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Some patients who suffer acute myocardial infarction (AMI, heart attack) show irregular waves, such as ST-segment elevation, on their electrocardiogram (ECG). These waves reflect the electrical activity of the heart, and larger than normal Q-waves reflect damage to the left ventricle. Among heart attack patients who have ST-segment elevation on their ECG, those who receive thrombolytic or clot-busting medications are more likely to develop non-Q-wave-MI. This signals a better prognosis than Q-wave-MI, according to a meta-analysis of five randomized controlled trials on thrombolysis, which was supported in part by the Agency for Healthcare Research and Quality (HS06208).
The meta-analysis revealed that among this group of patients, those who developed a non-Q-MI as compared with a Q-wave-MI had 3.8 percent lower rates of in-hospital death and 6.4 percent lower rates of 1-year death, as well as 2.9 percent and 3.5 percent lower in-hospital and 1-year reinfarction rates, respectively. In-hospital and 1-year mortality were also significantly lower for non-Q-MI patients who received thrombolysis compared with placebo/control patients who developed a non-Q-MI.
The subgroup of patients who develop non-Q as compared with Q-wave infarction after thrombolytic therapy may fare better because thrombolysis provides early and sustained opening of the infarct-related artery. This, in turn, limits left ventricular infarction and dysfunction. The five studies analyzed in this study were restricted to patients with AMI who had ST-segment elevation on the ECG. However, the majority of patients in whom non-Q-wave infarction develops do not show ECG changes such as ST-segment elevation or left bundle branch block that would lead the doctor at the bedside to administer thrombolytic therapy.
See "Development and prognosis of non-Q-wave myocardial infarction in the thrombolytic era," by Shaun G. Goodman, M.D., M.Sc., Aiala Barr, Ph.D., Anatoly Langer, M.D., M.Sc., and others, in the August 2002 American Heart Journal 144, pp. 243-250.
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