Variabilidade da frequência cardíaca no domínio do caos como preditora de morbimortalidade em pacientes submetidos à cirurgia de revascularização do miocárdio

Abstract

Recent studies have shown that low heart rate variability (HRV) is a clear indication of an increased risk for severe ventricular arrhytmia and sudden cardiac. However, the traditional techniques of data analysis in time and frequency domain are often not sufficient to characterize the complex dynamics of heart beat generation. Hence, different attempts have been reported to apply the concept of nonlinear dynamics (chaos domain) to this problem as the methods Detrended Fluctuation Analysis (DFA), Autocorrelation (Tau), Hurst Exponent (HE), Lyapunov Exponent (LE), Poincaré Plot (SD1 e SD2). Objective: We speculated that patients with decreased chaotic behavior in the preoperative period would tend to present higher morbidity and mortality in the length of postoperative stay. Methods: Seventy-two non-selected patients (mean age 58.4±10.2 years) with coronary artery disease and elective coronary artery bypass graft surgery (CABG) indication, were studied. We had their HRV with Polar Advanced S810 and analyzed with the above chaos, time and frequency domain variables. The occurrences of relevant events during the length of postoperative stay as neurological, infectious and renal complications, severe arrhytmias or death were compared. The Fisher s Test was used to compare the occurrence of events. We described Sensibility, Specificity, Positive Predictive Value, Positive Likelihood Ratio and ODDS Ratio (CI 95%). Results: In comparison of groups death versus no death (Scenario 1) of the Lyapunov Exponent, for example, the ODDS Ratio was 11.5 (CI 95% 1.261 to 104.92, P=0.0171). The Scenario 3 (2 or more events versus 0 to 1 event) showed the Odds Ratio 12.414 (CI 95% 1.515 to 101.72, P=0.0048). Conclusions: The patients with decreased HRV evaluated from some nonlinear dynamic analysis methods before CABG surgery present higher morbidity and mortality in the length of postoperative stay.