Can catheter ablation for supraventricular tachycardia and atrial fibrillation cause bradycardia in a patient with a normal baseline electrocardiogram, normal echocardiogram, normal renal function, and normal potassium levels?

Can Catheter Ablation for SVT and Atrial Fibrillation Cause Bradycardia?

Yes, catheter ablation for SVT and atrial fibrillation can cause bradycardia, though the risk varies dramatically by ablation type and is generally low for most procedures.

Risk by Ablation Type

AVNRT (Slow-Pathway) Ablation

• Complete AV block occurs in approximately 1% of slow-pathway ablation procedures for AVNRT, which may require permanent pacemaker implantation 1
• This 1% risk is substantially lower than the 8% risk associated with fast-pathway ablation approaches 1
• Pre-existing first-degree AV block does not significantly increase progression risk to complete heart block, though heightened vigilance is warranted 1
• The mechanism involves inadvertent injury to the compact AV node during energy delivery near the slow pathway region 2

Atrial Flutter (CTI) Ablation

• Bradycardia is not a typical complication of cavotricuspid isthmus ablation, which achieves >90% acute success with excellent safety 1
• When post-procedural bradycardia does occur after CTI ablation, it typically reflects previously masked sinus node dysfunction rather than direct procedural injury 1
• This unmasking phenomenon occurs because elimination of the flutter reveals underlying sick sinus syndrome that was previously obscured by the tachyarrhythmia 3

Atrial Fibrillation Ablation

• AF ablation itself rarely causes direct bradycardia through procedural injury 4
• The major complication rate for AF ablation is 5.2%, but bradycardia is not among the primary complications (which include tamponade, stroke, and pulmonary vein stenosis) 5, 4
• Post-ablation bradycardia more commonly results from unmasking of underlying sinus node dysfunction or tachy-brady syndrome 3, 6

Intentional AV Junction Ablation

• AV junction ablation deliberately creates complete AV block and requires permanent pacemaker implantation in 100% of cases 1
• This procedure achieves complete AV block in 70-95% of patients (typically ≥87%) with overall complication rates <2% 1
• Ventricular fibrillation and sudden death are rare but recognized complications, particularly when post-ablation pacing rates are inadequate 7
• Pacing at 90 bpm for 1-3 months post-ablation reduces VF risk compared to slower pacing rates ≤70 bpm (6% vs 0%, p<0.05) 7

Medication-Related Bradycardia Post-Ablation

• Antiarrhythmic drugs used after ablation independently cause bradycardia: sotalol, amiodarone, and dofetilide all have bradycardic effects 1
• Rate-control medications (beta-blockers, calcium-channel blockers) can exacerbate underlying bradycardic tendencies and require close monitoring 1, 3
• This is particularly relevant in patients with tachy-brady syndrome, where rate control for residual tachycardia may worsen bradycardic episodes 3

Clinical Context for Your Patient

In a patient with normal baseline EKG, normal echocardiogram, normal renal function, and normal potassium:

• The risk of procedure-induced bradycardia requiring pacemaker is approximately 1% for AVNRT ablation 1
• For atrial flutter or AF ablation, direct procedural bradycardia is rare; any bradycardia more likely represents unmasking of pre-existing sinus node dysfunction 1, 3
• The normal baseline EKG suggests no pre-existing conduction disease, which is reassuring 2
• Normal echocardiogram excludes structural heart disease that might increase risk 2

Key Pitfalls to Avoid

• Do not assume all post-ablation bradycardia is procedural injury—many cases represent unmasking of underlying sick sinus syndrome or tachy-brady syndrome 3, 6
• Recognize that bradycardia-tachycardia syndrome may emerge after successful ablation of the tachycardia component, requiring pacemaker for the bradycardia and potentially additional ablation or medications for recurrent tachycardia 3, 6
• Monitor for bradycardia-dependent ventricular arrhythmias in the immediate post-ablation period, particularly after AV junction ablation 7
• Avoid aggressive rate control in patients with suspected tachy-brady syndrome, as this may precipitate symptomatic bradycardia 3

Overall Risk Assessment

The overall complication rate for SVT ablation is very low (0.8%), with complete heart block being the most relevant bradycardic complication 5, 4. For your patient with normal baseline studies, the risk of clinically significant bradycardia is approximately 1% for AVNRT ablation and even lower for atrial flutter or AF ablation 1, 4.