Changes in diastolic time with various pharmacologic agents: implication for myocardial perfusion.

Abstract

SUMMARY Diastolic time (DT) is calculated as the cycle length (RR) minus electromechanical systole (QS2). The ratio of DT (RR-QS2) to RR interval times 100, or the percent diastole (%D), varies nonlinearly with heart rate (HR), increasing rapidly with decreasing HR. The effect of commonly used cardioactive agents on %D was studied in five groups of normal subjects.In group I (n = 12), propranolol (160 mg daily) increased %D from 55. DIASTOLIC TIME can be calculated as the cardiac cycle (RR) minus electromechanical systole (QS2). It has a curvilinear relationship with heart rate (HR), increasing rapidly as rates fall below 75 beats/min. Cardioactive drugs may affect diastolic time by altering HR, QS2 or both. Subendocardial perfusion and perfusion distal to a significant obstruction in patients with coronary artery disease is nearly all diastolic. As such, it is related not only to diastolic perfusion pressure and microcirculatory tone, but also to the diastolic time.'-'0 While the effect of cardioactive drugs on systolic time intervals (STIs) has been studied,'1-14 the effect of these agents on diastole has not been emphasized. In this study we investigated the effect of commonly used cardioactive drugs on diastolic time in normal subjects.Material and Methods

Myocardial metabolic and hemodynamic effects of dobutamine in heart failure complicating coronary artery disease.

“…An adverse metabolic response was not seen in our patients with CM, but did occur in four of 18 SUMMARY Digoxin (5 mg/mI) was added to 10-mg and 20-mg pellets of purified primary and secondary amyloid fibrils, a normal human liver and heart homogenate and a homogenate from the heart of a patient with amyloid cardiomyopathy who had not received digitalis. After centrifugation, the supernatants were recovered and assayed for digoxin concentrations.…”

“…The study population consisted of 18 14 CAD patients decreased their PCWP by 33% (23.3 to 15.6 mm Hg). The double product of heart rate and systolic AP increased comparably in both groups (41% and 42%), but the four adverse responders had a higher double product during dobutamine infusion than the other 14 CAD patients (163.4 vs 152.5 X l02).…”

Long-Term Heart Rate Reduction Induced by the Selective I f Current Inhibitor Ivabradine Improves Left Ventricular Function and Intrinsic Myocardial Structure in Congestive Heart Failure

“…The fact that longterm ivabradine administration induces myocardial angiogenesis, as described in normal animals for the bradycardic agent alinidine, 24 and thus prevents coronary rarefaction suggests that ivabradine probably augments myocardial perfusion. Moreover, because the heart rate-diastolic time relation is nonlinear, the decrease in heart rate induced by ivabradine most likely results in an increase in the diastolic part of the cardiac cycle, 25 leading to an enhanced coronary perfusion time and thus increasing myocardial perfusion, especially to the deeper layer. 26 Finally, an increase in coronary perfusion due to HRR would prevent the development of coronary endothelial dysfunction provoked by the long-term decreased perfusion observed in CHF 27,28 and, by preventing local hypoxia, could diminish the local production of cytokines such as interleukin-1, interleukin-6, and tumor necrosis factor-␣, 29 free radicals, 30 and/or vasoconstrictors such as endothelin, 31 all factors implicated in the deterioration of LV function/remodeling and intrinsic tissue structure.…”

Comparison of the haemodynamic profiles of elgodipine and nicardipine in the anaesthetized dog

“…Reflex tachycardia is an undesirable consequence of acute vasodilatation which may worsen cardiac ischaemia, either as a result of increased myocardial oxygen demand, or by reducing diastolic filling time thus impairing coronary perfusion (Boudoulas et al, 1979). Unlike nicardipine which, when reflexes were functional, produced dose-related increases in MVO2, elgodipine did not change this parameter significantly.…”