Ebstein’s anomaly of the tricuspid valve is a rare form of congenital heart disease that occurs in 1 in 20,000 live births and has a prevalence of approximately 0.5% among patients with congenital heart disease.1 It is characterized by apical displacement of the septal and posterior leaflets of the tricuspid valve. All three leaflets may be malformed or even fused.2 This results in a small right ventricle, a large right atrium, significant tricuspid regurgitation, a propensity for supraventricular arrhythmias and ultimately right heart failure. More than half of affected patients have occasional or persistent cyanosis.3 Only 5% of patients survive beyond the fifth decade.4 The previously reported oldest survivor lived to age 85 and was asymptomatic until age 79.5 Case Report. An 85-year-old woman was referred to our institution for evaluation of recurrent falls. She had a 3-month history of sudden-onset global weakness followed by frank syncope, which typically occurred when walking. These episodes usually lasted one or two minutes and witnesses noted no seizure-type activity. Recovery was prompt and required no special measures. Past medical history was remarkable for a single episode of amaurosis fugax occurring at age 84. Current medications included aspirin, conjugated estrogen replacement therapy and multivitamins. The patient was living alone. Systems review was unrevealing. Physical exam revealed blood pressure 150/88 mmHg, pulse 66 beats/minute, no orthostasis and no cyanosis. The jugular venous pulse was elevated and prominent “v” waves were noted. Cardiac exam revealed a split S1, a fixed split S2 with a diminished pulmonic component and a II/VI mid-systolic murmur at the left lower sternal border without evidence of radiation. Neurological exam was normal. Review of outside data demonstrated minimal carotid atherosclerosis seen on ultrasound obtained for evaluation of the amuarosis fugax. Laboratory studies, including lipid panel and thyroid function testing, were normal. A 12-lead electrocardiogram showed normal sinus rhythm, normal axis, first-degree atrioventricular block and otherwise normal intervals (Figure 1). Chest x-ray showed clear lung fields and an increased cardiac silhouette. Transthoracic echo revealed mild left ventricular (LV) hypertrophy, a small LV cavity and marked dilatation of the right ventricle (RV) and atrium (Figure 2). Apical displacement of the septal leaflet of the tricuspid valve was evident. Left ventricular function was normal, but the right ventricle was globally hypokinetic. Bowing of the intraventricular septum into the left ventricle in diastole suggested significant right ventricular volume overload. Doppler showed severe tricuspid regurgitation and a high-velocity jet was seen in the right atrium coming from the base of the septal leaflet. Color flow mapping of the intra-atrial septum suggested the presence of a bi-directional shunt. To further define the atrial septal defect (ASD) and determine if the high-velocity jet represented a ventricular septal defect (VSD), a transesophageal echo (TEE) was performed. This confirmed the presence of a small ASD secundum and suggested possible right ventricular outflow tract obstruction. Right heart catheterization and ventriculography were then performed. Catheterization of the pulmonary artery could not be performed despite the use of multiple guidewires. The RV was dilated and hypokinetic. Severe tricuspid regurgitation was evident and the regurgitant contrast crossed the ASD into the left atrium. The RV outlet was displaced apically (likely secondary to the displaced and dysplastic septal leaflet). The oxygen saturations (Table 1) suggested some anomalous pulmonary venous return; this was confirmed by cannulation of a vein on the lateral side of the high right atrium. This was of insignificant flow since overall right atrial and ventricular saturations were not increased. The patient experienced her typical symptoms as an inpatient while on cardiac monitor. ECG obtained at that time is shown in Figure 3. It shows a narrow complex tachycardia at a rate of 153 beats/minute. It self terminated and blood pressure during the event was 80/40 mmHg. The patient recovered uneventfully. An electrophysiology study (EPS) was then performed. Easily inducible sinus node reentrant tachycardia with a cycle length of 420 milliseconds was elicited and blood pressure consistently fell from 130/66 mmHg to 80/45 mmHg, which self terminated after a premature atrial beat (Figure 4). Radiofrequency energy was applied to the high lateral right atrium with termination of the arrhythmia. The arrhythmia could not be induced after the ablation. Intracardiac tracing obtained from the ablation site was consistent with a sinus node pattern, suggesting that the sinus node was the site of the arrhythmia (Figure 5). The patient had no further episodes of syncope. During the next 18 months she had occasional atrial fibrillation, which was suppressed with low-dose amiodarone. Discussion. This case is illustrative and unique for several reasons. In almost half of patients with syncope, a cause is never identified. Syncope is common in the elderly and an annual incidence of 6% has been reported in those over 75 years of age.6 Determination of the etiology is more critical in the elderly since they are more likely to have a cardiac cause and this portends a worse