Hemodynamic determinants of left atrial strain in patients with hypertrophic cardiomyopathy: A combined echocardiography and CMR study

Background Left atrial (LA) strain is associated with symptomatic status and atrial fibrillation in patients with hypertrophic cardiomyopathy (HCM). However, hemodynamic determinants of LA reservoir (LARS), conduit, and pump strains have not been examined and data are needed on the relation of LA strain with exercise tolerance in HCM. Methods Fifty HCM patients with echocardiographic and CMR imaging within 30 days were included. Left ventricular (LV) volumes, mass, EF, scar extent, extracellular volume fraction (ECV), and LA maximum volume were measured by CMR. Echo studies were analyzed for mitral inflow, pulmonary vein flow, mitral annulus tissue Doppler velocities, LV global longitudinal strain, and LA strain. Twenty six patients able and willing to exercise underwent cardiopulmonary stress testing for peak oxygen consumption (MVO2), and VE/VCO2 slope. Patients were followed for clinical events. Findings LARS was significantly associated with indices of LA systolic function, LV GLS, and LV filling pressures (P<0.05). Conduit strain was significantly associated with mitral annulus early diastolic velocity and ECV, whereas LA pump strain was determined by LA systolic function and indices of LV end diastolic pressure (all P<0.05). LARS and conduit strain were significantly higher in patients who achieved ≥80% of MVO2. LARS, conduit, and pump strains were significantly associated with atrial fibrillation (P<0.05). Conclusions LV structure, systolic and diastolic function, and LA systolic function determine the 3 components of LA strain. LA strain is associated with exercise tolerance and clinical events in patients with HCM.

Fick principle and exercise pulmonary hemodynamic determinants of the six-minute walk distance in pulmonary hypertension

The six-minute walk test is widely used to assess the severity and prognosis of pulmonary hypertension. However, the pathophysiology underlying a compromised six-minute walk distance is incompletely characterized. The purpose of this study is to evaluate the Fick principle and pulmonary hemodynamic determinants of the six-minute walk distance in patients with suspected pulmonary hypertension. Twenty-nine patients were retrospectively studied and underwent a right heart catheterization for the evaluation of suspected pulmonary hypertension. With the pulmonary artery catheter in place, patients were moved to a treadmill and completed a six-minute walk test. Fick cardiac output and indices of right heart afterload were calculated using continuous measurements of pulmonary vascular pressures, gas exchange, and mixed venous blood samples. Fifteen subjects who walked ≤ 348 m were compared to 14 subjects who walked > 348 m. Systemic oxygen delivery was impaired in six-minute walk distance ≤ 348 m compared to six-minute walk distance > 348 m (15.2 ± 6.2 vs. 23.2 ± 6.8 mL/kg/min, p < 0.01). Impaired oxygen delivery was due to a depressed cardiac index and decreased cardiac reserve demonstrated by the change in the stroke volume index (3.0 ± 14 vs. 17 ± 15 mL/min/m2, p = 0.02). The six-minute walk distance positively correlated with oxygen delivery ( r = 0.501, p = 0.006) and inversely correlated with oxygen extraction ( r = 0.369, p = 0.049). A decreased six-minute walk distance was associated with an increased total pulmonary resistance ( r = 0.502, p = 0.006) and pulmonary vascular resistance ( r = 0.530, p = 0.003). In patients with suspected pulmonary hypertension, a decreased six-minute walk distance is due to compromised oxygen delivery, decreased cardiac reserve, and increased right ventricular afterload.

P1515 Hemodynamic determinants of tricuspid annular pulmonary systolic excursion (TAPSE)/ systolic pulmonary arterial pressure (SPAP) ratio in Heart Failure with reduced Ejection Fraction

Background the TAPSE/SPAP ratio has gained a role as an easy-to-use surrogate of right ventricle-to-pulmonary circulation (RV-PC) coupling, showing a strong prognostic significance in heart failure (HF) patients. The hemodynamic determinants of TAPSE/SPAP ratio, as assessed by invasive approach, have not been fully clarified. Aim To identify the right heart hemodynamic variables correlated with TAPSE/SPAP in a HF with reduced EF (HFrEF) cohort, both at rest and during exercise. Methods 30 HFrEF patients (age 68 ± 10 years LV EF 28 ± 7) underwent to rest and exercise echocardiography and performed right heart catheterization within 24 hours. Bivariate correlations between TAPSE/SPAP ratio (at rest and during exercise), right heart hemodynamic variables, RV systolic function and NTproBNP have been explored. Results TAPSE/SPAP ratio at rest showed a moderate correlation with pulmonary artery wedge pressure (PAWP: r= 0.441; p= 0.039), pulmonary artery pressures (PAP systolic: r = 0.481; p= 0.026; PAP diastolic: r= 0.434; p= 0.043; mPAP: r= 0.476; p= 0.025), pulmonary vascular resistance and compliance (r= 0.475; p= 0.041). A stronger correlation was identified with right atrial (RAP systolic: r= 0.586; p= 0.017; RAP diastolic: r= 0.681; p= 0.006) and right ventricular pressures- in particular diastolic ones (RVP systolic: r= 0.584; p= 0.004; RAP diastolic: r= 0.652; p= 0.002). No significant correlation with NTproBNP and RV 3D EF emerged. Exercise TAPSE/SPAP ratio significantly correlated with right atrium (RAP systolic: r= 0.564; p= 0.036) and right ventricle systolic pressures only (RVP systolic: r= 0.789; p&lt; 0.001). Conclusions TAPSE/SPAP ratio at rest showed a stronger correlation with invasively derived diastolic right heart pressure rather than pulmonary vascular bed pressures. A similar correlation was also observed for exercise TAPSE/SPAP ratio. This tight correlation with RV, rather than with vascular pressures, supports the significance of this ratio as a marker of RV adaptation to vascular overload.