Background and aim: Pattern of heart rate (HR) changes during exercise and recovery is deranged in patients with cardiovascular disease, being considered as an independent predictor of poor outcome. This issue has been poorly examined in patients with chronic heart failure (CHF), particularly in the early stages of this syndrome.
Methods: Cardiopulmonary exercise testing (CPX) was performed in 54 men with sinus rhythm with mild stable systolic CHF in NYHA class I-II (age 57 ± 12 years, LVEF 31 ± 8%) and in 27 male volunteers without CHF (age 54 ± 8 years, LVEF 67 ± 7%). Apart from peak oxygen consumption (peakVO₂), chronotropic response was evaluated using the following parameters: peak heart rate (HR) expressed in absolute values (maxHR) and age-predicted maximal values (%maxHR), HR increase during exercise (ΔHR), chronotropic index (CI = ΔHR/predicted ΔHR) and a regression coefficient of a linear function between HR and time during exercise (HR-time slope). Chronotropic response was also evaluated during recovery based on a regression coefficient of a linear function between HR and time during the first three-min of recovery (HR-time slope) and HR decrease after 90 s (HRR90), 120 s (HRR120) and 180 s (HRR180) from peak exercise.
Results: Men with CHF in NYHA II and I class demonstrated impaired chronotropic response to exercise as compared to control peers: NYHA II vs NYHA I vs control: maxHR 122 ± 24 vs 154 ± 25 vs 166 ± 13 bpm, all p < 0.05; %maxHR 76 ± 14 vs 91 ± 11 vs 101 ± 7%, all p < 0.001; ΔHR 48 ± 20 vs 75 ± 20 vs 91 ± 14 bpm, all p < 0.01; HR-time slope during exercise 5.6 ± 2.2 vs 6.5 ± 2.6 vs 8.3 ± 1.2, all p < 0.01 (NYHA I vs NYHA II, p > 0.2); CI 0.56 ± 0.36 vs 0.85 ± 0.21 vs 1.02 ± 0.13, all p < 0.01; HR-time slope during three-min of recovery -14.0 ± 7.0 vs -19.2 ± 5.1 vs -23.5 ± 3.8, p < 0.05 (NYHA I vs control p > 0.2); HRR90 30 ± 17 vs 44 ± 14 vs 49 ± 9 bpm, p < 0.05 (NYHA I vs control p > 0.2); HRR120 35 ± 8 vs 51 ± 13 vs 59 ± 9 bpm, all p < 0.05; HRR180 41 ± 17 vs 57 ± 15 vs 68 ± 10 bpm, all p < 0.01. In CHF men, impaired peakVO₂ was related to HR response to exercise (r = 0.60, p < 0.001) and recovery (r = 0.50, p < 0.001). Abnormal HR response to recovery correlated also to high NT-proBNP (r = 0.33, p < 0.05). In 13 men with CHF in whom CPX was performed twice between 17 ± 11 days, variability coefficients for analysed parameters of chronotropic response ranged 8–15%.
Conclusions: Parameters reflecting the chronotropic response to exercise and recovery are characterised by a good reproducibility, hence may be useful in the clinical assessment of patients with CHF. There is a marked reduction of chronotropic response in patients in the early stages of CHF, which may be another mechanism limiting exercise capacity.
Kardiol Pol 2010; 68, 12: 1323-1330