Influence of nifedipine on coronary haemodynamics and myocardial metabolism in coronary artery disease

Calcium channel blockade with felodipine does not affect metabolic coronary vasodilation in patients with coronary artery disease

The effect of calcium channel blockers may affect the feedback mechanism between myocardial metabolic activity and coronary blood flow. To test this hypothesis the effect of calcium channel blockade on metabolic coronary flow regulation was studied. In 10 patients with stable coronary artery disease, coronary sinus blood flow and myocardial oxygen supply and consumption (MVO2) were measured both at sinus rhythm and during atrial pacing (30 beats/min above sinus rate), at control and during infusion of felodipine, a vasoselective dihydropyridine. The myocardial oxygen supply-consumption ratio at control (i.e., the slope of the regression line characterizing normal metabolic flow regulation) was 1.58 (95% CI, 1.38-1.80). Following infusion of felodipine, systemic and coronary vascular resistance during sinus rhythm decreased by 20 +/- 11% and 23 +/- 15%, respectively, and coronary venous oxygen saturation increased from 36 +/- 6% at control to 42 +/- 7% (p = 0.047) during infusion of felodipine. The myocardial oxygen supply-consumption ratio, characterizing metabolic flow regulation during felodipine, was 1.52 (95% CI, 1.26-1.78) and thus not different from control. Metabolic coronary flow regulation was not affected by administration of felodipine, although the setpoint of this regulation mechanism might have been offset by the initial drug-induced coronary vasodilation, which persisted during pacing.

Cardioprotective effect of intracoronary nifedipine during percutaneous transluminal coronary angioplasty. A French double-blind cross-over multicentre study

The aim of this double-blind, placebo-controlled, cross-over study was to assess the cardioprotective effect of intracoronary nifedipine during percutaneous transluminal coronary angioplasty balloon occlusion. A balloon inflation without drug injection was initially made to ascertain that a shift of the ST segment (> or = 2 mm, 0.08 s after the J point) appeared (inclusion criterion). Two other balloon inflations were preceded by intracoronary injection of either 0.2 mg nifedipine or placebo, distal to the stenosis through the balloon catheter. The evaluation criteria were (1) time to ST segment shift, and (2) maximal amplitude of ST segment shift caused by balloon occlusion. Comparison of the data used an analysis of variance. Sixty-seven patients (mean age 54 +/- 8 years; 54 male, 13 female) were studied; 50 patients had 1-, 16 patients 2- and 1 patient 3-vessel disease. The dilated vessel was the left anterior descending coronary artery (n = 51), the right coronary artery (n = 12) and the left circumflex coronary artery (n = 4). Balloon inflation time was 100 +/- 31 s in the nifedipine group and 93 +/- 29 s in the placebo group. Five patients were excluded (procedure stopped after the first inflation in 1 and ST segment shift < 2 mm during the first inflation in 4). The time to 2-mm ST segment shift was longer in the nifedipine group than in the placebo group (62 +/- 40 s versus 51 +/- 40 s, P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

The role of nitrates, beta blockers, and calcium antagonists in stable angina pectoris

Numerous controlled studies have shown that nitrates, beta blockers, and calcium antagonists are effective in the treatment of stable angina pectoris. The pharmacokinetics, pharmacodynamics, and hemodynamic effects of these agents are different, and thus combination therapy offers additive improvement and also counterbalancing of the undesirable side effects of each drug. The choice of therapy depends on the severity of symptoms, associated diseases, compliance, side effects, and status of left ventricular function. The main mechanism of improvement is a decrease in myocardial oxygen consumption, though an increase in coronary blood flow is another potential reason for the use of calcium blockers. This review considers the properties of these drugs, their mechanism of action, and the results of randomized studies.

Effects of nicardipine on exercise- and pacing-induced myocardial ischemia in angina pectoris

