Page 34 - Medicine and Surgery

P1: JYS
BLUK007-02 BLUK007-Kendall May 25, 2005 17:25 Char Count= 0

30 Chapter 2: Cardiovascular system

cardiopulmonary bypass to reduce heart movement and Open valvotomy and valve repair is performed under
avoid additional ischaemia and internal defibrillating cardiopulmonary bypass. The valve leaflets are sepa-
paddles are used to restore sinus rhythm. rated under direct vision. This is used for patients with
coexisting mitral regurgitation.
Valvular regurgitation when due to dilation of the valve
Complications
ring may be treated by sewing a rigid or semi-rigid
Aspirin is usually continued for the procedure, but other
ring around the valve annulus to maintain size (annulo-
antiplatelet drugs such as clopidogrel are stopped up to
plasty). If regurgitation is due to areas of flail leaflets, e.g.
5daysinadvance. During the procedure patients are
due to infective endocarditis or chordal rupture, part of
heparinised to prevent thrombosis. Antibiotic cover is
the leaflet may be resected or even repaired with a piece
provided using a broad spectrum antibiotic to prevent
of pericardium to restore valve competence.
bacteraemia. Operative mortality depends on many fac-
Valve replacement: Using cardiopulmonary bypass the
tors including age and concomitant disease, it usually
diseased valve is excised and a replacement is sutured
varies from 1 to 5%. There is a similar, age-related risk
into place. Valves may be divided into mechanical and
of stroke.
biological types:
Early mechanical valves were ball and cage type such

Prognosis
as the Starr–Edwards valve. Current designs all have
Approximately 90% of patients have no angina postop-
some form of tilting disc such as the single disc Bj¨ ork–
eratively, with almost all patients experiencing a signifi-
Shiley valve or the double disc St Jude valve. They are
cant improvement. Over time symptoms may gradually
durable, but require lifelong anticoagulation therapy
return due to progression of atheroma in the arteries or
to prevent thrombosis of the valve and risk of em-
occlusion of vein grafts. Less than half are symptom-free
bolism.
at 10 years. Outcome is improved by risk factor modifi- Biological valves may be xenografts (from animals)
cation(stoppingsmoking,loweringhighbloodpressure, or homografts (cadaveric). Xenografts are made from
treating hyperlipidaemia and diabetes effectively, etc).
porcinevalvesorfrompericardiummountedonasup-
Angioplasty or re-do coronary artery surgery may be
portive frame. They are treated with glutaraldehyde to
possible if medication is insufficient to control symp-
prevent rejection and are used to replace aortic or mi-
toms; however, repeat surgery has a higher mortality.
tral valves. They do not require anticoagulation unless
Angioplastyusingstentimplantationissuitableforgrafts
the patient is in atrial fibrillation but have a durabil-
or native vessels.
ity of approximately 10 years. Valve failure may result
from leaflet shrinkage or weakening of the valve com-
petence causing regurgitation, or calcification causing
Valve surgery
valve stenosis.
Valvesurgery is used to treat stenosed or regurgitant Valve replacements are prone to infective endocarditis,
valves, which cause compromise of cardiac function. which is difficult to treat (and may require removal of a
Conservative surgery is performed whenever possible. mechanical valve).
The aortic valve is not usually amenable to conservative Valve replacement provides marked symptomatic re-
surgery and usually requires replacement if significantly lief and improvement in survival. Operative mortality
diseased. A stenosed mitral valve may be treated by fol- is approximately 2%, but this is increased in patients
lowing procedures: with ischaemic heart disease (when it is usually com-
Percutaneous mitral balloon valvuloplasty in which a bined with coronary artery bypass grafting), lung dis-

balloon is used to separate the mitral valve leaflets. ease and the elderly. Perioperative complications include
This is now the preferred technique unless there is haemorrhage and infection. Late complications include
coexisting mitral regurgitation. haemolysis and valve failure. Arrhythmias also occur. All
Closed valvotomy uses a dilator that is passed through
prosthetic valves require antibiotic prophylaxis against
aleft sub-mammary incision into the left atrial ap- infectiveendocarditisduringnon-sterileprocedures,e.g.
pendage. dental treatment, lower gastrointestinal or urogenital