Cardiopulmonary exercise testing in patients with 21mm St. Jude Medical aortic prosthesis

Small-sized prostheses may be associated with high transprosthetic gradients, particularly in patients with a body surface area (BSA) >1.70m2, affecting left ventricular mass regression, symptom improvement and long-term survival. However, the influence of such gradients on exercise tolerance has not been clearly defined. The study aim was to verify the utility of cardiopulmonary exercise testing (CPX) in detecting patient-prosthesis mismatch, and to identify the clinical and echocardiographic data that predict exercise tolerance at CPX in patients with a 21mm St. Jude Medical (SJM) aortic prosthesis.

Twenty patients (one male, 19 females; mean age 66 +/- 9 years) with a 21 mm SJM prosthesis were evaluated by means of 2D echocardiography and CPX at 36 +/- 10 months after operation. Patients were divided into groups on the basis of a BSA of <1.70 m2 (group 1, n = 12) or > or =1.70 m2 (group 2, n = 8).

At echocardiography, left ventricular mass reduction was 16 +/- 10% versus 9 +/- 6% in groups 1 and 2, respectively, mean gradient (MG) was 15 +/- 6 versus 17 +/- 4 mmHg (p = NS), effective orifice area index (EOAi) 0.86 +/- 0.10 versus 0.79 +/- 0.09 cm2/m2 (p = 0.05). At CPX, group 2 patients showed a significantly lower exercise duration (p = 0.02), maximum workload (p = 0.02), peak O2 uptake (p = 0.01), anaerobic threshold (AT) (p = 0.03), ventilatory equivalent for CO2 at AT (p = 0.007), and O2 cost of work (p = 0.03). Group 1 patients showed a ventilatory origin for their effort dyspnea, while group 2 patients showed a significant circulatory component. At multivariate analysis, BSA, age, EOAi and MG were independent predictors of CPX results.

In patients with a 21 mm aortic SJM prosthesis and a BSA > or =1.70m2, CPX allows detection of patient-prosthesis mismatch, in terms of impaired exercise tolerance due to circulatory causes. CPX results can be anticipated on the basis of the patient's BSA, age, EOAi and MG. In these patients, technical solutions allowing implantation of a larger prosthesis should be considered whenever an active lifestyle is anticipated after aortic valve replacement.