Defibrillation with low voltage using a left ventricular catheter and four cutaneous patch electrodes in dogs.

The purpose of this study was to determine a lower limit of defibrillation thresholds (DFTs) that could be used to evaluate nonthoracotomy lead configurations for implantable defibrillators. A lead configuration that consisted of a left ventricular catheter and four circumferential cutaneous patches was tested because it was hypothesized to create a relatively uniform electric field for defibrillation. In eight anesthetized dogs, three 8F defibrillating catheters with 6 cm platinum clad titanium tips were inserted into the right ventricle (R), right ventricular outflow tract (O), and left ventricle (L). Four cutaneous patch electrodes (4P), each with a surface area of 42 cm2, were placed on the left lateral, right lateral, anterior and posterior thorax. DFTs for ten lead configurations, consisting of different combinations of these electrodes, were evaluated. DFTs were determined by using a modified Purdue technique and applying a single capacitor biphasic shock with both phases 6 ms in duration after 15 sec of electrically induced fibrillation. The L(-)----4P+ configuration produced a lower DFT than R(-)----4P+ (3.2 +/- 1.6 J vs 8.0 +/- 4.2 J, P less than 0.001) with reduced current (2.6 +/- 0.7 A vs 4.1 +/- 1.2 A, P less than 0.001). Lowering the impedance by a mean of 40%, configurations that used four patches produced lower DFTs than those that used a single left lateral patch. The use of an O catheter produced lower DFTs only when used in conjunction with an R catheter.(ABSTRACT TRUNCATED AT 250 WORDS)