Author + information
- Rujie Qin1,
- Osamu Nagayama2,
- Yuta Takayanagi3,
- Arisa Nagamine3,
- Longmei Wu4,
- Jo Kato5,
- Isao Nishi6,
- Yuko Katoh2,
- Takeshi Yamashita2,
- Akira Koike5 and
- Kazutaka Aonuma5
- 1Doctoral Program in Clinical Sciences, Graduate School of Comprehensive Human Science, University of Tsukuba
- 2The Cardiovascular Institute
- 3Master's Program in Medical Science, Graduate School of Comprehensive Human Science, University of Tsukuba
- 4Department of Cardiology, National Hospital Organization Kasumigaura Medical Center
- 5Cardiovascular Division, Institute of Clinical Medicine, Graduate School of Comprehensive Human Science, University of Tsukuba
- 6Department of Cardiology, Tsuchiura Clinical Education and Training Center, University of Tsukuba
Ventilation (VE) increases almost linearly with the increase in CO2 output (VCO2) during incremental exercise testing. This VE-VCO2 slope rises in parallel with the severity of heart failure. Usually, this slope becomes steeper just before peak exercise probably because of the respiratory compensation for lactic acidosis, and this point is called RC point. However, the RC point may not be identified in some patients. We evaluated whether the respiratory compensation during exercise testing has clinical significance in cardiac patients.
In total, 152 cardiac patients (66.7±5.4 years) whose gas exchange ratio (R) at peak exercise ranges from 1.10 to 1.20 were enrolled. We compared cardiopulmonary function between patients who showed RC point (n=118) and those without it (n=34).
The R at peak exercise did not significantly differ between patients with RC point (1.15±0.03) and those without it (1.14±0.03). However, as compared to the patients without RC point, those with RC point had higher peak VO2 (20.2±5.3 vs 13.6±3.4 ml/min/kg, p<0.001), higher anaerobic threshold (12.4±3.2 vs 9.2±2.3 ml/min/kg, p<0.001), and lower VE-VCO2 slope (31.7±5.8 vs 37.8±9.6, p=0.001). BNP also tended to be lower in the patients with RC point (175.4±364.7 vs 327.9±381.1pg/ml, p = 0.077).
The present findings suggest that the phenomenon of respiratory compensation during heavy exercise indicates better cardiopulmonary function in cardiac patients.