Fixed subaortic stenosis

Undiagnosed sub-valvular aortic stenosis with an associated Ventricular Septal Defect (VSD) presenting late in a multi-parous woman

BACKGROUND

Sub-valvular aortic stenosis is a rare disorder that has a prevalence of 6.5% of all adult congenital heart diseases. The hemodynamic changes that occur in pregnancy with the resultant increase in cardiac output may not well be tolerated by a pregnant woman with sub-valvular aortic stenosis.

CASE PRESENTATION

We report the case of a 34-year-old para 7 (6 alive + 1 dead) who has been experiencing intermittent episodes of easy fatigability on moderate exertion since childhood and had survived 6 prior pregnancies. During her last pregnancy, she started experiencing chest pain, palpitations, dyspnea, orthopnea, and pre-syncope at 36 weeks and had a caesarean section at 37 weeks on account of fetal distress. The post-delivery cardiac evaluation showed severe sub-valvular Aortic stenosis and a ventricular septal defect.

CONCLUSION

Sub-valvular Aortic stenosis may progress slowly in adults and may be tolerated during pregnancy. Despite the rare presentation and contraindication of pregnancy in such a patient, she extraordinarily survived the pregnancy with a healthy baby. Routine cardiovascular assessment during prenatal, ante-natal and post-natal care is highly advocated particularly so in resource-poor settings.

Surgical treatment of recurrent subvalvular discrete membrane and left ventricular outflow tract stenosis in an adult patient with a history of congenital cardiac surgery

Left ventricular outflow stenosis can develop at the supravalvular, valvular, and subvalvular levels. Resection of strictures at the diffuse subvalvular level is very difficult. In such pathologies, Konno-Rastan procedure provides very successful solutions as an anterior aortoventriculoplasty method. In this article, we performed anterior aortaventriculoplasty surgical treatment for tunnel type left ventricular outflow tract stenosis, recurrent subvalvular discrete membrane, and aortic regurgitation in an adult patient with a history of partial atrioventricular septal defect repair and subvalvular discrete membrane resection operation in early childhood. The Konno-Rastan procedure, which we applied to the redo case, which is rarely used in adult patients and rarely seen in the literature, is shared.

Computational Assessment of Valvular Dysfunction in Discrete Subaortic Stenosis: A Parametric Study

PURPOSE

Discrete subaortic stenosis (DSS) is a left-ventricular outflow tract (LVOT) obstruction caused by a membranous lesion. DSS is associated with steep aortoseptal angles (AoSAs) and is a risk factor for aortic regurgitation (AR). However, the etiology of AR secondary to DSS remains unknown. This study aimed at quantifying computationally the impact of AoSA steepening and DSS on aortic valve (AV) hemodynamics and AR.

METHODS

An LV geometry reconstructed from cine-MRI data was connected to an AV geometry to generate a unified 2D LV-AV model. Six geometrical variants were considered: unobstructed (CTRL) and DSS-obstructed LVOT (DSS), each reflecting three AoSA variations (110°, 120°, 130°). Fluid-structure interaction simulations were run to compute LVOT flow, AV leaflet dynamics, and regurgitant fraction (RF).

RESULTS

AoSA steepening and DSS generated vortex dynamics alterations and stenotic flow conditions. While the CTRL-110° model generated the highest degree of leaflet opening asymmetry, DSS preferentially altered superior leaflet kinematics, and caused leaflet-dependent alterations in systolic fluttering. LVOT steepening and DSS subjected the leaflets to increasing WSS overloads (up to 94% increase in temporal shear magnitude), while DSS also increased WSS bidirectionality on the inferior leaflet belly (+ 0.30-point in oscillatory shear index). Although AoSA steepening and DSS increased diastolic transvalvular backflow, regurgitant fractions (RF < 7%) remained below the threshold defining clinical mild AR.

CONCLUSIONS

The mechanical interactions between AV leaflets and LVOT steepening/DSS hemodynamic derangements do not cause AR. However, the leaflet WSS abnormalities predicted in those anatomies provide new support to a mechanobiological etiology of AR secondary to DSS.

Impact of Aortoseptal Angle Abnormalities and Discrete Subaortic Stenosis on Left-Ventricular Outflow Tract Hemodynamics: Preliminary Computational Assessment

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.