The structure of the human heart is complex, with various biological components in it. In some people, either due to genetic reasons or age-related disorders, some of these components develop abnormalities which are classified as structural heart diseases. While surgery was the only option to treat these ailments in the past, in recent years, several minimally invasive techniques have emerged to treat structural heart diseases. Transcatheter Mitral Valve Replacement (TMVR) is one of them.
What Is TMVR?
The mitral valve in the heart regulates blood flow to the left side of the heart. Over time, the mitral valve can develop several abnormalities, the most common among them being the following:
- Mitral stenosis: When the mitral valve fails to open as wide as it should.
- Mitral regurgitation or leaky mitral valve: This is leakage of blood backwards through the mitral valve every time the left ventricle contracts.
Previously, till more than a decade ago, surgery was done or even transcatheter (a minimally invasive procedure) techniques were used to repair these conditions. But in recent years, the success of Transcatheter Aortic Valve Replacement (TAVR) has inspired experiments in Transcatheter Mitral Valve Replacement.
In this procedure, as the name implies, a catheter tube is used to push a synthetic valve through a vein in the body into the heart in position of the faulty, native mitral valve. In the trans-septal process, the catheter is inserted through the femoral vein in the leg or groin. In the trans-apical process, a hole is made in the chest wall to insert the catheter.
When and How Is It Performed?
The emergence of TMVR was necessitated by the fact that some patients with mitral valve abnormalities are not suitable for surgery. This could be because the stenosis is caused by calcification (hardening) of the leaflets of the valve or other reasons. TMVR is also used when surgical techniques like rings and bioprosthesis have failed.
The synthetic valve used for replacement is biologically safe for the human body and approved by the FDA (Food & Drug administration) in the US. Popular makes include Fortis, Tendyne, NaviGate, Intrepid, CardiAQ and Tiara.
Once the procedure is done, the patient is closely monitored for anti-coagulation (reducing the risk of formation of blood clots) as well as any other complications that may arise.
Pros and Cons of TMVR
A significant advantage of TMVR is that the procedure is minimally invasive and doesn’t require a surgical incision. However, TMVR comes with its own set of challenges. Most challenges revolve around the structure of the mitral valve itself. The mitral valve is large in size, quite hard to access, asymmetrical in shape and lacks a clearly well-defined annulus (the base on which the 2 leaflets are supported). This makes anchoring of the replacement valve a challenge. Also, the geometry of the valve changes throughout the cardiac cycle, and further, placing the replacement valve comes with the risk of outflow tract obstruction in the left ventricle. The mortality rate of patients that have undergone TMVR, after 30 days, is high as of date.
However, with time, these challenges too will be overcome with better designs of the replacement valve and better replacement techniques. There is a lot of research and experimentation happening all around the world in this area.
TMVR is a new frontier in cardiology and brings hope to patients with structural heart disease as well as to those who are poor candidates for surgical interventions. Sophisticated 3D imaging techniques are being used for modeling the valve and selecting candidates for valve replacement. These measures could increase the success rate of TMVR and could pave the way for its increased adoption.