Measurement properties of Tai Chi exercise self-efficacy among ethnic Chinese with coronary heart disease risk factors: a pilot study.

BACKGROUND: Improvement in aerobic capacity and reduction in blood pressure after Tai Chi exercise programs in persons with coronary heart disease (CHD) or with CHD risk factors have been reported. Self-efficacy has been shown to be a consistent predictor of behavioral outcomes, now being applied to Tai Chi exercise. AIM: To assess the utility and appropriateness of existing tools measuring aspects of Tai Chi exercise self-efficacy (TCSE) in a new population, ethnic Chinese with CHD risk factors. Specific objectives were: (1) examine acceptability and feasibility; (2) determine score distributions; (3) assess the reliability and known-groups validity; (4) translate tool into an equivalent Chinese version and determine if there were any differences between ethnic Chinese and non-Chinese. METHODS: Following a review of the literature, two existing tools used with Caucasians were found and modified; a 9-item exercise self-efficacy tool developed by Resnick and Jenkins [Resnick B, Jenkins LS, Testing the reliability and validity of the Self-Efficacy for Exercise scale. Nurs. Res. 49(3) (2000) 154-159], and a 3-item tool developed by Li et al. [Li F, McAuley E, Harmer P, Duncan TE, Chaumeton NR, Tai Chi enhances self-efficacy and exercise behavior in older adults. J. Aging Phys. Act. 9 (2001) 161-171] to assess gradations of the challenge to perform Tai Chi among elderly populations. The modified TCSE tool was translated into Chinese and back-translated. A pilot study was conducted to pre-test the modified 14-item TCSE tool in ethnic Chinese and non-Chinese. RESULTS: A total of 18 subjects (mean age = 60 years, S.D. = 18.4) participated. Seven subjects (39%) identified themselves as ethnic Chinese. Ten subjects (56%) had experience performing Tai Chi, ranging from 3 months to 17 years (mean = 5.0 years, S.D.=5.0). Half of the subjects reported having a history of hypertension (n = 9, 50%), while nearly one-third reported having high cholesterol (n = 5, 28%). No significant difference in TCSE mean scores was found between ethnic Chinese and non-Chinese (p > 0.05). Internal consistency estimates were very high (TCSE Barriers, r = 0.95; TCSE Performance, r = 0.97). A statistically significant difference was found in the TCSE mean scores between Tai Chi practitioners and non-practitioners (TCSE Barriers, t = -3.3, p = 0.01; TCSE Performance, t = -2.7, p = 0.03), with Tai Chi practitioners reporting higher self-efficacy; thus providing initial evidence of known-groups validity. CONCLUSIONS: Measurement of self-efficacy to overcome barriers to Tai Chi exercise (TCSE Barriers) and self-efficacy to perform Tai Chi (TCSE Performance) functioned well in this sample. The acceptability and feasibility of this tool was established and known-groups validity was confirmed. Further research using this tool among ethnic Chinese with CHD or CHD risk factors, including those with less than high school education or low literacy, is recommended as the next step in development of TCSE.     

Reliability of Bayesian probability analysis for predicting coronary artery disease in a veterans hospital

To assess the accuracy of Bayesian probability analysis for the prediction of coronary artery disease, post-test probabilities were generated by the application of three Bayesian algorithms to the clinical and noninvasive test results of 199 patients undergoing angiography in a veterans' hospital. All assumed conditional independence but each used different pre-test and conditional probabilities. Two statistical approaches were employed: (1) Sorting of patients in ascending deciles of probability and comparing expected and observed probabilities in each decile. (2) Calculation of normally distributed reliability statistics which do not depend on probability subsets and the comparison of resulting probability distributions using these statistics. Both statistical approaches revealed that the Bayesian algorithms overestimated disease probability when it was high and underestimated it when low. Though all three algorithms were frequently incorrect, they differed significantly in their accuracies, suggesting that errors in Bayesian analysis are caused by factors other than the assumption of independence. The errors may be due to differences in sensitivity and specificity of tests applied in different institutions.     

The reliability of probability analysis in the prediction of coronary artery disease in two hospitals

To assess the accuracy of the Bayesian computer program CADENZA for the prediction of coronary artery disease, the authors examined the probabilities generated by the application of this program to the clinical and noninvasive test results of 303 patients in a private referral center and 199 patients in a veterans' hospital. These probabilities were compared with those produced by applying a six-variable discriminant function derived by logistic regression at the private referral center. Two statistical approaches were employed in evaluating the relative performances of the Bayesian program and the discriminant function. The first of these involved the sorting of patients in both test groups into ascending deciles of probability and comparing expected probability with observed angiographic disease prevalence in each decile. The second involved the calculation and comparison of a standardized reliability measure. The latter was significantly lower for the discriminant function both at the private hospital (0.200 for the discriminant function versus -17.5 +/- 1.96 for the Bayesian program) and at the veterans' hospital (-0.8 +/- 1.96 for the discriminant function versus -11.3 for Bayesian program). This suggests that the discriminant function is significantly superior to the Bayesian algorithm CADENZA for predicting coronary artery disease probabilities in subjects who have relatively high pretest disease probabilities.     

