Mural Right-Sided Infective Endocarditis in Adults

Infective endocarditis (IE) is a life-threatening infection that affects the endothelial surface of the heart, predominantly of the valves.¹ However, the infection may also involve the endothelium of heart chambers, a condition known as mural infective endocarditis (MIE). MIE appears to be rare, affecting fewer than 1% of patients with IE.² Mural right-sided infective endocarditis (M-RSIE) is presumably less common, with endovascular devices serving as key predisposing factors. The frequency and severity of M-RSIE in cases lacking endovascular devices remain unknown, as does the role of cardiac surgery in managing nonvalvular forms of right-sided involvement. We therefore conducted a systematic review to investigate the clinical and microbiological characteristics, management, and prognosis of M-RSIE.

• •What is the clinical question being addressed? This systematic review aimed to characterize the microbiology, diagnostic and therapeutic management strategies, and outcomes of M-RSIE in patients without endovascular device-related infection sources.
• •What is the main finding? M-RSIE is a rare infection affecting primarily younger adults, usually involving the right ventricle and caused by Staphylococcus aureus; despite frequent embolic complications and surgical intervention requirements, mortality was relatively low.

A systematic review of published studies of adults (≥18 years) diagnosed with M-RSIE without valvular involvement was conducted following the Preferred Reporting Items for Systematic reviews and Meta-Analyses 2020 guidelines. Studies in non-English language were excluded. Patients were excluded if they had concurrent left-sided involvement, concurrent right-sided cardiac valve involvement (eg, tricuspid, pulmonary, Thebesian, Eustachian valves, or Chiari network), cardiovascular implantable electronic device, or central venous catheters. Reports were considered eligible if they fulfilled the following criteria: 1) definite IE according to modified Duke criteria³; 2) MIE, a cardiac infection that involved the mural endocardium without involvement of valves^1,2; 3) injection drug use (IDU), considered as the self-administration of substances delivered by needle; 4) congenital heart disease (CHD), as an abnormality in the heart's structure present at birth.

Medical literature was searched by an expert librarian (D.G.) for the following concepts: endocarditis, right atrium, right ventricle, and nontricuspid/nonvalvular/mural. Search strategies were created using a combination of keywords and standardized index terms. Covidence software (Veritas Health Innovation) was used to manage the study selection process. Two independent reviewers (G.C., L.B.) evaluated titles, abstracts, and full texts according to predefined inclusion and exclusion criteria. Discrepancies were resolved through consensus.

Of the 310 publications identified, 33 underwent full-text review. After excluding 16 studies based on the prespecified eligibility criteria, 17 studies with 19 adult patients were included in the final analysis. All but 2 articles were single case reports. Table 1 summarizes the main findings. Pooled analysis showed a median age of 38 years (IQR: 23-47 years), with male predominance (11; 58%). Two (10.5%) patients had CHD, 2 (10.5%) had IDU, and 2 (10.5%) were orthotopic heart transplantation (OHT) recipients; 5 (26.3%) had other predisposing conditions, and 8 (42%) patients had no risk factors. The predominant pathogen was Staphylococcus aureus (8/42%; including 2 methicillin-resistant S aureus). Remaining cases were distributed among Streptococcus spp. (4/21%) negative blood cultures (4/21%) and Aspergillus spp. in 3 (16%) immunocompromised patients (2 OHT recipients and 1 patient on chronic corticosteroid therapy). In these 3 cases, a microbiological diagnosis required cardiac tissue sample testing. Among patients with available information, clinical signs of sepsis were common (11/58%), whereas heart failure was rare (1/5%). The most frequent site of involvement was the right ventricle (right ventricle: 12/63%; right atrium: 7/37%). In 12 (63%) cases, a transthoracic echocardiography (TTE) was sufficient for diagnosis, whereas a transesophageal echocardiography (TEE) was essential in 5 (26%) patients, 3 (60%) of whom had atrial involvement. In 5 (26%) cases, additional imaging techniques were utilized (1 case: computed tomography; 1 case: computed tomography plus cardiac magnetic resonance imaging [MRI]; and 3 cases: cardiac MRI), raising diagnosis in all instances. Septic pulmonary emboli were observed in 12 (80% of those with available information) cases. Nine (47%) patients underwent cardiac surgery (most cases involved tumorectomy/vegetectomy, with 1 case requiring TV replacement), while percutaneous mechanical aspiration was performed in 1 case. One patient died as a complication of M-RSIE. Follow-up information postdischarge was available in 7 (37%) patients with a median follow-up duration of 8 months (IQR: 6-12 months).

