Heart rate recovery is a prognostic tool in patients with heart failure. This study is the first of its kind aimed to identify whether heart rate response during and after the six-minute walking test provides significant prognostic insights. Challenging the distance ambulated approach as a prognostic tool, the heart rate recovery after the six-minute walking test is a powerful prognosticator that performs similarly to the heart rate recovery after maximal exercise and is more accurate than the distance ambulated approach. The six-minute walking test is able to elicit a cardiac response that is similar to that observed during a maximal effort from cardiopulmonary exercise and is able to identify a greater percentage of patients with an abnormal heart rate response. The use of pedometers is well-documented as a measurement tool for increasing physical activity and related health benefits and was a chief measurement tool to assess distance covered in all experiments.
Now that we’ve established heart rate response following the six-minute walking test as a prognostic tool, further research by examining new distances should be implemented. Cardiopulmonary exercise testing is the gold standard of functional assessments considering patients with systolic HF. The six-minute walking test heart rate recovery is a more realistic measurement tool because it doesn’t require maximal exertion from patients. Abnormal heart rate recovery remained a prognostic index despite achieving less than age-predicted maximal HR values. Therefore, depending on symptoms of the patient, the risk of an event during trial periods is reduced by using the six-minute walking test heart rate response going forward.
Interestingly, subjects on beta-blockers were included in the cox-regression model for both the cardiopulmonary exercise and six-minute walking test. It’s no secret that beta-blockers aim to slow the heart rate in subjects with cardiac arrhythmias and post-cardiac infarction. However, test results showed no significant difference between subjects on the beta-blockers and those without it during the cardiopulmonary exercise and six-minute walking test. Limitations involved are that only 16% of subjects were patients with heart failure with a preserved ejection fraction (HFpEF). These patients would suffer from hypertension, be predisposed to diabetes, or be older subjects.
In the future, more research should investigate the relationship between heart rate recovery, distance ambulated, and maximal heart rate and exertion. Distance ambulated is still considered a competent measurement tool to assess risk in patients with heart failure. Based on merging recent and previous research, a spectrum is created. In this meta-analysis, on the low end of distance ambulated is the previous research indicating greater risk of cardiac events. On the high end of distance ambulated is either the maximal heart rate given by calculations with the Karvonen formula or near maximal exertion, or an individual with a high fitness level which would correspond with a faster heart rate recovery. Both which are associated with lower risk of cardiac events. Since all of these predictors of cardiac events are intimately intertwined, it’s difficult to ignore any of them in further research. Creating the whole picture, it’s hard to see how a subject could ambulate a far distance without a significant level of cardiopulmonary fitness. Further, without that level of cardiopulmonary fitness it’s unlikely their heart rate recovery would be quick. Opposite to this, little distance ambulated would likely be associated with poor fitness levels, and therefore a slow heart rate recovery. More research investigating how all three assessments work together to predict cardiac events could improve the measurement and analysis of research data, as well as creating a new research design.
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