Differential Diagnosis for Supraventricular Tachycardia (SVT)

Single Most Likely Diagnosis

• Atrioventricular Nodal Reentrant Tachycardia (AVNRT): This is the most common cause of SVT, accounting for approximately 60% of cases. It occurs when there is an abnormal electrical pathway in the atrioventricular node, leading to a reentrant circuit that causes the heart to beat too quickly.

Other Likely Diagnoses

• Atrioventricular Reentrant Tachycardia (AVRT): This includes orthodromic AVRT, which accounts for about 30% of SVT cases. It involves an accessory electrical pathway between the atria and ventricles, leading to a reentrant circuit.
• Atrial Flutter: Although not always presenting as a typical SVT, atrial flutter can sometimes be mistaken for SVT due to its rapid ventricular response. It is characterized by a rapid, regular atrial rhythm.
• Sinus Tachycardia: While not a pathological tachycardia per se, sinus tachycardia can present similarly to SVT and is a common finding in various conditions such as anxiety, dehydration, or thyrotoxicosis.

Do Not Miss Diagnoses

• Wolff-Parkinson-White (WPW) Syndrome: A condition characterized by an accessory electrical pathway in the heart that can cause SVT. It is crucial to identify because it can lead to life-threatening arrhythmias if not properly managed.
• Thyroid Storm: Hyperthyroidism can cause SVT, and thyroid storm is a life-threatening complication of untreated or undertreated hyperthyroidism.
• Cardiac Tamponade: Although not directly causing SVT, cardiac tamponade can lead to a clinical presentation that might initially be confused with SVT due to the rapid heart rate associated with decreased cardiac output.
• Pulmonary Embolism: Can cause tachycardia that might be mistaken for SVT, and is a critical diagnosis not to miss due to its high mortality if untreated.

Rare Diagnoses

• Junctional Tachycardia: A rare cause of SVT originating from the atrioventricular junction.
• Idiopathic Left Ventricular Tachycardia: A rare form of ventricular tachycardia that can sometimes be confused with SVT due to its relatively narrow QRS complex.
• Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT): Although primarily a ventricular tachycardia, it can present with supraventricular features and is a rare but important diagnosis due to its potential for sudden cardiac death.