Prognostic significance of myocardial energy expenditure and myocardial efficiency in patients with heart failure with reduced ejection fraction

In heart failure with reduced ejection fraction (HFrEF) patients, myocardial blood flow (MBF), myocardial energy expenditure (MEE), myocardial efficiency has been poorly evaluated because of the necessity of invasive procedures in the determination of these parameters. Transthoracic echocardiography (TTE) can provide reliable data for MEE, MBF (via coronary sinus (CS) flows). Also, myocardial efficiency can be evaluated by the MEE to MBF ratio. We aim to assess MBF, MEE and energy efficiency and the prognostic value of these parameters in HFrEF. In this prospective study, a total of 80 patients with HFrEF due to either ischemic or non-ischemic etiology and 20 healthy control subjects were included. Median follow-up duration was 901 (27-1004) days. MBF was calculated via coronary sinus blood flow. MEE was measured from circumferential end-systolic stress, stroke volume and left ventricular ejection time. MEE to MBF ratio was determined as MEf. Primary composite end-point (CEP) was cardiovascular mortality, heart transplantation or mechanical circulatory support. MEE and MEf were lower and MBF per minute was higher in HF group compared to control subjects whereas MBF per 100 g left ventricular mass was not different. MEE and MEf have significantly negative correlation with troponin I, BNP, uric acid and positive correlation with epicardial fat thickness. In Cox regression analysis, per one calorie decrease of MEE was associated 4.3 times increased risk [HR 4.396 (95% CI 1.230-15.716)] and per one percent decrease of MEf was associated 3.3 times increased risk of CEP [HR 3.343 (95% CI 1.025-10.905)]. Our study demonstrated that while MEE and MEf diminished in HFrEF, MBF preserved with the symptomatic progression of HF. MEE and MEf were found to be associated with important prognostic markers and independent predictors of CEP in HFrEF. Evaluation of MEE, MBF and MEf with echocardiography may provide an additional data regarding prognostic assessment of HFrEF population.