Unexplained Dyspnea and Cardiopulmonary Exercise Testing: Rationale for a Dyspnea Clinic

ABSTRACT Objective To describe the experience of a tertiary-care center in the management of patients with unexplained dyspnea referred for cardiopulmonary exercise testing (CPX). Methods All consecutive adults with unexplained dyspnea who underwent CPX at a single tertiary referral center over a ten-year period were included from a prospective registry. We collected data on final diagnosis, routine labs and diagnostic testing including stress/resting echocardiography performed within 6 months of CPX. Results From 2008 to 2019, 156 patients with unexplained dyspnea were referred for CPX with no prior history of cardiovascular disease, lung disease or neuromuscular disease. A 4-fold increase in referrals was noted during this time period. Analysis of diagnostic work-up revealed marked heterogeneity, particularly according to the specialty of the referring physician. Among the 134 patients who achieved an adequate level of exertion during CPX, 24 (17.9%) and 30 (22.4%) patients had an abnormal age-predicted peak VO 2 of < 80% according to Wasserman’s and FRIEND equations respectively. Further analysis revealed 22.5% of patients had a VE/VCO2 slope > 34, suggesting ventilatory inefficiency. Subgroup analysis of 108 patients with complete left ventricular (LV) diastology revealed 13% of patients with a final diagnosis of unexplained dyspnea after CPX were found to have underlying diastolic dysfunction. Conclusions Our study illustrates an increase in CPX referrals for unexplained dyspnea and associated heterogeneity in diagnostic testing in this population. There is a need for an integrated dyspnea clinic to standardize workflow and facilitate early diagnosis for these patients.