Prospective Randomized Comparison of Two Defibrillation Safety Margins in Unipolar, Active Pectoral Defibrillator Therapy

Abstract

Various techniques are used to establish defibrillation efficacy and to evaluate defibrillation safety margins in patients with an ICD. In daily practice a safety margin of 10 J is generally accepted. However, this is based on old clinical data and there are no data on safety margins using current ICD technology with unipolar, active pectoral defibrillators. Therefore, a randomized study was performed to test if the likelihood of successful defibrillation at defibrillation energy requirement (DER) + 5 J and + 10 J is equivalent. Ninety-six patients (86 men; age 61.0 +/- 10.3 years; ejection fraction 0.341 +/- 0.132; coronary artery disease [n = 65], dilated cardiomyopathy [n = 18], other [n = 13]) underwent implantation of an active pectoral ICD system with unidirectional current pathway and a truncated, fixed tilt biphasic shock waveform. The defibrillation energy requirement (DER) was determined with the use of a step-down protocol (delivered energy 15, 10, 8, 6, 4, 3, 2 J). The patients were then randomized to three inductions of ventricular fibrillation at implantation and three at predischarge testing with shock strengths programmed to DER + 5 J at implantation and + 10 J at predischarge testing or vice versa. The mean DER in the total study population was 7.88 +/- 2.96 J. The number of defibrillation attempts was 288 for + 5 J and 288 for + 10 J. The rate of successful defibrillation was 94.1% (DER + 5 J) and 98.9% (DER + 10 J; P < 0.01 for equivalence). Charge times for DER + 5 J were significantly shorter than for DER + 10 J (3.65 +/- 1.14 vs 5.45 +/- 1.47 s; P < 0.001). A defibrillation safety margin of DER + 5 J is associated with a defibrillation probability equal to the standard DER + 10 J. In patients in whom short charge times are critical for avoidance of syncope, a safety margin of DER + 5 J seems clinically safe for programming of the first shock energy.

Dual- versus single-coil implantable defibrillator leads: review of the literature

“…Regarding the multiple factors influencing defibrillation efficacy and the inconsistency in testing protocols, these data should be interpreted with caution. There are no data showing that unipolar defibrillation is associated with reduced defibrillation energy safety margin compared to dual-coil lead systems in clinical practice [29,30].…”

“…The reproducibility of successful conversion of induced VF episodes with unipolar defibrillation systems were studied by Carlsson et al [29]. The mean DFT in 96 patients was 7.9 ± 3 J. Two-hundred eighty-eight defibrillation attempts were performed using a defibrillation energy of DFT ?…”

“…However, a significant difference in DFT between singleand dual-coil lead systems was reported in only four of seven randomized studies (Table 1), resulting in maximal improvement in mean DFT of 20%. With regards to safety margins [29,30], temporal stability of DFT [31] and the differences in the tested defibrillation waveforms and used testing protocols, the DFT difference between single-and dual-coil lead systems may have limited clinical relevance.…”

Ist die DFT-Testung noch ein Muss?

“…Ergaben frühe klinische Untersuchungen den Hinweis auf eine gesteigerte Mortalität bei Patienten mit erhöhten Defibrillationsschwellen [6,7,16,24], so konnten Untersuchungen unter Verwendung moderner Defibrillatorsysteme keinen Einfluss der Defibrillationseffektivität auf die Prognose von ICD-Patienten zeigen [3,26,28]. Technologischer Fortschritt führte zu einer signifikanten Verbesserung der Defibrillationseffektivität [2,4,12,21]. Die Frage bleibt, welches Implantationskriterium eine klinisch ausreichende zukünftige Defibrillationssicherheit garantiert.…”

“…Moderne pektoral implantierte transvenöse Defibrillatorsysteme mit biphasischen Schockformen erreichen unter einem strikten intraoperativen Testprotokoll effektive Defibrillationen in einem Energiebereich von 8-10 J [3,4,11,12,20,21], deren zeitliche Stabilität wiederholt belegt werden konnte [10-12, 20, 23, 34]. Nach einem "step-down"-DFT-Protokoll bestimmte Defibrillationsschwellen erreichen mit Sicherheitsmargen von +5 J und +10 J Defibrillationswahrscheinlichkeiten von 94% und 99% [4].…”