Review Article
Comparison of Atrial Fibrillation in the Young versus That in the Elderly: A Review
Table 2
Electrophysiological differences between the elderly and young that can predispose to AF (summarised from human and animal studies in Table
1).
| Features | Elderly | Young |
| Impulse initiation | | | (i) Sinus node function | Impaired (leading to longer sinus node recovery times), contributing to abnormal impulse initiation | Generally preserved | (ii) Pulmonary vein ectopic activity | Also contributes to AF pathogenesis although substrate abnormalities have a dominant role in initiation and maintenance | Predominant trigger for AF initiation |
| Impulse conduction | | | (i) P wave morphology and duration (usually signifying interatrial conduction) | Abnormal P wave morphology and prolonged interatrial conduction | Usually normal | (ii) Wavefront propagation | Abnormalities noted such as conduction slowing (particularly of premature impulses) thereby contributing to reentrant waves | Usually normal |
| Substrate abnormalities | | | (i) Complex fractionated atrial electrograms | Greater number | Lesser than in elderly | (ii) Atrial refractoriness—effective Refractory Period (ERP) | ERP prolonged in the right atrium and could contribute to dispersion in refractoriness | Usually not prolonged | (iii) Action potential duration (APD) | Prolonged in the right atrium | Generally within normal limits | (iv) Regional atrial voltage differences | Larger atrial volumes with more number of low voltage areas | Atria usually of normal size and mean voltage within normal limits |
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