Effects of nisoldipine therapy on myocardial perfusion and neuro-hormonal status in patients with severe ischaemic left ventricular dysfunction

Discovery and Development of Calcium Channel Blockers

In the mid 1960s, experimental work on molecules under screening as coronary dilators allowed the discovery of the mechanism of calcium entry blockade by drugs later named calcium channel blockers. This paper summarizes scientific research on these small molecules interacting directly with L-type voltage-operated calcium channels. It also reports on experimental approaches translated into understanding of their therapeutic actions. The importance of calcium in muscle contraction was discovered by Sidney Ringer who reported this fact in 1883. Interest in the intracellular role of calcium arose 60 years later out of Kamada (Japan) and Heibrunn (USA) experiments in the early 1940s. Studies on pharmacology of calcium function were initiated in the mid 1960s and their therapeutic applications globally occurred in the the 1980s. The first part of this report deals with basic pharmacology in the cardiovascular system particularly in isolated arteries. In the section entitled from calcium antagonists to calcium channel blockers, it is recalled that drugs of a series of diphenylpiperazines screened in vivo on coronary bed precontracted by angiotensin were initially named calcium antagonists on the basis of their effect in depolarized arteries contracted by calcium. Studies on arteries contracted by catecholamines showed that the vasorelaxation resulted from blockade of calcium entry. Radiochemical and electrophysiological studies performed with dihydropyridines allowed their cellular targets to be identified with L-type voltage-operated calcium channels. The modulated receptor theory helped the understanding of their variation in affinity dependent on arterial cell membrane potential and promoted the terminology calcium channel blocker (CCB) of which the various chemical families are introduced in the paper. In the section entitled tissue selectivity of CCBs, it is shown that characteristics of the drug, properties of the tissue, and of the stimuli are important factors of their action. The high sensitivity of hypertensive animals is explained by the partial depolarization of their arteries. It is noted that they are arteriolar dilators and that they cannot be simply considered as vasodilators. The second part of this report provides key information about clinical usefulness of CCBs. A section is devoted to the controversy on their safety closed by the Allhat trial (2002). Sections are dedicated to their effect in cardiac ischemia, in cardiac arrhythmias, in atherosclerosis, in hypertension, and its complications. CCBs appear as the most commonly used for the treatment of cardiovascular diseases. As far as hypertension is concerned, globally the prevalence in adults aged 25 years and over was around 40% in 2008. Usefulness of CCBs is discussed on the basis of large clinical trials. At therapeutic dosage, they reduce the elevated blood pressure of hypertensive patients but don't change blood pressure of normotensive subjects, as was observed in animals. Those active on both L- and T-type channels are efficient in nephropathy. Alteration of cognitive function is a complication of hypertension recognized nowadays as eventually leading to dementia. This question is discussed together with the efficacy of CCBs in cognitive pathology. In the section entitled beyond the cardiovascular system, CCBs actions in migraine, neuropathic pain, and subarachnoid hemorrhage are reported. The final conclusions refer to long-term effects discovered in experimental animals that have not yet been clearly reported as being important in human pharmacotherapy.

Metabolic Modulators for Chronic Cardiac Ischemia

Many patients with ischemic heart disease continue to experience anginal symptoms despite revascularization and treatment with antianginal medications. The effectiveness of current anti-ischemic medications is limited by their hemodynamic side effects, such as hypotension and bradycardia, which result in compromised organ perfusion. In this article, we review five novel agents (ranolazine, trimetazidine, L-carnitine, ribose, and dichloroacetate) under investigation for treatment of ischemic heart disease that work by enhancing the efficiency of the myocardium, rather than decreasing its work. This new paradigm promises to eliminate these side effects.

