Case Synopsis

A 34-year-old man was referred to the congenital heart disease arrhythmia service in 2015. Original diagnoses were tricuspid atresia and pulmonary stenosis. Previous interventions were a left modified Blalock-Taussig shunt in 1980 as an infant; atriopulmonary Fontan operation in 1983 (aged 3 years) with subsequent conversion to an intracardiac total cavopulmonary connection (TCPC) fenestrated (4 mm) lateral tunnel, resection of right atrium (RA) wall, and Gor-Tex enlargement of left pulmonary rtery (LPA) in 1995 (aged 15 years). Following this he was cyanosed with baseline saturations on air of 90%–93%, desaturating to ∼84% on exercise. Cardiac catheterization in 2001 showed a patent bidirectional Glenn with good size pulmonary arteries; the inferior vena cava (IVC) tunnel was patent and dilated at 7 cm, with rapid filling of the levo phase, excluding pulmonary vein compression. Pressures were as follows: left ventricle (LV)—86/5 mmHg, IVC 9/6 mean 8 mmHg, superior vena cava (SVC) mean 9 mmHg, LPA mean 8 mmHg, right pulmonary artery (RPA) 8 mmHg, LPA to PA pullback—no gradient, LV to Ao pullback—no gradient; saturations: SVC 77%, IVC 84%, RPA 80%, LPA 77%. Left ventriculography—preserved systolic function.

The patient began to develop symptoms of palpitations in 2002 with documented atrial tachycardia and went on to have electrophysiologic (EP) studies with radiofrequency catheter ablation in 2002, 2004, and 2005. He was noted to be in a persistent atrial tachycardia on each occasion and for all procedures a 3D electroanatomic mapping system was used. The procedures were not performed in the same regional center in which he was being seen for his congenital heart disease. Examples of his tachycardia are shown in Fig. 10.1 .

Atrial tachycardia, (A) In 2002, (B) In 2004, (C) In 2005.

The first procedure performed in 2002 was the ablation of a macroreentrant tachycardia within the pulmonary venous atrium accessed via the fenestration and comprised of a circuit in the morphologic left atrium, using the mitral valve annulus and an area of scar on the posterior wall. Tachycardia was slowed but not terminated with ablation and still inducible at the end of the case. He was discharged on amiodarone, which initially maintained sinus rhythm; however, by the end of 2003, he again developed a persistent atrial tachycardia.

His second procedure was performed in 2004. The pulmonary venous atrium was again accessed via the lateral tunnel fenestration. Two tachycardia were seen—one with a cycle length of 240 ms, the other faster but with a similar appearance on 12 lead ECG. There were large areas of the atrium electrically dissociated from the tachycardia circuit which occupied the anterior and lateral parts of the native right atrium. This appeared to have an area of scar as its central obstacle and was terminated during the creation of a linear lesion from the scar to a line of double potentials in the posterolateral aspect of the right atrium and believed to represent the suture lines of the lateral tunnel. At the end of the case, sustained tachycardia could not be induced (including with isoprenaline).

In 2005 a third procedure was performed. Under conscious sedation, it was noted at this time that the pressure within the lateral tunnel was 19 mmHg. Mapping of the lateral tunnel and systemic venous atrium revealed focal activation arising from the inferior part of the residual interatrial septum. Ablation here slowed and subsequently terminated the tachycardia; however, there was transient atrioventricular (AV) block after the ablation. A second tachycardia was then ablated in a similar area to the circuit seen in 2004, on the lateral wall of the pulmonary venous (morphologic right) atrium. At the end of the case the patient was in Mobitz type I (Wenckebach) second-degree heart block, which subsequently resolved to first-degree heart block ( Fig. 10.2 ), and by the time of discharge the PR interval was reported as being within normal limits.

First-degree atrioventricular block post AT ablation (PR ∼ 300 ms).

Following his third catheter ablation, it was felt that the clinical priority was to reduce his cyanosis rather than pursue further attempts at electrophysiology (EP) intervention, regardless of arrhythmia recurrence. He remained on long-term anticoagulation with warfarin and a maintenance dose of 100 mg amiodarone once daily, which reduced the burden of his symptoms. The fenestration was closed in 2006 with a 4 mm Amplatzer Septal Occluder device and afterward there was no residual flow into the right atrium. Post device placement baseline oxygen saturations were 97% on room air.

Subsequently he was well, in sinus rhythm with an unremarkable cardiorespiratory examination, normal blood pressure, and no signs of heart failure. In view of his age, the amiodarone was converted to dronedarone 400 mg twice daily, which he tolerated well. During this time he was in full-time employment with an active social life and regularly participated in light/moderate sporting activities. He smoked 10 cigarettes per day and drank a little alcohol socially.

In 2011 he again started to become more troubled with intermittent symptoms of palpitations. He also complained of occasional dizziness.

