Case Synopsis

A 39-year-old man was referred to the congenital heart disease (CHD) arrhythmia service in 2015. He was known to have crisscross heart with situs solitus, atrioventricular (AV) concordance, ventriculoarterial (VA) discordance, a large unrestrictive inlet ventricular septal defect (VSD), and a dysplastic pulmonary valve with severe pulmonary valve stenosis. His only intervention was a right-sided Blalock-Taussig (BT) shunt performed when he was 4.5 months old. Cardiac catheterization performed in 2003 showed a dilated BT shunt with a distal stenosis at the anastomosis to the right pulmonary artery, normal pulmonary artery pressures, and a mean pullback gradient over the BT shunt of 43 mmHg. The branch pulmonary arteries were of good size. He also had significant cardiomegaly and the calculated Qp:Qs at the time of this scan being ∼3:1.

The patient had a background history of paroxysmal palpitations that had started in childhood. They could sometimes be stopped by vagal maneuvers. An ECG in 1988 was reported to show “atypical atrial flutter”; however, no traces were available to review in 2015. He had initially been treated with digoxin, disopyramide, and propranolol, and subsequently from 1987 was given flecainide and digoxin. Following transition from the pediatric to the adult congenital heart disease (ACHD) service, and subsequent multidisciplinary team (MDT) discussion, his flecainide was stopped in 2009 in view of his structural heart disease. At this time he had been free of symptoms from arrhythmia since 2005 and had been physically stable, in full-time employment, with NYHA Class II symptoms (shortness of breath on stairs or uphill, no ankle edema, no orthopnea) and no major limitations in his daily life. He was a nonsmoker and consumed alcohol infrequently.

The patient remained well until 2007 when he experienced a transient episode of diplopia and abnormal eye movements, which spontaneously resolved after 9 h. He reported to the local ophthalmology service where his eyes were examined and no abnormalities detected. A head CT was not performed. He was seen 1 month later by the regional ACHD service.

On examination at this time he was clubbed; height and weight were 172 cm and 50.4 kg, respectively, oxygen saturations 89% on air, blood pressure 90/50 mmHg, heart rate 68 bpm and regular, jugular venous pressure was not raised, and first and single second heart sounds were normal. There was a left ventricular heave and a grade 4/6 continuous murmur.

Blood workup showed a Hb of 16.8 g/dL (MCV 94.3) and was otherwise normal.

His ECG at this time was described as showing sinus rhythm with very large P waves, marked first-degree AV block (PR interval 380 ms); QRS duration 150 ms with a right bundle branch block pattern.

A transthoracic echocardiogram was performed (2007). Peak velocity across the pulmonary valve was 5 m/s; there was very mild left- and right-sided AV valve regurgitation and good ventricular function. There was a high velocity flow in the BT shunt (maximum systolic gradient ∼80 mmHg). No intracardiac thrombus was seen.

It was felt that the episode most likely represented a transient ischemic attack (TIA) and the patient was started on oral aspirin 75 mg once daily. A 24 h ambulatory ECG was performed, and this showed sinus rhythm throughout with first-degree heart block, occasional Wenckebach phenomenon ( Fig. 15.1 ), episodes of aberrant conduction ( Fig. 15.1B ), and sinus bradycardia ( Fig. 15.1C ). There were no tachyarrhythmias observed. Heart rate histograms are shown in Fig. 15.3D . Similar findings were again recorded on ambulatory monitoring in 2008.

24 h ambulatory monitoring (2007); a marker channel is shown at the bottom of each trace. (A) Lengthening of the PR interval followed by a nonconducted P wave. (B) An example of aberrant conduction with a change in the morphology of the QRS complex. (C) Sinus bradycardia. (D) Heart rate histograms over the 24-h period showing some diurnal variation.

He remained under regular follow-up and was stable until 2011 when he started to have intermittent palpitations again. There was no history of syncope or presyncope. A 12 lead ECG from 2010 is shown in Fig. 15.2 . During a Bruce protocol exercise test performed in 2010, he exercised for 7.39 min with an increase in heart rate from 51 bpm to a peak of 146 bpm (78% of maximum predicted). His blood pressure rose from 104/45 mmHg to a peak of 136/66 mmHg. The test was stopped due to shortness of breath. There were no significant arrhythmias noted (occasional ventricular ectopics only) and no ST segment changes with exercise. His resting saturations were 88% and fell to 63% at peak exercise.

12 lead ECG in 2010 showing sinus rhythm, first-degree atrioventricular block (PR interval 336 ms) and right bundle branch block (QRS duration 146 ms).

