heart attack
 


Heart Attack


Almost all heart attacks occur when a blood clot suddenly and completely blocks a coronary artery.

This condition is called a coronary thrombosis, or simply a coronary. The part of the heart muscle nourished by the blocked artery becomes damaged by lack of oxygen.

Unless blood flow returns within minutes, muscle damage increases. Heart cells begin to die after four to six hours without blood. The damage can affect the heart's ability to pump and may cause the patient's death. If the clot can be dissolved within four to six hours, damage to the heart can be reduced. Symptoms. Some people have no warning signs at the beginning of a heart attack. But many people experience angina, dizziness, indigestion, or other symptoms. Most heart attacks cause severe pain. Patients describe the pain as a dull, crushing ache in the chest, but discomfort may extend into the neck, jaw, arms, or back.

The pain may last from a few minutes to several hours. Anyone with chest pain who suspects the pain may be due to a heart attack should seek medical help immediately.

Some patients may stop breathing, and their hearts may stop beating. A first-aid technique called cardiopulmonary resuscitation (CPR) can maintain breathing and circulation until a patient can be taken to a hospital. But CPR should be performed only by someone trained in the technique.

Diagnosis and treatment.

Injured heart muscle causes abnormal ECG waves. Soon after a patient reaches the hospital, doctors administer an ECG to determine that symptoms result from a heart attack and not some other disorder. Doctors also use certain blood tests to detect a heart attack. But these tests are not useful until a few hours after an attack. Doctors may administer a strong painkilling drug, such as morphine, to relieve the pain of a heart attack. They also use drugs to dissolve clots in the blocked artery or may perform emergency angioplasty or bypass surgery.

After doctors stabilize the condition of a heart attack patient, they admit the person to the hospital and monitor him or her for complications in the intensive care unit. Some hospitals have a specialized intensive care unit called a coronary care unit for heart patients. Two major complications are heart failure and arrhythmia. Heart failure occurs if the heart cannot pump enough blood because of extensive damage to the heart muscle. In most cases, heart failure can be successfully treated. In arrhythmia, the heart's electrical system produces an abnormal pattern of beats. Most arrhythmias can be readily treated, but a type called ventricular fibrillation can cause sudden death. Ventricular fibrillation occurs when electrical signals in the ventricles fire randomly.

More than 20 percent of heart attack patients who do not get medical care die. Some people die before they can reach a doctor, but other patients ignore their symptoms and delay treatment. The death rate among hospitalized patients ranges from 5 to 10 percent. Heart attack patients with ongoing chest pain, arrhythmias, or heart failure have a greater risk of another attack than do patients without these problems.

Source : World Book 2005


 




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Supersaturated oxygen (SSO2) administered during catheter-based treatments for heart attack can significantly reduce heart muscle damage, according to a new study reported in Circulation: Cardiovascular Interventions, a journal of the American Heart Association.

In another study from the same issue, a different group of researchers found that manually removing a blood clot provided greater recovery of heart function after a heart attack.

"The greatest benefits were seen in the patients most at risk," said Gregg W. Stone, M.D., lead author of the SSO2 study, and professor of medicine at Columbia University Medical Center in New York, N.Y. "The larger the heart attack, the more heart muscle salvaged."

SSO2 — highly concentrated oxygen mixed in blood and delivered to the area of heart muscle dying after a heart attack — showed promise in animal studies and a previous human trial (AMIHOT-I). So Stone and his colleagues conducted AMIHOT-II with a similar protocol, focusing on patients with anterior ST-segment elevation myocardial infarctions (STEMIs) who were treated within six hours of heart attack symptoms.



"STEMIs are the large attacks," Stone said. "They have a really bad early prognosis because there is so much heart muscle lost." When a large area of the heart is damaged, heart failure is more likely.

Of the 733,000 Americans who suffer acute coronary syndromes (i.e. heart attack or chest pain) each year, 361,000 (almost half) have a STEMI. Catheter-based percutaneous coronary intervention (PCI) is a procedure that can effectively open blocked arteries in STEMI patients.

The AMIHOT-II researchers studied 301 STEMI patients who arrived within six hours after the onset of symptoms at 20 sites in four countries. The researchers randomized 222 to receive PCI plus SSO2 — infused for 90 minutes during treatment -- and 79 to PCI only. Some of their analyses also included data pooled from 101 patients from the AMIHOT-I.

Major study findings included:
In AMIHOT-II patients, heart damage 14 days after treatment averaged 26.5 percent of the left ventricle for PCI-only patients and 20 percent for the PCI plus SS02 group. Pooled data from both AMIHOT studies showed 25 percent damage in PCI-only patients and 18.5 percent in the SSO2 group. Among 154 patients whose left ventricle ejected less than 40 percent of the blood with each contraction prior to treatment, the PCI-only group had 33.5 percent damage versus 23.5 percent in the SSO2 patients. "For patients with large heart attacks, this is the first therapy shown to be beneficial in an adequately powered, multicenter trial," Stone said. In those with more than 40 percent blood ejection, muscle damage was 16.5 percent in PCI-only patients and 12.5 percent in the SSO2 group, which is a similar relative reduction in heart attack size as in patients with larger attacks, but a smaller absolute reduction. Researchers found no significant differences between the two groups of AMIHOT-II patients in the levels of blood markers that indicate a heart attack, or in the percentage of heart muscle at risk of dying, which was measured three hours after treatment. At 30 days post-op, the pooled data showed the two groups had similar percentages of major adverse events — death, another heart attack, reopening the same heart artery and stroke: 4.7 percent for the SSO2 patients and 5.1 percent for PCI-only group. "Some scientists have questioned the safety of SSO2 in heart patients, but only a few major and minor problems occurred in AMIHOT-II, and the study met all of its pre-defined safety endpoints," Stone said. In the same issue of Circulation: Cardiovascular Interventions, Francesco Liistro, M.D., and colleagues at San Donato Hospital in Arezzo, Italy, reported that manually removing a blood clot during PCI provides STEMI patients greater heart muscle perfusion and recovery of left ventricle function. In their single-center study, researchers randomized 55 patients to clot aspiration and 56 to standard PCI. In PCI, a physician typically inflates a balloon on a catheter tip to flatten a clot against the vessel wall, and then inserts a metal-mesh stent to prop the vessel open. Instead of using a balloon, which leaves clot debris in the blood, the team pushed a special catheter into the blockage and sucked the clot into the tube to remove it from the body before stenting.

Major study findings included: The ST-segment of an electrocardiogram returned to normal in 39 (71 percent) of the clot-aspiration group versus 22 (39 percent) of those getting standard PCI. Ninety-six percent of aspiration patients reached TIMI grade 3, the desired blood flow through the opened artery, compared to 82 percent for the standard PCI group. Aspiration patients showed a higher rate of artery perfusion, as measured by ultrasound, than those getting standard PCI, 85 percent versus 64 percent. Source: American Heart Association


Source : www.physorg.com/news172253019.html

 

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