Arrhythmias Post Tetralogy of Fallot Surgical Repair Joseph Atallah, MD CM, SM Division of Pediatric Cardiology Section of Electrophysiology

Outline Why is there a risk of arrhythmias Arrhythmia classification Recognition Treatment Longterm outcomes Summary

Arrhythmias … Why?

Arrhythmias … Why? Incidence Risk factors Up to 36% of post-op TOF patients will experience some arrhythmic event, mostly insignificant and brief Majority resolve within 48 hrs post-op Risk factors Young age at surgery Longer bypass and aortic cross-clamp time Complexity of repair

Arrhythmia Classification SLOW FAST .

Arrhythmia Classification SLOW Sinus bradycardia Heart block FAST Sinus tachycardia Atrial tachycardia Supraventricular tachycardia Junctional tachycardia Ventricular tachycardia

Arrhythmia Classification SLOW Sinus bradycardia Intrinsic: sinus node dysfunction (rare) Extrinsic: medications (sedation …), increased ICP … Heart block Results from damage to the AVN, His bundle or bundle branches FAST Sinus tachycardia Common: medications (inotropes, sedation …), hemodynamic stress … Atrial tachycardia Rare Supraventricular tachycardia ORT or AVNRT or atrial flutter Junctional tachycardia Relatively common: multifactorial Ventricular tachycardia Rare, more of an issue 10-20-30 years post-op

Definition and Recognition

Heart Block SLOW Heart block Incidence is 1-3% of all pediatric open heart surgeries Often recognized in the operating room However, may be acute or gradual in onset in first few days post-op Highest risk surgeries LVOTO surgery VSD Closure TOF ccTGA Definition: more P waves than QRS complexes (more As than Vs)

Heart Block SLOW Heart block 2nd degree (partial) Not every atrial beat is conducted to the ventricle = ventricular rate is slower than the atrial rate (2:1, 3:1 …) 3rd degree (complete) No (zero) atrial beat is conducted to the ventricle Extreme: HR (VR) = 0 … flat line … bad news … please help! Most common: ventricular escape rhythm at a certain rate Inadequate slow vs. acceptable rate Narrow vs. wide complex QRS

Heart Block QRS QRS QRS P ?T P P P 2 1

Heart Block QRS P P P

Heart Block Narrow QRS Wide QRS

Heart Block

Arrhythmia Recognition FAST Supraventricular Tachycardia Usual rate between 180 and 280 bpm Sudden onset and termination Minimal HR variation during SVT Junctional Tachycardia Usual rate between 160 and 230 bpm Gradual onset and termination HR variation during JET

Junctional Tachycardia Onset within the first 24 hrs post-op Due to stress injury around the AV node and the His bundle Inappropriate accelerated rhythm with the same QRS morphology as sinus rhythm Often with more Vs then As = VA dissociation Most common after TOF repair

Junctional Tachycardia QRS V V V V P A A A

Junctional Tachycardia

Junctional Tachycardia V V A V A V A V V A

Treatment

SLOW Weaning sedation Warming up Medications Pacing Atropine Isoproterenol Epinephrine Pacing Atrial, ventricular or both

FAST Optimize hemodynamics Correcting electrolyte and acid-base disturbances Weaning certain inotropes (e.g. Epi, Dexmetomedine) Optimizing sedation Cooling Anti-arrhythmic drugs Procainamide Amiodarone Esmolol Overdrive atrial pacing

Outcomes

Long-term Outcomes Heart Block Supraventricular tachycardia At least 60% resolve in the first month post-op ~90% of those will occur in the first 10 days post-op Remaining require a permanent pacemaker implantation despite the possibility of late recovery of AV conduction Supraventricular tachycardia May resolve Medical therapy or ablation Junctional tachycardia May be very resilient and life threatening Usually resolves within 2 days but may last 8 days

Summary Most common arrhythmias post surgical repair of TOF Heart block Junctional tachycardia A simple analytical approach to recognition Multiple treatment options, ultimately: Pacing for heart block AAD for junctional tachycardia Long-term outcomes: Heart block: 30-40% will require pacing ST and JT usually resolve early on