Association of Active and Passive Components of LV Diastolic Filling With Exercise Intolerance in Heart Failure With Preserved Ejection Fraction. Mechanistic Insights From Spironolactone Response
OBJECTIVES:This study sought to investigate the association of left ventricular (LV) untwisting rate (UT) and E/e' ratio with the response of exercise capacity to spironolactone in heart failure with preserved ejection fraction (HFpEF). BACKGROUND:In most patients with HFpEF, LV filling abnormalities represent a central component in the development of dyspnea. LV diastolic filling is determined by the interplay of passive (LV stiffness and myocardial collagen content, reflected by E/e' ratio) and active myocardial properties (UT, a precursor to isovolumic pressure decay and contributor to diastolic suction). METHODS:In 194 patients with HFpEF (64 ± 8 years), a complete echocardiogram (including assessment of myocardial deformation and rotational mechanics) was performed. Echocardiography following maximal exercise was undertaken to assess LV systolic and diastolic responses to stress. A subset of 105 patients with an exercise-induced increase in estimated LV filling pressure were randomly assigned to spironolactone 25 mg (n = 51) or placebo (n = 54) for 6 months. RESULTS:Baseline peak Vo2 was associated with UT (β = 0.19; p = 0.01) and E/e' (β = -0.16; p = 0.03), independent of clinical data and exercise reserve in longitudinal deformation and ventricular-arterial coupling. An increase in peak Vo2 with treatment was independently associated with changes in UT (β = 0.28; p = 0.003) and exertional increase in E/e' (β = -0.23; p = 0.01) from baseline to follow-up. A significant interaction with the use of spironolactone on peak Vo2 was found for E/e' (p = 0.02) but not for UT (p = 0.62). CONCLUSIONS:Both active and passive determinants of LV filling, as reflected by UT and E/e', contribute to reduced exercise capacity in HFpEF. Improvement in functional capacity with a 6-month therapy with spironolactone is associated with improvements in both indices. However, the possible mediating effect of this medication is observed only on E/e'.