Thursday, 28 September 2017

The Basal, Peak and Maximum Heart Rate Determinants of the Cardiac Patients Who Underwent Dobutamine Stress Echocardiography

It is too hard to determine the individual heart rate changes even by an experienced heart specialist. Practically, there are many determinants for a heart rate to slow down, or speed up, or vary inexplicably. The determinants are not well-known in the heart disease literature. The maximum, peak and basal heart rates are generally used values in clinical medicine and physiology. Generally, the percentage of peak, or maximum, or a fixed percentage of heart rate is used to prescribe the intensity of exercise, or medicine in both the rehabilitation programs and the disease prevention. It is known that a delayed heart rate recovery during the first and second minute after acute exercise is an independent predictor of overall mortality. The peak, or maximum, or basal heart rate is widely used as a criterion for achieving peak exertion in the determination of maximal aerobic capacity. 

Recently, some longitudinal and cross-sectional studies have pointed that aerobic endurance training accelerates heart rate recovery after exercise in healthy subjects. In many clinical settings, exercise testing is not used if subjects attain an arbitrary percentage of their age-predicted maximal heart rate . In earlier research articles, mainly metaanalysis and regression analysis have been used to identify the determinants of heart rates, assuming the response variance is constant. Note that the three heart rates basal, peak and maximum are positive and heterogeneous. For a positive response variable, the variance may be non-constant, due to variance-to-mean relationship. Such data set should be analysed using joint Log-normal and gamma models. The current data sets (basal, peak and maximum) are positive, their variances are non-constant, distributions are non-normal, and the previous statistical methodologies are inappropriate. In addition, best of our knowledge, there is little study of heart rates for the DSE data. These issues have motivated us to locate the heart rate (basal, peak and maximum) determinants of the DSE data set. 

The present report aims to examine the following hypotheses. What are the determinants of the basal, or peak, or maximum heart rate of the DSE data set? What are the associations of the determinants with the basal, or peak, or maximum heart rate? What are the effects of the determinants on the basal, or peak, or maximum heart rate? Answer of these hypotheses are little known in the cardiology literature. These issues are addressed in the current report.Some continuous positive responses such as basal, peak, and maximum heart rates have non-normal error distributions. The class of generalized linear models is used for analysing such data. In practice, the gamma and the log-normal distributions are often used in modelling positive data. For some positive response variables, it is often observed that there exists a variance-to-mean relationship, consequently the response variance may be non-constant.

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