Pa. Friedman et Ms. Stanton, THORACOTOMY ELEVATES THE DEFIBRILLATION THRESHOLD AND MODIFIES THE DEFIBRILLATION DOSE-RESPONSE CURVE, Journal of cardiovascular electrophysiology, 8(1), 1997, pp. 68-73
Thoracotomy Elevates the Defibrillation Threshold. Introduction: Despi
te innovations in nonthoracotomy defibrillation systems, thoracotomies
are still required in some clinical settings and are utilized in many
animal-based research protocols, The effect of a thoracotomy on defib
rillation energy, however, has not been well characterized, Methods an
d Results: Ten dogs in the immediate testing group underwent defibrill
ation testing immediately following a thoracotomy; another ten dogs in
the delayed testing group were given 48 to 72 hours of recovery befor
e defibrillation testing, A right ventricular endocardial coil to cuta
neous thoracic patch biphasic system was used, At the time of defibril
lation testing, the immediate testing group had a faster mean heart ra
te (144.7 +/- 30.2 vs 105.8 +/- 17.5 beats/min, P < 0.01), higher mean
pulmonary artery pressures (systolic: 18.14 +/- 9.18 vs 11.28 +/- 6.4
6 mmHg, P = 0.1; diastolic: 6.59 +/- 2.88 vs 3.89 +/- 1.75 mmHg, P < 0
.05), and higher mean defibrillation shock impedance (89.0 +/- 11.6 vs
70.9 +/- 7.3 Omega, P < 0.002) than the delayed group, The mean ED(50
) (energy with a 50% success rate) was significantly higher in the imm
ediate group than in the delayed group (26.9 +/- 14.9 vs 14.2 +/- 6.9
J, P < 0.05), and the slopes of the dose-response curves were signific
antly different (P = 0.03). Conclusion: In a right ventricular endocar
dial to cutaneous patch system, thoracotomy significantly and transien
tly increased the defibrillation threshold and modified the defibrilla
tion dose-response curve.