Show notes
CardioNerds (Amit Goyal and Josh Saef) join ACHD fellow Dr. Prashanth Venkatesh and ACHD program director Dr. Jeannette Lin, both from the University of California, Los Angeles, for a deep dive into the complex disease entity that is Ebstein anomaly. They discuss the anatomic features of the dysplastic tricuspid valve as well as the right ventricle in patients with Ebstein anomaly, and how these structural features affect cardiovascular physiology and clinical presentation. This is followed by an in-depth discussion into associated entities including arrhythmias and atrial-level shunts as well as the appropriate multimodality evaluation. Finally, they tackle the difficult question of when and how to intervene, delving into the various interventional treatments and exploring their outcomes using illustrative case-based examples. Audio editing CardioNerds Academy Intern, Pace Wetstein.
The CardioNerds Adult Congenital Heart Disease (ACHD) series provides a comprehensive curriculum to dive deep into the labyrinthine world of congenital heart disease with the aim of empowering every CardioNerd to help improve the lives of people living with congenital heart disease. This series is multi-institutional collaborative project made possible by contributions of stellar fellow leads and expert faculty from several programs, led by series co-chairs, Dr. Josh Saef, Dr. Agnes Koczo, and Dr. Dan Clark.
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Pearls
Ebstein anomaly is characterized by an inherent myopathy which is often more clinically consequential than the more obvious tricuspid valvulopathy. This can affect not only the right ventricle due to ‘atrialization’ and severe tricuspid regurgitation (TR) but also the left ventricle that is often small due to chronic preload deprivation from reduced RV outflow (no flow, no grow)!Diagnosing severe TR on echocardiography in patients with Ebstein anomaly is challenging, due to the frequent absence of a clearly defined vena contracta and lack of hepatic vein systolic flow reversal. Be on the lookout for severe low gradient TR, which may manifest as a triangular doppler signal rather than the normal parabolic profile.If an electrocardiogram of a patient with Ebstein anomaly suggests prior inferior myocardial infarction, be very suspicious for a right-sided accessory pathway! These are seen in nearly a third of patients with Ebstein anomaly, and manifest as negative delta waves in the inferior leads, leading to a pseudo-infarct pattern. NOTE: infarction, aberrancy, and ventricular hypertrophy should not be coded in the presence of an accessory pathway (i.e., WPW pattern).Patients with Ebstein anomaly who are planned for tricuspid valve replacement should undergo an electrophysiology study preoperatively, since the cavo-tricuspid isthmus responsible for atrial flutter that plagues a large number (20%) of these patients will be covered by a tricuspid prosthetic valve ring and be inaccessible for future catheter ablation.Certain patients with Ebstein anomaly with significant baseline RV dysfunction who require tricuspid valve surgery may benefit from a concomitant Glenn shunt, which is a surgical anastomosis of the superior vena cava to the right pulmonary artery. This relieves the dysfunctional RV of a third of its baseline preload, potentially enabling it to recover effectively from the stress of cardiopulmonary bypass.
Show notes
1. What is Ebstein anomaly and why does it occur?
Ebstein anomaly is a rare congenital heart defect of the tricuspid valve (TV) and the myocardium. It occurs in approximately 1 in 200,000 live births.Ebstein anomaly occurs because of defective delamination of the TV. Delamination is the process by which the TV leaflets form from tissue that peels away from the endocardium and myocardium of the right ventricle.Specifically, the septal and posterior leaflets of the TV are inadequately delaminated in Ebstein anomaly. Since they didn’t peel away sufficiently from the myocardium to form the TV at the valve annulus, these leaflets are small, dysplastic and attach significantly more apical to the true tricuspid valve annulus.The anterior TV leaflet is attached to the true TV annulus, but is long, redundant, and floppy, hence often described as ‘sail-like’. It may have fenestrations and can have fibrous attachments to the free wall of the RV. It may also be non-restricted and prolapse into the RV outflow tract, causing outflow obstruction.
