The Annals of Thoracic Surgery, Vol 27, 137-140, Copyright © 1979 by The Society of Thoracic Surgeons
Hemodynamic effects of various modes of cardiac pacing after operation for idiopathic hypertrophic subaortic stenosis
RJ Shemin, WC Scott, DG Kastl and AG Morrow
The hemodynamic effects of varying heart rate and pacing site were studied
in 6 patients with idiopathic hypertrophic subaortic stenosis following
operative relief of outflow obstruction. Ventricular pacing (117 beats per
minute) resulted in a 26% decrease in cardiac output (p less than 0.02), a
54% increase in pulmonary capillary wedge pressure (p less than 0.03), and
a 23% decrease in mean blood pressure (p less than 0.05), compared with
normal sinus rhythm (88 beats per minute). Slow atrial pacing (112 beats
per minute) did not significantly alter any hemodynamic variable compared
with normal sinus rhythm. Rapid atrial pacing (143 beats per minute)
produced a similar degree of hemodynamic impairment as ventricular pacing.
This study demonstrates that ventricular pacing at heart rates commonly
used clinically and rapid atrial rates result in a significant fall in
cardiac output. Preservation of atrial systole at heart rates that allow
adequate diastolic ventricular filling of a hypertrophied, noncompliant
ventricle is stressed. In addition, atrial electrodes are useful to record
atrial electrograms or induce rapid atrial stimulation to treat
supraventricular tachyarrhythmias.