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Ischaemic heart disease

Introduction

As cardiomyocytes generate almost all their energy from oxidative phosphorylation they are strictly dependent on continuous flow of oxygenated blood.

Ischaemic heart disease (IHD) is an umbrella term for all conditions characterised by ischaemia of the myocardium. Because this is almost always due to coronary artery atherosclerosis, the term coronary artery disease (CAD) is virtually equivalent to IHD and they’re often used interchangeably.

We can distinguish acute and chronic ischaemic heart disease. Acute ischaemic heart disease is referred to as acute coronary syndrome (ACS). Chronic ischaemic heart disease is referred to as chronic coronary syndrome (CCS) or stable ischaemic heart disease.

Angina pectoris is the name of the characteristic pain associated with different types of ischaemic heart disease. Angina is typically a pressing retrosternal chest pain, sometimes described as someone sitting on the patient’s chest. The pain may radiate to the arm, the neck, or the jaw.

Etiology

In more than 90% of cases ischaemia occurs due to obstructive atherosclerotic plaques in the coronaries, a condition called coronary artery disease. As such, the risk factors for coronary artery disease are the same as for atherosclerosis in general, like hypertension, dyslipidaemia, diabetes mellitus, etc.

Symptoms usually occur when the atherosclerotic plaque occludes more than 70% of the lumen. At this point the critical stenosis point has been reached.

The remaining 10% of cases occurs due to:

• Abnormally increased demand
• Diminished blood volume
• Diminished oxygenation of blood
• Diminished oxygen-carrying capacity of blood

Chronic ischaemic heart disease

The classical manifestation of chronic ischaemic heart disease is stable angina. In stable angina, coronary artery stenosis has reached the critical 70%. This is sufficient for perfusion of the myocardium in rest. However, as soon as the myocardial blood requirement increases, such as during walking up stairs or exercise, the perfusion will be insufficient for the myocardium. This causes angina pectoris. Symptoms are relieved upon rest or after application of nitro-glycerine, a vasodilator.

Vasospastic angina (Prinzmetal angina) is caused by coronary artery vasospasm, with or without underlying coronary artery disease. Vasospasm may occur in rest and usually unrelated to exercise.

Ischaemic cardiomyopathy is caused by ischaemic damage to the myocardium. This may occur due to long-term chronic ischaemic heart disease, or due to previous myocardial infarction. This damage to the myocardium may lead to heart failure.

The healthy myocardium that isn’t damaged by ischaemia will always try to compensate for the damaged myocardium. Left ventricular hypertrophy and dilation are usual findings, along with fibrosis of the damaged myocardium. Microscopically we find myocardial hypertrophy, fibrosis and diffuse subendocardial vacuolization.

Sudden cardiac death

Sudden cardiac death is defined as unexpected death from cardiac causes early after the onset of symptoms, or without symptoms. It occurs due to a ventricular arrhythmia, but the cause of the ventricular arrhythmia varies.

Sudden cardiac death almost exclusively occurs in people with structurally abnormal hearts, either due to chronic ischaemic heart disease, acute myocardial infarction, cardiomyopathy, myocarditis, etc.

It’s important to give proper treatment of ischaemic heart disease to prevent sudden cardiac death, especially in those with acute myocardial infarction.