Effect of diltiazem on silent ischemic episodes, plasma bradykinin and prostaglandin metabolism

Effect of carteolol on silent myocardial ischemia, variability in heart rate, and the pain-modulating system

To investigate the effects of carteolol, which is a nonselective beta-adrenergic agent with intrinsic sympathomimetic activity, on silent myocardial ischemia, exercise-induced myocardial ischemia, indexes of heart rate variability, and pain-modulating system, 20 patients (mean 60 +/- 9 years) with chronic stable angina underwent exercise treadmill testing and 24-hour ambulatory electrocardiographic monitoring during 2 weeks of carteolol administration (15 mg/day) in a double-blind, placebo-controlled design. Plasma levels of beta-endorphin and bradykinin and electrical pain stimulation to the skin were measured at rest and peak exercise. Indexes of heart rate variability of both time-domain and frequency-domain analysis were derived from 24-hour ambulatory electrocardiographic monitoring. Carteolol decreased maximal heart rate responses to daily activities during ambulatory monitoring and significantly reduced the median frequency and duration of silent myocardial ischemic episodes (from 1.0 to 0.0 events/24 hr and from 16 to 0 min/24 hr, respectively). Carteolol significantly decreased the rate-pressure product at rest and during exercise with improving maximal ST segment depression, suggesting amelioration of exercise-induced myocardial ischemia. Carteolol did not significantly affect plasma levels of beta-endorphin and bradykinin or pain threshold. It significantly decreased some indexes (standard deviation of all normal sinus R-R intervals in the entire 24-hour recording and standard deviation of the mean of all 5-minute segments of normal R-R intervals of a 24-hour recording) of heart rate variability. These results suggest that carteolol may reduce total myocardial ischemic burden by the reduction of cardiac oxygen demand during daily activities and exercise stress, while not affecting plasma levels of beta-endorphin, bradykinin, and pain threshold. Because carteolol tended to decrease indexes of heart rate variability, significant caution might be necessary in prescribing the beta-blocking agents with intrinsic sympathomimetic activity like carteolol to patients with potential serious arrhythmia.

Effects of intracoronary diltiazem on certain hemostatic parameters during acute myocardial infarction in swine

Controversy currently exists regarding the use of diltiazem in the treatment of acute myocardial infarction (AMI). due to conflicting results from clinical trials and animal studies. The purpose of this project was to evaluate the changes in the hemostatic profile during AMI following low dose intracoronary diltiazem infusion. Fourteen Yorkshire swine underwent thoracotomy and 50 min LAD occlusion, followed by 3 h of reperfusion. The first group (n = 8) received 2.5 mg of diltiazem intracoronary at a rate of 5.6 micrograms kg min-1 at the onset of reperfusion. The second group (n = 6) received 0.9% saline intracoronary at the onset of reperfusion and served as the control. The dynamics of plasma antithrombin-III (AT-III), Protein C, total Protein S, fibronectin, endothelin-1 (ET-1), and the stable metabolites of thromboxane (TxB2) and prostacyclin (6-keto-PGF1a) were determined at baseline, then twice during occlusion and finally three times during reperfusion. Diltiazem infusion resulted in diminished ET-1 (34.5%), fibronectin (23.2%), and TxB2 (35.6%); and elevated Protein C (29.3%) when compared with controls. We conclude that intracoronary diltiazem favorable influences hemostasis during AMI in swine. The cardioprotective effects of diltiazem during AMI may be related to the improved hemostatic profile and the reduced incidence of thrombotic complications in such patients.

Serial changes of the plasma prostanoids during myocardial ischemia-reperfusion in swine. Effects of magnesium, diltiazem, and a novel Mac-1 inhibitor

The key role of prostanoids has been recognized in patients with ischemic heart disease. However, serial changes of thromboxane and prostacyclin during both brief and prolonged ischemia-reperfusion are poorly known. These plasma prostanoids were measured during myocardial stunning (MS) and acute myocardial infarction (AMI). The effects of magnesium (Mg), diltiazem, and a Mac-1 inhibitor on the level of the stable metabolites of thromboxane (TXB2) and prostacyclin (6-keto-PGF1 alpha) were elucidated. Forty-nine swine underwent brief (8 min) or prolonged (50 min) coronary artery occlusion followed by reperfusion. The occlusion phase was associated with a decline of plasma prostanoids, followed by a significant increase during reperfusion. Mg and diltiazem similarly affected plasma prostanoids by reducing TXB2 release at 1 h of reperfusion. There was, however, no effect on plasma 6-keto-PGF1 alpha. The Mac-1 inhibition was associated with stabilization of both antagonistic prostanoids as well. Ability of Mg, diltiazem, and leumedins to favorably modulate plasma prostanoid levels have direct clinical implications for the use of these agents in patients with coronary artery disease.

Effects of bepridil on silent myocardial ischemia and eicosanoid metabolism in chronic stable angina pectoris after healing of myocardial infarction

To investigate the effects of bepridil on silent myocardial ischemia and on eicosanoid metabolism, 10 patients with chronic stable angina underwent exercise treadmill testing and 48-hour ambulatory electrocardiographic monitoring both before and after 4 weeks of bepridil administration (150 mg/day). Fasting venous levels of thromboxane B2, 6-keto-prostaglandin F1 alpha, and leukotriene C4 were measured by radioimmunoassay. Bepridil decreased heart rate responses to daily activities during ambulatory monitoring, and significantly (p < 0.05) reduced the median frequency and duration of silent myocardial ischemic episodes (from 5.5 to 0 events/48 hours and from 86 to 0 minutes/48 hours respectively). Bepridil significantly decreased the blood pressure heart rate product at peak exercise and significantly prolonged the mean exercise tolerance time (from 456.6 to 527.0 second). Bepridil also significantly decreased the plasma levels of thromboxane B2 and leukotriene C4 at rest. These results suggest that bepridil may reduce silent myocardial ischemic episodes either by the reduction of cardiac oxygen demand during daily activities and exercise stress, or by controlling coronary and systemic vasomotor tone. The drug also has a salutary effect on eicosanoid metabolism, to which its efficacy on silent myocardial ischemic episodes may be related.