Ischaemic Heart Disease

The evidence for IHD comes from two aging but still valid studies carried out first in America and then in Europe, where patients with angina were randomized to either medical treatment or surgical treatment. With passing time, those treated surgically began to show a survival advantage. This was particularly marked in the groups shown in Table 1.1, listed in descending order of greater prognostic importance.

It can be seen from the above that coronary angiography is essential to assess the prognostic implications of IHD, and makes decision-making relatively straightforward. On prognostic grounds alone, a young, otherwise fit, patient with a 90% LMS stenosis should be offered surgery, whereas an old, unfit diabetic arteriopath with single vessel disease affecting only a branch of the circumflex coronary artery should not.

Valve Disease

The symptomatic indication is the same as everywhere else: failure of medical treatment adequately to control the symptoms. The prognostic indication in general depends on the valve lesion, the presence of symptoms and changes in the structure and function of the heart (abnormal shape and increased size of the ventricle, ventricular function and AF are markers of an advanced stage of the valve pathology). In other words, regardless of the severity of the stenosis or regurgitation, there is no prognostic indication if the patient is asymptomatic with normal heart function and dimensions.

Risk Assessment

The mortality of cardiac surgery has for over 40 years been measured and incorporated into decisions about clinical care. Crude mortality, however, is not enough, and even journalists understand that the risk profile of the patient has as much to do with outcome as the quality of surgical care that is given.

Many models of risk in adult cardiac surgery have been developed, but the authors of this chapter are particularly (and understandably) biased toward the European System for Cardiac Operative Risk Evaluation (EuroSCORE). This was originally developed in 1999 and rapidly became the most widely used risk model in cardiac surgery. The EuroSCORE originated from the analysis of data of more than 13,000 consecutive cases performed in more than 100 European centres in 1995. Progress in surgical techniques and postoperative care made the original data set outdated and led to the development of a new model: the EuroSCORE-II. The core of risk factors is almost the same although some definitions are more precise. These variables include patient-related factors (age, gender, lung disease, renal impairment, extracardiac arteriopathy, poor mobility, previous cardiac surgery, active endocarditis, critical preoperative state, DM on insulin), cardiac-related factors (functional class, recent MI, LV function, PHT) and operative-related factors (priority, weight of surgical procedure, surgery on the thoracic aorta). The EuroSCORE calculator is available online.

Setting Up

Most cardiac operations are carried out with a standard set-up, which follows the patient surgical safety checklists. Once key factors associated with reduction of postoperative morbidity and mortality such as timely antibiotic administration, acknowledgement of allergies, blood availability and sterility have been verified, surgery begins.

Median sternotomy is the preferred access for most cardiac operations. Before dividing the sternum, it is useful to deflate the lungs to mitigate the risk of opening the pleural cavities. This minor event can be easily treated by placing a drain in the opened pleura, but in patients with reduced respiratory reserve it can be beneficial to keep the pleural intact. If the procedure includes the coronary surgery (CABG) the next step will be conduit harvesting (usually the left internal mammary artery (LIMA) and long saphenous vein (LSV). The LIMA is a precious conduit in coronary surgery: it is an ideal graft to the LAD coronary artery, which stays patent virtually forever and seems immune to atherosclerosis. If required, a segment of the LSV is harvested simultaneously. Once this part of the set-up is complete, the patient is fully heparinized and the ACT used to confirm the adequacy of anticoagulation. Cannulation of the ascending aorta and RA will follow. A double purse-string suture is used to secure the aortic cannulation site and further purse-string sutures are placed in the RA to secure the venous cannula or cannulae, which drain blood into the heart–lung machine. Another purse-string suture will be placed lower in the ascending aorta for the cardioplegia line, which will be essential to stop and intermittently perfuse the heart during the ‘cross-clamp time’. Additional cannulation sites can be the right superior pulmonary vein for the LV vent insertion, the RA for the retrograde cardioplegia cannula or the PA for further venting. Venting the heart chambers and great vessels provide a relaxing bloodless field, which is an important aspect of a good set-up. Once everybody is happy with the ACT and the conduits are ready, the patient is ‘put on bypass’: blood is drained from the RA into the oxygenator, by simple gravity or vacuum-assisted. Oxygenated blood is then pumped into the aorta and the ventilator is switched off.