Acute coronary syndrome caused by extrinsic coronary compression from an aortic root abscess in a patient with mechanical aortic valve endocarditis: a case report and literature review

Abstract Background  Extrinsic coronary compression is an extremely rare complication of aortic root abscess formation and can manifest as an acute coronary syndrome in infective endocarditis. Optimal management strategies are unknown and therefore illustrative case reports may be informative. Case summary  We describe a 63-year-old man with a background history of a mechanical aortic valve who developed sepsis due to Escherichia coli bacteraemia from a presumed urinary source. He suddenly deteriorated with cardiogenic shock and anterior ST-segment elevation myocardial infarction on Day 16 and received emergency percutaneous coronary intervention for severe stenoses of left anterior descending and diagonal arteries. A transoesophageal echocardiogram 2 days later demonstrated a large aortic root abscess. He was transferred for emergency surgery which revealed a large aortic abscess surrounding the left main stem confirming extrinsic coronary compression. He received a redo tissue aortic valve replacement and repair of his abscess cavity. Discussion  We describe a case where percutaneous coronary intervention and emergency surgery was used to treat extrinsic compression from an aortic root abscess; a complication that is associated with a high mortality. This is also a rare case of E. coli causing prosthetic valve endocarditis. We also explore the findings of 11 previous cases of extrinsic coronary compression from aortic root abscess.


Introduction
Acute coronary syndrome (ACS) occurs in 2.2% of infective endocarditis (IE) with a mortality of 27% based on registry data. 1 Acute coronary syndrome is associated with a higher mortality and risk of heart failure in the setting of IE. Extrinsic compression from aortic root abscess is extremely rare being present in 11 previous case reports and only 1 of the 26 patients studied in a retrospective study of 1210 patients giving an incidence of 4% of patients with ACS in IE. 1 The commonest mechanism of ACS in IE is septic emboli. Other causes include mycotic aneurysm formation, severe aortic regurgitation, external compression, or aortic valve vegetations obstructing coronary ostia. 1 Escherichia coli has infrequently been associated with prosthetic valve endocarditis. We describe a 63-year-old man who suffered with an aortic root abscess of his mechanical aortic valve causing extrinsic coronary compression.

Case presentation
A 63-year-old man was admitted to the emergency department with fevers, dry cough, and transient non-exertional central chest ache. He had a history of mechanical aortic valve replacement (AVR) 15 years earlier due to rheumatic heart disease for which he took warfarin. On examination, he appeared diaphoretic and was febrile (>40 C) but was haemodynamically stable with no respiratory compromise. His chest sounds were clear and his heart sounds revealed his mechanical second heart sound with no added sounds. There were no peripheral stigmata of IE. His blood tests showed deranged liver function tests, C-reactive protein 197 mg/L (normal 0-10 mg/L) and international normalized ratio (INR) >10 (target range 2-3). His dipstick urine test was strongly positive for blood. His chest radiograph revealed his aortic valve prosthesis but no consolidation or pulmonary oedema. His blood and urine cultures grew extended spectrum beta-lactamase E. coli and he was commenced on intravenous Meropenem for a presumed urinary source of sepsis. He continued to spike daily fevers and an ultrasound abdomen and a computed tomography (CT) abdomen and pelvis did not reveal an alternative source of infection. He became acutely unwell with respiratory failure and tachycardia on Day 16 and his electrocardiogram showed sinus tachycardia and anterior ST-elevation ( Figure 1). He was taken immediately to the cardiac catheter lab and was found to have diffuse tapering stenosis of his left anterior descending (LAD), diagonal, and circumflex vessels. He had percutaneous coronary intervention (PCI) to LAD and diagonal with three drug-eluting stents ( Figure 2, Supplementary Material). He became extremely hypotensive in cardiogenic shock and was commenced on a dobutamine infusion and taken to the high dependency unit. On Day 18, he had a pulseless ventricular tachycardia arrest requiring two cycles of cardiopulmonary resuscitation and he was intubated and managed on the intensive treatment unit. He received a transoesophageal echo which showed an aortic root abscess and aortic valve endocarditis (Figures 3-6, Supplementary Material). He was extubated successfully and transferred to a cardiothoracic centre for emergency surgery after rapid pharmacological reversal of warfarin. The aorta was opened and the mechanical valve and infected tissue were explanted. A large abscess cavity surrounding the left main stem (LMS) was revealed confirming extrinsic coronary compression as a cause of his ST-segment elevation myocardial infarction (STEMI). The right ventricular outflow tract was opened to decompress the abscess cavity. The abscess had formed a left coronary to right ventricular (RV) fistula which was oversewn. The large defect in the aorta was repaired with a bovine pericardial patch. A 23-mm Magna (Edwards Lifesciences) tissue aortic valve was placed. The culture of the explanted valve revealed E. coli. His transthoracic echocardiogram at discharge showed an ejection fraction of 25% with a well seated AVR. Due to spontaneous contrast in his left ventricle (LV), he was felt to have a high risk of future LV thrombus and was commenced on rivaroxaban and aspirin. He was successfully discharged following a prolonged inpatient stay and progressed well with rehabilitation. At the time of writing, he is active and lives independently. Unfortunately, he continues to suffer with shortness of breath [New York Heart Failure Association (NYHA) 3] secondary to ischaemic cardiomyopathy. A cardiac magnetic resonance study performed 2 years following his admission shows a large LAD territory and right ventricular chronic myocardial infarction causing severely impaired biventricular systolic function. He receives optimal medical management for heart failure and is scheduled for cardiac resynchronisation device therapy.