Suprasternal Doppler ultrasound for assessment of stroke distance

An assessment of a non-invasive technique for measurement of stroke distance was made using a portable Doppler ultrasound machine. The aim was to determine the measurement error of repeated stroke distance measurements (Within-observer variability) and to assess measurement agreement between two operators (between-observer variability). The measurement error (within-observer variability) for both operators was similar at approximately 2 cm. However, the measurements of the two operators (between-observer variability) did not agree well. Using the mean (SD) of three readings by each operator, the mean difference between the operators was -0.21 cm (1.96) giving a 95% confidence interval for the differences of -4.0 to +3.6 cm. There were significant positive and negative correlations between stroke distance and a variety of variables (age, height, weight, heart rate), but the relations were weak. The results indicate that the Doppler ultrasound technique for measurement of stroke distance would best be used to study trend changes in an individual patient, or subject, by a single operator.     

Prognostic value of exercise tests in male veterans with chronic coronary artery disease

PURPOSE: The authors evaluate the prognostic value of treadmill testing in a large consecutive series of patients with chronic coronary artery disease. Exercise testing is widely performed, but analyses of the prognostic value of test results have largely concentrated on patients referred for the diagnosis of coronary artery disease, patients after an acute coronary event or procedure, or patients with congestive heart failure. METHODS: All patients referred for evaluation at two university-affiliated Veterans Affairs Medical Centers who underwent exercise treadmill tests for clinical indications between 1987 and 2000 were determined to be dead or alive using the Social Security Death Index after a mean 5.8-year follow-up. Patients without established heart disease and those with congestive heart failure were excluded, leaving the target population of those with a history myocardial infarction or coronary intervention. Clinical and exercise test variables were collected prospectively according to standard definitions; testing and data management were performed in a standardized fashion using a computer-assisted protocol. All-cause mortality was used as the endpoint for follow-up. Standard survival analysis was performed including Kaplan Meier curves and the Cox Hazard Model. RESULTS: Of the 1,473 patients with coronary artery disease who had exercise testing, 273 (19%) patients had a revascularization procedure (Revascularization group); 813 (55%) had a history of myocardial infarction, diagnostic Q waves (MI group), or both; and 387 (26%) had a history of myocardial infarction or Q wave and revascularization (Combined group). Mean age of the patients was 61.8 +/- 9 years. A total of 401 deaths occurred during a mean follow-up of 5.8 years with an annual mortality rate of 4.5%. Only two variables, age and maximal exercise capacity, were independently and statistically associated with time to death in all three groups and were the strongest predictors of all cause mortality. CONCLUSION: A simple score based on METs, age, and history of myocardial infarction or diagnostic Q waves can stratify prognosis in patients with chronic coronary artery disease. The score enabled the identification of a group at low risk (32% of the cohort) with an annual mortality rate of 2%, a group at intermediate risk (42% of the cohort) with an annual mortality rate of about 4%, and a group at high risk (26% of the cohort) with an average annual mortality rate of approximately 7%.     

The importance of heart rate recovery in patients with heart failure or left ventricular systolic dysfunction

BACKGROUND: The ability to better predict outcome with exercise testing in patients with heart failure (HF) and left ventricular systolic dysfunction (LVSD) may prove extremely valuable in determining which patients are at increased risk. This study evaluated the ability of heart rate recovery (HRR) to predict outcome in patients with HF and validate previous findings in LVSD. METHODS AND RESULTS: HRR was measured at 1-, 2-, 3-, and 5-minute time points after treadmill testing in 2,193 males being evaluated for chest pain at the Palo Alto and Long Beach VA Hospitals. Left ventricular ejection fraction (LVEF) was calculated using biplane ventriculography and patients were considered to have LVSD if they had an LVEF <50%. Angiographic and clinical data was available for all patients. Of the 2,193 patients, 314 patients had LVSD and 109 had a history of HF. Both HF patients and patients with LVSD with a normal HRR at 2 minutes had improved survival compared with patients that had an abnormal HRR at 2 minutes when adjusted for age and beta-blocker use (HF adjusted odds ratio 0.25, 95% CI 0.10-0.66, P < .006; LVSD alone adjusted odds ratio 0.25, 95% CI 0.13-0.47, P < .0001). Stepwise proportional hazard regression analysis revealed that only 2-minute HRR, age, LVEF, and chronic obstructive pulmonary disorder were significant predictors of mortality in patients with LVSD and only HRR at 2 minutes and LV hypertrophy were significant predictors of mortality in patients with HF. CONCLUSION: HRR is a significant predictor of mortality in patients with HF and patients with LVSD and may be useful in better determining prognosis.