O valor prognóstico da eficiência ventilatória em pacientes com miocardiopatia dilatada

Abstract

Introduction: Despite the current control of its transmission, Chagas disease (ChD) remains a serious public health problem, with a high morbidity and mortality rates. Cardiomyopathy is the most frequent complication in ChD, being one of the main etiologies of heart failure with poor prognosis. Identification of patients with dilated cardiomyopathy who are at high risk for adverse events is fundamental to establish differentiated therapeutic strategies with possible impact on the prognosis. In this context, ventilatory efficiency, expressed by the ratio between ventilation and carbon dioxide production, is altered in patients with heart failure. Several studies have associated ventilatory efficiency with the occurrence of adverse events, with prognostic value stronger than functional capacity. The ventilatory efficiency can be evaluated by VE/VCO2 solpe or by the VE/VCO2 ratio at lactate threshold (VE/VCO2 AT). Previous studies have demonstrated that the VE /VCO2 slope is strongly associated with adverse events, but the prognostic value for VE/VCO2 AT has not been defined in patients with heart failure. Thus, the present study was designed to verify the determinants of VE/VCO2 AT and to evaluate the prognostic impact of this variable in patients with heart failure secondary to dilated cardiomyopathies due to Chagas (ChCM) and idiopathic etiology (ICM). Materials and Methods: Patients with ChCM and ICM underwent clinical examination, echocardiographic evaluation and cardiopulmonary exercise test (CPET) symptom-limited. Several CPET parameters were measured, including VO2peak, VE /VCO2 slope, and VE/VCO2 AT. The outcome evaluated during follow-up was combined, defined by death, hospitalization for heart failure, ischemic stroke or need for heart transplantation. RESULTS: We included 79 patients, mean age of 51 ± 14 years, with dilated cardiomyopathy, 52 (66%) secondary to ChD, and 27 (34%) ICM. Fifty-nine patients were in NYHA functional class II and III. The majority were using beta-blockers (87.3%) and 84.8% with ACE inhibitors and / or ARBs. The left ventricular ejection fraction was 38% ± 10% and the right ventricular function assessed by the fractional area change was 49% ± 15%. All patients underwent CPET, without complications, with an exercise time of 522 ± 38 minutes. The VE/VCO2 slope was 34.8 ± 7.2 and VE/VCO2 AT was 30.9 ± 4.6. Subsequently, the factors associated with VE/ VCO2 AT were evaluated. The factors associated with VE/VCO2 AT were NYHA functional class (p = 0.007), left atrial volume (p <0.001) and right ventricular function estimated by tissue Doppler (p = 0.030), adjusted for sex and age. During a follow-up of 17.3 ± 8.4 months, 18 adverse events occurred, including 6 deaths, 5 heart failure hospitalizations, 6 ischemic strokes, and one patient underwent emergency heart transplantation. In the multivariate analysis by the Cox regression model, including the left ventricular ejection fraction, the E/e' ratio, pulmonary artery pressure, etiology of the dilated cardiomyopathy, VE/VCO2AT was an independent predictor of adverse events (HR 1.21; 95% CI 1.10-1.33, p<0.001), after adjustment for beta-blockers use. Conclusion: VE/VCO2 AT was independently associated with NYHA functional class, left atrial volume and right ventricular function, and presented additional prognostic value in patients with dilated cardiomyopathy.