Arrhythmias Post Tetralogy of Fallot Surgical Repair

Joseph Atallah, MD CM, SMDivision 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– 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

PQRS

?T PQRS

P PQRS

2 1

Heart Block

P P P

QRS

Heart Block

Narrow QRSWide 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

P

V

A

V

A

V V

A

Junctional Tachycardia

Junctional TachycardiaV V V V VA A A AVA

Treatment

SLOW

• Weaning sedation• Warming up• Medications– 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– 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