Home » 2010 » Number 10-06: Common Trick, Uncommon Application

Number 10-06: False positive Gerbode Defect by CMR 

Case from: Harbin D, Ailiani R, McHugh V, Fahey D, Ferri C, Shear M, Tisue T, Perlock P.
from Gundersen Lutheran Health System, La Crosse, Wisconsin, US

Clinical history: An 80 year old male with previous mitral and tricuspid annuloplasty and partial pericardiectomy, was persistenty symptomatic with progressive right heart failure and pulmonary hypertension underwent CMR examination. CMR demonstrated an ASD and a defect in the membranous ventricular septum with flow from the left ventricle to the right atrium strongly suggestive of a Gerbode defect (Figure 1 and 2). 

Figure 1 (click to enlarge)

 

Figure 2

A repeat transesophageal echocardiogram was performed with colour Doppler to confirm the CMR findings. This confirmed tricuspid regurgitation and a separate eccentric jet of flow entering the right atrium ostensibly arising from the left ventricle (Figure 3).

Figure 3

Right heart catheterization demonstrated a Qp:Qs shunt of 1.2. A pigtail catheter was placed in the left ventricular cavity and agitated saline was injected with simultaneous surface echocardiography (Figure 4). No cross over of bubbles were seen entering the right atrium from the left ventricle, hence outruling a Gerbode defect.

Figure 4

Cine CMR: The still images of the 4-chamber cine demonstrate a thin membranous ventricular septum in diastole (Figure 2) with an eccentric jet entering the right atrium (in systolic frame, Figure 1) presumptively from the left ventricle, consistent with a Gerbode defect (LV-RA shunt). 

Echocardiogram: The original transthoracic echocardiogram (Figure 3) seems to confirm the CMR findings with two jets entering the right atrium- a central tricuspid regurgitant jet, and a second eccentric jet entering the right atrium, presumptively from the LV. The mosaic blue color seen near the tricuspid valve is due to the lower aliasing velocity of 0.39 m/sec and is resulting from high turbulence of tricuspid regurgitation.

Bubble Study: A relatively infrequently used technique of injecting agitated saline directly into the left ventricle effectively excluded a Gerbode defect and a diagnosis of eccentric tricuspid regurgitation was confirmed. 

Perspective: This case highlights the importance of complementary imaging and invasive techniques in assessing rare conditions such as a Gerbode defect.

Editors Comment: The exceptional high resolution images afforded to us using CMR must always be interpreted with the same degree of caution and attention as any other imaging modality. A unique opportunity to really define the area of interest with CMR with multiple cross cuts though the suspected VSD, high resolution cine imaging, along with in-plane and through-plane phase contrast flow imaging of the membranous interventricular septum would be likely to differentiate eccentric tricuspid regurgitation from a Gerbode defect.

References:

1. Gerbode ventricular septal defect diagnosed at cardiac MR imaging: a case report. Cheema OM, Patel AA, Chang AM, et al. Radiology 2009;252:50-52.
2. The Gerbode defect: left ventricular to right atrial communication-anatomic, hemodynamic, and echocardiographic features. Silbiger JJ, Kamran M, Handwerker S, et al. Echocardiography 2009;26: 993-8.
3. Uncommon acquired Gerbode defect (left ventricular to right atrial communication) following a tricuspid annuloplasty without concomitant mitral surgery. Dadkhah R, Friart A, Leclerc JL, et al. Eur J Echocardiogr 2009;10:579-81.


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COTW handling editor: Rory O' Hanlon