Abstract
- 1.
In patients with biventricular hearts like ToF and IART, catheter ablation can be an excellent first option.
- 2.
If catheter ablation fails due to technical reasons (such as abnormal venous anatomy), a repeat attempt with appropriate preprocedure planning and a different approach should be considered.
- 3.
If multiple, technically adequate, catheter ablation attempts fail, drug therapy based on established guidelines should be considered.
Keywords
Atrial flutter, Catheter ablation, Electroanatomical mapping, Hemiazygous continuation of inferior vena cava, Tetralogy of Fallot
Case Synopsis
History
A 51-year-old male underwent primary repair of tetralogy of Fallot (ToF) in 1974 at the age of 9 years. The repair included a Dacron patch to close the ventricular septal defect and a pericardial patch in the right ventricular outflow tract. He remained well throughout childhood and early adult life with regular, but infrequent, outpatient follow-up. By the age of 48 he had developed progressive right ventricular dilatation with severe and increasing pulmonary regurgitation on serial echocardiography. He had no exercise-related symptoms and exercise tolerance was good (VO2 max 33 mL/kg/min). Coronary angiography was normal. The right ventricle measured 5.7 cm at the base on echocardiography but there was reasonable long axis function (tricuspid annular plane systolic excursion 18 mm). There was good left ventricular function with no branch pulmonary artery stenosis or other cardiac pathology.
The 12 lead ECG prior to surgery showed sinus rhythm with a broad right bundle branch block pattern with a QRS width of 160 ms and QRS axis of −80 degrees. A preprocedural MRI showed normal biventricular function with severe pulmonary regurgitation and no late gadolinium enhancement. He underwent elective pulmonary valve replacement (26 mm perimount bioprosthesis; Edwards Lifesciences, Irvine, Calif, USA) and a ring annuloplasty was carried out on the tricuspid valve. He made an excellent postoperative recovery ( Fig. 3.1 ).
A year after his procedure he described reduced exercise tolerance with shortness of breath. An echocardiogram showed minimal pulmonary and tricuspid valve regurgitation and normal right ventricular pressures. Left ventricular function was good but his right ventricle had remained dilated with reduced function postoperatively.
Electrocardiogram
A resting 12 lead ECG from the patient in sinus rhythm is shown below with typical features of previously repaired ToF.
Below is a second ECG from the patient with the patient experiencing his typical symptoms of shortness of breath but no palpitations.
He was commenced on Bisoprolol 2.5 mg and given his symptom burden; a decision was made to carry out a diagnostic electrophysiology study (EPS) with a plan to proceed to ablation.
Electrophysiology Study
When the patient attended for his EPS he was in his tachycardia from a symptomatic viewpoint and his 12 lead ECG shown was identical to his clinic ECG ( Fig. 3.2 ) suggesting one important macroreentrant circuit.
His antiarrhythmic medication had been stopped 5 days prior to the procedure but his oral anticoagulant (warfarin) was not interrupted with his international normalized ratio (INR) on the day of the procedure less than 2.5.
Femoral vein ultrasound confirmed a large left femoral vein and a small but patent right femoral vein.
A 7Fr and 8Fr sheath was placed in the right femoral vein percutaneously without complication. A 5Fr quadripolar electrophysiology catheter was advanced through the 8Fr sheath but did not cross the midline on abdominal fluoroscopy. The catheter was withdrawn. A 5Fr sheath was then inserted into the left femoral vein and a 0.035 mm wire advanced toward the heart. This took an unusual course parallel to the left of the spine. The sheath pressure was low suggesting a venous structure as opposed to inadvertent arterial puncture. A 5Fr multipurpose catheter was then advanced toward the heart and a hand angiogram demonstrated a left-sided inferior caval vein with hemiazygos continuation into left-sided superior caval vein (SCV) draining to the coronary sinus (CS). A formal venogram was then performed ( Figs. 3.3–3.8 ) which demonstrated a CS measuring 4.8 cm in diameter.
