Sudden death

Abstract

Sudden death can be defined as an unexpected event that happens in healthy people or in stable patients. It must occur within one hour from the onset of the first symptoms, and it is precipitated by a cardiac arrest, which is irreversible for the absence of an adequate and prompt assistance or for an intrinsic cardiac disease. Heart block is usually preceded by severe disturbances of the cardiac rhythm, as ventricular fibrillation or bradycardia. In a first group of diseases, at the basis of this event, a primitive disorder, directly correlated with an abnormality of cell membrane channels involved in the exchange of electrolytes, can be found, as in Brugada's syndrome. A more common condition is represented by infarct or severe ischemia, sometimes known before, that determine significant alterations in the cardiac rhythm, followed by ventricular fibrillation and cardiac arrest. Rarer is an acute hemopericardium, where a sudden severe haemorrhage takes place inside the pericardium, with a primary effect of acute cardiac tamponade; in absence of recent cardio-thoracic surgery, a cause can be the rupture of an aortic aneurysm, involving its first intrapericardic tract. Many other cardiac diseases, as acute myocarditis, left ventricular hypertrophy, hypertrophic cardiomyopathy, dilatative cardiomyopathy, restrictive cardiomyopathy, Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC), pulmonary or aortic stenosis, atrial myxoma, and, rarely, Cyanotic Congenital Heart Diseases (CCHD), can induce a sudden cardiac arrest. In other conditions, the cardiac arrest follows an acute primary disease of one or multiple apparatuses. At first, an abrupt and massive haemorrhage, followed by a fall in the venous return, can produce an electro-mechanical cardiac dissociation, with subsequent cardiac arrest. A similar condition is represented by anaphylactic shock, where a sudden peripheral vasodilatation with an abrupt fall in blood venous return can be associated with an increased pulmonary vascular resistance, bronchospasm and coronary vasoconstriction by circulating histamine. A characteristic condition is the onset of an acute respiratory failure, followed by acute hypoxia, hypercapnia and acidosis. It can happen after tension pneumothorax, complicating a respiratory insufficiency, or in case of bilateral pneumothorax. Moreover, a sudden increase in pulmonary resistance accompanied by severe hypoxia, as in acute thrombo-embolism of the pulmonary artery, can determine a sudden cardiac arrest. Another cause, even rarer, of cardiac arrest is finally represented by a spontaneous cerebral haemorrhage, where a rapid rise of intracranial pressure, but more often a direct damage of vital cerebral centres, leads to a direct acute cardio-respiratory failure.