Calcium antagonists for Prinzmetal's variant angina, unstable angina and silent myocardial ischemia: therapeutic tool and probe for identification of pathophysiologic mechanisms

Salvianolic Acid B Inhibits Ferroptosis and Apoptosis during Myocardial Ischemia/Reperfusion Injury via Decreasing the Ubiquitin-Proteasome Degradation of GPX4 and the ROS-JNK/MAPK Pathways

Myocardial ischemia/reperfusion injury (MIRI) is related to ferroptosis and apoptosis elicited by reactive oxygen species (ROS). In this research, we investigated the protective effect of salvianolic acid B (SAB) as a natural antioxidant on ferroptosis and apoptosis in the MIRI process, and discussed the protective mechanism inhibiting ubiquitin-proteasome degradation of glutathione peroxidase 4 (GPX4) and the c-Jun N-terminal kinases (JNK) apoptosis signal pathway. We observed that ferroptosis and apoptosis occurred in the MIRI rat model in vivo and the H9c2 cardiomyocyte hypoxia/reoxygenation (H/R) damage model in vitro. SAB can alleviate tissue damage related to ROS, ferroptosis and apoptosis. Ubiquitin-proteasome degradation of GPX4 occurred in H/R models, and SAB reduced the ubiquitin-proteasome degradation of GPX4. SAB downregulates JNK phosphorylation and the expression of BCL2-Associated X (Bax)/B-cell lymphoma-2 (Bcl-2) and Caspase-3 to inhibit apoptosis. The role of GPX4 in the cardioprotection of SAB was further verified by the elimination effect of the GPX4 inhibitor RAS-selective lethal 3 (RSL3). This research shows that SAB may be used as a myocardial protective agent against oxidative stress, ferroptosis and apoptosis, and has potential clinical application prospects.

Does a negative ergonovine provocation test truly predict freedom from variant angina?

Ergonovine provocation test is known to be very sensitive for diagnosing variant angina. The patient described in this study initially presented with atypical chest pain and underwent coronary angiography and ergonovine provocation tests, which were negative. The patient was subsequently prescribed a proton pump inhibitor and prokinetics for pain relief, but then presented with acute myocardial infarction and cardiogenic shock due to coronary artery vasospasm 5 years later. This case suggests that ergonovine provocation test generates false negative results, which can lead to unwanted outcomes. Even with a negative ergonovine provocation test, prescription of calcium channel blockers or nitrates should be considered in patients with a clinical history suggestive of variant angina.

The calcium-channel blocker controversy: historical perspective and important lessons for future pharmacotherapies. An international society of pharmacoepidemiology 'hot topic'

Reports of adverse events in association with calcium-channel blockers led to heated controversy over the safety and efficacy of these drugs, as well as to panic among the general public. At the 1998 International Conference of Pharmacoepidemiology, four experts were asked to summarize, and draw lessons from, the controversy's development. We conducted our own review in order to provide a broader historical perspective on the subject and to present the discussants' views within the framework of additional published opinions. Several years after the controversy's onset, many uncertainties still remain about the merits of CCBs. Yet the media scare generated by a few studies might have been prevented had investigators placed greater emphasis, particularly in their reports to the media, on the limitations of their observational and meta-analytic designs. These studies, however, did call attention to the persistent use of CCBs for off-label indications, and the imperative to improve clinician prescribing practices. Moreover, they showed the pitfalls of reliance on surrogate endpoints, stressing the need for data on major clinical outcomes-with funding a responsibility of the pharmaceutical industry-before approving drugs destined for widespread, long-term use. Attention to these lessons will do us well as we evaluate emerging pharmacotherapies. Copyright (c) 2000 John Wiley & Sons, Ltd.

