In our patient, we suspect that the source of bacteremia was a recent upper respiratory or sinus infection, given her symptoms of BIE were heralded by mucopurulent rhinorrhoea. Haemophilus parainfluenzae bacteremia has previously been reported in association with maxillary sinusitis, and was complicated by mitral valve endocarditis, which presented with multiple cerebral emboli [12]. Although in our patient, there were no clinical signs of a stroke, she had a head computed tomography (CT) scan to rule out a clinically silent cerebral embolus. Typically, the vegetations in Haemophilus spp. endocarditis are large, and consequently, have a high propensity for systemic embolization, including to the brain, kidneys, spleen and liver; systemic embolization occurs in approximately 70% of patients who are subsequently diagnosed with H. parainfluenzae endocarditis [5, 11]. In our patient, we noticed non-tender, macular lesions of the sole of her right foot, which were consistent with Janeway lesions and splinter haemorrhages. The likelihood for embolization is directly related to the size and filamentous morphology of the vegetations in H. parainfluenzae endocarditis [13]. In one series, vegetations > 10 mm were reportedly three times as likely to embolize than those that were < 10 mm in size [10].

Our patient had other features of H. parainfluenzae endocarditis: it usually affects young people, between the ages of 20–30, has a female preponderance, and a predilection for the mitral valve; owing to its high virulence and slow-growing nature, results in destruction of the mitral valve apparatus [11, 14]. Fortunately, in our case, the perforation was limited to the P3 segment of the PMVL, allowing for cardiac surgeons to perform a Carpentier sliding leaflet plasty for mitral valve repair. Notably, the mitral valve is the most commonly affected valve in H. parainfluenzae endocarditis, followed by the aortic valve [11].

Our patient also had some atypical findings: firstly, it is unusual for BIE to afflict previously healthy, native heart valves, especially in the absence of risk factors, such as intravenous drug abuse, or a history of rheumatic or congenital heart disease [1, 5, 15]. However, in one series, > 50% of patients diagnosed with H. parainfluenzae endocarditis had no underlying valvulopathy [16]. Moreover, our patient was found to be anaemic on serial laboratory tests with a normal mean corpuscular volume (MCV), which is consistent with normocytic anaemia. She had no history of menorrhagia, nor had she noticed any frank blood loss. Our patient was also symptomatic with complaints of unremitting fatigue, palpitations, and pallor; whilst these symptoms may be attributed to the underlying bacteremia, anaemia would certainly have further exacerbated them.

This case highlights the role of transesophageal echocardiography in the investigation and management of mitral valve endocarditis. Due to its proximity to the left atrium and the mitral valve, a TOE is the most sensitive imaging modality to identify vegetations, any damage to the mitral valve apparatus and study the haemodynamic consequences (regurgitation or perforation). In our patient, although a TTE showed vegetation on the PMVL, it failed to demonstrate perforation of the P3 segment, which was identified from the subsequent TOE. clinically, this was an important finding because BIE complicated by a destructive penetrating lesion is an indication for surgical intervention.

In our patient, there were several indications for surgery: left-sided BIE caused by a highly resistant micro-organism, complicated by destructive penetrating lesion with evidence of persistent bacteremia or fever lasting for > 5 days after initiating antibiotic therapy, presenting with recurrent emboli and persistent vegetation despite appropriate antibiotics. Importantly, in our case, urgent surgery was deemed necessary since our patient had native valve endocarditis (NVE) and had mobile vegetation > 10 mm with clinical evidence of embolic phenomena (Janeway lesions and splinter haemorrhages) despite appropriate antibiotics.

Furthermore, TOE has a role in preoperative planning. In this case, the identification of the perforated P3 segment of PMVL in a young female patient, allowed surgeons to counsel the patient on the feasibility for repair and possibility for replacement, either with a bioprosthetic or mechanical valve. If a repair were not feasible or successful, a mechanical prosthesis would warrant lifelong anticoagulation with Warfarin, which is a teratogenic agent. This can have lasting implications with regards to conception for a young woman of reproductive age, since warfarin handling can be challenging perinatally.

This case reiterates the difficulty in diagnosing HACEK endocarditis due to the slow-growing nature of these organisms. Clinically, this translates into a delay in initiating appropriate antibiotics and worse outcomes (e.g., multiple systemic emboli, perforation or destruction of valve apparatus, abscess formation, lethal arrhythmias). The average incubation period for H. parainfluenzae is 5 days; in our case, we suspect that a high bacterial inoculum, which was reflected by the severity of our patient’s illness, resulted in quicker speciation [5, 11, 12, 14].

The treatment for H. parainfluenzae endocarditis is a 4-week course of intravenous ceftriaxone in NVE and a 6-week course for prosthetic valve endocarditis (PVE). However, antibiotics alone are ineffective in patients with BIE who present with valvular dysfunction resulting in heart failure, complicated by heart block, annular or aortic abscess, destructive vegetations, persistent bacteremia or fever > 5–7 days despite appropriate antibiotic therapy, recurrent emboli or vegetations > 10 mm in length. These factors are invariably linked to a protracted course of BIE with haemodynamic instability and reduced life expectancy. Therefore, timely surgical intervention can prolong survival and improve long-term outcomes [17]. Mitral valve repair (MVr), compared to replacement, is associated with decreased in-hospital and long-term mortality. Additionally, MVr is also associated with decreased recurrence of BIE and overall need for reoperation [18]. However, the result of a MVr is dependent on the experience of the operating surgeon, the extent of valve damage, which is more severe in cases of MVr. Importantly, patients who are considered for replacement tend to be hemodynamically and clinically more unstable in comparison to those who are offered MVr.

The indications for and timing of surgery for patients with BIE have been outlined in the 2023 European Society of Cardiology (ESC), the 2019 American Association for Thoracic Surgery (AATS), and the 2020 American College of Cardiology (ACC) guidelines. Briefly, there are three main indications for surgery in acute BIE: heart failure, uncontrolled infections, and prevention of septic embolization, especially to the CNS [19,20,21].

Haemodynamic instability secondary to valvular insufficiency, characterised by severe LV dysfunction, refractory pulmonary oedema, and/or cardiogenic shock, is the most common indication for urgent surgery. Early surgical intervention is considered where the infection spreads beyond the annulus, or BIE is complicated by perivalvular abscess or fistula, heart block, or pseudoaneurysm formation. Moreover, urgent surgery may be considered in patients with large (> 10 mm), mobile vegetations with the aim of preventing potentially catastrophic embolism [19,20,21]. In a randomised study, early surgical intervention, in patients with NVE and large (> 10 mm) vegetations, was associated with significant reduction in embolic events and all-cause mortality [17].

An isolated vegetation, single scallop or leaflet involvement, less extensive valve damage are factors that favour MVr as compared with replacement. No randomised studies have compared mitral valve repair with replacement in patients with NVE. However, Feringa et al. reported that the in-hospital mortality (2.3% vs. 14.4%) and long-term survival (7.8% vs. 40.5%) were significantly lower among patients who had undergone MVr as compared with replacement. In addition, the rates of reoperation, stroke, and recurrent endocarditis was also significantly lower after MVr [18].