Ranolazine: new approach for the treatment of stable angina pectoris

Myocardial ischemia is a metabolic problem involving reduced delivery of oxygen to cardiac mitochondria, resulting in less ATP formation, acceleration of glycolysis and production of lactate and H+ by the cell. Traditional therapies for ischemia aim at restoring the balance between mitochondrial ATP production and breakdown by reducing the need for ATP via suppression of heart rate, blood pressure and cardiac contractility, or by increasing oxygen delivery via increased myocardial blood flow. Despite optimal treatment with traditional hemodynamically oriented drugs (beta-adrenergic receptor antagonist, Ca2+ channel antagonist and nitrates), many patients continue to suffer from angina. Thus, there is a need for anti-anginal drugs that act directly on cardiomyocytes to lessen the metabolic abnormalities induced by ischemia and reduce the symptoms (chest pain and exercise intolerance). Ranolazine has been demonstrated to improve exercise time to angina or 1 mm of ST-segment depression in a manner similar to currently approved drugs, but without any significant effects on heart rate or blood pressure at rest or during exercise. In two Phase III trials, ranolazine improved exercise tolerance and reduced the frequency of angina attacks in chronic severe angina patients when administered either as monotherapy or on a background of atenolol, amlodinine or diltiazem. At present, ranolazine is under review for US Food and Drug Administration approval and, if approved, it will represent the first drug of its class in the USA.

Management of myocardial ischemia. Is ranolazine needed? For all or some patients with myocardial ischemia?

This editorial refers to 'Should ranolazine be used for all patients with ischemic heart disease or only for symptomatic patients with stable angina or for those with refractory angina pectoris? A critical appraisal' by U Thadani also published in this issue.

Effects of three vasoactive peptides isolated from the plasma of the snake Bothrops jararaca

Incubation of plasma from the snake Bothrops jararaca (BJP) with trypsin generated two hypotensive peptides. The primary structure of the peptides was established for three sequences as: Asn-Pro-Phe-Val-Asp-Ala (fraction 13), Ser-Lys-Pro-Asn-Met-Ser-Asp-Glu-Ser-Leu-Ala-Val-Ala-Ile (fraction 14), Asn-Pro-Phe- Val-Asp-Ala (fraction 15). These peptides display homology with fragments of albumin from Trimeresurus flavoviridis. A bolus intra-arterial injection of the purified or the synthetic peptide produced a strong and sustained vasopressor response in the anaesthetized snake B. jararaca and Wistar rats; this hypotensive effect was also potentiated by captopril, an angiotensin-converting enzyme inhibitor (0.1 mg/kg). The natural concentrations of these peptides in plasma need to be determined and could play a physiological role in snake blood pressure regulation.

Ranolazine, a new antianginal drug

The increasing and unmet social and economic burden of ischemic heart disease calls for new antianginal therapies. Ranolazine, a new antianginal agent, has a different mode of action from existing therapies, which act by decreasing indices of cardiac work. Ranolazine mainly affects the late sodium current across the membrane of cardiomyocytes, inducing a cascade of electrophysiologic and metabolic effects with the potential to reduce the cardiac ischemic burden without significantly changing blood pressure and heart rate. In clinical trials, ranolazine has been demonstrated to exert antianginal and anti-ischemic effects in chronic angina. It improves exercise performance, and decreases angina frequency and nitroglycerin use. Ranolazine is well tolerated at therapeutic doses. Larger studies are needed to explore the effects on hard end-points of morbidity and mortality.

Blood Pressure Reduction and Cardiovascular Prevention: An Update Including the 2003-2004 Secondary Prevention Trials

In a meta-analysis published in June 2003, we reported that new and old classes of antihypertensive drugs had similar long-term efficacy and safety. Furthermore, we observed that in clinical trials in hypertensive or high-risk patients gradients in systolic blood pressure (SBP) accounted for most differences in outcome. To test whether our previous conclusions would hold, we updated our quantitative overview with new information from clinical trials published before 2005. To compare new and old antihypertensive drugs, we computed pooled odds ratios from stratified 2 x 2 contingency tables. In a meta-regression analysis, we correlated these odds ratios with corresponding between-group differences in SBP. We then contrasted observed odds ratios with those predicted from gradients in SBP. The main finding of our overview was that reduction in SBP largely explained cardiovascular outcomes in the recently published actively controlled trials in hypertensive patients and in placebo-controlled secondary prevention trials. The published results suggested that dihydropyridine calcium-channel blockers might offer a selective benefit in the prevention of stroke and inhibitors of the renin-angiotensin system in the prevention of heart failure. For prevention of myocardial infarction, the published results were more equivocal, because of the benefit of amlodipine over placebo or valsartan in 2 trials, whereas other placebo-controlled trials of calcium-channel blockers or angiotensin converting enzyme inhibitors did not substantiate the expected benefit with regard to cardiac outcomes. In conclusion, the hypothesis that new antihypertensive drugs might influence cardiovascular prognosis over and beyond their antihypertensive effect remains unproven. Our overview emphasizes the need of tight blood pressure control, but does not allow determining to what extent blood pressure must be lowered for optimal cardiovascular prevention.

