From the Guidelines
Syncope is a temporary loss of consciousness due to insufficient blood flow to the brain, and immediate medical attention is necessary after the first episode, especially if it occurs suddenly without warning, is associated with exercise, or happens with chest pain or palpitations. If you experience syncope, you should lie down flat with legs elevated to restore blood flow to the brain. While waiting for medical help, stay hydrated and avoid standing up quickly. The initial evaluation typically includes an electrocardiogram (ECG), orthostatic vital signs, and possibly an echocardiogram to rule out cardiac causes, as recommended by the 2017 ACC/AHA/HRS guideline for the evaluation and management of patients with syncope 1.
Common causes of syncope include:
- Vasovagal reactions (triggered by pain, fear, or standing for long periods)
- Orthostatic hypotension (blood pressure drop when standing)
- Cardiac arrhythmias
- Structural heart problems Treatment depends on the underlying cause - vasovagal syncope may require only lifestyle modifications like increased fluid intake and avoiding triggers, while cardiac causes might need medication (such as beta-blockers like metoprolol 25-100mg daily) or procedures like pacemaker implantation, as suggested by the 2017 ACC/AHA/HRS guideline 1.
It is essential to identify patients with underlying heart disease, myocardial ischemia, Wolff-Parkinson-White syndrome, and potentially life-threatening diseases such as long-QT syndrome (LQTS), Brugada syndrome, and catecholaminergic polymorphic ventricular tachycardia, as these conditions can increase the risk of mortality, as stated in the 2006 AHA/ACCF scientific statement on the evaluation of syncope 1. Syncope occurs because insufficient blood flow to the brain causes temporary cerebral hypoperfusion, leading to loss of consciousness as a protective mechanism to restore horizontal positioning and cerebral blood flow.
Other potential causes of syncope, as outlined in the 2017 ACC/AHA/HRS guideline, include:
- Infectious causes, such as myocarditis or Lyme disease
- Neuromuscular causes, such as myotonic dystrophy or Friedreich ataxia
- Anatomic causes, such as cardiac tumors or prosthetic valve thrombosis
- Endocrine causes, such as carcinoid syndrome or pheochromocytoma
- Hematologic causes, such as beta thalassemia major
- Neurological disorders, such as seizure-induced bradycardia/hypotension or migraine, as discussed in the 2017 ACC/AHA/HRS guideline 1.
In summary, syncope is a complex condition that requires prompt medical attention to determine the underlying cause and provide appropriate treatment, with the goal of improving the patient's quality of life and preventing injury or mortality, as emphasized by the 2017 ACC/AHA/HRS guideline 1 and the 2006 AHA/ACCF scientific statement 1.
From the Research
Definition and Classification of Syncope
- Syncope is an abrupt, transient, and complete loss of consciousness associated with an inability to maintain postural tone; recovery is rapid and spontaneous 2.
- The primary classifications of syncope are cardiac, reflex (neurogenic), and orthostatic 2.
Diagnosis and Evaluation of Syncope
- The first step of syncope diagnostic assessment is to identify patients with cardiac syncope, and once established, these patients must receive the adequate mechanism-specific treatment 3.
- Evaluation focuses on history, physical examination (including orthostatic blood pressure measurements), and electrocardiographic results 2.
- A thorough history and physical examination including orthostatic assessment are crucial for making the diagnosis 4.
- The initial patient evaluation, particularly a detailed medical history, is the key to identifying the most likely diagnosis 5.
Treatment and Management of Syncope
- Established mechanism-specific treatment strategies include withdrawal of hypotensive drugs, applying fludrocortisone and midodrine for the hypotensive phenotype and cardiac pacing in the bradycardic phenotype 3.
- The results of recent trials indicate that 'mechanism-specific therapy' is highly effective in preventing recurrences 3.
- Pharmacologic agents such as atenolol, midodrine, and paroxetine have demonstrated efficacy in the treatment of vasovagal syncope in at least 1 prospective, randomized, placebo-controlled clinical trial 6.
- Other therapies commonly used in treating syncope include increased salt and fluid intake and fludrocortisone 6.
Prognosis and Risk Stratification
- The prognosis of patients with reflex and orthostatic syncope is good; cardiac syncope is more likely to be associated with adverse outcomes 2.
- Risk stratification tools, such as the Canadian Syncope Risk Score, may be beneficial in informing decisions regarding hospital admission 2.
- Short-term risk assessment should be performed to determine the need for admission 4.