Diagnostic Considerations
The differential diagnosis for a narrow complex tachycardia is extensive, and the term supraventricular tachycardia (SVT) is nonspecific. Differentiation of automatic versus reentrant mechanisms may be determined by the presence of a warm-up or cool-down period at onset and termination and by the response to vagal maneuvers or adenosine.
Go to Atrial Tachycardia and Multifocal Atrial Tachycardia for information on these topics.
A right-sided atrial ectopic tachycardia (AET) focus in the presence of tachycardia-induced cardiomyopathy must be differentiated from idiopathic dilated cardiomyopathy with a secondary compensatory sinus tachycardia; the degree of dysfunction and heart rate are higher and second-degree atrioventricular (AV) block is more common in patients with atrial ectopic tachycardia.
Atrial ectopic tachycardia must also be differentiated from atypical AV node reentry, permanent junctional reciprocating tachycardia, and inappropriate sinus tachycardia. The former two usually respond to adenosine with abrupt termination.
Inappropriate sinus tachycardia typically occurs in association with exercise intolerance and a mild elevation of a sinus rate, more commonly in females. Approximately half the patients with atrial ectopic tachycardia demonstrate transient atrial slowing with adenosine, whereas the others demonstrate only transient AV block. Aberrantly conducting atrial ectopic tachycardia must be differentiated from ventricular tachycardia (VT).
In atrial ectopic tachycardia, a conduction delay from atrium to ventricle often occurs. Most patients demonstrate first-degree AV block and some show second-degree block.
Atrial flutter is another abnormal rhythm in the differential diagnosis of atrial ectopic tachycardia.
