Define sudden natural death. Describe its causes and medicolegal importance. Add a note on vagal inhibition.

Definition and Importance

• Its medicolegal importance lies entirely in the fact that a sudden death looks suspicious. It raises the possibility of poisoning, injury, criminal neglect or negligence, and it must therefore be investigated as a medicolegal case until a natural cause is established
• Other consequences — a false accusation may be made against a relative, a doctor or an employer; questions of insurance and compensation arise, particularly where death occurs at work; the survivorship question may follow; and a death soon after a medical procedure will be attributed to it unless a natural cause is demonstrated
• Every such death requires a full medicolegal autopsy with all three cavities opened, together with histology and toxicology; and a negative autopsy is a recognised and honest outcome in a proportion of cases

Special Entities

• Vagal inhibition (reflex cardiac arrest) — instantaneous death from cardiac arrest caused by parasympathetic overactivity, following a relatively trivial stimulus to a sensitive area: pressure on the carotid sinus or the neck, a blow to the epigastrium, the testicles or the larynx, sudden immersion in cold water, unexpected impact on the abdomen, instrumentation of the cervix, the pleura or the urethra, and puncture of a serous cavity. It is favoured by alcohol, fear and a full stomach
• The autopsy in vagal inhibition is negative — there are NO signs of asphyxia and often no injury at all, and the diagnosis is one of exclusion made from the circumstances. This has enormous medicolegal importance: a person may die from a slight blow or from light pressure on the neck that would not otherwise be fatal, and the assailant is nonetheless responsible
• Sudden infant death syndrome (SIDS, cot death) — the sudden death of an infant under 1 year, typically between 2 and 4 months, unexplained after a thorough autopsy, examination of the scene and review of the history. Risk factors are prone sleeping position, soft bedding, overheating, co-sleeping, maternal smoking, prematurity and low birth weight; the "Back to Sleep" campaign reduced its incidence dramatically. It is a diagnosis of exclusion, and the differential includes infection, metabolic disease, accidental suffocation and deliberate smothering, which the autopsy cannot always distinguish
• Sudden death in a young athlete — hypertrophic cardiomyopathy, anomalous coronary origin, arrhythmogenic right ventricular cardiomyopathy, and commotio cordis, in which a blow to the precordium at a critical moment in the cardiac cycle induces ventricular fibrillation with no structural damage at all

Investigation of a Sudden Death

Conduct of the Autopsy and Applied Aspects

• A complete autopsy with all three cavities opened, however obvious the apparent cause; a coronary thrombus does not exclude a coexisting subdural haematoma or a poisoning
• Examine the coronary arteries by serial transverse section at close intervals, and the conducting system where indicated; and weigh the heart and measure the ventricular wall thickness
• Preserve viscera for toxicology in every sudden death — poisoning is the principal alternative explanation, and the material cannot be recovered once the body is released
• Take histology from the heart, lungs, liver, kidneys and brain; myocarditis, early infarction and pulmonary embolism may be visible only microscopically
• Preserve blood in EDTA for molecular autopsy where the autopsy is negative in a young person, and advise cardiological screening of first-degree relatives; this is the one circumstance in which a forensic autopsy can save a life
• Examine the scene and the history in an infant death; SIDS cannot be diagnosed from the body alone, and the sleeping arrangements, the position in which the infant was found and the family history are part of the diagnosis
• Do not attribute a sudden death to a trivial injury without excluding natural disease, and equally do not overlook vagal inhibition, in which a trivial injury genuinely is the cause and the autopsy is otherwise normal
• Open the coronaries by serial transverse section, not longitudinally; a longitudinal cut can miss a short segment of critical stenosis entirely
• Examine the pelvis in every woman of reproductive age; a ruptured ectopic pregnancy is a classical sudden death and is missed when the abdomen is opened without looking
• Vagal inhibition is a diagnosis of exclusion from the circumstances, with a negative autopsy and no asphyxial signs — and the assailant remains responsible although the force was trivial
• SIDS cannot be diagnosed from the body alone; the scene, the sleeping arrangements and the history are part of the definition, and deliberate smothering is in the differential
• Preserve blood for molecular autopsy in a negative young death and advise family screening; it is the one circumstance in which a forensic autopsy can prevent another death
• A negative autopsy is an honest outcome in a proportion of sudden deaths, and inventing a cause to avoid it is worse than reporting the finding as it stands
• Coronary atherosclerosis is the commonest cause overall, and Indians develop it a decade earlier than Western populations, so it should not be excluded on age alone
• Massive haemoptysis from tuberculosis remains a real cause in India, and a sudden death with blood in the airways should not be assumed traumatic
• Take blood cultures where infection is possible; fulminant meningococcaemia can kill within hours and may leave little to see grossly
• Commotio cordis leaves no structural damage at all — a precordial blow at a critical instant in the cardiac cycle — and the autopsy will be entirely negative
• Ask about the family history in every young sudden death; a history of unexplained young deaths or drownings points directly to an inherited arrhythmic syndrome
• Sudden death looks suspicious and must be investigated as such; the medicolegal importance lies less in the disease than in excluding poisoning, injury and neglect
• Alcohol, fear and a full stomach favour vagal inhibition, and the combination appears repeatedly in the reported cases
• Cherry-pink lividity should prompt carboxyhaemoglobin estimation before any other explanation for a sudden death is accepted
• Check the ventricular wall thickness and heart weight; hypertrophic cardiomyopathy is the classical sudden death of the young athlete and is diagnosed on those measurements with histology
• Preserve viscera for toxicology in every case without exception; the body is released within hours and the opportunity does not return
• Take histology from heart, lung, liver, kidney and brain as a minimum; myocarditis and early infarction have no gross appearance
• Death within 24 hours of onset defines it, and every such death is a medicolegal case requiring a full autopsy irrespective of how natural the history sounds
• Look at the base of the brain for a ruptured aneurysm; subarachnoid haemorrhage in a young adult during exertion is a classical sudden death and is missed if the vessels are not examined.