What Are the Long-Term Benefits of the Dual-Chamber Rate-Responsive System Driven by Contractility?
Myocardial contractility beat-to-beat evaluation is now possible using an implanted microaccelerometer located on the tip of an endocardial lead in the right ventricle. The signal provided by this device is closely related to right ventricle dp/dt curve. The maximal value of the accelerometer signal, peak of endocardial acceleration (PEA) is correlated with dp/dt max (mm Hg) during dobutamine infusion. Some previous studies have clearly established a direct correlation between right and left ventricle contractility [1–3]. Increased cardiac output during exercise and emotional or psychological stress is mediated by the autonomic nervous system, sympathetic tone increasing myocardial contractility and heart rate . In an individual patient, every PEA value is associated with a heart rate value. These two parameters related by a closed loop algorithm can be used to drive a rate-responsive pacemaker in patients with chronotropic incompetence but normal contractility adaptation during sympathetic stimulation. A DDDR device was provided by Sorin (Italy) Living 1 pacemaker. This works using a specially designed ventricular lead tipped by a microaccelerometer and a standard pacing unipolar electrode. Some studies have demonstrated the efficacy of this pacemaker [5–7]. The aim of this paper is to study the long-term stability of the correlation linking PEA and heart rate variations in implanted patients.
KeywordsMyocardial Contractility Sick Sinus Syndrome Pace Threshold Ventricular Lead Accelerometer Signal
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