COMPARATIVE EFFECTIVENESS OF MECHANICAL AND BIOPROSTHETIC HEART VALVE REPLACEMENT

Mahammadjonov Saidjahon Shokirjon ogli

Mirzamansurova Robiya Ahmadjon qiz

iKokand University, Andijan BranchFaculty of General MedicineAbstractHeart valves are essential anatomical structures that ensure unidirectional blood flow within the heart. In cases of valve insufficiency or stenosis, replacement surgery becomes a crucial intervention in modern cardiac surgery. Two primary types of prosthetic valves are used today: mechanical valves and bioprosthetic valves. Both types have distinct advantages and disadvantages, and the choice depends on factors such as patient age, health status, risk of thrombosis, and quality-of-life considerations.

Introduction to Heart Valves

Heart valves are vital anatomical and physiological structures responsible for maintaining the unidirectional flow of blood. Located between the chambers of the heart, they prevent backflow and ensure smooth circulatory function.

Main functions of heart valves:Maintaining one-way blood flowPreventing regurgitationSupporting efficient and coordinated heart functionCommon heart valve disorders:1. Stenosis — narrowing of the valve opening (e.g., aortic stenosis)2. Regurgitation — incomplete closure leading to backwar blood flow (e.g., mitral regurgitation)These conditions may lead to cardiac overload, impaired hemodynamics, and heart failure, often requiring valve replacement surgery.Indications for Valve ReplacementMitral stenosisAortic regurgitationSevere valve prolapseCongenital valve defectsInfective endocarditis with structural destructionBioprosthetic Heart ValvesBioprosthetic valves are typically manufactured from animal-derived tissues (e.g., bovine pericardium) and are widely used in cardiovascular surgery. They are associated with lower thrombotic risk compared to mechanical valves and therefore require minimal anticoagulation therapy.

Advantages:

Lower risk of thromboembolismReduced need for long-term anticoagulationImproved physiological compatibilityBetter quality of life in many patientsDisadvantages:Limited durability (typically 10–20 years)Higher risk of degeneration in younger patientsPossible need for reoperationEffectiveness of Bioprosthetic Valves

Clinical Effectiveness

Provide adequate hemodynamics and restore normal blood flow

Reduce symptoms such as dyspnea and fatigue

Improve long-term quality of life

Statistical Data:Average durability: 10–20 years

Reoperation risk increases afte 10 years, especially in younger patients

Physiology of the Human Heart

Heart activity is based on rhythmic myocardial contractions. Systole refers to contraction, whereas diastole refers to relaxation. Cardiac impulses originate from the sinoatrial node (60–80 impulses per minute), then spread through the atria, AV node, bundle of His, and Purkinje fibers, leading to coordinated contraction of ventricles.

The cardiac cycle includes: Atrial systoleVentricular systole Diastole (joint relaxation phase)During atrial contraction, blood moves into the ventricles; during ventricular systole, semilunar valves open to eject blood into the aorta and pulmonary artery.

Comparison Between Mechanical and Bioprosthetic Valves

Research Findings: Studies show that mechanical valves have a lower reoperation rate, but require lifelong anticoagulation therapy, increasing the risk of bleeding.Meta-analysis indicates that in patients aged 50–70 years, survival is higher with mechanical valves.In patients above 70 years, bioprosthetic valves are preferred due to reduced anticoagulation requirements and lower bleeding risk.Postoperative outcomes (stroke, bleeding, infection) show no significant difference between the two groups immediately after surgery.Reoperation is significantly more common in the bioprosthetic group due to structural valve deterioration.

Summary of Key Differences: Feature Mechanical Valves Bioprosthetic Valves Durability Very long (20–30+ years) Moderate (10–20 years) Anticoagulation Lifelong Short-term or none Thrombosis Risk Higher Lower Reoperation Risk Low HigherBest for Younger patients Older (>70 years) or anticoagulation-intolerant patients

Conclusion Heart valves are crucial structures maintaining unidirectional blood flow and supporting efficient cardiac function. Disorders such as stenosis and regurgitation can severely impair heart performance, necessitating valve replacement surgery.Both mechanical and bioprosthetic valves play an essential role in modern cardiac surgery.Mechanical valves provide long-term durability but require lifelong anticoagulation.Bioprosthetic valves offer better physiological compatibility and lower thrombotic risk but have a limited lifespan.Current research supports the use of bioprosthetic valves in elderly patients, while mechanical valves remain preferable for younger individuals requiring long-term durability.Valve replacement significantly improves cardiac function, reduces symptoms of heart failure, and enhances overall quality of life, making it one of the most important and progressive fields in cardiovascular surgery.

References

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