Aim: 

Ventricular arrhythmias are frequently observed in the elderly population as changes of the normal aging heart. At present, the underlying mechanisms remain poorly understood. The aim of the study is to determine specific age-related changes in electrophysiological and structural properties of ventricular myocardial tissue which can be related to arrhythmias.

Methods: 

We measured radiotelemetry ECG during 18-24 months in wild type rats. The same animals were then studied in vivo by multiple lead recordings from the ventricular surface.

Results: 

Spontaneous supraventricular and ventricular arrhythmias which increased with age were telemetrically observed. Isochrone maps revealed ectopic beats during premature stimulation and ventricular arrhythmias during burst pacing in aged but not in control hearts. Moreover, ventricular activation was usually characterized by slow periodic circus movements. Interestingly during arrhythmias, focal beats consistently appeared at the same breakthrough points observed during sinus rhythm activation.

Conclusion: 

Our results in aged hearts suggest that peripheral conduction system may participate in perpetuating sequences of ventricular ectopic beats, irrespective of their origin. Impaired interaction between Purkinje system and ventricular myocardium might represent a potential reentry substrate, contributing to higher vulnerability to ventricular arrhythmias in aged hearts.