Acute aortic dissection in the paediatric population is a rare but life-threatening disease. Although clinical diagnosis is difficult, chest trauma, history of CHD, and genetic mutations have been associated with aortic dilatation and dissection in children. Reference Zalzstein, Hamilton and Zucker1,Reference Eun, Cho, Cho and Byun2 It is extremely crucial to provide an emergent intervention once identified. We present two cases of acute aortic dissection that required emergent procedures, including ascending aorta replacement and extracorporeal membrane oxygenation induction. Both patients were found to have a genetic mutation in actin alpha 2 (ACTA2) after their demise.
Case reports
Case 1
The patient was a 14-year-old boy (weight, 35.9 kg) with a history of patent ductus arteriosus device closure who initially presented to an outside hospital due to abdominal and back pain. He did not have any significant family history. Eventually, he received pain medications and was discharged home. The next day, he re-presented with chest pain, vomiting, and diarrhoea, with elevated troponin level of 7.33 ng/ml, lactate of 11 mmol/L with ST depression on electrocardiography. Echocardiography revealed an intimal flap in the ascending aorta (Fig 1c). Thoracoabdominal CT demonstrated a dilated ascending aorta of 51.5 mm and an intimal flap extending from the left lateral wall of the ascending aorta to the common iliac artery (Fig 1a and b). The intestines and kidneys were poorly perfused. He was diagnosed with type A acute aortic dissection and emergently taken to the operating room.
Figure 1. (a) dilated ascending aorta and PDA device. (b) intimal flap in the ascending aorta, aortic arch, and descending aorta. (c) intimal flap in the ascending aorta on echocardiography. PDA = patent ductus arteriosus.
A median sternotomy was performed, and pericardial tamponade of the blood was relieved. Cardiopulmonary bypass was initiated with cannulation of the ascending aorta and right atrium. We confirmed the aortic cannula was placed into the true lumen by performing echocardiography. Once his body temperature reached 22°C, cardiopulmonary bypass flow was discontinued, and retrograde cerebral perfusion was started with superior vena cava cannulation. Retrograde cardioplegia was intermittently administered. The ascending aorta was transected, and an intimal tear that entered the arch along the lesser curve toward the patent ductus arteriosus device was observed. Ascending hemiarch repair was performed using a 28-mm Dacron vascular graft. Cardiopulmonary bypass was weaned off successfully, and the patient returned to the ICU. His post-operative course was complicated by progressive multiorgan failure, including intestinal and lower-extremity ischaemia. His abdomen was extremely distended, and eventually, the patient required exploratory laparotomy. His entire bowel was dusky, especially with variable ischaemia from the ligament of Trietz to the terminal ileum. The abdomen was kept open temporarily. Moreover, his lower extremities developed compartment syndrome; therefore, we performed fasciotomy. The patient required high-dose insulin therapy, sodium bicarbonate, and renal replacement therapy due to hyperkalemia and acidosis. On CT, we found that aortic dissection extended to the right renal artery with global poor perfusion of the right renal parenchyma. His urine output was only 300 cc over the last 24 hours (0.3cc/kg/hr) with elevated creatine and BUN levels (4.41 and 40mg/dl, respectively). The next morning, he developed bradycardia with a widening QRS on electrocardiography. The patient’s family decided not to proceed with cardiopulmonary resuscitation and he died. Genetic testing revealed a heterozygous pathogenic variant in the ACTA2 gene.
Case 2
This patient was a 14-year-old boy (weight, 45.5 kg) with a history of premature infancy, developmental delay, and attention-deficit/hyperactivity disorder. One of his siblings passed away at 4 months of age with diagnosis of sudden infant death syndrome. The patient presented with abdominal and shoulder back pain with multiple episodes of emesis. Initially, he was seen at the OSH and found to have an elevated creatinine level, but non-contrast abdominal CT was normal. Chest radiographic findings showed mild bilateral pulmonary congestion. The patient was discharged with a diagnosis of constipation. However, his symptoms worsened, and he was brought to our emergency centre. He was noted to have hypertension and received morphine for pain. Shortly after obtaining his vital signs, he experienced sudden cardiac arrest with ventricular fibrillation, and cardiopulmonary bypass was initiated immediately. We did not achieve return of spontaneous circulation despite appropriate medication; therefore, the decision was to proceed with extracorporeal membrane oxygenation cannulation.
