Effect of atrial natriuretic peptide on electrical defibrillation efficacy.
BACKGROUND
In vitro studies have suggested that human atrial natriuretic peptide (ANP) modulates the electrophysiologic properties of myocardial cells. This study assessed whether ANP could influence defibrillation efficacy.


RESULTS
In 35 anesthetized dogs, the transcardiac defibrillation threshold (DFT) as well as hemodynamic and electrophysiologic variables were determined before and during treatment with ANP (n = 11), hydralazine (n = 11), or saline (n = 13). ANP (1.5 microg/kg + 0.2 microg/kg per min) increased the plasma concentration of cyclic GMP (a second messenger for ANP) and significantly decreased aortic blood pressure (mean 100+/-11 mmHg to 83+/-15 mmHg). ANP also prolonged ventricular repolarization (effective refractory period 157+/-7 msec to 165+/-11 msec) and markedly reduced DFT (5.4+/-1.2 J to 3.8+/-0.7 J [P < 0.01]) without changing pulmonary artery pressure or sinus cycle length. Neither saline nor hydralazine (1.5 mg/kg) had a significant effect on DFT (saline 4.7+/-2.1 J to 4.6+/-2.4 J; hydralazine 4.3+/-2.0 J to 4.2+/-1.9 J), although hydralazine caused pronounced hypotension (mean aortic pressure 103+/-9 mmHg to 74+/-13 mmHg).


CONCLUSIONS
These results suggest that ANP increases defibrillation efficacy, and that this effect is not necessarily shared by other vasodilating agents.
Murakawa
Y
Y
Second Department of Internal Medicine, University of Tokyo, Japan. murakawa-2im@h.u-tokyo.ac.jp
Yamashita
T
T
Kanese
Y
Y
Omata
M
M
D000818:Animals; D009320:Atrial Natriuretic Factor / Q000008:administration & dosage / Q000097:blood / Q000627:therapeutic use*; D006152:Cyclic GMP / Q000097:blood; D004285:Dogs; D004554:Electric Countershock; D004562:Electrocardiography; D006439:Hemodynamics / Q000187:drug effects; D006830:Hydralazine / Q000008:administration & dosage / Q000627:therapeutic use; D007262:Infusions, Intravenous; D016896:Treatment Outcome; D014665:Vasodilator Agents / Q000008:administration & dosage / Q000627:therapeutic use; D014693:Ventricular Fibrillation / Q000097:blood / Q000503:physiopathology / Q000628:therapy*
D014665:Vasodilator Agents; D006830:Hydralazine; D009320:Atrial Natriuretic Factor; D006152:Cyclic GMP