In hypertrophic cardiomyopathy (HCM) longitudinal systolic left ventricular (LV) function is frequently depressed despite preserved LV ejection fraction and has prognostic impact.
Aim: In this echocardiographic study predictors of longitudinal LV systolic function in HCM patients were evaluated including coronary microcirculatory function assessed as coronary flow reserve (CFR) in left anterior descending coronary artery (CFR-LAD).
Methods: in 34 pts with asymmetric HCM (mean age 50 ± 15 yrs; 56% female; 8 pts with left ventricular outflow track obstruction) and 20 matched control comprehensive transthoracic echocardiographic examination was done including measurement of CFR-LAD and Vector Velocity Imaging (VVI) analysis of peak longitudinal systolic strain (S; %) and strain rate (SR; 1/s) on endocardial (endo) and epicardial (epi) level. CFR-LAD was defined as ratio between maximal velocity of coronary blood flow during diastole in rest and during maximal hyperemia induced by i.v. infusion of adenosine.
Results: HCM pts had impaired longitudinal S endo (-11.89 ± 2.78 vs -19.23 ± 3.6, p<0.001) and S epi (7.15 ± 1.93 vs 15.38 ± 3.9, p<0.001) as well as SR endo (-0.73 ± 0.17 vs -1.27 ± 0.16, p<0.001) and SR epi (-0.47 ± 0.015 vs -0.97 ± 0.19, p<0.01). CFR-LAD was significantly impaired in HCM patients (2.16 ± 0.53 vs 3.34 ± 0.67, p<0.001) and significantly correlated with S endo (r=-0.508, p=0.004), S epi (r=-0.387, p=0.035) and SR endo (r=-0.475, p=0.007). In linear regression analysis significant univariate predictors of S endo were: indexed LV mass (g/m2 BSA) (B=0.399, CI 0.003-0.053, p=0.029), indexed left atrial volume (ml/m2 BSA) (B=0.365, CI 0.003-0.171, p=0.044), ratio E/Eprim (B=0.501, CI: 0.169-0.817, p=0.004) and CFR-LAD (B=-0.508, CI:-4.137 to -0.893, p=0.004). Significant univariate predictors of SR endo were: indexed LV mass (g/m2 BSA) (B=0.434, CI 0.000-0.003, p=0.017), indexed left atrial volume (ml/m2 BSA) (B=0.354, CI 0.000-0.011, p=0.051), ratio E/Eprim (B=0.577, CI:0.017-0.055, p=0.001) and CFR-LAD (B=-0.475, CI:-0.253 to -0.044, p=0.007). In multivariate model independent predictor of S endo was CFR-LAD (B=-1.854, CI -3.644 to -0.065, p=0.043) and independent predictor of SR endo were E/Eprim (B=0.027, CI:0.006-0.047, p=0013) and CFR-LAD (B=-0.102, CI:-0.203 to 0.000, p=0.050).
Conclusion: Important determinants of impaired longitudinal LV systolic function in HCM patients are LV mass, LV filling pressure and impaired coronary microcirculatory function. Microvascular abnormalities in HCM contribute to ischemia and impaired longitudinal systolic LV function independently from other parameters.