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This Article Full Text Full Text (PDF) All Versions of this Article: 295/6/H2336    most recent 00517.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Rossi, S. Articles by Macchi, E. PubMed PubMed Citation Articles by Rossi, S. Articles by Macchi, E.

Ventricular activation is impaired in aged rat hearts

¹Dipartimento di Biologia Evolutiva e Funzionale, Sezione Fisiologia, Università degli Studi, Parma, Italy; ²Department of Physiology, University of Bern, Bern, Switzerland; ³Dipartimento di Patologia e Medicina di Laboratorio, Sezione di Anatomia ed Istologia Patologica and ⁴Dipartimento di Clinica Medica, Nefrologia e Scienze della Prevenzione, Sezione di Medicina del Lavoro, Università degli Studi, Parma, Italy; and ⁵Centro di Biomagnetismo-Fisiologia Clinica, Università Cattolica del Sacro Cuore, Rome, Italy

Submitted 15 May 2008 ; accepted in final form 9 October 2008

Ventricular arrhythmias are frequently observed in the elderly population secondary to alterations of electrophysiological properties that occur with the normal aging process of the heart. However, the underlying mechanisms remain poorly understood. The aim of the present study was to determine specific age-related changes in electrophysiological properties and myocardial structure in the ventricles that can be related to a structural-functional arrhythmogenic substrate. Multiple unipolar electrograms were recorded in vivo on the anterior ventricular surface of four control and seven aged rats during normal sinus rhythm and ventricular pacing. Electrical data were related to morphometric and immunohistochemical parameters of the underlying ventricular myocardium. In aged hearts total ventricular activation time was significantly delayed (QRS duration: +69%), while ventricular conduction velocity did not change significantly compared with control hearts. Moreover, ventricular activation patterns displayed variable numbers of epicardial breakthrough points whose appearance could change with time. Morphological analysis in aged rats revealed that heart weight and myocyte transverse diameter increased significantly, scattered microfoci of interstitial fibrosis were mostly present in the ventricular subendocardium, and gap junction connexin expression decreased significantly in ventricular myocardium compared with control rats. Our results show that in aged hearts delayed total ventricular activation time and abnormal activation patterns are not due to delayed myocardial conduction and suggest the occurrence of impaired impulse propagation through the conduction system leading to uncoordinated myocardial excitation. Impaired interaction between the conduction system and ventricular myocardium might create a potential reentry substrate, contributing to a higher incidence of ventricular arrhythmias in the elderly population.

epicardial mapping; breakthrough point; aged heart