Combination therapy with calcium-channel blockers and beta blockers for chronic stable angina pectoris

Biomimetic nanoparticle technology for cardiovascular disease detection and treatment

Cardiovascular disease (CVD), which encompasses a number of conditions that can affect the heart and blood vessels, presents a major challenge for modern-day healthcare. Nearly one in three people has some form of CVD, with many suffering from multiple or intertwined conditions that can ultimately lead to traumatic events such as a heart attack or stroke. While the knowledge obtained in the past century regarding the cardiovascular system has paved the way for the development of life-prolonging drugs and treatment modalities, CVD remains one of the leading causes of death in developed countries. More recently, researchers have explored the application of nanotechnology to improve upon current clinical paradigms for the management of CVD. Nanoscale delivery systems have many advantages, including the ability to target diseased sites, improve drug bioavailability, and carry various functional payloads. In this review, we cover the different ways in which nanoparticle technology can be applied towards CVD diagnostics and treatments. The development of novel biomimetic platforms with enhanced functionalities is discussed in detail.

Correcting Calcium Dysregulation in Chronic Heart Failure Using SERCA2a Gene Therapy

Chronic heart failure (CHF) is a major contributor to cardiovascular disease and is the leading cause of hospitalization for those over the age of 65, which is estimated to account for close to seventy billion dollars in healthcare costs by 2030 in the US alone. The successful therapies for preventing and reversing CHF progression are urgently required. One strategy under active investigation is to restore dysregulated myocardial calcium (Ca²⁺), a hallmark of CHF. It is well established that intracellular Ca²⁺ concentrations are tightly regulated to control efficient myocardial systolic contraction and diastolic relaxation. Among the many cell surface proteins and intracellular organelles that act as the warp and woof of the regulatory network controlling intracellular Ca²⁺ signals in cardiomyocytes, sarco/endoplasmic reticulum Ca²⁺ ATPase type 2a (SERCA2a) undoubtedly plays a central role. SERCA2a is responsible for sequestrating cytosolic Ca²⁺ back into the sarcoplasmic reticulum during diastole, allowing for efficient uncoupling of actin-myosin and subsequent ventricular relaxation. Accumulating evidence has demonstrated that the expression of SERCA2a is downregulated in CHF, which subsequently contributes to severe systolic and diastolic dysfunction. Therefore, restoring SERCA2a expression and improving cardiomyocyte Ca²⁺ handling provides an excellent alternative to currently used transplantation and mechanical assist devices in the treatment of CHF. Indeed, advancements in safe and effective gene delivery techniques have led to the emergence of SERCA2a gene therapy as a potential therapeutic choice for CHF patients. This mini-review will succinctly detail the progression of SERCA2a gene therapy from its inception in plasmid and animal models, to its clinical trials in CHF patients, highlighting potential avenues for future work along the way.

Combination of β Adrenergic Receptor Block and Renin-Angiotensin System Inhibition Diminished the Angiotensin II-Induced Vasoconstriction and Increased Bradykinin-Induced Vasodilation in Hypertension

In hypertension, the combination therapy is frequently used to obtain a better therapeutic effect and reduce adverse effects. One effective combination is with inhibitors and β-blockers of renin–angiotensin system. Although the mechanisms of action of each drug are already known, the antihypertensive mechanism is more complex and therefore the combined treatment mechanism is unclear. Specifically, the effect of the treatments of angiotensin-converting enzyme inhibitor or AT₁ receptor antagonist with β-blocker on the angiotensin II and bradykinin reactivity has not been studied. For this reason, we evaluated the interaction between propranolol and captopril or losartan on vascular reactivity to bradykinin and angiotensin II in spontaneously hypertensive rat. We constructed concentration–response curves to angiotensin II and bradykinin after treatment of SHR with propranolol–captopril or propranolol–losartan by using rat aortic rings. While losartan or captopril with propranolol potentiated bradykinin-induced vasodilation effect, the propranolol–losartan interaction decreased the angiotensin II-induced vasoconstriction. In addition, the combinations did not reduce the heart rate significantly. These results suggest that the combined therapy decreased blood pressure to normotensive values and showed less effect for angiotensin II and greater effect for bradykinin than monotherapy which could contribute in the antihypertensive effect.

