Internal Medicine

P1: SBT

0521779407-05 CUNY1086/Karliner 0 521 77940 7 June 4, 2007 20:49

212 AV-Nodal Reentrant Tachycardia

tests

■Basic Tests

➣12-lead ECG:

➣Narrow QRS tachycardia unless pre-existing conduction defect

or rate-related aberrant ventricular conduction. Commonly at

180–200 bpm (range 150–250 bpm).

➣Typical AVNRT (Slow-Fast): retrograde P wave buried in the QRS

or in the S wave (short RP tachycardia). Begins with an APC with

a long PR interval (antegrade conduction down slow pathway).

Generally not initiated with a VPC. Usually terminates with a

retrograde P wave (86%).

➣Atypical AVNRT (Fast-Slow): retrograde P wave before the next

QRS complex (thus, long RP tachycardia).

■Specific Diagnostic Test

➣Electrophysiology study to confirm AVNRT (usually performed

in conjunction with RF ablation).

differential diagnosis

■Sinus tachycardia, atrial flutter, AV re-entry tachycardia, and atrial

tachycardia. Carotid sinus massage or adenosine IV: terminates

AVNRT, AVRT (bypass tracts) and AT (56%) but increases AV block

in atrial flutter and in AT, thus enabling better identification of p

waves. Diagnostic electrophysiology study often required.

management

What to Do First

■Vital signs to assess hemodynamic response; 12 lead ECG to assess

acute myocardial ischemia, infarction.

General Measures

■Avoid caffeine and alcohol if correlated with SVT occurrence

specific therapy

Restore NSR

Acute

■Restoration of NSR when a rapid ventricular response results in

hypotension, pulmonary edema, or ischemia. Vagal maneuvers

(carotid sinus massage, Valsalva) followed by IV adenosine.

Chronic

■For frequent occurrence, beta blockers or calcium channel blockers

(verapamil, diltiazem), or digoxin PO for chronic suppression. Class

I and III antiarrhythmic agents often not required.