Long-term experience with a contractility (autonomic nervous system) driven pacemaker sensor in patients with chronic chagasic cardiomyopathy.

We analyzed performance of a ventricle-paced, ventricle-sensed, inhibited, rate-responsive (VVIR) pacemaker driven by autonomic nervous system activity sensor in chagasic patients with cardiac conduction system disturbances. Forty-seven chagasic patients were studied (28 male, 19 female; age, 24-68 years). Thirty-six patients had complete atrioventricular (AV) block, eight had second-degree AV block, and the remaining three patients had sinus node disease. Patients were divided into two groups according to their heart rate (HR) at rest: group 1 had an HR more than 65 bpm; group 2, HR less than 65 bpm. A comparative study that extended over the first 12 months after pacemaker implantation evaluated: HR at rest and during various types of stress tests, arterial blood pressure at rest and during exercise, and performance of the TIR-60 UP leads in conjunction with the sensor function as compared with the performance of other leads. Patients from group 1 had a higher HR at rest and a smaller HR variation during stress test than did patients from group 2. This indicates that with this type of rate-adaptive system it is possible to control each patient individually. The blood pressure at rest and during stress tests did not differ between the two patient groups. With respect to the sensor function, the TIR-60 UP leads offered the same performance as others leads. The VVIR pacemaker equipped with the sensor of autonomic nervous system activity allowed chagasic patients to restore their physiologic mechanisms. Seventy-four percent of the patients had the New York Heart Association Functional Class improved by 1 or 2 steps, after the pacemaker implantation.