| dc.description.abstract | The concept of artificial cardiac pacing has been changing over time. The first indication to implant a pacemaker (PM) was a complete atrioventricular block diagnosis. Since then, pacemaker implantation was indicated in other conditions; also, the technology of the implantable devices became more complex. Although the right ventricular apical pacing has been used for many decades, there is strong evidence that this type of stimulation is associated with increased risk of heart failure, atrial fibrillation and mortality. Due to this evidence, it was necessary to use a mode of stimulation that could reduce unnecessary ventricular pacing by promoting intrinsic conduction when possible. The aim of this study was to evaluate the impact of the intrinsic conduction search (ICS) in the pattern of ventricular activation in chagasic and non chagasic patients with DDD pacemakers. The study was conducted between March 2005 and June 2007, and comprised 30 patients, all with stable atrial activity and preserved atrioventricular conduction. The patients underwent a study protocol that included serology for Chagas' disease and evaluation of the pacemaker by telemetry and echocardiography, in order to obtain measurements of ventricular dyssynchrony. During telemetry, the atrioventricular interval was adjusted to allow the prevalence of intrinsic conduction of the ventricules or ventricular pacing. After this, we also performed an echocardiography during intrinsic rhythm and ventricular pacing. After completion of the echocardiogram, the intrinsic conduction search parameter was programmed in all patients. Sixty days after this, we performed a new telemetry test, obtaining the data recorded by the pulse generators, as the percentage of atrial and ventricular pacing events. After obtaining the impedance values, pulse amplitude, pulse width, load and average current of each pulse, we calculated the estimated longevity of generators. Of all patients included in this study, 73.3% were female and non-chagasic. In patients with Chagas disease, most were male. The mean age was 62.5 years and it did not differ between the groups. The analysis of telemetry data showed that in those pacemakers featured to promote AV intrinsic conduction, the percentage of ventricular pacing was significantly lower. There was no significant difference between the other variables obtained by telemetry. When compared to other cardiomyopathies, the Chagas patients showed lower maximum frequency of atrioventricular coupling and higher percentage of ventricular pacing beats after programming ICS. Without the ICS, the two groups showed no significant difference regarding the variables obtained by telemetry from MP. The measures of intraventricular dyssynchrony obtained by echocardiography did not differ between chagasic and non chagasic patients with and without the programming of the search for intrinsic conduction. It was demonstrated that the ICS was able to reduce the number of ventricular stimulations by the pacemaker, increase the longevity of pulse generators and, despite not having been observed ventricular dyssynchrony during right ventricular pacing, the ICS significantly reduced the time to systolic activation of the lateral and septal wall of the left and right ventricles. | |
