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<strong>KCE</strong> Reports 82 Multislice CT in Coronary Heart Disease 5<br />
2 BACKGROUND<br />
2.1 CORONARY HEART DISEASE<br />
2.1.1 Pathophysiology<br />
Coronary heart disease (CHD) or coronary artery disease (CAD) refers to any cardiac<br />
disease caused by an impaired blood flow and deficient oxygen supply to <strong>the</strong><br />
myocardium, due to a<strong>the</strong>romatous narrowing of <strong>the</strong> coronary arteries. It is one of <strong>the</strong><br />
main causes of mortality and morbidity in Western countries. It can be manifested by<br />
stable angina pectoris, acute coronary syndromes (ACS) - including myocardial<br />
infarction (MI) and unstable angina -, or sudden death. Loss of myocardial tissue due to<br />
MI can lead to heart failure and it can constitute <strong>the</strong> anatomical basis for arrhythmias,<br />
leading to “sudden death”. Cardiac disease may also be related to high blood pressure,<br />
valvular dysfunction, congenital abnormalities, primary cardiac muscle problems, or<br />
o<strong>the</strong>r rarer conditions. These are not part of <strong>the</strong> disease spectrum of CHD.<br />
Two separate arteries carry oxygenated blood to <strong>the</strong> heart muscle: <strong>the</strong> right and <strong>the</strong><br />
left coronary artery. The first part of <strong>the</strong> left coronary artery, known as <strong>the</strong> “left main<br />
stem”, shortly after its origin divides into two branches: <strong>the</strong> circumflex artery (Cx) and<br />
<strong>the</strong> left anterior descending artery (LAD). Because <strong>the</strong> two branches of <strong>the</strong> left<br />
coronary artery are generally considered separately in clinical practice, it is common to<br />
refer to three coronary arteries instead of <strong>the</strong> anatomically more correct “two”.<br />
Depending on whe<strong>the</strong>r one, two or three coronary arteries are significantly involved in<br />
<strong>the</strong> a<strong>the</strong>romatous proces, <strong>the</strong> labels single, double, or triple vessel disease are<br />
attributed. Due to its prognostic significance, if <strong>the</strong> left main stem is involved in <strong>the</strong><br />
a<strong>the</strong>romatous process in a given patient, it is stipulated as such.<br />
The underlying mechanism of CAD is a gradual build-up of fatty material into <strong>the</strong><br />
coronary vessel wall that leads to <strong>the</strong> formation of a<strong>the</strong>romatous plaques. The<br />
pathophysiological mechanisms leading to stable angina pectoris or an ACS are different.<br />
It is traditionally accepted that a plaque has to reduce <strong>the</strong> internal diameter if a vessel by<br />
at least 50% (or >75% reduction in cross sectional area), in order to reduce blood flow<br />
through <strong>the</strong> coronary artery during exertion and provoke ischemia and angina pectoris.<br />
ACSs on <strong>the</strong> o<strong>the</strong>r hand result from a sudden blockage of coronary blood flow, due to<br />
rupture of a vulnerable a<strong>the</strong>romatous plaque, not necessarily involving flow-limiting<br />
stenoses. 1-3<br />
The main risk factors for CAD development are tobacco use, high blood pressure,<br />
raised blood cholesterol, and diabetes mellitus. Several interventions aiming to prevent<br />
CAD have been well documented, ranging from lifestyle changes to a daily and lifelong<br />
intake of drugs. The best documented are smoking cessation, blood pressure lowering,<br />
anti-platelet aggregation <strong>the</strong>rapy (low-dose aspirin) and pharmaceutical lipid<br />
management (statins).<br />
2.1.2 Definitions<br />
Symptomatic CAD can be manifested ei<strong>the</strong>r by stable angina pectoris, as an ACS or as<br />
sudden death. Loss of a substantial part of myocardial tissue can lead to heart failure,<br />
cardiogenic shock and death. Heart failure is a distinct clinical syndrome characterised<br />
by symptoms such as breathlessness and fatigue and signs such as fluid retention. The<br />
clinical spectrum of CAD is displayed in Table 1.<br />
Table 1: Clinical spectrum of CAD.<br />
Pathology<br />
Symptomatic CAD<br />
Asymptomatic CAD<br />
stable angina<br />
ACS<br />
O<strong>the</strong>r<br />
Manifestations<br />
unstable angina<br />
AMI<br />
Sudden death, heart<br />
failure, …