Cardiodynamic and neurohormonal importance of atrial contribution in rate-responsive pacing.
To elucidate the physiologic importance of atrial contribution in recently developed rate-responsive pacing, changes in cardiodynamics and neurohormonal factors were analyzed during exercise in patients with respiratory rate-dependent, rate-responsive atrial (AAIR; n = 6) and ventricular (VVIR; n = 9) demand mode pacemakers implanted for sick sinus syndrome. With increasing pacing rate during bicycle ergometer exercise, the AAIR group had significant increases in cardiac index (p < 0.05), left ventricular ejection fraction (p < 0.05), and ejection (p < 0.05) and peak filling (p < 0.05) rates; however, the VVIR group had a significant decrease in ejection fraction (p < 0.05), and an increase in cardiac index (p < 0.05) that was significantly less than in the AAIR group. At rest, the mean plasma concentrations of atrial natriuretic peptide (p < 0.005) and cyclic guanosine monophosphate (p < 0.05) were significantly greater in the VVIR group than in the AAIR group and normal subjects (n = 8). Atrial natriuretic peptide, norepinephrine, and cyclic adenosine and guanosine monophosphates were significantly greater (p < 0.05) during exercise, and atrial natriuretic peptide was significantly greater in the VVIR group (207.5 +/- 8.3 pg/ml) than in the AAIR group (116.4 +/- 51.5) and normal subjects (30.8 +/- 19.2; p < 0.05); this suggested a further increase in the nonphysiologic atrial overload with VVIR pacing. The data show both the neurohormonal and cardiodynamic importance of atrioventricular synchrony in rate-responsive pacing.
First Department of Internal Medicine, Nippon Medical School, Tokyo, Japan.
Y
Y
Seino
S
S
Shimai
Y
Y
Nagae
C
C
Ibuki
T
T
Takano
S
S
Tanaka
H
H
Hayakawa
D000368:Aged; D016275:Atrial Function; D009320:Atrial Natriuretic Factor / Q000097:blood; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D000242:Cyclic AMP / Q000097:blood; D006152:Cyclic GMP / Q000097:blood; D004837:Epinephrine / Q000097:blood; D004867:Equipment Design; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009638:Norepinephrine / Q000097:blood; D010138:Pacemaker, Artificial; D012804:Sick Sinus Syndrome / Q000097:blood / Q000503:physiopathology* / Q000628:therapy; D016277:Ventricular Function, Left
D009320:Atrial Natriuretic Factor; D000242:Cyclic AMP; D006152:Cyclic GMP; D009638:Norepinephrine; D004837:Epinephrine