Kinetic energy of left ventricular blood flow across heart failure phenotypes and in subclinical diastolic dysfunction.

ABSTRACT

Kinetic energy (KE) of intracardiac blood flow reflects myocardial work spent on accelerating blood and provides a mechanistic window into diastolic filling dynamics. Diastolic dysfunction may represent an early stage in the development of heart failure (HF). Here we evaluated the hemodynamic effects of impaired diastolic function in subjects with and without HF, testing the hypothesis that left ventricular KE differs between controls, subjects with subclinical diastolic dysfunction (SDD), and patients with HF. We studied 77 subjects [16 controls, 20 subjects with SDD, 16 heart failure with preserved ejection fraction (HFpEF), 9 heart failure with mildly reduced ejection fraction (HFmrEF), and 16 heart failure with reduced ejection fraction (HFrEF) patients, age- and sex-matched at the group level]. Cardiac magnetic resonance at 1.5 T included intracardiac four-dimensional (4-D) flow and cine imaging. Left ventricular KE was calculated as 0.5 × m × v2. Systolic KE was similar between groups (P > 0.4), also after indexing to stroke volume (P = 0.25), and was primarily driven by ventricular emptying rate (P < 0.0001, R2 = 0.52). Diastolic KE was higher in patients with heart failure than in controls (P < 0.05) but similar between SDD and HFpEF (P > 0.18), correlating with inflow conditions (E-wave velocity, P < 0.0001, R2 = 0.24) and end-diastolic volume (P = 0.0003, R2 = 0.17) but not with average e' (P = 0.07). Diastolic KE differs between controls and heart failure, suggesting more work is spent filling the failing ventricle, whereas systolic KE does not differentiate between well-matched groups with normal ejection fractions even in the presence of relaxation abnormalities and heart failure. Mechanistically, KE reflects the acceleration imparted on the blood and is driven by variations in ventricular emptying and filling rates, volumes, and heart rate, regardless of underlying pathology.NEW & NOTEWORTHY Here we present the first study of left ventricular kinetic energy in individuals with subclinical diastolic dysfunction and in heart failure patients with preserved or impaired systolic function. Kinetic energy differs between groups in diastole, and reflects altered filling and emptying processes. Kinetic energy analysis should be considered in studies seeking to characterize myocardial energetics comprehensively.