We aimed to clarify the predictors of death or heart failure (HF) in elderly patients who undergo transcatheter aortic valve replacement (TAVR).Methods and Results:We prospectively enrolled 83 patients (age, 83±5 years) who underwent transthoracic echocardiography (TTE) and cardiopulmonary exercise testing (CPET) with impedance cardiography post-TAVR. We investigated the association of TTE and CPET parameters with death and the combined outcome of death and HF hospitalization. Over a follow-up of 19±9 months, peak oxygen uptake (V̇O) was not associated with death or the combined outcome. The minimum ratio of minute ventilation (V̇E) to carbon dioxide production (V̇CO) and the V̇E vs. V̇COslope were higher in patients with the combined outcome. After adjusting for age, sex, Society of Thoracic Surgeons score and peak V̇O, ventilatory efficacy parameters remained independent predictors of the combined outcome (minimum V̇E/V̇O: hazard ratio, 1.108; 95% confidence interval, 1.010-1.215; P=0.031; V̇E vs. V̇COslope: hazard ratio, 1.035; 95% confidence interval, 1.001-1.071; P=0.044), and had a greater area under the receiver-operating characteristic curve. The V̇E vs. V̇COslope ≥34.6 was associated with higher rates of the combined outcome, as well as lower cardiac output at peak work rate during CPET.In elderly patients, lower ventilatory efficacy post-TAVR is a predictor of death and HF hospitalization, reflecting lower cardiac output at peak exercise.