No abstract

A B S T R A C T The effects

A B S T R A C T The question of whether or not the size of an area of myocardial infarction, measured at 1 wk after coronary occlusion, can be influenced by coronary artery reperfusion was examined in dogs. In seven control experiments the anterior descending coronary artery was ligated, while in seven other studies the occlusion was released after 3 hr. In all animals calibrated photographs were used to assess the zone of hypoperfusion and the acutely injured area of epicardial ST segment elevation, as well as the extent of damage at postmortem 1 wk later. In control dogs, the gross infarct size at postmortem averaged 63.8±7.3% of that predicted from the acutely injured zone. However, in reperfused hearts the average gross infarct size at 1 wk was only 10.2+4.4% of that predicted. Transmural specimens were obtained at autopsy for histology and measurement of myocardial creatine phosphokinase (CPK) activity from sites initially used for epicardial electrocardiography. In control animals, there was a direct relationship between the degree of ST segment elevation and the degree of cell necrosis in transmural histologic sections. ST segment elevation also predicted myocardial CPK (international units per milligram protein): log CPK = -0.0613 ST + 1.17 (r = 0.66, n = 56 sites). In the reperfused animals, log CPK =-0.166 ST + 1.36 (r = 0.69, n = 46 sites) showing almost complete preservation of CPK activity at 1 wk, sparing being most prominent in the epicardial zone. Similarly, there was a good correlation between myocardial CPK activity and the histological assessment of cell destruction, the degree of cell damage = -0.152 CPK + 3.86 (r = 0.86; n = 102 sites). Thus, control dogs showed severe myocardial CPK depletion

The purpose of this study was to evaluate the need for permanent pacing in patients who have survived the effects of anterior myocardial infarction with complete heart block and have returned to sinus rhythm but who are left with impairment of intraventricular conduction. We reviewed. All had been referred with recent anterior myocardial infarction complicated by the development of complete heart block. It was not known whether there was pre-existing fascicular block before infarction. In 2 patients (Cases 3 and 6) a narrow QRS in the presence of complete heart block suggested proximal atrioventricular block. In all other patients the level of the block was considered to be distal in site because of the slow rate of the escape pacemaker and a QRS width of at least 0 12 s. All patients needed temporary pacing.The diagnosis of acute myocardial infarction was established by a typical history accompanied by characteristic enzyme rises and the development of pathological Q waves accompanied by ST segment and T wave changes in the anterior chest leads. Bundle-branch block was defined according to the criteria of Goldman (1967) and the criteria for hemiblock were those of Rosenbaum (1970). Partial bilateral bundle-branch block was defined as right bundle-branch block and left anterior hemiblock or right bundle-branch block and left posterior hemiblock.The usual hospital stay was at least 3 weeks and follow-up observations were obtained in all patients. His bundle electrograms were recorded in 8 patients after return to sinus rhythm, using the technique described by Scherlag et al. (1969). 186

Between the years 1960 and 1974, 839 patients were paced for chronic complete atrioventricular block. Analysis of survival compared with the general population showed that 170 deaths were expected according to standard mortality tables and 288 actually occurred, giving a ratio of actual to expected deaths of 1.7:1. Patients with a definite history of myocardial infarction showed a higher than average mortality when paced. Mortality was not influenced whether heart was constant or intermittent, whether the ventricular rate was below or above 40/minutes, or whether QRS duration was greater or less than 0.1 second. Analysis of the age groups paced disclosed the most important correlations. Between the ages of 80 and 89 years paced patients could expect to survive as long as other of the same age without heart block. There was, however, a very high ratio of 4.5:1 for 90 patients in the age group 50 to 59 years. The reason for the high mortality ratio was uncertain but it may have been the result of a greater incidence of underlying coronary artery disease.