30 March, 2024

Aortic Stenosis: What It Means

Introduction
Aortic Stenosis (AS) refers to a clinical scenario where the Aortic Valve (AoV) doesn’t open well, causing an impediment to blood flow from the heart to the rest of the body. This leads to the heart working against resistance which adds undue stress to the heart. If this scenario is left unchecked for a long time, the heart eventually fails leading to complications that often culminate in the patient’s demise. An animated depiction of AoV, AS and treatment options is laid out in this video (courtesy: Alliance for Aging Research)

The Aortic Valve
The aortic valve (AoV) is one of the four valves of a normal heart. It sits between the Left Ventricle (LV, the heart’s main pumping chamber) and the Aorta (the main channel that carries blood from the heart to the rest of the body). The role of AoV is to allow unidirectional blood flow from LV to Aorta offering minimal or no resistance while preventing any blood leak back into LV from Aorta. Native AoV has ‘cusps’ made up of extremely soft thin tissue. The cusps open and close with every heart contraction without any significant fatigue. Three symmetric cusps arranged in the shape of the ‘Mercedes Benz’ logo constitute a normal health AoV.

Why does Aortic Stenosis occur?
Few of us are born with aortic valve cusps which are not perfectly symmetric, which causes flow turbulence across the valve. This leads to repetitive micro injury and healing of aortic cusps that over a long time (years) adds scar tissue and calcium deposits causing structural deformity. These degenerated/deformed cusps lead to restricted openings as well as imperfect seals during closure (Figure 2A, 2B). If the cusps’ opening is restricted significantly, blood flow gets severely restricted, leading to the clinical condition termed “Aortic Stenosis” (AS). Stenosis refers to restricted valve opening. AS is typically graded as mild, moderate, and severe. While mild and moderate AS can be observed with medicines alone, patients with severe AS may need to undergo corrective measures.

Risk factors for Aortic Stenosis:
It is hypothesized that factors which put us at risk for AS are similar to those for Coronary Artery Disease as well, namely diabetes, high cholesterol, smoking, etc. Still, the most important risk factor is ageing. A healthy lifestyle and good control of risk factors can affect the onset and progression of AS. On the other hand, few people are born with not three, but 2 or 1 Aortic Valve cusps. Such conditions are called bicuspid or unicuspid valves, and they are at higher risk for developing AS early in life.

Symptoms of severe Aortic Stenosis:
Breathing difficulty
Exercise intolerance, getting tired easily
Chest discomfort
Dizziness, giddiness, or fainting
Leg swelling
Difficulty breathing when lying down

Treatment options for severe Aortic Stenosis:
AS is a mechanical problem that must be dealt with through mechanical intervention. Once a patient is diagnosed with severe AS and has symptoms associated with it: these are the available options:

Medicines alone: In severe AS cases, medicines can somewhat alleviate the symptoms but don’t modify the disease or prolong longevity. Overall, it is a fallback option when standard treatment options seem undesirable.
Surgery: Surgery is the mainstay of therapy. Open heart surgery involves cutting open the chest, putting the patient on a heart-lung bypass machine, removing the degenerated aortic valve and replacing it with a man-made valve (mechanical or bio-prosthetic) that is immediately functional after implantation. Surgical Aortic Valve Replacement (SAVR) is a well-established technique for all patients with severe Aortic Stenosis. In routine low-risk cases, surgery-related major complications are uncommon.
Minimally Invasive: Transcatheter Aortic Valve Replacement (TAVR) is a newer technique in which a specialized bioprosthetic Valve is squeezed and loaded onto a delivery system (Flexible tube called catheter). This catheter is now inserted inside the body via a small groin/leg incision similar to coronary angioplasty. Once in the body, the compressed valve is released at the site of the diseased native aortic valve. All this is achieved via a small incision in the groin area that is not visible after a few days. TAVR offers a less risky minimally invasive procedure with early recovery. TAVR has undergone rigorous clinical studies in the past 10 years, and the results have been extraordinarily positive. TAVR is the standard therapy in the Western world for patients with severe AS who are considered intermediate or high risk for open heart surgery or are above 65 years of age.
Balloon Valvuloplasty: This procedure involves inflating a balloon at the aortic stenosis site, leading to the valve’s crack opening. This procedure is reserved as an urgent bailout option for those who can not undergo SAVR or TAVR at that point in time. The procedure is simple, relatively safe, and offers temporary relief to patients too sick to undergo SAVR or TAVR. The major limitation of Balloon Valvuloplasty is that the positive benefits of intervention are temporary. Typically, stenosis recurs severely in about 3-6 months.

The Heart Team:
The landscape of AS treatment has seen a major overhaul in the past decade. TAVR is the most disruptive medical technology in recent times, and the entire world is talking about it. A multi-modality approach to individual patient cases has been shown to improve overall outcomes and due to this, the concept of “The Heart Team” has evolved lately. The Heart Team involves a group of clinical and non-clinical staff coming together to discuss each patient case, using a multi-disciplinary approach to handle the problem, and coming to a combined decision agreed upon by all the parties. It also provides holistic patient care that targets every aspect of patient well-being rather than limiting it to one particular problem. As someone seeks to care for severe AS, it is reasonable to approach a healthcare institute with an established Heart Team.

I am sure I didn’t answer all your questions on this topic. Feel free to message me with your queries; I will happily answer them.

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