Calcium channel blockers: an update

This paper reviews the current literature pertaining to calcium channel blockers, including their classification, properties, and therapeutic indications, in light of several recent trials that have addressed their safety. Calcium channel blockers are a structurally and functionally heterogeneous group of medications that are used widely to control blood pressure and manage symptoms of angina. They are classified as dihydropyridines or nondihydropyridines. As a class, they are well tolerated and are associated with few side effects. The question of whether they may precipitate cardiovascular events has been largely settled by recent trials, such as the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT), the International Verapamil Slow-Release/Trandolapril Study (INVEST), and the Controlled Onset Verapamil Investigation of Cardiovascular Endpoints (CONVINCE) study, in which no such association was found. Even so, the use of these agents has been linked with an increased risk of heart failure. Thus, long-acting calcium channel blockers may be safely used in the management of hypertension and angina. However, as a class, they are not as protective as other antihypertensive agents against heart failure.

Cardiovascular prevention and blood pressure reduction: a quantitative overview updated until 1 March 2003

BACKGROUND

In a meta-analysis published in October 2001, we reported that new and old classes of antihypertensive drugs had similar long-term efficacy and safety. Furthermore, we observed that in clinical trials in hypertensive or high-risk patients gradients in systolic pressure accounted for most differences in outcome.

OBJECTIVE

To test whether our previous conclusions would hold, we updated our quantitative overview with new information from 14 clinical trials presented before 1 March 2003.

METHODS

To compare new and old antihypertensive drugs, we computed pooled odds ratios from stratified 2 x 2 contingency tables. If Zelen's test of heterogeneity was significant, we used a random effects model. In a meta-regression analysis, we correlated odds ratios with corresponding between-group differences in systolic pressure. We then contrasted observed odds ratios with those predicted from gradients in systolic pressure.

MAIN OUTCOMES

Differences in achieved systolic blood pressure and incidence of total and cardiovascular mortality, cardiovascular events, stroke, myocardial infarction and heart failure. NEW VERSUS OLD DRUGS: In 15 trials, 120 574 hypertensive patients were randomized to old drugs (diuretics or beta-blockers) or new agents [calcium-channel blockers, alpha-blockers, angiotensin-converting enzyme (ACE) inhibitors or angiotensin type-1 receptor (AR1) blockers]. Old and new drugs provided similar protection against total and cardiovascular mortality and fatal plus non-fatal myocardial infarction. Calcium-channel blockers, including (-8%, P = 0.07) or excluding verapamil (-10%, P = 0.02), as well as AR1 blockers (-24%, P = 0.0002) resulted in better stroke prevention than did the old drugs, whereas the opposite trend was observed for ACE inhibitors (+10%, P = 0.03). The risk of heart failure was higher (P < 0.0001) on calcium-channel blockers (+33%) and alpha-blockers (+102%) than on conventional therapy involving diuretics. META-REGRESSION: Between-group differences in achieved systolic pressure ranged from 0.1 to 3.2 mmHg in seven actively controlled trials (73 237 patients), and from 2.1 to 22.1 mmHg in seven studies comparing varying intensities of blood pressure lowering (11 128 patients). For these 14 new trials, we predicted outcome from achieved systolic blood pressure using our previously published meta-regression models based on 30 trials with 149 407 patients. In general, predicted and observed odds ratios were similar. Larger reductions in systolic pressure (weighted mean 1.8 mmHg) in two trials accounted for the advantage of AR1 blockers over conventional therapy in the prevention of stroke. Only for cardiovascular mortality in very old patients (P = 0.02) and for cardiovascular events and myocardial infarction in old Australians (P < 0.05), the observed odds ratios deviated from our predictions based on the gradients in systolic blood pressure.

INTERPRETATION

The hypothesis that new antihypertensive drugs, such as calcium-channel blockers, alpha-blockers, ACE inhibitors or AR1 blockers might influence cardiovascular prognosis over and beyond their antihypertensive effects remains unproven. The finding that blood pressure differences largely accounted for cardiovascular outcome emphasizes the desirability of tight blood pressure control. However, the level to which blood pressure must be lowered to achieve maximal benefit remains currently unknown.

