CORONARY ARTERY CIRCUMFERENTIAL WALL STRESS 11@"; REDUCED MORE BY ESMOLOL THAN NICARDIPINE.
M.J.A. Williams*, C.J.S. Low, G.T. Wilkins. R.A.H. Stewart. Department of Medicine, University of Otago, Dunedin, New Zealand.
Beta blockers reduce mortality in patients with coronary heart disease. It has been reported that short acting dihydropyridine calcium channel blockers may increase the risk of myocardial infarction or death. The aim of this study was to compare the effects of acute administration of nicardipine, a dihyrdropyridine calcium channel blocker, and the P- blocker esmolol on coronary artery peak circumferential wall stress, a determinant of atherosclerotic plaque rupture.
Methods: Coronary intravascular ultrasound studies were performed in 20 subjects with coronary artery disease before and after double blind randomisation to either intravenous esmolol (10) or nicardipine (10) titrated to decrease systolic blood pressure by 20 mmHg. Peak coronary stress was calculated as the product of peak systolic pressure and arterial radius divided by arterial wall thickness. An index of coronary stress was calculated as peak systolic stress/beat x heart rate.
Results: Baseline characteristics were similar for the two groups.
. Mean % change from baseline (95% Cl)
Nicardipine Esmolol p________
heart rate 17.9 (10.1 to 25.6) -7.0 (-2.8 to - 1 1. 3) .0002
artery radius 4.8 (3.4 to 6.2) -2.8 (-1.5 to -4.0) .0002
peak stress -8.1 (-5.8 to -10.4) -18.1 (-15.4 to -20.8) .0005
stress index 8.5 (-0.4 to 17.3) -24.0 (-21.3 to -26.7) .0003
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Conclusions: Esmolol reduced peak coronary stress more than nicardipine for a similar reduction of blood pressure. The stress index, which adjusts for change in heart rate, increased after nicardipine but decreased after esmolol. These different effects on wall stress may influence the risk of plaque rupture and acute coronary events.
