Discrepancies in these trials could also be explained by the differences in the beta-blockers studied. Most of the positive experience with the use of beta-blockers in CHF has been with metoprolol, a cardioselective agent, or with beta-blockers that possess additional vasodilatory properties (ie, bisoprolol, bucindolol, carvedilol). Nonselective beta-blockers were not recommended for heart failure because there was concern that peripheral beta-2 blockade and the unopposed alpha-mediated vasoconstriction would adversely affect cardiac contractility. This was supported by the experiences ofthe initial investigators, who found that low dose propranolol was poorly tolerated in patients with heart failure. buy ortho tri-cyclen online
In addition, there is a change in the ratio of myocardial beta-1 to beta-2 receptors from 80:20 in the normal heart to 60:40 in the falling heart . With increasing dependence on beta-2 receptors in heart failure, beta-blockers with intrinsic sympathomimetic activity (acebutolol, oxprenolol, pindolol) may also result in cardiac decompensation due to down-regulation of these beta-2 receptors . Many of the negative beta-blocker trials, in fact, used beta-blockers with ISA.