The human heart is an incredible organ that continuously pumps blood throughout the body to deliver oxygen and nutrients to where they are needed. Heart valves play a vital role in regulating the directional flow of blood through the heart. When heart valves become damaged or diseased, they can no longer function properly and new options must be considered. One such option is the implantation of a prosthetic or artificial heart valve as a replacement for the damaged native valve.
What are Heart Valves?
The heart contains four valves that ensure blood flows in the correct direction during each heartbeat. The two atrioventricular valves, the mitral and triscupid valves, are located between the upper and lower chambers. They prevent backflow of blood from the ventricles into the atria during ventricular contraction. The two semilunar valves, the aortic and pulmonary valves, are located at the exits of the left and right ventricles and prevent backflow into the ventricles during relaxation and filling.
When a heart valve becomes damaged or diseased, it no longer opens and closes properly. This can cause blood to flow backward or a blockage in flow. The two most common causes of heart valve disease are rheumatic fever which damages the leaflets and makes them thickened and calcified, and degenerative valve disease where the valve leaflets become stiff with age. Left untreated, heart valve disease can lead to heart failure or other serious complications.
Types of Prosthetic Heart Valves
When a damaged heart valve requires replacement surgery, doctors have the option of implanting an artificial or prosthetic heart valve made from either mechanical or biological materials:
Mechanical Heart Valves: Made entirely from non-biological materials like carbon and synthetic polymers. They provide long-term durability but patients require lifetime blood thinners due to the increased risk of blood clots forming on the valve surface.
Tissue/Bioprosthetic Heart Valves: Made from either harvested animal tissue (porcine or bovine pericardium) or human donor tissue. They do not require long-term anticoagulation but have less durability than mechanical valves with 10-15 years being the average lifespan.
Homograft Valves: Valves harvested from human donors. Rarely implanted due to limited availability but avoid long-term anticoagulation.
The best prosthetic valve option depends on the patient's age, lifestyle needs, other health issues, and risk for blood clots or bleeding complications. The cardiothoracic surgeon performs a comprehensive assessment to recommend the valve type with the best outcomes.
Heart Valve Replacement Surgery
Replacing a heart valve is a serious open-heart surgery that carries some risk but generally has excellent long-term results. Some key aspects of the surgery include:
- Access is gained through a median sternotomy incision to open the chest cavity and stop the heart.
- The damaged native valve is completely excised, usually along with any calcium buildup.
- Careful measurements are made of the Heart Valve's 3-D annular diameter and the appropriate size prosthetic is chosen for secure implantation.
- The new valve is sewn in place with a continuous suture along the annulus using watchmaker precision.
- The heart is closed up and the chest reconstructed with wires or stainless steel sutures.
- Patients are placed on cardiopulmonary bypass for circulatory support during the surgery.
- Recovery in the ICU for several days before transition to a step-down unit and eventual discharge.
Post-procedure, patients receive anticoagulant drugs as prescribed by their cardiac team. For modern tissue valves, follow-up visits monitor overall health and any structural valve deterioration. With close medical care, prosthetic valves provide most patients a new lease on life.
Advances in Prosthetic Heart Valve Technology
Medical device companies continue innovating new valve designs with the goals of decreasing risk of complications and extending durability. Some notable advances include:
- Pericardial tissue valves treated with anti-calcification agents to slow mineralization and increase lifespan.
- Rapid-deployment valves collapsed into delivery systems for transcatheter implantation through small incisions instead of open-heart surgery.
- Valves sized and shaped using 3D printing and computer modeling for precision anatomical fit.
- Polymer skirt extensions added to mechanical discs that reduce turbulent blood flow pressures against valve surfaces.
- Transcatheter aortic valves implanted through catheters to treat high-risk seniors for aortic stenosis with non-surgical TAVR procedures.
As research progresses, future valve technologies may utilize patient-specific modeling, self-adapting materials, tissue regeneration, and even fully-artificial organs. By advancing both surgical options and long-term durability, more individuals worldwide can gain years of productive living from heart valve replacement therapies.
In summary, prosthetic heart valve implantation through replacement surgery has emerged as a reliable treatment when native heart valves become dysfunctional. With continued innovations, these life-saving artificial valves are allowing more people to live actively well into their senior years. Close collaboration between engineers, physicians and patients will hopefully develop even improved valves of the future.
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