Resolution of high initial epicardial patch defibrillation thresholds following chronic implantation

To determine what effect chronic implantation of automatic implantable cardioverter defibrillator epicardial patch electrodes had on initial high defibrillation thresholds at implant, six patients were studied. There were five men, one woman, mean age 61 years. Three had coronary artery disease and three had dilated cardiomyopathies. Mean ejection fraction was 20%. Two patients underwent concomitant coronary artery revascularization and one underwent mitral valve replacement. No patient was on antiarrhythmic drugs. At the time of initial implant, adequate defibrillating thresholds could not be obtained in any patch configuration despite the use of up to 40 joules. Further testing was precluded in each patient due to the development of profound hypotension (less than or equal to 70 mmHg systolic) that was poorly responsive to pressors. The patch electrodes were then implanted in an arbitrary anterior-posterior position and the leads were tunneled to an abdominal pocket. After 10-15 days (mean 11), the lead ends were exposed and defibrillation testing was performed again. In all six patients, adequate defibrillation thresholds were obtained (mean 18 joules). We conclude that if adequate defibrillation thresholds cannot be obtained at implant and if further testing cannot be performed without jeopardizing the life of the patient, the patch electrodes should be implanted and retesting performed at 10-15 days.