ABSTRACT
The purpose of this study was to investigate the prognostic value of change in heart rate (HR) response to oxygen uptake (VO<sub>2</sub>) during exercise in patients with coronary heart disease (CHD).We retrospectively studied 204 patients with CHD who were sent to our exercise testing laboratory between August 1983 and February 1985. The following equation was used to determine the relation between VO<sub>2</sub> and HR during a graded treadmill exercise test: HR= A・exp <sup>B･VO2</sup>, where the constant b was defined as the inclination of the exponential curve-fitting model for oxygen uptake and heart rate during graded treadmill exercise (I-ECOH). Data on mortality were determined in May 2006 by examining medical records from the outpatient clinic and/or conducting telephone interviews with the patients or their families. Among the 204 study subjects, there were 54 cardiac deaths during the entire 20-year follow-up period. Kaplan-Meier survival curves for 20 years of follow-up demonstrated a survival rate of 81.3% for patients with a lower I-ECOH (＜35) and 56.0% for those with a higher I-ECOH (≧35), showing a significant difference in survival (p＜0.001). Multivariate Cox proportional hazards analysis revealed left ventricular ejection fraction (LVEF), peak oxygen uptake (VO<sub>2</sub> peak) and I-ECOH as independent predictors of survival. In this analysis, the prognostic power of minutes ventilation/carbon dioxide output (VE/VCO<sub>2</sub>)slope was insignificant. The patients were divided into two groups with (＜45%) and without (≧60%) LV dysfunction using LVEF for more detailed analysis. The VO<sub>2</sub> peak and VE/VCO<sub>2</sub> slope were significant independent predictors of survival in patients with LV dysfunction. However, the I-ECOH was a significant independent predictor of survival in patients with and without LV dysfunction. Our data indicate that I-ECOH provides independent prognostic information on CHD patients with and without LV dysfunction.
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.
ABSTRACT
A 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 (IECOH) as an index of cardio-pulmonary functional reserve in healthy subjects. 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. The IECOH was derived from the following equation : HR=A⋅exp<SUP>B·VO<SUB>2</SUB></SUP>. The constant “B” represents the IECOH. The following three identifications were made : 1) the relationship between maximal oxygen uptake (VO<SUB>2</SUB>max) and IECOH in 82 healthy males ; 2) the relationship between IECOH and age in 428 healthy males and females ; 3) the effect of physical training in 8 healthy males.<BR>There was inverse correlation between IECOH and VO<SUB>2</SUB>max (r= -0.824) . And also, there were inverse correlations between IECOH detected from submaximal tests and VO<SUB>2</SUB>max (above r=-0.6) . There were no differences in the IECOH detected from maximal and submaximal tests. In Bland-Altman plot method, accuracy of measurment in the IECOH detected from submaximal exercise test was precise. There was a significant relationship between IECOH and age in male and female subjects (r=0.499 and r=0.310, respectively) . Physical training increased VO<SUB>2</SUB>max and decreased IECOH significantly. The VO<SUB>2</SUB>max before and after physical training correlated inversely with the IECOH before and after physical training (r=-0.514) .<BR>In conclusion, these results suggest that IECOH is adequate and useful as an index of cardio-pulmonary functional reserve which can be measured by the submaximal exercise test in healthy subjects.
ABSTRACT
This study examined the effects of physical training on exercise hyperpnea (EH) in patients on hemodialysis (HD) . In baseline, 17 (trained group) and 12 (control group) patients on HD performed symptom limited exercise test using a treadmill. Trained group, but not control group, exercised 2 to 3 times weekly on non-dialysis days under medical supervision. Exercise testing was repeated 20 weeks after the baseline. Ventilatory response to exercise was evaluated using the regression slope relating minute ventilation (VE) to carbon dioxide output (VCO<SUB>2</SUB> ) during incremental exercise (VE/VCO<SUB>2</SUB> slope) below the point of respiratory compensation. In trained group, VE, oxygen uptake ( VO<SUB>2</SUB>) and VCO<SUB>2</SUB> at peak exercise increased and VE/VO<SUB>2</SUB> and VE/VCO<SUB>2</SUB> decreased after physical training, respectively. No change was observed in control group. VO<SUB>2</SUB> at the anaerobic threshold increased in trained group, but not in control group. The post training VE/VCO<SUB>2</SUB> slope (33.9±5.0) was significantly (p<0.05) lower than the pre-training slope (38.0± 4.8) and remained constant in control group. In trained group, changes in the VE/VCO<SUB>2</SUB> slope correlated with those in peak VO<SUB>2</SUB> (p<0.05) . These results suggest that physical training decreases EH in patients on HD and that it correlates with changes in exercise tolerance.
ABSTRACT
A study was conducted to clarify the effect of hyperoxia (HO) on exercise tolerance andhemodynamics in patients with ischemic heart disease (IHD) . The subjects were 10 patients with serious IHD who showed ischemic ST depression during low-intensity exercise testing. In all subjects, cardiopulmonary exercise testing (CPX) was performed using two types of inhalation : normoxia (NO) and HO (O<SUB>2</SUB>: 60%, N<SUB>2</SUB>: 40%) . Heart rate (HR), blood pressure (BP), rating of perceived exertion (RPE), elapsed exercise duration and pressure rate product (PRP) were measured, and ECG was recorded during CPX according to the Bruce protocol. The peak oxygen uptake (VO<SUB>2</SUB>peak) was calculated using the appropriate formula. These data were compared between the NO and HO groups, and the following results were obtained.<BR>ST depressions on ECG, BP, HR and PRP after 20 min of rest showed no changes under NO. The other hand, only ST depression was improved after 20 min of rest under HO. The exercise duration in HO group was longer than in the NO group, and the VO<SUB>2</SUB>peak in the HO group was higher than in the NO group. However, peak RPE showed no significant difference between the HO and NO groups. The incidence of ST depression as an endpoint of CPX showed no significant difference between the two groups. BP, HR and PRP at the CPX endpoint showed no significant differences between the HO and NO groups. In patients whose exercise duration was prolonged beyond the mean value by HO, peak HR and PRP were increased significantly. However, this tendency was not seen in patients whose exercise was prolonged for less than the mean value.<BR>In conclusion, these results suggest that an increase in the oxygen supply to peripheral working muscles may play an important role in increasing exercise tolerance under HO in IHD patients.
ABSTRACT
A study was conducted to evaluate the effects of exercise training for cardiac rehabilitation. 69 patients with coronary artery disease were assigned to a low intensity exercise training program, which lasted for 3 months. The target heart rate for the exercise program was set at 50-60% of maximal heart rate. For comparison, the study patients were divided into 2 groups. 25 patients who had undergone CABG were assigned to group A and 42 patients who had not undergone CABG were assigned to group B. A symptom-limited treadmill exercise test was performed before and after the exercise training program in each patient. Oxygen uptake (VO<SUB>2</SUB>), SBP, HR and PRP were measured at rest, submaximal workload and workload at the end point during the treadmill exercise test.<BR>In addition, FAT, LVI and PCI were calculated. The parameters measured before and after exercise training were compared in order to assess the effects of the exercise training program. Our findings showed that exercise training was effective for improving exercise tolerance and submaximal exercise capacity in patients with coronary artery disease, particularly those who had undergone CABG.