Effect of diltiazem on sympathetic hyperactivity in patients with vasospastic angina as assessed by spectral analysis of arterial pressure and heart rate variability

The autonomic nervous system importantly regulates coronary arterial tone and vascular resistance. To evaluate a role of autonomic nervous activity and the effects of calcium antagonist in patients with vasospastic angina (VSA), 13 VSA patients with patent coronary arteries (58+/-8 years) and 8 normal subjects (58+/-12 years) were studied. Arterial pressure and electrocardiogram were continuously recorded with the patient in a supine position under controlled respiration (0.2 Hz). Low-frequency (LF) and high-frequency (HF) components of the beat-to-beat variabilities of systolic arterial pressure and RR interval were then estimated by autoregressive power spectral analysis. The LF power (normalized unit) of both systolic arterial pressure (0.53+/-0.17 vs 0.30+/-0.17, p < 0.01) and RR variabilities (0.51+/-0.20 vs 0.31+/-0.16, p < 0.05) in patients with VSA were greater than that in normal subjects. There was no significant difference in the HF power. Seven patients with VSA who were treated with diltiazem (60 to 200 mg/day) had normalized LF power (normalized unit) of both systolic arterial pressure (0.62+/-0.12 vs 0.33+/-0.16, p < 0.01) and RR variabilities (0.55+/-0.23 vs 0.36+/-0.14, p < 0.05), together with clinical improvement. An increased sympathetic vasomotor tone and cardiac sympathetic predominance may play an important role in patients with VSA. Diltiazem improves these sympathetic hyperactivities.

Calcium antagonists in patients with left ventricular dysfunction: back on the bridge?

Calcium antagonists have a useful role in the management of patients with cardiac disease, producing coronary and systemic vasodilatation and an additional possibly beneficial effect on ventricular diastolic function. On the other hand, the myocardial depressant effect of the first-generation drugs and the abrupt changes in blood pressure, with neurohormonal activation, have been associated with worsening heart failure in certain patients. The present review summarizes the data currently available, with emphasis on the newer slow-release and long-acting calcium antagonists. Use of these drugs minimizes the peak and trough effect associated with short-acting preparations, and particularly when administered against a background of digoxin, diuretic and angiotensin converting enzyme inhibitors, may be associated with better long-term results in patients with ventricular dysfunction. The DEFIANT studies, using nisoldipine-coat core, showed that nisoldipine-CC improved diastolic ventricular function and had a significant anti-ischemic effect in patients with mild-moderate ventricular dysfunction after acute myocardial infarction. The VHeFT III trial showed that felodipine had no effect on exercise capacity or survival in patients with Class 2-3 heart failure. In the PRAISE study of Class 3-4 patients, amlodipine was neutral in patients with ischemic disease, but a strikingly beneficial effect was observed in non-ischemic heart failure (45% decrease in mortality). The precise mechanism for the beneficial effect of amlodipine in these patients is unknown. Further studies are needed to examine the issue of survival benefit in patients with non-ischemic heart failure and the mechanisms involved.

Calcium channel antagonists in the management of anginal syndromes: changing concepts in relation to the role of coronary vasospasm

Despite the increasing evidence that alterations in coronary vascular tone can and do occur in patients with anginal syndromes, only in a minority of such patients with Prinzmetal's angina is there decisive evidence that the coronary vasodilation induced by calcium channel antagonists (CCAs) plays a specific therapeutic role. CCAs may also give therapeutic benefit in a number of conditions in which coronary vasoconstriction may contribute to ischemia, such as hyperventilation, cold-induced angina, or silent ischemia not caused by an increase in heart rate. Thus, the decision of whether or not to use CCAs in angina syndromes will often have to be made on grounds other than what appears to be a minor role of vasospasm in the overall spectrum of angina. There are preliminary indications that the long-term prognosis may be different among different categories of CCAs.

Localization of calcium channels of the L-type in human epicardial arteries: a light microscope autoradiographic study

