Cardiac SurgeryCardiac Surgery
Cardiac surgeons in general do not investigate their patients, this task is the responsibility of the referring Cardiologist. It is however the responsibility of the surgeon to ensure that if possible, all relevant investigations are performed and available to him before he embarks upon surgery. Because of this, referrals of patients with cardiac problems, which may require surgical treatment, should be referred to the Department of Cardiology, Inkhosi Albert Luthuli Central Hospital under the Headship of Prof. D P Naidoo
In general assessment of a patient for possible surgery is a complex process which includes assessment of physical, mental and social aspects of a patients status.
Congenital Heart Disease
The incidence of congenital heart disease worldwide is in the order of 0.8% of births. Of these children, some have non-surgical or self-correcting conditions. From the birthrate in KwaZulu-Natal and the eastern portion of the Eastern Cape we roughly estimate that our Department should be operating on 500-850 congenital heart lesions per year if we were to service the whole population. A small amount of this workload is performed within the Private Sector (+/-50/year). The department offers a service in all types of surgically remediable congenital heart disease other than hypoplastic left heart.
Valvular Heart Disease
Valvular heart disease is divided into congenital and acquired. Acquired disease is loosely divided into rheumatic and degenerative. Infective endocarditis may complicate previously abnormal valves and is rare on normal valves except inpatients compromised by intravenous drug abuse.
Surgery for valve disease is performed to improve cardiac function and/or to prevent further cardiac decompensation. When possible an attempt is made to repair valve tissue, accepting that in many patients further valve deterioration may require further surgery at some future time. This is because of the morbidity associated with long term valve replacement, mainly related to problems with anticoagulation and thrombo-embolism. However due to the poor short results reported from most centres with repair of rheumatic valves in the younger patient, our department has limited such repairs to specially selected cases.
The present valve replacements available are biological (porcine aortic or bovine pericardial, homograft) or mechanical, consisting of pyrolytic carbon discs hinged or suspended in a metal or pyrolytic carbon housing. In our practice most of our valve surgery is for rheumatic disease.
Biological valves have the advantage of not requiring anticoagulation in their own right, a big advantage in a rural community. They however have at present a limited life span especially in the younger patient making most of the present generation of biological valves completely unusable in children. Present changes in some of the preservation techniques may help prolong the life of these prostheses in the future.
Homograft valves are useful in the aortic position where they appear to have a longer life than xenografts (non-human biological tissue). However they have proved less successful in the mitral position where aortic homograft valves require a stent and mitral homografts have yet to prove themselves.
Mechanical valves have the advantage that the present generation of valves appears to have a prolonged functional life span, probably in excess of 30 years. They can also be used in young patients. They have the major disadvantage of requiring life long anticoagulation with its risks. They also have the disadvantage of a low (1.5-2%) annual risk of thrombosis especially in the mitral position. Because of this any patient with acute breathlessness following valve replacement must have the valve screened to ensure ongoing normal valve function.
Coronary Artery Disease
Coronary artery surgery is now the most common cardiac operation. Indeed it is the commonest elective surgical procedure performed in the United States with an operative rate of 600 per 1,000,000 per year, a total of around 150,000 procedures annually. The population in KwaZulu-Natal has a much lower overall incidence of ischaemic heart disease than is seen in North America. In certain sectors of the community, however it is very high especially in the Indian community where it is commonly associated with diabetes.
Patients are selected for surgery on a basis of symptoms and prognosis from their coronary disease anatomy. Several large series have looked at the risk of coronary artery disease treated medically and with surgery. Detailed guidelines indicating the risk following either medical or surgical treatment have been evolved. Patients with angina or angina equivalent or who have had an episode of infarction, are carefully assessed by the cardiologist to see which type of treatment will give the patient the best prognosis. These assessments include biochemical assessments looking for lipid and cholesterol abnormalities as well as ECG, stress ECG and echocardiological assessments. If patients have evidence of significant coronary artery disease and are otherwise fit on general physical and mental grounds, they would be further assessed by coronary artery angiography. They would then be assessed as requiring medical treatment, possible candidates for percutaneous transluminal coronary angioplasty or for possible surgery. At this point the surgeon is consulted to assess whether the lesions are also felt by the surgeon to be amenable to surgery.
The techniques used in coronary artery surgery are well worked out. Native arterial and venous conduits are used, internal mammaries, long or short saphenous vein and recently radial arteries are the most frequently used conduits. Post-operatively, recovery is usually quick, most patients being discharged on the 6th day. Patients undergoing emergency surgery for unstable angina, or ongoing ischaemia following infarct may need additional support from the intra-aortic balloon pump but also usually have an early and good recovery. Patients with significant left ventricular dysfunction and patients with poor quality arteries do less well.