Advancements in pharmacotherapy for angina

INTRODUCTION

Angina pectoris is the most prevalent symptomatic manifestation of ischemic heart disease, frequently leads to a poor quality of life, and is a major cause of medical resource consumption. Since the early descriptions of nitrite and nitrate in the 19th century, there has been considerable advancement in the pharmacologic management of angina. Areas covered: Management of chronic angina is often challenging for clinicians. Despite introduction of several pharmacological agents in last few decades, a significant proportion of patients continue to experience symptoms (i.e., refractory angina) with subsequent disability. For the purpose of this review, we searched PubMed and Cochrane databases from inception to August 2016 for the most clinically relevant publications that guide current practice in angina therapy and its development. In this article, we briefly review the pathophysiology of angina and mechanism-based classification of current therapy. This is followed by evidence-based insight into the traditional and novel pharmacotherapeutic agents, highlighting their clinical usefulness. Expert opinion: Considering the wide array of available therapies with different mechanism efficacy and limiting factors, a personalized approach is essential, particularly for patients with refractory angina. Ongoing research with novel pharmacologic modalities is likely to provide new options for management of angina.

Recent advances in the management of chronic stable angina II. Anti-ischemic therapy, options for refractory angina, risk factor reduction, and revascularization

The objectives in treating angina are relief of pain and prevention of disease progression through risk reduction. Mechanisms, indications, clinical forms, doses, and side effects of the traditional antianginal agents - nitrates, β-blockers, and calcium channel blockers - are reviewed. A number of patients have contraindications or remain unrelieved from anginal discomfort with these drugs. Among newer alternatives, ranolazine, recently approved in the United States, indirectly prevents the intracellular calcium overload involved in cardiac ischemia and is a welcome addition to available treatments. None, however, are disease-modifying agents. Two options for refractory angina, enhanced external counterpulsation and spinal cord stimulation (SCS), are presented in detail. They are both well-studied and are effective means of treating at least some patients with this perplexing form of angina. Traditional modifiable risk factors for coronary artery disease (CAD) - smoking, hypertension, dyslipidemia, diabetes, and obesity - account for most of the population-attributable risk. Individual therapy of high-risk patients differs from population-wide efforts to prevent risk factors from appearing or reducing their severity, in order to lower the national burden of disease. Current American College of Cardiology/American Heart Association guidelines to lower risk in patients with chronic angina are reviewed. The Clinical Outcomes Utilizing Revascularization and Aggressive Drug Evaluation (COURAGE) trial showed that in patients with stable angina, optimal medical therapy alone and percutaneous coronary intervention (PCI) with medical therapy were equal in preventing myocardial infarction and death. The integration of COURAGE results into current practice is discussed. For patients who are unstable, with very high risk, with left main coronary artery lesions, in whom medical therapy fails, and in those with acute coronary syndromes, PCI is indicated. Asymptomatic patients with CAD and those with stable angina may defer intervention without additional risk to see if they will improve on optimum medical therapy. For many patients, coronary artery bypass surgery offers the best opportunity for relieving angina, reducing the need for additional revascularization procedures and improving survival. Optimal medical therapy, percutaneous coronary intervention, and surgery are not competing therapies, but are complementary and form a continuum, each filling an important evidence-based need in modern comprehensive management.

Monotherapy with amlodipine or atenolol versus their combination in stable angina pectoris

BACKGROUND

The basic cause of angina pectoris is imbalance between the metabolic needs of the myocardium and the capacity of the coronary circulation to deliver sufficient oxygenated blood to satisfy these needs.

HYPOTHESIS

The study was undertaken to evaluate whether the effect of combined amlodipine and atenolol therapy on patients with stable angina pectoris and with ST-depression during exercise testing and 48-h ambulatory electrocardiographic monitoring is superior to that of either agent given alone.

METHODS

Patients with stable angina pectoris and ST depression during exercise and ambulatory monitoring were randomized to receive amlodipine (n = 116) or atenolol (n = 116), or both (n = 119). All patients were also treated with short- and long-acting nitrates. The design was a double-blind, randomized, triple-arm parallel group study with 10 weeks of administration of the test medication.

RESULTS

In terms of time to onset of ST depression > 1 mm, time to onset of angina, total exercise time, maximum achieved workload, and peak intensity of angina, amlodipine and atenolol alone were as effective as their combination. During ambulatory monitoring, atenolol was more effective than amlodipine regarding total time and number of ST-depression episodes, and as effective as the combined drugs.

CONCLUSION

For individual patients with stable angina pectoris, combination of a beta blocker with a calcium antagonist is not necessarily more effective than either drug given alone.