The anatomical localization of Ca2+ channels of the L-type was analyzed in sections of the human right and anterior interventricular coronary arteries by using in vitro light microscope autoradiography associated with radioligand binding techniques. [3H]Nicardipine was utilised as a ligand. Binding of the radioligand to sections of the two coronary arteries was time-, temperature- and concentration-dependent. Analysis of binding isotherms revealed a dissociation constant value of about 0.5 nM in the two arteries and maximum binding capacities of 139 +/- 6.4 fmol/mg tissue for the right coronary artery and of 173 +/- 9.5 for the anterior interventricular branch. The pharmacological profile of [3H]nicardipine binding to sections of human coronary arteries was consistent with the labelling of Ca2+ channels of the L-type. Dihydropyridine derivatives were the most powerful competitors of [3H]nicardipine binding, whereas phenylalkylamines, benzothiazepine or non-selective channel modulators were weak competitors or ineffective. Light microscope autoradiography revealed the highest density of [3H]nicardipine binding sites in the tunica media of the coronary arteries. In this layer Ca2+ channels of the L-type are located within smooth muscle cells. A lower accumulation of the radioligand occurred in the tunica adventitia, whereas no specific binding was found in the tunica intima. Study of the localization of Ca2+ channels in sections of human coronary arteries may contribute to a better understanding of the mechanism of the marked coronary dilatory activity elicited by Ca2+ antagonists demonstrable in both in vitro preparations and in vivo.

Thrombolysis in refractory unstable angina

Multiple drug therapy, including nitrates, beta blockers, calcium antagonists, aspirin, and heparin, has been advocated as effective in the treatment of unstable angina, a syndrome with a multifactorial pathogenesis. Recently, plaque rupture and thrombosis have been demonstrated as the most important pathogenetic mechanisms. Nevertheless, clear-cut results on the effects of thrombolytic treatment in unstable angina are still lacking. Some possible explanations why the medical treatment of unstable angina has still not yet been standardized, whereas that of myocardial infarction has, are suggested. A review of randomized and nonrandomized studies published on this topic evaluating the role of different thrombolytic agents in unstable angina is presented. In addition the role of coronary angiography is discussed. In view of the disappointing results of coronary artery bypass surgery performed in the acute phase of the disease, one of the goals of clinical research is to identify subsets of patients at high and low risk and who undergo different types of therapeutic interventions. To support published data suggesting that total myocardial ischemia has a significant impact on prognosis, we present our results of a study carried out on patients with refractory unstable angina treated with thrombolytic therapy and evaluated with continuous electrocardiographic monitoring in the attempt to correlate total myocardial ischemia with short-term prognosis. Data in favor of the prognostic role of continuous electrocardiographic monitoring in unstable angina are also reviewed. Finally, we propose some suggestions that might be useful for future studies.

Progress in cardioprotection: the role of calcium antagonists

Calcium antagonists are now widely used for the treatment of clinical hypertension and angina pectoris. They are efficacious for the treatment of vasospastic, fixed atherosclerotic and mixed angina; they reduce the incidence of silent ischemia; and they have been shown to reduce postmyocardial infarct angina. Experimental data suggest that they may have certain cardioprotective properties in cases of acute myocardial ischemia and infarction, stunned myocardium, diastolic dysfunction, left ventricular hypertrophy and atherosclerosis. Moreover, they have been shown to improve exercise performance, as well as the diastolic abnormalities in patients with hypertrophic cardiomyopathy. In animals, they may delay or reduce the extent of myocardial necrosis after coronary occlusion or coronary occlusion followed by reperfusion, and in low doses that do not alter the hemodynamic profile, they have been shown to enhance the return of ventricular function in animals with stunned myocardium. However, the early first-generation calcium antagonists (nifedipine, verapamil, diltiazem) have not been shown to reduce myocardial infarct size or to enhance survival in patients with acute myocardial infarction. There now are clinical studies that suggest that, unlike beta blockers or nitrates, nifedipine may slow the development of atherosclerotic progression in humans over a 2-year period, and it seems likely that in the 1990s there will be further expansion of the use of calcium antagonists for not only angina and hypertension but also for aspects of cardioprotection. That calcium antagonists may delay, prevent or possibly regress atherosclerotic lesions is an exciting possibility.

Superior efficacy of propranolol versus nifedipine in double-component angina, as related to different influences on coronary vasomotility

PURPOSE

In 24 patients with stable spontaneous and effort-related angina, ischemic episodes at rest were not preceded by changes in circulatory variables (heart rate, systemic and pulmonary arterial pressures) that may raise the myocardial oxygen consumption. We interpreted these episodes as caused by critical and reversible coronary flow reduction at the site of a stenotic lesion, and evaluated the clinical efficacy of nifedipine and propranolol in the treatment of this condition.

