Key result
Progressive left atrial dilatation induced by 6 weeks of rapid ventricular pacing in an ovine model did not significantly alter the mean atrial defibrillation threshold (122 +/- 15 V).
Why the study?
Does left atrial dilatation alter the endocardial atrial defibrillation threshold in an ovine model of pacing-induced dilated cardiomyopathy?
Does left atrial dilatation alter the endocardial atrial defibrillation threshold in an ovine model of pacing-induced dilated cardiomyopathy?
In an ovine model, progressive left atrial dilatation did not significantly alter the minimal energy requirements for successful atrial defibrillation using a coronary sinus/right atrium shock vector.
Answers are grounded in this paper and cite their sources.
Suggests left atrial dilatation may not affect defibrillation thresholds; supports consensus but leaves human translation open.
Left atrial (LA) dilation is a common finding in patients with chronic atrial fibrillation (AF). Progressive dilatation may alter the atrial defibrillation threshold (ADFT). In our study, epicardial electrodes were implanted on the LA free wall and right ventricular apex of eight adult sheep. Large surface area, coiled endocardial electrodes were positioned in the coronary sinus and right atrium (RA). LA dilatation was induced by rapid ventricular pacing (190 beats/min) for 6 weeks and echocardiographically assessed weekly along with the ADFT (under propofol anesthesia). LA effective refractory period (ERP) was measured every 2-3 days using a standard extra stimulus technique and 400 ms drive. The AF cycle length (AFCL) was assessed from LA electrograms. During the 6 weeks of pacing the mean LA area increased from 6.1 +/- 1.5 to 21.3 +/- 2.4 cm2. There were no significant changes in the mean ADFT (122 +/- 15 V), circuit impedance (46 +/- 5 omega), or LA AFCL (136 +/- 23 ms). There was a significant increase in the mean LA ERP (106 +/- 10 ms at day 0, and 120 +/- 13 ms at day 42 of pacing). In this study, using chronically implanted defibrillation leads, the minimal energy requirements for successful AF were not significantly altered by ongoing left atrial dilatation. This finding is a further endorsement of the efficiency of the coronary sinus/RA shock vector. Furthermore, the apparent stability of the AF present may be a further indication of a link between the type of AF and the ADFT.
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POWER et al. (1998) studied Pacing induced dilated cardiomyopathy (n=8). Rapid ventricular pacing vs. Baseline was evaluated on Atrial defibrillation threshold (ADFT). Progressive left atrial dilatation induced by 6 weeks of rapid ventricular pacing in an ovine model did not significantly alter the mean atrial defibrillation threshold (122 +/- 15 V).
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