Prolonged QRS duration (QRS >/=170 ms) and left axis deviation in the presence of left bundle branch block: A marker of poor left ventricular systolic function?

BACKGROUND: Left bundle branch block (LBBB) is commonly associated with structural heart disease and left ventricular dysfunction. We propose that the QRS duration and degree of left-axis deviation (LAD) identify significant left ventricular systolic dysfunction in patients with LBBB. METHODS: In this prospective study the ejection fraction (EF) of 300 consecutive patients with LBBB was evaluated by echocardiography. The relationship between QRS duration and LAD (axis between -30 degrees and -90 degrees ) and EF were derived. RESULTS: There was no significant difference in age, sex, presence of ischemic or nonischemic cardiomyopathy and valvular heart disease, and EF among the patients with or without LAD. The EF of patients with QRS >/=170 milliseconds with LAD (n = 20) and without LAD (n = 18) was 25% +/- 16% and 23% +/- 13%, respectively (P =.71). The mean EF (24% +/- 10%) of the patients with a QRS duration of >/=170 milliseconds (n = 38) was significantly lower than the mean EF (36% +/- 16%) of the patients with a QRS duration of <170 milliseconds (n = 262, P <.015). The QRS duration also had a significant (P <.001) inverse correlation with EF (R = 0.37, adjusted R (2) = 0.13, SE of estimate = 16.21). However, the QRS axis was not significantly correlated with EF and did not have added predictive value. CONCLUSIONS: The QRS duration has a significant inverse relationship with EF and prolongation of QRS duration (>/=170 milliseconds) in the presence of LBBB is a marker of significant left ventricular systolic dysfunction. The presence of LAD in LBBB does not signify a further decrease in EF.

A submaximal treadmill test for developing target ratings of perceived exertion for outpatient cardiac rehabilitation.

For patient populations whose heart rates cannot be used to regulate exercise intensity, the Borg Rating of Perceived Exertion (RPE) Scale is the preferred way to prescribe exercise intensity. Individual perceptual variations are best quantified by measuring perceptual intensity during maximal exercise testing; however, many situations require a submaximal protocol. Here, a submaximal treadmill procedure for establishing individualized target Ratings of Perceived Exertion is described. Target ratings of exertion were developed for outpatient cardiac rehabilitation patients using the new method and compared to target Ratings of Perceived Exertion obtained using standard techniques. A total of 144 target ratings at intensities ranging from 50% to 85% VO2max were compared. Over-all, the average difference between the two methods was 0.27 units and was not significant at any intensity. Therefore, the Treadmill Slope Method appears to be a valid submaximal test for generating target Ratings of Perceived Exertion for outpatient cardiac rehabilitation patients.

Three-point method of prescribing exercise with ratings of perceived exertion is valid for cardiac patients.

It is often difficult to use heart rate to prescribe exercise for cardiac patients due to the effects of medications and procedures such as cardiac transplantation. Ratings of Perceived Exertion (RPE) is the preferred method of regulating exercise intensity in these situations. An RPE-based exercise prescription has previously depended on perceptual data from a maximal Graded Exercise Test (GXT). Recently, using 13 healthy subjects, we validated a Three-point RPE for prescribing exercise using RPE which can be used when ratings from a GXT are not available Currently, we examined the accuracy of this method for developing target RPEs for patients in Phase II cardiac rehabilitation. Such target RPEs did not differ from those obtained using standard procedures. We conclude that the Three-point Method is valid for preparing RPE-based exercise prescriptions for Phase II cardiac rehabilitation patients.

The slope method for prescribing exercise with ratings of perceived exertion (RPE).

The Borg Ratings of Perceived Exertion scale (RPE) has been shown to be a valuable tool for prescribing exercise; however, use of RPE-based exercise prescriptions in field settings has often been problematic because RPE data derived from maximal exercise testing are needed. We describe a simple method for obtaining target RPEs for exercise training from submaximal exercise data. Target RPEs for 50%, 60%, 70%, and 85% VO2 peak exercise intensities obtained using the new method did not differ significantly from those obtained using data from a maximal graded exercise test. The mean difference was less than one RPE unit and was not significant (p < .05). Therefore, the Slope Method appears to be valid for developing RPE-based exercise prescriptions.

A new method for prescribing exercise: three-point ratings of perceived exertion.

