Computational Intelligence in Cardiology and Heart Disease Diagnosis - Computational Intelligence in Biomedical Engineering - page 173

I aVR V1 V4

II aVL V2 V5

III aVF V3 V6

ST elevation in leads II, III, and VF

Acute inferior myocardial infarction

FIGURE 4.24
ECG of acute inferior myocardial infarction depicting ST elevation in the infe-
rior leads II, III, and aVF and a reciprocal ST depression in the anterior leads.
(Modified from Dean Jenkins and Stephen Gerred, http://www.ecglibrary.
com/ecghome.html. With permission.)

occurs due to factors such as atherosclerosis in the blood vessels. A major
symptom is angina pectoris, which is characterized by paroxysmal attacks
of chest pain usually caused by ischemia, which does not induce infarction.
There are several types where the typical angina is stable angina characterized
by paroxysms of pain related to exertion and relieved by rest. Prinzmetal's
angina occurs at rest and is caused by reversible spasm in normal to severely
atherosclerotic coronary arteries. In this case, the ST segment of the ECG
is either elevated or depressed during the attacks. Unstable angina is associ-
ated with prolonged pain, pain at rest, or worsening of pain similar to stable
angina patients but the symptoms vary or are unstable. In extreme cases,
sudden cardiac death can result usually within 1 hour of a cardiac event or in
the absence of symptoms.

4.5.4 Blood Vessel and Valve Diseases
Several diseases affect the AV valves, aortic valve, and pulmonic valves result-
ing in narrowing or leaking, which reduces their eciency. The majority of
valvular heart disease cases are due to congenital abnormalities or from inflam-
mation due to diseases such as rheumatic fever or syphilis. In the case of
rheumatic fever, the mitral and aortic valve are most frequently affected.
Thickening of the mitral valve results in narrowing of the orifice, mitral
stenosis , which blocks the flow of blood from the left atrium to the left ventricle
causing increased pressure in the left atrium due to incomplete emptying. As a
result, cardiac output is reduced because there is inadequate filling of the left
ventricle. Mitral stenosis also causes characteristically abnormal heart sounds
due to turbulence in blood flow and opening and closing of the narrowed valve.