Supraventricular Tachycardia Management

Introduction to SVT

Catheter ablation is the recommended first-line treatment for recurrent, symptomatic SVTs, including AVNRT and AVRT, due to its high success rate (>95%) and low complication rate, according to the American Heart Association 1
The mechanism of AVNRT involves reentry within the AV node using dual AV nodal physiology, while AVRT involves reentry using an accessory pathway and the normal conduction system 2

Typical AVNRT is characterized by a narrow QRS complex, heart rate of 180-200 bpm, and P waves hidden within or immediately after the QRS complex, with a short RP interval, as stated by the American College of Cardiology 1
Atypical AVNRT is characterized by retrograde P waves with a long RP interval and negative P waves in inferior leads, according to the American Heart Association 3
Orthodromic AVRT is characterized by a narrow QRS complex, P wave visible in the ST segment, and an RP interval longer than in typical AVNRT, as noted by the American College of Cardiology 2
Antidromic AVRT is characterized by a wide QRS complex with LBBB morphology and a pre-excitation pattern during tachycardia, as stated by the American Heart Association 2

The following ECG characteristics are suggestive of specific arrhythmias:

Arrhythmia	ECG Characteristics
AVNRT	Narrow QRS, hidden or retrograde P waves, short RP interval (RP <90 ms)
AVRT	Narrow QRS, hidden or retrograde P waves, longer RP interval (RP >90 ms)
VT	Wide QRS, lack of R-S complexes in leads V1-V6, R-S interval >100 ms in any precordial lead, AV dissociation, or QRS concordance

Synchronized cardioversion is the first-line treatment for SVT, as recommended by the American Heart Association 1
Vagal maneuvers, such as the Valsalva maneuver and carotid sinus massage, are recommended as a Class I treatment, with success rates varying by mechanism, according to the American College of Cardiology 4
Adenosine is recommended as a Class I treatment if vagal maneuvers fail, with caution in patients with severe asthma or high-grade AV block, as stated by the American Heart Association 1
IV beta-blockers, diltiazem, or verapamil are recommended as a Class IIa treatment for rate control and potential conversion, according to the American College of Cardiology 1
IV amiodarone is recommended as a Class IIb treatment when other therapies fail, as stated by the American Heart Association 1
Vagal maneuvers are recommended as first-line therapy for acute termination of SVT, followed by adenosine if vagal maneuvers fail, and beta-blockers and non-dihydropyridine calcium channel blockers are recommended as first-line pharmacologic therapy for SVT 3, 5

Oral verapamil or diltiazem are recommended as a Class I treatment for AVNRT, according to the American College of Cardiology 1
Oral beta-blockers are recommended as a Class I treatment for AVNRT, as stated by the American Heart Association 1
Flecainide or propafenone are recommended as a Class IIa treatment for patients without structural heart disease, according to the American College of Cardiology 1
Catheter ablation is recommended as a Class I treatment, with a success rate >95% for AVNRT and AVRT, and a low complication rate, as stated by the American Heart Association 1
Electrophysiology study and catheter ablation should be considered for recurrent symptomatic episodes, with high effectiveness rates and low complication rates 5

Patients with pre-excitation syndromes should avoid AV nodal blocking agents during AF, as they can accelerate conduction through the accessory pathway, according to the American College of Cardiology 2
Persistent SVT can lead to tachycardia-mediated cardiomyopathy, and continuous cardiac monitoring is essential to detect intermittent arrhythmias, as stated by the American Heart Association 2
Patients with chest discomfort who have a normal or unchanged ECG and no elevations of cardiac biomarkers still require careful evaluation, as recommended by the American College of Cardiology/American Heart Association (ACC/AHA) guidelines 6
Age >75 years is an independent risk factor for adverse outcomes in patients with tachycardia 6
Serial ECGs should be performed at 15-30 minute intervals if the patient remains symptomatic, and cardiac biomarkers should be measured in all patients with chest discomfort and repeated at 8-12 hours after symptom onset 6
The ACC/AHA guidelines recommend observation for 6-12 hours (may extend to 24 hours), with serial cardiac biomarkers and ECGs performed during observation, and functional cardiac testing (e.g., stress testing) after the observation period 6

Junctional rhythms can be classified into three types:

Type	Heart Rate (bpm)	Characteristics
Junctional Escape Rhythm	40-60	Narrow QRS, absent or retrograde P waves, AV dissociation
Nonparoxysmal Junctional Tachycardia	70-120	Narrow QRS, 1:1 AV association, often indicates underlying pathology
Focal Junctional Tachycardia	110-250	Narrow QRS, retrograde P waves, often requires treatment

Management of junctional rhythm depends on hemodynamic stability and underlying cause, with asymptomatic patients with adequate heart rate possibly not requiring immediate treatment 1
Failing to recognize that SVT persisting for weeks to months can lead to tachycardia-mediated cardiomyopathy, and high post-procedural SVE burden is associated with increased risk of atrial fibrillation (AF) recurrence 5