Cardiovascular adverse drug reaction associated with combined beta-adrenergic and calcium entry-blocking agents

Numerous studies have shown a beneficial effect of combination therapy with beta-blockers and calcium antagonists in patients with anginal syndrome and/or hypertension. However, because both agents exert a negative chronotropic effect, their combined use may cause bradyarrhythmias with resultant symptoms of cerebral, coronary, and systemic hypoperfusion. We describe our clinical experience with patients who had cardiovascular adverse drug reactions (CVADRs) with combination therapy. This prospective study included 26 patients who had CVADRs among 2,574 admissions during a 2-year period. The study group included 14 men and 12 women with a median age of 73 years. Various combinations of calcium antagonists and beta-blockers were associated with the CVADRs. The most frequent pharmacologic combination was diltiazem plus propranolol. The CVADRs were the cause for hospital admission in 10 patients, an associated cause in nine patients, and developed during hospitalization in seven patients. Cardiac bradyarrhythmias were found in 22 patients. These rhythm abnormalities resolved within 24 h after discontinuation of the offending drugs. Temporary transvenous pacemaker insertion was necessary in only one patient with complete atrioventricular block. Twenty-two patients recovered, two patients died of pump failure not associated with CVADRs, and in two patients, the CVADRs contributed to the patients' death. CVADRs are not uncommon in elderly patients with ischemic heart disease and/or hypertension treated with the concomitant use of calcium antagonist and beta-adrenergic blocking drugs. Use of calcium antagonist plus beta-blocker may unpredictably cause serious hemodynamic events, marked suppression of sinus node activity, and prolongation of atrioventricular conduction in some patients. Enhanced therapeutic monitoring may be warranted when calcium antagonists are combined with beta-blockers.

Vanidipinedilol: a vanilloid-based beta-adrenoceptor blocker displaying calcium entry blocking and vasorelaxant activities

Calcium channel and beta-adrenoceptor blockade have proved highly useful in antihypertensive therapy. Studies of the mechanisms of action of vanidipinedilol that combine these effects within a single molecule are described here. Intravenous injection of vanidipinedilol (0.1, 0.25, 0.5, 1.0, and 2.0 mg/kg) produced dose-dependent hypotensive and bradycardic responses, significantly different from nifedipine-induced (0.5 mg/kg, i.v.) hypotensive and reflex tachycardic effects in pentobarbital-anesthetized Wistar rats. A single oral administration of vanidipinedilol at doses of 10, 25, and 50 mg/kg dose-dependently reduced blood pressure with a decrease in heart rate in conscious spontaneously hypertensive rats (SHRs). In the isolated Wistar rat atrium, vanidipinedilol (10(-7), 10(-6), and 10(-5) M) competitively antagonized the (-)isoproterenol-induced positive chronotropic and inotropic effects and inhibited the increase in heart rate induced by Ca2+ (3.0-9.0 mM) in a concentration-dependent manner. The parallel shift to the right of the concentration-response curve of (-)isoproterenol and CaCl2 suggested that vanidipinedilol possessed beta-adrenoceptor-blocking and calcium entry-blocking activities. On tracheal strips of reserpinized guinea pig, cumulative doses of vanidipinedilol (10(-10) to 3x10(-6) M) produced dose-dependent relaxant responses. Preincubating the preparation with ICI 118,551 (10(-10), 10(-9), 10(-8) M), a beta2-adrenoceptor antagonist, shifted the vanidipinedilol concentration-relaxation curve significantly to a region of higher concentrations. These results implied that vanidipinedilol had a partial beta2-agonist activity. In the isolated thoracic aorta of rat, vanidipinedilol had a potent effect inhibiting high-K+-induced contractions. KCI-induced intracellular calcium changes of blood vessel smooth muscle cell (A7r5 cell lines) determined by laser cytometry also was decreased after administration of vanidipinedilol (10(-8), 10(-7), 10(-6) M). Furthermore, the binding characteristics of vanidipinedilol and various antagonists were evaluated in [3H]CGP-12177 binding to ventricle and lung and [3H]nitrendipine binding to cerebral cortex membranes in rats. The order of potency of beta1- and beta2-adrenoceptor antagonist activity against [3H]CGP-12177 binding was (-)propranolol (pKi, 8.59 for beta1 and 8.09 for beta2) > vanidipinedilol (pKi, 7.09 for beta1 and 6.64 for beta2) > atenolol (pKi, 6.58 for beta1 and 5.12 for beta2). The order of potency of calcium channel antagonist activity against [3H]nitrendipine binding was nifedipine (pKi, 9.36) > vanidipinedilol (pKi, 8.07). The ratio of beta1-adrenergic-blocking/calcium entry-blocking selectivity is 0.1 and indicated that vanidipinedilol revealed more in calcium entry-blocking than in beta-adrenergic-blocking activities. It has been suggested that vanidipinedilol-induced smooth muscle relaxation may involve decreased entry of Ca2+ and partial beta2-agonist activities. In conclusion, vanidipinedilol is a nonselective beta-adrenoceptor antagonist with calcium channel blocking and partial beta2-agonist associated vasorelaxant and tracheal relaxant activities. Particularly, the vasodilator effects of vanidipinedilol are attributed to a synergism of its calcium entry blocking and partial beta2-agonist activities in the blood vessel. A sustained bradycardic effect results from beta-adrenoceptor blocking and calcium entry blocking, which blunts the sympathetic activation-associated reflex tachycardia in the heart.