To define the effects of nicardipine, a new dihydropyridine calcium antagonist drug, on exercise- and pacing-induced myocardial ischemia, 15 men with coronary artery disease were studied during cardiac catheterization. Nicardipine was administered intravenously as a 2-mg bolus followed by an infusion titrated to maintain a 10- to 20-mm Hg decrease in systolic arterial pressure. At rest, nicardipine decreased systemic and coronary vascular resistances, left ventricular end-diastolic pressure and increased coronary blood flow, heart rate and myocardial oxygen consumption. During bicycle exercise-induced myocardial ischemia, nicardipine significantly prolonged exercise duration and time to 1 mm of ST-segment depression. These changes were associated with no alteration in the product of systolic pressure and heart rate, decreased left ventricular end-diastolic pressure, systemic and coronary vascular resistances and increased coronary blood flow, as well as myocardial oxygen consumption. During atrial pacing, the heart rate threshold for myocardial ischemia was not changed by nicardipine administration, despite improvement in the ratio of coronary blood flow to myocardial oxygen consumption and hemodynamic changes otherwise similar to those during exercise. Nicardipine favorably influenced myocardial metabolic state, as indexed by lactate extraction during pacing-induced ischemia. Nicardipine is a potent coronary and systemic vasodilating drug that improves exercise tolerance and myocardial metabolic response to pacing stress, the mechanism for which appears to be partially mediated through increased coronary blood flow.

Observations on the warm up phenomenon in angina pectoris

Adaptation to exercise was investigated in 14 men aged 34-69 years (mean 51) with stable exertional angina caused by occlusive coronary artery disease. All underwent exercise electrocardiography to symptom limitation according to the Bruce protocol (first effort), and exercise to the onset of angina (warm up) followed by four minutes' rest, followed by exercise to symptom limitation (second effort). This protocol was repeated after sequential treatment for one month each with nifedipine 10 mg three times a day and with timolol 10 mg twice a day. Warm up significantly increased walking time to the onset of angina by 34.5% and to maximal exercise by 29.5%. The heart rate and rate-pressure product were significantly higher on second effort both at the onset of angina (by 7.0% and 11.1% respectively) and at maximal exercise (by 10.5% and 15.4% respectively). ST segment displacement was not significantly different after warm up. The effect of warm up on walking time to the onset of angina was markedly reduced after treatment with nifedipine but little influenced by timolol. Mean (SE) walking time after warm up on no treatment was 10.1 (0.7) min; after treatment with nifedipine it was 10.0 (0.6) min and after treatment with timolol it was 9.7 (0.4) min. These data demonstrate a substantial improvement in exercise performance after warm up and are consistent with the hypothesis that submaximal exercise in angina pectoris facilitates myocardial oxygen uptake by coronary vasodilatation.

Regional cardioprotection by subselective intracoronary nifedipine is not due to enhanced collateral flow during coronary angioplasty

Twelve patients with proximal stenosis of the left anterior descending artery, normal myocardial wall motion but without angiographically demonstrable collateral circulation, were studied during transluminal occlusion. Prior to the first transluminal occlusion before crossing the lesion with the balloon, patients were randomly given 0.2 mg nifedipine or its solvent in the left mainstem. The same dose was repeated via the balloon catheter, positioned across the lesion, immediately prior to the second transluminal occlusion. In all patients great cardiac venous flow and ST-elevation were monitored during and after each transluminal occlusion. The lactate extraction ratio A-GCV/A (A = arterial, GCV = great cardiac vein) was determined prior to the angioplasty procedure, 10-15 seconds after each transluminal occlusion and 10 minutes after the third transluminal occlusion. Great cardiac venous flow rose significantly to an average of 160% of basal flow when nifedipine was administered into the mainstem before the angioplasty procedure while its solvent had no effect. During each transluminal occlusion, great cardiac venous flow diminished on average by 30% in those who received nifedipine and by 28% in those who received only its solvent. This difference was statistically not significant. After angioplasty great cardiac venous flow was slightly, but not significantly, increased in both groups with respect to basal flow (104% resp. 120% of control). Patients who received nifedipine in the post-stenotic area just before the second transluminal occlusion, had significantly lower lactate production, measured immediately after the transluminal occlusion compared with the patients who received only its solvent (P less than 0.01). The ST-elevation during the second transluminal occlusion was significantly lower in the nifedipine group (0.1 mm in nifedipine group versus 1.4 mm in solvent group; P less than 0.05, unpaired t-test). Nifedipine given intracoronary in the post-stenotic area just before coronary angioplasty reduces lactate release and electrocardiographic signs of myocardial ischemic injury. This regional cardioprotective effect seems not due to an enhanced collateral flow, but to a regional cardioplegic effect, which precedes the ischemic event.

