Epidemiology and aetiology

Ischaemic heart disease (IHD) includes all the consequences of narrowing or occlusion of the coronary arteries by atherosclerosis. These include angina, myocardial infarction and heart failure, arrhythmias and mitral valve incompetence. Myocardial infarction is the commonest cause of death in the UK. The risk factors and pathogenesis of atherosclerosis are the same as for peripheral vascular disease, discussed on page 203. The heart is supplied by the right and left coronary arteries. The left coronary artery is the bigger vessel and has a main stem 1 cm in length which divides into the left anterior descending artery and the circumflex artery (Fig. 14.1).

Figure 14.1 Anatomy of the coronary arteries.

Clinical features

The manifestations of coronary artery disease vary depending on which vessels are affected and are summarised in Box 14.1.

Investigation

Coronary angiography is the definitive investigation for patients suspected of having ischaemic heart disease. Non-invasive techniques such as MRA are likely to replace diagnostic coronary angiography in the future.

Treatment

Coronary artery bypass grafting (CABG)

Coronary artery bypass graft is one of the most commonly performed major operations. Most are performed using cardiopulmonary bypass with hypothermia (Fig. 14.2).

Figure 14.2 Cardiopulmonary bypass.

Most operations are carried out through a median sternotomy incision using cardiopulmonary bypass. Mini-thoracotomy and endoscope operations are becoming more widely used. Some procedures are performed on the beating heart without bypass (off-pump surgery). The internal thoracic artery is the first choice conduit, followed by the long saphenous vein or radial artery. First elective operations have a mortality of 0.5–2.5%, rising to as high as 20% for revision or emergency procedures.

The results for angina are excellent, with 85% of patients relieved of symptoms without medication; a further 5% are improved but require anti-anginal drug therapy.

Other procedures that may be carried out at the time of CABG include:

• left ventricular aneurysm excision (mortality 5%)

• mitral valve repair/replacement (mortality 15%)

• ablation of ventricular arrhythmic focus (mortality 30%)

• ventricular septal rupture (mortality 30%).

Complications include:

• death

• stroke (risk raised if carotid arteries stenosed)

• myocardial infarction

• limb ischaemia/compartment syndrome (especially if intra-aortic balloon pump used perioperatively)

• pneumonia

• wound problems from saphenous vein harvest

• intrathoracic bleeding

• graft occlusion with recurrence of angina/infarction

• arrhythmias.

Stenting versus CABG for ischaemic heart disease

Indications for coronary bypass surgery are summarised in Box 14.2.

Box 14.2 Indications for coronary artery bypass surgery

Failure of medical therapy with chronic stable angina

Unstable angina

Left main stem disease

Symptomatic three-vessel disease

Post-infarct angina

Acute myocardial infarction with cardiogenic shock

Failed PTCA

Reoperation for recurrent symptoms

Congenital anomalies, e.g. anomalous origin of any coronary artery

Kawasaki disease

Coronary disease concomitant with other cardiac procedures

Large clinical trials have shown that PTCA and stenting are effective in treating angina, with lower morbidity than surgery. However, the re-intervention rate is higher. CABG achieves better long-term survival, and is more effective in patients with triple vessel disease (Fig. 14.3).

Figure 14.3 An algorithm for the management of patients with suspected coronary artery disease (CAD). This pathway is changing as stent technology improves.

This is a subject of intense international debate.

Infective/subacute infective endocarditis

This is a common condition which mainly affects aortic and mitral valves, and tricuspid in intravenous drug users. There is often an underlying valve abnormality (Table 14.1). The common organisms responsible are indicated in Table 14.2.

Table 14.1 Abnormalities associated with infective endocarditis

Table 14.2 Organisms involved in infective endocarditis