How to use calcium antagonists in hypertension: putting the JNC-VI guidelines into practice. Joint National Committee for the Prevention, Detection, Evaluation and Treatment of High Blood Pressure

The prevention and treatment of hypertension remain as major challenges for clinicians all over the world. The recently published Sixth Report of the Joint National Committee for the Prevention, Detection, Evaluation and Treatment of High Blood Pressure (JNC-VI) uses evidence-based medicine in providing guidelines to aid clinicians in the prevention, detection and treatment of high blood pressure, including pharmacological approaches. Calcium antagonists are used widely for the treatment of hypertension, and JNC-VI focuses on specific situations where calcium antagonists could be considered as preferred treatments. There are a large number of calcium antagonists available, with a variety of pharmacodynamic and pharmacokinetic actions. Several sustained-release formulations of these drugs are also available. In terms of blood pressure control, calcium antagonists are more effective as antihypertensive treatments than beta-blockers, ACE inhibitors and angiotensin II receptor blockers in Black patients. The dihydropyridine calcium antagonists have been shown to reduce morbidity and mortality in elderly patients with isolated systolic hypertension. The rate-lowering calcium antagonists can be used as alternatives to beta-blockers in patients with coronary artery disease and hypertension. Calcium antagonists can be used as alternatives to ACE inhibitors in patients with hypertension and concomitant diabetes mellitus and/or renal disease. Some dihydropyridine calcium antagonists may be useful as alternatives to ACE inhibitors in patients with hypertension and systolic heart failure. Calcium antagonists appear to be extremely useful in patients with cyclosporin-induced hypertension, and in patients with hypertension and concomitant Raynaud's phenomenon and/or migraine. The rate-lowering agents can be used in patients with atrial tachyarrhythmias and hypertension. Clinicians should be aware of drug-drug interactions involving calcium antagonists, especially after the recent problems with mibefradil. Although retrospective studies have caused controversy regarding the safety of calcium antagonists in patients with hypertension, recent prospective studies have revealed no major safety concerns with these drugs.

Calcium antagonists. Drug interactions of clinical significance

The interaction of calcium antagonists, including the dihydropyridine calcium antagonists (e.g. nifedipine), verapamil and diltiazem, with drugs from other classes has major clinical ramifications as the use of drug combinations increases in frequency. Combinations are used in the treatment of disorders ranging from hypertension to cardiac rhythm disturbances, angina pectoris and peripheral vasospastic disease. In this era of organ transplantation, drugs like cyclosporin are coming into potential conflict with an ever-growing list of drugs. Drug combinations used as part of long term therapies are also making their appearance in toxic drug reactions, including antituberculous and anticonvulsant agents. Bronchodilators and H2-blockers also fall into this category of potential culprits of combined drug toxicity, and the interactions of calcium antagonists with beta-blockers and antiarrhythmic agents are also becoming a matter of concern.

Amlodipine in patients with angina uncontrolled by atenolol. A double blind placebo controlled cross over trial

Dihydropyridine calcium antagonists are established second line treatment for angina uncontrolled by beta-adrenergic blockers. Amlodipine is a recently introduced, dihydropyridine with a long half life. In a double blind, placebo controlled, cross over trial we assessed the efficacy and safety of amlodipine in 20 patients with persistent angina despite treatment with atenolol. 17 male patients (mean age 58 y) completed the study. Two patients were withdrawn during placebo because of worsening angina and one withdrew whilst on amlodipine because of palpitations. Compared with baseline, amlodipine prolonged exercise time to S-T segment depression by a median of 12.5%; significantly more than was found with placebo (median 0%). The improvement in exercise time and time to angina also tended to be greater for amlodipine than placebo. GTN consumption, at a median of 1.3/week, was significantly less with amlodipine than placebo (2.8). Attacks of angina were also reduced. Standing systolic and diastolic blood pressures and sitting systolic blood pressure were lower with amlodipine than placebo. Heart rate did not change. There was no change in cardiac output (measured by doppler aortovelography) when amlodipine was added to atenolol. Holter monitor measurements of 24 h maximum and minimum heart rate, heart rate variation and extrasystole counts were the same for amlodipine and placebo. In conclusion, amlodipine is effective in patients with angina inadequately controlled by atenolol alone, and does not interfere with cardiac rhythm or function.

