Beneficial enhancement of coronary blood flow by nifedipine. Comparison with nitroglycerin and beta blocking agents

Pharmacotherapy of Vasospastic Angina

Vasospastic angina is a diagnosis of exclusion that manifests with signs and symptoms, which overlap with obstructive coronary artery disease, most often ST-segment elevation myocardial infarction. The pharmacotherapy that is available to treat vasospastic angina can help ameliorate angina symptoms. However, the etiology of vasospastic angina is ill-defined, making targeted pharmacotherapy difficult. Most patients receive pharmacotherapy that includes calcium channel blockers and/or long-acting nitrates. This article reviews the efficacy and safety of the pharmacotherapy used to treat vasospastic angina. High-dose calcium channel blockers possess the most evidence, with respect to decreasing angina incidence, frequency, and duration. However, not all patients respond to calcium channel blockers. Nitrates and/or alpha1-adrenergic receptor antagonists can be used in patients who respond poorly to calcium channel blockers. Albeit, evidence for use of nitrates and alpha1-adrenergic receptor antagonists in vasospastic angina is not as robust as calcium channel blockers and can exacerbate adverse effects when added to calcium channel blocker therapy. Despite having a clear benefit in patients with obstructive coronary artery disease, the benefit of beta-adrenergic receptor antagonists, statins, and aspirin remains unclear. More data are needed to elucidate whether or not these agents are beneficial or harmful to patients being treated for vasospastic angina. Overall, the use of pharmacotherapy for the treatment of vasospastic angina should be guided by patient-specific factors, such as tolerability, adverse effects, drug–drug, and drug–disease interactions.

Coronary artery vasomotion and post-stenotic coronary artery blood flow after intracoronary lacidipine in patients with ischaemic heart disease: a pilot study

BACKGROUND

The calcium antagonist lacidipine has been shown to be highly vasoselective and to improve myocardial perfusion in hypertensive patients. However, its effects on coronary artery vasomotility and on post-stenotic coronary flow reserve in patients with atherosclerotic heart disease are unknown.

OBJECTIVES

This study was designed to investigate the acute direct effects of repeated infusions of lacidipine on epicardial coronary artery vasomotion and on post-stenotic coronary artery blood flow in patients with stable angina pectoris and angiographic evidence of coronary heart disease.

METHODS

In 8 patients with stable angina and moderate to severe stenosis of the left coronary artery, measurements of epicardial dimensions (quantitative angiography) and of coronary blood flow (Doppler guidewire) distal to a stenosis were performed at baseline and after 3 repeated intracoronary boluses of 12 microg of lacidipine. Results were compared with those obtained after 10 mg of intracoronary papaverine.

RESULTS

The intracoronary administration of lacidipine was well tolerated, without any adverse effects. Lacidipine significantly increased the minimal luminal diameter of the lesion (peak relative increase of 43.7%), without significant changes in heart rate and systolic aortic pressure. Intracoronary lacidipine caused a dose-dependent increase in coronary flow reserve. Maximal vasodilatory effects were equivalent to those obtained with intracoronary papaverine.

CONCLUSIONS

These results suggest that lacidipine acts directly as a potent vasodilator in stenotic epicardial vessels and improves myocardial perfusion distal to a moderately severe stenosis in patients with stable angina.

Underestimation of extent and severity of coronary artery disease by dipyridamole stress thallium-201 single-photon emission computed tomographic myocardial perfusion imaging in patients taking antianginal drugs

OBJECTIVES

This study evaluated the diagnostic value of dipyridamole plus low level treadmill exercise (dipyridamole stress) thallium-201 single-photon emission computed tomography (SPECT) in patients taking antianginal drugs.

BACKGROUND

Dipyridamole stress is the major substitute for maximal exercise in patients referred for myocardial perfusion imaging. Although antianginal drugs are commonly suspended before exercise, dipyridamole stress is usually performed without discontinuing these drugs.

METHODS

Twenty-six patients underwent two dipyridamole perfusion studies: the first without (SPECT-1) and the second with (SPECT-2) antianginal treatment. Twenty-one patients (81%) received calcium antagonists, 19 (73%) received nitrates, and 8 (31%) received beta-blockers. Eighteen of the patients underwent coronary angiography. Data are presented as the mean value +/- SD.

RESULTS

Visual scoring yielded significantly larger and more severe reversible perfusion defects for SPECT-1 than for SPECT-2. Quantitative analysis showed larger perfusion defects on stress images of SPECT-1 in the left anterior descending coronary artery (LAD) (25 +/- 21% vs. 17 +/- 15%, p = 0.003), left circumflex coronary artery (LCx) (56 +/- 35% vs. 48 +/- 36%, p = 0.03) and right coronary artery (RCA) (36 +/- 27% vs. 25 +/- 24%, p = 0.008) territories. Individual vessel sensitivities in the LAD, LCx and RCA territories were 93%, 79% and 100% for SPECT-1 and 64%, 50% and 70% for SPECT-2, respectively. These differences were highly significant for the LAD (p = 0.004) and LCx (p = 0.00004) territories. The overall individual vessel sensitivity of SPECT-1 was significantly higher than that of SPECT-2 (92% vs. 62%, p = 0.000003). Specificity was not significantly different in SPECT-1 compared with SPECT-2 (80% and 93%, p = 0.33).

CONCLUSIONS

Continued use of antianginal drugs before dipyridamole plus low level treadmill exercise thallium-201 SPECT may reduce the extent and severity of myocardial perfusion defects, resulting in underestimation of coronary artery disease.

Nifedipine gastrointestinal therapeutic system versus atenolol in stable angina pectoris. The Netherlands Working Group on Cardiovascular Research (WCN)

The gastrointestinal therapeutic system formulation of nifedipine enables a once-daily dosing resulting in predictable, relatively constant plasma concentrations. To evaluate the efficacy and safety of this formulation and to compare this with the beta-blocker atenolol, we conducted a double-blind, randomised, multi-centre study in 129 male patients with documented exercise induced angina pectoris. After 4 weeks' treatment, nifedipine (60 mg), improved time to onset of 0.1 mV ST-segment depression from 536 s by 72 +/- 117s, time to onset of pain from 619 s by 56 +/- 120 s, and total exercise time from 685 s by 40 +/- 88 s. Atenolol 100 mg, had a comparable effect, time to onset of 0.1 mV ST-segment depression improved from 496 s by 53 +/- 129 s, time to onset of pain from 572 s by 57 +/- 118 s, and total exercise time from 653 s by 33 +/- 99 s. Between group analysis revealed no statistically significant differences for these exercise parameters. Atenolol, but not nifedipine, significantly reduced heart rate and systolic blood pressure at rest and during exercise (P < 0.001 between groups), indicating different modes of action of the drugs. With regard to safety, both drugs were generally well tolerated. There were significantly (P = 0.01) more vasodilation related side effects with nifedipine. These data demonstrate that gastrointestinal therapeutic system formulation of nifedipine and atenolol as once-daily monotherapy are equally effective and safe, but with different effects on exercise parameters.

Calcium channel blockers in heart failure: help or hindrance?

Since their development, calcium channel blocking agents have stimulated interest in their potential benefit for a variety of cardiovascular disorders, including heart failure. The rationale for the potential benefit of calcium channel blockers in heart failure is multi-factorial, including vasodilation, correction of perturbed diastolic relaxation, anti-ischemic action, and potential for inhibiting myocyte hypertrophy and injury. Despite these potential benefits, the degree of salutary influence has remained controversial, and a number of studies have suggested potential adverse action in patients with heart failure, perhaps linked to either negative inotropic action or to reflex neurohormonal activation. Diversity among different agents, particularly with regard to tissue selectivity and pharmacokinetics may imply substantial differences in the relative benefits and risks in various subgroups of patients with heart failure. One trial with the newer dihydropyridine agent, amlodipine, indicates benefit to survival in patients with moderate to severe heart failure and reduced ejection fraction. The reproducibility of this finding and the mechanism for this benefit deserves further investigation.

