name	LightSquared
foundation	July 20, 2010
location city	Reston, Virginia
location country	USA
key people	CEO Sanjiv Ahuja
products	Wholesale integrated 4G-LTE/satellite broadband mobile wireless
intl	}}

LightSquared is a company that plans to develop a wholesale 4G LTE (Long Term Evolution) wireless broadband communications network integrated with satellite coverage across the United States.

LightSquared History

LightSquared traces its roots back to 1988 and was known as American Mobile Satellite Corporation and later as Mobile Satellite Ventures after a merger between Motient Corporation and TMI Communications. It was most recently known as Skyterra, a company that provided comprehensive mobile satellite communications services. The company has operated in the North American market with two geostationary satellites since 1995. MSAT-2 is licensed in the United States and was launched in 1995. MSAT-1 is licensed in Canada and was launched in 1996.

LightSquared was granted the first license to deploy and provide terrestrial service in the L-Band spectrum in November 2004.

In 2011, LightSquared announced that it had signed a 15-year agreement to buy 4G from Sprint.

Integrated 4G-LTE-Satellite Network

LightSquared plans to provide network capacity on a wholesale-only basis to wireline and wireless communication service providers; cable operators; device manufacturers; web players; and content providers. LightSquared will sell its service to retailers and device makers, so that LTE wireless broadband service will be bundled into products. The integrated 4G-LTE-satellite network also will serve public sector projects including emergency preparedness and communications in times of crisis. The company announced in July 2010 that the network will be built by Nokia Siemens Networks. LightSquared expects to launch commercially in the second half of 2011 with four trial markets - Baltimore, Phoenix, Denver and Las Vegas.

The FCC sees LightSquared’s plan as a way of enhancing competition and speeding the deployment of mobile broadband in the United States. LightSquared will help smaller, regional wireless operators compete and provide nationwide 4G service to rural and underserved areas. It also provides new entrants in the wireless market a chance to come up with new business models that change how consumers access wireless broadband services.

On April 21, 2011, LightSquared and SI Wireless announced a partnership that will give SI Wireless customers throughout rural under-served markets access to LightSquared's 4G-LTE national broadband network and satellite coverage. The bilateral roaming agreement also delivers service to parts of rural Illinois, Kentucky and Tennessee.

On April 20, 2011, LightSquared entered into a bilateral roaming agreement with regional carrier Cellular South that will provide subscribers of Cellular South a nationwide 4G-LTE footprint, as well as satellite coverage in rural areas where there is no terrestrial network. The agreement is reciprocal in that it will also expand LightSquared's 4G-LTE coverage to additional rural communities.

On March 23, 2011, LightSquared CEO Sanjiv Ahuja announced that Best Buy had signed a retail distribution agreement with LightSquared to resell LightSquared's 4G LTE-satellite service under the current Best Buy Connect brand.

On March 22, 2011, LightSquared secured a deal with Leap Wireless, the parent of Cricket Communications phone service, that will allow Cricket to offer customers access LightSquared's 4G-LTE network.

On March 11, 2011, LightSquared announced a multi-year stategic network partnership with Open Range Communications, a broadband wireless provider of voice and data service to rural American communities.

On July 28, 2011, LightSquared and Sprint Nextel entered into a 15 year agreement to allow Sprint Nextel spectrum hosting, network service, and 4G LTE Wholesale. In return LightSquared will also utilize Sprint Nextel's current 3G network. The deal will also accelerate LTE Network build out.

Spectrum

LightSquared controls 59 MHz of United States spectrum (1525-1559 MHz) and received U.S. Federal Communications Commission (FCC) authorization in 2004 to use this L-Band spectrum to build its nationwide 4G-LTE wireless broadband network integrated with satellite coverage. On August 18, 2010, LightSquared announced it had delivered notice to Inmarsat triggering Phase 1 of a Cooperation Agreement between Inmarsat and LightSquared. This deal increases the amount of contiguous spectrum over North America available to both companies and should help accelerate the build-out of the LightSquared LTE network. LightSquared has an option to implement Phase 2 of the Cooperation Agreement which will add further capacity to its network. On January 28, 2011, LightSquared delivered notice to Inmarsat triggering Phase 2 of the Cooperation Agreement between Inmarsat and LightSquared in order to meet the accelerated demand for capacity for LightSquared’s 4G-LTE network.

Satellite launch

LightSquared’s SkyTerra 1 launched from the Baikonur Cosmodrome in Kazakhstan on November 14, 2010, “completing an important step on the way to providing combination satellite-terrestrial cell phone service in North America.” The satellite, one of the “largest commercial satellites ever built,” was launched aboard a Russian Proton-M/Briz-M rocket, weighs 5.4 tons, and carries the largest commercial reflector antenna ever put into space.

Request to the FCC

On March 1, 2001, LightSquared's predecessor, Mobile Satellite Ventures applied to the FCC to use a "highly innovative and spectrum-efficient combination of spot-beam satellites and terrestrial base stations to substantially improve coverage, capacity, and reliability of mobile communications without using any additional spectrum."

On January 26, 2011, The Federal Communications Commission granted LightSquared’s Request for Modification of its Authority for an Ancillary Terrestrial Component. The grant allowed LightSquared and its wholesale customers to offer terrestrial-only devices rather than having to incorporate both satellite and terrestrial services. "We find good cause to grant LightSquared a conditional waiver of Section 25.149(b)(4) of the Commission’s rules for services provided by LightSquared using its MSS (Mobile Satellite Services) L-band spectrum,” the FCC noted in its report.

