Case Report An Unusual Case of Acute Myocardial Infarction

A 53-year-old male presented with acute coronary syndrome (ACS). Outside hospital coronary angiography a week ago had been normal. One year ago, patient had undergone aortic valve replacement with a bioprosthetic valve. Bedside echocardiography showed a rocking AV prosthesis. Patient underwent immediate valve surgery disclosing bioprosthetic ring endocarditis with partial ring detachment. ACS in prosthetic valve carriers should prompt early bedside TTE.


Introduction
The clinical definition of acute myocardial infarction denotes the presence of acute myocardial injury detected by abnormal cardiac biomarkers, preferably hs-cTn, and clinical signs of myocardial ischemia, such as symptoms of myocardial ischemia, new ischemic ECG changes including the appearance of new pathological Q-waves, imaging evidence of loss of viable myocardium or identification of new coronary thrombus by angiography or autopsy.Apart from coronary causes, there are numerous conditions underlying myocardial injury such as heart failure, myocarditis, trauma, cardiac procedures, sepsis, infection, kidney dysfunction, acute pulmonary embolism, chemotherapy, radiation, hypertrophic cardiomyopathy and other structural heart disease.We are describing a patient presenting with chest pain, ECG changes, elevation of cardiac troponin and a new wall motion abnormality, finally classified as type 2 myocardial infarction [1] associated with prosthetic valve endocarditis.We highlight the role of echocardiography in non-invasive imaging of ACS [2].

History of presentation: how the patient was admitted, physical examination
A 53-year-old male was admitted because of recurrent chest pain irradiating to the left hand and left shoulder, and hs-cTn elevation.Electrocardiogram (ECG) in the asymptomatic patient showed elevated ST segments in V1-V3 and a loss of R-wave progression in V1-3 (Figure 1), compared with a previous ECG.On clinical examination, the patient was a pleasant man in excellent condition, bronzed from a recent holiday in Italy, without fever, chills or malaise.Except for a systolic murmur at the right sternal border physical examination was normal.On current admission hemoglobin was 10.7 g/dL (normal value 13,5-18,0 g/dl), white blood cell count was 20,29 G/L (normal value 4,0-10,0 G/L), CRP was 2.0 mg/dl (normal value <0,5 mg/dl), myoglobin was 1742 ng/ ml (normal value 23-72 ng/ml), hs-cTn was 169 pg/mL (normal value 0-14 ng/L), and CK was 763 U/L (normal value < 190 U/L).

Past Medical History
Patient had a history of systemic lupus, and had undergone aortic valve replacement with a biological prosthesis (25 mm Carpentier Edwards Inspiris) two years ago for aortic regurgitation.On the night when he had arrived at the Italian seaside four weeks ago, he had first noted abrupt precordial chest pain.He had been seen in a local hospital late that night, but was dismissed with a normal ECG and a hs-cTn around 300pg/mL, with the recommendation to consult with a cardiologist upon return home.The patient had followed the advice, and undergone cardiac catheterization two weeks ago, which was normal (Figure 2).Laboratory values at the time of the catheterization showed a white blood cell count of 12,8 G/L (normal value 4,0-10,0 G/L), NT proBNP of 344 ng/L (normal value <125 ng/L), and Troponin I of 151 ng/L (normal value < 45,2 ng/L).TTE was reported as showing minimal mitral valve regurgitation and a prosthetic aortic valve, but no other abnormalities.Patient had been discharged same day because he was clinically well.

Differential diagnosis
Differential diagnoses of the patient's condition are psychosocial derangements, metabolic disturbances including insulin-resistance, and inflammatory diseases [2].

Investigations
Bedside TTE in the emergency room showed a rocking motion of the AV prosthesis (Video 1), compared with a TTE 10 months before (Video 2).Furthermore, new apical dyskinesia was noted.Acute TEE confirmed combined aortic valve prosthesis stenosis and regurgitation resulting from partial ring detachment.

Management (medical/interventions)
No cardiac catheterization was done.Instead, patient underwent immediate valve surgery.Vegetations on the ventricular and aortic aspect of the non-coronary cusp of the AV prosthesis were found (supplemental Figure 1) with a perforating connection to the left ventricle.The non-coronary aspect of the valve ring was completely detached by a circumferential aortic ring abscess.The dysfunctional aortic valve prosthesis was replaced with an Edwards Inspiris Resilia-23 mm, including a patch reconstruction of the aortic annulus after cleaning the abscess cavity.
Supplementary Figure 1: Explanted aortic valve bioprosthesis with endocarditis lesions on the ventricular aspect of the valve.

Patient Perspective
Patient had chest pain, was seen by two hospitals and three cardiologists, but remained without a diagnosis over one month.He had no symptoms of endocarditis, e.g.fevers, chills, fatigue or breathlessness.

Discussion
In this case, imaging evidence of new partial dehiscence of the prosthetic valve and the clinical suspicion of silent LAD embolization favored the urgent diagnosis of prosthetic valve endocarditis (PVE).No major or minor Duke criteria were fulfilled prior to surgery [3], but pathological criteria confirmed the diagnosis of PVE [4].PVE is a severe, life-threatening complication that accounts for 10-30% of all cases of infective endocarditis (IE) IE [5].Patients with prosthetic heart valves are classified as a highrisk group for IE [4,6,7].Peri-annular extension of the infection in IE is a serious and relatively common complication and is associated with high mortality [7].The incidence of early PVE in the first 12 months after surgery is 43%, while the incidence of late PVE (beyond 12 months after surgery) is 57% [6].The aortic valve is subject of PVE in 66.5%, the mitral valve in 40.7%, the tricuspid valve in 2.9% of cases, and PVE involving more than one valve occurs in 7.2% of patients [8].The most common underlying infectious organism is Staphylococcus aureus.In the present case blood cultures and cultures of the extracted valve were negative.Diagnostic imaging of prosthetic valve endocarditis is a difficult task [9].In general, the most informative method is TEE, which allows imaging of vegetations, abscesses or fistulas, leaflet mobility and ring stability.The sensitivity of TEE in the diagnosis of PVE ranges from 82% to 96%, in contrast to TTE carrying a sensitivity of only 17% to 36% [10].However, in our clinical case, bedside TTE gave the clue (video 1), and indicated emergent surgery [11].A quick review of the previous TTE on file in the hospital (video 2) enabled the diagnosis of a new wall motion abnormality in the distal interventricular septum and the left ventricular apex, different from the specific wall motion abnormality of Takotsubo syndrome.TEE was done acutely in the cath lab, showing the dehiscent valve ring (video 3) and turbulent flow around the valve.

Follow-up
The postoperative course was uneventful.The patient was discharged from the hospital on Dalbavancin 1,5 g once per week because of an allergy to penicillin, and was followed up closely, with no more events.The patient has completely recovered as of the last follow-up visit in June 2023.

Conclusion
Optimal management of PVE is still controversial.Emergency surgery may be necessary to prevent acute pulmonary edema and cardiogenic shock [4].The cornerstone of surgical treatment of patients with PVE is the implantation of a new valve in a completely debrided site.In our case, the patient was diagnosed with an aortic root abscess with valve ring detachment, presenting clinically as ACS, and echocardiographically as rocking valve.The exact pathomechanism of myocardial injury during PVE is unclear and may include mechanical coronary compression and septic embolism into the coronary circulation [12].

Figures
Figures 2A and 2B: Coronary angiography prior to current admission.