Controversies concerning calcium antagonists

The paper discusses the controversial attitude regarding the safety of calcium channel blockers (CCBs), especially of the dihydropyridine nifedipine, induced through several meta-analyses of studies with CCBs by Dr. Furberg et al.; as a result, a detrimental effect of CCBs, especially during acute myocardial infarction, has been claimed. Several independent re-analyses of the 16 studies, all performed in the 1980s and mainly using the short-acting nifedipine capsule, did not confirm Furberg's results and showed an insignificant mortality difference between patients on CCBs versus those on control. Nevertheless, new safety studies applying long-acting CCBs (half-lives of 1 or more days) combined with efficacy assessments are necessary, both in hypertension as well as coronary artery disease, to finally clear up this important question.

Efficacy and safety of nisoldipine coat core in the management of angina pectoris, systemic hypertension, and ischemic ventricular dysfunction

The effects of the long-acting dihydropyridine calcium antagonist nisoldipine coat core (CC) have been investigated in > 3,500 patients with angina pectoris, hypertension, and ischemic ventricular dysfunction. In patients with angina pectoris, nisoldipine CC improved total treadmill exercise duration (p = 0.027), delayed the onset of angina pectoris (p = 0.009), and increased time to exercise-induced ST-segment depression (p = 0.061). In general, nisoldipine 20-40 mg was effective, and the dose-response curve flattened thereafter. In patients with hypertension, 10-40 mg once daily as monotherapy reduced blood pressure (p < 0.05), with a fall in diastolic pressure of > or = 10 mm Hg or a final diastolic pressure of < 90 mm Hg in 35-63% of patients. In most patients followed for a year, nisoldipine CC was continued as monotherapy. Efficacy was similar in patients < 65 and > 65 years of age. In the Doppler Flow and Echocardiography in Functional Cardiac Insufficiency: Assessment of Nisoldipine Therapy (DEFIANT-I) study of patients recovering from myocardial infarction, nisoldipine CC had a salutary effect on diastolic ventricular function, with a higher transmitral early filling velocity and shorter isovolumic relaxation time than in patients receiving placebo. Bicycle exercise capacity was greater (by 12 W; 95% confidence interval, 0.8-23.3) and exercise-induced ischemia occurred less frequently. The nisoldipine CC data pool (3,679 patients) showed that the drug was well tolerated with a low incidence of side effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of nicorandil on regional perfusion and left ventricular function

Left ventricular function and regional perfusion were evaluated by two study designs in patient groups with stable ischemic coronary artery disease (CAD): (1) using conventional left ventricular angiographies and (2) applying myocardial contrast echocardiography. The aim of the studies was to establish the effects of sublingually or orally applied nicorandil (N) on pacing-induced myocardial ischemia (MIS). In the first angiographic study, in nine patients with ischemic CAD and with pacing-inducible MIS, the effect of N, 20 mg sublingually, on hemodynamics and regional wall motion (RWM) were studied. There were no parameter changes without MIS being induced when comparing measurements at the 7th and 14th minute after N application to control values (p > 0.05). In the 15th and 16th minutes after N, pacing-induced MIS could no longer be elicited but left ventricular pump function improved; comparing MIS with N versus MIS without N: ejection fraction improved by 21%, cardiac index by 37%, and RWM by 21%, while filling pressure fell by 41% and systemic vascular resistance fell by 29%. Thus, N-mediated "protection from ischemia" with rather improved hemodynamics and RWM corresponds with alterations that theoretically could have been expected after nitroglycerin given under the above conditions. In the second echocardiographic study, regional perfusion was assessed in 10 patients by intracoronary injection of a newly developed echo contrast medium (ECM) and measurement of ECM washout halftime (t1/2) over opacified myocardial regions of interest, which displayed wall motion abnormalities already at rest.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of nifedipine gastrointestinal therapeutic system and atenolol on antianginal efficacies and exercise hemodynamic responses in stable angina pectoris

A gastrointestinal therapeutic system (GITS) of nifedipine has been developed to provide a once-daily dosing, and predictable, relatively constant plasma concentrations. This study compared the antianginal efficacy of nifedipine GITS with a once-a-day beta-receptor blocker, atenolol. Seventeen patients with documented coronary artery disease and stable stress-induced angina pectoris were studied during a 2-week, single-blind, placebo baseline phase and a 12-week randomized, double-blind, active drug crossover efficacy phase, using the bicycle exercise test and ambulatory electrocardiographic recordings. Patients exercised significantly longer with nifedipine GITS (883 +/- 47 seconds) and atenolol (908 +/- 44 seconds) than with placebo (794 +/- 41 seconds). Nifedipine GITS reduced systolic blood pressure at all stages of exercise compared with placebo but, because heart rate tended to increase more during nifedipine therapy, there was no difference in rate-pressure products between the placebo and nifedipine GITS periods. In contrast, atenolol reduced heart rate, systolic blood pressure and rate-pressure product during exercise compared with placebo. Whereas left ventricular ejection fractions (by radionuclide angiocardiography) increased with exercise, the maximal increase was smaller with atenolol than with placebo and nifedipine. The net increase in left ventricular ejection fraction at the end of exercise was greater with nifedipine than with placebo or atenolol. Ambulatory electrocardiograms showed only a small number of ischemic events. Neither nifedipine GITS nor atenolol reduced the number of ischemic events or total duration of ST-segment deviations significantly. It is concluded that nifedipine GITS is as effective an antianginal agent as atenolol, but the hemodynamic effects of the 2 agents differ.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of atenolol, slow-release nifedipine, and their combination on respiratory gas exchange and exercise tolerance in stable effort angina

The effects of atenolol, nifedipine, and their combination on gas exchange and exercise tolerance were studied in 27 patients with effort angina and normal global ventricular function in an open-label and randomized cross-over trial. Symptom-limited semi-supine exercise tests using a ramp protocol (20 W/min) with simultaneous breath-by-breath analysis of gas exchange were carried out after a 4-day wash-out period and after consecutive 2-week treatment periods with atenolol (50 mg b.i.d.), slow-release nifedipine (20 mg b.i.d.), and their combination (b.i.d.). Exercise tolerance was not significantly higher with atenolol than with nifedipine [118(24) vs 113(23) W]. Combination therapy [120(23) W] was more effective than monotherapy with nifedipine (p less than 0.05) but produced no further increase in exercise tolerance over atenolol monotherapy. Maximum oxygen uptake was not significantly different among the treatments. In the range of light to moderate exercise, the slope of the VO2-workload regression line expressed as ml.min-1.W-1 was lower with atenolol than with nifedipine [8.64(1.59) vs 10.28(1.74), p less than 0.005] and intermediate with combination therapy [9.99(1.83)]. The intercept on the VO2 axis was higher with atenolol than with nifedipine [366(111) vs 299(113) ml.min-1, p less than 0.05]. A similar pattern of results was seen when the drug effects on the slope of the VCO2-workload relation were analyzed. VE was higher with nifedipine than with atenolol at all points of the regression analysis [greater than 30 W].(ABSTRACT TRUNCATED AT 250 WORDS)

Myocardial metabolic and hemodynamic effects of a sustained intravenous infusion of nifedipine with and without metoprolol in patients with unstable angina