Companies that provide global positioning systems, in addition to the United States Air Force, the operator of the GPS system, opposed the FCC waiver, saying that more time was needed to resolve concerns that LightSquared's service might interfere with their satellite-based offerings. LightSquared has promised to work with GPS providers and give the FCC monthly updates on a resolution to interference concerns. In June 2011, LightSquared unveiled a new plan for deploying its network which would use the lower frequency band of 1526-1536MHz (23MHz away from GPS) for the initial deployment and delay use of the upper band closer to GPS until a later date. They also proposed a 3dB reduction in the base station radiated power.

Network issues

In a January 12, 2011 letter to the FCC, National Telecommunications and Information Administration (NTIA) chief Lawrence Strickling said that LightSquared's hybrid mobile broadband services raise "significant interference concerns. Grant of the LightSquared waiver would create a new interference environment and it is incumbent on the FCC to deal with the resulting interference issues before any interference occurs. Several federal agencies with vital concerns about this spectrum band, including the Departments of Defense, Transportation and Homeland Security, have informed NTIA that they believe the FCC should defer action on the LightSquared waiver until these interference concerns are satisfactorily addressed."

On February 17, 2011 the Deputy Secretary of Defense Bill Lynn, along with the head of the USAF Space Command, Gen. William L. Shelton, expressed concerns about potential GPS interference from the LightSquared network.

On April 5, 2011, with respect to concerns raised by the U.S. GPS Industry Council and NTIA about LightSquared’s MSS/ATC operations, the FCC states that LightSquared cannot commence offering a commercial terrestrial service until the FCC concludes that the harmful interference concerns have been resolved. They also emphasize that responsibility for protecting services rests not only on new entrants but also on incumbent users themselves, who must use receivers that reasonably discriminate against reception of signals outside their allocated spectrum. In the case of GPS, the FCC notes that LightSquared’s operations have been anticipated for at least 8 years.

GPS receivers have relatively sensitive "front ends" because of the extremely weak signal strength, generally have little filtering to further reduce the signal loss, and are subject to interference from high power signals in the L band, something made worse when an active antenna system containing a LNA is added to the system. When MSS/ATC (Mobile Satellite Service/Ancillary Terrestrial Component) operation was first proposed, the number of ATC transmitters was thought to be small, because it was part of an integrated system with the satellite.

LightSquared has been coordinating with the other L-Band MSS providers in order to expand its spectrum, and now controls a nearly contiguous 20 MHz section through deals with other MSS providers, coordination with multiple international agencies, and the US FCC International Bureau.

The initial modification order to allow terrestrial-only devices onto LightSquared's network was filed on November 19, 2010, with comments due on December 2, 2010, and reply comments due on December 9, 2010. This time frame has the US Thanksgiving holiday squarely in the middle of it, and allowed little official time for correspondence (six business days between filing and comments due, five business days between comments due and reply comments due). Several corporations and industry organizations feel that this is a major modification to LightSquared's MSS/ATC license, and wanted a 30-day comment period. An FCC spokesman said, "The FCC waiver approval granted to LightSquared was based on the merits of its proposal, following a process that included ample opportunity for comment."

With the possibility of tens of thousands of base stations that transmit in the satellite-to-earth part of the L-band MSS spectrum closest to the GPS spectrum, the high power signals (typically 70 dBm) will interfere with far weaker GPS signals from space (typically −150 to −130 dBm at ground level). The GPS receivers specs never intended to deal with this situation, so they will have problems. However, FCC Chairman Julius Genachowski stated on May 31, 2011 that "it should be no surprise to anyone involved in the LightSquared matter that the company was planning for some time to deploy a major terrestrial network in the spectrum adjacent to GPS," and that "all interested parties had ample time to comment in advance of these orders (granting the request to increase the power level of the base stations to the exact level the GPS industry is now criticizing). Indeed, the Harbinger/Skyterra license-transfer proceeding was pending at the Commission for nearly a year."

Since 2002, LightSquared has worked with the NTIA and the GPS industry to avoid interference between LightSquared’s network and GPS. LightSquared has agreed to operate its services within strict technical requirements. LightSquared’s predecessor agreed with GPS industry representatives to protect GPS with more stringent out‐of‐band‐emission limits than those required by the FCC’s rules. Beginning in 2009, LightSquared has sponsored tests with both GPS navigation‐only devices and GPS‐capable phones. So far, such tests have shown very limited adverse impact on GPS as almost all receivers were resilient to predicted interference from LightSquared’s operations. This is in complete contrast to the results of testing conducted by Garmin International which found that widespread, severe GPS jamming would occur. In addition, the FCC has initiated a process that hopes to ensure LightSquared’s service will not interfere with GPS. In order to resolve GPS interference concerns the FCC has established a working group composed of NTIA, other Federal agencies, the GPS community, and LightSquared to fully examine the potential for interference. LightSquared has agreed that this process must be completed to the FCC’s satisfaction before the company will offer commercial service.

At the level of GPS devices used for timing at CMRS base stations, throughout 2010, LightSquared successfully worked with the manufacturers of timing devices to design and implement a filter that eliminates interference for those CMRS base stations using GPS for timing.

In a January 6, 2011 letter from LightSquared to NTIA chief Lawrence Strickling, “LightSquared agreed to organize and lead an industry group major participants in the telecom and GPS industries, including chipset and device manufacturers, service providers, academic experts, user groups and others – including the FCC and NTIA officials. This group will examine the issue of interference to GPS devices and will consider both short-term and long-term technical solutions to the issue.”

