Prosthetic Heart Valves - Types, Mechanisms, Indications, and Risks

Introduction

The heart comprises four chambers- two upper sections, the right and left atrium, and two lower divisions, the right and left ventricles. Parallel to four chambers, the heart has four valves: mitral, tricuspid, aortic, and pulmonary. Valves are a crucial part of the heart’s structure. They open and close as the blood passes through them. They mainly regulate the entry and exit of blood into the heart’s various chambers. The valves have flaps or leaflets that open and close. Valves with three leaflets open and close simultaneously. The leaflets are compact to avoid any backflow of blood, and visa verse is why they open. The mitral or bicuspid valve allows blood to flow smoothly from the left ventricle into the left. It has two leaflets. The tricuspid valve allows blood to flow easily from the right atrium into the right ventricle. It has three leaflets. The aortic valve controls smooth blood flow from the left ventricle to the aorta. Finally, the pulmonary valve primarily allows smooth blood flow from the right ventricle into the pulmonary artery. It has three leaflets.

How Do Heart Valves Work?

The four valves have the primary function of opening and closing according to the heart’s blood flow. Therefore, when working without interruptions, the four heart valves ensure no backflow of blood. Mentioned below is the pace at which the blood flows.

• Open tricuspid and mitral valves allow the blood to flow from the atrium on the right side into the ventricle of the same side and from the left atrium into the left ventricle.

• A closed tricuspid is when the right ventricle is whole. It closes to keep the blood from flowing backward into the right atrium when the ventricle contracts.

• The mitral valve closes when the ventricle is up to its total capacity. This keeps blood flowing backward into the left atrium when the ventricle contracts.

• The pulmonary valve then opens as the right ventricle begins to contract. Blood is then flown out of the right ventricle through this heart valve inside the pulmonary artery and eventually into the lungs.

• Next, the left ventricle begins to contract, and the aortic valve opens up. Blood is pumped out of the left ventricle through this valve into the aorta.

• The aorta branches into several arteries and thus provides blood to the body. Aorta is known to be the largest blood vessel of the heart as well as the entire body. It is highly flexible and has three leaflets.

• Closed pulmonic is when the right ventricle finishes contracting and starts to relax, preventing blood from backflow inside the right ventricle.

• When the left ventricle finishes contracting and begins to relax, the aortic valve is shut, thus avoiding any leakage or backflow of blood into the ventricle.

• This pattern repeatedly occurs, causing blood to flow continuously to the vital organs, primarily the heart, lungs, and rest of the body.

What Are the Signs and Symptoms That Suggest a Prosthetic Heart Valve?

Prosthetic heart valve implantation is a surgical and invasive procedure aiming to correct and treat defective heart valves to regain the heart's standard function. Mentioned below are a few signs and symptoms that may help the healthcare provider decide on going forward with a prosthetic heart valve surgery after careful diagnosis and physical examination.

• Dizziness.

• Chest pain.

• Difficulty in breathing.

• Cyanosis or bluish discoloration of the skin.

• Discomfort around the waist.

• Swelling of the ankles and abdomen.

• Increased water retention.

• Rapid gain in weight.

• Lethargy.

What Are the Kinds of Prosthetic Heart Valves?

The broad classification of prosthetic heart valves includes- mechanical heart valves, bioprosthetic heart valves, and homograft heart valves.

• Mechanical heart valves have been made available in three varieties- bileaflet, monoleaflet, and caged ball valves. They are composed of an occluder, an occluder restraint, and a sewing ring. During diastole and systole of the mitral valve, the occluder situates itself into the sewing ring, creating a seal in order to prevent the backflow of blood. Unfortunately, subpar hemodynamics is one of the significant drawbacks of mechanical valves.

• Bioprosthetic valves include three xenograft tissue leaflets. These leaflets are available in the form of porcine or bovine pericardial tissues. The xenografts are treated with a glutaraldehyde solution in order to decrease the risk of thromboembolic changes since glutaraldehyde is known to inhibit the denaturation of collagen. Bioprosthetic valves can be stented or non-stented. When stented, the leaflets of the valve are sewn to a dacron-covered metallic support structure, and when it is not stented, the leaflets are attached directly to the aortic annulus. Hemodynamically, these valves are better than the mechanical ones. However, their tiny annulus creates a huge pressure gradient, which marks its drawback.

• Homograft valves are developed and created from human cadavers with no regenerative capacities. Susceptibility to cyclic stress is their drawback. A homograft valve is used with an autograft valve- a heart valve from an anatomic position that is transplanted to another position.

What Are the Other Treatment Options for Defective Heart Valves?

Prosthetic heart valves are an excellent option for correcting defective heart valves. On the other hand, factors such as the patient's age, cardiovascular health, underlying diseases, immune system, family history, etc., may not make the patient suitable to undergo a prosthetic heart valve treatment. Therefore, the healthcare provider is the best person to decide which of the below-mentioned treatment modalities is the perfect alternative for the patient.

• Vasodilator therapy.

• Diuretics or water pills.

• Beta-blockers.

• Endocarditis prophylaxis.

• Anticoagulation.

• Open heart surgery.

• Mechanical valve insertion.

• Bioprosthetic valve repair.

• Mitral clip.

• Balloon valvuloplasty.

• Transcatheter aortic valve replacement or TAVR.

• Transcatheter Mitral Valve Replacement or TMVR.

• Cardiac rehabilitation.

What Are the Risks of Prosthetic Heart Valve Surgery?

Risks are a part of any procedure, invasive or noninvasive. Risks and complications can be easily kept at bay by performing the treatment with great finesse and expertise, as well as a thorough knowledge of the patient’s medical, family, and drug history. Mentioned below are a few of the risks of prosthetic heart valve surgery.

• Excessive bleeding during the surgery or even after the surgery.

• Blood clots.

• Heart attack.

• Stroke.

• Lung disorders.

• Infection of the blood.

• Pneumonia.

• Pancreatic disorders.

• Breathing difficulty.

• The abnormal rhythm of the heart.

• Incorrect replacement of the heart valve.

Conclusion

Valves of the heart cannot be replaced or compromised. Defective heart valves need to be corrected and cured urgently. Prosthetic heart valves have proven to be successful in several suitable candidates. Patients who have undergone prosthetic heart valve surgeries live a positive outlook.