Once the anatomy had been confirmed, a fixed decapolar catheter was placed in a small side branch of the large coronary sinus as a reference catheter and using the CARTO system (Biosense Webster Inc., Diamond Bar, CA, USA) a local activation time map was created using the DecaNav multipolar mapping catheter (Biosense Webster Inc.).
Entrainment maneuvers confirmed a macroreentrant circuit with a cycle length of 270 ms around the cavotricuspid isthmus (CTI) encompassing a large area of the lateral wall of the right atrium (RA).
Ablation was performed over a wide area the lateral wall down onto the CTI area (there not being an inferior vena cava so defining a true isthmus end was difficult) and CS os using a ThermoCool SmartTouch catheter (Biosense Webster Inc.).
Despite this the tachycardia was not slowed or terminated and subsequently was remapped with identical results. The anomalous venous course hampered stability of the ablation catheter (particularly in reference to doubling back on to the CTI line) and despite further ablation, the tachycardia remained. At this point using extra sedation, the patient was externally electrically cardioverted with a single 200J shock restoring sinus rhythm.
The following day he was discharged home on his antiarrhythmics and warfarin. He was subsequently followed up again after 8 months having suffered a recurrence of his arrhythmia which on the surface ECG appeared identical to the previously identified arrhythmia.
Questions
- 1.
What are the common atrial arrhythmias encountered in postsurgical correction of ToF
- 2.
What are the common vascular anomalies encountered?
- 3.
What other options are there for this patient?
Consultant Opinion #1
- Elisabeth M.J.P. Mouws, MD
- Natasja M.S. de Groot, MD, PhD
Postoperative atrial arrhythmias and ablation strategies after total tetralogy of Fallot (ToF) correction
This case represents a patient with repaired ToF who developed postoperative atrial tachyarrhythmias approximately 4 decades after the initial repair. Three-dimensional electroanatomical mapping studies prior to ablative therapy revealed that atrial tachyarrhythmias in this patient population include intraatrial reentrant tachycardias (macroreentrant circuits around surgical scars, sutures, and so on), cavotricuspid isthmus–dependent atrial flutter, or focal atrial tachycardias (electrical activation originating from a small circumscriptive region from where it expands more or less centrifugally to the remainder of the atrium). The arrhythmogenic substrate of these atrial tachyarrhythmias is mainly located in the right atrium, near sites related to surgical incisions created at repair. Another frequently occurring tachyarrhythmia in patients with ToF is atrial fibrillation, which develops on average at the age of 44 years.
The incidence of late postoperative atrial tachyarrhythmias rises with time after surgical repair and they are the main cause of morbidity due to heart failure, stroke, and even sudden cardiac death. Effective therapy is therefore essential and ablative therapy may be a potentially curative treatment modality.
If ablation is not successful despite targeting the critical isthmus of the reentrant circuit it can be the result of insufficient lesion depth or persisting gaps in the linear lesion. The authors describe difficulty in acquiring a stable position of the ablation catheter due to the complex cardiovascular anatomy. For such a patient, a redo procedure guided with the magnetic navigation system with a floppy catheter to reach ‘the difficult spots’ may offer an alternative approach, although it may be complicated by insufficient contact force. Another option may be an ablation procedure using the superior caval vein approach.
In this case, particularly the venous anomaly in which there is no true inferior vena cava (IVC) isthmus and the inability for stable positioning of the catheter made the procedure challenging.
The authors describe the venous anomaly, which was confirmed by angiography, as the combination of a left-sided IVC with hemiazygos continuation into a left-sided superior vena cava (SVC) draining to the coronary sinus (CS). While this makes ablation difficult, we would recommend another attempt utilizing the approaches given above. If a second attempt (as described) also fails, we would recommend increasing or altering his medical therapy. Based on the recently published guidelines for management of arrhythmias in the ACHD population , we would attempt the use of sotalol (with cardioversion to convert to sinus rhythm after 48 h of sotalol), and, if that fails to maintain sinus rhythm, a trial of Dofetilide with appropriate precautions for both drugs as described in the literature.
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
