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Syncope (Fainting)

Syncope is a brief loss of consciousness caused by a sudden drop in blood flow to the brain, with causes ranging from harmless fainting reflexes to serious heart rhythm problems.

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Syncope — the medical term for fainting — is a sudden, brief loss of consciousness caused by a temporary drop in blood flow to the brain, followed by complete recovery. It is extremely common: a large share of people faint at least once in their lives. Most episodes are benign, but syncope can occasionally be the first sign of a serious heart problem, so the cause should always be sorted out rather than assumed. Fainting is also responsible for a meaningful share of emergency visits and fall-related injuries in older adults. Causes: Syncope falls into three broad groups:
  • Reflex (vasovagal) syncope: The most common type. A nervous-system reflex abruptly slows the heart and drops blood pressure, triggered by prolonged standing, heat, pain, emotional distress, or even the sight of blood. In Florida's heat and humidity, dehydration is a frequent contributor.
  • Orthostatic syncope: Blood pressure falls on standing because of dehydration, blood loss, or medications such as blood pressure drugs, diuretics, and some antidepressants.
  • Cardiac syncope: The most concerning group. Rhythm problems — very fast rhythms such as supraventricular tachycardia or very slow rhythms — and structural problems such as severe valvular heart disease can abruptly cut the heart's output.
Not every spell that looks like fainting is syncope. Seizures cause loss of consciousness through abnormal brain activity rather than low blood flow, and vertigo causes spinning dizziness without blacking out. Distinguishing among these changes the entire work-up. Symptoms and Warning Signs: Reflex fainting usually announces itself: lightheadedness, warmth, nausea, sweating, "graying out" or tunnel vision, and muffled hearing in the seconds before consciousness is lost. Bystanders may notice pallor. Recovery is rapid once the person is lying flat. Fainting with no warning at all, or during physical exertion, points toward a cardiac cause and is treated far more seriously. Diagnosis: The most valuable tools are a careful history — what you were doing, what you felt beforehand, how quickly you recovered — a physical examination, blood pressure measurements lying and standing, and an electrocardiogram. Depending on the findings, your physician may add blood tests, an echocardiogram, a wearable heart monitor to catch intermittent rhythm problems, or a tilt-table test to reproduce reflex fainting under controlled conditions. Routine brain imaging is usually unnecessary unless the story suggests a seizure or head injury, because true syncope is a circulation problem rather than a brain problem. Treatment: Treatment is aimed at the underlying cause:
  • Reflex syncope: Staying well hydrated, recognizing warning symptoms, and sitting or lying down promptly. Physical counter-maneuvers — crossing the legs and tensing the muscles — can abort an episode.
  • Orthostatic causes: Reviewing and adjusting medications, increasing fluid and salt intake when appropriate, and rising slowly from sitting or lying positions.
  • Cardiac causes: Treating the specific rhythm or valve problem, which may involve medication changes, a pacemaker for slow rhythms, or valve intervention.
When to Seek Immediate Care: Call 911 or seek emergency care for fainting during exercise, fainting preceded by chest pain or a racing heartbeat, episodes causing significant injury, multiple episodes in a short period, or fainting in someone with known heart disease or a family history of sudden cardiac death. Because the causes range from trivial to life-threatening, every first episode of true syncope deserves a medical evaluation, and a witness's description of the episode is often the single most useful piece of information you can bring. The internal-medicine team at Zimmer Medical Group performs the initial work-up in the office and refers to cardiology or neurology when the findings call for it.

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