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

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 VO2 of 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.