Pronounced increase in defibrillation threshold associated with pacing-induced cardiomyopathy in the dog

• Published in: The American heart journal Vol. 127; no. 2; pp. 366 - 376
• Main Authors: LUCY, S. D, JONES, D. L, KLEIN, G. J
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier 01.02.1994
• Subjects: Anesthesia. Intensive care medicine. Transfusions. Cell therapy and gene therapy; Animals; Biological and medical sciences; Body Weight; Cardiac Output - physiology; Cardiac Output, Low - blood; Cardiac Output, Low - physiopathology; Cardiac Pacing, Artificial; Cardiomegaly - blood; Cardiomegaly - physiopathology; Cardiomyopathies - blood; Cardiomyopathies - etiology; Cardiomyopathies - physiopathology; Dogs; Electric Countershock - methods; Electric Stimulation; Emergency and intensive cardiocirculatory care. Cardiogenic shock. Coronary intensive care; Intensive care medicine; Medical sciences; Norepinephrine - blood; Organ Size; Pacemaker, Artificial; Ventricular Fibrillation - physiopathology; Ventricular Fibrillation - therapy; Ventricular Pressure - physiology; Heart; Heart failure; Fissipedia; Intensive cardiocirculatory care; Carnivora; Instrumentation therapy; Cardiovascular disease; Threshold energy; Instrumental stimulation; Vertebrata; Experimental disease; Mammalia; Efficiency; Heart disease; Animal; Technique; Defibrillation; Dog; Hypertrophy
• ISSN: 0002-8703; 1097-6744

Progressive changes in myopathology after implantation of an automatic defibrillator could compromise device efficacy. The influence of heart failure development on the defibrillation threshold was evaluated by means of a rapid ventricular pacing model of heart failure in dogs. After transvenous pacemaker lead implantation, adult mongrel dogs were randomly assigned to either the control (n = 7) or rapidly paced group (240 beats/min, n = 6). Seventeen days after implantation, triplicate determinations of the defibrillation threshold were made with three epicardial electrodes. The average defibrillation threshold was four times higher in the rapidly paced group, 13.3 +/- 2.0 joules (mean +/- SEM), than in the control group, 3.3 +/- 0.7 joules (p < 0.01), and was significantly correlated with ventricular weight (r = 0.70, p < 0.01). Both defibrillation threshold energy per gram of ventricle and ventricular weight corrected for body weight were significantly higher in rapidly paced dogs compared with control dogs. It was concluded that myocardial hypertrophy and heart failure may profoundly increase defibrillation energy requirements.