The effects of diltiazem on cardiac function in silent ischemia after myocardial infarction

Silent ischaemia and hypertension

For many years now, silent ischaemia has been recognized as a distinct clinical entity, and its relevance in different patient groups has been established. However, a number of basic questions have not been answered. In explaining the pathophysiology of silent ischaemia, factors affecting both the demand and the supply side are now being recognized. With the exception of certain well-defined groups, it is not clear why some patients are mostly symptomatic, while other patients are predominantly asymptomatic. There appear to be many factors influencing the ischaemic pain threshold. Studies investigating the prevalence of silent ischaemia show a remarkably high prevalence of silent ischaemia in different patient groups. Patients with hypertension but without coronary artery disease form a specific and vulnerable high-risk population that is particularly prone to silent ischaemia. Since changes at the macrovascular level are not responsible, various factors negatively influencing either cardiac supply or demand have been investigated. A reduced coronary reserve is central in explaining the increased prevalence of silent ischaemia in hypertensives. Left ventricular hypertrophy renders meaningful detection of ST segment changes difficult, but a possible solution dealing with this problem is offered by applying more stringent criteria in terms of minimal ST depression in the definition of ischaemia. The treatment of silent ischaemia is largely the same as for angina pectoris, but whether therapy should be directed at elimination of all ischaemic episodes or only of symptomatic episodes depends on further prospective work addressing this question.

Pharmacokinetic and pharmacodynamic interactions between diltiazem and quinidine

OBJECTIVES

To examine the pharmacokinetic and pharmacodynamic interactions between quinidine and diltiazem because both drugs can inhibit drug metabolism.

METHODS

Twelve fasting, healthy male volunteers (age, 24 +/- 5 years; weight, 75 +/- 10 kg) received a single oral dose of diltiazem (60 mg) or quinidine (200 mg), alone and on a background of the other drug, in a crossover study. Background treatment consisted of 100 mg quinidine twice a day or 90 mg sustained-release diltiazem twice a day for 2 day before the study day.

RESULTS

Pretreatment with diltiazem significantly (p < 0.05) increased the area under the curve of quinidine from 7414 +/- 1965 to 11,213 +/- 2610 ng.hr/ml and increased its terminal elimination half-life (t1/2) from 6.8 +/- 1.1 to 9.3 +/- 1.5 hours. Its oral clearance was decreased from 0.39 +/- 0.1 to 0.25 +/- 0.1 L/hr/kg, whereas the maximal concentration was not significantly affected. Diltiazem disposition was not significantly affected by pretreatment with quinidine. Diltiazem pretreatment increased QTc and PR intervals and decreased heart rate and diastolic blood pressure. No significant pharmacodynamic differences were shown for diltiazem alone versus quinidine pretreatment.

CONCLUSION

Diltiazem significantly decreased the clearance and increased the t1/2 of quinidine, but quinidine did not alter the kinetics of diltiazem with the dose used. No significant pharmacodynamic interaction was shown for the combination that would not be predicted from individual drug administration.

Amlodipine in patients with stable angina pectoris treated with nitrates and beta-blockers. The influence on exercise tolerance, systolic and diastolic functions of the left ventricle

The effects of 5 and 10 mg of amlodipine and of placebo were compared in 21 patients with stable angina pectoris and multivessel coronary artery disease. The blind comparison was performed by means of bicycle ergometry and stress echocardiography using esophageal stimulation of the left heart atrium. All patients subsequently received placebo, amlodipine 5 mg and 10 mg for 2 weeks. In bicycle ergometry both doses of amlodipine in comparison with placebo significantly lowered the ST segment depression in lead V5 and prolonged the time to onset of angina. The exercise duration was significantly prolonged only after 10 mg of amlodipine. In stress echocardiography 10 mg of amlodipine significantly improved ejection fraction and reduced wall motion score during stimulation and increased peak velocity of relaxation of left ventricular posterior wall at rest and immediately after stimulation. In the patients with left ventricular end-diastolic pressure < or = 20 mmHg, amlodipine reduced the ratio of peak transmitral flow velocity in atrial contraction to that in early diastole (A/E) at rest and shortened deceleration time at rest and immediately after stimulation. Amlodipine in patients with stable angina pectoris significantly improved the exercise tolerance and the function of the left ventricle in a dose-dependent way. Amlodipine was well tolerated.

Silent myocardial ischemia after acute myocardial infarction

Silent ischemia after myocardial infarction has definite prognostic significance but should be interpreted within the context of other prognostic indicators. The rationale for therapeutic intervention is based on the prognostic implications of silent ischemia and the potentially deleterious effect of repeated episodes of ischemia on the integrity of the left ventricle. We measured parameters of ischemia in 20 patients who showed asymptomatic ischemic ST-T changes on exercise testing in the early phase after myocardial infarction. After diltiazem administration, a reduction of exercise-induced ST-T depression from 2.3 +/- 0.8 to 0.7 +/- 0.6 mm (p less than 0.01) occurred, and regional wall-motion score at exercise, determined by radionuclide angiography, improved significantly (p less than 0.02). These and other observations warrant further studies in which the duration, severity and frequency of the ischemic episodes should be quantified and correlated with prognosis after myocardial infarction.