Syncope: A Review of Diagnosis and Treatment

Introduction

Syncope is a clinical syndrome in which temporary loss of consciousness is caused by insufficient blood supply to the brain, usually due to a sudden decrease in systemic blood pressure. When consciousness is lost, maintaining an upright position becomes impossible; therefore, syncope is usually associated with falls and an increased risk of injury.

True syncope is brief, with an episode rarely lasting longer than 1–2 minutes (1). A longer period of loss of consciousness suggests either that the episode is not syncope or that another pathology is present, for example, when head trauma occurs as a result of syncope and prolongs the period of unconsciousness.

Syncope is only one of many possible causes of transient loss of consciousness. Other causes include seizure disorders, traumatic brain injuries such as concussion, intoxication with various substances, metabolic disorders, and psychiatric disorders such as psychogenic pseudosyncope or pseudo-seizures (1). Distinguishing these conditions from true syncope is complex but crucial for providing the most effective treatment. This article discusses the causes, symptoms, diagnosis, and treatment of true syncope.

Epidemiology and Etiology of Syncope

Approximately 20% of the population experiences an episode of syncope during their lifetime (2). Syncope most commonly affects young people, often due to a vasovagal mechanism, and its incidence increases again in individuals over 70 years of age (1). The increased risk of syncope in older patients is associated with age-related diseases that impair the ability to respond to physiological stress that would not normally trigger a syncopal episode (3).

Syncope occurs more frequently in women than in men, although this also depends significantly on the characteristics of the population studied (2). In men, syncope is usually caused by cardiac factors (2). Syncope is a relatively common reason for patients to seek emergency hospital care, accounting for 1–3% of all cases (4). Approximately 35% of patients seeking medical attention because of a syncopal episode are hospitalized for further evaluation and treatment (4).

Cardiogenic syncope is caused by cardiac and vascular diseases such as cardiomyopathy, arrhythmias, or valvular dysfunction. Syncope of cardiac origin is associated with a poorer prognosis (5). An electrocardiogram (ECG) is essential in these cases to differentiate possible causes of syncope. Advanced cardiomyopathy, chronic heart failure, and valvular insufficiency are causes of hypotension that may lead to transient cerebral hypoperfusion. These patients often take medications that reduce heart rate, which may also contribute to cardiogenic syncope (5).

Ventricular arrhythmias, such as ventricular tachycardia and Torsade de pointes, are more common in older individuals with known cardiac conditions. These patients usually experience prodromal symptoms before syncope, which may warn of an impending syncopal episode. The alteration in consciousness may be accompanied by chest pain and shortness of breath. This type of syncope is not dependent on body position and may occur while lying down, sitting, or standing (5). These arrhythmias are also usually recorded on an ECG only after syncope has occurred and cannot be predicted in advance on the ECG.

Supraventricular tachyarrhythmias include supraventricular tachycardia and atrial fibrillation. With these arrhythmias, patients often complain of palpitations, chest pain, and shortness of breath. Patients typically experience prodromal symptoms, and a syncopal episode may occur while walking or attempting to stand because of developing hypotension.

Bradycardias include sinus bradycardia, high-degree atrioventricular block, cardiac pacemaker dysfunction, and adverse drug reactions (5). These patients usually have a well-established history of cardiac disease. During the presyncopal period, the patient may complain of chest pain, shortness of breath, reduced exercise tolerance, and fatigue. In these cases, syncope may occur suddenly without prodromal symptoms.

Syncope may also be caused by obstruction of blood flow, for example, aortic stenosis, hypertrophic obstructive cardiomyopathy, mitral stenosis, pulmonary stenosis, pulmonary embolism, or cardiac tamponade (5). Other causes may include myocardial infarction and acute aortic dissection. Common symptoms of these conditions include chest pain, neck and shoulder pain, shortness of breath, epigastric pain, and hypotension.

Neurally mediated reflex syncope, also known as vasovagal syncope, may be caused by emotional stress, such as fear, or physical pain. A syncopal episode may occur after a sudden unpleasant sight, smell, or painful stimulus. It is often accompanied by nausea and vomiting and may occur after physical exertion.

Orthostatic hypotension is another cause of syncope. It may be suspected when syncope occurs suddenly upon standing, in the presence of autonomic neuropathy or parkinsonism, or suddenly after physical exertion.

Symptoms and Diagnosis of Syncope

Clinical signs associated with a syncopal episode are important and may be significant for diagnosis (6). Syncope is a temporary loss of consciousness characterized by loss of postural control. Presyncope is a group of various symptoms that may occur before a syncopal episode, although these symptoms may also occur without subsequent syncope. Presyncope usually lasts only a few seconds. Patients may describe it as a sensation of almost fainting or losing consciousness.

Common prodromal symptoms are associated with impending syncope and presyncope, particularly in cases of neurally mediated reflex syncope. Symptoms may include dizziness, sensations of heat or cold, sweating, palpitations, nausea, blurred vision, impaired hearing such as indistinct sounds or ringing in the ears, and facial pallor, which is usually noticed by others.

In some cases, patients may experience no symptoms before a syncopal episode, particularly older patients who may not remember them. The absence of symptoms may be associated with cardiogenic syncope and a higher risk of injury from falling because the patient does not realize that loss of consciousness is imminent and therefore does not have time to lie down or lower the head.

