SURGICAL MANAGEMENT OF ACQUIRED HEART VALVE DISEASE

SURGICAL MANAGEMENT OF ACQUIREDHEART VALVE DISEASE

The choices in surgical management of heart valve diseasehave recently become more complex, with closed valvotomy,open valvotomy and balloon valvuloplasty all being possible approaches.

Cardiac bypass

In the technique of cardiac bypass the circulation isarrested and there is extracorporeal circulation from aroller pump and external oxygenator. The brain is perfusedat relatively low pressure, and the oxygenator and perfusionsystem introduce microemboli into the arterial circulation.There is therefore a morbidity associated withprolonged cardiac bypass. Most of the morbidity seems tobe reversible (e.g. intellectual impairment) but patientswith cerebrovascular disease, such as carotid stenosis, areat particularly high risk from cerebral infarction.

Balloon valvuloplasty

In balloon valvuloplasty a balloon catheter is insertedthrough the valve orifice and then dilated to split open thevalve. The aortic valve can be dilated in children, andballoon valvuloplasty has been especially successful forpulmonary and mitral stenosis. If torrential regurgitationis produced during mitral valvuloplasty, valve replacementis essential.

Valve repair and replacement

Plastic surgical repair to a damaged valve uses pericardialor other tissue to repair defects in the valve cusps, or suturingof the valve ring to a prosthetic former to correct agrossly dilated valve ring. The latter is commonly performedin severe tricuspid regurgitation. The proceduresare time-consuming and technically demanding and havehad a history of variable results.

Prosthetic and biological valves

The type of valve used for replacement depends very oftenon local preference and expertise. Mechanical valves require permanent oral anticoagulation with warfarin. Biological valves do not, but are prone to early failure and calcification.The original prosthetic Starr-Edwards valve -essentially a ball in a cage - was built for durability, butearly models formed thrombus on the struts and were alsorather noisy.

Numerous attempts have been made toimprove on this, but many have developed mechanical problems and the Starr valve remains the most durable prosthesis currently available.In order to avoid the anticoagulation essential withmechanical valves, various attempts have been made to usebiological ones.

Fresh human homografts have been usedvery successfully in the aorta, but availability has been aproblem. The most widely used biological valves arexenografts. Porcine or bovine tissue is usually mounted ona ring or stent; such valves have the advantage of notrequiring long-term anticoagulation, nor do they producethe loud prosthetic clicks of mechanical valves.

Their disadvantages are that they have an unpredictable lifespanand can calcify and become stenosed very rapidly in youngpatients. However, most of them last at least 5 years.They may be considered in women of childbearing age whowish to have a family without the teratogenic risks of anticoagulation.Such patients must be prepared to face thesubsequent reoperation for valve replacement when thebiological valve fails.Under current UK legislation a heavy-goods or publicservicevehicle licence holder cannot drive if he or sheis on anticoagulants, and so these patients may have toopt for biological valves if they wish to maintain their occupation.

SURGICAL MANAGEMENT OF ACQUIRED HEART VALVE DISEASE

By: Dr Izharul Hasan

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