Dataset Information

Significance of aortoseptal angle anomalies to left ventricular hemodynamics and subaortic stenosis: A numerical study.

ABSTRACT:

Purpose

Discrete subaortic stenosis (DSS) is an obstructive cardiac disease caused by a membranous lesion in the left ventricular (LV) outflow tract (LVOT). Although its etiology is unknown, the higher prevalence of DSS in LVOT anatomies featuring a steep aortoseptal angle (AoSA) suggests a potential role for hemodynamics. Therefore, the objective of this study was to quantify the impact of AoSA steepening on the LV three-dimensional (3D) hemodynamic stress environment.

Methods

A 3D LV model reconstructed from cardiac cine-magnetic resonance imaging was connected to four LVOT geometrical variations spanning the clinical AoSA range (115°-160°). LV hemodynamic stresses were characterized in terms of cycle-averaged pressure, temporal shear magnitude (TSM), and oscillatory shear index. The wall shear stress (WSS) topological skeleton was further analyzed by computing the scaled divergence of the WSS vector field.

Results

AoSA steepening caused an increasingly perturbed subaortic flow marked by LVOT flow skewness and complex 3D secondary flow patterns. These disturbances generated WSS overloads (>45% increase in TSM vs. 160° model) on the inferior LVOT wall, and increased WSS contraction (>66% decrease in WSS divergence vs. 160° model) in regions prone to DSS membrane formation.

Conclusions

AoSA steepening generated substantial hemodynamic stress abnormalities in LVOT regions prone to DSS formation. Further studies are needed to assess the possible impact of such mechanical abnormalities on the tissue and cellular responses.

SUBMITTER: Shar JA

PROVIDER: S-EPMC10570849 | biostudies-literature | 2022 Jul

REPOSITORIES: biostudies-literature

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Publications

Significance of aortoseptal angle anomalies to left ventricular hemodynamics and subaortic stenosis: A numerical study.

Shar Jason A JA Keswani Sundeep G SG Grande-Allen K Jane KJ Sucosky Philippe P

Computers in biology and medicine 20220515

<h4>Purpose</h4>Discrete subaortic stenosis (DSS) is an obstructive cardiac disease caused by a membranous lesion in the left ventricular (LV) outflow tract (LVOT). Although its etiology is unknown, the higher prevalence of DSS in LVOT anatomies featuring a steep aortoseptal angle (AoSA) suggests a potential role for hemodynamics. Therefore, the objective of this study was to quantify the impact of AoSA steepening on the LV three-dimensional (3D) hemodynamic stress environment.<h4>Methods</h4>A ...[more]

PMID: 35751200

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Project description:Discrete subaortic stenosis (DSS) is an obstruction of the left ventricular outflow tract (LVOT) due to the formation of a fibromuscular membrane upstream of the aortic valve. DSS is a major risk factor for aortic regurgitation (AR), which often persists after surgical resection of the membrane. While the etiology of DSS and secondary AR is largely unknown, the frequent association between DSS and aortoseptal angle (AoSA) abnormalities has supported the emergence of a mechanobiological pathway by which hemodynamic stress alterations on the septal wall could trigger a biological cascade leading to fibrosis and membrane formation. The resulting LVOT flow disturbances could activate the valve endothelium and contribute to AR. In an effort to assess this hypothetical mechano-etiology, this study aimed at isolating computationally the effects of AoSA abnormalities on septal wall shear stress (WSS), and the impact of DSS on LVOT hemodynamics. Two-dimensional computational fluid dynamics models featuring a normal AoSA (N-LV), a steep AoSA (S-LV), and a steep AoSA with a DSS lesion (DSS-LV) were designed to compute the flow in patient-specific left ventricles (LVs). Boundary conditions consisted of transient velocity profiles at the mitral inlet and LVOT outlet, and patient-specific LV wall motion. The deformation of the DSS lesion was computed using a two-way fluid-structure interaction modeling strategy. Turbulence was accounted for via implementation of the k-ω turbulence model. While the N-LV and S-LV models generated similar LVOT flow characteristics, the DSS-LV model resulted in an asymmetric LVOT jet-like structure, subaortic stenotic conditions (up to 2.4-fold increase in peak velocity, 45% reduction in effective jet diameter vs. N-LV/S-LV), increased vorticity (2.8-fold increase) and turbulence (5- and 3-order-of-magnitude increase in turbulent kinetic energy and Reynolds shear stress, respectively). The steep AoSA subjected the septal wall to a 23% and 69% overload in temporal shear magnitude and gradient, respectively, without any substantial change in oscillatory shear index. This study reveals the existence of WSS overloads on septal wall regions prone to DSS lesion formation in steep LVOTs, and the development of highly turbulent, stenotic and asymmetric flow in DSS LVOTs, which support a possible mechano etiology for DSS and secondary AR.

Project description:BACKGROUND:Myocardial fibrosis occurs in aortic stenosis (AS) as part of the hypertrophic response. It can be detected by LGE, which is associated with an adverse prognosis in the form of increased mortality and morbidity. OBJECTIVES:To assess the prevalence of LGE patterns using cardiac magnetic resonance (CMR) in severe AS patients and to study its prognostic significance. METHODS:Patients enrolled into the study from June 2012 to November 2014. All the patients underwent CMR and various patterns of LGE studied. These patients if symptomatic were advised AVR and others were managed conservatively. All patients were followed up and watched for outcomes like mortality, heart failure/hospitalization for cardiovascular cause, fall in left ventricular ejection fraction (LVEF) ?20% and arrhythmia. RESULTS:A total of 109 patients (mean age-57.7±12.5yrs) underwent CMR with 63 males. These patients were followed up for a mean of 13 months. Among 38 patients who underwent AVR, 6 died (5-cardiovascular cause, 1-non cardiovascular). 71 patients were managed conservatively out of which 18 died (17-cardiovascular cause, 1-non cardiovascular cause). LGE patterns were seen in 46 patients (43%); mid myocardial enhancement was seen in 31.1% of cases (33 patients). No LGE pattern was seen in 57%(63 patients). Basal and mid regions were maximally involved with mid myocardial enhancement in 66% & 68.3% respectively. LV ejection fraction (p=0.002), peak aortic systolic velocity (p=0.01) and peak aortic systolic gradient (p=0.02) were the main predictors of LGE. Main predictors of primary outcome were NYHA class [OR- 13.4(2.8-26.1), p?0.001], age- 62±?9.6yrs(p=0.001), EF simpson-50.9±13%(p??0.001), LGE[OR 2.8 (1.27-6.47),p=0.01], number of segments involved [2.37±2.1,P?0.001] & CMR LV mass (151.73±32gms, p=0.007). LGE predicted heart failure/hospitalization for cardiovascular cause [OR- 3.8(1.2-11.9), p=0.01] and fall in LVEF [OR- 5.8(1.5-22.5), p=0.005]. Patients with LGE had 2.87 times risk of adverse outcomes and patients with more than 3 segment LGE involvement had again increased chances for adverse outcomes. CONCLUSIONS:LGE was detected by CMR in 43% of patients with severe AS. It predicted recurrent heart failure, hospitalization for cardiovascular cause and fall in LV ejection fraction. Our study has laid a path to larger prospective studies with long term follow up to assess the prognostic impact of CMR in patients with severe AS.

Dataset Information

Significance of aortoseptal angle anomalies to left ventricular hemodynamics and subaortic stenosis: A numerical study.

Purpose

Methods

Results

Conclusions

Publications

Significance of aortoseptal angle anomalies to left ventricular hemodynamics and subaortic stenosis: A numerical study.

Similar Datasets

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