We tested the usefulness of a sustained intravenous infusion of nifedipine and a combination of nifedipine and metoprolol in the early management of 14 patients with unstable angina pectoris. After a 24-hour run-in period, nifedipine was titrated in a stepwise fashion (mean dose 27 +/- 7 micrograms/min). After nifedipine treatment coronary blood flow increased from 150 +/- 66 to 183 +/- 74 ml/min (p less than 0.05), whereas double product, myocardial oxygen consumption, and both arterial and coronary sinus (nor)epinephrine levels were unchanged. Myocardial lactate uptake increased from 3.4 +/- 26.1 to 31.3 +/- 26.6 mumol/min (p less than 0.005) and free fatty acid uptake from 7.2 +/- 22.1 to 34.5 +/- 33.7 mumol/min (p less than 0.05). A small nonsignificant improvement in amino acid metabolism was observed. Metoprolol was added in seven patients and led to a decrease in double product (-2.2 +/- 1.6 x 10(3); p less than 0.01) and myocardial oxygen consumption (-3.2 +/- 3.8 ml/min; p less than 0.05). The lactate uptake/oxygen uptake ratio increased by 18% after metoprolol (p = NS). The number of episodes of chest pain decreased from 2.4 +/- 1.1/24 hours to 0.1 +/- 0.2 in the nifedipine group and from 2.9 +/- 1.1/24 hours to 0.3 +/- 0.5 in the nifedipine plus metoprolol group (both p less than 0.01). We conclude that in the acute phase of unstable angina, intravenous nifedipine can be carefully titrated to improve coronary blood flow and oxidative metabolism. The addition of metoprolol is also associated with a reduction in myocardial oxygen demand. This treatment results in significant hemodynamic stability.

Coronary vasomotor tone in large epicardial coronary arteries with special emphasis on beta-adrenergic vasomotion, effects of beta-blockade

Changes in coronary vasomotor tone of large epicardial coronary arteries today can be assessed quite accurately by exact measurements of coronary diameters applying computer assisted systems. The effect of various vasodilators (nitrates, calcium antagonists, EDRF-dependent compounds) was tested in this way. It appears that normal coronary artery segments reach a maximum of dilator reserve with an increase of luminal diameter of approximately 30-40%; different patterns of kinetics were, however, encountered. beta-Blocking agents, both non-selective (propranolol) and selective (atenolol), were found to lead to a gradual vasoconstriction, i.e., a decrease in diameter by approximately 20-25% over 20 min, an effect which is overcome by nitrates. New beta-blocking compounds with vasodilator properties, such as celiprolol, show no constriction. The vasoconstrictor effect of propranolol and atenolol may not only be due to the decrease of flow following the drop in myocardial oxygen consumption, but could also reflect an unopposed alpha-adrenergic tone. The clinical aspects of this observation are discussed.

Increased coronary tone in exertional angina: the beneficial effects of calcium antagonists

Coronary vasoconstriction may play a relevant role in the pathogenesis of exercise-induced myocardial ischemia, not only in patients with Prinzmetal's angina, but also in patients with chronic stable angina. In these patients the use of calcium antagonists, namely, dihydropyridine derivatives, may be beneficial. Hyperventilation is a simple and sensitive test to discriminate patients with effort angina who will improve their exercise capacity after administration of these drugs.

Acute effects of nifedipine versus isosorbide dinitrate on exercise tolerance in patients with isolated coronary artery occlusion and collaterals

The acute effects of slow-release nifedipine and isosorbide dinitrate on exercise tolerance were compared in nine patients with isolated total coronary artery occlusion showing retrograde filling via collaterals. All patients had a reproducible positive exercise stress test off medication before the study. Each patient was randomized to 10 mg slow-release nifedipine and 5 mg isosorbide dinitrate in a single-blind, cross-over study. The exercise stress test was performed 30 minutes after drug administration. After nifedipine, three patients had a negative exercise stress test, whereas the test was negative after isosorbide dinitrate only in one patient. A significantly higher exercise tolerance was detected at peak exercise after nifedipine than after isosorbide dinitrate, as shown by a longer exercise time (380 +/- 44 vs. 295 +/- 41 seconds, p less than 0.001), a more increased maximum work load (355 +/- 89 vs. 255 +/- 55 W x min, p less than 0.02), and a higher rate-pressure product (30,300 +/- 2,500 vs. 26,100 +/- 2,700, p less than 0.01). In conclusion, these results seem to suggest that nifedipine may have a vasomotor effect on collaterals, since it elevated the threshold of ischemia more than isosorbide dinitrate did in patients with isolated coronary artery occlusion, showing retrograde filling via collaterals.

Propionyl carnitine in stable effort angina

The aim of this study was to investigate the anti-ischemic activity of propionyl carnitine (PC) in 18 informed, volunteer male patients, aged 37-70, suffering from a typical stable effort angina. The study design was randomized, balanced, crossover, and double blinded. The study lasted 75 days. In the first 15 days of washout the patients performed two maximal symptom-limited bicycle tests to verify the repeatability of the parameters examined. Then one group received PC for 30 days 500 mg three times a day, and the other group received placebo (PL) three times a day. At the end of 30 days the groups exchanged treatments. At the end of each period, 2 hours after the last oral administration, the patients performed a maximal symptom-limited bicycle exercise test with increased loads of 10 watts/min. No significant differences were observed between the two tests performed during the wash-out period, for a 1 mm ST-segment depression time, for the time to the end of exercise, and for the rate x pressure product at the same experimental time. The oral administration of PC in coronary patients increased both the 1 mm ST-segment depression time and the time to the end of exercise. Furthermore, the drug reduced the ischemic depression of ST at maximal common work and at maximal work. After PC, the rate x pressure product was not significantly different in relation to placebo at submaximal and maximal exercise. Thus PC seems to have an antiischemiclike effect, probably related to its metabolic activity.

Rest and exercise cardiovascular effects of terazosin in congestive heart failure

This study investigated the acute effects of the alpha 1 antagonist terazosin on myocardial circulatory responses at rest and during exercise. Ten patients with congestive heart failure (class III and IV) underwent hemodynamic evaluation before and after a 5-mg oral dose of terazosin. At rest and during exercise, terazosin significantly decreased pulmonary capillary wedge pressure, systemic vascular resistance and mean arterial pressure while cardiac index increased. Stroke volume index increased (p less than 0.01) during exercise while left ventricular stroke work index remained unchanged in both experimental conditions. Terazosin administration significantly decreased both rest and exercise myocardial oxygen consumption while exercise coronary sinus oxygen content increased and arterial-coronary sinus oxygen difference diminished (p less than 0.05). Parallel with these changes, alpha blockade decreased the ratio of coronary blood flow to total cardiac output. Coronary vascular resistance remained unaltered with alpha blockade both at rest and during exercise. Coronary blood flow tended to diminish with decreased myocardial oxygen demand. Alpha 1 blockade induces systemic vasodilation and improves myocardial circulatory parameters without inducing coronary dilation or altering metabolic autoregulation.

[Changes in myocardial metabolism induced by drugs used during intensive care]

More and more patients with coronary heart disease (CAD) are admitted to intensive care units. The drugs used to treat these patients have various effects on the myocardium which must be known in order to avoid worsening the CAD. This review examines the metabolic effects on the myocardium of the most commonly used drugs in intensive care. The physiology of myocardial oxygen supply is first recalled with regard to the coronary circulation, myocardial oxygen extraction and consumption. Digitalis glycosides do not affect the coronary circulation, but the decrease myocardial oxygen consumption in patients with heart failure, mainly by lowering heart rate. Dihydropyridine calcium blockers (nifedipine, nicardipine) increase coronary blood flow, despite a decrease in arterial blood pressure. Their effects on myocardial oxygen consumption are mediated by a sympathetic reflex. Verapamil decreases the heart rate and myocardial inotropism, and is responsible for coronary vasodilation. The result is a decrease in myocardial oxygen consumption. Diltiazem and bepridil have almost similar effects: they decrease myocardial oxygen consumption and increase blood supply to the heart. It has been recently shown that verapamil was the most depressant calcium channel blocking agent, and that it resulted in the most important decrease in myocardial metabolism. Beta-blocking agents decrease myocardial metabolism, except those with an important intrinsic sympathomimetic activity, such as pindolol. Amiodarone can be considered as an alpha and beta blocking drug: its main effect is to counteract the effects of endogenous catecholamines on myocardial metabolism. The sympathomimetic amines (noradrenaline, adrenaline, isoprenaline, dopamine, dobutamine) increase, to different extents, myocardial oxygen consumption. Vasodilators, such as the nitrates or sodium nitroprusside, decrease cardiac filling pressures, and increase myocardial blood flow, thus lowering myocardial oxygen consumption. Phosphodiesterase inhibitors (amrinone, enoximone) have both an inotropic and a vasodilating effect. They decrease cardiac afterload, and increase blood supply to the myocardium; this compensates for the increase in myocardial oxygen consumption due to the increase in myocardial contractility. Because all the drugs used in intensive care have different effects on myocardial metabolism, their reasoned use should avoid an inappropriate increase in oxygen demand.

