The effect of polarity of the initial phase of a biphasic shock waveform on the defibrillation threshold of pectorally implanted defibrillators.
The effect of initial phase polarity on the DFT of two pectorally implanted biphasic ICDs was tested in a randomized, prospective manner at the time of implantation. Twenty-two consecutive patients with VT-VF who received either the Medtronic PCD 7219C Jewel device (10 patients) or PCD 7219D Jewel device (12 patients) were studied. DFT testing was performed in a standard step-down manner. Both initial phase polarities--initial defibrillation current flowing from active can/SVC coil +/- subcutaneous patch) to the RV coil (RV coil to active can/SVC (RV+)--were tested in random order. The mean DFT achieved with RV+ compared with RV-was lower for the 7219C patient group (6.6 +/- 3.1 vs 10.8 +/- 5.5 J; P = 0.007). A similar trend was observed for the 7219D group, though the difference did not reach statistical significance (12.0 +/ 4.0 vs 16.3 +/- 7.3 J; P = 0.07). Seven of the 10 patients in the 7219C group had a lower DFT with RV+, while the initial phase polarity made no difference in 3. In the 7219D group, 7 patients had a lower DFT using RV+, 2 patients had a lower DFT using RV-, and the initial phase polarity made no difference in 3. In conclusion, this study demonstrates that changing the polarity of the initial phase of a biphasic shock waveform can have a significant impact on the DFT achieved at the time of ICD implantation.
Keelan
E T
ET
Electrophysiology Laboratory, Milwaukee Heart Institute of Sinai Samaritan Medical Center, Wisconsin, USA.
Sra
J S
JS
Axtell
K
K
Maglio
C
C
Underwood
R D
RD
Desphande
S
S
Biehl
M
M
Dhala
A
A
Blanck
Z
Z
Jazayeri
M R
MR
Akhtar
M
M
D000368:Aged; D017147:Defibrillators, Implantable; D004554:Electric Countershock / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D011446:Prospective Studies; D017180:Tachycardia, Ventricular / Q000628:therapy; D013909:Thorax; D014693:Ventricular Fibrillation / Q000628:therapy