Verapamil potassium cardioplegia and cardiac conduction

Preservation of adenosine 5'-triphosphate and mitochondrial function during hypercalcemic reperfusion using verapamil cardioplegia

Immediate hypercalcemic reperfusion results in ventricular dysfunction and loss of high-energy stores. The purpose of this study was to evaluate the effect of verapamil cardioplegia on the preservation of myocardial energy stores, mitochondrial ultrastructure, and ventricular dysfunction in the postischemic rat heart during immediate hypercalcemic reperfusion. Rats in the control group were subjected to cardioplegia with potassium, while rats in groups 1 to 3 were subjected to the same with verapamil (0.5 mg/L). The control and group 1 rats underwent normocalcemic reperfusion and groups 2 and 3 rats underwent hypercalcemic reperfusion. Myocardial samples were analyzed for adenosine 5'-triphosphate (ATP) content and mitochondrial ultrastructural damage. Hemodynamic parameters of heart rate, aortic flow (AF), and postischemic rate of aortic pressure change (dP/dT) also were evaluated. Data were analyzed using analysis of variance. The ATP stores were preserved at greater than 100% control levels in hearts subjected to verapamil cardioplegia. There was no evidence of irreversible mitochondrial damage. Heart rate, AF, and dP/dT were significantly (p < 0.05) depressed in hearts subjected to verapamil cardioplegia. This study suggests verapamil cardioplegia preserves ATP and mitochondrial function during immediate hypercalcemic reperfusion but does not improve postischemic hemodynamics.

Reduction of myocardial injury with verapamil before aortic cross-clamping

The effect of verapamil administered before aortic cross-clamping was assessed in 40 patients undergoing elective coronary artery bypass grafting. Myocardial protection consisted of cold blood potassium cardioplegia, topical ice slush, and moderate (28 degrees C) systemic hypothermia. Patients were randomly divided into two groups: group 1 (18 patients) received verapamil (0.1 mg/kg up to 10 mg) intravenously three to five minutes before aortic cross-clamping; group 2 (22 patients) did not (control). Myocardial injury was assessed by cumulative release of the cardiac-specific isoenzyme of creatine kinase (CK-MB) after release of the aortic cross-clamp. Release of CK-MB was significantly lower in the verapamil group (44.9 +/- 6.2 versus 72.2 +/- 9.0 IU at 24.5 hours, p = 0.005). Calculated total infarct size was also lower in the verapamil group (6.0 +/- 0.9 versus 8.9 +/- 1.0 g-Eq, p = 0.035). Individual CK-MB release curves showed either one or two peaks. The two-peak pattern was more frequent in control patients (18 of 21 control patients versus 6 of 18 verapamil patients, p = 0.001) and was associated with a larger infarct size. Atrioventricular pacing was not required in any verapamil patient, but was needed in 1 control patient. We conclude that verapamil administered before aortic cross-clamping protects against myocardial injury during coronary artery bypass grafting with no increase in the incidence of atrioventricular block.

Verapamil. An updated review of its pharmacodynamic and pharmacokinetic properties, and therapeutic use in hypertension

Although verapamil is a well-established treatment for angina, cardiac arrhythmias and cardiomyopathies, this review reflects current interest in calcium antagonists as anti-hypertensive agents by focusing on the role of verapamil in hypertension. Verapamil is a phenylalkylamine derivative which antagonises calcium influx through the slow channels of vascular smooth muscle and cardiac cell membranes. By reducing intracellular free calcium concentrations, verapamil causes coronary and peripheral vasodilation and depresses myocardial contractility and electrical activity in the atrioventricular and sinoatrial nodes. Verapamil is well suited for the management of essential hypertension since it produces generalised systemic vasodilation resulting in a marked reduction in systemic vascular resistance and, consequently, blood pressure. Evidence from clinical studies supports the role of oral verapamil as an effective and well-tolerated first-line treatment for the management of patients with mild to moderate essential hypertension. Clinical studies have shown that verapamil is more effective the higher the pretreatment blood pressure and some authors have found a more pronounced antihypertensive effect in older patients or in patients with low plasma renin activity. Sustained release verapamil formulations are available for oral administration which, as a single daily dose, are as effective in lowering blood pressure over 24 hours as equivalent doses of conventional verapamil formulations given 3 times daily. As a first-line antihypertensive agent, oral verapamil is equivalent to several other calcium antagonists, beta-blockers, diuretics, angiotensin-converting enzyme (ACE) inhibitors and other vasodilators, and is not associated with many of the common adverse effects of these treatments. Verapamil may be preferred as an alternative first-line antihypertensive treatment to diuretics in elderly patients because it has similar efficacy in these patients without causing the adverse effects commonly linked with diuretic treatment. Furthermore, because verapamil does not cause bronchoconstriction, it may be used in preference to beta-blockers in patients with asthma or chronic obstructive airway disease. Reflex tachycardia, orthostatic hypotension or development of tolerance is not evident following verapamil administration. As a second- or third-line treatment for patients refractory to established antihypertensive regimens, verapamil produces marked blood pressure reductions when combined with diuretics and/or ACE inhibitors, beta-blockers and vasodilators such as prazosin.(ABSTRACT TRUNCATED AT 400 WORDS)

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.

