The hemodynamic effect of slowing the heart rate by paired or coupled stimulation of the atria

Abstract

The effect on cardiac output and arterial pressure of slowing the heart rate below the sinus rate by paired and coupled stimulation of the atria, and of increasing the heart rate above the sinus rate by single pacing of the atria, was tested in 11 patients. When the heart rate was slowed by coupled or paired stimulation of the atria, the second of each of a pair of atrial impulses was blocked at the A-V node and ventricular activation was unaltered. In patients with sinus rhythm, coupled and paired stimulation of the atria is a safe method for slowing the heart rate. There was no significant change in the external work performed by the heart when the heart rate was decreased below the sinus rate as much as 45 per cent or increased above the sinus rate as much as 50 per cent.