Ambulatory monitoring in February 2011 showed an atrial arrhythmia burden of 34% with frequent atrial ectopics as well as periods of atrial bigeminy and sustained atrial arrhythmia ( Fig. 10.3 ). Heart rate histograms showed normal diurnal variation with a minimum heart rate of 47 bpm at night and a maximum heart rate of 105 bpm during the day. In view of the documented symptomatic atrial tachycardia, it was decided that more aggressive management of his arrhythmia was required and in 2012 he had two further attempts at catheter ablation. At the first in early 2012, he had evidence of two predominant circuits, one related to the scar on the posterolateral right atrium and the second to the isthmus between the IVC and AV valve. Ablation was successfully undertaken of both these circuits. By this time, venous cannulation was only possible via the left (not right) femoral route due to right femoral vein occlusion. Just over 6 months later, another procedure was undertaken; on this occasion there were three tachycardias ablated: one a macroreentrant tachycardia related to scarring on the lateral and septal aspects of the tunnel and also two focal/microreentrant tachycardias, arising from the high right atrium and also the lateral right atrium both within the tunnel. At the end of the procedure he had evidence of nonsustained atrial arrhythmia only.

(A) Atrial bigeminy; (B) Atrial tachycardia.

2015

Despite an apparently successful procedure in 2012, by 2015 he had a further recurrence of atrial tachycardia. Having had multiple ablation procedures over the previous decade, however, a consensus decision was made after the fifth procedure, not to pursue an invasive approach and to continue with medical therapy. Functionally he had otherwise remained stable. Available serial ETT/CPEX data are shown in Table 10.1 . Transthoracic echocardiography in February 2015 showed no LV outflow obstruction, a dilated left ventricular cavity with mildly reduced systolic function, moderate left-sided AV valve regurgitation (longstanding), no spontaneous echo contrast within the TCPC or residual fenestration detected. The patient remained in a persistent atrial tachycardia; however, the ventricular rate was well controlled ( Fig. 10.4 ), and there was no hemodynamic compromise or intrusive symptoms.

TABLE 10.1

Serial functional (exercise) assessments

	2001	2006	2010	2011
Study	Modified Bruce	Bruce	CPEX	CPEX
Time (mins)	18	13:24	7:35
RER	—	—	1.15
METS		15
Vo2 max (% predicted)	—	—	20.3 mL/kg/min (51)	21.2 mL/kg/min (54)
Resting HR			78
Max HR (% predicted)	140	96	102 (68)	117 (61)
Resting BP (mmHg)		120/70	110/80
Peak BP		150/80	150/80
Rhythm/arrhythmia		Intermittent Wenckebach and atrial flutter	SR, first-degree AV Block, LBBB (QRS 116 ms)	Sinus rhythm with frequent atrial ectopy
Test terminated due to		Leg fatigue	SOB

 

BP , blood pressure; HR , heart rate; LBBB , left bundle branch block; METS , Metabolic Equivalents; RER , respiratory exchange ratio; SOB , shortness of breath; SR , sinus rhythm.

Persistent atrial tachycardia in 2015 with controlled ventricular response.

In 2015, the patient had worsening palpitations and was started on bisoprolol 2.5 mg once daily. These symptoms considerably improved; however, he began to experience infrequent but severe presyncope. 12 lead ECG showed a junctional rhythm at 36 bpm ( Fig. 10.5 ). The bisoprolol was reduced to 1.25 mg once daily and ambulatory ECG was undertaken which showed sinus pauses (up to 9 s— Fig. 10.6 ), paroxysms of rapidly conducted atrial tachycardia, and frequent periods of junctional rhythm.

Junctional bradycardia in 2015.

Nine second sinus pause followed by junctional bradycardia.

His case was reviewed at a multidisciplinary team meeting and a decision was made to implant a surgical pacing system. This was initially attempted via a subxiphoid incision; however, it was not possible to obtain acceptable ventricular lead pacing parameters through this approach, therefore a further lateral thoracotomy was performed. It was noted that the epicardium was extremely fragile, however, and it was still not possible to anchor a pacing lead adequately here and the patient was closed without pacemaker insertion.

In view of the necessity for pacing and the failed surgery, a decision was made to attempt placement of an endocardial system percutaneously via a transbaffle puncture. The procedure was performed during therapeutic anticoagulation with warfarin. This was a long and complex procedure and the transbaffle puncture was difficult as the baffle was heavily calcified. Although the baffle was eventually successfully punctured, it was only possible to pass a single guide wire and not a sheath via an anterograde approach. The guide wire was then snared via a retrograde (transfemoral) route, allowing eventual passage of a guide sheath and placement of a single pacing lead at the ventricular apex with satisfactory parameters. A single chamber device was implanted as it was felt that there was insufficient space in the transbaffle puncture to implant a second lead and that this would also be too high risk. On balance, although there was no evidence of AV conduction disease, it was decided that a ventricular lead should be placed rather than an atrial lead, in the event of developing more advanced AV conduction disease in the future, and in the hope that in the meantime, ventricular pacing would rarely be needed. Postprocedural chest X-ray is shown in Fig. 10.7 . The generator was placed prepectorally and the wound closed without complications. However, femoral arterial access was unintentionally lost during the terminal part of the case, resulting in a significant retroperitoneal hematoma which required vascular surgery. Despite this, the patient made a good recovery and was successfully discharged home. At review in outpatient clinic in early 2016 the patient confirmed that he was no longer having presyncope, and pacing check showed 3% ventricular pacing. He remains in a regular atrial tachycardia with a ventricular rate of 74 bpm on dronedarone 400 mg bd. He complains of occasional palpitations; however, there have been no high rate episodes detected on device check. His main complaint is of generalized mild tiredness. Saturations are reduced from 97% preprocedurally to 91% at latest follow-up. At the current time, there is no intention for him to undergo any further catheter ablations.

Postprocedural chest X-ray.