PATIENTS AND METHODS

The study was randomized, placebo-controlled, and crossover in design. Nineteen of the 24 subjects were men (mean group age, 59 years; range, 47 to 65 years). The study consisted of four four-day periods. The first and the fourth periods, during which patients received placebo, were single-blind. The treatment consisted of 80 mg of propranolol or 20 mg of nifedipine administered four times daily. The second and the third periods, during which patients received propranolol or nifedipine crossing over to the alternative drug in the next period, were double-blind and separated by a 24-hour interval.

RESULTS

Propranolol fully abolished or reduced the number of spontaneous ischemic episodes in a significantly larger proportion of patients than did nifedipine; it was also effective in several cases in which nifedipine had failed or had even caused a paradoxic effect. Quantitative angiographic evaluation of the influences of nifedipine (Group 1, 12 patients, 10 mg sublingually) and propranolol (Group 2, 12 patients, 0.1 mg/kg intravenously) on the residual lumen diameter of one significant coronary stenosis in each patient showed that (1) after nifedipine, the lumen was unchanged in one, augmented in seven, and reduced in four cases; (2) variations ranged between +1.59 and -1.2 mm, and their direction correlated closely with the influence of oral nifedipine on the episodes of spontaneous ischemia; and (3) in no case did treatment with propranolol vary the stenosis lumen by more than 0.3 mm.

CONCLUSION

In this form of angina, a number of lesions seem to offer a compliant substrate for vasomotion and, possibly, for critical changes in flow. The vasomotor influences of nifedipine on these lesions are variable as well as the efficacy of the drug on the manifestations of ischemia at rest. Propranolol produces no important variations of the coronary stenotic lesions, causes a decrease of heart rate that facilitates coronary flow in diastole, and reduces the baseline metabolic demand of the heart so that the threshold of ischemia during critical reduction of coronary flow may become elevated.

Comparison of coronary vasomotor responses to nifedipine in syndrome X and in Prinzmetal's angina pectoris

To test whether calcium channel blockade plays a similar role in the coronary vasomotion of patients with syndrome X (n = 29) and patients with Prinzmetal's angina pectoris (n = 12), quantitative angiography was used to evaluate the effect of nifedipine (10 mg, sublingually) on the lumen diameter of proximal, mid and distal thirds of normal epicardial branches. The main differences in the coronary vasomotor reaction were uniform vasodilatation in Prinzmetal's angina and a variable response to syndrome X, and a greater increase in the coronary lumen in patients with Prinzmetal's angina as compared with those with syndrome X who showed vasodilatation. The variable response in syndrome X was not related to changes in diastolic pressure and cardiac output. Patients showing coronary constriction were those who responded to nifedipine with a higher degree of tachycardia, which might suggest a neural participation in the paradoxic reaction to this drug. In the Prinzmetal group, on the contrary, at a similar heart rate increase the pattern was invariably vasodilatation. Thus, calcium ions appear to have a different role in the coronary smooth muscle contractility of the 2 series of patients; in fact, in Prinzmetal's angina nifedipine relaxed the coronary arteries to a greater degree and made them unresponsive to stimuli that were still able to cause vasoconstriction in patients with syndrome X.

Efficacy and safety of intravenous diltiazem for treatment of atrial fibrillation and atrial flutter. The Diltiazem-Atrial Fibrillation/Flutter Study Group

