What are the complications and management options for a patient with supraventricular tachycardia (SVT)?

Complications of Supraventricular Tachycardia

Untreated SVT can lead to heart failure, pulmonary edema, myocardial ischemia from sustained elevated heart rates, and in patients with congenital heart disease, carries increased risk of stroke and sudden cardiac death. 1

Hemodynamic Complications

• Heart failure develops from prolonged tachycardia-induced cardiomyopathy, occurring in approximately 1% of patients with persistent SVT 1, 2
• Pulmonary edema results from acute left ventricular dysfunction secondary to sustained rapid ventricular rates 1
• Myocardial ischemia occurs due to increased myocardial oxygen demand and decreased coronary perfusion time during tachycardia 1
• Hemodynamic instability manifests as hypotension, syncope, or altered consciousness requiring immediate intervention 1, 3

Thromboembolic Complications

• Stroke risk is elevated in adults with congenital heart disease who develop SVT 1
• Sudden cardiac death risk increases in patients with structural heart disease and untreated SVT 1

Pre-excitation Specific Complications

• Ventricular fibrillation can occur when atrial fibrillation develops in patients with accessory pathways (Wolff-Parkinson-White syndrome) that have short refractory periods, allowing rapid pre-excited conduction to the ventricles 1
• This represents a life-threatening emergency requiring immediate synchronized cardioversion 1

Iatrogenic Complications

Adenosine-Related

• Atrial fibrillation precipitation occurs in approximately 30% of patients, which may conduct rapidly in pre-excitation syndromes and potentially trigger ventricular fibrillation 1
• Minor side effects (flushing, chest discomfort, dyspnea) occur in 30% but last less than 1 minute 1
• Post-conversion arrhythmias: atrial or ventricular premature complexes immediately after conversion may reinitiate tachycardia 1, 4

Antiarrhythmic Drug Complications

• Proarrhythmic effects from flecainide occur in 4% of supraventricular arrhythmia patients, with 7 of 9 events being exacerbations of SVT (longer duration, more rapid rate, harder to reverse) 5
• Two ventricular arrhythmias occurred in patients with paroxysmal atrial fibrillation and coronary artery disease, including one fatal VT/VF 5
• Wide complex tachycardia and ventricular fibrillation have been reported in chronic atrial fibrillation patients with high ventricular rates during exercise 5

AV Nodal Blocker Complications

• Accelerated ventricular rate occurs when verapamil, diltiazem, or beta-blockers are given to patients with pre-excitation, as these agents block the AV node but not the accessory pathway, potentially causing life-threatening rapid ventricular rates during atrial fibrillation 4

Management to Prevent Complications

Acute Management Algorithm

For hemodynamically unstable patients (hypotension, syncope, myocardial ischemia, severe heart failure):

• Perform immediate synchronized cardioversion without attempting vagal maneuvers or adenosine 1, 4
• Have defibrillation capability immediately available 1

For hemodynamically stable patients:

1. First-line: Vagal maneuvers (modified Valsalva with patient supine for 10-30 seconds at 30-40 mmHg, or carotid massage for 5-10 seconds after confirming no bruit) - 27.7% success rate 1, 4, 2
2. Second-line: Adenosine IV (90-95% effective) with cardioversion equipment immediately available 1, 4, 2
3. Third-line: IV calcium channel blockers (diltiazem or verapamil) or beta-blockers for narrow-QRS tachycardias 1, 4
4. Last resort: Synchronized cardioversion if pharmacotherapy fails 1

Critical Pitfall Avoidance

• Always confirm the diagnosis before treatment - distinguish SVT from ventricular tachycardia, as misdiagnosis can be fatal 4
• Never use AV nodal blockers in pre-excitation - verapamil, diltiazem, and beta-blockers are absolutely contraindicated in patients with accessory pathways and atrial fibrillation 4
• Monitor post-conversion closely - premature complexes after cardioversion may trigger recurrence, requiring antiarrhythmic drugs to prevent reinitiation 1, 4

Special Populations

Pre-excited atrial fibrillation:

• Synchronized cardioversion for unstable patients 1
• Ibutilide or IV procainamide for stable patients (never AV nodal blockers) 1

Adults with congenital heart disease:

• Higher risk of heart failure, stroke, and sudden death requires aggressive rhythm control 1
• Early cardiology referral mandatory 1

Long-Term Complication Prevention

• Catheter ablation is first-line therapy for recurrent symptomatic SVT with success rates of 94.3-98.5%, preventing tachycardia-mediated cardiomyopathy 2, 6
• Oral beta-blockers, diltiazem, or verapamil reduce episode frequency in patients without pre-excitation 4
• All patients treated for SVT require cardiology referral for risk stratification and definitive management planning 6