PURPOSE: Patients with unexplained dyspnea are referred for dynamic evaluation via Cardiopulmonary Exercise Testing (CPET) protocols. Many of these subjects are treated with CSBB. While patients are advised to interrupt their use, not all can do so safely. In order to characterize the common patterns of their influence on CPET measurements when used in conventional doses, the following experiment was performed.
METHODS: 84 test subjects treated with CSBB (48 females, 36 males) underwent CPET in our pulmonary physiology laboratory over a 36 month period. Each had been advised by their treating physicians that interruption would be inadvisable. Following testing, data including work capacity (WC), anaerobic threshold (AT), heart rate reserve (HRR), 02/pulse, dead space to tidal volume ratio (VD/VT) and ventilatory equivalent for carbon dioxide (VE/VC02) were compiled and analyzed.
RESULTS: Analysis of the peak exercise cardiovascular and respiratory indices were analyzed and summarized as follows (note data are expressed as: mean +/- 1 SD for the 84 subjects): WC = 87 +/- 6.5% of V02 max-predicted; AT = 44 +/- 3.6% of V02 max-predicted; 02/pulse = 9.0 +/- 0.8 cc/beat (females) and 12.8 +/- 1.1 cc/beat (males); HRR = 26.4 +/- 4.6%; VD/VT = .22 +/- .03; VE/VC02 = 34 +/- 2.4. A negative correlation between HRR and WC was established - r = .79 (p < .05) but not between HRR and AT r = - .64 (p < .1).
CONCLUSION: CPET recordings of CSBB treated subjects present a consistent and noteworthy pattern. While work capacity is characteristically reduced, the principal hallmark of cardiovascular limitation (reduced AT) may not be apparent. This is likely due to salutary effects on hemodynamics in patients with hypertension and related left ventricular dysfunction that offset a blunted heart rate response (elevated HRR) associated with treatment. Respiratory (ventilatory) function in our test subjects was not notably affected by treatment.
CLINICAL IMPLICATIONS: CPET evalautions in subjects on CSBB is at times unavoidable. Familiarity with characteristic patterns of cardiopulmonary recordings may aid in more accurate interpretation.
DISCLOSURE: O. Khawaja, No Financial Disclosure Information; No Product/Research Disclosure Information