The Syncope and Sudden Sports Death

Edited by Dr. Stefano Casali

Syncope

The etymology of the word derives from the Greek "syn koptein" which means to break, interrupt, cut. From the clinical point of view it is the "expression of an" alteration of brain functions, generally due to a decrease in cerebral blood flow or to a its electrical or metabolic dysfunction which can be the expression of various pathologies, from a benign and insignificant episode to sudden death.

Syncope is a short-term loss of consciousness with inability to maintain postural tone (with consequent fall to the ground if the subject is standing), it arises more or less abruptly and resolves spontaneously (different from the coma that lasts longer than long and requires medical intervention).
On the other hand, pre-syncope or lipothymia is a lesser degree of the same disorder characterized by a feeling of incipient fainting, weakness (asthenia), cold sweating, a feeling of nausea, but without complete loss of consciousness and without falling to the ground. Syncope is a fairly frequent occurrence in young subjects (about 5% of hospital admissions and 3% of cases that are visited in an emergency room).

A syncopal episode can occur more frequently:

in young subjects (up to 40-45% in some series) in which it is often isolated and has a benign significance;

in elderly subjects, in which it can more easily hide important diseases and have more serious consequences.

Loss of consciousness is the expression of an "alteration of brain function, which can be due to various causes:

a "sudden reduction or interruption" of blood supply to the brain;

a disturbance in the electrical function of neurons;

a metabolic disorder. Neurons are very sensitive to a lack of energy substrates, particularly a reduction in blood glucose = hypoglycemia.

In relation to the primary causes and the basic mechanism, three groups of syncopes are distinguished:

non-cardiovascular, due to other causes (neurogenic, metabolic ....);

cardiovascular, due to an acute decrease or interruption of the blood supply to the brain;

neuromediate, due to vasomotor instability mediated by nerve reflexes.

They can also be classified as:

Indeterminate syncopes: syncopes that at the end of all possible investigations with the means now available do not find a justification, are very few in number.

Syncopinon-cardiovascular: due to a pathology of the nervous system (neurogenic syncopes) eg. generalized seizure (grand mal attack). In this case, the subject suddenly falls to the ground in convulsions, often causing trauma injuries and bites of the tongue. The recovery of consciousness is slow and often the subject remains asleep. A very similar type of syncope can also be caused by a migraine crisis or a transient ischemic attack (TIA). Or following a sudden reduction in blood flow localized to a small area of the brain (microembolism, spasm of the blood vessels) which lasts from a few minutes to hours (more frequent in the elderly with atherosclerosis of the cerebral vessels or arterial hypertension).

Cardiovascular syncopes: they are quite frequent and are due to a "sudden interruption or reduction in generalized cerebral flow (that is, it affects the whole brain), resulting from a reduction in cardiac output which can be caused by different diseases and mechanisms, in turn can be divided into two main groups:

obstruction of blood flow inside the heart or main vessels (aorta, pulmonary artery, etc.) as occurs in some valve diseases (aortic valve or mitral valve stenosis), in hypertrophic cardiomyopathies in which the heart muscle (especially the left ventricle) is very hypertrophic and rigid and fills with difficulty. Syncope in these cases occurs during physical exercise:
- "effort syncope";
- a "cardiac arrhythmia

Cardiac output is the product of systolic output (amount of blood expelled with each contraction of the left ventricle) and heart rate. Arrhythmias that cause a sudden increase in heart rate (tachyarrhythmias) greatly shorten the duration of diastole, thus filling the heart. This can reduce systolic output and consequently cardiac output, causing pre-syncope or syncope. In this case, the subject may signal that the loss of consciousness was preceded by a strong palpitation or a sudden acceleration of the heartbeat. A drastic reduction in cardiac output can instead occur in those cases of arrhythmia in which the heart rate falls below normal beats (bradyarrhythmia). This occurs in alterations of the atrio-ventricular conduction system and can go as far as electrical asystole (the heart stops). In the "trained athlete" there is physiological vagotonia = benign arrhythmia that disappears when the individual stops training and is not accompanied by symptoms. In some subjects, however, vagotonia does not cease with maltraining and tends to worsen over time = non-physiological vagotonia .