Nitrates: why and how should they be used today? Current status of the clinical usefulness of nitroglycerin, isosorbide dinitrate and isosorbide-5-mononitrate

Nitrates are highly effective both in terminating acute attacks of angina pectoris and in the prophylaxis of symptomatic and asymptomatic myocardial ischemia. Preload reduction by venodilatation is the prevailing mechanism of nitrates in patients with chronic stable angina and is the unique feature distinguishing them from beta and calcium-channel blockers. Nitrates dilate coronary arteries not only in pre- and poststenotic vessels, but also in eccentric lesions. In patients with endothelial dysfunction, nitrates seem to be the physiological substitute for endothelium-derived relaxing factor. During the past decade, however, there has been substantial evidence of a clinically relevant loss of the anti-ischemic effects ("nitrate tolerance"). Many studies with oral dosing of isosorbide dinitrate or isosorbide-5-mononitrate at least three times daily have proven nitrate tolerance in patients with coronary artery disease and/or congestive heart failure. Complete loss of anti-ischemic effects after repetitive, continuous patch attachments has also been found. As we first showed in 1983, intermittent therapy with once-daily ingestion of high-dose sustained-release isosorbide dinitrate was successful in preventing the development of tolerance. Similarly, tolerance to isosorbide-5-mononitrate also does not develop when it is ingested once daily. It is now generally accepted that a daily low-nitrate interval is required to prevent tolerance development. Although the minimal patch-free interval required to prevent tolerance needs further investigation, a 12-h patch-free interval should prevent tolerance in most patients. The prolonged duration of action of once-daily high-dosage administration of sustained-release formulations, the improved patient compliance with a single daily administration, and the increased likelihood of maximal anti-ischemic effects are important reasons for recommending high single daily doses of isosorbide dinitrate or isosorbide-5-mononitrate.

Beta-adrenoceptor antagonists plus nifedipine in the treatment of chronic stable angina pectoris

The antianginal effects of beta-adrenoceptor antagonists are achieved by a reduction in myocardial oxygen demand. This is a rational approach to treatment in patients whose angina is caused by a fixed stenosis. However, dynamic coronary vasospasm is an important factor in patients with chronic stable angina. Nifedipine increases myocardial oxygen supply by reducing coronary vascular tone and is a logical approach to treatment in these patients. For monotherapy of angina, nifedipine is less effective than the beta-adrenoceptor antagonists, but the combination has additive effects in reducing the frequency of anginal episodes and improving exercise tolerance. Plasma concentrations of nifedipine are closely related to clinical efficacy, and the variable first-pass metabolism of the drug leads to wide interindividual differences in peak concentrations and duration of action. Increasing the size of individual doses of nifedipine carries a risk of enhanced side effects due to high peak plasma concentrations. Optimal treatment may be more appropriately achieved in some patients by a slow release formulation, but with an increased frequency of administration.

Comparison of antianginal efficacies and exercise hemodynamic effects of nifedipine and diltiazem in stable angina pectoris

The antianginal efficacies of nifedipine (40 to 120 mg/day) and diltiazem (120 to 360 mg/day) were studied in 21 normotensive patients with chronic stable angina pectoris, using a randomized, double-blind, crossover design. Patients received each agent titrated to maximum tolerated doses for 6 weeks, after a 2-week placebo baseline period. The maximum tolerated dose for nifedipine was 72 +/- 8 (standard error) mg/day and for diltiazem 297 +/- 20 mg/day. Two patients discontinued nifedipine early because of side effects. Duration of symptom-limited treadmill exercise was longer during the nifedipine (556 +/- 43 seconds) and diltiazem periods (546 +/- 39 seconds) compared with placebo baseline (474 +/- 41 seconds, p less than 0.02). Compared with placebo, nifedipine caused a significant increase in heart rate both at rest standing and at peak exercise. Nifedipine decreased resting systolic blood pressure but had no effect at peak exercise. In contrast, diltiazem caused a significant decrease in heart rate at rest but had no effect on blood pressure at rest or at peak exercise. Thus, nifedipine and diltiazem have differential effects on heart rate and systolic blood pressure suggesting different modes of action. However, despite the increase in exercise duration, neither nifedipine nor diltiazem increased the heart rate-systolic pressure product during maximum exercise. This suggests that the antianginal effects of the 2 agents probably are mediated via reduction of myocardial oxygen demand at submaximal exercise. In addition, diltiazem appears to be better tolerated than nifedipine.

Different vasomotor action of nifedipine on dynamic coronary obstructions and therapeutic response in effort and prinzmetal angina

Variations induced by nifedipine (10 mg sublingually) in the residual lumen diameter of significant (greater than 50%) coronary lesions were assessed angiographically in 58 patients with effort angina (group 1) and in 19 patients with Prinzmetal angina (group 2). A relationship was sought between these acute variations of the stenotic lumen and the clinical response to treatment with the same drug (20 mg four times daily). Treatment efficacy was evaluated with exercise testing in group 1 and Holter monitoring in group 2. In group 1 the residual segment of stenotic diameter showed an increase, decrease, or no change with the calcium antagonist. Nifedipine failed to improve 40% of the cases (21% unchanged and 19% worsened) in group 1. In the same group of patients, the responses to exercise tests were dissociated from the acute vasomotor pattern. Changes in the pressure-rate product also did not explain the clinical results. In group 2 the majority of lesions had compliant portions, which invariably reacted to nifedipine with dilatation. All patients with the Prinzmetal form had relief of the anginal episodes with treatment. These data suggest that the therapeutic efficacy of nifedipine in classic effort angina probably is the net result of influences on the myocardial oxygen consumption and supply, and the acute coronary vasomotor pattern does not allow to predict the clinical response. Stenotic lesions in the Prinzmetal form possess a distinct sensitivity to the relaxant action of calcium channel blockade, which reasonably explains the highly positive response to treatment.

Effects of vasodilators on the coronary circulation in congestive heart failure

Pressure or volume overload of the myocardium increases the wall stress, particularly of the subendocardium, and leads to hypertrophy. Even though cardiac hypertrophy is viewed as a beneficial compensatory process that normalizes wall stress, the increased muscle mass carries with it the need of increased blood supply. Overall flow per unit mass is similar at rest in hypertrophic and normal hearts but a reduction of flow to the subendocardium and an increase in minimal coronary vascular resistance have been described. Thus, the potential exists for a vasodilator-induced steal mechanism shunting blood away from potentially ischemic areas. Angiotensin-converting enzyme inhibitors reduced myocardial oxygen consumption and coronary blood flow in parallel manner in some studies, indicating preserved coronary autoregulation, but there is also some evidence of a coronary vasodilator effect. Calcium antagonists reduce coronary vascular resistance and improve the myocardial demand-supply ratio, but the clinical usefulness of the newer compounds with supposedly little or no negative inotropic effects remains to be established. Hydralazine improved the myocardial oxygen demand-supply ratio in patients with dilated cardiomyopathy, but metabolic function may deteriorate more often after hydralazine than after angiotensin-converting enzyme inhibitors in patients with coronary heart disease. Similar observations have been made using alpha-adrenergic blockers. Although progress has been made in the understanding of the coronary circulation and the influence of vasodilators in congestive heart failure, many questions await clarification using refined or new methodology.