Medical history and physical examination are the most specific and sensitive methods for evaluating syncope (7). The diagnosis can be established in 50–85% of patients based on medical history and physical examination. No other laboratory test is more effective (7). According to the 2007 American College of Emergency Physicians guidelines, medical history, physical examination, and a 12-lead ECG with a 12-lead rhythm strip are the main diagnostic tools (Class A recommendation) (8).

It is important to determine the circumstances surrounding the syncopal episode: what the patient was doing, the environment in which the episode occurred, and whether the patient was standing or lying down. Syncopal episodes may be triggered by fatigue, lack of sleep and food, warm and humid environments, alcohol consumption, pain, and negative emotions such as fear or distress.

The patient's activity before syncope may help determine the origin of the episode. Syncope may occur at rest, when changing body position, during or after physical exertion, or in specific situations such as shaving, coughing, or prolonged standing. Syncope occurring within 2 minutes of standing is usually caused by orthostatic hypotension (9).

It is important to establish whether the patient experienced syncope while standing, sitting, or lying down. Syncope occurring while the patient is sitting or lying down may be of cardiac origin (5). The patient should be asked whether consciousness was completely lost, whether the loss of consciousness occurred suddenly and lasted for a short period, whether consciousness was regained spontaneously, and whether control of body posture was lost during the episode. If the answers to these questions are positive, there is a high likelihood that the episode represents true syncope. If one or more answers are negative, other possible causes of loss of consciousness should be considered (5).

Approximately 70% of patients experience dizziness, weakness, or a sensation of impending loss of consciousness before a syncopal episode. Nausea and sweating may also occur during the prodromal period. However, if a patient experiences an aura, the episode is not syncope but a seizure. Patients who experience true syncope usually do not remember how they fell (5).

Symptoms before syncope last an average of 2.5 minutes in neurally mediated reflex syncope and 3 seconds in cardiac syncope (5). It is important to determine whether the patient experienced chest pain, shortness of breath, lower back pain, palpitations, severe headache, focal neurological symptoms, ataxia, diplopia, or dysarthria before syncope (5).

It is important to interview witnesses who observed the syncopal episode. This makes it possible to determine more accurately whether the patient lost consciousness, how long the loss of consciousness lasted, and whether the patient was confused afterward. If confusion persists for more than 30 seconds after the episode, it is likely that the event was a seizure (5). Concomitant diseases and medications, including antihypertensive and antiarrhythmic drugs, should also be evaluated.

After a syncopal episode, all vital signs should be assessed. Tachycardia may be caused by pulmonary embolism, hypovolemia, tachyarrhythmia, or acute coronary syndrome. Bradycardia may also develop as a result of acute coronary syndrome or conduction abnormalities. Therefore, a detailed examination of the cardiovascular system is essential. Auscultation may reveal heart murmurs characteristic of significant valvular defects. Distended jugular veins, hepatomegaly, and edema are typical findings in chronic heart failure.

Blood glucose levels should also be assessed. Hypoglycemia may mimic a syncopal episode. Following syncope, the patient may sustain injuries as a result of falling. A computed tomography scan of the brain may often be necessary.

If orthostatic hypotension is suspected, an orthostatic test should be performed. If systolic blood pressure decreases by more than 20 mm Hg and diastolic blood pressure decreases by more than 10 mm Hg upon standing, a diagnosis of orthostatic hypotension may be confirmed (5). If carotid sinus syncope is suspected, carotid sinus massage may be performed to assess whether symptoms characteristic of a syncopal episode occur.

Syncope Treatment

Understanding the etiology and cause of syncope allows the most effective treatment to be selected. Patient education on how to avoid syncope is very important. For example, if a patient is diagnosed with carotid sinus syncope, they should be advised not to wear tight collars, to use razors instead of electric shavers, and to maintain adequate and consistent fluid intake. In the future, these patients may require a pacemaker.

If a patient has orthostatic hypotension, they should be taught how to behave appropriately and advised never to get out of bed suddenly. First, they should raise their head, then sit up after a short period, and only then stand. Compression stockings may also be recommended.

Cardiogenic syncope, for example, in cases of arrhythmia, should be treated with antiarrhythmic medications or pacemakers.

How should patients respond when prodromal symptoms occur? These symptoms may manifest differently in each patient, but a rapid response is necessary if the patient reports feeling unwell. If an impending syncopal episode is suspected, the patient should immediately be laid down, the legs crossed, the head lowered, and something firm should be placed in their hands to squeeze. Prodromal symptoms are more common in younger patients, particularly in cases of neurally mediated reflex syncope.

In the event of syncope, the following actions should be taken:

• Protect the patient from possible environmental hazards, such as high places, water, or electrical wires, to prevent injury from falling.
• Elevate the patient's legs to improve venous return and restore blood flow to the brain.
• Assess vital signs: pulse, blood pressure, and respiration.
• Assess other signs, such as skin color and the presence of convulsions, as these may help establish the diagnosis.
• Avoid attempting to lift the patient until consciousness has been regained. Trying to lift the patient may provoke another syncopal episode.

Prognosis

The prognosis of patients experiencing syncopal episodes depends on the etiology of syncope and the presence of comorbidities. Patients diagnosed with cardiovascular diseases have a higher risk of sudden death and mortality compared with patients whose syncope is of non-cardiogenic origin.

It has been estimated that the 5-year mortality rate in the cardiovascular disease group exceeds 50%, with 30% of patients dying within the first year. The main problem in determining prognosis is that patients often do not seek medical attention after a syncopal episode, leaving the condition undiagnosed.

Publication "Internistas" No. 10, 2019.

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