The American journal of cardiology
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Comparative Study
Comparison of right atrial pacing soon after myocardial infarction with treadmill testing 6 months later.
Seventy-four patients recovering from acute myocardial infarction underwent right atrial pacing before hospital discharge, and treadmill exercise testing 6 months later. The early right atrial pacing test was positive in 32 patients (43 percent) and the late treadmill test was positive in 32 patients (42 percent). The results of the two tests were concordant in 77 percent of the patients, 23 with an ischemic response and 34 with a normal response on both tests. ⋯ This finding may explain the similar frequency of ischemic responses to the two tests. These results indicate that the response to right atrial pacing soon after myocardial infarction is a good predictor for the presence or absence of an ischemic response to treadmill testing 6 months later. Thus, early right atrial pacing at the time of hospital discharge may be used to determine the pace of rehabilitation and short-term prognosis.
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Labetalol, an alpha and beta receptor blocking agent, was evaluated in 11 patients with documented coronary artery disease and stable angina. The mean dose of labetalol was 1.5 (range 1 to 2) mg/kg. Cardiovascular effects began within 1 minute after injection and were maximal within 10 minutes. ⋯ Coronary sinus flow increased from 107 +/- 26 to 118 +/- 25 ml/min (p less than 0.01) and coronary vascular resistance decreased from 1.0 +/- 0.2 to 0.77 +/- 0.1 mm Hg/ml per min (p less than 0.001). Labetalol may be a useful adjunct in the treatment of angina not only because it diminishes myocardial oxygen requirements but also because it improves coronary hemodynamics. Thus, labetalol appears to have some advantage compared with the usual beta blocking agents with their potentially detrimental effects on coronary hemodynamics.
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The echocardiographic appearance of fibrotic thickening and calcification of mitral valve chordae tendineae and left ventricular papillary muscles in 17 patients is described. Pathologic proof of excessive fibrosis or calcification was obtained in five patients. In a sixth patient, calcium was demonstrated on angiography to extend from the chordae into papillary muscle. ⋯ One patient had rheumatic mitral valve disease. Many patients had mitral regurgitation and most had a history, physical examination and radiologic findings compatible with congestive heart failure. Although the origin and importance of the chordal and papillary muscle changes reported are not known, their frequent association with mitral regurgitation and with congestive heart failure suggests possible interrelations.