Coronary vasomotor and clinical effects of nifedipine in effort, mixed and Prinzmental angina

Changes induced by nifedipine (10 mg s.l.) in the residual lumen diameter of significant (greater than 50%) coronary lesions were assessed angiographically in 69 patients with effort angina (Group 1), in 22 patients with mixed angina (Group 2), and in 14 patients with Prinzmental angina (Group 3). These changes were related to the clinical response to treatment with the same drug (diary records, exercise testing, Holter monitoring). In Groups 1 and 2 segments of stenotic vessels showed either increase, decrease or no change in diameter with the calcium antagonist; in Group 3 the majority of the vessels showed compliant portions which invariably responded with dilatation. Nifedipine failed to improve cases with exertional (21% unchanged, 19% worsened) and mixed (41% exacerbated) forms; all patients with the Prinzmental form had relief of the anginal episodes. In Group 1, the response to exercise tests were dissociated from the acute vasomotor pattern and the pressure-rate product failed to explain the clinical results. Fifty-two percent of the patients in Group 2 showed significant acute widening of critical stenoses as well as obvious improvement; patients in this group who did worse with treatment had reacted to nifedipine with narrowing of their critical stenoses. These data suggest that: the response to nifedipine of classic effort angina is probably the net result of an interaction of changes in myocardial oxygen consumption and supply; coronary vasomotion has a role in mixed angina and influences of nifedipine may be either favorable or unfavorable; stenotic lesions in the Prinzmental form are quite sensitive to the relaxant action of calcium blockade and this probably represents a background to the highly positive clinical response to treatment.

Changes in myocardial ischaemia during isosorbide dinitrate or indoramin therapy in patients with stable angina using relations between the ST segment and heart rate

The effect of isosorbide dinitrate or indoramin on myocardial ischaemia was examined in patients with stable angina pectoris. In a prospective trial, randomization resulted in 8 and 9 patients, respectively, given isosorbide dinitrate in a dose of 30-90 mg daily, and indoramin in a dose of 75-225 mg daily; 2 of these patients were serially examined during the two types of therapy. Changes in myocardial ischaemia were assessed by exercise testing using 12 standard electrocardiographic leads and a bipolar lead CM5. Individual and group comparisons showed that isosorbide dinitrate resulted in an increase in ST segment depression, the maximal ST/heart rate slope and the ratio of net ST segment depression to increases in heart rate (at least P less than 0.01). In contrast, with indoramin therapy there were no significant changes in these indices. The results in these patients suggest that isosorbide dinitrate leads more consistently to increases in the severity of myocardial ischaemia than indoramin, although this effect on ischaemia is apparently less than the benefit of these agents on exercise performance.

The combination of antianginal drugs: effects and indications

Today, three classes of drugs, all acting differently on the myocardium, the coronary circulation, and the peripheral circulation, that is, on the determinants for myocardial oxygen consumption (heart rate, contractility, and wall tension), are at the physician's disposition for anti-ischemic medical treatment: nitrates, beta-receptor blocking agents and Ca antagonists. All three drugs have been proven to exhibit a marked antianginal effect when given alone, as demonstrated both by an improvement in exercise performance as well as in perfusion and a significant decrease in symptomatic and silent ischemic episodes. Treatment should cover the total ischemic burden, which can be assessed today more accurately by Holter monitoring than with exercise tests alone. It has been shown in patients with stable angina that the majority of ischemic episodes are silent (over 75%); therefore, the question arose as to whether medical anti-ischemic treatment should aim at the prevention not only of symptomatic, but also of silent episodes. Furthermore, ischemia was revealed to be not only a marker for the presence of high-grade life-threatening obstructions, but also to have prognostic implications, not only in symptomatic, but also in asymptomatic episodes. In addition, ischemia can lead to life-threatening arrhythmia and irreversible myocardial damage, especially localized fibrosis. To what extent this is prevented by vigorous anti-ischemic treatment is still unanswered; however, as pathophysiologically symptomatic and asymptomatic ischemic episodes behave similarly, the latter should be included in treatment. The combinations of drugs, especially of nitrates and beta blockers, Ca antagonists and beta blockers, and also nitrates and Ca antagonists result in a further improvement in exercise performance and a reduction in ischemic episodes, allow the dose to be reduced, and minimize side effects. In addition, as is indicated from their hemodynamics, in special clinical situations, combinations might be preferable. Whether treatment should primarily reduce sympathetic drive or, rather, be directed towards vasodilation depends on the type of angina and the individual need. Hence, combining drugs in treating angina pectoris represents a true therapeutic challenge for the physician.

Nifedipine in acute myocardial infarction: an assessment of left ventricular function, infarct size, and infarct expansion. A double blind, randomised, placebo controlled trial

The influence of nifedipine on left ventricular ejection fraction, infarct size, and infarct expansion was studied in a prospective, double blind, randomised, placebo controlled trial in 132 patients with low risk acute myocardial infarction of less than 12 hours duration, defined by an initial left ventricular ejection fraction greater than 35% and clinical Killip class of less than or equal to II. Sixty four patients were assigned to nifedipine 120 mg/day and 68 to placebo. Treatment was started on average (SEM) 8.0 (0.2) hours after onset of pain and continued for six weeks. Gated blood pool scans, thallium scans, and cross sectional echocardiograms were performed before treatment and at 10 days. There were no significant differences between the two groups in age, sex, cardiac risk factors, or use of other medications. Mean (SEM) global left ventricular ejection fraction was not different before treatment (nifedipine group 53 (2%), placebo group 55 (2%) and did not differ at 10 days (nifedipine group 54 (2%), placebo group 52 (2%). There were also no differences in regional wall motion or regional ejection fractions. Thallium defects quantified by computer analysis were similar in both groups before treatment (nifedipine 7.8 (0.7), placebo 7.9 (0.7)) and at 10 days (nifedipine 5.3 (0.7) placebo 5.3 (0.7)). In the subgroup of patients with transmural infarction who had good quality echocardiograms and serial studies (n = 30), there was no difference in mean (SEM) baseline infarct segment lengths between the two groups (nifedipine 70 (4) mm, placebo 65 (4) mm); however, the nifedipine group demonstrated no significant change in infarct segment length between the initial and 10 day studies ( + 0.6 (3) mm) while there was a significant increase in the infarct segment length in the placebo group (+ 7.8 (4) mm). The infarct segment length increased by >/= 1 cm in seven (47%) placebo patients but in only one (7%) nifedipine patient. The nifedipine group had a significant initial 10% decrease in mean arterial pressure whereas there was no change in the in the placebo group; this blood pressure difference persisted for 10 days. Thus although the early administration of nifedipine has no detectable effect on clinical outcome and infarction size, it may reduce early infarct expansion via an afterload reduction mechanism in patients with transmural infarction. These initial results must be interpreted with caution and need to be confirmed in a larger trial.

