Unfavorable systemic and coronary hemodynamic profile of left ventricular hypercontractile phenotype in hypertrophic cardiomyopathy
Background
The left ventricular (LV) hypercontractile phenotype (HP) plays a critical role in hypertrophic cardiomyopathy (HCM) and is usually identified with the left ventricular outflow tract gradient (LVOTG).
Purpose
To assess the systemic and coronary hemodynamic profile associated with HP identified with increased LV elastance (also known as force) at rest in patients with HCM.
Methods
We enrolled 1248 HCM patients (age 50 ± 15 years, 798 males, 64%) with ejection fraction (EF) ≥50%, referred for rest transthoracic echocardiography (TTE) in 14 quality-controlled sites from 7 countries TTE assessment included LVOTG, EF, and LV force (systolic blood pressure + LVOTG/LV end-systolic volume, mmHg/mL). Volumetric echocardiography with Simpson’s method was used to measure EF from end-diastolic volume (EDV) and end-systolic volume (ESV), stroke volume (SV), arterial elastance (AE) and ventricular-arterial coupling (VAC). We also assessed resting peak diastolic coronary flow velocity (D-CFV) in the mid-distal left anterior descending artery in a subset of 275 patients.
Results
EF equaled 68 ± 7%, force = 6.8 ± 5.3 mmHg/ml and LVOTG = 22 ± 28 mmHg. HP was identified as the highest quartile of force (> 7.85 mmHg/ml, mean value= 13.3 ± 7.0). HP showed the lowest SV (46 ± 18 ml) and EDV (61 ± 20 ml), with the highest AE (3.19 ± 1.35 mmHg/ml) and VAC (3.46 ± 1.59) compared to other quartiles (p<0.001) ( see Picture) . D-CFV was not higher in patients with HP (n = 65) compared to those (n = 210) without HP (41± 11 vs 38 ± 14 cm/s, p=ns, but higher in comparison to joint first and second Force quartile (n=122) vs 37 ±14 p =0.0472). Table displays the demografic, clinical and TTE parameters related to HP (Table). In multivariate logistic analysis 4 independent predictors of HP were identified: SBP >130 mmHg with OR 2.5, female sex with OR 5.4, LV EF >70% with OR 6.1 and LVOTG >30 mmHg with the highest OR = 6.3. Conclusion: HCM patients with HP exhibit a distinctive systemic hemodynamic and coronary physiology profile, characterized by low SV, high VAC, and supranormal baseline D-CFV compared to non-HP patients. These findings suggest reduced cardiovascular efficiency and increased myocardial oxygen demand, possibly detrimental over time.