References

Further reading

LightSquared: The answer to U.S. wireless competition? - CNET

NSN Lands $7B LTE Deal in US - Light Reading

LightSquared to Cover U.S. with LTE & Satellite Network - Phone Scoop

LightSquared: $7 billion LTE network built by Nokia Siemens Networks, launching end of next year - Into Mobile

Huge: Hybrid satellite-LTE network launches under name Lightsquared – Betanews

Harbinger forges $7B LTE pact with Nokia Siemens – FierceWireless

FCC grants LightSquared approval to use satellite airwaves for cell phones - Washington Post

- US National Executive Committee for Space-Based PNT

- GPS World

Susceptibility of GPS devices to interference - CNNMoney

External links

LightSquared

Lightsquared Backgrounder

NTIA FCC LightSquared Interference

Lightsquared LTE Interference

FCC Requested to Authorize a Terrestrial Service...

Data Shows Disastrous GPS Jamming from FCC-Approved Broadcaster

Trimble testifies at United States House of Representatives subcommittee on interference against LightSquared

Inmarsat's Chief Doubts Severity of LightSquared-GPS Interference Issue

Coalition to Save Our GPS, an advocacy group opposed to increased use of the spectrum near the GPS frequencies

Wireless Modeling of LightSquared & GPS spectrumWireless modeling of LightSquared & GPS Spectrum near San Francisco Bay Area.]

Category:Wireless networking Category:Internet access

name	Andrew Paolo Napolitano
office	Judge of theNew Jersey Superior Court
term start	1987
term end	1995
appointed	Thomas Kean
birth date	June 06, 1950
birth place	Newark, New Jersey, United States
alma mater	Princeton UniversityNotre Dame Law School
occupation	JudgeAttorneyMedia Personality
religion	Roman Catholic
website	Biography on FoxNews.com }}

Andrew Paolo Napolitano (born June 6, 1950 in Newark, New Jersey) is a former New Jersey Superior Court Judge and now a political and legal analyst for Fox News Channel. Napolitano started on the channel in 1998, and currently serves as the network's senior judicial analyst, commenting on legal news and trials.

Judicial and academic career

He is a graduate of Princeton University (where he was a founding member of the Concerned Alumni of Princeton) and Notre Dame Law School.

Napolitano sat on the New Jersey bench from 1987 to 1995, becoming the state's youngest then-sitting Superior Court judge. He also served as an adjunct professor at Seton Hall University School of Law for 11 years. Napolitano resigned his judgeship in 1995 to pursue his writing and television career.

Media career

Prior to joining Fox as a news analyst, Napolitano was the presiding judge on the television show, ''Power of Attorney'', in which people brought small-claims disputes to a televised courtroom. Differing from similar formats, the plaintiffs and defendants were represented, "pro bono," by famous attorneys. The show ran in syndication during the 2000–2001 season.

From 2006 to 2010, Napolitano co-hosted a talk radio show on Fox News Radio with Brian Kilmeade titled ''Brian and the Judge''.

Napolitano hosts a libertarian talk show called ''Freedom Watch'' that airs daily, with new episodes on weekdays, on Fox Business. Frequent guests on ''Freedom Watch'' are Congressman Ron Paul, economist Peter Schiff, and Lew Rockwell. Napolitano has called himself the "Ayn Rand of Fox News" and has also promoted the works of Friedrich Hayek, Milton Friedman and Ludwig von Mises on his program. The show originally aired once a week on Wednesdays at 2:00 pm on Fox News' ''Strategy Room''. On September 14, 2009 it became a show that airs three to four times a week. On June 12, 2010 it debuted as a weekly show on Fox Business.

Napolitano regularly substitutes for television host Glenn Beck when Beck is absent from his program. After Beck announced he would be leaving Fox News, he asked Napolitano to replace him.

Writing career

In 2004, Napolitano wrote the book, ''Constitutional Chaos: What Happens When the Government Breaks its Own Laws'', a criticism of the American justice system. In the National Review, former federal prosecutor Andrew McCarthy noted that Napolitano had been a mid-level state judge and questioned Napolitano's knowledge of the federal Constitution, citing what McCarthy asserted were numerous errors in Napolitano's writing on the subject.

In 2006, his second book, ''The Constitution in Exile: How the Federal Government Has Seized Power by Rewriting the Supreme Law of the Land'' was published.

A third book, ''A Nation of Sheep'', was released in October 2007.

In April 2009, Napolitano's fourth book, ''Dred Scott's Revenge: A Legal History of Race and Freedom in America'', was released.

In March, 2010, Napolitano's fifth book was released: ''Lies the Government Told You: Myth, Power, and Deception in American History''.

According to Napolitano's radio show, he is currently working on a sixth book which will be about President Barack Obama and the current state of America.

Politics

Napolitano is a pro-life libertarian also known as libertarian conservatism.

Napolitano has called consumer advocate and frequent presidential candidate Ralph Nader a hero of his.

Professor Murray Sabrin and political commentator Lew Rockwell mentioned Napolitano as a possible vice presidential running mate for Republican Ron Paul during the 2008 presidential election.

Personal

Napolitano splits his time living in Manhattan and Sussex County, New Jersey where he owns a farm that produces maple syrup.

Napolitano is not related to U.S. Secretary of Homeland Security Janet Napolitano, who he sometimes jokingly calls "Cousin Janet."