Intravenous nifedipine for control of hypertension in patients after coronary artery bypass graft surgery

A study was undertaken to assess the use of intravenous nifedipine in controlling hypertension in patients following coronary artery surgery. A combined hemodynamic and metabolic assessment was carried out in 15 patients on data recorded at six sequential time intervals: (1) baseline, (2) control of blood pressure, (3) 30 minutes after control of blood pressure, (4) 1.5 hours after control of blood pressure, (5) 3.5 hours after control of blood pressure, and (6) 30 minutes after discontinuing nifedipine. Coronary sinus and great cardiac vein blood flows were measured by the continuous thermodilution technique using the Baim coronary sinus flow catheter. Intravenous nifedipine was run initially at an average rate of 1.82 microg/kg/min. It took an average time of 12 minutes to lower the blood pressure to less than 130 mmHg systolic. There were highly significant decreases in systolic, mean, and diastolic blood pressures (P < .001), associated with significant decreases in systemic vascular resistance (P < .001) and left ventricular stroke work index (P < .05). There was an increase in cardiac output at 30 and 90 minutes of infusion (P < .05), and the stroke volume was increased 90 minutes after starting nifedipine (P < .05). The increase in heart rate was not significant. There was no significant effect on conduction times as measured by PR and QRS intervals on the ECG. However, the QTc interval was decreased after 3.5 hours (P < .05). There was an increase in right atrial pressure at 90 minutes and again 30 minutes after stopping nifedipine. (P < .05). The pulmonary artery pressure also was increased after stopping the infusion (P < .05). The pulmonary capillary wedge pressure, pulmonary vascular resistance, and right ventricular stroke work index remained unchanged. Coronary sinus and great cardiac vein flows were maintained despite a decrease in perfusion pressure, suggesting that nifedipine is a potent coronary vasodilator. Indeed, coronary vascular resistance was significantly decreased (P < .05). Myocardial oxygen consumption remained unchanged. The lactate extraction indicated that myocardial metabolism remained aerobic regionally and globally. Thus, the results suggest that blood pressure was easy to control and that there were no adverse effects on atrioventricular conduction, cardiac performance, regional and global myocardial oxygen utilization, or lactate extraction.

Cardiac nuclear medicine, present status, future hopes as seen from the view of a cardiologist

The present techniques of nuclear medicine that are used in cardiology are critically evaluated. They are used mainly for the assessment of coronary circulation (measurement of regional flow and perfusion), on the determination of left ventricular muscle function (radionuclear ventriculography) and on the study of cardiac metabolism. The last-mentioned technique is unique insofar as (except for magnetic resonance imaging) there is no other method available to analyse myocardial metabolism noninvasively in living man. Of immense practical importance is the diagnosis and quantitation of the abnormal coronary flow and perfusion, as coronary artery disease is one of the major diseases of the Western world. Finally, the value of nuclear imaging techniques is compared with that of other nonnuclear methods. In present-day medicine, with its increasingly high costs, the value of nuclear techniques must be assessed very carefully.

Nifedipine and angina pectoris. Short-term changes in quantitative coronary angiography with nifedipine and clinical response to treatment in effort-induced, mixed, and spontaneous angina pectoris

Changes induced by nifedipine (10 mg sublingually) in the residual luminal diameter of significant (greater than 50 percent) coronary lesions were assessed angiographically in 69 patients with effort-induced angina (group 1), in 22 patients with mixed angina (group 2), and in 14 patients with Prinzmetal's angina (group 3). These changes were related to the clinical response to treatment with the same drug, as evaluated through diary records and Holter monitoring in the mixed (spontaneous component) and Prinzmetal forms and through exercise testing in effort-induced and mixed (effort-associated component) angina. In groups 1 and 2, segments of stenotic vessels showed either an increase or decrease or no change in diameter with the calcium antagonist; in group 3, the majority of the lesions had compliant portions which invariably responded with dilatation. Nifedipine failed to improve cases with exertional (20 percent [14/69] unchanged; 19 percent [13/69] worsened) and mixed (41 percent [9/22] exacerbated) forms; 100 percent of the 14 patients with the Prinzmetal form had relief of the anginal episodes. In group 1, the response to exercise tests was dissociated from the short-term vasomotor pattern, and the pressure-rate product failed to explain the clinical results. Forty-five percent (ten) of the patients in group 2 showed significant short-term widening of critical stenoses, as well as obvious improvement; patients who did worse with treatment in this group had reacted to nifedipine with narrowing of critical stenoses. These data suggest that the response to nifedipine of classic effort-induced angina is probably the net result of an interaction of changes in myocardial oxygen consumption and supply; coronary vasomotion has a role in mixed angina, and influences of nifedipine may be either favorable or unfavorable; stenotic lesions in the Prinzmetal form are quite sensitive to the relaxant action of calcium blockade, and this probably represents a background to the highly positive clinical response to treatment.

Beta-blockers and calcium antagonists in angina pectoris. The potential role of combination therapy

In coronary heart disease, beta-blockers are beneficial because they limit the increase in heart rate and blood pressure during exercise, and calcium antagonists are useful because they reduce myocardial oxygen demand. Many different pharmacological combinations of a beta-blocker and a calcium antagonist are possible, and beta-blockade may ameliorate reflex tachycardia induced by peripheral vasodilatation due to calcium antagonists, therefore enhancing the benefit. Studies have shown that combination therapy with propranolol and nifedipine, verapamil or diltiazem has greater antianginal efficacy based on symptomatic and objective assessment than either agent alone. A similar result has been reported for nifedipine or verapamil combined with atenolol. In combination, atenolol and nifedipine did not depress cardiac output or change the left ventricular ejection fraction (LVEF) at rest. During exercise atenolol alone resulted in a reduced LVEF response in most patients but the combination did not adversely affect left ventricular function. Nifedipine alone did not significantly change LVEF. When verapamil was combined with atenolol, resting ejection fraction fell, indicating a deterioration in cardiac function. Nifedipine and propranolol combined do not change heart rate significantly. Verapamil and atenolol both reduce resting heart rate and their combination has a greater effect; a combination of propranolol and diltiazem also reduces heart rate to a similar extent. Caution is therefore warranted when prescribing the latter 2 combinations. An increase in side effects can be expected with combination regimens compared with monotherapy; but with the nifedipine-atenolol combination the calcium antagonist can alleviate beta-blocker-induced effects by its vasodilator effect, and beta-blockers may ameliorate nifedipine-induced palpitations and flushing.(ABSTRACT TRUNCATED AT 250 WORDS)

[Calcium inhibitors and anesthesia]

Calcium blockers (CB) are routinely used. This could lead to possible interference with anaesthetic drugs. CB prevent calcium from entering the cell by inhibiting the slow voltage-dependent calcium channels. They act mostly on heart and smooth muscle. Of all the possible indications, the three that are confirmed are coronary heart disease, arterial hypertension and supraventricular rhythm disturbances. Most of the work published and the cases reported concerns interactions between CB and halogenated anaesthetic agents; the latter's actions on the heart depend on cellular calcium exchange. Also, the cardiovascular effects of these anaesthetics are similar to that of CB. Experimentally, halothane and enflurane have direct cardiac inhibitory effects similar to verapamil and diltiazem, whereas isoflurane's properties seem closer to the dihydropyridines (nifedipine and nicardipine). Giving verapamil or diltiazem increases the number of sino-atrial and atrio-ventricular blocks when using a halogenated agent. Clinically, interpreting the effects of CB during anaesthetic induction is difficult because of the pathology (coronary heart disease, cardiac failure), the other drugs (beta-blockers and nitrates) and the type of anaesthesia (emergency or elective). Interactions can give rise to anything from a severe cardiovascular collapse, requiring catecholamines, to a mild fall in blood pressure which responds well to plasma expansion, or even no effect on blood pressure. Rebound is seen on stopping CB in patients with coronary heart disease or arterial hypertension; stopping them before surgery does not therefore seem justified. However, extreme care must be taken when using halogenated agents for patients under treatment with CB and/or beta-blockers. A wary anaesthetist will be able to adapt the technique to the patient. It has been suggested that CB could be used to treat preoperatively myocardial ischaemia (diltiazem), hypertensive crises (nifedipine, nicardipine) and ventricular rhythm disturbances (verapamil); this must be done with caution, the patient being closely monitored (haemodynamic and electrocardiographic monitoring). Postoperatively, intranasal nifedipine, continuous intravenous nicardipine or diltiazem have been used to treat increases in arterial blood pressure during recovery and to adapt the cardiovascular system to the increased metabolic needs. Here again, close patient monitoring is essential. In any case, treatment with CB which has been stopped should be started up again as soon as possible.

