Chapter 35

Supraventricular Tachycardia

Glenn N. Levine, MD, FACC, FAHA

1. What does the term supraventricular tachycardia (SVT) mean?

    By strict definition, a supraventricular tachycardia is any tachycardia whose genesis is not in the ventricles. Thus, the term can encompass atrial fibrillation and flutter, atrial tachycardia and multifocal atrial tachycardia, and reentrant tachycardias. Others will use the terms SVT or paroxysmal SVT to more specifically refer to the reentrant tachycardias of atrioventricular (AV) nodal reentrant tachycardia (AVNRT) and AV reentrant tachycardia (AVRT), as well as atrial tachycardia and several uncommon supraventricular arrhythmias. For the purposes of this chapter, we will use the term SVT to refer to any tachycardia not caused by ventricular tachycardia, and the term paroxysmal SVT to refer to tachycardias resulting from AVNRT, AVRT, and atrial tachycardia (although the reader should recognize that this is somewhat arbitrary and not universally accepted, and we will not discuss in detail other rare causes of paroxysmal SVT).

2. What is the most common cause of paroxysmal SVT?

    AVNRT accounts for 60% to 70% of paroxysmal SVTs, followed by AVRT.

3. What factors are part of the generic workup for supraventricular tachycardia?

 History, including type and duration of symptoms (palpitations, lightheadedness, chest pains, dyspnea, presyncope, precipitating factors)

 Questions regarding the intake of alcohol, caffeine, and illicit drugs

 Cardiac history (myocardial infarction, valvular disease, cardiac surgery)

 Physical examination (although often unrevealing)

 12-lead electrocardiogram (ECG) (looking for signs of chamber enlargement, preexcitation, etc.)

 Echocardiogram (often unrevealing because paroxysmal SVT can occur in the absence of structural heart disease, although atrial arrhythmias will often occur in the setting of dilated atria)

 Laboratory tests (electrolyte abnormalities, hyperthyroidism)

4. What are the causes of narrow complex regular tachycardias (regular referring to fixed R-R intervals—the time or distance between QRS complexes)?

    ECGs of the more common SVTs that cause narrow complex regular tachycardias are shown in Figure 35-1.

Figure 35-1 SVTs that cause a narrow complex regular tachycardia. A, Sinus tachycardia. Normal appearing P waves (arrows) are present before each QRS complex. B, Atrial tachycardia. Abnormal, inverted P waves (arrows) are present before each QRS complex. C, Atrial flutter. Flutter waves (arrows) are present. There is 2:1 conduction. D, Atrioventricular nodal reentrant tachycardia (AVNRT). No P waves are present before the QRS complexes. Retrograde, inverted P waves (arrows) are visible immediately after the QRS complexes. E, Atrioventricular reentrant tachycardia (AVRT). No P waves are present before the QRS complexes. Although retrograde P waves are sometimes seen in the ST-T segment with AVRT, none are visible in this particular rhythm strip.

 Sinus tachycardia (not really an arrhythmia, but still in the differential diagnosis)

 Atrial flutter

 Atrial tachycardia

 AVNRT

 AVRT

 Rare causes of narrow complex QRS, especially in adults, that are often difficult to diagnose and are more suited for discussion at the cardiology fellow or attending level, include sinoatrial (SA) nodal reentrant tachycardia and focal junctional tachycardia.

5. What are the causes of narrow complex irregular tachycardias (tachycardias with irregular R-R intervals)?

    ECGs of SVTs that cause narrow complex irregular tachycardias are shown in Figure 35-2.

Figure 35-2 Supraventricular tachycardia (SVTs) that cause a narrow complex irregular tachycardia. A, Multifocal atrial tachycardia (MAT). P waves of differing morphologies (arrows) are present before the QRS complexes. B, Atrial flutter with variable block. Flutter waves are intermittently visible between the QRS complexes. C, Atrial fibrillation. No organized atrial activity is present.

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