New synthetic ligands for L-type voltage-gated calcium channels

The pharmacology of the L-type Ca2+ channel has been the subject of considerable basic and clinical investigation over the past two decades primarily because of the clinical activities of nifedipine, verapamil and diltiazem. However, it is quite clear that this Ca2+ channel is, in common with other pharmacologic receptors, a multiple drug receptor. There are probably as many as six or more discrete drug binding sites associated with this Ca2+ channel. Continued investigation of these sites may yield both new therapeutic agents, structural clues to ligands active at other classes of Ca2+ channel and structures active at other classes of ion channel.

Symptomatic bradycardia induced by the combination of oral diltiazem and beta blockers

Ten patients, who were admitted to the Intensive Coronary Care Unit during a one year period with symptomatic bradycardia while on combination therapy with oral diltiazem and beta-blocker agents, are described. The important features of this adverse reaction to drug combination were that it appeared mainly in a relatively elderly age group and with presenting symptoms of lethargy, dizziness, syncope, chest pain, and (in one patient with poor left ventricular function) pulmonary edema. It was not dose dependent and occurred even in very low doses of each drug. Electrophysiologic abnormalities were localized to the sinus node in all 10 patients and the primary rhythm disorders were junctional escape rhythm, sinus bradycardia, and sinus pause. These rhythm abnormalities resolved within 24 h following withdrawal of the offending drugs. Temporary pacemaker insertion was necessary in four patients. The duration of drug combination used before the acute episode range from within hours to up to 2 years. In conclusion, although combination diltiazem/beta blocker therapy is very effective in ischemic syndrome, caution is advised when this combination is used especially in the elderly or in patients with left ventricular dysfunction or antecedent sinoatrial or atrioventricular conduction abnormality.

Kinetics and hemodynamic effects of intravenous nicardipine modified by previous propranolol oral treatment

Intravenous nicardipine, 5 mg, was administered in two comparable groups of eight patients with chronic coronary artery disease but no clinical signs of heart failure. One group had received no previous treatment and served as a control group, and the other had received long-term treatment with large oral doses of propranolol. Blood concentrations of nicardipine were higher, and the area under the plasma concentration curve was greater in the group previously treated by propranolol. The total clearance of nicardipine was decreased in patients taking propranolol, without a change in the half-life of the drug. Typical hemodynamic responses, namely, a decrease in aortic pressure and in arterial resistances, were greater and more lasting in patients previously treated orally by propranolol. Filling pressure remained stable in both groups. The nicardipine infusion did not induce signs of dromotropic or inotropic negative effects in either group. The greater and more lasting hemodynamic effects of nicardipine in the group previously treated orally by propranolol do not seem to be related to an overall hemodynamic action of propranolol, but are probably due to higher nicardipine plasma levels, and may be caused by a decrease in hepatic blood flow induced by propranolol, with a consequent decrease in nicardipine clearance and by a smaller nicardipine volume of distribution in the propranolol group.

Stable angina pectoris: 3. Medical treatment

The therapeutic goals for the patient with angina pectoris are to minimize the frequency and severity of angina and to improve functional capacity at a reasonable cost and with as few side effects as possible. An integrated approach necessitates attention to conditions that might be aggravating angina, such as anemia or hypertension. Alterations in life-style and personal habits, such as cessation of cigarette smoking, are often necessary and should be continually reinforced by the physician. Certain concomitant diseases, such as chronic obstructive pulmonary disease, may influence the selection of drug therapy. Nitrates, beta-adrenergic blockers, and calcium entry blockers are the major classes of drugs that can be used alone or in combination in a program that is designed for the individual patient.

[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.

Calcium channel antagonism and beta blockade in combination--a therapeutic alternative in cardiovascular disorders. A review

Calcium-channel antagonists and beta-adrenergic blocking agents have become important modalities in the cardiovascular therapeutic armamentarium. These drugs are often administered as monotherapy to a wide range of cardiological patients with angina pectoris, hypertension, arrhythmias, congestive heart failure, and other diseases. Since within each class these drugs exhibit pharmacologic differences, it follows that their effectiveness varies in different disease states and that they exhibit a wide variety of side effects. In an attempt to optimize therapy, the individual drugs from these two classes can be combined; and the efficaciousness and side-effect profile of various combinations between calcium-channel antagonists and beta blockers are discussed in this review. Recommendations as to which patients may benefit from a combination and as to which patients may be harmed by the combination therapy will be made. Very few studies have compared the safety and efficacy of a single agent with the combination and with placebo in a controlled randomized fashion. To determine which therapy is superior and to determine which combination one should recommend under what circumstances, such placebo-controlled, randomized trials are a necessity, and will hopefully be performed although the complexity is enormous.

