Impact of DDD and VVIR Stimulation Modes on Functional Capacity and Quality of Life of Chagasic Patients

Introduction: Atrioventricular stimulation provides hemodynamic benefi ts over the isolated ventricular rate, but this advantage is not completely established in chagasic patients with systolic dysfunction. Objectives: To evaluate the inﬂ uence of DDD and VVIR stimulation modes on functional capacity, quality of life (QoL) and laboratory abnormalities of a natriuretic peptide in chagasic patients with ventricular dysfunction submitted to pacemaker implantation. Methods: Twenty patients (55% male) with a mean age of 62.7 (± 9.9 years) and a mean ejection fraction of 41.8% (± 2.8) were prospectively studied. Alternately, patients received pacing in the DDD and VVIR modes for a period of three months under each schedule. The minimum percentage of ventricular pacing was 80%. After each period, the patient was submitted to the six-minute walk test (6MWT), QOL assessment by the Minnesota Living with Heart Failure Questionnaire (MLHFQ) and the Assay of QUAlity of life and RELated events (AQUAREL). Laboratory evaluation was performed with the N-terminal fraction of the brain natriuretic peptide (N-terminal pro b-type natriuretic peptide - NT-proBNP). Results: The mean distance walked on the 6MWT in the DDD and VVIR modes were 390.60 (± 52.71) and 396.30 (± 52.71) meters respectively (p = 0.160). Results of lower QOL were found, considering the physical domain of the MLHFQ (p = 0.03) and the domains of effort dyspnea (p = 0.05) and arrhythmia (p <0.001) of the AQUAREL with the VVIR mode. NT-proBNP levels increased signifi cantly with stimulation in VVIR mode (p < 0.001). Conclusion: After three months of stimulation with the VVIR mode, there was worsening of the QoL of the chagasic patients and increase of the levels of NT-proBNP (clinical trial record: ReBEc RBR-53x476)


PALAVRAS-CHAVE:
The AV interval was not individualized, being maintained the nominal of 120 ms after a spontaneous «p» wave and 150 ms after a stimulated «p» wave. The occurrence of a dynamic AV interval was allowed.

Statistical analysis
The verification of normality of the quantitative data was performed with the Kolmogorov-Smirnov test. Parametric variables were analyzed by paired t-test.
The Wilcoxon test was applied for non-parametric variables. Regarding the frequencies found in the NYHA classification, the chi-square hoc-post-test was used, as described by Beasley et al. 9 . For all analyses, a significance level of 5% (p <0.05) was adopted with a 95% confidence interval from a convenience sample.
The Spearman test was used to evaluate the correlation between QOL results, functional capacity, and NT pro-BNP dosages.

RESULTS
After applying the inclusion criteria, 23 patients were selected for the study. Three of these did not complete the follow-up because they presented atrial fibrillation or less than 80% of ventricular pacing (Fig. 1).
The AQUAREL results indicated that the stimulation mode did not affect the chest discomfort domain, whose In the DDD mode, the Spearman test indicated a correlation between the results found in the physical and emotional domains of the MLHFQ with its total score. In addition, it was possible to verify a correlation between the effort dyspnea and arrhythmia domain analysis of the AQUAREL questionnaire, with the results of the MLHFQ in DDD mode (Fig. 3) and in the VVIR mode (Fig. 4).

DISCUSSION
The results of this work demonstrate that the AV stimulation mode provides a better impact on QoL according to both instruments used.
Although no significant effect on the global MLHFQ score, when analyzing its physical component, we     21 , the brain natriuretic peptide (BNP) was