Hemodynamic responses to beta-adrenergic blockade with metoprolol and pindolol after coronary artery bypass surgery.

Varying ancillary properties of beta-adrenergic blocking drugs, such as intrinsic sympathomimetic activity or beta 1-selectivity, are known to evoke different hemodynamic effects. These differences may be relevant during hemodynamically unstable conditions. Twenty patients undergoing elective coronary artery bypass surgery were matched in two groups and given either metoprolol tartrate (0.03 mg/kg) or pindolol (0.003 mg/kg) intravenously during recovery from surgery. Heart rate (p less than 0.01) and the rate-pressure product (p less than 0.05) were equally reduced by both beta-blocking drugs. Pindolol also caused a minor decrease in cardiac output (p less than 0.05) and a respective increase in the systemic vascular resistance; all other variables remained stable. It is plausible that in the presence of significant adrenalinemia, which constantly develops after coronary artery surgery, the nonselective pindolol blocks both beta 1-receptors and vascular dilatory beta 2-receptors and thereby increases systemic vascular resistance despite its intrinsic sympathetic activity. Thus, if the use of a beta-blocking agent is considered during the immediate recovery stage following coronary artery bypass surgery, a beta 1-selective drug is more desirable than one with an intrinsic sympathomimetic property.