Oxygen pulse is not predictive of stroke volume in heart failure.

AIM: Stroke volume (SV) is the major cardiovascular discriminator between those that are exercise trained versus untrained individuals and healthy individuals versus those with pathologic left ventricular dysfunction. Furthermore, since the increase in oxygen pulse (O(2)P) (O(2)P=VO(2)/HR?oxygen uptake/heart rate) that occurs with exercise is a function of SV and the arterial-venous oxygen difference (a-vO(2)), O(2)P has been demonstrated a reliable indicator of SV for healthy individuals. Although commonly used as a physiological and clinical marker of SV, the validity of O(2)P as an indicator of SV in patients with heart failure has not been investigated. METHODS: Thirty-one (23 men, 8 women) patients (age: 64+/-7.9; ejection fraction: 24+/-7.8) with chronic heart failure had cardiac output measured during steady-state workloads (25 watts and 75% VO(2peak)) upon entry and again at completion of 12 weeks of exercise training. Four patients were excluded due to clinical complications and 3 because of non-compliance; therefore, 24 patients completed the study. RESULTS: The relationships between SV and O2P are: 1) baseline: SV=11.1+4(O2P), SEE=11.8; r(2)=0.39 and 2) study completion: SV=25.1+2.3(O2P), SEE=12.7; r(2)=0.21. While SV did not increase after 25 watts, O2P continued to increase by 17%, respectively. In addition, there were no training effects on SV or O(2)P. As SV increased, O(2)P underpredicted measured SV. CONCLUSIONS: In patients with heart failure and poor left ventricular function, O(2)P is not recommended as a marker of the SV during exercise.

Measuring energy expenditure in cardiac patients using the Body Media Armband versus indirect calorimetry. A validation study.

AIM: The purpose of this study was to compare differences in energy expenditure using the newly developed SenseWear Armband body monitor to indirect calorimetry in cardiac rehabilitation patients. METHODS: Twenty-four (62+/-8.1 years) patients completed steady state exercise for 8 minutes on 4 modes of exercise (arm ergometry, treadmill walking, recumbent stepping and rowing ergometry). Total cumulative kilojoules were recorded simultaneously by indirect calorimetry and the SenseWear Armband. Statistical analyses assessed the degree of agreement between the 2 measurement methods and 3 different versions of the SenseWear software. RESULTS: The correlations between indirect calorimetry and version 2.2 of the SenseWear armband for arm and rowing ergometry, the treadmill and recumbent stepper were r=0.90, r=0.67, r=0 .80 and r=0.74, respectively. There were no between method differences during arm ergometry (p<1.000) and the recumbent stepper (p<0.102). Bland and Altman plots revealed the greatest spread of scores for the rower and the treadmill. Between method differences were minimal when using the preliminary cardiac software. The correlations for arm and rowing ergometry, the treadmill and recumbent stepper were r=0.90, r=0.84, r=0.78 and r=0.82, respectively. CONCLUSIONS: The accuracy of the BodyMedia SenseWear Armband appears to be exercise modality dependent in those with heart disease when using software developed for the general population. Therefore, the information should be interpreted cautiously, particularly during treadmill walking and rowing. Initial experiments with cardiac-focused software are promising, but preliminary.

Cardiac rehabilitation without exercise tests for post-myocardial infarction and post-bypass surgery patients.

PURPOSE: To compare the progress of patients who were exercise tested before or during cardiac rehabilitation versus those patients who were not tested. METHODS: Eighty-eight (88) post-myocardial infarction patients and 141 post-bypass surgery patients had a symptom-limited exercise test before or during 12 weeks of cardiac rehabilitation. Another 125 post-myocardial infarction and 146 post-surgery patients were not tested. RESULTS: Caloric expenditure during class increased for the entire group (P < 0.001) from week 1 to week 12. Body weight decreased for the entire group as a result of cardiac rehabilitation (P < 0.001). Tricep skinfolds decreased for the entire group (P < 0.001) while subscapular skinfolds did not change (P = 0.28). The percent change from week 1 to week 12 for both groups was similar for all variables. No problems occurred during cardiac rehabilitation that required emergency medical management. CONCLUSIONS: Patients completing a 12-week cardiac rehabilitation program can be safely progressed in terms of their exercise capacity without an entry exercise test. This is desirable in a managed-care setting for reducing costs while maintaining effective patient care. Such factors as staff training and experience, institutional philosophy, patient referral patterns, and facility location must be considered before adopting a no-test policy.