Related Experiment Videos
Acute and chronic effects of diltiazem on A-V conduction at rest and during exercise
Insights
Diltiazem, a calcium channel blocker, showed minimal acute effects on heart rhythms during exercise. Chronic use at higher doses slightly prolonged resting PR intervals in patients with coronary artery disease.
Area of Science:
- Cardiology
- Clinical Pharmacology
- Electrophysiology
Background:
- Diltiazem is a calcium channel blocker that inhibits calcium ion influx through slow channels.
- Understanding its electrocardiographic (ECG) effects at rest and during exercise is crucial for patient management.
- Previous research on diltiazem's cardiac electrophysiological impact, particularly during exertion, requires further elucidation.
Purpose of the Study:
- To evaluate the acute and chronic electrocardiographic (ECG) effects of diltiazem.
- To assess these effects both at rest and during symptom-limited exercise.
- To investigate dose-dependent responses to chronic diltiazem administration.
Main Methods:
- Acute study: 16 patients (coronary artery disease/hypertrophic cardiomyopathy) underwent exercise testing before and after a 120 mg oral diltiazem dose.
- Chronic study: 10 coronary artery disease patients received placebo and diltiazem (120, 180, 240 mg/day) or placebo in a double-blind crossover design.
- Symptom-limited upright exercise testing was performed weekly throughout the chronic study.
Main Results:
- Acutely, diltiazem did not significantly alter mean PR, QRS, or QTc intervals or heart rate at rest or peak exercise.
- Isolated cases showed diltiazem slowing ventricular response in atrial fibrillation and causing transient Mobitz I block.
- Chronically, only the 240 mg/day dose significantly prolonged the resting PR interval (p < .005).
Conclusions:
- Diltiazem exhibits minimal acute electrocardiographic changes at rest and during exercise in patients with CAD and HCM.
- Chronic administration, particularly at higher doses (240 mg/day), may lead to a slight prolongation of the resting PR interval.
- These findings suggest a generally well-tolerated electrophysiological profile for diltiazem within the studied parameters.
Abstract:
The acute and chronic electrocardiographic effects of diltiazem, a drug which inhibits calcium passage through slow channels, were examined both at rest and during symptom-limited exercise. In the acute study, 12 patients with coronary artery disease (CAD), three patients with hypertrophic cardiomyopathy (HCM), and one patient with both CAD and HCM performed symptom-limited upright exercise prior to and one hour after receiving 120 mg oral dose of diltiazem. In the chronic study, three dose levels of diltiazem (120 mg/day, 180 mg/day, 240 mg/day) were compared with placebo in ten patients with CAD. Each patient received one week of placebo followed by placebo or diltiazem in a double-blind random cross-over fashion, so that each patient received four weeks of placebo and three weeks of diltiazem, one week at each dose level. Each week, symptom-limited upright exercise testing was performed. In the acute study, diltiazem did not significantly affect the mean PR, QRS, QTC intervals or the heart rate at rest or at maximal exercise. In one patient, diltiazem markedly slowed the ventricular response to atrial fibrillation and in another patient, provoked transient Mobitz I block. In the chronic study, the only significant difference observed was a prolongation of the resting PR interval on the 240 mg/day dose schedule (p less than .005).