Chapter 126. Supraventricular Tachyarrhythmias

1. What electrocardiographic findings help differentiate between the common supraventricular tachyarrhythmias (SVTs)?

2. What acute and chronic management strategies are indicated for various SVTs?

3. What comorbid conditions increase the risk of thromboembolic complications in patients with atrial fibrillation?

4. Which patients with atrial fibrillation deserve anticoagulation, and which of these patients need bridging anticoagulation until oral warfarin attains therapeutic international normalized ratio (INR)?

5. Which SVTs deserve electrophysiologic intervention over medical management?

Supraventricular tachyarrhythmias (SVTs) comprise an array of narrow-complex arrhythmias that originate above the ventricles and include both the most commonly encountered arrhythmia, atrial fibrillation (AF), and the uncommon ones, such as Wolfe-Parkinson-White (WPW) syndrome. This chapter describes in detail the common atrial arrhythmias encountered by hospitalists, and explains the uncommon arrhythmias that hospitalists should recognize and manage with cardiologist or electrophysiologist consultation or referral. The chapter will briefly describe arrhythmia mechanisms while focusing on arrhythmia diagnosis, management options in the acute setting, and long-term management strategies—all essential for a seamless transition beyond the inpatient setting.

Common presenting symptoms of SVTs include rapid palpitations, chest discomfort, dyspnea, presyncope, and syncope. Additionally, atrial fibrillation and atrial flutter may present with new stroke symptoms. Particularly in the elderly with atrial fibrillation, palpitations and chest discomfort are often absent and excessive fatigue is the predominant symptom.

When evaluating patients with a narrow-complex arrhythmia, the QRS complex is by definition less than 120 ms. The regularity of the RR intervals then helps reduce the numerous possibilities, as indicated in the SVT recognition algorithm (Figure 126-1). Only four possibilities exist if the RR intervals are irregular: (1) atrial fibrillation, (2) atrial flutter with variable atrioventricular (AV) node blockade, (3) atrial tachycardia with variable AV node blockade, and (4) multifocal atrial tachycardia (MAT).

More challenging to diagnose is the SVT with a regular RR interval. If, however, no P wave can be identified, this indicates the most common form of paroxysmal SVT: atrioventricular nodal reentrant tachycardia (AVnRT). The P wave in typical AVnRT is buried within the QRS complex. If the P wave is identified, then determine if there is more than one P wave for each conducted QRS. If so, then only atrial flutter or atrial tachycardia remain as possible diagnoses.

Finally, if only a 1-to-1 relationship between the P waves and QRS complexes exists, measuring the RP interval will further narrow the likely rhythms (Figure 126-2). The response of the rhythm to bedside vagal maneuvers or intravenous adenosine can be used to better differentiate the regular narrow-complex arrhythmias by transiently slowing the AV conduction and revealing the P waves, ...