This study evaluates the effectiveness and safety of intravenous diltiazem for the treatment of atrial fibrillation and atrial flutter. A double-blind, parallel, randomized, placebo-controlled protocol was used, and 6 large, urban hospitals, both university-affiliated and private, participated. The study involved 113 patients with atrial fibrillation or flutter, a ventricular rate greater than or equal to 120 beats/min and systolic blood pressure greater than or equal to 90 mm Hg without severe heart failure. The dose of intravenous diltiazem (or identical placebo) was 0.25 mg/kg/2 minutes followed 15 minutes later by 0.35 mg/kg/2 minutes if the first dose was tolerated but ineffective. If a patient did not respond, the code was broken and the patient was allowed to receive open-label diltiazem if placebo had been given. Of 56 patients, 42 (75%) randomized to receive diltiazem responded to 0.25 mg/kg and 10 of 14 responded to 0.35 mg/kg, for a total response rate of 52 of 56 patients (93%), whereas 7 of 57 patients (12%) responded to placebo (p less than 0.001). After the double-blind protocol, 49 of the 57 patients who received placebo were then given diltiazem; 47 of 49 responded, for an overall response rate of 99 of 105 patients (94%) with diltiazem. The median time from the start of drug infusion to the maximal decrease in heart rate was 4.3 minutes. Side effects occurred in 14 patients, 7 of whom had asymptomatic hypotension not requiring intervention. Thus, intravenous diltiazem was rapidly effective for slowing the ventricular response in most patients with atrial fibrillation or atrial flutter. Blood pressure decreased slightly. Side effects were mild.

Morphologic features of unstable atherothrombotic plaques underlying acute coronary syndromes

Unstable angina appears to be a good clinical marker for rapidly progressing coronary artery disease. Pathologically, an unstable atherothrombotic coronary lesion, represented by a raised atherosclerotic plaque with ruptured surface causing variable degree of hemorrhage into the plaque and luminal thrombosis (rapid plaque progression), usually is present in patients at autopsy after a period of unstable angina. The thrombus at the rupture site may be mural and limited (just sealing the rupture) or occlusive, depending on the degree of preexisting atherosclerotic stenosis. An occlusive thrombus is seldom seen over ruptured plaques causing less than 75% stenosis (histologic cross-sectional area reduction), but it is found with increasing frequency when severity of stenosis increases beyond 75%. Most occlusive thrombi have a layered structure with thrombus material of differing age indicating an episodic growth by repeated mural deposits, and microemboli/microinfarcts are frequently found in the myocardium downstream to coronary thrombi, indicating intermittent thrombus fragmentation with peripheral embolization. Such a "dynamic thrombosis" (with or without a concomitant focal vasospastic phenomenon) at the site of an unstable (ruptured) atherosclerotic lesion obviously may lead to the other thrombus-related acute coronary events: myocardial infarction or sudden death. Accordingly, progression of unstable angina to myocardial infarction or sudden death should, in principle, be preventable by the correct timing of current available therapies aimed to prevent or eliminate (1) the chronic atherosclerotic obstruction, (2) the acute plaque disruption, (3) luminal thrombosis, and (4) vasospasm.

Different coronary vasomotor effects of nifedipine and therapeutic correlates in angina with spontaneous and effort components versus Prinzmetal angina

Flow impedance, probably of vasomotor origin, superimposed on severe coronary stenosis has been considered a trigger for the spontaneous component of angina occurring both on effort and at rest. To investigate more thoroughly this pathophysiologic aspect we evaluated (by means of quantitative coronary angiography) the acute vasomotor reaction to nifedipine (10 mg sublingually) of significant (greater than 50%) stenotic lesions in 22 patients with double-component angina. We also correlated this reaction with the clinical response (daily number of ischemic episodes evaluated by means of 48-hour Holter ambulatory monitoring) to treatment with nifedipine (20 mg four times a day); calcium channel blockade, in fact, is considered a specific remedy in cases of altered coronary vasomotility. Patients with Prinzmetal angina, who were known to have homogeneous coronary vasodilating reactions and favorable clinical responses to nifedipine, were studied by means of the same methods and served as the control group (14 patients). In double-component angina the residual lumen diameter of significant lesions was unchanged in two patients, enhanced in 10, and reduced in 10 after sublingual nifedipine; lumen variations from baseline values ranged from +1.29 to -1.56 mm. Acute changes in stenosis correlated closely with results obtained with oral treatment. In the group with Prinzmetal angina, coronary stenoses invariably responded with dilatation (the residual coronary lumen increased by an average of 69% of baseline); 100% of the patients in this group responded favorably to treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Near-total reduction in verapamil bioavailability by rifampin. Electrocardiographic correlates

