Discussion

These five cases demonstrate that large right ventricular outflow tract aneurysms/pseudoaneurysms can occur after right ventricular outflow tract surgical reconstruction. Patients should be monitored for this uncommon complication, especially during the first post-operative year. Careful imaging evaluation is important, since patients can often remain asymptomatic even when the aneurysm/pseudoaneurysm is large,^{Reference Antal, Cikirikcioglu, Myers, Didier and Kalangos1} as seen in 4/5 patients in this series. In addition, it can be difficult to differentiate between true aneurysms and pseudoaneurysms clinically. While prior reports have shown pseudoaneurysms are more likely to increase in size rapidly and true aneurysms have a higher chance of stabilising,^{Reference Rosenthal, Gross and Pasternac2} Patient 5’s pathology was consistent with a pseudoaneurysm, which remained stable in size until repair 7 years after diagnosis. Progression can be followed with chest radiographs (Fig 2), which may show widening of the cardiac silhouette or aneurysm/pseudoaneurysm calcification.^{Reference Pillai, Reddy, Kulkarni, Murthy and Cherian3} Echocardiography can be used to diagnose both true and pseudoaneurysms, though two patients in this series were not diagnosed until angiography was performed. Pseudoaneurysms may have a shorter neck and more often have rough margins in comparison to the smooth lining of a true aneurysm.^{Reference Rosenthal, Gross and Pasternac2} The neck of the pseudoaneurysm will also be narrower and colour flow can help demonstrate continuity of flow to the right ventricle.^{Reference Pillai, Reddy, Kulkarni, Murthy and Cherian3} Lack of myocardial or full thickness endothelial tissue in the pseudoaneurysm wall may increase the risk of rupture of the thin-walled structure, though this did not occur in any of our patients.^{Reference Antal, Cikirikcioglu, Myers, Didier and Kalangos1}

Figure 2. Serial chest radiographs from Patient 1 depicting aneurysm progression from (a) the day of tetralogy of Fallot repair, (b) 2 months later with an enlarging cardiac silhouette and opacity at the left superior aspect of the heart, and (c) just prior to aneurysm resection.

This complication should be suspected when there are respiratory complaints, which Patient 1 presented with, as patients are often asymptomatic until the aneurysm/pseudoaneurysm is large enough to cause airway compression, leading to respiratory distress.^{Reference Antal, Cikirikcioglu, Myers, Didier and Kalangos1} A chest radiograph may raise suspicion for an aneurysm/pseudoaneurysm, which can be confirmed in most patients by echocardiography. Usually, non-specific symptoms are discovered on routine follow-up, though patients may present with right ventricular failure or syncope.^{Reference Antal, Cikirikcioglu, Myers, Didier and Kalangos1,Reference Calabro, Santoro, Pisacane, Pacileo, Giovanna and Vosa6}

The location of the aneurysm/pseudoaneurysm can differ based on the type of surgical repair, as seen in this case series, and result from disruption or dehiscence of part of the surgically reconstructed outflow tract.^{Reference Sah, Berdjis, Valdez and Gates7} Use of ventriculotomy and pericardial patch,^{Reference Antal, Cikirikcioglu, Myers, Didier and Kalangos1,Reference Rosenthal, Gross and Pasternac2,Reference Seybold-Epting, Chiariello, Hallman and Cooley4} residual obstruction of the right ventricular outflow tract or branch pulmonary arteries,^{Reference Antal, Cikirikcioglu, Myers, Didier and Kalangos1,Reference Rosenthal, Gross and Pasternac2,Reference Seybold-Epting, Chiariello, Hallman and Cooley4,Reference Peer, Bhat, Furtado and Chikkatur5} ventricular septal defects,^{Reference Seybold-Epting, Chiariello, Hallman and Cooley4} infection, and elevated right ventricular pressure causing excessive stress on the patch or suture line^{Reference Antal, Cikirikcioglu, Myers, Didier and Kalangos1–Reference Pillai, Reddy, Kulkarni, Murthy and Cherian3} have been reported as more common causes. At catheterisation, all patients in this series demonstrated >2/3 systemic right ventricular pressure and branch pulmonary artery stenoses, and three had residual ventricular septal defects.

After the aneurysm/pseudoaneurysm is identified, urgent surgery is usually indicated to resect the aneurysm/pseudoaneurysm and for additional surgical intervention for residual lesions. Four patients in this series had branch pulmonary artery stenoses addressed at the time of aneurysm/pseudoaneurysm repair, and one patient (Patient 2) required catheterisation the next day for right pulmonary artery stent angioplasty. All patients also required subsequent transcatheter bilateral branch pulmonary artery balloon and/or stent angioplasty within 8 months, but the most recent imaging demonstrated no aneurysm/pseudoaneurysm recurrence in any of our patients.

While no patient in this series had rupture, ongoing dilation is possible and, thus, prompt surgical revision should be considered in patients with this complication. Progressive aneurysm/pseudoaneurysm dilation risks rupture and compression of adjacent structures.^{Reference Pillai, Reddy, Kulkarni, Murthy and Cherian3,Reference Calabro, Santoro, Pisacane, Pacileo, Giovanna and Vosa6} Patients should also be evaluated for related complications such as thrombus formation within the aneurysm, which has been reported and adds risk for embolisation to the pulmonary circulation. Early operative correction is especially prudent in these patients.^{Reference Seybold-Epting, Chiariello, Hallman and Cooley4,Reference Peer, Bhat, Furtado and Chikkatur5} Close proximity or adherence of the aneurysm/pseudoaneurysm to the sternum may make re-operation challenging. Careful pre-procedure assessment with imaging is important to aid with surgical planning.^{Reference Pillai, Reddy, Kulkarni, Murthy and Cherian3}

This case series highlights an uncommon, yet striking, complication that can occur following surgical right ventricular outflow tract reconstruction with associated anatomic conditions which may place a patient at higher risk. Awareness of, and close clinical attention to, this potential complication is important.