Introduction
An uncommon condition that affects newborns is subvalvular aortic stenosis (SAS), sometimes known as subaortic stenosis. Typically, a membrane below the aortic valve prevents blood flow across the left ventricular outflow tract. Although it is categorized as a congenital cardiac abnormality, its sluggish progression, high rate of postoperative recurrence, and rarity at birth and infancy suggest that it may be an acquired problem.
What Is Subaortic Stenosis?
A constriction (stenosis) of the aortic valve's surrounding tissue results in subaortic stenosis, partially blocking or obstructing blood passage through the heart. It can be mild, moderate, or severe; if it is moderate or severe, the heart may have to work harder, which might harm its health.
What Causes Subaortic Stenosis?
Several causes can lead to permanent subvalvular aortic stenosis, such as underlying left ventricular outflow tract shape that increases turbulence at the outflow tract, hemodynamic abnormalities observed in other cardiac diseases, or hereditary factors. A chronic flow disturbance may be brought on by a narrow LVOT, an enlarged aortic override, enhanced mitral-aortic septation, and a steep atrioventricular septal angle.
A fibromuscular ridge forms due to these stimuli, which causes aberrant proliferation of muscles and endothelium and raises fluid shear stress on the interventricular septum. This might be the reason why subvalvular aortic stenosis developed. Repairing related congenital cardiac abnormalities may alter the left-sided outflow, raising fluid shear stress and turbulence on the interventricular septum, which can lead to the development of subvalvular aortic.
What Pathophysiology Associated With Subaortic Stenosis?
Intraventricular left ventricular hypertrophy, often accompanied by a septal bulge, develops when there is a clinically substantial blockage to the blood flow that exits the left ventricle due to subvalvular aortic stenosis. Further blockage and hyperdynamic function follow from this. Systolic and cardiac output are adequately maintained in isolated subvalvular aortic stenosis until a significant blockage manifests. Undervalvular aortic stenosis progresses slowly in adults, but it can proceed at a variable and unexpected rate in youngsters.
Aortic Regurgitation
If subvalvular aortic stenosis persists, the aortic valve deformity may eventually emerge. Aortic valve trauma is caused by the high-velocity blood jet passing through the stenosis, and the thickening and asymmetrical post-stenotic dilatation of the ascending aorta are partially caused by the fibroblastic tissue of the membrane potentially encroaching on the aortic valve. Aortic regurgitation, which grows worse over time and continues even after surgery to relieve the subvalvular aortic stenosis, affects 65 percent of participants. Since the left ventricular outflow tract pressure gradient increases, the normally mild condition of aortic regurgitation may become more severe. Already pressure-overloaded, the left ventricle experiences volume overloading due to aortic regurgitation, which raises the left ventricular oxygen demand.
Moreover, the coronary perfusion is decreased by the drop in aortic diastolic pressure. The myocardium of the left ventricle is vulnerable to ischemia damage due to the reduction in coronary perfusion and rise in left ventricular oxygen demand. While treating subvalvular aortic stenosis, some individuals may require aortic valve replacement or repair.
What Clinical Signs Are Associated With Subaortic Stenosis?
There are no symptoms seen with moderate sub-aortic stenosis. Subaortic stenosis can cause symptoms like
Moderate and severe occurrences occur more frequently.
What Risk Factors Are Associated With Subaortic Stenosis?
As a congenital cardiac condition, subaortic stenosis has no identified risk factors. However, if the illness is left untreated or if therapies are ineffective, physical stress, such as exercise and pregnancy, can lead to the development of symptoms.
How To Diagnose Subaortic Stenosis?
The following are the diagnostic criteria for diagnosing subaortic stenosis:
1. ECG:
Fifty to eighty percent of individuals have an ECG that shows variable degrees of left ventricular hypertrophy. A noticeable Q wave in the left precordial leads may indicate septal hypertrophy. The ECG results may appear normal in individuals with severe subvalvular aortic stenosis.
2. Radiograph of The Chest
The radiograph of the chest is frequently normal. Certain people have modest cardiomegaly or LV prominence, including those with slight stenosis.
3. Catheterization of The Heart
Aortic stenosis separated from the heart does not usually require cardiac catheterization. It is commonly carried out to interpret the amount of subaortic blockage further if various layers of obstruction are detected. Hemodynamic and anatomical data, such as the gradient across the valve, the degree of aortic regurgitation, and the assessment of cardiac output, are obtained during catheterization. It is possible to see related lesions, such as aortic coarctation. Although it can be used as part of a preoperative workup to rule out severe coronary artery disease, it is not advised in the diagnosis of subvalvular aortic stenosis.
What Are the Treatment Modalities That Are Used In Treating Subvalvular Aortic Stenosis?
When it comes to treating subvalvular aortic stenosis in children, medical therapy is ineffective because the majority of these individuals are asymptomatic. Intervention is eventually required to alleviate the left ventricular outflow tract blockage since it is progressing. Surgical repair of the blockage is the only effective treatment for subvalvular aortic stenosis. This can include myectomy, only a small-scale membrane removal, or a large-scale ring resection. On the other hand, the patient is put on medication until the operation can be done if they experience heart failure or clinically substantial left ventricular dysfunction.
Conclusion
About 1 percent of newborns with congenital heart abnormalities have subaortic stenosis, also known as subvalvular aortic stenosis. Blood with a high oxygen content finds it difficult to get to the rest of the body when subaortic stenosis is present because the heart's left ventricle, which pumps blood out of the body, is clogged.
The second most frequent kind of aortic stenosis is called subaortic stenosis, and it affects men more often than women. Most individuals also suffer from other cardiac defects. When subaortic stenosis worsens over time, it may cause significant symptoms that significantly disrupt the lives of adults who had the condition as children. While some patients may just require years of careful observation, the majority of patients will eventually require surgery of some kind.