Effect of calcium entry and beta blockade during infrarenal aortic clamping

Clamping and declamping during aortic surgery produce a hemodynamically significant myocardial stress. The cardiovascular (CV) response to this stress may be adversely altered by calcium antagonists and beta-adrenoreceptor blockade employed to control symptomatic coronary artery disease. This study evaluated the effect of verapamil (V), propranolol (P), and their combination (P + V) on the CV response to infrarenal abdominal aortic cross-clamping and declamping in anesthetized dogs. Six dogs received P as a bolus of 0.5 mg/kg 20 min before clamping. Six additional dogs received V as a 300 micrograms/kg bolus followed by a V infusion of 6 micrograms/kg/min for 20 min before clamping. A third group of six dogs received the P bolus followed 20 min later by the V regimen (P + V). In both the V and P + V groups, 6 micrograms/kg/min V was infused throughout the clamping and declamping sequence. A fourth group of six control dogs received no cardioactive drugs during the experiment. Heart rate, mean aortic blood pressure, left ventricular end-diastolic pressures, peak rate of rise of left ventricular pressure, cardiac output, and systemic vascular resistance were measured in all animals before aortic cross-clamping, at 5 and 40 min after clamping, and 5 min after declamping. The results demonstrated additive negative chronotropic and inotropic properties of P + V therapy with a more significantly adverse effect than that of either drug alone. The implications of this study warrant added caution when patients treated with these drugs undergo abdominal aortic surgery.

Comparison of the antianginal efficacy of four calcium antagonists and propranolol in stable angina pectoris

The antianginal effects of propranolol 160 mg/day, diltiazem 240 mg/day, nicardipine 80 mg/day, nifedipine 40 to 80 mg/day and verapamil 320 mg/day were compared in 12 patients with chronic stable angina pectoris using a symptom-limited exercise test. Compared to placebo propranolol and calcium antagonists similarly reduced (p less than 0.001) the frequency of antianginal attacks and nitroglycerin consumption, and increased exercise tolerance and time to greater than or equal to 1 mm S-T segment depression. After propranolol the pressure-rate product at submaximal and maximal exercise was significantly decreased. The calcium antagonists produced a significant reduction in the submaximal pressure-rate product, but no significant change in the peak pressure-rate product. Maximum ST depression was significantly lower after propranolol and was unchanged after the calcium antagonists. None of the drugs caused significant adverse effects. The results indicate that in patients with stable effort angina pectoris, diltiazem, nicardipine, nifedipine and verapamil were as effective as propranolol in improving exercise tolerance and time to ischaemia, and they did not alter the peak pressure-rate product. Different antianginal mechanisms may be operative for the various calcium antagonists.

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

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

Combination therapy with diltiazem and nifedipine in patients with effort angina pectoris

The antianginal effects of diltiazem and nifedipine alone and in combination were evaluated in a double-blind, randomized, placebo-controlled trial in 11 patients (nine men and two women, 57 +/- 8 years old) with stable effort angina. Each patient received placebo, 30 mg of diltiazem, 10 mg of nifedipine, and 30 mg of diltiazem plus 10 mg of nifedipine four times daily for 1 week each. Antianginal efficacy was assessed by means of a treadmill exercise test. The exercise tolerance time was significantly prolonged from 235.1 +/- 52 (placebo period) to 342.2 +/- 101 sec by diltiazem (p less than .01) and to 325.6 +/- 73 sec by nifedipine (p less than .01). The drug combination further prolonged exercise time to 451.1 +/- 103 sec, which was significantly longer than the interval attained with either diltiazem (p less than .01) or nifedipine (p less than .01) alone. The plasma concentration of diltiazem was unaffected by the addition of nifedipine, whereas the plasma nifedipine concentration was significantly increased from 34.8 +/- 11 to 106.4 +/- 37 ng/ml (p less than .001) by the concomitant administration of diltiazem. These data suggest that exercise tolerance in patients with effort angina is increased by the concomitant administration of diltiazem and nifedipine associated with an increase in the nifedipine plasma concentration.

Efficacy of the calcium antagonist isradipine in angina pectoris

Thirty-six patients with chronic, stable angina pectoris were studied during 2-week treatment periods in which they received, in a randomized double-blind, crossover study, a new calcium entry blocking agent, isradipine, 7.5 mg three times daily or placebo. Antianginal efficacy was determined by treadmill exercise testing carried out 3 and 9 hours after drug administration on the final day of each treatment period. During placebo therapy, treadmill exercise time to the onset of angina (P1) and to the development of moderate angina (P2) was similar at 3 and 9 hours and similar to the placebo run-in period. During isradipine therapy, treadmill exercise time 3 hours after dosing was greater than with placebo therapy (P1 312 +/- 23.0 vs. 267 +/- 19.5 seconds, p less than 0.001; P2 410 +/- 20.2 vs. 355 +/- 18.8 seconds, p less than 0.002). Nine hours after drug administration, the results of exercise testing were similar to placebo.