References

External links

Freedom Watch With the Judge

Judge Andrew P. Napolitano website

Brian and The Judge

Judge Andew P. Napolitano's bio at foxnews.com

Draft Judge Andrew P. Napolitano website

The Judge's Farm - Vine Hill

Category:American judges Category:American legal writers Category:American libertarians Category:American Christians Category:American political writers Category:American television personalities Category:American talk radio hosts Category:Glenn Beck Category:Princeton University alumni Category:Notre Dame Law School alumni Category:American people of Italian descent Category:New Jersey state court judges Category:People from Newark, New Jersey Category:People from Sussex County, New Jersey Category:Seton Hall University School of Law faculty Category:1950 births Category:Living people Category:Fox News Channel people

de:Andrew Napolitano pt:Andrew Napolitano

Sanjiv Ahuja is currently Chairman and CEO of LightSquared a company that is developing a wholesale-only nationwide 4G LTE Long Term Evolution wireless broadband communications network integrated with satellite coverage. The company is the result of Harbinger Capital Partners acquisition in March, 2010 of satellite operator SkyTerra Communications. Sanjiv partnered with Harbinger Capital Partners Chief Executive Officer Philip A. Falcone in creating LightSquared.

Sanjiv is also founder, Chairman and Chief Executive Officer of Augere, a company formed in 2007 with a vision to provide broadband access for all. Augere is currently providing wireless broadband internet services in Bangladesh and Pakistan under the brand name Qubee. As well, Sanjiv is the founder and Chairman of Eaton Telecom, which is building passive telecom infrastructure throughout Africa.

Prior to founding Augere, Sanjiv was the Chief Executive Officer of Orange S.A for three years from March 2004 - April 2007. Prior to that he was the company's Chief Operating Officer from April 2003 to March 2004. After stepping down as CEO of Orange S.A, Sanjiv was Chairman of Orange UK until September 2008.

During his leadership, Orange increased the number of countries in which it operated from 17 to 23, including 14 countries in Africa, and more than doubled its mobile customers from 48 million to over 100 million worldwide. Orange S.A also saw a significant and continuous improvement in revenue, market share and cash flow under his leadership. Sanjiv oversaw the successful extension of the Orange brand from mobile origins to embrace France Telecom's broadband, fixed line and IPTV services in its largest markets.

Sanjiv's previous industry experience includes President of Telcordia Technologies (formerly Bellcore), the world's largest provider of operations support systems, network software and consulting and engineering services to the telecommunications industry. Prior to that, he spent fifteen years at IBM in various executive roles. His last area of responsibility included leading IBM's entry into the telecommunications software industry.

Sanjiv has a degree in electrical engineering from Delhi University, India, and a masters degree from Columbia University in New York. He is currently a non-executive director of Telenor S.A.

Category:1956 births Category:Columbia University alumni Category:Columbia Engineering alumni Category:Living people

fr:Sanjiv Ahuja

name	Myocardial infarction
disasesdb	8664
icd10	-
icd9
medlineplus	000195
emedicinesubj	med
emedicinetopic	1567
emedicine mult
meshid	D009203 }}

Myocardial infarction (MI) or acute myocardial infarction (AMI), commonly known as a heart attack, is the interruption of blood supply to a part of the heart, causing heart cells to die. This is most commonly due to occlusion (blockage) of a coronary artery following the rupture of a vulnerable atherosclerotic plaque, which is an unstable collection of lipids (fatty acids) and white blood cells (especially macrophages) in the wall of an artery. The resulting ischemia (restriction in blood supply) and oxygen shortage, if left untreated for a sufficient period of time, can cause damage or death (''infarction'') of heart muscle tissue (''myocardium'').

Classical symptoms of acute myocardial infarction include sudden chest pain (typically radiating to the left arm or left side of the neck), shortness of breath, nausea, vomiting, palpitations, sweating, and anxiety (often described as a sense of impending doom). Women may experience fewer typical symptoms than men, most commonly shortness of breath, weakness, a feeling of indigestion, and fatigue. Approximately one quarter of all myocardial infarctions are "silent", without chest pain or other symptoms.

Among the diagnostic tests available to detect heart muscle damage are an electrocardiogram (ECG), echocardiography, and various blood tests. The most often used markers are the creatine kinase-MB (CK-MB) fraction and the troponin levels. Immediate treatment for suspected acute myocardial infarction includes oxygen, aspirin, and sublingual nitroglycerin.

Most cases of STEMI (ST elevation MI) are treated with thrombolysis or percutaneous coronary intervention (PCI). NSTEMI (non-ST elevation MI) should be managed with medication, although PCI is often performed during hospital admission. In people who have multiple blockages and who are relatively stable, or in a few emergency cases, bypass surgery may be an option.

Heart attacks are the leading cause of death for both men and women worldwide. Important risk factors are previous cardiovascular disease, older age, tobacco smoking, high blood levels of certain lipids (triglycerides, low-density lipoprotein) and low levels of high density lipoprotein (HDL), diabetes, high blood pressure, obesity, chronic kidney disease, heart failure, excessive alcohol consumption, the abuse of certain drugs (such as cocaine and methamphetamine), and chronic high stress levels.

