Sudden Cardiac Death

The most common cause of sudden unexpected cardiac death in adults is severe stenosis or thrombotic occlusion of a major coronary vessel, often in association with recent or healed myocardial infarction. ANATOMY OF THE CORONARY ARTERIES

The majority of sudden coronary deaths can be attributed to disease in the proximal 25mm of the left anterior descending coronary artery and in the proximal 45mm of the right main vessel.

Pathologists should examine these segments with particular care. If they do not show substantial narrowing or thrombotic occlusion, the proximal portion of the circumflex artery, the obtuse marginal branch of the circumflex artery, the first diagonal branch of the left anterior descending and distal portion of the right coronary artery close to the right margin of the heart should be dissected with care.

Hypertension is also a recognised cause of sudden cardiac death and this is not necessarily related to coexistent ischaemic heart disease . There is evidence of increased ventricular arrhythmias in patients with hypertensive left ventricular hypertrophy (Visit: Hypertensive heart disease ) and also in chronic alcoholism.

ASSESSMENT OF ISCHEMIC DAMAGE ; Angina pectoris

- Vascular causes of sudden death other than atherosclerosis:

Dangerous anomalies in the coronary arteries: (i) One artery arises in the aorta while the other ostium is in the pulmonary artery. An intramyocardial left to right shunt of blood develops and the arteries become dilated. (ii) Two coronary ostia arise in one aortic sinus. An arterial branch has to cross right to left or left to right depending on which sinus the ostia are present.

Kawasaki's disease: Dilated arteries containing thrombus.

Spontaneous dissection of a coronary artery:

Bridging: Layer of myocardium covers the epicardial surface of a major coronary artery.

- Conduction system :

There is a risk of sudden death in patients with complete A-V block or with Wolff-Parkinson-White syndrome.

A-V nodal mesothelioma - cystic nodule just anterior to the coronary sinus in the right atrium. MESOTHELIOMA OF ATRIOVENTRICULAR NODE

An approach to examination of the heart in sudden natural death:

The following questions should be answered -

- Is the death really natural? In this respect the pathologist is heavily dependent on the police officers for detecting suicides and unnatural death.

- Is death due to extracardiac causes? A wide range of extracardiac conditions can kill rapidly. Most are readily identified. The commonest causes are pulmonary emboli and aortic aneurysms of all types, including dissection.

- Is death cardiac? Approximately 80% of sudden natural death is cardiac in origin and of this the greater part is due to coronary atherosclerosis producing ischaemic heart disease.

There is high level of atherosclerosis, particularly in males and this may complicate the issue of whether coronary disease actually caused death.

Sudden death in ischaemic heart disease is precipitated by ventricular fibrillation but there are several mechanisms by which this develops.

The two main mechanisms are new acute myocardial ischaemia and chronic myocardial damage with fibrosis initiating ventricular tachycardias. Myocardial infarction

The pathologist should look for the features that indicate these mechanisms and can then give ischaemic heart disease as a cuase of death.

If coronary stenosis with a normal myocardium is capable of causing sudden death, the mechanism is unclear.

- Are any cardiac non-ischaemic conditions capable of producing sudden death?

-If no cause of death is apparent by this stage, recheck history and consider carrying out toxicological examination by consultation.

Certain conditions do seem to carry a risk of sudden death and include epilepsy and chronic alcoholism.

The heart is macroscopically and microscopically normal. The previous medical history of the subject should be reviewed and any family history of sudden death is noted. History of previous syncopal attacks is strongly suggestive of cardiac arrhythmias.

SUDDEN DEATH IN ISCHAEMIC HEART DISEASE- MECHANISM

Mechanism	Morphology	Probability of causal relation to death
Acute myocardial ischaemia	Coronary atheroma with stenosis and a) coronary thrombosis and acute infarction b) coronary thrombosis alone	Very high probability
Chronic ischaemic myocardial damage	Coronary atheroma with stenosis and a) macroscopic LV scars b) macroscopic LV scars with hypertrophy c) No scars- LV hypertrophy (> 500g total heart weight)	Moderate to high probability Moderate probability
Coronary stenosis alone	Coronary atheroma with stenosis - normal LV myocardium	Questionable probability depending on number of stenoses and the circumstances.