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

Abstract

SUMMARY Although theextent ofenzymatically estimated infarct size appearstobeanimportant determinant ofmorbidity andmortality early after infarction, itsinfluences on long-term survival andlate ventricular dysrhythmia havenotyetbeencharacterized. Accordingly, we prospectively studied 173patients youngerthan66yearsofagewithout evidence ofprior myocardial infarction, whosurvived acutemyocardial infarction foratleast 24hours. Infarct size was estimated enzymatically anddysrhythmia quantified bycomputerfromtwo-channel, 24-hour ambulatory ECGs.Themean infarct size index (ISI) ofthose whodied was significantly larger thanthat ofsurvivors (46.5 ± 5.8(SEM) vs21.1i 1.4CK-g-Eq/m2, p < 0.001). Overall survival was significantly better after small (ISI < 15CK-g-Eq/m2) ormodest infarcts (15< ISI< 30)than after large infarcts (ISI30)(p< 0.01, p < 0.05, respectively). Regardless ofthelocus oftheinfarction, patients withsmall infarcts hada better prognosis thanthose withlarger infarcts. Latemortality was comparable after transmural andsubendocardial infarction, buthigher after anterior thanafter inferior infarction (15%vs 6%;p < 0.05). Amongthe10clinical andhemodynamic variables evaluated withmultivariate analysis, ISI(but notinfarct locus), peakplasma creatine kinase, congestive failure atthetimeofadmission, ageandgender weresignificantly related tomortality. Premature ventricular complexes were more frequent among patients withmodest orlarge infarcts (ISI15)throughout thefollow-up (p< 0.05), regardless ofinfarct locus. Thus, theextent ofinfarction isa strong determinant ofbothventricular dysrhythmia andmortality, late aswell asearly after acutemyocardial infarction. MORTALITY EARLY after acutemyocardial infarction isrelated toage,thepresence orabsence of oldmyocardial infarction, andthesite andextent of myocardial infarction sustained.1-5 Inaddition, theincidence andseverity ofventricular dysrhythmia during thefirst 24hours after infarction reflect theamountof myocardium damaged.6 7Long-term survival appears toreflect inpart theseverity oftheinfarct based onindirect criteria, such asthepresence ofcongestive heart failure, depressed ejection fraction anddyskinesis. Further, late ventricular dysrhythmia appears tocorrelate notonly with theseverity ofcoronary artery diseasebutalsowithleft ventricular contraction abnormalities, which inturnreflect theextent ofinjury.'2' 13 Thisstudy wasdesigned todetermine whether the extent ofinfarction isanimportant determinant ofthe incidence andseverity ofventricular dysrhythmia and mortality lateafter infarction. Becausepotential relationships might beobscured byadvanced ageor oldinfarcts,3 onlypatients aged65years oryounger andwithout historical or electrocardiographic evidence ofprevious myocardial infarction were studied.