Discussion
We describe a case where PCI and emergency surgery was used to treat extrinsic compression from an aortic root abscess; a Day 1 Hospital admission with fevers, dry cough, and atypical chest pain.
Day 2 Blood and urine cultures grew extended spectrum beta-lactamase Escherichia coli. Treated for sepsis of presumed urinary source with intravenous antibiotics.

Days 3-15
Ultrasound abdomen and whole-body computed tomography was negative for infective source.

Day 16
Sudden deterioration with ST-segment elevation myocardial infarction and cardiogenic shock. Coronary angiogram revealed severe stenoses of his left anterior descending and diagonal for with he received primary percutaneous coronary intervention.

Day 18
Ventricular tachycardia arrest cardiac arrest in intensive treatment unit for which he was successfully cardioverted.

Day 19
Transoesophageal echocardiogram confirmed an aortic root abscess and mechanical aortic valve endocarditis.
Emergency surgery with a redo tissue aortic valve replacement and abscess cavity repair.
complication that is associated with a high mortality. This is the first case described of this complication in a mechanical aortic valve. The low initial suspicion for IE due to positive urinary cultures and an atypical organism incurred delays to definitive management and is a crucial learning point of this case. Although E. coli endocarditis is extremely rare, it is an important differential diagnosis in the setting of   E. coli bacteraemia and patients with a prosthetic valve who are inherently high risk. This case is also unique as the patient survived several catastrophic complications of endocarditis; aortic root abscess, STEMI, and cardiogenic shock. The pattern of diffuse tapering stenosis involving the LMS, proximal LAD/diagonal bifurcation and circumflex matches the angiographic appearance of other reported cases of extrinsic compression from abscess that was confirmed with CT. 2-5 A CT scan was not performed due to his moribund clinical status and urgency of his surgery. Transoesophageal echocardiogram (TOE), however, demonstrated the abscess was in close proximity to the left coronary artery origin and compression was later confirmed at surgery. At the time of surgery, the abscess had formed an RV fistula which was not present on his TOE following his STEMI, suggesting it was a new progression of his abscess rather than a cause of his STEMI. His PCI was a high-risk procedure due to risks of propagating potential septic emboli and the prospect of placing coronary stents during active endocarditis. However, PCI was deemed necessary in the setting of cardiogenic shock and STEMI. One previous case does describe the attempted use of bare-metal stents in a similar circumstance; however, the patient died from cardiogenic shock, highlighting the life-threatening nature of this complication. 2 We identified 11 contemporary cases of extrinsic coronary compression from aortic root abscess on literature search ( Table 1). [2][3][4][5][6][7][8][9][10][11][12] Demographics were widespread in terms of age (ranging from 22 to 82 years). Nine males were affected. Four were caused by prosthetic aortic valve endocarditis; however, six of eight native valve endocarditis had known aortic valve disease prior to admission. No patient had a mechanical aortic valve. Time of onset from symptoms of endocarditis to clinical syndrome caused by the coronary compression ranged from a few days to 2 months. The proximal left coronary artery was involved in all but one case where the aortic root abscess was compressing the right coronary artery. It is clear from the literature that the clinical syndrome is associated with critical illness (five had cardiogenic shock and one resulted in sudden cardiac arrest) and mortality (seven patients died by the time the case was described). Staphylococcus aureus was the causative organism in seven patients; the remaining were Staphylococcus epidermis, Enterococcus faecalis, and two patients had negative blood cultures.
The optimal strategy of reperfusion in ACS during IE remains unclear due to the rarity of the condition and paucity of outcome data. Percutaneous coronary intervention may be complicated by LMS or distal embolization of vegetation. Percutaneous coronary intervention can also lead to the development of mycotic aneurysm and incurs risks of dissection, perforation, or post-stent stenosis. It may, however, be considered in critical illness as with our patient and should be contemplated on a case-by-case basis. Aspiration thrombectomy has been successfully used in previous cases with the added benefit of culture and sensitivity of aspirated vegetations. 13 Thrombolysis is associated with negative outcomes in the presence of IE due to the high risk of intracranial haemorrhage from subclinical cerebral emboli. 1 Prosthetic valve E. coli endocarditis is a non-HACEK (haemophilus, aggregatibacter, Cardiobacterium hominis, Eikenella corrodens, and kingenella) gram-negative bacilli infection that is extremely rare being described mainly in case reports. Incidences have been quoted as low    as 0.51% of all endocarditis and are associated with older age, women and states of immunocompromise such as diabetes, haemodialysis, and malignancy. 14 It does occur more commonly in prosthetic valves and previous systematic review reveals 52% has a urinary source as with our patient and up to a third are considered nosocomial in nature. 14,15 The mortality is high (21%). 15 Registry studies suggest the occurrence of intracardiac abscess with non-HACEK infection to be 42%. 14

Conclusion
This case highlights the rare but catastrophic complication of extrinsic coronary compression that can occur with aortic root abscess and how percutaneous coronary intervention and emergency surgery was used in its management.

Lead author biography
Dr George Joy is a research fellow in cardiac imaging at Barts Heart Centre. His research interests include interventional cardiology and advanced imaging in cardiomyopathy.

Supplementary material
Supplementary material is available at European Heart Journal -Case Reports online.
Slide sets: A fully edited slide set detailing this case and suitable for local presentation is available online as Supplementary data.

Consent:
The authors confirm that written consent for submission and publication of this case report including images and associated text has been obtained from the patient in line with COPE guidance.