The Annals of Thoracic Surgery, Vol 38, 260-264, Copyright © 1984 by The Society of Thoracic Surgeons
Improved cardiovascular hemodynamics with atrioventricular sequential pacing compared with ventricular demand pacing
ST Raza, TZ Lajos, JN Bhayana, AB Lee Jr, AN Lewin, B Gehring and G Schimert
To determine the advantages of atrioventricular (AV) sequential pacing over
ventricular demand pacing, paired cardiovascular hemodynamic studies were
performed in each pacing mode at a constant heart rate. The paired studies
included determination of ejection fraction (EF) by echocardiography and
gated blood pool radionuclide scanning, and of cardiac output (CO) by the
indicator-dilution method. There was no significant difference in EF with
either pacing mode. Determined by echocardiography, EF with AV sequential
pacing was 57% compared with 56% with ventricular demand pacing; by the
gated blood pool method, EF with AV sequential pacing was 58% compared with
57% in the ventricular mode. Significant improvement with AV sequential
pacing was seen in CO (4.75 L/min from 3.75 L/min; p less than 0.01);
stroke volume (58 ml from 48 ml; p less than 0.02); arteriovenous oxygen
content difference (4.9 vol% from 5.6 vol%; p less than 0.01); total
peripheral resistance (1,724 dynes sec cm-5 from 2,025 dynes sec cm-5; p
less than 0.01); and cardiac contractility, as reflected by mixing time
(6.9 seconds from 8.0 seconds; p less than 0.02). No significant changes
were noted in mean arterial or atrial pressure or in systemic oxygen
consumption. In a second group of 6 patients, similar paired studies were
done in AV sequential pacing modes before and after therapeutic reduction
of total peripheral resistance. A significant increase in CO (43%) was
observed following reduction in total peripheral resistance. We conclude
that AV sequential pacing improves CO more effectively than ventricular
demand pacing. Cardiac output can be further enhanced in patients with
congestive heart failure by pretreatment with agents to reduce total
peripheral resistance.
