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Ventricular tachycardia following aortic valve replacement
  1. Noor Mohammed,
  2. Uday Dandekar,
  3. Faizel Osman
  1. Department of Cardiology and Cardiothoracic Surgery, University Hospitals of Coventry and Warwickshire NHS trust, Coventry, UK
  1. Correspondence to Dr Noor Mohammed, Department of Cardiology, University Hospitals of Coventry and Warwickshire, Coventry CV2 2DX, UK; drnoorullah{at}yahoo.co.in

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Introduction

A 23-year-old man underwent mechanical bi-leaflet implant following infective endocarditis of native trileaflet aortic valve. He developed sustained runs of ventricular tachycardia (VT) (left bundle branch block (LBBB) morphology) 5 days postoperatively with loss of cardiac output needing external electrical cardioversion. Physical examination revealed an ejection systolic murmur in the aortic area (grade 2/6) and a pan-systolic murmur (grade 4/6) along the left sternal edge with raised jugular venous pressure. Routine blood tests demonstrated leucocytosis and a raised C reactive protein, and chest radiography showed pulmonary oedema. Transoesophageal echocardiography (TOE) was performed (figure 1).

Figure 1

Preoperative transoesophageal echocardiogram image (top) and spectral continuous wave Doppler (bottom).

Question

Based on these images and the clinical data the most likely diagnosis is:

  1. Severe tricuspid regurgitation (TR) with tricuspid valve endocarditis

  2. Prosthetic valve dehiscence

  3. Acquired LV to right atrial shunt

  4. Muscular ventricle septal defect

For the answer see page 820

From the question on page 793

ANSWER: C

The patient had distinct echocardiographic features of an acquired Gerbode defect. TOE revealed abnormal systolic flow between the LV and right atrium (RA) (figure 1, see online supplementary video 1). The mechanical prosthesis was intact with no paravalvular regurgitation.

It can be difficult to distinguish a muscular ventricular septal defect and tricuspid valve leaks from a LV–RA defect in view of dense velocity and anatomical close relationship between the three structures (tricuspid valve, aortic valve and sub aortic membranous septum). However, misdiagnosis can be prevented by remembering to look for a LV–RA shunt, with careful review of the jet origin, morphology and direction.1 The large systolic pressure gradient between the LV and the RA resulted in a high velocity Doppler flow signal in RA (figure 1). It can sometimes be mistakenly diagnosed as a tricuspid regurgitant jet simulating pulmonary arterial hypertension. The continuous wave (CW) Doppler study shows continuous signal due to pressure gradient between LV and RA. In comparison the CW Doppler signal in TR is limited to the systolic phase of cardiac cycle. In our case the peak pressure difference across the defect was 4.0 m/s (64 mm Hg). The CW Doppler signal in prosthetic valve dehiscence with aortic regurgitation would demonstrate flow in opposite direction to normal forward systolic flow and thus the answer choice is wrong.

The condition was first described by Gerbode in 1958 and is commonly seen as a congenital defect.2 Endocarditis is the second most important cause of acquired LV–RA shunts. It is usually associated with advanced heart block as the conduction system lies within the membranous septum. Therefore, it is not surprising that infection or laceration of this area damages conduction. LBBB pattern with inferior axis VT suggested it has originated from the RV outflow tract (RVOT) in view of right heart strain. A high index of suspicion is needed to look for unusual aetiology once the common correctable causes of VT are excluded. The diagnosis of LV–RA communication is not easy, and should be remembered in patients who do not recover normally.

Our patient successfully underwent redo homograft aortic valve replacement with intraoperative confirmation of echocardiographic findings (see online supplementary figure S1). Post pump TEE demonstrated a well-functioning prosthesis and small residual shunt with reduced RV size and no TR (see online supplementary figure S2). There was no recurrence of VT following surgery and the patient was discharged after 6 weeks of intravenous antibiotic therapy.

References

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Footnotes

  • Contributors All the authors were involved in the clinical care of the patient and contributed towards manuscript.

  • Competing interests None.

  • Patient consent Obtained.

  • Provenance and peer review Not commissioned; externally peer reviewed.