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Sudden and Unexpected Death from Natural Causes. Section 1 General consideration 1. Definition of sudden unexpected death
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Section 1 General consideration 1. Definition of sudden unexpected death The definition of sudden unexpected death is referred to as a sudden death of an individual who appears healthy and dies suddenly within a few minutes or several hours due to pre-existing disease or functional disorder. The official definition of a sudden unexpected death as described by WHO is that an individual dies from natural diseases within 24 hours since symptoms appear.
Three characteristics in the cases of sudden and unexpected death: (a) The suddenness of the death; (b) The unexpectedness of the death; (c) Natural diseases or functional disorders as the causes of death. The violent deaths, although occurring suddenly in most cases as they do, are not within the scope of sudden unexpected death.
2. Causes of sudden unexpected death Diseases of any human physical system may lead to sudden unexpected death. Leading causes: diseases of cardiovascular system, the diseases of central nervous system and respiratory system rank second. The diseases of gastrointestinal and genitourinary system are less commonly to cause the sudden unexpected death.
Diseases of respiratory system are most commonly seen to lead to sudden death in neonate and children. Diseases of cardiovascular system account for the major cause in the sudden unexpected deaths in adults. Certain external factors such as emotional distress and physical exertion may predispose the onset of the disease that leads to the sudden death.
3. The purposes for medico-legal investigation in sudden unexpected death Medico-legal autopsy must be conducted under the following conditions: 1. In cases suspected to be violent death. 2. In cases of violent deaths that have been disguised to be sudden unexpected death from natural causes. By medico-legal investigation, some occupational or grave infectious diseases may be detected. Proper prophylactic measurements may be taken.
Section 2 The common causes of sudden and unexpected death 1. Cardiovascular system Most sudden and unexpected deaths are caused by lesions in the cardiovascular system. (1) Coronary artery disease i. Coronary insufficiency Coronary insufficiency from narrowing of the lumen of major vessels may lead to chronic ischemia and hypoxia of the muscle distal to the stenosis. If the ischemia region involves the pace-maker node or a major branch of the conducting system, the liability to rhythm abnormalities is increased.
ii. Complications of atheroma Ulcerative atheromatous plaques may rupture, filling the vessel partially or completely with cholesterol, fat and fibrous debris. The endothelial cap of a ruptured plague may act as a valve within the vessel and cause a complete obstruction. Sub-intimal hemorrhage, where bleeding occurs into a plague, expanding it suddenly and often reducing or blocking the lumen.
iii. Coronary thrombosis Less than one-third of sudden cardiac deaths has been detected to have a coronary thrombus at autopsy as pure stenosis and complications of atheroma are much more common. Thrombi are still frequent and are often associated with a myocardial infarct. Multiple thrombi also occur, some being post-infarction, due to a stagnant circulation.
iv. Myocardial infarction Myocardial infarction occurs when a severe or a complete occlusion occurs in a coronary artery, and if the collateral circulation is not sufficient to maintain the muscle. If 70% or more of the lumen of a major branch is blocked, an infarct commonly develops. The effect of a large infarct is either to reduce cardiac function because of pump failure, as the necrotized muscle cannot contract, or it leads to arrhythmias and ventricular fibrillation. The fatal effects of an infarct may appear at any time after the muscle has become ischemic though many hours are needed for an infarct to become visible.
Figure 17.1 The paler area at the lower edge is a regional myocardial infarction of several days' duration. Figure 17.2 Haemopericardium due to a ruptured anterior myocardial infarct. Death was due to cardiac tamponade.
v. Rupture of myocardial infarct A ruptured myocardial infarct may cause sudden death from a hemopericardium and cardiac tamponade. Most commonly found in old person, who have a soft, senile myocardium, but can occur in anyone. Tends to take place two or three days after the onset of the infarction when the necrotic muscle is becoming soft. Mural thrombus may develop over the inner surface of a myocardial infarct. Parts of it may break off, leading to emboli in the systemic circulation, which may cause infarcts in kidney, spleen and brain.
vi. Myocardial fibrosis Another complication of myocardial infarction is the myocardial fibrosis which may develop when a myocardial infarct heals. Large plaques on the endocardium, or in the wall of the ventricle or septum may later interfere with cardiac function or with the conducting system. A large fibrotic area on the free wall of the left ventricle may later swell due to the high pressure during systole, forming a cardiac aneurysm. These aneurysms rarely rupture, as they are tough and fibrotic.
vii. Papillary muscle rupture This can occur due to infarction and necrosis, and allow part of the mitral valve to prolapse, with signs of valve insufficiency and perhaps sudden death.
