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Historic evolution of multisite pacing
Standard DDD pacing with short AV delay was first proposed as a potential treatment of dilated
cardiomyopathy with encouraging preliminary results1. The enthusiasm generated by this report
was, however, rapidly tempered by the results of controlled studies which failed to confirm the value
of DDD pacing in an unselected heart failure population2-5. In a small subset of patients, selected on
the basis of very short filling times and fusion of the mitral A and E waves, it was further found that
restoration of a more physiologic ventricular filling pattern could be beneficial4. However, even in the
best clinical situation, conventional DDD pacing has inevitable adverse hemodynamic consequences
due to right ventricular apical pacing6,7. These deleterious effects are explained by the accentuation
of interventricular and left intraventricular asynchrony, and secondary impairment of left ventricular
systolic and diastolic function8. From this incessant competition between improvement in left ventricular
filling and adverse hemodynamic effects of right ventricular apical pacing, one may separate the
“responders”, in whom the former mechanism prevails, from the “non responders”, where the effects
of right ventricular apical pacing predominate. The study of DDD pacing as a treatment of heart failure
has allowed, nevertheless, to recognize two important issues, namely the individualization of an
optimal atrioventricular delay, and the need to choose a pacing mode offering the most physiological
sequence of ventricular contraction.
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