Differential effects of 1,4-dihydropyridine calcium channel blockers: therapeutic implications

Increasing recognition of the importance of calcium in the pathogenesis of cardiovascular disease has stimulated research into the use of calcium channel blocking agents for treatment of a variety of cardiovascular diseases. The favorable efficacy and tolerability profiles of these agents make them attractive therapeutic modalities. Clinical applications of calcium channel blockers parallel their tissue selectivity. In contrast to verapamil and diltiazem, which are roughly equipotent in their actions on the heart and vascular smooth muscle, the dihydropyridine calcium channel blockers are a group of potent peripheral vasodilator agents that exert minimal electrophysiologic effects on cardiac nodal or conduction tissue. As the first dihydropyridine available for use in the United States, nifedipine controls angina and hypertension with minimal depression of cardiac function. Additional members of this group of calcium channel blockers have been studied for a variety of indications for which they may offer advantages over current therapy. Once or twice daily dosage possible with nitrendipine and nisoldipine offers a convenient administration schedule, which encourages patient compliance in long-term therapy of hypertension. The coronary vasodilating properties of nisoldipine have led to the investigation of this agent for use in angina. Selectivity for the cerebrovascular bed makes nimodipine potentially useful in the treatment of subarachnoid hemorrhage, migraine headache, dementia, and stroke. In general, the dihydropyridine calcium channel blockers are usually well tolerated, with headache, facial flushing, palpitations, edema, nausea, anorexia, and dizziness being the more common adverse effects.

Calcium channel blockers and cardiac surgery

Calcium channel blockers have an important role in the pharmacotherapy of cardiovascular disorders. These agents act by inhibiting the slow inward current into excitable cells, exert direct negative inotropic, chronotropic, and dromotropic activity, and are potent vasodilators. These direct effects are modified by reflex autonomic stimulation and by pathologic states. Serious adverse effects of the calcium channel blockers are most frequently observed in patients with ventricular dysfunction, conduction system disease, or concomitant beta blockade. Calcium channel blockers are indicated in the treatment of angina pectoris, supraventricular arrhythmias, and hypertension. The use of these agents in patients with hypertrophic cardiomyopathy, congestive heart failure, and pulmonary hypertension is investigational. The calcium channel blockers are gaining increased importance in the management of patients undergoing cardiac surgery. Verapamil is indicated for the treatment of post-cardiac-surgical atrial flutter and fibrillation; however, the calcium antagonists are not effective as prophylaxis against postoperative supraventricular arrhythmias. Laboratory studies have shown that drug interactions exist between calcium channel blockers and inhalational anesthetics and nondepolarizing neuromuscular blocking agents; clinical studies have demonstrated that these interactions are rarely significant. Perioperative coronary spasm can be effectively treated with the calcium channel blockers. The timing of calcium antagonist withdrawal prior to surgery is controversial, but continuation of therapy until surgery is usually safe. The clinical significance of platelet function inhibition by the calcium antagonists is unknown. Protection of ischemic myocardium by calcium channel blockers has been demonstrated. Important interactions between the calcium antagonists, hypothermia, and the ionic constituents of cardioplegia require further study before the role of these agents as adjuncts to clinical cardioplegia is defined. Expanded indications and the introduction of new calcium channel blockers will result in increased use of these agents in the future.

Acute hemodynamic effects of intravenous nicardipine in patients treated chronically with propranolol for coronary artery disease

Intravenous nicardipine, 5 mg, was infused over 5 minutes in 2 comparable groups of 8 patients with chronic coronary artery disease but no clinical signs of heart failure. Eight patients had received no previous treatment and served as a control group; 8 other patients had received long-term treatment with large doses of propranolol. The hemodynamic responses to nifedipine were similar in the 2 groups, but was greater in patients taking propranolol. At 10 minutes, systemic vascular resistance decreased by 47% in patients taking propranolol and by 39% in the control group; mean aortic pressures decreased by 25% and 10%; heart rate increased by 23% and 19%; and cardiac index increased by 45% in both groups. At 20 minutes, left ventricular end-systolic volume index decreased by 20% in patients taking propranolol and 15% in the control patients; angiographic stroke index increased by 19% and 8%; left ventricular ejection fraction increased by 22% and 11%; and mean circumferential fiber velocity increased by 46% and 32%. Intravenous nicardipine infusion (5 mg) did not induce negative inotropic effects in patients with chronic coronary heart disease, and no evidence of congestive heart failure was seen, even in patients receiving large doses of propranolol. Nicardipine counteracted the potential deleterious effects of propranolol; increased peripheral vascular resistance and left ventricular stroke work and decreased cardiac output.