2. How is the myocardium affected in Ebstein anomaly and what are the hemodynamic sequelae?
Ebstein anomaly is characterized by an inherent ventricular myopathy which often is more clinically important than the tricuspid valve dysfunction.The apically displaced tricuspid valve resulting from inadequate delamination causes the RV to be partitioned into a ‘functional RV’ which is responsible for generating RV outflow and an ‘atrialized RV’ which is a redundant chamber anterior to the true TV annulus but posterior to the septal and posterior leaflets.The atrialized RV is redundant since it does not contribute to RV output, and hence takes out a lot of the RV contractile reserve, especially in cases of severe apical displacement of the TV. In these cases, the functional RV chamber generating the output may be small and can get dysfunctional due to the superimposed severe TR.Also, since the RV output is reduced, the left ventricle (LV) is chronically deprived of preload and is often smaller than normal (remember – no flow, no grow). The LV may also have features of noncompaction cardiomyopathy, further contributing to myocardial dysfunction.
3. What are the major clinical findings in Ebstein anomaly?
Look for clubbing, cyanosis, and hypoxemia at rest or on exertion, which may occur due to interatrial shunting.Extra heart sounds are common in Ebstein anomaly, due to flow across the abnormal TV. It has been memorably described as sounding like someone falling down the stairs.A TR murmur may or may not be heard and may be suppressed due to the presence of laminar rather than turbulent flow, through a very wide regurgitant valve orifice.A CV wave, usually seen in patients with acquired severe TR, are usually absent in patients with Ebstein anomaly despite having severe TR, since the severely dilated RA typically absorbs the regurgitant flow and blunts the transmission of pressure into the internal jugular vein during systole.Manifestations of RV failure including ascites, leg edema, and exertional dyspnea are often seen in cases of severe RV dysfunction.
4. What are some of the key echocardiographic features of Ebstein anomaly?
The key finding that you need to identify immediately on an apical 4 chamber view is the abnormal apical position of the septal attachment of the TV. NOTE that the tricuspid valve normally attaches more apically than the mitral valve. To meet echocardiographic criteria for Ebstein anomaly, the attachment of the septal leaflet of the TV should be 8mm/m2 (normalized for body surface area) apical from the septal attachment of the anterior mitral valve leaflet.The right atrium is usually severely dilated and comprises both the anatomic right atrium (posterior to the true TV annulus) and the ‘atrialized RV’.Tricuspid regurgitation is seen in essentially all cases of Ebstein anomaly and is commonly severe or torrential. However, this may not be obvious because the malcoaptation of the leaflets is often so severe that a vena contracta may not be seen.Hepatic vein flow reversal in systole from severe TR is usually absent because the extra flow of the TR is absorbed by the severely dilated RA and does not cause high pressure in the hepatic vein.A sharp, triangular profile of the TR jet on continuous wave doppler rather than its usual parabolic form may be the only indication of severe low gradient TR seen in Ebstein anomaly.RV myopathy can lead to interventricular dyssynchrony that can manifest as abnormal motion of the interventricular septum.
5. What conditions are associated with Ebstein anomaly and how are they best diagnosed?
Up to 90% of Patients with Ebstein anomaly have an atrial level shunt, which is either an atrial septal defect or patent foramen ovale, best seen on transesophageal echocardiography. Right-to-left interatrial shunting can cause exertional hypoxia that is detected on cardiopulmonary exercise testing. These defects may also predispose to paradoxical emboli.One-third of Patients with Ebstein anomaly have associated Wolff-Parkinson-White syndrome from accessory pathways. Two-thirds of these are right-sided pathways and can be diagnosed on electrocardiography, where they manifest as negative delta waves in the inferior limb leads, often mimicking a Q-wave myocardial infarction. These can be definitively diagnosed with an electrophysiology study.Additional arrhythmias include AV nodal re-entrant tachycardia and focal atrial tachycardia in up to 20% of patients, as well as atrial flutter in approximately 20% of patients.Markedly tall P-waves with amplitude 2.5 mm are seen in nearly all Ebstein’s patients, due to severe (often massive) right atrial enlargement. The P-waves are classically known as ‘Himalayan’ P-waves due to their markedly peaked morphology. Most Patients with Ebstein anomaly have right bundle branch block on ECG.