Reduction in Defibrillation Threshold Using an Auxiliary Shock Delivered in the Middle Cardiac Vein

Abstract

Defibrillation in the middle cardiac vein (MCV) has been shown to reduce ventricular defibrillation thresholds (DFTs). Low amplitude auxiliary shock (AS) from an electrode sutured to the left ventricle at thoracotomy have also been shown to reduce DFT if delivered immediately prior to a biphasic shock (between the ventricular RV and superior vena caval (SVC) electrodes). This study investigates the impact on DFT of an AS shock from a transvenously placed MCV lead system. A standard defibrillation electrode was positioned in the RV in eight anesthetized pigs (35-43 kg). A 50 x 1.8-mm electrode was inserted in the MCV through an 8 Fr angioplasty guide catheter. A 150-V (leading edge) monophasic AS was delivered (95 microF capacitor) from the MCV-->Can with three different pulse widths (3, 5, 7 ms). A primary biphasic shock (PS) (95 microF capacitor, phase 1: 44% tilt, 1.6-ms extension and phase 2: 2.5-ms fixed duration) was delivered from the RV-->Can +/- AS. The four configurations were randomized and DFTs (PS + AS) assessed using a modified binary search. Ventricular fibrillation (VF) was induced with 60 Hz AC followed 10 seconds later by the test shock. The DFTs were compared using repeated measures analysis of variance (ANOVA). All configurations incorporating AS produced significant (P < 0.05) reduction in the DFT compared to no AS (13.8 +/- 7.4 J). There was no difference in the efficacy of differing pulse widths (P > 0.05); 3 ms (11.0 +/- 5.4 J), 5 ms (11.5 +/- 6.0), and 7 ms (10.6 +/- 5.3 J). In conclusion, delivering an AS from a transvenous lead system deployed in the MCV reduces the DFT by 23% compared to a conventional RV-->Can shock alone.

Incidence and clinical predictors of low defibrillation safety margin at time of implantable defibrillator implantation

“…A distal shock coil far from apex may elevate DFTs [41,42], and implanting the RV lead near septum and apex may lower DFTs [43][44][45]. Adding a shock coil in the middle cardiac vein [46][47][48][49][50] or azygous vein or implanting a subcutaneous array electrode [51][52][53][54] may be a more successful strategy for low DSM patients who failed to convert ventricular fibrillation with maximum delivered energy, especially in right-sided implant patients. The extra shock coil and subcutaneous array can substantially improve the shocking vector or waveform to obtain an adequate DSM.…”

Investigation of Coronary Venous Anatomy by Retrograde Venography in Patients With Malignant Ventricular Tachycardia

“…The MCV and AIV have been used as conduits for the passage of mapping catheters in connection with different ablation procedures 3,4 and for defibrillation lead placement, 5,7 but neither the MCV nor the AIV seems to be useful for pacing the LV, inasmuch as hemodynamic improvement has not been reported for leads positioned in these veins. 2 …”

“…1,2 The coronary venous system has also been used for radiofrequency catheter ablation, 3 mapping, 4 and defibrillation. [5][6][7] The main purpose of the present study was to investigate the coronary venous system in patients with heart disease and malignant ventricular tachyarrhythmias by means of retrograde venography. The availability of veins for potential placement of a lead was assessed.…”

Examination of a Middle Cardiac Vein Defibrillation Coil as Stand‐Alone Anode, Auxiliary Anode, and Bystander Electrode in a Transvenous Defibrillation Circuit

“…The middle cardiac vein has been demonstrated in animal 6,7 and human studies as a site with the potential to yield a low defibrillation threshold (DFT) through a lead placed transvenously. Previous investigations have compared the middle cardiac vein as a sole anode or auxiliary anode with a conventional right ventricular (RV) anodal defibrillation 6–10 . A direct comparison of defibrillation characteristics between a middle cardiac vein anode and an middle cardiac vein plus RV anode using low impedance coils and shocking to a superior vena cava (SVC) plus active housing cathode has not been undertaken.…”