A double blind placebo controlled comparison of verapamil, atenolol, and their combination in patients with chronic stable angina pectoris

The efficacy and effect on cardiac function of verapamil 120 mg three times a day and atenolol 100 mg once a day, singly and in combination, were evaluated in 15 patients with angina pectoris. While they were on the combination treatment four patients withdrew from the study. Episodes of angina pectoris and glyceryl trinitrate consumption were significantly reduced only on the combination. On the combination only four patients developed evidence of ischaemia during exercise compared with seven on verapamil and ten on atenolol. ST segment depression at peak exercise, assessed by 16 point precordial mapping, was reduced by all active treatments from 7.1 on placebo to 2.7, 0.9, and 0.6 mm on atenolol, verapamil, and the combination respectively. Mean left ventricular ejection fraction fell significantly from 60% on placebo to 53% on the combination but was unchanged on verapamil and atenolol. Verapamil was an effective alternative to atenolol; the combination was the most effective treatment but was associated with a significant morbidity.

New therapeutic modalities for the treatment of elderly patients with ischemic heart disease

In developing a treatment plan for elderly patients with ischemic heart disease, it is important to appreciate that the pathophysiologic process and aging influence the type of response produced by various drugs. The aging process also alters the way drugs are absorbed, distributed, and eliminated. Each of these variables must be considered in deciding which drugs should be used and how they should be administered.

Changes in haemodynamics and left ventricular function during intravenous nifedipine infusion with and without additional propranolol in patients with coronary artery disease. A randomized, placebo controlled trial

The haemodynamic effects of a combined intravenous treatment of nifedipine and propranolol in ten patients with coronary artery disease compared to a single treatment with nifedipine or placebo were investigated. Nifedipine infusion resulted in a reduction of left ventricular (LV) afterload and LV volumes with an increase in heart rate and EF and no change of the double product, coronary sinus flow, LV diastolic parameters and dp/dtmax. Addition of propranolol lowers myocardial oxygen demand by reducing heart rate and dp/dtmax together with a sustained afterload reduction with no change in LV volumes and EF. The vasodilatatory action of nifedipine pretreatment balanced the negative effects of acute beta-receptor blockade on LV function and allows the reduction of myocardial oxygen demand without a deterioration of LV function.

Alternative medical treatment for patients with angina pectoris and adverse reactions to beta blockers. Usefulness of nifedipine

Although beta blockers are effective for the treatment of angina pectoris, chronic adverse effects produced by these agents--including lethargy, fatigue, and male impotence--can adversely affect patient acceptance and treatment compliance. To assess the clinical effects of switching from anti-anginal treatment with beta blocker only (phase I) to half-dose beta blocker plus the calcium blocker nifedipine (phase II) or nifedipine alone (phase III), 18 patients with chronic stable angina pectoris and side effects to beta blockers were evaluated in a 12-week, open-label trial. Three patients did not complete the study, one secondary to new unstable angina and two secondary to nifedipine side effects. Of the 15 patients completing the trial (13 men and two women; mean age, 54 +/- 5 [SEM] years), all sequentially participated in the one-month phases. Weekly angina frequency assessed from patient diaries was significantly less for treatment with nifedipine only (phase III) as compared with beta blocker (phase I) (1.7 +/- 1 versus 3.9 +/- 1 episodes per week), while phase II was not significantly different. Exercise test time was maintained throughout all phases (phase I, 457 +/- 39; phase II, 458 +/- 40; and phase III, 498 +/- 48 seconds, p not significant). All 15 patients in phase I (100 percent) had side effects to beta blockers, but these side effects were lessened in 12 patients (80 percent) in phase II and 13 patients (86 percent) in phase III, with total alleviation of symptoms in two patients (13 percent) in phase II, and eight patients (53 percent) in phase III. Thus, in patients with side effects to beta blockers, switching to nifedipine is associated with a significant reduction in beta blocker adverse symptoms and equal anti-anginal efficacy.

Advances in calcium blocker therapy

Calcium blockers are drugs that interfere with the entry of calcium ions into cells of a variety of tissues. Three calcium blockers, verapamil, nifedipine, and diltiazem, are currently approved for clinical use in the United States and many others are undergoing clinical trials. All calcium blockers share the effect of dilating blood vessels, although some agents are selective dilators of certain vascular beds, such as the coronary or cerebral circulation. There exist major differences among these drugs in their ability to depress myocardial contraction and inhibit cardiac impulse conduction, as well as other properties. The therapeutic actions of the agents in use, as well as the actions of the investigational calcium blockers, have been reviewed. Although calcium blockers are generally well tolerated and have fewer side effects than many alternative drugs, serious adverse effects are possible in certain clinical settings. The clinical indications for these drugs continue to expand and will likely find many uses in surgical patients, especially in the areas of cardiac surgery, neurosurgery, vascular surgery, and general surgery.