Conservative management of a ruptured mycotic aneurysm

Abstract

Mycotic aneurysms are a well-recognised complication of infective endocarditis. In contrast to many sequelae of endocarditis, they can present late in the course of the disease, despite adequate treatment. We discuss the case of an 82-year-old patient who was successfully treated for Enterococcus faecalis endocarditis, but presented late with a hypotensive collapse. CT imaging demonstrated a ruptured mycotic aneurysm. He underwent laparotomy, but the decision was made to treat conservatively to protect the vascular supply to the bowel. The patient subsequently made a full recovery.

Background

Clinical diagnosis of mycotic aneurysms is rare; however, they have been found in nearly two-thirds of patients dying with infective endocarditis.¹ Mycotic aneurysms may present many weeks or months after treatment has been instituted, and rupture is associated with high mortality of up to 37%.² This case highlights that infective endocarditis is a multisystem disease with many extracardiac manifestations, and emphasises the need for continued clinical vigilance in this high-risk group of patients.

Case presentation

An 82-year-old man was admitted acutely with a 2-day history of fever and rigours. He had undergone transurethral resection of the prostate 6 months earlier, complicated postoperatively by a urinary tract infection. Urine culture grew Enterococcus faecalis and symptoms resolved with antibiotics. For 5 weeks preceding admission, he had experienced sweats, a rash, anorexia and weight loss of 2 stones. The history included mild chronic obstructive pulmonary disease and tuberculosis 50 years previously. On physical examination, there was a petechial rash on both shins, a soft pansystolic murmur at the cardiac apex and mild clubbing. The abdomen was soft with mild tenderness in the right flank. Three splinter haemorrhages were noted in the fingers.

Blood and urine samples were sent for culture. His admitting chest x-ray and ECG were both unremarkable. Tazobactam and piperacillin were given for presumed urosepsis. Transthoracic echocardiogram on Day 2 showed a soft, mobile mass on the mitral valve, moderate mitral regurgitation and mild aortic regurgitation. On Day 3, initial blood cultures grew E faecalis in both bottles.

He was given intravenous amoxicillin and gentamicin according to local microbiology advice. A transoesophageal echocardiogram was performed, giving more detailed imaging of the mitral valve. After 4 weeks of antibiotic therapy, his symptoms and inflammatory markers had improved. Transoesophageal echocardiography during the 3rd week of treatment concluded that the vegetation had reduced in size.

On Day 30 of admission, he suffered a syncopal event while ambulatory on the ward and complained of abdominal pain and nausea.

Investigations

Blood tests after collapse showed reduction in haemoglobin from 11.5 to 7.3 g/dl. An erect chest radiograph was unremarkable, but abdominal radiography showed mild small bowel distension. CT of the abdomen showed a fusiform, irregular enlargement of the superior mesenteric artery (SMA) (figure 1).

Figure 1.

Left panel—three-dimensional reconstruction of arterial phase CT angiogram demonstrating aneurysm at the distal end of superior mesenteric artery (SMA) (arrowed); right panel—subtracted selective angiography of SMA showing aneurysm (arrowed).

Differential diagnosis

Causes of hypotensive collapse in infective endocarditis:

• Heart failure: primary muscle damage, malignant arrhythmia

• Acute valve dysfunction for example, mitral regurgitation

• Septic shock

• Fistula formation (intracardiac and extracardiac)

• Aortic root abscess causing complete heart block

• Infarction or rupture of distal abscess, for example, splenic

• Ruptured mycotic aneurysm (aortic, visceral, cerebral)

• Acute myocardial infarction—abscess occluding coronary artery, embolic

Treatment

The initial strategy attempted was embolisation of the SMA. The patient therefore underwent angiography (figure 1) and two attempts were made to place a coil within the aneurysm without success. The patient subsequently became haemodynamically unstable during the procedure and was taken to theatre for emergency exploratory laparotomy. Free blood (400 ml) was aspirated from the abdominal cavity. The abdominal contents had become adherent and separation of the bowel layers was felt to be high risk and complex. Additionally, there were fears that ligation risked compromising the vascular supply to the bowel. The decision was therefore made to treat the aneurysm conservatively. Tranexamic acid was given and he was monitored in the intensive care unit.

Outcome and follow-up

Ten days later, he had recovered and was discharged. A follow-up CT scan 2 weeks post-discharge concluded that the mycotic aneurysm appeared to have resolved and he continues to do very well in the community.

Discussion

Most complications of infective endocarditis occur early in the course of the clinical disease, before antibiotic treatment is instituted, or in its early stages. Conversely, mycotic aneurysms may often present later, after sterilisation of the valve is well underway. This is likely related to on-going physiological stresses on the damaged arterial wall that result in progression of the aneurysm.

In this case, the history of abdominal pain and sudden hypotension were indicators of an intra-abdominal event. Previous investigations, length of antibiotic therapy and the clinical state had made abscess-related complications or acute heart failure unlikely. Aneurysms of the superior mesenteric artery are often asymptomatic, but may enlarge rapidly to present with clinical symptoms. The generalised abdominal pain in this case is typical. Hypotensive shock may occur due to acute bleeding into the abdomen, and the bowel may become ischaemic; other features include diarrhoea, a pulsatile mass or visceral pain on eating (claudication abdominis). Ruptured or bleeding mesenteric aneurysm is associated with a high morbidity and mortality.²

Mycotic aneurysms at this site associated with infective endocarditis are rare, but well acknowledged in the literature. However, this is only the fifth documented case of a mesenteric aneurysm caused by an Enterococcus species.^3–6

In patients with endocarditis, abdominal symptoms should be viewed with a high index of suspicion and early input from a surgical team is essential. Diagnostic imaging should be undertaken. The most readily available modality is selective CT angiography, which can often be performed in an emergency. For more stable patients, magnetic resonance angiography can allow more detailed characterisation of the lesion and therefore permits meticulous planning of treatment options.

Repair techniques can be surgical, such as synthetic grafting or resection, or percutaneous, including endovascular stenting and embolisation with metallic coils or vascular plug devices.³ There is some evidence that the vascular plugs have shorter procedure times and a lower rate of migration,⁷ although evidence at this anatomical site is limited. In an acutely unstable patient, primary laparotomy may be necessary, and can allow rapid assessment and treatment of the bleeding site. In this case, conservative treatment with procoagulant agents offered a greater chance of recovery than surgical repair or arterial ligation due to the complex nature of the operative findings and potential risk of non-functioning bowel.

Learning points.

• Acute circulatory collapse in patients with infective endocarditis has a wide differential, which needs to be considered early in such patients.

• Late collapse may represent rupture of a mycotic aneurysm, the course of which tends to be distinct from the episode of endocarditis itself.

• Imaging techniques such as CT and magnetic resonance angiography offer clear non-invasive assessment methods, but in the acute setting, emergency laparotomy may be the only option compatible with patient survival.