Medical Products News

Background
Stress testing the cardiovascular patient or those suspected of cardiovascular disease has remained a staple of diagnostic cardiology for decades. The predominant method of inducing physiological stress for the purpose of observing cardiovascular adaptations utilizes a treadmill and one of several empirically validated protocols. It has been established that many patients are unable to complete a standard treadmill stress test for a variety of reasons including deconditioning, comorbidities, orthopedic limitations, etc. It is hypothesized that stress testing using alternative methodologies may allow a larger percentage of the patient population to be tested and to reach a maximal (clinically relevant) test.

Methods
80 subjects with severe cardiovascular disease (post revascularization, CHF, or history of acute events) were enrolled in this clinical cohort study. Subjects at the same disease level who had previously completed a treadmill based exercise stress test at the South Carolina Heart Center (Columbia, SC) using the Bruce exercise protocol upon entry to cardiac rehabilitation were enrolled retrospectively to compose the control group for this analysis (n = 40). The experimental cohort (n =40) was comprised of subjects having clinically severe cardiovascular disease that were stress tested using the RHE cycle and the RHE exercise stress testing protocol.
Data analysis were conducted at the South Carolina Heart Center and descriptive statistics as well as two-sample T-testing for cohort comparisons of like variables were employed. Statistical significance was attained at p .05.

Findings

· The RHE cycle and stress testing protocol allowed a significantly higher percentage of subjects with clinical cardiovascular disease to achieve a maximal stress test when based upon RER (RER > 1.1).
· The mean percentage of maximal RER attained was significantly higher among the experimental cohort.
· The RHE cycle and stress testing protocol allowed a significantly higher percentage of subjects with clinical cardiovascular disease to achieve a maximal stress test when based upon HR (HR > 90% of age predicted maximum heart rate).
· The mean percentage of maximal HR attained was significantly higher among the experimental cohort.
· The RHE cycle and stress testing protocol allowed 85% of subjects with severe cardiovascular disease to attain a maximal stress test.
· The RHE cycle and stress testing protocol allowed 33% more severely diseased subjects to reach a maximal stress test than the treadmill when max was defined by RER.
· The RHE cycle and stress testing protocol allowed 33% more severely diseased subjects to reach a maximal stress test than the treadmill when max was defined by heart rate.
· The percentage of VO2 max attained and mean absolute VO2 were not statistically different among cohorts.
· Anaerobic threshold was met at an earlier percentage of VO2 max among experimental subjects suggesting that these subjects may be working harder at earlier stages of the testing protocol.
· Subjects tested via the RHE cycle and stress testing protocol were able to exercise for a significantly longer time than those tested via treadmill.
· The RHE cycle and stress testing protocol caused a significant reduction in the number of submaximal terminations due to fatigue among this severely diseased population.
· Subjects with severe cardiovascular disease who were tested using the RHE cycle and stress testing protocol reported the test/protocol as being significantly easier/less demanding than the treadmill and Bruce protocol.

Quality Control Suggestions
Comments presented for improvement of the RHE cycle by tested subjects and research staff included:
· Seat adjustment is difficult
· Add safety straps to foot pedals to reduce the potential of injury
· Program test protocols into computer to eliminate manual adjustment
· Reduce EKG artifact

Conclusions
This clinical trial investigating the efficacy of the RHE cycle and stress testing system among a severely diseased population (i.e. cardiac rehabilitation, post revascularization, post acute events, etc.) serves to establish validity and diagnostic value of the RHE protocol and stress testing system across the spectrum of patients having severe cardiovascular disease. The RHE system allows a greater percentage of patients to reach a maximal exercise stress test with diminished perceived exertion, thereby reducing the number of submaximal terminations and the resultant need for pharmacological stress tests.