Relationship Between Physical Activity Patterns And Key Cardiopulmonary Exercise Testing Variables In Patients With Heart Failure
- Presented on May 31, 2013
Purpose A hallmark characteristic of heart failure (HF) is reduced physical activity (PA) patterns and functional capacity. The relationship between key cardiopulmonary exercise testing (CPX) variables and PA patterns has not been investigated. To evaluate PA patterns in patients with ischemic HF and its relationship to peak oxygenconsumption (VO2), the minute ventilation/dioxide carbon production (VE/VCO2) slope and the oxygen uptake efficiency slope (OUES).
Methods A cross sectional study was carried out in 16 patients with ischemic HF (age 57 ± 9 years, percent ejection fraction: 31,84 ± 8,26). Subjects wore an accelerometer (Actigraph® GT3X) for six days to measure total steps/day as well as percent time at light, moderate and vigorous PA. A symptom-limited CPX was performed on a treadmill using a ramping protocol (0.5 metabolic equivalents/min). Oxygen consumption (ml.Kg-1.min-1), VCO2 (L/min) and VE (L/min) were collected (K4 COSMED®, Italy) throughout the CPX. Peak VO2 was expressed as the highest 30-second average value obtained during the last stage of the CPX. The VE/VCO2 slope and OUES were obtained by least squares linear regression. One way analysis of variance was used to assess differences between PA patterns at different intensities. Pearson’s correlation was used to assess the relationship between PA and CPX variables. A p-value < 0.05 was considered statistically significant.
Results Subjects performed an average of 9029 steps/day, with the majority of PA performed at light intensity (66.48 ± 6.24%) compared to moderate (28.75 ± 4.39%) and vigorous (4.32 ± 1.01%) intensities ( p < 0.05). PA patterns demonstrated a significant correlation with key CPX variables. Total steps correlated with peak VO2 (r = 0.64 p < 0.05), the VE/VCO2 slope (r = – 0.72; p < 0.05) and the OUES (0.63; p <0.05). The percent time at light intensity PA correlated with the VE/VCO2 slope (r = 0.58; p < 0.05) and the OUES (- 0.51; p <0.05). The percent time at vigorous intensity PA correlated with peak VO2 (r = 0.55; p < 0.05) and the, VE/VCO2 slope (r = – 0.52; p < 0.05).
Conclusions PA assessed by accelerometer is significantly associated with key CPX variables in patients with HF. These findings suggest PA monitoring may provide insight into functional patterns and identify patients with a higher likelihood for a poor CPX response.