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Differential Diagnosis & Pitfalls

• Supraventricular tachycardia – Various supraventricular arrhythmias (eg, atrial fibrillation, atrial flutter, atrial tachycardia, atrioventricular nodal reentrant tachycardia, or atrioventricular reentrant tachycardia) may present with dizziness, lightheadedness, palpitations, and (less commonly) syncope. If there is aberrant ventricular conduction, it will produce a wide QRS complex tachycardia that may be difficult to distinguish from ventricular tachycardia, although the QRS complexes are generally monomorphic.
• Wolff-Parkinson-White syndrome – Patients with an accessory atrioventricular (AV) conduction pathway can present with dizziness, lightheadedness, palpitations, or syncope due to atrioventricular reentrant tachycardia as well as atrial fibrillation or atrial flutter with rapid conduction down the accessory pathway, which can produce extremely rapid ventricular rates that can degenerate to ventricular fibrillation. Delta waves may be present on a baseline ECG.
• Brugada syndrome – Hereditary channelopathy resulting in recurrent syncope or sudden cardiac arrest. Baseline ECG shows characteristic ST elevation and T-wave abnormality in the right precordial leads.
• Catecholaminergic polymorphic ventricular tachycardia – Voltage-gated ion channel mutation that causes polymorphic ventricular tachycardia resulting in dizziness, syncope, or sudden cardiac arrest triggered by exercise or emotional stress. The baseline ECG may be normal. Arrhythmias may be seen on treadmill testing.
• Sinus node dysfunction – Prolonged sinus pauses or sinus exit block can cause dizziness, lightheadedness, and/or syncope. The arrhythmia may be sporadic and can be missed on a screening ECG. Longer term ECG monitoring may be necessary to make the diagnosis.
• Atrioventricular nodal block – Third-degree (complete) AV block produces severe bradycardia that can present as dizziness or syncope. It may be intermittent. ECG monitoring or invasive electrophysiologic testing may be necessary to make the diagnosis.
• Neurocardiogenic syncope – The most common cause of syncope. There may be clues in the history, although structural heart disease and arrhythmia must be excluded. Tilt testing may also be helpful to establish the diagnosis.
• Seizures – Prodromal symptoms (aura), tongue biting, urinary incontinence, tremors, convulsions, and postictal symptoms (eg, fatigue, confusion) are often present. An electroencephalogram (EEG) may be abnormal.
• Structural heart disease – Valvular heart disease or severe cardiomyopathy may cause syncope, particularly during exertion, although other symptoms such as dyspnea, edema, orthopnea, and/or angina usually predominate.

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