Key result
Ventricular rate variability in AF directly reflects scaled atrial variability across conduction pathways.
Why the study?
The genesis of the irregularity of the ventricular rhythm in patients with atrial fibrillation is not yet fully understood, particularly the role of the atrioventricular conduction pathways.
Observational (n=18)
p-value: p=>0.27
Irregularity of the ventricular response during atrial fibrillation is determined by atrial variability and the scaling factor of the conduction pathway, behaving similarly whether conduction is via the AV node or an accessory pathway.
Irregularity of the ventricular rhythm is a hallmark of patients with atrial fibrillation, yet the genesis of the irregularity is not yet fully understood. The role of the atrioventricular (AV) node in determining the irregularity of the ventricular response to atrial fibrillation was investigated by comparing the frequency distributions of the atrial (AA) and the ventricular (RR) intervals. Atrial electrograms and surface electrocardiographic leads were recorded during sustained atrial fibrillation in 12 patients with conduction over the AV node. The scaling factor (mean RR interval/mean AA interval) quantified the ability of the conduction pathway to scale the atrial input to a slower ventricular response and ranged from 2.55 to 5.92 (mean +/- SD 3.77 +/- 0.92). The coefficient of variation (SD/mean) measured the relative variability of the AA and RR interval distributions. The atrial and ventricular coefficients of variation were not significantly different (0.20 +/- 0.04 versus 0.21 +/- 0.03, p greater than 0.27). Similar recordings were analyzed in six patients with conduction over a accessory AV pathway. The scaling factor ranged from 1.54 to 2.46 (2.02 +/- 0.39) and, as was the case for patients with conduction over the AV node, the atrial and ventricular coefficients of variation did not significantly differ (0.24 +/- 0.08 versus 0.27 +/- 0.10, p greater than 0.6). For both groups of patients, ventricular variability and the maximal RR intervals were predicted by the product of the scaling factor and either atrial variability or maximal AA intervals, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
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Kirsh et al. (1988) conducted an observational in Atrial fibrillation (n=18). Conduction over the AV node vs. Conduction over an accessory AV pathway was evaluated on Difference between atrial (AA) and ventricular (RR) interval coefficients of variation (p=>0.27). In patients with atrial fibrillation, ventricular variability was predicted by the product of the conduction pathway scaling factor and atrial variability, with similar atrial and ventricular variations.
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