Myocardial efficiency is an important determinant of functional improvement after aortic valve replacement in aortic valve stenosis patients: a combined PET and CMR study

The pathophysiology underlying aortic valve stenosis (AVS)-induced cardiac dysfunction and reduced exercise capacity is unclear. We hypothesize that improvement of myocardial external efficiency (MEE)—the ratio between external work and myocardial oxygen consumption (MVO₂)—underlies functional improvement of AVS patients after aortic valve replacement (AVR). Therefore, the aim of this proof-of-concept study was to investigate whether myocardial efficiency is reduced in patients with cardiac hypertrophy caused by AVS and to assess the effect of AVR on myocardial efficiency in relation to exercise capacity.

Echocardiography, cardiopulmonary exercise test, [¹¹C]-acetate positron emission tomography and cardiovascular magnetic resonance imaging were performed in 10 AVS patients prior to (pre-AVR) and 4 months after AVR (post-AVR). Fourteen healthy individuals served as control group. MEE was significantly lower in pre-AVR patients (32 ± 7%) than in controls (49 ± 6%). AVR significantly decreased left ventricle mass and MVO₂. Also, external work significantly decreased post-AVR reaching similar values as in controls. AVR significantly improved MEE from 32 ± 7 to 37 ± 5% (P = 0.02). Moreover, significant correlations were present between the AVR-induced increase in MEE and changes in both exercise work (r = 0.74, P = 0.01) and peak VO₂ (r = 0.67, P = 0.03). However, four AVS patients did not show improved MEE, which was associated with no or minimal improvement in exercise parameters.

MEE is significantly reduced in patients with AVS-induced hypertrophy. Improved MEE is an important predictor of AVR-induced improvement of exercise capacity in AVS patients. Future investigation is needed to confirm our observations in a large prospective, multicenter clinical trial.