Author + information
- Received October 1, 1982
- Revision received April 14, 1983
- Accepted April 27, 1983
- Published online September 1, 1983.
- Haruaki Nakaya, MD*,
- Ronald W. Millard, PhD*,†,1,
- David A. Lathrop, PhD*,‡,
- Winston E. Gaum, MD, FACC‡,
- Samuel Kaplan, MD, FACC‡ and
- Arnold Schwartz, PhD, FACC*,†
- ↵1Address for reprints: Ronald W. Millard, PhD, Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Mail Location 575, Cincinnati, Ohio 45267.
The calcium channel blocking agent, diltiazem, improves ischemia-induced conduction delays in the canine heart. It is not known, however, if the improvement of myocardial blood flow caused by diltiazem participates in this response. Accordingly, ischemia-induced conduction delay was measured during brief coronary artery occlusion before and after administration of diltiazem in nine anesthetized pigs with fixed heart rate. Acute coronary occlusion prolonged subendocardial (mean ± standard error of the mean, 39.9 ± 3.9 ms) and subepicardial (41.6 ± 4.1 ms) conduction times (time to peak of the bipolar electrogram in each region) by 51 ± 4 and 58 ± 5%, respectively. Regional myocardial blood flow at the ischemic electrode sites was 0.006 ± 0.002 ml/min per g and was unaffected by diltiazem.
Intravenous diltiazem pretreatment (0.01, 0.1, 0.3 and 1.0 mg/kg) 5 minutes before coronary occlusion significantly reduced the ischemia-induced conduction delay in both subendocardial and subepicardial regions during coronary occlusion. The pigs in which ventricular fibrillation occurred within 10 minutes showed a significantly longer conduction delay than that observed in pigs in which ventricular fibrillation occurred later (> 10 minutes).
Thus, the data suggest that the reduction of ischemia-induced conduction delay produced by diltiazem is independent of blood flow changes and, therefore, that diltiazem may have a beneficial antiarrhythmic action.
Present address: Department of Pharmacology, Hokkaido University, School of Medicine, Sapporo 060, Japan.
- Received October 1, 1982.
- Revision received April 14, 1983.
- Accepted April 27, 1983.
- American College of Cardiology Foundation