Sudden cardiac death: causes, premonitory symptoms and treatment
Sudden cardiac death in medicine refers to an unexpected (or ‘apparently’ unexpected) death from cardiac causes that occurs in often asymptomatic patients, immediately after the onset of symptoms (within an hour) or even without the onset of symptoms
In adults, it is a complication and often the first clinical manifestation of ongoing ischaemic heart disease (i.e. a disease in which the heart is poorly supplied with blood, as typically occurs in angina pectoris and myocardial infarction).
Sudden cardiac death is a far from rare event
It alone is responsible for more than 50,000 deaths a year and is the cause of 50% of all deaths from heart disease.
Causes and risk factors of sudden cardiac death
Among the most important causes and risk factors for sudden cardiac death are a number of conditions and diseases
- ischaemic heart disease (the most common cause, approximately 9 out of 10 cases);
- congenital coronary malformations;
- mitral valve prolapse;
- myocarditis and endocarditis;
- dilated or hypertrophic cardiomyopathy (from chronic arterial hypertension);
- pulmonary hypertension;
- endocranial hypertension that may lead to pathological reflex bradycardia;
- acquired or inherited alterations of the conduction system;
- cardiac malformations;
- cardiac arrhythmias (e.g. bradyarrhythmia or ventricular fibrillation).
Critical stenosis (narrowing >75%) from coronary atherosclerosis of at least one of the three main cardiac vessels is present in 90% of those suffering sudden cardiac death.
Arrhythmias occurring in the absence of a structural cardiomyopathy can lead to sudden death, the most important cause being long QT syndrome, characterised by increased cardiac excitability and episodic ventricular arrhythmias.
Another cause of sudden cardiac death is pathological bradycardia (bradyarrhythmia).
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Other risk factors for sudden cardiac death
High levels of aldosterone (>200 pg/ml blood) combined with high levels of cortisol (>21.1 mg/dL) have been strongly correlated with the event of sudden death, in patients considered at risk for such an event (and with all-cause mortality in haemodialysed type 2 diabetics).
Sudden cardiac death may also be a consequence of chronic abuse of anabolic steroids that increase the size of muscles, including heart cells, but without a parallel increase in contraction force. On the contrary, these cells often die and are not replaced by other cells, but by fibrous tissue that remains even when the steroid intake is discontinued, with permanent damage to the heart. An insufficient number of cells can be followed by episodes of inadequate heart pressure and blood supply, and infarction.
Important risk factors for sudden cardiac death are family history, being overweight, obesity, cigarette smoking and drug use.
Symptoms and diagnostic tools
Often patients presenting with sudden cardiac death were either completely asymptomatic, i.e. they had no symptoms at all, or they had non-specific symptoms such as:
- asthenia (tiredness)
- easy fatigability;
- dyspnoea (difficulty breathing;
- dizziness;
- frequent fainting.
More specific ‘premonitory’ symptoms are undoubtedly the presence of a severe arrhythmia such as bradyarrhythmia and frequent fainting, as well as the typical symptom of ischaemic heart disease, i.e. chest pain in the sternal area radiating to the left arm.
In the presence of such symptoms, the patient is advised to undergo a cardiological examination, which also includes an electrocardiogram, Holter, blood tests and cardiac ultrasound with colordoppler.
Therapies in case of sudden cardiac death
Cardiac massage and, if possible, rapid defibrillation are the main remedies in cases of sudden cardiac death, representing – for the patient – the difference between life and death.
Approximately 25% of cases could be resuscitated if defibrillated within 4 to 5 minutes, while for every additional minute the chance of survival decreases by 10%; time is in fact a key factor in survival, and not only in the case of patient survival, the quicker the medical measures have been taken and the less possible irreversible brain damage caused by the lack of blood flow to the organs.
An untimely intervention could still save the patient’s life, but he or she could enter an irreversible state of coma.
Prevention of sudden cardiac death
For individuals at risk, e.g. with a family history of severe arrhythmias (e.g. bradyarrhythmia) or who have survived a previous cardiac arrest, an important prevention tool may be the implantation of a pacemaker with a subcutaneous defibrillator, called an ICD defibrillator.
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