The Invasive Cardiopulmonary Exercise Test

Abstract

A 71-year-old man was evaluated for a chief complaint of progressive dyspnea on exertion over the previous 5 years. The patient’s medical history is significant for revascularized coronary artery disease, left diaphragmatic paresis, systemic hypertension, and obesity. His medications included aspirin 81 mg daily, metoprolol succinate 100 mg daily, lisinopril 10 mg daily, and simvastatin 20 mg daily. Over the 6 months before his presentation, the patient’s daily aerobic exercise tolerance performed on a stationary bicycle decreased from 30 minutes to 10 minutes in duration because of worsening dyspnea. Echocardiography demonstrated normal biventricular systolic and diastolic function, an estimated pulmonary artery systolic pressure of 43 mm Hg, and the absence of valvular disease or an intracardiac shunt. Pulmonary function testing revealed a moderate restrictive defect. Cardiopulmonary exercise testing was next considered to determine whether a cardiovascular or pulmonary limitation to exercise was present. Based on the available clinical data, we suspected exercise-induced pulmonary arterial hypertension (PAH) or exercise-induced heart failure with preserved left ventricular ejection fraction (HFpEF) as potential pathophysiological mechanism(s) by which to account for the patient’s symptoms. Thus, an invasive cardiopulmonary exercise test (iCPET) was performed (Figure 1), which uses intracardiac hemodynamic and arterial blood gas data generated during exercise from a pulmonary artery and radial catheter, respectively, to diagnose these and other select causes of exertional shortness of breath (Table). View this table: Table. Cardiopulmonary Hemodynamic Criteria for Diagnosing Select Cardiac Limitations to Exercise Figure 1. Invasive cardiopulmonary exercise test results. A , Analysis of the case vignette patient’s key functional performance measures demonstrates that the maximum respiratory exchange ratio, which compares the carbon dioxide (CO2) output to the oxygen (O2) uptake (V CO2:V O2) at maximum exercise is >1.05, indicating an overall level of effort was performed by the patient that was sufficient to define a …