Abstract 3112: Slower Periodic VO2 Oscillations during Exercise Indicate Worse Clinical Status and Poorer Prognosis of Patients with Heart Failure
Purpose: It is generally assumed that the cycle length (CL) of periodic VE or VO2 oscillation, an ominous sign seen during exercise in advanced heart failure (HF), is approximately one minute. However, in our experience, the duration seems to vary substantially among individuals, and the differences in CL may be of clinical and prognostic value. We hypothesized that CL varies substantially among patients with HF and that slower oscillations indicate worse clinical status and prognosis.
Methods: From a consecutive series of over 4500 symptom-limited bicycle exercise tests with respiratory gas analysis performed for recent 5.5 years, we selected 50 patients (LVEF = 31 ± 13%) with HF exhibiting the most marked exercise VO2 oscillations that allowed us to accurately measure CL. The patient selection were made by our developed FFT method estimating the ratio of low-frequency power (0.5–1.25 cycle/min) relative to total power (4-min time-window, overlapping every 30sec). After averaging CL of at least 3 periodic VO2 fluctuations for each patient, patients were evenly divided into two groups according to the median of CL: Group-S (Slower, longer CL, n=25) and Group-F (Faster, shorter CL, n=25). Demographic, clinical, prognostic, and exercise data were compared between the groups.
Results: We found that CL substantially varied from 45 to 118 sec (median = 67 sec). CL of Group-S was 80 ± 11 sec, while that of Group-F was 59 ± 6 sec. There was no significant difference with respect to age, sex, and etiology of HF between the groups. Compared with Group-F, Group-S showed lower peak VO2 (15.4 ± 3.6 vs 18.6 ± 4.2 ml/min/kg, p=0.005) and oxygen pulse (7.4 ± 2.5 vs 9.5 ± 2.1 ml, p=0.002), and greater VE/VCO2 slope (42 ± 12 vs 37 ± 8, p=0.049). Group-S also had higher BNP level (457 ± 348 vs 256 ± 275 pg/ml, p=0.03). Kaplan-Meier mortality rates for cardiac and all-cause death were significantly higher in Group-S than in Group-F (both, p<0.05).
Conclusions: We demonstrated that cycle length of exercise VO2 oscillations substantially varies among patients with heart failure, and that the difference is of clinical significance; the slower the cycle length, the worse the clinical status and prognosis.