Meta-analysis of efficacy and safety of second-generation dihydropyridine calcium channel blockers in heart failure

Second-generation dihydropyridine calcium channel blockers slightly increase cardiac index, left ventricular ejection fraction, and exercise treadmill tests in patients with chronic heart failure, and do not increase norepinephrine levels; these drugs seem to be safe and beneficial in this category of patients. A 6% reduction in mortality was found, which, although not significantly different from 0%, does indicate that these drugs do not increase mortality in this category of patients.

New Insights into the Therapeutic Mechanism of Action of Calcium Channel Blockers in Salt-Dependent Hypertension: Their Interaction with Endothelin Gene Expression

It appears that the beneficial action of calcium channel blockers (CCBs) in hypertension may be related to short-term and long-term effects. This paper summarises pharmacological studies aiming to characterise those effects. The primary consequence of the short-term effects is the decrease of blood pressure related to a selective interaction of CCBs with calcium channels in hypertensive vessels. The long-term effects may additionally control the disease through prevention of end organ damage, accompanying the interaction of CCBs with the pathways, leading to the re-expression of embryonic genes and to the overactivation of type I collagen gene, which are amplified by a high-salt diet. ET-1 and tumour growth factor beta-1 could be among the main factors activating those pathways. The processes leading to overexpression of those factors and to tissue remodelling may be controlled by lacidipine, independent of the reduction of blood pressure.

The calcium antagonist controversy: the emerging importance of drug formulation as a determinant of risk

Calcium antagonists are one of the widely available classes of antihypertensive agents. Their broad appeal is attributable to several features, including their efficacy, their beneficial characteristics such as metabolic neutrality, and the occurrence of relatively few nuisance-type side effects. Despite these attributes, a number of retrospective analyses have suggested that calcium antagonists may be detrimental and may both promote adverse cardiovascular events and increase the risk of cancer by interfering with cellular apoptosis. On the basis of this and other retrospective analyses, Furberg and Psaty (Am J Hypertens 1996; 9: 122-125) have proposed that the use of calcium antagonists as first-line antihypertensive agents should be discontinued. I have previously countered these allegations and have suggested that they are not relevant to the newer calcium antagonist formulations in current use. It is not widely appreciated that different formulations of the same chemical moiety can produce markedly different hemodynamic and neurohormonal effects, due to differences in the rate of drug delivery into the systemic circulation. During chronic treatment with dihydropyridine calcium antagonists, major fluctuations in blood pressure (rapid onset and offset of antihypertensive effects) during the dosing interval may occur for drugs and formulations that are short acting. In contrast, slow-release formulations of otherwise rapidly absorbed dihydropyridines achieve a more gradual and sustained antihypertensive effect. It is probable that newer calcium antagonist formulations that are truly once daily and do not provoke intermittent sympathetic activation or a cardioacceleratory response will not promote adverse cardiovascular events.

Use of calcium antagonists in patients with ischemic heart disease and systemic hypertension

Ischemic heart disease (IHD) and systemic hypertension commonly coexist in a large number of patients, and the presence of hypertension is a risk factor for worsening IHD. A monotherapy that would effectively treat both is thus an attractive idea, and calcium antagonists have been evaluated in this role. Calcium antagonists exert therapeutic effects through a combination of actions, including systemic and peripheral vasodilation, negative inotropy, and reduced nodal conduction. In randomized, double-blind clinical trials, verapamil compares favorably with propranolol in the alleviation of angina and hypertension. Both diltiazem and nifedipine, as well as long-acting diltiazem, are also effective in treating the combined condition. In addition, each of these drugs enhances exercise tolerance and favors compliance with calcium antagonist therapy. Recent questions regarding the safety of this class of drug have tempered the enthusiasm for their use as first-line therapy in cardiovascular disease. In particular, short-acting dihydropyridine derivatives, including nifedipine and isradipine, may increase cardiovascular morbidity and mortality because of reflex sympathetic stimulation. The results of appropriately controlled, prospective clinical trials will provide more definitive conclusions. For now, we must be cautious in the use of calcium antagonist monotherapy for combined IHD and hypertension.

What does nisoldipine coat core (CC) add to current therapy that is clinically meaningful?

Nisoldipine coat core (CC) is a long-acting dihydropyridine with good tolerability. Ambulatory blood pressure measurements in a large, South African multicenter trial show that it has an excellent trough:peak ratio, and that it reduces the early morning rise in blood pressure without any tachycardia. Nisoldipine CC is an effective antihypertensive agent in both black and nonblack South African ethnic groups. In another South African study, regression of left ventricular hypertrophy was achieved in black patients with severe diastolic hypertension. Safety issues are discussed against the background of the testing of this drug in postinfarct left ventricular dysfunction.

