Just what is a Mechanical Heart Valve?
Your heart has four chambers that ensure blood is continually pumped to your lungs to be oxygenated and then sent around your body. Each chamber contains a valve that lets blood flow forwards and prevents it from flowing back into the previous chamber. These valves are essential for ensuring a steady supply of blood to your entire body.
Heart valves can become damaged in one of two ways. The first type is a leaky valve and occurs when the valve fails to close fully and blood leaks back into the previous chamber of the heart. The second is called valve stenosis, or narrowing, and it describes a valve that fails to open completely and blocks the flow of blood. It is common practice to replace the failing valves in both conditions. This could either be with a biological replacement, which has been taken from an animal or human donor, or with a mechanical heart valve.
So what is a Mechanical Heart Valve?
Mechanical heart valves are artificial devices manufactured to replace damaged natural valves that no longer function correctly. With a high success rate and no need for replacement in the lifetime of the user, mechanical valves have only one main drawback - they increase the risk of blood clots forming in the heart. This means that patients with mechanical heart valves require lifelong use of anticoagulants.
There are three main types of mechanical heart valves:
Caged Ball: The pressure of the blood pooling in one chamber pushes a ball to the edge of its cage, opening the valve so that blood can flow into the second chamber. The building pressure in chamber two then rolls the ball backwards, forming a seal and allowing the first chamber to fill back up again. This ‘see-sawing’ movement of the ball in its cage was the first design to provide long-term success. However, it was associated with a high risk of clotting and has since been replaced with more modern and effective.
Bileaflet: The bileaflet valve is made up of two half-circular flaps (leaflets), mounted in a circular frame. These allow blood to flow unilaterally through the heart and prevent it from moving backwards. Well tolerated by the body, this design provides the most natural blood flow through the heart and requires only low doses of anticoagulants to prevent blood clotting.
Tilting Disc: This design was invented shortly after the caged ball valve and has been refined and developed over the last fifty years. A disc suspended from a metal ring by two metal supports, the tilting disc design works like a window. It swings open when the heart contracts to allow blood to flow through and pivots closed again when it relaxes, preventing the blood from flowing backwards.
How is a Mechanical Heart Valve fitted?
Mechanical heart valves are fitted in open heart surgery, a complex procedure that requires the surgeon to access the heart directly through the rib cage. The patient is placed on bypass for the duration of the surgery with a machine doing the work of the heart and lungs, oxygenating the blood and pumping it around the body. This enables the surgeon to operate directly on the heart and replace the valves without interrupting the body’s blood supply.
Living with a Mechanical Heart Valve
Patients who have had a mechanical heart valve replacement are capable of leading normal, active lives with very few concessions. The main factor is the necessity for the patient to take an anticoagulant, such as Warfarin, for the rest of their life to reduce the risk of heart attack or stroke. This is because there is a risk of blood clots developing on the surface of the valve. These clots could reduce the flow of blood to the heart causing a heart attack or break away and travel through the body, causing a stroke.
Further Reading:
https://www.cardiosmart.org/Heart-Basics/How-the-Heart-Works
Options for heart valve replacement
http://www.poconorecord.com/article/20150429/ENTERTAINMENTLIFE/150429265/101116/LIFESTYLE
Study Compares Tissue-Based or Mechanical Replacement Heart Valves
http://consumer.healthday.com/general-health-information-16/misc-surgery-news-650/study-compares-tissue-based-or-mechanical-replacement-heart-valves-692147.html?lexp=true&utm_expid=38353063-4.pIV1hUrQR8K_MJ1_OqjLag.1
NIH funds WPI heart valve study
http://www.wbjournal.com/article/20150423/NEWS01/150429968/nih-funds-wpi-heart-valve-study
https://www.bhf.org.uk/heart-health/treatments/valve-heart-surgery