An Infected Bicuspid Aortic Valve, an Anomalous Coronary Artery, and a Dog-Bitten Postman

Congenital coronary artery anomalies are estimated to occur in 0.3% to 1.3% of the population.² Most cases are asymptomatic incidental findings; however, certain anomalies increase the risk of myocardial ischemia, HF, or sudden cardiac death. Angelini, in particular, found left anomalous coronary artery from the opposite sinus of Valsalva (ACAOS) posed such a risk that surgical revascularisation is warranted.^3,4 However, whether surgery is indicated for right ACAOS is less clear.⁴ There was no statistically significant survival benefit in surgical management versus medical management among 247 patients with anomalous coronary arteries who were followed for 10 years, in what the authors perceived as an asymptomatic variant.⁵ Intramural aortic courses (IACs) of anomalous coronary arteries may also increase the risk of developing ischemia in the setting of compression from an aortic valve replacement. In systole, the aorta stretching may predispose patients to constriction of an intramural anomalous coronary artery. The intercoronary commissure may compress the anomalous vessel in diastole also. Anomalous coronary arteries may also be atretic as a consequence of developmental haemodynamics.⁵ The slit-like orifice, and acute angle of take-off, creates a haemodynamic effect similar to an ostial stenosis, which reduces coronary blood flow.⁵ This is why deroofing may be advocated for over bypass grafting. In Guidelines for the Management of Adults With Congenital Heart Disease, anomalous left coronary artery from the right (ALCA-R) with IAC should be revascularized. (Class- I recommendation).⁶ In anomalous right coronary artery from the left sinus (ARCA-L), revascularization is only advocated for in the presence of documented ischemia, sudden death, or unexplained arrhythmia (Class-I recommendation), but multidisciplinary team management could support the decision for surgical repair in asymptomatic cases (Class-IIa recommendation).⁵ In our case, we elected not to bypass the right ACAOS as the patient was asymptomatic and the prognostic benefit of bypass in his case, was questionable.

The BAV was found to have fusion of right and left coronary cusps, Sievers Type 1. Abnormal valvulogenesis results in BAV. Adjacent cusps fail to split, leaving only 2 cusps, 1 of which is frequently larger than the other. The morphology of the commissures changes depending on how they are united. In roughly 2% of individuals with a BAV, anomalies in coronary artery anatomy, such as anomalous origins of coronary arteries and upwardly displaced coronary ostia, are found.⁷ The autosomal-dominant inheritance pattern for BAV is regarded to be the most prevalent, but there is evidence of genetic variability, and the pattern may be varied.⁷ It is a Class-1 recommendation from the American College of Cardiology and the American Heart Association to screen relatives using echocardiography in first degree relatives.^6-9 This man’s family have been referred for screening.

C. canimorsus is a facultatively anaerobic, fastidious Gram-negative bacillus considered to be a commensal oral flora in dogs. It was originally described by Bobo & Newton in 1976 in a patient with meningitis. Patients who are immunocompromised, particularly with asplenia and alcoholics are predisposed to severe infections with fulminant sepsis. It has been associated with a wide variety of infections including meningitis, septic arthritis, and IE.⁸ Infective endocarditis accounts for under 2% of C. canimorsus blood stream infections and is rare. Between 1977 and 2019, there were 18 cases of C. canimorsus IE reported in the literature (Table 1). Twelve of these cases had animal contact with a dog, 1 with a lion, and in 5 cases animal contact was not described.¹⁰ Recent publications report B-lactamse production in between 32% and 70% of isolates. A Class-D beta-lactamase has been described among in 4 strains of C. canimorsus. This gene, designated ‘blaOXA-347, is phenotypically associated with resistance to penicillin, cephalosporins, and imipenem and is classified as a carbapenemase.

Historically, phenotypic identification of bacteria was only available, but with the advent of proteomics, it has been possible to identify phylogenetically related species within geni. Molecular methods such as full gene sequencing, genomic restriction analysis, conventional ribotyping, 16S-23S intergenic spacer gene sequencing may be utilized for intrageneric differentiation of bacterial species.¹¹ Bacterial 16S rRNA gene sequencing is commonly used for bacterial identification of culture-negative samples. All bacteria have the 16S rRNA gene, which is an exceptionally maintained segment in the 30 S subunit, the transcriptional engine.¹¹ Ubiquitous PCR primers may be constructed to select the conserved sections of the 16S gene, allowing for the amplification of the gene in a variety of microorganisms from a lone specimen. The 16S rRNA gene has both conserved and varied sections, which allows for global amplification and discrimination amongst bacteria. For most bacteria and archaea, public databases provide type strains of 16S rRNA gene sequences. In this case, 16SPCR of the infected valve tissue clenched the diagnosis and provided justification for targeted antimicrobial treatment. The patient would otherwise have been treated with a broader regimen increasing the risk of adverse drug reactions and increased healthcare cost.

In conclusion, this textbook case demonstrates the risk factors for IE, the complex multidisciplinary decision-making surrounding management for IE and the utility of 16S PCR in providing appropriate antimicrobial management.