We evaluated the significance of the interaction between rifampin and verapamil in six volunteers who received single doses of verapamil, 10 mg intravenously (IV), then 120 mg orally two days later. Subjects were then given rifampin, 600 mg orally every day for 15 days. After 13 and 15 days of rifampin therapy, the IV and oral doses of verapamil were repeated. Electrocardiograms (ECG) were done and serum verapamil and norverapamil concentrations measured before and for 12 h after each dose. For IV verapamil, there was a small decrease in area under the serum concentration-time curve and an increase in clearance after rifampin therapy (p less than 0.05). There were no changes in elimination half-life, volume of distribution, or AUC for percentage of change in P-R interval-time curve (AUCPR). For oral verapamil, there were marked decreases in peak concentration, AUC, oral bioavailability (all p less than 0.005), and AUCPR (p less than 0.001) after rifampin treatment. There were no changes in time to peak concentration or elimination half-life. For oral verapamil, significant P-R interval prolongation occurred only before treatment with rifampin. The decrease in oral bioavailability and the abolition of ECG response confirm that a highly significant drug interaction exists between rifampin and verapamil given orally but not intravenously.

Silent myocardial ischemia: an update

Silent myocardial ischemia is diagnosed by several different techniques and has been documented in all the anginal syndromes. In addition to other factors, its presence may be related to increased pain threshold and increased pain tolerance. Although some patients with painless ischemia may have less extensive coronary artery disease, cumulative evidence indicates that silent myocardial ischemia does not necessarily signify a lesser degree of cardiac ischemia or a less severe coronary abnormality. As judged by ambulatory monitoring studies, it shows circadian variation; occurs more frequently than symptomatic ischemia; and appears to depend, in large part, on activation of the sympathetic nervous system. Frequent silent ischemic events during ambulatory monitoring are worrisome because they reflect the disease "activity" of single or multiple coronary atherosclerotic lesions. Thus, there may be a direct association between the severity of ischemia seen during Holter monitoring, the extent of underlying coronary artery disease or disease activity, and prognosis. When diagnosed by exercise testing, silent myocardial ischemia may be associated with significant coronary involvement. In this regard, patients with three vessel coronary disease, impaired left ventricular function, and silent ischemia during stress testing should benefit from coronary revascularization. Compared with symptomatic patients, other evidence suggests that patients with exercise-induced asymptomatic ischemia have at least the same or perhaps even a worse outlook; this may be related to the lack of symptoms that would prompt evaluation and therapy. Awareness of the possibility of silent myocardial ischemia and use of commonly available tests, both to establish its presence and severity and to guide treatment, are emerging as new clinical goals. Further data, however, are necessary to determine how vigorously this should be pursued in different patient subgroups. In association with unstable angina or post-myocardial infarction, the added risk of silent myocardial ischemia warrants a more aggressive approach.

Calcium channel antagonists. Part IV: Side effects and contraindications drug interactions and combinations

With the correct selection of drug and patient, the calcium antagonists as a group can be remarkably effective at relatively low cost of serious side effects. Almost all side effects are dose related. Minor side effects include those caused by vasodilation (flushing and headaches), constipation (verapamil), and ankle edema. Serious side effects are rare and result from improper use of these agents, as when intravenous verapamil (or diltiazem) is given to patients with sinus or atrioventricular nodal depression from drugs or disease, or nifedipine to patients with aortic stenosis. The potential of a marked negative inotropic effect is usually offset by afterload reduction, especially in the case of nifedipine which actually has the most marked negative inotropic effect. Yet caution is required when even calcium antagonists, especially verapamil, are given to patients with myocardial failure unless caused by hypertensive heart disease. Drug interactions of calcium antagonists occur with other cardiovascular agents such as alpha-adrenergic blockers, beta-adrenergic blockers, digoxin, quinidine, and disopyramide. The most marked interaction with digoxin is that with verapamil, which may raise digoxin levels by over 50%. Combination therapy of calcium antagonists with beta-blockers is increasingly common, and is probably safest in the case of dihydropyridines. Other combinations being explored are those with angiotensin-converting enzyme inhibitors and diuretics.