outcome. Elderly patients also tend to have multiple physiological derangements, which decrease the threshold for syncope when a new abnormality arises.7 All patients should have a 12-lead electrocardiogram (ECG). Q-waves suggest prior infarction and increase the likelihood that ventricular tachycardia is the cause. Conduction disease or QT abnormalities may similarly indicate the likely cause. Prolonged ECG monitoring is of benefit if the occurrence of arrhythmia correlates temporally with symptoms, but in many cases the occurrence of arrhythmia only correlates poorly with symptoms.8 Our patient had witnessed symptoms while in the hospital and a definite correlation could be made with the tachyarrhythmia. Electrophysiology testing is more likely to be helpful in patients with abnormal ECGs, arrhythmias noted on prolonged monitoring (Holter monitoring) and those with depressed ventricular function. Negative predictors of the utility of EPS include normal echo, normal ECG, normal Holter, prolonged syncopal episodes and absence of injury during syncope.9 ECG abnormalities typically seen in Ebstein’s anomaly include peaked P-waves, first-degree AV block, right bundle branch block (75%) and pre-excitation patterns. Accessory pathways with manifest pre-excitation (usually a right ventricular bypass, Wolff-Parkinson White type B) have been reported in about 10% of Ebstein’s anomaly cases, but rarely in asymptomatic patients. Supraventricular tachycardia occurs in 30% of patients (usually atrial fibrillation, atrial flutter or reentrant tachycardia).10 In younger patients, the presence of chronic atrial fibrillation is associated with a subsequent high mortality rate.4 The propensity to arrhythmia is attributed to the atrial dilatation secondary to tricuspid regurgitation and the atrialization of the portion of the right ventricle between the true valve annulus and the displaced septal and posterior leaflets. The most common additional findings obtained by EPS in patients with Ebstein’s anomaly include delayed intra-atrial conduction, likely secondary to the atrial dilatation. Conduction delays below the Bundle of His are also frequent, suggesting a problem with the His bundle before it bifurcates; nonetheless, complete heart block is rare. Although the tricuspid annulus is displaced in Ebstein’s anomaly, the normal relationship of the AV node to the His bundle is preserved. Consequently, the His bundle electrograms are obtained in their usual place at the junction of the right atrium and the atrialized right ventricle and not at the level of the displaced tricuspid valve. This atrialized region of the right ventricle tends to be very irritable and catheter irritation can easily provoke ventricular fibrillation.11 Ventricular tachycardia is uncommon in the absence of stimulation, occurring in less than 7% of patients.12 The displaced and nonfused tricuspid annulus is believed to contribute to the development of accessory pathways in up to 25% of patients. These pathways occur in the free wall and posterior septum. One-third of patients with accessory pathways have more than one pathway. Conduction may be intermittent and some pathways only conduct in a retrograde direction; hence, they can cause orthodromic circus motion tachycardia but not manifest pre-excitation on surface ECG. In fact, orthodromic circus motion tachycardia is the most common manifestation of accessory pathways (usually the AV node acts as the antegrade limb and the pathway as the retrograde limb). The accessory pathway’s ventriculoatrial conduction time is usually slower in Ebstein’s anomaly cases compared to other patients due to slow conduction through the atrialized right ventricle. Pathways with rapid antegrade conduction may contribute to the occurrence of syncope and sudden death. Successful catheter ablation of these pathways has been described.13 Our patient is unique in manifesting sinus node reentrant tachycardia in association with Ebstein’s anomaly. Sinus node reentrant tachycardia is rare, reported in 3–10% of patients undergoing EPS for supraventricular tachycardia.14 The sinus node and the entire crista terminalis are highly anisotropic and this inhomogeneity of tissue provides the substrate for reentry in and around the sinus node. Usually, a single extra stimulus during EPS is sufficient to induce it, especially with the use of longer coupling intervals. Criteria for identification of SNRT have been published; key criteria are P-wave morphology identical to sinus, normal sequence of atrial activation and abrupt slowing or termination with vagal maneuvers.15 Suggested medical therapy for sinus node reentrant tachycardia includes beta-blockers, calcium channel blockers and digoxin, but since the diagnosis is made during EPS, ablation has emerged as the preferred therapy. Our patient was successfully ablated; this is typical with reported success rates close to 100% and complications rare.16 Our patient is alive and well 2 years later, at 87 years of age. We believe this case is unique and illustrative for several reasons. It demonstrates the diverse causes of syncope in the elderly and our patient represents the first reported case of sinus node reentrant tachycardia in association with Ebstein’s anomaly. This patient is both the oldest reported survivor and the longest symptom-free survivor.
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