Myocardial metabolism and coronary sinus blood flow during coronary artery surgery: effects of nitroprusside and nifedipine

The effects of nitroprusside and nifedipine on hemodynamics, coronary dynamics, and global myocardial metabolism were compared in two groups of patients undergoing elective coronary artery surgery, who were anesthetized with fentanyl, 100 micrograms/kg. After induction of anesthesia, either nitroprusside or nifedipine was started as follows: group S (n = 11) received nitroprusside at an initial rate of 1.3 micrograms/kg/min; group N (n = 9) received nifedipine at an initial rate of 0.7 micrograms/kg/min. Infusion rates were adjusted to maintain systolic blood pressure (SBP) between 80% and 120% of preinfusion (control) values. Control measurements were obtained 10 minutes after intubation. Then vasodilator infusion was started. Additional measurements were obtained 10 minutes after the start of infusion (before surgery) and after sternotomy. The mean (+/- SD) total dose requirements were: nitroprusside, 1.6 +/- 0.3 micrograms/kg/min; and nifedipine 1.1 +/- 0.7 micrograms/kg/min. The mean (+/- SD) total infusion time was: nitroprusside, 32 +/- 5 minutes; and nifedipine, 37 +/- 7 minutes. After 10 minutes of infusion there were decreases in SBP (p less than 0.001) and diastolic blood pressure (DBP; p less than 0.01) in group S. In group N only SBP decreased (p less than 0.01). At this time there were no significant changes in coronary sinus blood flow (CSBF) or myocardial oxygen consumption (MVO2) in either group. After stenotomy DBP remained decreased (p less than 0.05) in group S.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic and hemodynamic effects of nicardipine during pacing-induced angina pectoris

During repeat exercise testing in 10 patients with stable angina, individual optimal doses of nicardipine were determined. Hemodynamic values and cardiac metabolism were studied during 2 pacing periods carried out before and after this dose (mean 5.3 mg). Postpacing ST-segment depression diminished (1 mm) after nicardipine administration (p less than 0.05), whereas pacing time to onset of angina did not change. Nicardipine administration increased heart rate 16% (p less than 0.005) and reduced systolic (10%) and diastolic (8%) blood pressures (both p less than 0.005). Coronary blood flow increased 16% (p less than 0.05) and coronary vascular resistance decreased 24% (p less than 0.01). Myocardial oxygen consumption was unchanged despite an 11% decrease in rate-pressure product during pacing (p less than 0.02). In the control state before nicardipine administration, metabolic signs of ischemia included release of lactate across the heart in 7 patients, decreased mean free fatty acid and glutamate uptake and alanine release during pacing, together with increased glucose uptake and citrate release during recovery. After nicardipine lactate release decreased in 5 of the 7 patients, pacing no longer changed free fatty acid, glutamate and alanine uptake/release from the level at rest. During recovery glucose uptake was reduced and citrate release was unaffected. The hemodynamic data indicate that nicardipine is a systemic and coronary vasodilator, increasing oxygen supply to the ischemic myocardium. The metabolic results indicate a change in substrate utilization toward that of normal heart, suggesting improved aerobic energy supply.

The haemodynamic effects of nifedipine, verapamil and diltiazem in patients with coronary artery disease. A review

Of the 3 most widely used calcium antagonists--nifedipine, verapamil and diltiazem--nifedipine is the most potent arterial vasodilator. Increases in cardiac output and coronary blood flow following nifedipine administration result in part from the afterload reduction. Reflex adrenergic stimulation produces an increase in heart rate and masks a direct inhibitory effect on myocardial contractility. The negative inotropic action of nifedipine is observed during intracoronary administration or may be made apparent by concurrent beta-blocker therapy. While verapamil is also a potent vasodilator, negative inotropic and dromotropic properties are more apparent in therapeutically used dosages. Reflex sympathetic activation is also triggered by verapamil, with an offsetting of the negative inotropic effects such that little change in cardiac output results. A decrease in myocardial oxygen consumption, with or without a decrease in coronary sinus blood flow, has regularly been observed following verapamil administration. Reduced oxygen demand appears to be a major mechanism of its antianginal effect. The heart rate X systolic pressure product is decreased both by the fall in arterial pressure and, particularly after oral administration, by a decrease in heart rate. Diltiazem produces similar haemodynamic and electrophysiological effects to those of verapamil but has less potency in inducing arterial dilatation and more of a tendency to slow the heart rate. Diltiazem does not appear to cause significant increases in coronary blood flow or bring about improvement in ejectional and isovolumic indices of myocardial contraction - evidence of its intrinsic negative inotropic effect.