Right pectoral implantable cardioverter defibrillators: role of the proximal (SVC) coil.
BACKGROUND
Increased defibrillation thresholds (DFTs) with right active pectoral implantable cardioverter defibrillators (ICDs) and/or right proximal coils (SVC) are attributed to poorer vector. However, SVC affects impedance, current flow, and shock waveform phase duration (PD), which exert independent DFT effects.


OBJECTIVE
Compare DFTs and shock characteristics in SVC On with SVC Off in right ICDs.


RESULTS
DFT+ testing (n = 42, 62% males, 62 +/-15 years, left ventricular ejection fraction (LVEF) 26 +/- 11%, ischemic cardiomyopathy 65%, amiodarone 26%) revealed >20% incidence of high DFT (>20J) . Dilated cardiomyopathy and amiodarone increased DFT. Individual impedance variability (25-74 Omega) generated a wide PD range (2.6-8.7 ms). Overall, SVC On reduced impedance by 33% (from 54 +/- 10 to 35 +/- 5Omega, P< 0.0001), and shortened PD (from 5.45 +/- 1.20 to 3.67 +/- 0.74 ms, P< 0.01). SVC On affected DFTs in 19/42 (45%) patients. SVC On was beneficial in 12/19. PD shortened but current flow remained unaltered. (In these, SVC Off impedance was >45Omega and PD >5 ms.) SVC On was detrimental in 7/19 despite increasing current flow. In these, PD shortened excessively (median 2.9 ms) because impedance was low (31 +/- 4Omega). In 3/6 cases with DFTs >20 J in both SVC On and Off, PD optimization reduced DFT. Overall, selection of best SVC configuration or deliberate PD programming yielded DFTs </=20 J in >90% patients, reducing need for system modification to <7%.


CONCLUSIONS
Right pectoral active ICDs have high DFTs. The SVC coil may be detrimental when pulse waveform excessively shortens. Noninvasive maneuvers, for example, SVC and waveform optimization, may improve DFT.
Varma
Niraj
N
University Hospitals of Cleveland and Case Western Reserve University, Cleveland, Ohio, USA. niraj.varma@case.edu
Efimov
Igor
I
D017147:Defibrillators, Implantable; D004567:Electrodes, Implanted; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005260:Female; D006333:Heart Failure / Q000517:prevention & control*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010369:Pectoralis Muscles / Q000601:surgery*; D014159:Transducers