Prevention of myocardial electrical activity during ischemic arrest with verapamil cardioplegia

The effect of potassium cardioplegia and potassium cardioplegia containing verapamil hydrochloride on myocardial preservation and electrical activity during prolonged aortic occlusion was examined in 40 adult mongrel dogs. Twenty-four animals (Group 1) received potassium cardioplegia, and 16 animals (Group 2) received potassium verapamil cardioplegia. Potassium or potassium verapamil cardioplegia, 10 ml per kilogram of body weight, was administered after application of the aortic cross-clamp and at 30-minute intervals during the 90-minute arrest. Myocardial temperature was maintained within a range of 8 degrees to 10 degrees C with topical ice saline solution, and electrical activity was monitored with specially designed plunge electrodes. Plunge electrode activity was recorded from the myocardium during arrest in 16 of the 24 animals in Group 1; no electrical activity was present in the animals in Group 2 (p less than .001). The addition of verapamil to potassium cardioplegia increased the tolerance of the myocardium to prolonged ischemia and resulted in less depletion of high-energy phosphate stores and better preservation of mitochondrial ultrastructure and left ventricular function. These data suggest that verapamil augments the preservation provided by potassium cardioplegia by initiating and maintaining a more complete electrical arrest.

Cardioplegia and calcium antagonists: a review

During open-heart operations, periods occur during which the blood supply to the heart is stopped. Myocardial damage can be limited by cooling and induction of electromechanical arrest (cardioplegia). Many animal studies and some clinical trials provide strong evidence for the use of calcium antagonists, such as nifedipine, verapamil hydrochloride, diltiazem hydrochloride, and lidoflazine, as adjuncts to cardioplegia to optimize the protection. Salutary effects of calcium antagonists are discussed in regard to possible mechanism of action, application time, and efficacy during hypothermia. A major conclusion is that virtually no negative effects on cardiac protection have as yet been described in experimental or clinical studies, apart from short-term negative inotropic responses, while there is an increasing body of positive evidence for their efficacy. A new development is the use of these drugs for regional cardioplegia during dilation of coronary arteries (transluminal angioplasty).

Verapamil and myocardial preservation in patients undergoing coronary artery bypass surgery

The value of verapamil hydrochloride as a myocardial preservative when administered prior to or during periods of myocardial ischemia was studied in patients with normal preoperative cardiac function during elective coronary artery bypass grafting. Myocardial protection included systemic hypothermia (28 degrees C) and hypothermic hyperkalemic cardioplegia. Patients were randomly divided into four groups. Group 1 received intravenous administration of verapamil prior to aortic cross-clamping. Group 2 received intravenous verapamil plus verapamil in the cardioplegic solution. Group 3 received verapamil in the cardioplegic solution only. Group 4 was given no verapamil. Oxygen extraction during the reperfusion period was greatest in Group 4. However, the incidence of pacing was 50 to 78% in Groups 2 and 3, who were given verapamil in the cardioplegic solution. These groups also had a greater need for inotropic agents for discontinuation of cardiopulmonary bypass (CPB). This study indicates that verapamil may be a useful pretreatment prior to CPB and ischemia, but is not effective and may even be detrimental when administered during ischemic periods to patients with good myocardial function.

Platelet inhibitors and hydroxyethyl starch: safe and cost-effective interventions in coronary artery surgery

This study evaluated the cost-effectiveness and clinical safety of utilizing hetastarch in pump prime solutions and for colloid replacement postoperatively in conjunction with the platelet inhibitors, aspirin and Persantine (dipyridamole). Sixty-four adult patients undergoing a coronary artery bypass operation were divided into two groups. Group 1 (N = 32) received only Persantine (75 mg three times a day) on the day prior to operation. Group 2 (N = 32) received the same Persantine dose plus aspirin (325 mg). In both groups, aspirin and Persantine were continued postoperatively and hetastarch was used as the colloid of choice. All patients were evaluated for blood loss, coagulation profiles, cost of blood and colloid replacement, and clinical course. Group 2 patients demonstrated significantly greater blood loss (p less than 0.05) but the same postoperative coagulation profiles as Group 1. The transfusion requirement (3.6 units versus 1.3 units) and cost basis ($252 versus $91) for patient care were higher in Group 2. Hetastarch had no effect on blood loss and was not associated with any adverse clinical reactions. Annual institutional savings based on utilization of hetastarch were calculated at $33,500 to $40,500 per 500 patients. We conclude that preoperative administration of aspirin (325 mg) is associated with increased perioperative blood loss and higher patient costs, two variables not demonstrable with Persantine only. Use of hetastarch combined with postoperative platelet inhibition was clinically safe and was a cost-effective method of colloid replacement.