Effects of ryanodine on cat papillary muscle and isolated rat heart.

The neutral alkaloid, ryanodine, has several actions on cardiac muscle. To delineate better its mode of action, we studied ryanodine's effect upon contracting cat papillary muscles under changing loading conditions and stimulation frequencies. We also studied ryanodine's physiologic and metabolic effects upon isolated rat hearts. The results of our study suggest the following: (1) ryanodine causes both decreased release and decreased uptake of calcium by the sarcoplasmic reticulum; (2) elevation of high-energy phosphates secondary to decreased energy requirements is due to decreased calcium availability to the myofilaments during systole; (3) the slowed or incomplete relaxation caused by ryanodine may be a stimulus for myosin phosphorylation; (4) ryanodine probably decreases calcium movement through the sarcolemma and so increases adenosine and inorganic phosphate and decreased cyclic adenosine monophosphate (AMP) concentration in the myocardium; and (5) the effect of ryanodine on altered loading conditions and contraction velocities can be understood in terms of decreased calcium availability to the myofilaments.

Mechanism of protection from atherosclerosis by verapamil in the cholesterol-fed rabbit.

Seventy-two rabbits were separated into groups to receive no drug, subcutaneous verapamil, metoprolol, hydralazine, metoprolol and hydralazine, or oral verapamil in 1 of 3 doses daily for 10 weeks. They also received a high-cholesterol diet and had serum triglyceride, cholesterol, and verapamil levels measured twice during the study. Blood pressure (BP), heart rate and weight were measured every 10 days. Approximately 60% of the rabbits given verapamil had detectable levels of the drug in their serum. This group had significantly less severe atherosclerosis in their aortas at the time they were killed, even though they had significantly higher cholesterol levels than the other groups. This group also did not have different BP than the other groups (except for the subcutaneous verapamil group). Thus, protection from atherosclerosis by verapamil in the cholesterol-fed rabbit is not the result of lowering of BP.

New technique for detection of changes in QRS morphology of ECG signals.

With the use of the electrocardiogram (ECG) as a prototype signal, a new technique was devised for detecting signals embedded in noise. Averaged "normal" digitized ECG signals formed a template to which subsequent ECG QRS complexes were compared. The difference between the averaged template signals and subsequent normal beats was white noise, whereas the difference between the template and ectopic beats consisted of nonrandom signal variation. The template to new signal comparison for the zero-, first-, second-, and third-order differences utilized an approximate F test. Accurate detection of abnormal signals associated with high- and low-frequency noise is accomplished with this method, and the practical clinical utility of the method is under study.

Atrial flutter associated with acute myocardial infarction.

Between 1966 and 1968, 35 of 340 patients (10.3 percent) admitted to the Los Angeles County-University of Southern California Medical Center with documented myocardial infarctions were noted to have atrial flutter while being monitored in the coronary care unit. This incidence is higher than that found in most previous studies. Patients with atrial flutter had significantly higher mortality than infarction patients without flutter (P <0.05). The increased mortality for those with flutter was apparently the result of concurrent complications and probably not because of the arrhythmia alone. Atrial flutter recurring for more than one day was associated with further increase in mortality (P <0.02). Also, there was a higher death rate among patients with flutter who had anterior infarctions than among those with inferior infarctions, but the difference was not statistically significant. Most patients responded to treatment with antiarrhythmic drugs, but prior digitalis therapy apparently did not prevent the onset of atrial flutter.

The probability of surviving coronary bypass surgery. Five-year results from 1,718 patients.

This study of 1,718 men with bypass surgery from 1970 to 1974 in Milwaukee has indicated that the following factors are significantly associated with five-year survival: left ventricular end-diastolic pressure (LVEDP), plasma cholesterol level, coronary occlusion score, age, and left ventricular function (LVF). The 31 men with a previous stroke had a high risk (five-year survival was 32%). To serve as a guide to patient risk, a logistic model is used to predict five-year survival. These probabilities are tabulated for all combinations of LVEDP, age, LVF, occlusion score, and plasma cholesterol level.

Changes in occupation after coronary arteriography.

This study, involving 266 white males evaluates the effect of angiographically determined mild coronary artery impairment upon occupational status. Questionnaires filled out at the time of coronary arteriography and about 13 months later showed that in the interim 65% of the patients stayed in the same occupational status, 31% changed occupational status, and 4% retired. In both younger (less than or equal to 55 years) and older men (greater than 55 years) the proportion of retirees increased after angiography. Of those who remained employed, 19% changed to jobs with higher physical demands while 11% took jobs with lower physical demands. The decision to change the job did not seem to be affected by age or the presence of angina pectoris. Comparison of this patient population with U.S. national average has shown that the presence or awareness of coronary artery disease is associated with measured increase in occupational mobility, regardless of the severity of the disease. Our findings suggest that changes in occupational status after determination of mild coronary artery disease are motivated by psychological rather than physiological factors.

Preoperative risk factors and aorta-coronary bypass graft patency.

The relationship between graft patency and the presence of presurgical prognostic factors was studied in 636 patients who have undergone aorta-coronary bypass operation. We have found a positive correlation between vein graft patency and both coronary artery constriction score (p less than 0.01) and diastolic blood pressure (p less than 0.05). In patients studied up to one year after surgery, high graft patency was associated with both higher diastolic pressures (p less than 0.03) and higher cholesterol levels (p less than 0.001). However, high cholesterol levels also were associated with coronary arterial obstruction. In patients studied more than a year after operation, high constriction scores before the operation were associated with improved graft patency (p less than 0.03). Our findings indicate that short-term prognosis of the grafts is related mainly to hemodynamic variables.