Cardiac hypertrophy in hypertension. Repolarization abnormalities elicited by rapid lowering of pressure

In hypertension, coronary flow is augmented and oxygen balance is adequate despite an increase in coronary resistance. For the maintenance of flow in the presence of and after regression of ventricular hypertrophy, the ratio of pressure and ventricular mass must remain normal. Coronary reserve would be altered if treatment normalized pressure but not ventricular mass or if pressure were lowered too fast. We investigated 42 patients with primary hypertension. In 28 (Group I) left ventricular mass index (by ultrasound) was within the mean value +2 SD (96 + 38 g/m2) of 145 controls and exceeded these values in the remaining 14 patients (Group 2). The diastolic pressure was lowered rapidly to between 85 and 90 mm Hg with two potent vasodilators, nifedipine (sublingually) and nitroprusside, while a 12-lead electrocardiogram was recorded continuously. During both tests, seven patients in Group 2 (responders) showed inversion of normal T waves, in lead I, aVL, and V3-6. These changes waxed and waned in parallel with the pressure fall and recovery and were not attributable to alterations in adrenergic tone, conduction disturbances, variations, or group differences in the QRS axis, QTc interval, heart rate, left ventricular fractional shortening, wall stress, rate of dimension increase in early diastole, or isovolumic relaxation. A ""steal phenomenon'' or passive collapse in compliant coronary lesions during vasodilatation seems unlikely; in fact, patients were free from coronary symptoms, and the electrocardiographic alterations occurred only in seven patients in Group 2, who had a greater left ventricular mass index and required a larger pressure drop to return the diastolic pressure to normal.(ABSTRACT TRUNCATED AT 250 WORDS)

Total ischemic burden: effect of vasoactive agents

Treatment of the total ischemic burden is dependent on adequate documentation of both painful and painless episodes of myocardial ischemia, an understanding of the pathophysiologic mechanisms involved, and knowledge of prognosis for affected patients. Because a vasoconstrictive component appears to be an important element in the genesis of many episodes of myocardial ischemia, those vasoactive drugs that produce increased flow in the coronary circulation should be clinically useful. Nitrates and calcium blockers--especially nifedipine--have been found to be particularly valuable in this regard in both experimental and clinical trials.

Comparison of nifedipine and isosorbide dinitrate when added to maximal propranolol therapy in stable angina pectoris

A study was performed to compare isosorbide dinitrate and nifedipine as adjunctive therapy in 14 patients with coronary artery disease and stable angina pectoris taking maximal beta-blocking drugs. Drug titration phases ensured maximal therapy of propranolol, isosorbide or nifedipine. The combination of nifedipine and propranolol was more effective than the combination of isosorbide and propranolol in reducing angina and increasing exercise capacity (323 vs 416 seconds, p less than 0.005) during exercise treadmill testing. Nifedipine produced a greater reduction in systolic blood pressure at submaximal exercise than isosorbide. Global and regional ejection fraction at rest and exercise was assessed with radionuclide ventriculography. The substitution of nifedipine for isosorbide depressed the global ejection fraction at rest (0.61 to 0.56 p less than 0.05) and produced a slight improvement in exercise ejection fraction (0.47 to 0.51, difference not significant). The decrease in ejection fraction from rest to exercise was 0.14 to 0.04 with nifedipine (p less than 0.005). The benefit of nifedipine compared with isosorbide occurred in regions with marked exercise-induced ischemia. In patients treated with maximal beta-blocking therapy, nifedipine is an effective alternative to isosorbide as a combination agent with propranolol. The salutary effects of nifedipine included afterload reduction with exercise and possible improvements in coronary blood supply.

Calcium antagonists for chronic stable angina pectoris

Stable angina pectoris classically occurs on exertion or in response to other well-defined stress, and can be treated successfully, both in regard to symptoms and ability to undertake more exertion, with available calcium antagonists. Numerous reports suggest that response to calcium antagonists is similar to that with beta-adrenergic blockers, although the latter tend to show somewhat greater efficacy. Advantages in favor of calcium antagonists include the relative freedom from side effects that may occur with beta-adrenergic antagonists; the 2 types of substances can be combined usefully and given to the vast majority of patients requiring medication for angina. Left ventricular failure is a relative contraindication to both calcium antagonists and beta-adrenergic blockers, and thus to the combination. With calcium antagonists, however, the negative inotropic effects are often balanced by the associated peripheral vasodilatation. Where medical management of chronic stable angina is considered, calcium antagonists offer a reasonable alternative to beta blockers, and the use of the combination is highly effective, more so than either substance alone.

Isosorbide-5-mononitrate and isosorbide dinitrate retard in the treatment of coronary heart disease: a multi-centre study

A multi-centre study was carried out in 200 coronary patients to compare the efficacy and tolerance of isosorbide dinitrate retard (40 mg) and isosorbide-5-mononitrate (20 mg) with regard to the frequency of anginal attacks and consumption of sub-lingual (short acting) nitrates. After receiving treatment for 2 weeks with isosorbide dinitrate retard at a dosage of 2 or 3 tablets per day, only those patients continued the study who had a weekly average of 4 or more anginal attacks during this basal period. The selected patients were divided in 4 groups of 50 patients and received treatment for a further 4 weeks with either isosorbide dinitrate retard at a dosage of 2 tablets (Group D2) or 3 tablets (D3) per day or isosorbide-5-mononitrate at a dosage of 2 tablets (Group M2) or 3 tablets (Group M3) per day. A progressive improvement in symptoms was seen at the end of 2 and 4 weeks with both drugs. The greater therapeutic benefits were obtained in patients in Group M2; the greater difference was observed between Group M2 and D2 (p less than 0.01) and there were also significant differences (p less than 0.05) between Groups M2 and D3 and between Groups M3 and D3. Analysis of the results showed that the more frequently angina attacks had occurred during the basal period, the greater was therapeutic benefit obtained with isosorbide-5-mononitrate compared to isosorbide dinitrate retard at the end of the study. Heart rate at the end of the study showed a slight tendency to increase over initial levels in all groups. In contrast, systolic blood pressure decreased very significantly in all groups (p less than 0.001). Diastolic blood pressure also decreased in all groups but only to a highly significant degree in patients treated with isosorbide-5-mononitrate (p less than 0.001) and the two sub-groups M2 and M3 (p less than 0.005). In patients treated with isosorbide dinitrate retard, the reduction in diastolic pressure was only statistically significant when the 100 patients in the group were considered as a whole (p less than 0.05), while this was not the case for the two sub-groups D2 and D3. The most frequent side-effect was headache, which improved gradually. During treatment there was a progressive dissociation between reduction in the intensity and frequency of this adverse effect and the increasing anti-anginal action of the nitrates.

[Calcium antagonists in heart failure?]

Although beneficial acute hemodynamic effects of calcium antagonists in heart failure have been reported, their use in this setting is still controversial because of the negative inotropic effects produced by these agents. The direct actions of calcium antagonists, that is direct depression of myocardial contractility and coronary and peripheral vasodilation, are modulated by systemic hypotension-induced baroreceptor activation of autonomic reflexes. Thus, at clinically relevant dosages, the baroreceptor-mediated cardiac stimulatory effects may counterbalance or override the direct negative-inotropic effects, as usually observed with nifedipine or diltiazem. By contrast, with verapamil significant depression of contractility may occur. Newer calcium antagonists with higher vasoselectivity such as nisoldipine or felodipine may be particularly interesting in the setting of congestive heart failure because of pronounced arterial vasodilatation and their additional effects on coronary blood flow, LV-regional wall motion and diastolic function and peripheral blood flow distribution with negligible myocardial effects. Due to their marked vasodilatating properties, newer derivatives may be advantageous in the treatment of heart failure due to coronary artery disease and hypertension. Although limited data concerning long-term efficacy are available, preliminary studies suggest long-term benefit in selected patients. It appears that verapamil should not be used for vasodilator therapy of severe heart failure, since deterioration of LV function may occur.

