Left ventricular failure in acute myocardial infarction

In 30 patients with acute myocardial infarction complicated by either advanced atrioventricular or bundle branch block, pulmonary arterial wedge pressures were studied in relation to clinical and radiographic features of left ventricular failure, changes in central venous and pulmonary arterial pressures, and arterial hypoxemia. An increase in mean pulmonary arterial wedge pressure was poorly correlated with the presence of dyspnea, audible third or fourth heart sounds, or persistent basal rales; however, it was significantly related to radiographic evidence of pulmonary venous dilatation or edema, a systolic blood pressure of less than 100 mm Hg, gallop rhythm associated with tachycardia, and heart rate in patients with sinus rhythm and normal atrioventricular conduction. Increased mean right atrial pressure indicated increased mean pulmonary arterial wedge pressure in patients with isolated anterior infarction, but in several patients with isolated inferior infarction the level of right atrial pressure was disproportionately high. The pulmonary arterial diastolic pressure closely reflected the mean pulmonary arterial wedge pressure in the absence of obstructive airways disease or pulmonary embolism. The level of the arterial oxygen tension fell as the mean pulmonary arterial wedge pressure rose, but it was considerably reduced in some patients with only moderately increased pressures. However, the latter usually had radiographic evidence of pulmonary venous dilatation or edema, suggesting that the pressure had been elevated previously to higher levels.