Synopsis: How do we approach patients?

Syncope is a transient, self-limiting episode of loss of consciousness that usually results in a fall to the ground. Its onset is rapid and recovery is automatic, complete and usually immediate. The underlying mechanism is a brief period of global cerebral hypoperfusion.

The initial assessment of a patient with syncope is based on a careful history taking, clinical examination, orthostatic blood pressure testing and electrocardiogram.

Three key questions must be answered in the initial assessment:

Is the loss of consciousness due to syncope or not?

The differential diagnosis of syncope from other “non-syncope” conditions associated with true or apparent loss of consciousness is the first diagnostic challenge and prompts further investigation.

Is there evidence from the patient’s history that favors the diagnosis of syncope?

Taking an accurate history is key and often leads to the diagnosis or perhaps paves the way for further evaluation.

Is there underlying heart disease or not?

The absence of signs that suggest or diagnose heart disease excludes cardiac causes of syncope. In contrast, the presence of heart disease at baseline is a strong predictor of cardiac syncope, but with low specificity – approximately half of patients with heart disease have cardiac syncope.

Syncope is classified aetiologically as follows: neurogenic syncope (reflex type), syncope due to orthostatic hypotension, and syncope due to cardiac causes (arrhythmias, structural heart disease, or cardiopulmonary disease). Regardless of its mechanism, every syncope is associated with transient global cerebral hypoperfusion (most often due to reduced systemic blood pressure) which is also the main factor leading to loss of consciousness.

It is this cerebral hypoperfusion that distinguishes syncope from “non-syncope” causes, in which the impaired level of consciousness is not due to reduced cerebral perfusion. Many level of consciousness disorders can mimic syncope. In some episodes consciousness is actually lost, but the mechanism is not related to cerebral hypoperfusion. Such cases are: epilepsy, metabolic disorders (hypoxemia, hypoglycemia), poisonings and transient ischemic attacks especially in the vertebral-basal artery. In other cases, consciousness is only apparently lost, as in psychogenic pseudosyncope, shock, and episodes of falling to the ground.

The initial evaluation may lead to a specific diagnosis (so that further evaluation may not be needed and treatment may be planned), in the following conditions:

• Parasympathetic syndrome: in this case there are classic triggers such as fear, severe pain, emotional stress or prolonged standing and are associated with typical prodromal symptoms (benign form).
• Occasional syncope: syncope during or immediately after urinating, defecating, coughing or swallowing.
• Syncope due to orthostatic hypotension: if there is a record of orthostatic hypotension associated with syncope or pre-syncope. A decrease in systolic blood pressure of more than 20 mmHg or a decrease in systolic blood pressure of less than 90 mmHg 1 or 3 minutes after taking the upright position is defined as orthostatic hypotension regardless of symptoms and is usually accompanied by tachycardia.
• Syncope associated with cardiac ischemia: when symptoms are accompanied by electrocardiographic changes of acute ischemia with or without myocardial infarction, regardless of mechanism.
• Syncope associated with recorded arrhythmia.

Usually, the initial evaluation leads to the suspicion of a diagnosis, which must be confirmed by further testing.

Suspected or diagnosed heart disease is associated with a higher risk of arrhythmias and one-year mortality. In these patients, a cardiological check-up is recommended (ultrasound cardiogram, stress echo, electrophysiological study and/or rhythm monitoring with an implantable recorder – ILR).

If no arrhythmia is identified as the cause of syncope, further investigation is suggested to rule out syncope of neurogenic etiology – it concerns patients with recurrent or severe syncope and includes the tilt test, carotid bulb massage, 24-hour rhythm recording (Holter) and finally implantation subcutaneous rhythm recorder (ILR).

If a cause of syncope is confirmed, specific treatment is initiated, however, the cause of syncope may remain unexplained despite the initial evaluation. In these cases, a re-evaluation is recommended with the participation where there is an indication of other specialties.