Classification

There are two basic types of acute myocardial infarction: Transmural: associated with atherosclerosis involving major coronary artery. It can be subclassified into anterior, posterior, or inferior. Transmural infarcts extend through the whole thickness of the heart muscle and are usually a result of complete occlusion of the area's blood supply. Subendocardial: involving a small area in the subendocardial wall of the left ventricle, ventricular septum, or papillary muscles. Subendocardial infarcts are thought to be a result of locally decreased blood supply, possibly from a narrowing of the coronary arteries. The subendocardial area is farthest from the heart's blood supply and is more susceptible to this type of pathology.

Clinically, a myocardial infarction can be further subclassified into a ST elevation MI (STEMI) versus a non-ST elevation MI (non-STEMI) based on ECG changes.

The phrase "heart attack" is sometimes used incorrectly to describe sudden cardiac death, which may or may not be the result of acute myocardial infarction. A heart attack is different from, but can be the cause of cardiac arrest, which is the stopping of the heartbeat, and cardiac arrhythmia, an abnormal heartbeat. It is also distinct from heart failure, in which the pumping action of the heart is impaired; severe myocardial infarction may lead to heart failure, but not necessarily.

A 2007 consensus document classifies myocardial infarction into five main types:

Type 1 – Spontaneous myocardial infarction related to ischaemia due to a primary coronary event such as plaque erosion and/or rupture, fissuring, or dissection

Type 2 – Myocardial infarction secondary to ischaemia due to either increased oxygen demand or decreased supply, e.g. coronary artery spasm, coronary embolism, anaemia, arrhythmias, hypertension, or hypotension

Type 3 – Sudden unexpected cardiac death, including cardiac arrest, often with symptoms suggestive of myocardial ischaemia, accompanied by presumably new ST elevation, or new LBBB, or evidence of fresh thrombus in a coronary artery by angiography and/or at autopsy, but death occurring before blood samples could be obtained, or at a time before the appearance of cardiac biomarkers in the blood

Type 4 – Associated with coronary angioplasty or stents:

* Type 4a – Myocardial infarction associated with PCI

* Type 4b – Myocardial infarction associated with stent thrombosis as documented by angiography or at autopsy

Type 5 – Myocardial infarction associated with CABG

Signs and symptoms

The onset of symptoms in myocardial infarction (MI) is usually gradual, over several minutes, and rarely instantaneous. Chest pain is the most common symptom of acute myocardial infarction and is often described as a sensation of tightness, pressure, or squeezing. Chest pain due to ischemia (a lack of blood and hence oxygen supply) of the heart muscle is termed angina pectoris. Pain radiates most often to the left arm, but may also radiate to the lower jaw, neck, right arm, back, and epigastrium, where it may mimic heartburn. Levine's sign, in which the patient localizes the chest pain by clenching their fist over the sternum, has classically been thought to be predictive of cardiac chest pain, although a prospective observational study showed that it had a poor positive predictive value.

Shortness of breath (dyspnea) occurs when the damage to the heart limits the output of the left ventricle, causing left ventricular failure and consequent pulmonary edema. Other symptoms include diaphoresis (an excessive form of sweating), weakness, light-headedness, nausea, vomiting, and palpitations. These symptoms are likely induced by a massive surge of catecholamines from the sympathetic nervous system which occurs in response to pain and the hemodynamic abnormalities that result from cardiac dysfunction. Loss of consciousness (due to inadequate cerebral perfusion and cardiogenic shock) and sudden death (frequently due to the development of ventricular fibrillation) can occur in myocardial infarctions.

Women and older patients report atypical symptoms more frequently than their male and younger counterparts. Women also report more numerous symptoms compared with men (2.6 on average vs 1.8 symptoms in men). The most common symptoms of MI in women include dyspnea (shortness of breath), weakness, and fatigue. Fatigue, sleep disturbances, and dyspnea have been reported as frequently occurring symptoms which may manifest as long as one month before the actual clinically manifested ischemic event. In women, chest pain may be less predictive of coronary ischemia than in men.

Approximately one fourth of all myocardial infarctions are silent, without chest pain or other symptoms. These cases can be discovered later on electrocardiograms, using blood enzyme tests or at autopsy without a prior history of related complaints. A silent course is more common in the elderly, in patients with diabetes mellitus and after heart transplantation, probably because the donor heart is not fully innervated by the nervous system of the recipient. In diabetics, differences in pain threshold, autonomic neuropathy, and psychological factors have been cited as possible explanations for the lack of symptoms.

Any group of symptoms compatible with a sudden interruption of the blood flow to the heart are called an acute coronary syndrome.

The differential diagnosis includes other catastrophic causes of chest pain, such as pulmonary embolism, aortic dissection, pericardial effusion causing cardiac tamponade, tension pneumothorax, and esophageal rupture. Other non-catastrophic differentials include gastroesophageal reflux and Tietze's syndrome.

Causes

Heart attack rates are higher in association with intense exertion, be it psychological stress or physical exertion, especially if the exertion is more intense than the individual usually performs. Quantitatively, the period of intense exercise and subsequent recovery is associated with about a 6-fold higher myocardial infarction rate (compared with other more relaxed time frames) for people who are physically very fit. For those in poor physical condition, the rate differential is over 35-fold higher. One observed mechanism for this phenomenon is the increased arterial pulse pressure stretching and relaxation of arteries with each heart beat which, as has been observed with intravascular ultrasound, increases mechanical "shear stress" on atheromas and the likelihood of plaque rupture.

Acute severe infection, such as pneumonia, can trigger myocardial infarction. A more controversial link is that between ''Chlamydophila pneumoniae'' infection and atherosclerosis. While this intracellular organism has been demonstrated in atherosclerotic plaques, evidence is inconclusive as to whether it can be considered a causative factor. Treatment with antibiotics in patients with proven atherosclerosis has not demonstrated a decreased risk of heart attacks or other coronary vascular diseases.

