Serial Observations on Left Ventricular Dysfunction in Acute Myocardial Infarction
II. Systolic Time Intervals in Power Failure
Systolic time intervals corrected for heart rate were studied serially in 50 patients with acute myocardial infarction (AMI) 1, 5, and 20 days after the onset of symptoms from simultaneously recorded kineto-, phono-, and electrocardiograms and carotid artery pulse tracings. Left ventricular ejection time (LVET), electromechanical systole (QA2), and mechanical systole (M1A2) decreased from the first to the fifth day (P < 0.001) and increased again toward normal by the twentieth day. There was a clear correlation with the clinically assessed severity of AMI; the high prevalence of abnormal values indicated a frequent and early impairment of left ventricular performance. In severe power failure, deterioration was indicated by progressive shortening of the systolic time intervals, as contrasted to gradual improvement noted in uncomplicated infarctions. Similarly, LVET, QA2, and M1A2 displayed a significant correlation with the grade of radiologically assessed pulmonary vascular congestion on the first day. A relationship between LVET, QA2, and isovolumic contraction time (ICT)/LVET and the degree of paradoxical cardiac pulsation became apparent on the fifth day. LVET, M1A2, ICT/LVET, and preejection period (PEP)/LVET were more abnormal in the nine patients who died than in the 41 survivors (P < 0.05). PEP and ICT showed no correlation with clinically or radiologically assessed severity or prognosis of infarction, in contrast to findings in chronic heart failure. Decrease of contractility in AMI appears not to be directly reflected in preejection intervals. These findings indicate the value of externally measured left ventricular systolic time intervals, especially LVET, in assessment of the severity and prognosis of AMI.
- Received August 3, 1970.
- Accepted April 26, 1971.
- © 1971 American Heart Association, Inc.