Gerbode defect: A rare complication of infective endocarditis.

Infective endocarditis (IE) is a severe disease characterized by severe complications and high mortality rates. The direct communication from the left ventricle (LV) to right atrium (RA), namely, the Gerbode defect, is a rare complication of endocarditis.

A 32-year-old male presented with symptoms of fever and dyspnea. Clinical examinations revealed pansystolic murmur that was most prominent at the left parasternal region and audible at the apex with a parasternal heave. Laboratory examinations revealed elevated acute phase reactants, and a Roth spot was observed on fundoscopic examination. Echocardiography revealed a bicuspid aortic valve and highly mobile vegetation on the ventricular side of the anterior mitral leaflet [Figure 1]. Empiric therapy customized to the patient was immediately initiated with the diagnosis of bacterial endocarditis. Furthermore, transesophageal echocardiography revealed LV to RA and LV to right ventricle (RV) shunts [Figure 2]. A high-velocity systolic (>4 m/s) color Doppler flow from the upper membranous septum toward the RA was demonstrated. The diagnosis of infravalvular Gerbode defect was supported by two separate systolic jets across the tricuspid valve. The patient was confirmed with the diagnosis of the Gerbode defect, which was acquired as a complication of IE. Although there was no hemodynamic compromise, the patient was referred for cardiac surgery. At the 1-year follow-up, after mechanical valve implantation and ventricular septal defect (VSD) repair, the patient did not have any complaints.

Figure 1

The highly mobile vegetation (see arrow) in ventricular side of anterior mitral valve leaflet. AV: Aortic valve; AMVL: Anterior mitral valve leaflet; LA: Left atrium; LV: Left ventricle

Figure 2

Two separate systolic jets across tricuspid valve supported the diagnosis of infravalvular Gerbode defect. MV: Mitral valve; TV: Tricuspid valve; LA: Left atrium; LV: Left ventricle; RA: Right atrium; RV: Right ventricle; (curved arrows indicate systolic jets)

A congenital shunt from the LV to RA was first described in an autopsy report of a patient in 1838 by Thurnam J. In 1958, the defect was named Gerbode after the surgeon who performed a successful surgery on five patients with this anomaly.[1] It can also be acquired as a complication of surgical aortic and/or mitral valve replacement or due to IE.[2] The Gerbode defect could be a direct (supravalvular) or indirect (infravalvular) connection depending on the involvement of the tricuspid septal leaflet and the presence of additional communication between the LV and RV.[3] In our patient it is plausible that the mixed type of Gerbode defect was acquired as a consequence of bacterial invasion of the membranous septum. Reportedly, endocarditis causes LV–RA shunt by reconnecting a congenital defect, widening a small but nonsignificant shunt, or perforating the septum.[45]

Physiologically, a shunt is formed from the LV to RA due to a large pressure gradient that exists between these cardiac chambers.[5] Patients with IE usually present with fever and septicemia that may mask a new shunt formation, and the diagnosis of VSDs may easily be missed.[5] The Gerbode defect should be distinguished from other conditions, such as ruptured sinus of Valsalva aneurysms or VSD with severe tricuspid regurgitation. The diagnosis in our patient was based on the echocardiographic findings: (i) atypical jet direction, (ii) persistent shunt flow into diastole, (iii) lack of ventricular septal flattening, (iv) no RV hypertrophy, and (v) normal diastolic pulmonary artery pressure as estimated from the pulmonic regurgitant velocity, suggesting the Gerbode defect. Asymptomatic patients with insignificant intracardiac shunt should be followed up carefully rather than undergo surgical repair.[6] Besides, LV–RA shunts due to the defect of the membranous septum increases the risk of endocarditis. In addition, a history of endocarditis is a major risk factor of endocarditis. However, surgical management of IE with acquired Gerbode defect is preferred to ensure effective source control, prevention of embolism, and recurrence of IE. Hence in our patient, despite the absence of circulatory overload and RV pressure or volume overload due to a small LV–RA shunt, we referred him for cardiac surgery.

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