Consultant’s Opinion #1

Madhukar S. Kollengode, MD

Duy T. Nguyen, MD

This is a case that highlights the nuanced nature of the management of electrophysiology issues for adult patients with unrepaired congenital heart disease (CHD). There is an increased incidence of atrial arrhythmias in patients with ASDs. This is a consequence of long-standing hemodynamic overload resulting in atrial myocardial remodeling with increased myocyte size, interstitial fibrosis, and alterations in ultracellular structure predisposing to the development of atrial arrhythmias, in particular, atrial fibrillation (AFib). Electrical remodeling has also been described, with increased P-wave duration and dispersion, as well as a lengthened atrial effective refractory period (AERP). Although the majority of changes in patients with ASD are seen in right-sided chambers, a study evaluating patients with left-sided accessory pathways and ASD demonstrated lengthened AERP and enhanced inducibility of AFib. Importantly, despite the known remodeling and geometric distortion of the right ventricle associated with unrepaired ASD, there is no conclusive evidence of increased risk for ventricular arrhythmias.

The first consideration is the management of recurrent symptomatic AFib in this patient with unrepaired primum ASD. Therapy directed towards the restoration and maintenance of sinus rhythm is recommended . The long-term thromboembolic risk in this patient with simple nonvalvular CHD is not unlike that in the general population, and the decision to pursue anticoagulant therapy to prevent embolic complications should be guided by established scores for assessing risk such as the CHA ₂ DS ₂ -VASc. This patient’s CHA ₂ DS ₂ -VASc score of at least 1 is associated with low–moderate (0.9% per year) risk of embolic complications; either no antithrombotic therapy or treatment with an oral anticoagulant or aspirin may be considered. We agree with the decision to initiate systemic anticoagulation, especially in the setting of recurrent AFib requiring cardioversion and the presence of an intracardiac shunt lesion. This can be accomplished with warfarin (international normalized ratio goals, 2.0–3.0), or by utilizing novel anticoagulants (NOACs) such as direct thrombin inhibitors or factor Xa inhibitors. Management guidelines increasingly favor utilization of NOACs over warfarin, and in the absence of CHD-specific data, it is reasonable to consider NOACs in this patient with simple CHD and no hemodynamically significant valvular disease .

The ASD is hemodynamically insignificant (by MRI stroke volumes, no chamber enlargement), and normal right atrial size does not represent a risk factor for permanent AFib. Initial rhythm control strategy for paroxysmal AFib utilizing Vaughan Williams class Ic agents, such as flecainide and propafenone (in the absence of significant structural heart disease or coronary artery disease), or class III agents, such as sotalol, dronedarone, or dofetilide, in conjunction with direct current (DC) cardioversion is reasonable. We have had success with patients who did not tolerate sotalol but had less symptoms and good rhythm control on dofetilide, which is often better tolerated than other antiarrhythmics. Catheter-based ablative therapy for rhythm control is useful for symptomatic paroxysmal AFib that is refractory or intolerant to at least one class I or III antiarrhythmic medication and is reasonably the first-line therapy for recurrent symptomatic paroxysmal AFib. The success of AFib ablation in patients with CHD is lower; in a series of patients with predominantly simple CHD (ASDs in 61%), the success at 300 days was achieved in 42% compared with 53% of controls. In this patient with recurrent symptomatic paroxysmal AFib who was intolerant to therapeutic doses of sotalol, AFib ablation is reasonable; however, other antiarrhythmics with different side effect profiles may also be considered.

The second issue is the diagnostic workup and management of symptomatic monomorphic wide complex regular tachycardia, which highlights the complexity of appropriate patient selection and risk stratification for ICD therapy in adult CHD (ACHD). Exercise-induced nonsustained VT has been reported in ∼4% of asymptomatic middle-aged adults, with no increased mortality risk. Hemodynamically tolerated VT in adults with CHD should be managed according to well-established adult guidelines, while taking into consideration CHD-specific issues. Expert consensus guidelines for management of arrhythmias in patients with ACHD suggest considering EPS in those with palpitations suggestive of sustained arrhythmia when a conventional diagnostic workup is unrevealing, but these are based on limited clinical evidence. In this situation, nonsustained monomorphic VT with hemodynamic compromise was reported during exercise testing, with replication of his clinical symptoms.

EPS with programmed ventricular stimulation, which is utilized for risk stratification in some patients with ACHD such as those with repaired tetralogy of Fallot, has been of little prognostic utility in other forms of CHD. There is no known association between ASDs and increased risk of ventricular arrhythmias. There are reports of SCD in patients with ASD, but the subgroup represented an older population with coexisting coronary disease. The presence of nonsustained VT in this adult is likely due to acquired factors and is unrelated to the hemodynamically insignificant ostium primum ASD. Although ASD should be considered while making management decisions, risk stratification for SCD and ICD placement should focus on traditional risk factors. ICD therapy is far from benign and carries up to a 20% cumulative incidence of inappropriate shocks, as well as risks of device infection and lead malfunction. In the absence of syncope, ventricular dysfunction, evidence of structural arrhythmogenic foci, or a family history of SCD, the placement of an ICD is rarely indicated.

EPS with programmed ventricular stimulation may be used to characterize arrhythmias and confirm a ventricular origin versus supraventricular tachycardia with aberrancy or occult accessory bypass tract, to document inducibility of VT, to guide catheter ablation, and to assess risks for recurrent VT or SCD to determine the need for ICD therapy. The symptoms correlated with the presence of a monomorphic, rapid, wide complex tachycardia and thus it was reasonable to proceed with EPS to identify and ablate the arrhythmogenic ventricular focus .

VT was noninducible during EPS. Premature ventricular contractions with similar morphology to clinical VT were reportedly targeted. The inferiorly directed LBBB morphology VT with late precordial transition and predominantly negative deflection in lead I ( Fig. 4.1 ) are features suggestive of an outflow tract origin, more likely right ventricular outflow tract. As an early intrinsic precordial transition in this patient is seen with sinus rhythm ( Fig. 4.1 , lead V2), compared with the later precordial transition of the VT, the ablated focus at a reported left-sided septal substrate below the outflow tract seems inconsistent with the clinical VT, as noted in the figures. Furthermore, the LBBB morphology’s premature contractions reported following ablation are of unclear clinical significance and may be exits of different foci or related to the clinical VT and would themselves be amenable to catheter ablation. Inducibility of VT may depend on both sedation/anesthesia and concurrent pharmacologic and pacing modalities, which is generally required to ensure optimal abolition of the clinical VT. In this patient, the role of ICD in the prevention of SCD remains unclear and hinges on the reported hemodynamic compromise. There are risks of multiple ICD shocks for VT that may otherwise be targeted with ablation.

Lastly, we address the role of S-ICD rather than that of conventional transvenous ICD. Owing to a twofold increase in the risk of systemic thromboembolism in patients with conventional transvenous devices and intracardiac shunts, S-ICD is an appealing option in patients with ACHD. He is on systemic anticoagulation and this will mitigate, although may not entirely abolish, his risks of paradoxic emboli with a transvenous system. Additionally, venous cardiac access is often limited in patients with ACHD because of previous surgical treatments. S-ICD is a suitable alternative unless bradycardia therapy, cardiac resynchronization, or antitachycardia pacing are required. In this patient with uncomplicated venous anatomy and a high likelihood of ongoing atrial arrhythmias (increasing risks of inappropriate shocks), as well as remaining ventricular arrhythmogenic foci that may respond to antitachycardia pacing maneuvers, S-ICD may not be an ideal choice when compared to continued anticoagulation and/or surgical closure. These concerns may also increase the threshold for which an ICD should be implanted.