Repeat Holter monitoring was performed (2011), while he was taking digoxin only and showed no tachyarrhythmia, but bradyarrhythmia was noted. As previously observed, there was first-degree AV block and periods of AV Wenckebach; in addition there was evidence of more pronounced bradyarrhythmia on two separate recordings, including a daytime sinus pause of 3.59s ( Fig. 15.3A ) and P wave asystole of 5.8 s, also in the daytime ( Fig. 15.3B ); however, it did appear that in all instances of AV block, the nonconducted beats were preceded by PR lengthening. He was asymptomatic on both occasions. When symptomatic with palpitations and breathlessness, ventricular ectopics, and periods of bigeminy/trigeminy were recorded, accounting for ∼0.5% of the beat counts. Cross-sectional imaging at this time confirmed that ventricular function remained good. His digoxin was stopped and he was started on bisoprolol 1.25 mg.

(A) Ambulatory monitoring 2011—daytime sinus pause of 3.59 s (the patient was asymptomatic). (B) Daytime atrioventricular conduction block with P wave asystole of 5.8 s (the patient was asymptomatic).

Over the next 2 years, he reported a very slow deterioration in his functional status, becoming more easily short of breath and tired on exertion; however, he remained generally well and stable until 2014 when he started to experience “dizziness,” the exact nature of which was unclear. A 48 h Holter monitoring demonstrated both sinus node and AV nodal conduction disease, with occasional sinus pauses of up to 3 s and brief periods of 2:1 AV block during the daytime (traces unavailable). He continued to deny any syncope or presyncope, however, and given the potential challenges of implanting a permanent pacemaker, it was decided to continue to manage him conservatively with periodic repeat Holter monitoring.

In 2015, the patient was seen in the regional center for routine follow-up, during which he gave a history of two syncopal episodes. He was unconcerned about these episodes and had not presented himself to hospital at the time. He had been well in the interim period and his palpitations had become less intrusive. A detailed history revealed one episode of syncope was nocturnal, postmicturition, and sounded possibly vagal in etiology; however, the second occurred while supine in bed and at rest. The patient was witnessed by his partner to suddenly lose consciousness and this was accompanied by pallor and grunting/agonal breathing for ∼30 s. He was unable to recall the event. This occurred while the patient was on bisoprolol 1.25 mg od. His baseline 12 lead ECG from 2015 is shown in Fig. 15.4 .

12 lead ECG in 2015 showing pronounced first-degree atrioventricular block.

He was seen in the CHD arrhythmia clinic, and in view of the clear history of cardiogenic syncope in the context of previously documented conduction abnormalities, permanent pacemaker (PPM) implantation was empirically discussed with the patient; however, he was reluctant to undergo invasive intervention. Ambulatory monitoring off β-blockers was therefore repeated which showed nocturnal bradycardia as well as brief periods of asymptomatic second-degree block/nonconducted P waves ( Fig. 15.5 ). An MDT meeting was convened and all of the patient’s data reviewed. It was concluded that the patient should undergo PPM implantation as soon as possible. At this time ventricular function was felt to be mildly impaired.

(A) Ambulatory monitoring in 2015—PR lengthening followed by three nonconducted P waves, a sinus beat which is conduced, and then two junctional beats. (B) Sinus rhythm with 2:1 atrioventricular conduction.

After discussion and consideration of the risks involved via different access routes, an endocardial/transvenous approach was considered, but shortly prior to the scheduled procedure, the patient experienced an episode of very transient left-sided weakness and numbness with mouth drooping and slurred speech. He was reviewed by his local neurology service who felt that his symptoms were consistent with a further TIA. The procedure was postponed while the potential thromboembolic risks were reconsidered and he was started on warfarin.

A further MDT meeting was convened and an epicardial (surgical) pacemaker was recommended. The patient was reluctant to undergo general anesthesia and enquired about the possibility of a leadless pacemaker implant. On balance it was felt that the risks of general anesthesia were outweighed by the unknown thromboembolic risk of a leadless device without the capacity for AV synchrony, therefore a dual chamber epicardial system was implanted via a median sternotomy. A single chamber system was considered (which could have been performed via a limited left anterior thoracotomy); however, it was agreed that the benefit of synchronous AV contraction outweighed the increased risk of a sternotomy versus a more limited approach. The surgery was carried out uneventfully, lead parameters were satisfactory, and an abdominal box was placed without complications.

The device was programmed to promote intrinsic conduction. The patient made a satisfactory recovery but developed persistent atrial tachyarrhythmia (both a relatively organized atrial tachycardia and atrial fibrillation, Fig. 15.6 ) in the early postoperative period. He declined DC cardioversion and was treated with oral amiodarone, which eventually cardioverted him to sinus rhythm which he has maintained since with very occasional episodes of paroxysmal nonsustained atrial arrhythmia detected on pacing check ( Fig. 15.7 ). He remains well and recently became father to a healthy baby boy.

(A) Postoperative atrial fibrillation. (B) Postoperative organized atrial tachycardia.

Intracardiac electrograms from pacemaker check showing paroxysmal atrial fibrillation.