Submaximal Cardiopulmonary Exercise Testing for the Evaluation of Unexplained Dyspnea

Gas exchange measurements obtained during submaximal exercise have been shown to provide prognostic and diagnostic information in patients with heart failure (HF) and to differentiate heart versus lung limitations in patients with unexplained dyspnea. The aim of our study was to assess the clinical utility of submaximal cardiopulmonary exercise testing using the Shape-HF equipment in identifying the cause of unexplained dyspnea.A total of 65 patients underwent Shape-HF tests from September 2010 to June 2011 for unexplained dyspnea at our center.Of 65 patients, 39 were men and 26 were women. In this study, 23 patients had preexisting asthma or chronic obstructive pulmonary disease (COPD); 19 patients had a pacemaker (8), an implantable cardioverter defibrillator (2), or a cardiac resynchronization therapy defibrillator (CRT-D) (9). The study revealed that submaximal cardiopulmonary exercise testing provided supportive clinical data for deconditioning, pulmonary limitations (eg, COPD, interstitial lung disease, sleep apnea), pulmonary hypertension, and chronotropic incompetence in 21.5%, 23.1%, 13.8%, and 6.2% of patients, respectively. Pulmonary hypertension was confirmed in 55% of patients by echocardiography and lung problems were confirmed in 40% of patients by pulmonary function test and sleep study. Of nine patients with an implanted CRT-D, optimization of atrioventricular and interventricular programming was performed in seven (78%) using gas exchange monitoring while performing a steady state, low-level treadmill walk.Submaximal cardiopulmonary exercise testing has strongly suggested the diagnosis of COPD, interstitial lung disease, pulmonary hypertension, and deconditioning and has led to appropriate testing. Based on prior studies, we also used Shape-HF for its approved purpose of optimizing CRT-D programming in patients with HF, leading to clinical improvement.