IMPLANTABLE CARDIOVERTER-DEFIBRILLATORS A ND NONTHORACOTOMY LEAD SYSTEMS - TEMPORAL STABILITY OF DEFIBRILLATION ENERGY-REQUIREMENTS

The vast majority of cardioverter/defibrillator implantations is perfo rmed with nonthoracotomy lead systems. The temporal stability of de fi brillation energy requirements is well established for epicardial defi brillation lead systems, but not for nonthoracotomy lead systems. The defibrillation energy requirements were reevaluated in 30 patients, 13 months after implantation of a cardioverter/defibrillator with a nont horacotomy lead system. The study patients group consisted of 4 female s and 26 males; mean age 60.1 +/- 10.5 years; mean left ventricular ej ection fraction was 32.2 +/- 6.2 %. Coronary artery disease was the un derlying heart disease in 12 patients, dilative cardiomyopathy in 15 p atients, and artificial valve replacement in 3 patients. There was no clinical progression in the underlying heart disease between defibrill ator implantation and control measurements; left ventricular ejection fraction was unchanged (32.2 +/- 6.2 vs. 32.3 +/- 6.4 %); no changes o ccurred regarding patients' clinical status. In 27/30 patients the def ibrillation threshold at defibrillator implantation could be reconfirm ed at control measurements. The mean defibrillation energy/requirement s at implantation (14.4 +/- 4.8 Joules) were unchanged compared to con trol measurements (14.4 +/- 4.6 Joules). A temporal stability of defib rillation energy requirements could be established for the monophasic (n = 15; 18.0 +/- 4 vs. 18.1 +/- 3.4 Joules) as well as for the biphas ic waveform (n = 15; 11.1 +/- 3.4 vs. 11.5 +/-:2.9 Joules). The result s of intraoperative defibrillation thresholds measurements are predict ive for chronic defibrillation energy requirements in patients with no nthoracotomy lead systems.