Longitudinal Strain Reflects Ventriculoarterial Coupling Rather Than Mere Contractility in Rat Models of Hemodynamic Overload-Induced Heart Failure

Background: Longitudinal strain (LS) is a sensitive marker of systolic function. Recent findings suggest that both myocardial contractility and loading conditions determine LS. The aim of this study was to investigate whether LS reflects the connection of cardiac contractility to afterload (termed ventriculoarterial coupling [VAC]) rather than mere contractility in rat models of hemodynamic overload-induced heart failure (HF).

Methods: Pressure overload-induced HF was evoked by transverse aortic constriction (TAC; n = 14). Volume overload-induced HF was established by an aortocaval fistula (ACF; n = 12). Age-matched sham-operated animals served as controls for TAC (n = 14) and ACF (n = 12), respectively. Pressure-volume analysis was carried out to compute contractility (slope of end-systolic pressure-volume relationship [ESPVR]), afterload (arterial elastance [E_a]), and VAC (E_a/ESPVR). Preload was evaluated by meridional end-diastolic wall stress. Speckle-tracking echocardiography was performed to assess LS.

Results: The TAC group presented with maintained ESPVR, increased E_a, and enhanced meridional end-diastolic wall stress. In contrast, the ACF group was characterized by reduced ESPVR, decreased E_a, and enhanced meridional end-diastolic wall stress. VAC increased in both HF groups. Furthermore, LS was also impaired in both HF models (-5.9 ± 0.6% vs -12.9 ± 0.5%, TAC vs Sham_t [P < .001], and -11.7 ± 0.7% vs -13.5 ± 0.4%, ACF vs Sham_a[P = .048]). Statistical analysis revealed that strain parameters were determined predominantly by afterload in the TAC group and by contractility in the ACF group, while preload had a minor effect. In the entire study population, LS showed a correlation with VAC (R = 0.654, P < .001) but not with ESPVR (R = 0.058, P = .668).

Conclusions: Under pathophysiologic conditions when both contractility and afterload become altered, LS reflects VAC rather than mere contractility.