The patient was heparinised, the right femoral artery and vein were accessed, and extracorporeal membrane oxygenation was established. However, venous return was inadequate with high negative pressure. Aggressive volume administration was initiated at several litres. We then turned our attention to the right pleural space which might have compromised the venous drainage of extracorporeal membrane oxygenation, and rapidly placed a chest tube with several litres of bloody drainage. Subsequently, a left chest tube was also placed with more than 100 ml of bloody drainage. However, extracorporeal membrane oxygenation flow optimisation was not achieved. Although a left anterior thoracotomy was performed to ensure that the pericardium was drained, a small amount of bloody pericardial effusion was observed and extracorporeal membrane oxygenation flow was still under-optimised. The heart was firmly contracted and did not appear to be fibrillating or contracting. Despite this, adequate extracorporeal membrane oxygenation flow could not be achieved. Given greater than 90 minutes of cardiopulmonary bypass were attempted, including 30 minutes of extracorporeal membrane oxygenation support, the decision was made that further attempts at resuscitation were futile, and cardiopulmonary bypass was stopped. The patient underwent an autopsy, which demonstrated aortic dissection. The primary intimal tear was located at the ascending aorta, and aortic dissection extension was from the ascending aorta to the bifurcation to the common iliac arteries. Additionally, there was a ruptured site on the thoracic aorta close to the left subclavian artery. Genetic testing revealed a heterozygous pathogenic variant of ACTA2.
Discussion
Acute aortic dissection in young children is rare and has several predisposing factors. Although Ficker et al. reported that 22% of young children and adolescents had no risk factors, Reference Fikar and Fikar3 this disease is recognised in children particularly with CHD, connective tissue disorders, or severe trauma. Reference Zalzstein, Hamilton and Zucker1,Reference Eun, Cho, Cho and Byun2 We reviewed articles published since 1992 focusing on paediatric aortic dissection, enrolling patients aged < 19 years (four original articles and 35 case reports including our cases; Table 1). Reference Shamszad, Barnes and Morris4–Reference Teien, Finley and Murphy38 The mortality rates were 12–38% in the original articles. According to the case reports, nine patients died among 24 cases of Stanford A aortic dissection (37.5%). Genetic mutations and chromosomal anomalies were found in 17 cases (41.4%). The ratio is equivalent to that reported in other original articles. These findings strongly suggest that Stanford A aortic dissection is extremely lethal and should be carefully managed in children with genetic and chromosomal anomaly. However, an accurate clinical diagnosis of acute aortic dissection in children is challenging because its frequency is obviously less than that of other diseases in terms of differential diagnosis. Chest and back pain with migration, high blood pressure, leg ischaemia, and neurological findings may be clues for detecting acute aortic dissection. However, their symptoms are sometimes atypical and unremarkable, which confuses physicians. In fact, both cases were initially discharged and then re-admitted in an unstable condition. Although CT scan is the gold standard for diagnostic modality, we can consider the transesophageal echocardiography in the operating room. Physicians working in acute care settings, particularly in emergency centres, should be aware of disorders that predispose to acute aortic dissection.
Table 1. Literature review of pediatric aortic dissection
AAR = ascending aorta replacement; ACTA2 = actin alpha 2; ASD = atrial septum defect; AVD = aortic valve disease; BAV = bicuspid aortic valve; CKD = chronic kidney disease; CTD = connective tissue disease; FBN1 = Fibrillin 1; HLHS = hypoplastic left heart syndrome; LDS = Loeys–Dietz syndrome; LOX = Lysyl Oxidase; N/A: not applicable; SMAD = suppressor of mothers against decapentaplegic; TAAR = thoracic aortic arch replacement; TOF = tetralogy of Fallot; TGFRB = transforming growth factor-beta; VSARR = valve sparing aortic root replacement.
Once the diagnosis of acute aortic dissection is established, surgical interventions should be performed without any delay. Severe acidosis and malperfusion are associated with an extremely increased mortality rate in the surgical treatment of type A aortic dissection. Reference Lawton, Moon and Liu39 While transporting the patient to the operating room, medical management including beta-blockers, bicarbonate, and adequate sedation to stabilise the patient are crucial. In paediatric hospitals, the ability to have an aortic adult surgeon is extremely helpful. Perfusionists may not be familiar with paediatric aortic surgery in terms of cardiopulmonary bypass strategy and circuit size. For instance, retrograde cerebral perfusion, which we utilised in Case 1, is not often performed in paediatric cases except for cerebral protection. Reference Sahu, Ingole, Bisoi and Venugopal40 In addition, materials, such as vascular grafts, are limited for small children. Therefore, it is necessary to discuss the accessibility of aortic surgeons and perioperative management with operating room teams in advance.
Genetic testings are also important in aortic dissection in children. In our cases, both patients had an ACTA2 gene mutation, which was found after death. Thus, we recommended familial screening to these families. ACTA2 encodes for a smooth muscle α2-action protein. Pathogenic mutations in ACTA2 disrupt contractility and are a recognised cause of aortic dissection. Reference Yetman, Starr and Bleyl41 The patient in the first case had undergone patent ductus arteriosus device closure in infancy. In the context of ACTA2 gene mutation, the patent ductus arteriosus device procedure may have increased the risk of aortic dissection by disrupting the intima. After losing these patients, our genetic team was involved in family support. In addition to their genetic evaluation, prevention of forthcoming events and providing psychological support following distressful and tragic events are important
Acknowledgements
None.
Financial support
This research received no specific grant from any funding agency, commercial, or not-for-profit sectors.
Conflict of interest
None.
Ethical standard
Informed consent was obtained from the patient’s legal guardians.