There is an association of an increased incidence of a heart attack in the morning hours, more specifically around 9 a.m. Some investigators have noticed that the ability of platelets to aggregate varies according to a circadian rhythm, although they have not proven causation.

Risk factors

Risk factors for atherosclerosis are generally risk factors for myocardial infarction:

Diabetes (with or without insulin resistance) – the single most important risk factor for ischaemic heart disease (IHD)

Tobacco smoking

Hypercholesterolemia (more accurately hyperlipoproteinemia, especially high low density lipoprotein and low high density lipoprotein)

Low HDL

High Triglycerides

High blood pressure

Family history of ischaemic heart disease (IHD)

Obesity (defined by a body mass index of more than 30 kg/m², or alternatively by waist circumference or waist-hip ratio).

Age — Men acquire an independent risk factor at age 45, Women acquire an independent risk factor at age 55; in addition individuals acquire another independent risk factor if they have a first-degree male relative (brother, father) who suffered a coronary vascular event at or before age 55. Another independent risk factor is acquired if one has a first-degree female relative (mother, sister) who suffered a coronary vascular event at age 65 or younger.

Hyperhomocysteinemia (high homocysteine, a toxic blood amino acid that is elevated when intakes of vitamins B₂, B₆, B₁₂ and folic acid are insufficient)

Stress — Occupations with high stress index are known to have susceptibility for atherosclerosis

Alcohol — Studies show that prolonged exposure to high quantities of alcohol can increase the risk of heart attack

Males are more at risk than females.

Many of these risk factors are modifiable, so many heart attacks can be prevented by maintaining a healthier lifestyle. Physical activity, for example, is associated with a lower risk profile. Non-modifiable risk factors include age, sex, and family history of an early heart attack (before the age of 60), which is thought of as reflecting a genetic predisposition.

Socioeconomic factors such as a shorter education and lower income (particularly in women), and unmarried cohabitation may also contribute to the risk of MI. To understand epidemiological study results, it's important to note that many factors associated with MI mediate their risk via other factors. For example, the effect of education is partially based on its effect on income and marital status.

Women who use combined oral contraceptive pills have a modestly increased risk of myocardial infarction, especially in the presence of other risk factors, such as smoking.

Inflammation is known to be an important step in the process of atherosclerotic plaque formation. C-reactive protein (CRP) is a sensitive but non-specific marker for inflammation. Elevated CRP blood levels, especially measured with high sensitivity assays, can predict the risk of MI, as well as stroke and development of diabetes. Moreover, some drugs for MI might also reduce CRP levels. The use of high sensitivity CRP assays as a means of screening the general population is advised against, but it may be used optionally at the physician's discretion, in patients who already present with other risk factors or known coronary artery disease. Whether CRP plays a direct role in atherosclerosis remains uncertain.

Inflammation in periodontal disease may be linked to coronary heart disease, and since periodontitis is very common, this could have great consequences for public health. Serological studies measuring antibody levels against typical periodontitis-causing bacteria found that such antibodies were more present in subjects with coronary heart disease. Periodontitis tends to increase blood levels of CRP, fibrinogen and cytokines; thus, periodontitis may mediate its effect on MI risk via other risk factors. Preclinical research suggests that periodontal bacteria can promote aggregation of platelets and promote the formation of foam cells. A role for specific periodontal bacteria has been suggested but remains to be established. There is some evidence that influenza may trigger an acute myocardial infarction.

Baldness, hair greying, a diagonal earlobe crease (Frank's sign) and possibly other skin features have been suggested as independent risk factors for MI. Their role remains controversial; a common denominator of these signs and the risk of MI is supposed, possibly genetic.

Calcium deposition is another part of atherosclerotic plaque formation. Calcium deposits in the coronary arteries can be detected with CT scans. Several studies have shown that coronary calcium can provide predictive information beyond that of classical risk factors.

The European Society of Cardiology and the European Association for Cardiovascular Prevention and Rehabilitation have developed an interactive tool for prediction and managing the risk of heart attack and stroke in Europe. HeartScore is aimed at supporting clinicians in optimising individual cardiovascular risk reduction. The Heartscore Programme is available in 12 languages and offers web based or PC version.

Pathophysiology

Acute myocardial infarction refers to two subtypes of acute coronary syndrome, namely non-ST-elevated myocardial infarction and ST-elevated myocardial infarction, which are most frequently (but not always) a manifestation of coronary artery disease. The most common triggering event is the disruption of an atherosclerotic plaque in an epicardial coronary artery, which leads to a clotting cascade, sometimes resulting in total occlusion of the artery. Atherosclerosis is the gradual buildup of cholesterol and fibrous tissue in plaques in the wall of arteries (in this case, the coronary arteries), typically over decades. Blood stream column irregularities visible on angiography reflect artery lumen narrowing as a result of decades of advancing atherosclerosis. Plaques can become unstable, rupture, and additionally promote a thrombus (blood clot) that occludes the artery; this can occur in minutes. When a severe enough plaque rupture occurs in the coronary vasculature, it leads to myocardial infarction (necrosis of downstream myocardium).

