Serial measurements of myocardial efficiency in patients with aortic valve stenosis: pathophysiological mechanisms and prognostic implications

In patients with aortic valve stenosis (AS), the pathophysiological abnormalities involved in the transition to heart failure are unclear. As chronic heart failure progresses, the ratio between myocardial stroke work and oxygen consumption, that is, myocardial external efficiency (MEE), steadily deteriorates. However, in patients with AS, it is unknown whether changes in MEE are involved in disease progression. We investigated changes in MEE and whether MEE was associated with long-term prognosis in patients with AS. Ten healthy controls and 38 patients with moderate-to-severe AS and preserved left ventricular ejection fraction ≥ 50% were included in the study. To evaluate MEE, we used serial ¹¹C-acetate positron emission tomography, cardiovascular magnetic resonance imaging, and echocardiography, with a median follow-up period of 2.8 yr. Furthermore, we conducted a long-term follow-up for a median of 5.2 yr to detect cardiac events and relate them to MEE. In patients with AS, MEE increased during follow-up from 25.2% [95% confidence interval (CI): 24.0-26.5%] to 29.5% (95% CI: 27.3-31.8%; <i>P</i> = 0.001) and was higher than healthy volunteers, 19.9% (18.1-21.8; <i>P</i> < 0.001). Patients who experienced a cardiac event during long-term follow-up (<i>n</i> = 24, 63%) had higher baseline MEE, 26.5% (95% CI: 24.6-28.4%), than event-free patients, 23.3% (95% CI: 22.2-24.3%; <i>P</i> = 0.004). In asymptomatic patients with AS, MEE increased over time and high baseline MEE predicted a poor prognosis. Thus, the myocardium displayed an inherent capacity to improve the coupling between oxidative metabolism and contractile function in response to pressure overload.<b>NEW & NOTEWORTHY</b> Patients with aortic valve stenosis can improve myocardial efficiency-delaying heart failure.