INCREASE OF VAGAL ACTIVITY IN PATIENTS WI TH CORONARY-ARTERY DISEASE AFTER ADMINISTRATION OF THE CALCIUM-CHANNEL BLOCKER DILTIAZEM

The effects of the calcium channel blockers diltiazem on the parasympa thetic nervous system were studied by using spectral analysis of heart rate variability, and were compared with the effects of the beta-rece ptor blocker metoprolol. The area under the curve of the high-frequenc y range (f = 0.18-0.35 Hz) during controlled respiratory rate (f = 0.2 5 Hz) was used as a quantative index of parasympathetic activity. Twen ty-four male patients with proven coronary artery disease and normal l eft ventricular function (LVEF > 60 %) were studied 2 weeks after chro nic treatment with diltiazem (3 x 60 mg daily) or metoprolol (3 x 50 m g daily) before and after administration of the drug. Twelve patients received diltiazem and 12 patients metoprolol. After administration of diltiazem the peripheral systolic blood pressure was reduced, but the parasympathetic activity was significantly higher than compared with the initial measurement. The same effect was seen for metoprolol, but a significant lower heart rate was present after administration. The r elative area under the high-frequency range significantly increased at rest, by 110 % after diltiazem and 70 % after metoprolol. Diltiazem a nd metoprolol enhance the vagal influence at the heart, thereby leadin g to an enhancement of barosensitivity and of the respiratory sinus ar rhythmia. This action may contribute to the beneficial effects of both drugs in patients with coronary artery disease.