If impaired blood flow to the heart lasts long enough, it triggers a process called the ischemic cascade; the heart cells in the territory of the occluded coronary artery die (chiefly through necrosis) and do not grow back. A collagen scar forms in its place. Recent studies indicate that another form of cell death called apoptosis also plays a role in the process of tissue damage subsequent to myocardial infarction. As a result, the patient's heart will be permanently damaged. This myocardial scarring also puts the patient at risk for potentially life threatening arrhythmias, and may result in the formation of a ventricular aneurysm that can rupture with catastrophic consequences.

Injured heart tissue conducts electrical impulses more slowly than normal heart tissue. The difference in conduction velocity between injured and uninjured tissue can trigger re-entry or a feedback loop that is believed to be the cause of many lethal arrhythmias. The most serious of these arrhythmias is ventricular fibrillation (''V-Fib''/VF), an extremely fast and chaotic heart rhythm that is the leading cause of sudden cardiac death. Another life threatening arrhythmia is ventricular tachycardia (''V-Tach''/VT), which may or may not cause sudden cardiac death. However, ventricular tachycardia usually results in rapid heart rates that prevent the heart from pumping blood effectively. Cardiac output and blood pressure may fall to dangerous levels, which can lead to further coronary ischemia and extension of the infarct.

The cardiac defibrillator is a device that was specifically designed to terminate these potentially fatal arrhythmias. The device works by delivering an electrical shock to the patient in order to depolarize a critical mass of the heart muscle, in effect "rebooting" the heart. This therapy is time dependent, and the odds of successful defibrillation decline rapidly after the onset of cardiopulmonary arrest.

Diagnosis

The diagnosis of myocardial infarction can be made after assessing patient's complaints and physical status. ECG changes, coronary angiogram and levels of cardiac markers help to confirm the diagnosis. ECG gives valuable clues to identify the site of myocardial damage while coronary angiogram allows visualization of narrowing or obstructions in the heart vessels. At autopsy, a pathologist can diagnose a myocardial infarction based on anatomopathological findings.

A chest radiograph and routine blood tests may indicate complications or precipitating causes and are often performed upon arrival to an emergency department. New regional wall motion abnormalities on an echocardiogram are also suggestive of a myocardial infarction. Echo may be performed in equivocal cases by the on-call cardiologist. In stable patients whose symptoms have resolved by the time of evaluation, Technetium (99mTc) sestamibi (i.e. a "MIBI scan") or thallium-201 chloride can be used in nuclear medicine to visualize areas of reduced blood flow in conjunction with physiologic or pharmocologic stress. Thallium may also be used to determine viability of tissue, distinguishing whether non-functional myocardium is actually dead or merely in a state of hibernation or of being stunned.

WHO criteria formulated in 1979 have classically been used to diagnose MI; a patient is diagnosed with myocardial infarction if two (probable) or three (definite) of the following criteria are satisfied: # Clinical history of ischaemic type chest pain lasting for more than 20 minutes # Changes in serial ECG tracings # Rise and fall of serum cardiac biomarkers such as creatine kinase-MB fraction and troponin

The WHO criteria were refined in 2000 to give more prominence to cardiac biomarkers. According to the new guidelines, a cardiac troponin rise accompanied by either typical symptoms, pathological Q waves, ST elevation or depression or coronary intervention are diagnostic of MI.

Prevention

The risk of a recurrent myocardial infarction decreases with strict blood pressure management and lifestyle changes, chiefly smoking cessation, regular exercise, a sensible diet for those with heart disease, and limitation of alcohol intake. People are usually commenced on several long-term medications post-MI, with the aim of preventing secondary cardiovascular events such as further myocardial infarctions, congestive heart failure or cerebrovascular accident (CVA). Unless contraindicated, such medications may include:

Antiplatelet drug therapy such as aspirin and/or clopidogrel should be continued to reduce the risk of plaque rupture and recurrent myocardial infarction. Aspirin is first-line, owing to its low cost and comparable efficacy, with clopidogrel reserved for patients intolerant of aspirin. The combination of clopidogrel and aspirin may further reduce risk of cardiovascular events, however the risk of hemorrhage is increased. Beta blocker therapy such as metoprolol or carvedilol should be commenced. These have been particularly beneficial in high-risk patients such as those with left ventricular dysfunction and/or continuing cardiac ischaemia. β-Blockers decrease mortality and morbidity. They also improve symptoms of cardiac ischemia in NSTEMI. ACE inhibitor therapy should be commenced 24–48 hours post-MI in hemodynamically-stable patients, particularly in patients with a history of MI, diabetes mellitus, hypertension, anterior location of infarct (as assessed by ECG), and/or evidence of left ventricular dysfunction. ACE inhibitors reduce mortality, the development of heart failure, and decrease ventricular remodelling post-MI. Statin therapy has been shown to reduce mortality and morbidity post-MI. The effects of statins may be more than their LDL lowering effects. The general consensus is that statins have plaque stabilization and multiple other ("pleiotropic") effects that may prevent myocardial infarction in addition to their effects on blood lipids. The aldosterone antagonist agent eplerenone has been shown to further reduce risk of cardiovascular death post-MI in patients with heart failure and left ventricular dysfunction, when used in conjunction with standard therapies above. Spironolactone is another option that is sometimes preferable to eplerenone due to cost. Evidence supports the consumption of polyunsaturated fats instead of saturated fats as a measure of decreasing coronary heart disease. Omega-3 fatty acids, commonly found in fish, have been shown to reduce mortality post-MI. While the mechanism by which these fatty acids decrease mortality is unknown, it has been postulated that the survival benefit is due to electrical stabilization and the prevention of ventricular fibrillation. However, further studies in a high-risk subset have not shown a clear-cut decrease in potentially fatal arrhythmias due to omega-3 fatty acids.

