Cardiac Path Online

Sudden Cardiac Death

Dr Sampurna Roy MD





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. 

Visit: 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 cause 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





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 Left Ventricular scars

b) macroscopic Left Ventricular scars with hypertrophy

c) No scars- Left Ventricular  hypertrophy (> 500g total heart weight)


Moderate to high probability



Moderate probability

Coronary stenosis alone Coronary atheroma with stenosis - normal Left Ventricular  myocardium Questionable probability depending on number of stenoses and the circumstances.



Cardiac Causes of Sudden Death in young adults:


 - Coronary artery atherosclerosis

 - Left ventricular hypertrophy (idiopathic and with hypertension)

 - Myocarditis

 - Dilated cardiomyopathy (including alcohol)

 - Hypertrophic cardiomyopathy

 - Aortic dissection (specially Marfan's syndrome):

 - Mitral valve prolapse   

 - Anomalous coronary artery

 - Arrhythmogenic right ventricular dysplasia

 - Cardiac sarcoid

 - Conduction abnormalities

 - Cocain abuse

 - Coronary arterial vasculitis (specially Kawasaki disease)



Non-Atherosclerotic causes of Sudden Cardiac Death


   Vascular :     

 - Anomalous coronary artery anatomy

 - Supra-aortic stenosis

 - Coronary aneurysms/arteritis


  Valvar :            

-  Aortic stenosis

- Mitral valve prolapse


  Myocardial :    

- Severe Left Ventricular hypertrophy

- Dilated cardiomyopathy

- Hypertrophic cardiomyopathy

- Right ventricular dysplasia

- Myocarditis

- Sarcoid

- Idiopathic myocardial fibrosis

- Myocardial tumours



- Aneurysms of membranous ventricular septum.

- Chronic AV block due to calcification.

- Mesothelioma of AV node.

- Pre-excitation - anomalous conduction pathway.


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