A comparison of the hemodynamic effects of prenalterol and isoprenaline in patients with complete heart block.

Prenalterol is a new beta-adrenergic agonist which stimulates mainly beta 1-receptors, in contrast to isoprenaline which stimulates both beta 1- and beta 2-receptors. We studied the hemodynamic effects of prenalterol and isoprenaline in seven patients with complete heart block and idioventricular escape rhythm due to ischemic heart disease. Isoprenaline was given as a continuous infusion at two increasing doses (1.7 micrograms/min and 3.4 micrograms/min each given for 30 min). After the second dose of isoprenaline the cardiac index was increased from 2.27 +/- 0.06 to 3.61 +/- 0.60 1/min/m2, heart rate was increased from 34.1 +/- 1.2 to 50.4 +/- 3.1 beats/min and mean blood pressure was decreased by 12.4 mm Hg. Mean pulmonary artery pressure was increased by 2 mm Hg. Prenalterol was given as two i.v. bolus injections of 3.5 mg and 7.0 mg at 15-min intervals. The first dose of prenalterol increased the cardiac index from 2.22 +/- 0.10 to 2.42 +/- 0.12 and heart rate from 37.0 +/- 1.8 to 40.1 +/- 1.7. Mean blood pressure and mean pulmonary artery pressure were unchanged. The second dose of prenalterol did not change the hemodynamic variables significantly compared to the changes after the first dose. We conclude that isoprenaline is preferable to prenalterol for treatment of complete heart block.