Comparison of prognostic values of cardiopulmonary and heart rate parameters in exercise testing in men with heart failure

Background: Cardiopulmonary exercise testing (CPET) is the gold standard in the evaluation of patients with chronic heart failure (CHF). However, this test is relatively expensive, assessment of its results requires experience, and in Poland it is available only in tertiary health care centers. Many heart rate (HR) parameters taken during a standard electrocardiographic (ECG) exercise test also shows prognostic values. Thus, the aim of this study is to compare prognostic values of ventilatory and HR parameters in exercise testing in CHF patients, and to find out if HR parameters can be used instead of ventilatory in the evaluation of a prognosis. Methods: One hundred thirty two men (mean age 49 ± 11 years) with CHF with reduced left ventricu­lar ejection fraction (< 45%) underwent a treadmill CPET using a modified Bruce’s protocol, during which both HR and ventilatory parameters were measured. The patients were followed for 27 ± 13 months after CPET. Results: Mortality was 28% (n = 37). Non-survivors demonstrated significantly shorter exercise time (342 ± 167 vs. 525 ± 342 s, p < 0.001), lower maximal HR (122 ± 22 vs. 138 ± 21 bpm, p < 0.001), smaller difference between maximal HR and at rest (36 ± 19 vs. 52 ± 21 bpm, p < 0.001), and lower HR recovery rate (HRR; 16 ± 10 vs. 24 ± 13 bpm, p = 0.002), chronotropic index (CHI; 0.45 ± 0.23 vs. 0.61 ± 0.23, p < 0.001), peak oxygen consumption (13.82 ± 4.62 vs. 18.54 ± 5.68 mL/kg/min, p < 0.001) and oxygen uptake efficiency slope (OUES) value (1.56 ± 0.58 vs. 1.94 ± 0.63, p = 0.001), and higher ventilation to carbon dioxide production (VE/VCO2) slope value (40.56 ± 9.11 vs. 33.33 ± 7.36, p < 0.001). Two parameters that showed good prognostic value and availability in a routine CPET were chosen for receiver operating characteristic analysis, VE/VCO2 slope and CHI, which showed cut-off values of 35 (sensitivity 74%, specificity 71%, p < 0.001) and 64 (sensitivity 74%, specificity 68%, p < 0.001) respectively. Conclusions: Heart rate parameters show significant prognostic values; CHI is the best of them, however, it is weaker than VE/VCO2 slope. HR parameters show somewhat weaker prognostic values in comparison with ventilatory parameters, yet they may be useful in cases of CPET unavailability