(2) Hypertensive heart disease This condition may lead to sudden cardiac death from left ventricular hypertrophy. In hypertension, the heart may increase to 600 g or more and the muscle mass thus outgrows it coronary supply, even if the coronary arteries are healthy. Atheroma is often associated with hypertension, so that the enlarged muscle mass is further deprived of even a normal flow and becomes ischemic. Such muscle is unstable and irritable and easily jumps into arrhythmias and fibrillation, which causes the sudden death of an individual.
(3) Primary myocardial disease This is much less common than the ischemic condition of the heart. It may include several kinds of myocardial lesions. Myocarditis that occurs in many infective diseases, such as diphtheria and virus infections including influenza, disseminated sarcoidosis ( myocardial sarcoidosis). In sudden death pathology, a myocarditis of unknown aetiology is sometimes discovered on histology of autopsy tissues, known as isolated, Fiedler’s or Saphir’s myocarditis.
Cardiomyopathy, where a large heart shows certain abnormal histological characteristics, including： HCM (hypertrophic cardiomyopathy), : huge hearts of over 1000 g; asymmetric massive thickening of ventricular walls. CCM (congestive cardiomyopathy) : dilatation of the chambers with thinning of the ventricular walls. RCM (restrictive cardiomyopathy ): evident fibrotic thickening of the endomyo-cardium. ARVD/C (arrhythmogenic right ventricular cardiomyopathy(dysplasia)) : displacement of myocardial fibers by fatty tissue and collagen fibers.
2. Central nervous system (1) Ruptured berry aneurysm Subarachnoid hemorrhage: a relatively common cause of sudden collapse and often rapid death in young to middle-aged people, due to a ruptured aneurysm of a basal cerebral artery. Berry aneurysms develop at a weak spot in the vessel wall, which may be of any size from a millimeters to several centimeters in diameter and may be single or multiple. The apex can rupture, especially at any sudden rise in blood pressure, such as from exercise or emotion.
(2) Cerebral hemorrhage Sudden bleeding into the brain substance is common, usually in old age and in those with significant hypertension. The hemorrhage most often takes place in the external capsule of one hemisphere from rupture of a lenticulo-striate artery. The sudden expansion of a hematoma compresses the internal capsule and may destroy some of it, leading to a hemiparesis. Other places where bleeding occurs include the cerebellum and mid-brain. Some bleedings in the brain-stem may lead to marked hyperpyrexia.
Figure 17.5 A large intracerebral haemorrhage in the internal capsule, with extension into the ventricle.
Figure 17.6 Pontine haemorrhage in a hypertensive individual.
(3) Cerebral thrombosis and infarction This is rarely a cause of sudden or unexpected death, as the process is relatively slow, though neurological symptoms and signs consequent on infarction of a substantial part of the brain may be severe.
3. Respiratory system The major cause of sudden death within the respiratory organ is again vascular. Pulmonary embolism In almost every case, the source of the emboli is in the leg veins and pelvic veins. After any tissue trauma, or even surgical operation, especially where immobility or bed rest occurs, deep vein thrombosis develops. Other rare causes of sudden death in the respiratory system include a massive hemoptysis from cavitating pulmonary tuberculosis or from a malignant tumor, though the latter is a rare complication.
4. Gastrointestinal system Once again, causes of death in this system may be vascular, in that very severe bleeding from a gastric or duodenal peptic ulcer can be fatal in a short time, but most are moderate enough to allow medical or surgical treatment. Perforation of a peptic ulcer can be fatal in hours if not treated and intestinal gangrene due to strangulated hernias and torsion due to peritoneal adhesions can also be fulminating and fatal conditions.