Direct cardiac and peripheral vascular effects of intracoronary and intravenous nifedipine

The hemodynamic effects of a new parenteral formulation of nifedipine administered by the intravenous (1 mg) and intracoronary (IC) (0.1 and 0.2 mg) routes were studied in 10 patients with symptomatic coronary artery disease undergoing diagnostic right- and left-sided cardiac catheterization. Intravenous nifedipine (1 mg) reduced systemic vascular resistance by 34% (p less than 0.01), increased cardiac output by 28% (p less than 0.01) and decreased mean arterial pressure by 10% (p less than 0.01). It had less effect on peak positive dP/dt (-8% p less than 0.025) and on peak negative dP/dt (-15% p less than 0.01). Coronary blood flow increased 20% (p less than 0.025). In contrast, IC nifedipine (0.2 mg) increased coronary blood flow 46% (p less than 0.025), depressed contractility as assessed by peak positive dP/dt (-26% p less than 0.01) and prolonged diastolic relaxation time. The effect of 0.1 mg was similar but less pronounced. These data suggest that the primary therapeutic effect of nifedipine administered systemically to patients at rest results from an increase in coronary blood flow and, to a lesser extent, from afterload reduction; its myocardial depressant effects are small, transient and masked by reflex catecholamine release. IC nifedipine increases coronary blood flow, has a transient negative inotropic effect and prolongs relaxation. The relative importance of these myocardial effects in preventing myocardial ischemia is not known.

Left ventricular dysfunction induced by cold exposure in patients with systemic sclerosis

Raynaud's phenomenon and cardiac abnormalities are frequent in patients with systemic sclerosis. Radionuclide ventriculograms were obtained in 16 patients with Raynaud's phenomenon and systemic sclerosis or the related CREST syndrome and in 11 normal volunteers in order to evaluate changes in left ventricular function that might be induced by exposure to cold. Left ventricular regional wall motion abnormalities developed in nine of 16 patients during cooling compared with only one of 11 control subjects, despite a comparable rise in mean arterial pressure (p less than 0.02). The abnormalities occurred in seven of 11 patients with systemic sclerosis, one of four with CREST syndrome, and one with Raynaud's disease. To test the potential protective effect of nifedipine, radionuclide ventriculograms were then obtained during cooling after sublingual nifedipine (20 mg). Only five of 13 patients had wall motion abnormalities, and the severity of the abnormalities was significantly less than during the first cooling period (p = 0.03). Five of eight patients who had cold-induced wall motion abnormalities during the first cooling period had none after nifedipine, whereas two other patients demonstrated small abnormalities only during the second cooling period after treatment with nifedipine. It is concluded that cold induces segmental myocardial dysfunction in patients with systemic sclerosis and that nifedipine may blunt the severity of this abnormal response.

Calcium-channel blockers for combined angina pectoris and systemic hypertension

Calcium-channel blockers have been successfully used in the treatment of angina of effort and systemic hypertension. Many patients present with concomitant angina pectoris and hypertension. Controlled clinical trials demonstrate that the calcium-channel blockers are safe and effective as monotherapy in the treatment of these patients, and that their use compares favorably with that of propranolol. The effectiveness of these agents in hypertension appears to be primarily due to their ability to induce systemic vasodilation. Calcium-channel blockers have several therapeutic effects in angina pectoris. Beneficial actions on the major determinants of oxygen consumption, i.e. heart rate, blood pressure and contractility, are generally seen. The potent coronary vasodilating actions of these agents allow for increased coronary blood flow. Improvements in ventricular compliance, regression of left ventricular hypertrophy and cardioprotection appear to be additional effects of the calcium-channel blockers; their contribution to the drugs' overall therapeutic efficacy is presently being evaluated. Calcium-channel blockers are a welcome addition to drug regimens available for the management of patients with coexisting angina pectoris and hypertension.

Combination therapy with beta-adrenoceptor blockers and calcium antagonists

Verapamil and nifedipine enhance the hypotensive and anti-anginal effects of beta-adrenoceptor blocking drugs. The combination of beta-adrenoceptor blocking drugs with nifedipine may pose fewer safety problems than the combination with verapamil especially in ischaemic heart disease when left ventricular function is suspect. Verapamil as a single agent may be as effective as a beta-adrenoceptor blocking drug in angina and provide a suitable alternative. Careful supervision is required when verapamil is combined with beta-adrenoceptor blockers for both angina and hypertension but reported clinical problems in hypertension are few.

Double-blind crossover comparison of the antianginal effects of nifedipine and isosorbide dinitrate in patients with exertional angina receiving propranolol

A double-blind crossover study was performed on 27 patients with proved fixed coronary artery disease and stable angina pectoris. The study was designed to compare the relative efficacy of two combination therapies, nifedipine plus propranolol and isosorbide dinitrate plus propranolol, in terms of antianginal response and effect on exercise tolerance by evaluation of treadmill testing. The combination of nifedipine and propranolol was superior to the combination of isosorbide and propranolol in reducing the number of anginal attacks (p = 0.03), increasing total exercise time (p less than 0.02), increasing oxygen consumption achieved at end of exercise (p less than 0.03), increasing time to onset of pain (p = 0.003) and increasing oxygen consumption achieved at onset of pain (p = 0.003). Analysis of the rate-pressure products suggests that the difference in these results may be explained by the greater effect of nifedipine on afterload reduction. Although nitroglycerin consumption was reduced from baseline levels during combination nifedipine therapy (p less than 0.001), there was no statistical difference between nifedipine combination therapy and isosorbide combination therapy. In conclusion, although both combination therapies were superior to propranolol therapy alone, the combination of nifedipine and propranolol was more effective than the combination of isosorbide and propranolol in reducing the incidence of angina and improving exercise performance. Side effects were experienced at a similar frequency during both combination therapies.

Spectrum of acute hemodynamic effects of nifedipine in severe congestive heart failure

The acute hemodynamic effects of 20 to 50 mg of orally administered nifedipine were evaluated in 31 patients with severe chronic congestive heart failure (CHF) and the results were analyzed according to the response of the cardiac index (CI). Although the group mean value of CI increased significantly after nifedipine treatment (from 2.1 +/- 0.5 to 2.4 +/- 0.8 liters/min/m2, p less than 0.001), the individual response was variable. Twenty of the patients had 15% or greater increase in CI (group A) and 11 patients had less than a 15% increase or a decrease in CI (group B). Marked differences were also noted in the effects of nifedipine on other hemodynamic variables. Stroke volume increased 29 +/- 14% in group A and decreased 11 +/- 18% in group B (p less than 0.001). Systemic vascular resistance decreased 34 +/- 11% in group A (p less than 0.001) and increased slightly, 2 +/- 28%, in group B. Left ventricular (LV) stroke work index increased 11 +/- 19% in group A (p less than 0.001) and decreased markedly in Group B (21 +/- 20%). Six group B patients had a substantial worsening (20% or more) of one or more hemodynamic measurements, including CI, stroke volume index, LV stroke work index and mean pulmonary artery wedge pressure. A comparison of control hemodynamic values at rest, LV ejection fraction, associated coronary artery disease, nifedipine dose, and concomitant diuretic therapy revealed no significant differences between the 2 groups. This study confirms, in a large group of patients with severe CHF, the variable hemodynamic effects of nifedipine therapy.(ABSTRACT TRUNCATED AT 250 WORDS)