All ETDs from UAB

Advisory Committee Chair

Jack Rogers

Advisory Committee Members

Vladimir Fast

Gregory Walcott

Document Type

Thesis

Date of Award

2019

Degree Name by School

Master of Biomedical Engineering (MBE) School of Engineering

Abstract

Although strong defibrillation shocks can save patients from life-threating tachyarrhythmias, the function of the heart may be compromised. We found in an earlier study that the right ventricular insertion (RVI) is responsible for most of the initial propagation failure (wavebreak) that drives the transition from ventricular tachycardia (VT) to ventricular fibrillation (VF). To determine whether suppression of wavebreak at the RVI region can decrease VF re-occurrence after defibrillation, thereby decreasing the defibrillation shock strength threshold (DFT), a cooling method was developed to impede waves from propagating between the right ventricle (RV) and the left ventricle (LV) through the RVI. The method was applied to 6 normal isolated pig hearts. Defibrillation electrodes were placed at the right atrium and apex. Panoramic optical mapping of wave propagation pre- and post-cooling was used to image postshock wave propagation patterns and to demonstrate the effectiveness of this technique for suppressing RVI propagation. The DFT before and after cooling was found. For near-DFT failed defibrillation shocks, the location of the first wavebreak event in the transition from organized postshock activation to VF was found. Before cooling, we recorded 23 unsuccessful defibrillation events. The first wavebreak event occurred in the RVI region, the RV, or the LV in 16, 6, and 1 event, respectively. For RVI, RV, and LV wavebreaks, the average distance of the wavebreak from the RVI midline was 7.3±3.4 mm, 21.3±4.2 mm, and 38.3 mm, respectively. After cooling, 25 failed defibrillation events were obtained. The first wavebreak occurred at the RVI, RV, or LV in 3, 17, and 5 events, respectively. RVI, RV, and LV wavebreaks were 14.2±0.8 mm, 28.0±8.8 mm, and 31.7±13.8 mm, respectively, from the RVI midline. The proportion of wavebreaks at the RVI differed significantly pre- and post-cooling (P < 0.001, Fisher’s exact test). Before cooling, the first wavebreak occurred an average of 221±117 ms post shock. After cooling, this increased significantly to 307±123 ms (p<0.05). In conclusion, cooling diminished postshock wavebreak events at the RVI region and also increased the latency from shock to first wavebreak. However, data on whether the DFT was changed are equivocal.

Included in

Engineering Commons

Share

COinS