Calcium channel antagonists. Part III: Use and comparative efficacy in hypertension and supraventricular arrhythmias. Minor indications

The major antihypertensive mechanism of calcium antagonists is by decreasing the systemic vascular resistance, modified by the counter-regulatory responses of the baroreflexes and the renin-angiotensin-aldosterone system. In severe hypertension, the concept that calcium overload of the vascular myocyte could precipitate or aggravate peripheral vasoconstriction provides a logical basis for the use of these agents as first choice therapy; nifedipine, especially, has been well tested. As monotherapy for mild to moderate hypertension each of the three first-generation agents compares well with beta-blockers. Calcium antagonists may have a special role in the therapy of certain patient groups (elderly, black) or in those subjects whose life style involves intense physical or mental exertion (hemodynamics better maintained than with beta-blockade) or in patients with early end-organ damage such as left ventricular hypertrophy or renal insufficiency. However, the goal blood pressure may not be reached during monotherapy so that drug combinations may be required. Further indications for these compounds are as follows. Verapamil and diltiazem are frequently used in supraventricular tachycardias including acute and chronic atrial fibrillation. In the arrhythmias of the Wolff-Parkinson-White syndrome, there is the potential danger of provocation of anterograde conduction. Further indications for calcium antagonists, still under evaluation, include congestive heart failure (controversial), hypertrophic cardiomyopathy (verapamil), primary pulmonary hypertension (high doses required), Raynaud's phenomenon (nifedipine and diltiazem effective), peripheral vascular disease (proof not yet documented), cerebral insufficiency and subarachnoid hemorrhage (nimodipine promising), migraine, exertional bronchospasm, renal disease, atherosclerosis (experimental), and primary aldosteronism (nifedipine inhibits aldosterone release). Second-generation agents include dihydropyridines, such as nitrendipine, nicardipine, felodipine, amlodipine, nisoldipine, nimodipine, and isradipine. From these will be selected agents that are longer acting and provide higher vascular selectivity. New preparations of existing agents include slow-release formulations of nifedipine, verapamil, and diltiazem. Minor side effects include those caused by vasodilation (flushing and headaches), constipation (verapamil), and ankle edema. Serious side effects are rare and result from improper use of these agents, as when intravenous verapamil is given to patients with sinus or atrioventricular nodal depression from drugs or disease, or nifedipine to patients with aortic stenosis. The potential of a marked negative inotropic effect is usually offset by afterload reduction, especially in the case of nifedipine. Yet caution is required when calcium antagonists, especially verapamil, are given to patients with myocardial failure unless caused by hypertensive heart disease. Drug interactions of calcium antagonists occur with other cardiovascular agents such as alpha-adrenergic blockers, beta-adrenergic blockers, digoxin, quinidine, and disopyramide.(ABSTRACT TRUNCATED AT 400 WORDS)

Calcium channel antagonists. Part II: Use and comparative properties of the three prototypical calcium antagonists in ischemic heart disease, including recommendations based on an analysis of 41 trials

An analysis of 41 trials of angina of all varieties confirms that calcium antagonists are an important advance and are now established therapy for these syndromes. In effort angina, verapamil in a dose of 360-480 mg daily is better than propranolol in standard doses. Although nifedipine is highly effective against vasospastic angina, its use in threatened myocardial infarction or severe unstable angina is not supported by recent studies, unless combined with a beta-blocker. Diltiazem has recently been tested with apparent benefit in non-Q-wave myocardial infarction. Otherwise, these calcium antagonist agents all seem to have approximate equipotency in clinical ischemic syndromes including effort and vasospastic angina. Subjective side effects seem most troublesome in the case of nifedipine. All three calcium antagonists, especially nifedipine, have been successfully combined with beta-blocker therapy, yet occasional additive negative inotropic or chronotropic or dromotropic interactions may occur when verapamil or diltiazem is added to beta-blockade, and occasionally the direct negative inotropic potential of nifedipine may become evident. The choice between the calcium antagonists is determined not only by the clinical picture but also by the anticipated side effects in a given patient and by the overall cardiovascular status. In patients with supraventricular tachycardias or sinus tachycardia, verapamil or diltiazem is preferred, whereas in patients with a resting bradycardia or borderline heart failure nifedipine is likely to be chosen.