ABSTRACT
This study was conducted to clarify the validity and availability of inclination of exponential curve-fitting model for oxygen uptake (VO<sub>2</sub>) and heart rate (HR) during incremental exercise (I-ECOH) as an index of cardio-pulmonary functional reserve in patients with ischemic heart disease (IHD). A treadmill exercise test was used to measure the VO<sub>2</sub>(L/kg/min) and HR (beat/min) during incremental exercise of all subjects. I-ECOH was derived from the following equation : HR=A·exp<sup>B·VO2</sup>. The constant "B" represents I-ECOH. The following two identifications were made : 1) the relation between peak oxygen uptake (VO<sub>2</sub>peak) and I-ECOH in IHD patients with normal left ventricular function and with chronic heart failure (CHF); 2) the relation between I-ECOH and the New York Heart Association (NYHA) functional classification of IHD patients with CHF.There were significant differences among IHD patients with normal left ventricular function, CHF patients, normal controls and long distance runners in I-ECOH and VO2peak, respectively (p<0.001). There were inverse correlations between I-ECOH and VO2peak in IHD patients with normal left ventricular function (r=-0.64, p<0.001) and CHF (r=-0.63, p<0.001). I-ECOH could be used to discriminate effectively between NYHA functional classes (p<0.001).In conclusion, these results suggest that I-ECOH is adequate and useful as an index of cardio-pulmonary functional reserve in patients with ischemic heart disease.