The influence of location and extent of myocardial infarction on long-term ventricular dysrhythmia and mortality.

Although the extent of enzymatically estimated infarct size appears to be an important deter- minant of morbidity and mortality early after infarction, its influences on long-term survival and late ven- tricular dysrhythmia have not yet been characterized.Accordingly, we prospectively studied 173 patients younger than 66 years of age without evidence of prior myocardial infarction, who survived acute myocardial infarction for at least 24 hours.Infarct size was estimated enzymatically and dysrhythmia quantified by com- puter from two-channel, 24-hour ambulatory ECGs.The mean infarct size index (ISI) of those who died was significantly larger than that of survivors (46.5 ± 5.8 (SEM) vs 21.1 i 1.4 CK-g-Eq/m2, p < 0.001).Overall survival was significantly better after small (ISI < 15 CK-g-Eq/m2) or modest infarcts (15 < ISI < 30) than after large infarcts (ISI 30) (p < 0.01, p < 0.05, respectively).Regardless of the locus of the infarction, patients with small infarcts had a better prognosis than those with larger infarcts.Late mortality was com- parable after transmural and subendocardial infarction, but higher after anterior than after inferior infarction (15% vs 6%; p < 0.05).Among the 10 clinical and hemodynamic variables evaluated with multivariate analysis, ISI (but not infarct locus), peak plasma creatine kinase, congestive failure at the time of admission, age and gender were significantly related to mortality.Premature ventricular complexes were more frequent among patients with modest or large infarcts (ISI 15) throughout the follow-up (p < 0.05), regardless of in- farct locus.Thus, the extent of infarction is a strong determinant of both ventricular dysrhythmia and mor- tality, late as well as early after acute myocardial infarction.MORTALITY EARLY after acute myocardial in- farction is related to age, the presence or absence of old myocardial infarction, and the site and extent of myocardial infarction sustained.1-5In addition, the in- cidence and severity of ventricular dysrhythmia during the first 24 hours after infarction reflect the amount of myocardium damaged.6 7 Long-term survival appears to reflect in part the severity of the infarct based on in- direct criteria, such as the presence of congestive heart failure, depressed ejection fraction and dyskinesis.Further, late ventricular dysrhythmia appears to cor- relate not only with the severity of coronary artery disease but also with left ventricular contraction abnormalities, which in turn reflect the extent of injury.'2'13This study was designed to determine whether the extent of infarction is an important determinant of the incidence and severity of ventricular dysrhythmia and mortality late after infarction.Because potential relationships might be obscured by advanced age or old infarcts,3 only patients aged 65 years or younger and without historical or electrocardiographic evidence of previous myocardial infarction were studied.