The invasive cardiopulmonary exercise test.

A 71-year-old man was evaluated for a chief complaint of progressive dys-pnea 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 pathophysi-ological 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). Overview Dyspnea is defined as an abnormal or uncomfortable awareness of breathing 1 and may afflict up to one-quarter of the general population. 2 Pathophysiologi-cal perturbations to normal breathing, cardiopulmonary function, or oxygen (O 2) uptake by skeletal muscle cells modulate symptomatic expression of exertional dyspnea. Thus, exertional dyspnea is described universally across the spectrum of cardiopulmonary diseases , as well as in certain diseases of musculoskeletal and neuromuscular function, and in patients with significant anemia. This swath of dyspnea-associated comorbidities sets the framework for a diagnostic dilemma confronted commonly in cardiology and pulmonary practice: determining the contribution of cardiovascular disease to exertional dyspnea in the presence of competing comorbidities associated with breathlessness. iCPET affords the dynamic and simultaneous assessment of cardiovascular, respiratory , and metabolic function during exercise. In most cases, iCPET results inform clinicians regarding dyspnea pathophysiology to provide a definitive diagnosis, even in patients with comorbid cardiovascular and pulmonary disease. Thus, iCPET has evolved as the preferred diagnostic strategy for patients in whom the predominate mechanism of dyspnea is unresolved. 3 Moreover, iCPET is …