An accurate exercise prescription for ratings of perceived exertion has previously depended on data from a maximal graded exercise test during which RPE was measured. In many clinical settings RPE is not measured; in many fitness settings maximal testing is not feasible. A new method using treadmill speed or power output of a cycle ergometer at an RPE of 13 from a submaximal test which can be used in these situations is described. We evaluated the accuracy of this method at 50%, 60%, 70%, and 85% VO2max. A total of 160 target RPEs were developed using traditional procedures and the new method. No significant differences between RPEs obtained with the two techniques were found. The mean difference was less than one unit of RPE. It appears that the new method is valid for intensities of 50% to 85% VO2max and that data from either the cycle ergometer or the treadmill can be used to prepare exercise prescriptions.

Cardiac intracellular regulation: exercise effects on the cAMP system and A-kinase.

The effects of acute and chronic exercise on 3'5'-adenosine monophosphate (cAMP) concentration, adenylate cyclase activity, cAMP-phosphodiesterase (PDE), and cAMP-dependent protein kinase (A-kinase) activity are reviewed. During very mild- to moderate-intensity exercise with durations of up to 1 h, the cAMP concentration within the myocardium is related to the intensity of exercise. At higher intensities or during very long-duration exercise, this does not seem to be the case. The mode of exercise does not seem to be a significant factor in altering cardiac cAMP concentration. Duration is more important than intensity in determining cAMP-PDE activity. Post-exercise increases in cAMP-PDE are very similar in trained animals, independent of duration and intensity of work. These increases are attenuated and less variable as compared with untrained animals. The activity of A-kinase seems to increase with exercise training. The extent of the increase in A-kinase activity is likely dependent on the duration (and perhaps the intensity) of training and is of greater magnitude than the changes in the other enzymes of the cAMP system.

Is exercise indicated for the patient diagnosed as anorectic?

1. Anorexia nervosa is a disorder characterized by voluntary decreases in food intake resulting in negative caloric balance and dramatic loss of body weight. 2. Aerobic exercise may be contraindicated in patients diagnosed with anorexia because of the high caloric cost and the possibility of overindulgence. 3. Calorically modest weight lifting exercises to increase lean body mass might be useful in increasing compliance with therapy by ensuring that the weight gained is distributed in a more aesthetically appealing manner.

Accuracy and reproducibility of an exercise prescription based on Ratings of Perceived Exertion for treadmill and cycle ergometer exercise.

The accuracy of regulating exercise intensity by Ratings of Perceived Exertion (RPE) was examined. Subjects underwent 4 production trials, 2 on a treadmill (P1A, P1B) and 2 on a cycle ergometer (P2A, P2B). 9 untrained subjects used only their perceptions of effort to regulate exercise intensity. Target intensity was the RPE equivalent to 60% VO2max. Exercise intensity (VO2) during P1A, P1B, and P2A did not differ from the target, but during P2B was lower than target. During P1A and P1B heart rate did not differ from the target but was lower than target during P2A and P2B. RPE seems a valid means of regulating exercise intensity during repeated bouts of treadmill exercise at 60% VO2max; however, exercise intensity during repeated bouts on the cycle ergometer may be lower than target.

The validity of regulating exercise intensity by ratings of perceived exertion.

The purpose of this investigation was to examine the regulation of exercise intensity by using Ratings of Perceived Exertion (RPE). The RPE equivalent to 50% and 70% VO2max was estimated by using standard clinical protocols on a treadmill and cycle ergometer. Subjects then produced the target RPEs on these modalities. Physiological validity of perceptually regulated exercise intensity was determined by comparing VO2 and heart rate between estimation and production trials at the same relative intensity. With one exception, RPE was found to be a valid means of regulating exercise intensity both intra- and intermodally at 50% and 70% VO2max. Perceptual regulation of intramodal treadmill exercise was not valid at 70% VO2max in that both VO2 and heart rate were significantly lower during production than estimation. The present results also indicate that target RPE estimated during a cycle ergometer graded exercise test is more accurate for regulating exercise intensity than when the target RPE is estimated during a treadmill test. The lower accuracy found for treadmill production at the higher exercise intensity may have been caused by the use of a test protocol during the estimation trial that included relatively slow speeds and large inclines. In general, RPE provide a physiologically valid method of regulating exercise intensity.