Evaluation of biochemical functions and ventricular performance in regional ischemic-reperfused myocardium by afterload reduction: differential effects of calcium blocking and non-calcium blocking vasodilators.

The effects of afterload reduction with and without calcium blockade on reperfusion injury were studied in the pig. Reversible occlusion of the left anterior descending coronary artery was performed for 60 minutes followed by 120 minutes of reperfusion. For 15 minutes prior to and throughout reperfusion, treatment was administered with a calcium blocker (nifedipine or verapamil), a metallic organic dye and Ca2+ antagonist (ruthenium red), a vasodilator (nitroprusside), or saline. Biochemical functions, i.e., mitochondrial oxidative phosphorylation, myocardial ATP and Ca2+ content, and sarcoplasmic reticulum Ca2+ uptake were determined. Regional left ventricular wall motion was measured echocardiographically. Nifedipine and ruthenium red improved biochemical indices of ischemic myocardium in part by reducing afterload and thereby reducing oxygen demand and in part by reducing calcium entry into cells and mitochondria. Verapamil in the doses used failed to reduce afterload and demonstrated no salutary effect on biochemical parameters in ischemic myocardium. Nitroprusside reduced afterload, improved mitochondrial ATP production and increased percent wall thickening. Our findings suggest that afterload reduction with and without calcium blockade during the early reperfusion phase improves ischemic myocardium. These changes are predominantly biochemical in nature.

QRS voltage measurements in autopsied men free of cardiopulmonary disease: a basis for evaluating total QRS voltage as an index of left ventricular hypertrophy.

Use of total 12-lead QRS electrocardiographic voltage as a criterion for left ventricular (LV) hypertrophy has been of recent interest. Although upper and lower limits of QRS voltage for individual electrocardiographic leads have been reported in clinically healthy men and women, the upper limit of total 12-lead QRS voltage has not been established in adults free of cardiopulmonary disease by clinical and necropsy criteria. Therefore, the total QRS voltage from all 12 electrocardiographic leads was determined in 30 autopsied men known to be free of cardiopulmonary disease by clinical assessment and by a special cardiac examination using postmortem coronary angiography and chamber partition determination of LV weight. Gross heart weight, LV weight and total QRS voltage are reported. Comparisons were made between disease-free patients and previously reported patients with aortic valve stenosis, aortic regurgitation and cardiac amyloidosis with respect to total QRS voltage and gross heart weight. Total QRS voltage and gross heart weight were significantly greater in patients with severe aortic stenosis (mean 245 mm) and severe aortic regurgitation (mean 274 mm) than in our patients (mean 127 mm). Total QRS voltage was significantly less, whereas gross heart weight was significantly greater in patients with cardiac amyloidosis (mean 101 mm) than in our normal subjects (mean 127 mm). These data provide a basis for evaluating the total 12-lead QRS voltage as a criterion for LV hypertrophy.