Blood donation may reduce the risk of heart disease for men, but the link has not been firmly established.

A Cochrane review found that giving heparin to people who have heart conditions like unstable angina and some forms of heart attacks reduces the risk of having another heart attack. However, heparin also increases the chance of suffering from minor bleeding.

Management

An MI is a medical emergency which requires immediate medical attention. Treatment attempts to salvage as much myocardium as possible and to prevent further complications, thus the phrase "time is muscle". Oxygen, aspirin, and nitroglycerin may be administered. Morphine was classically used if nitroglycerin was not effective; however, it may increase mortality in the setting of NSTEMI. A 2009 and 2010 review of high flow oxygen in myocardial infarction found increased mortality and infarct size, calling into question the recommendation about its routine use. Other analgesics such as nitrous oxide are of unknown benefit. Percutaneous coronary intervention (PCI) or fibrinolysis are recommended in those with an STEMI.

Prognosis

The prognosis post myocardial infarction varies greatly, depending on a person's health, the extent of the heart damage and the treatment given. For the period 2005–2008 in the United States the median mortality at 30 days was 16.6% with a range from 10.9% to 24.9% depending on the hospital. Using variables available in the emergency room, people with a higher risk of adverse outcome can be identified. One study found that 0.4% of patients with a low risk profile died after 90 days, whereas in high risk people it was 21.1%.

Some of the more reproduced risk stratifying factors include: age, hemodynamic parameters (such as heart failure, cardiac arrest on admission, systolic blood pressure, or Killip class of two or greater), ST-segment deviation, diabetes, serum creatinine, peripheral vascular disease and elevation of cardiac markers. Assessment of left ventricular ejection fraction may increase the predictive power. The prognostic importance of Q-waves is debated. Prognosis is significantly worsened if a mechanical complication such as papillary muscle or myocardial free wall rupture occur. Morbidity and mortality from myocardial infarction has improved over the years due to better treatment.

Complications

Complications may occur immediately following the heart attack (in the acute phase), or may need time to develop (a chronicproblem). Acute complications may include heart failure if the damaged heart is no longer able to adequately pump blood around the body; aneurysm or rupture of the myocardium; mitral regurgitation, particularly if the infarction causes dysfunction of the papillary muscle; and arrhythmias, such as ventricular fibrillation, ventricular tachycardia, atrial fibrillation and heart block. Longer-term complications include heart failure, atrial fibrillation, and the increased risk of a second myocardial infarction.

Epidemiology

Myocardial infarction is a common presentation of ischemic heart disease. The WHO estimated in 2002, that 12.6 percent of worldwide deaths were from ischemic heart disease with it the leading cause of death in developed countries, and third to AIDS and lower respiratory infections in developing countries. Worldwide more than 3 million people have STEMIs and 4 million have NSTEMIs a year.

Coronary heart disease is responsible for 1 in 5 deaths in the United States. It is becoming more common in the developing world such that in India, cardiovascular disease (CVD) is the leading cause of death. The deaths due to CVD in India were 32% of all deaths in 2007 and are expected to rise from 1.17 million in 1990 and 1.59 million in 2000 to 2.03 million in 2010. Although a relatively new epidemic in India, it has quickly become a major health issue with deaths due to CVD expected to double during 1985–2015. Mortality estimates due to CVD vary widely by state, ranging from 10% in Meghalaya to 49% in Punjab (percentage of all deaths). Punjab (49%), Goa (42%), Tamil Nadu (36%) and Andhra Pradesh (31%) have the highest CVD related mortality estimates. State-wise differences are correlated with prevalence of specific dietary risk factors in the states. Moderate physical exercise is associated with reduced incidence of CVD in India (those who exercise have less than half the risk of those who don't).

Legal implications

At common law, a myocardial infarction is generally a disease, but may sometimes be an injury. This has implications for no-fault insurance schemes such as workers' compensation. A heart attack is generally not covered; however, it may be a work-related injury if it results, for example, from unusual emotional stress or unusual exertion. Additionally, in some jurisdictions, heart attacks suffered by persons in particular occupations such as police officers may be classified as line-of-duty injuries by statute or policy. In some countries or states, a person who has suffered from a myocardial infarction may be prevented from participating in activity that puts other people's lives at risk, for example driving a car or flying an airplane.

Research

Patients who receive stem cell treatment by coronary artery injections of stem cells derived from their own bone marrow after a myocardial infarction (MI) show improvements in left ventricular ejection fraction and end-diastolic volume not seen with placebo. The larger the initial infarct size, the greater the effect of the infusion. Clinical trials of progenitor cell infusion as a treatment approach to ST elevation MI are proceeding.

There are currently 3 biomaterial and tissue engineering approaches for the treatment of MI, but these are in an even earlier stage of medical research, so many questions and issues need to be addressed before they can be applied to patients. The first involves polymeric left ventricular restraints in the prevention of heart failure. The second utilizes ''in vitro'' engineered cardiac tissue, which is subsequently implanted ''in vivo''. The final approach entails injecting cells and/or a scaffold into the myocardium to create ''in situ'' engineered cardiac tissue.

References

External links

American Heart Association's Heart Attack web site – Information and resources for preventing, recognizing and treating heart attack.

Heart Attack – overview of resources from MedlinePlus

Category:Aging-associated diseases Category:Causes of death Category:Ischemic heart diseases Category:Medical emergencies

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