Pharmacological aspects of calcium channel blockers

Calcium channel blockers (CCBs) inhibit voltage-dependent L-type calcium channels. This leads to vascular smooth muscle relaxation and negative inotropic and chronotropic effects in the heart. The latter are counteracted in vivo by a vasodilatation-triggered, baroreceptor-mediated reflex increase in sympathetic tone, resulting in indirect cardiostimulation. The mean vascular/cardiac effect ratios of the first-generation CCBs-verapamil, nifedipine, and diltiazem-are relatively low and amount to approximately 3, 10, and 3, respectively. The pharmacokinetic properties of verapamil, nifedipine, and diltiazem are similar. The drugs are almost completely absorbed after oral administration, but their bioavailability is reduced because of first-pass hepatic metabolism. The onset of action of verapamil, nifedipine, and diltiazem, at least in immediate-release formulations, is relatively fast (0.5-2 hours), and their elimination half-lives range from 2 to 7 hours. The second-generation CCBs (e.g., amlodipine, felodipine, and nisoldipine) have a slower onset of action (due to either intrinsic properties of the drug or a slow-release formulation), a longer duration of action, and greater vascular/cardiac effect ratios. These features may provide therapeutic benefits, for example, a less pronounced increase in sympathetic tone and reflex tachycardia, and reduced likelihood of negative inotropic effects. These agents can therefore probably be used in patients with left ventricular dysfunction.

Nisoldipine CC: efficacy and tolerability in hypertension and ischemic heart disease

Nisoldipine is a second-generation dihydropyridine calcium channel blocker (CCB). It is the most vascular selective of the currently available CCBs, and thus has the capacity to lower blood pressure without affecting the functioning of the myocardium and skeletal muscle, and without producing any negative inotropic effects. Nisoldipine coat core (CC) is an extended-release formulation that allows nisoldipine to be released gradually over 24 hours, minimizing fluctuations in plasma concentration and providing a good trough/peak ratio. It has a slow onset and long duration of action, and ambulatory blood pressure monitoring has demonstrated that its antihypertensive effect is maintained over 24 hours with no evidence of reflex tachycardia, hypotension, or sympathetic neurohormonal activation and no effects on circadian variation. Studies in patients with hypertension have shown that nisoldipine CC provides reductions in blood pressure that are at least equivalent to those seen with diuretics, beta-blockers, angiotensin-converting enzyme inhibitors, and other CCBs, without deleterious effects on metabolic parameters. In particular, it has been found to be effective in elderly patients and in black patients with severe hypertension. The DEFIANT studies have demonstrated that nisoldipine CC improves cardiac function and exercise tolerance in patients recovering from acute myocardial infarction, without increasing the risk of mortality compared with placebo. It also improves exercise performance in patients with stable angina pectoris. Nisoldipine CC is well tolerated in all groups of patients, with the most frequently reported side effects being headache and peripheral edema, which are usually mild and transient.

Clinical application of three-dimensional myocardial imaging: evaluation of efficacy of medical treatment on myocardial perfusion

To investigate the clinical applicability of the three-dimensional (3D) myocardial imaging using a newly developed system (the Application Visualization System-Medical Viewer), thallium-201 myocardial single photon emission computed tomography was performed in 19 patients with previous myocardial infarction before and after treatment with nisoldipine. We have developed a new method for automatically reconstructing 3D imaging for the stereoscopic evaluation of myocardial perfusion. The left ventricular myocardial volume with a radioisotope count > or = 50% of maximum was calculated by using the conventional surface rendering method. With these images, the effect of nisoldipine on myocardial perfusion was assessed and the myocardial volume with a radioisotope count > or = 50% of maximum was compared. In fifteen (88%) of 19 patients, myocardial perfusion increased in the infarct areas after nisoldipine treatment. Nisoldipine significantly increased the myocardial volume with a radioisotope count > or = 50% of maximum from 141 +/- 17 to 153 +/- 18 ml on the stress 3D imagings. These findings indicate that nisoldipine improved myocardial perfusion during exercise. 3D imaging provided stereoscopic assessment of the changes in myocardial perfusion following treatment with nisoldipine and also detected transient enlargement of the left ventricular lumen induced by exercise.