Table 1.

Summary of Published Cases

First Author, Year	Design	Follow-Up (Months)	Age/Sex	CHD	IDU	Microbiology	Sepsis	Heart Failure	Heart Chamber	TTE	TEE	Septic Pulmonary Emboli	Procedure	In-Hospital Mortality
Wu et al. Heart & Lung. 2018;47(4):366-370.	CR	-	40/M	No	No	MSSA	Yes	Yes	RV	Pericardial effusion with diastolic collapse of the RV. Hyperechoic mass on the right ventricular surface of the interventricular septum	Not done	Yes	No	No
Tomaszuk. Kardiol Pol. 2011;69(6):587-589.	CR	12	20/ND	No	No	MSSA	Yes	No	RV	Longitudinal intracardiac mass (50 × 15 mm) in the RVOT, attached to the RV free wall and protruded into the pulmonary artery	Not done	Yes	Cardiac surgery	No
Teshome. JInvestMed. 2019;67(2):398-399.	CR	-	52/F	No	Yes	MRSA	Yes	No	RV	Negative	RV mural endocarditis attached to the moderator band and extending to the RVOT	Yes	No	No
Rajbanshi et al. Mayo Clin Proc. 2012;87(9):926-928.	CR	6	52/M	No	No	Aspergillus species	No	No	RV	Mass (45 × 21 mm) on the anterior free wall of the RV extending to the apex	Not done	No	Cardiac surgery	No
Qadir. J Hosp Med. 2023;18 Suppl 1:S711-S712.	CR	-	28/F	No	Yes	MRSA	Yes	No	RA	Large pedunculated echogenic mass (25 × 3 mm) in the RA attached to the free wall, separate from the TV	A 27 mm mobile, linear echodensity in the RA, attached to the wall	Yes	No	No
Matsuzoe. J Cardiol Cases. 2023;27(2):63-66.	CR	-	40/M	No	No	MSSA	No	No	RV	Severe TR and floating vegetation near the free wall of the RV (18 × 8 mm)	Severe TR with posterior leaflet prolapse due to torn chordae and PFO	Yes	Cardiac surgery	No
Lin. Heart Lung Circ. 2010;19(9):566-571.	CR	-	21/M	VSD	No	Negative BC	No	No	RV	VSD with left-to-right shunt. Large mobile echo density in the RVOT and VSD	Large vegetation (41 × 16 mm), attached to the free wall near the RVOT. A separate lesion was seen attached to the RV side	Yes	No	No
Lee. Cardiology. 2014;129(1):65-68.	CR	-	32/F	VSD	No	VGS	No	No	RV	A 5-mm-sized defect in the muscular part of the IV septum with left-to-right shunt. Echogenic and mobile mass (10 × 9 mm) attached to the RV free wall near the RVOT	Confirmatory	No	Cardiac surgery	No
Köz . Anadolu Kardiyoloji Dergisi. 2009;9(5):E15.	CR	-	32/M	No	No	Negative BC	Yes	No	RV	Mass located in RV apex (28 × 38 mm).	Not done	No evaluation	Cardiac surgery	No
Koshy. Circulation. 2009;119(6):899–901.	CR	12	40/M	No	No	MSSA	Yes	No	RV	Bilobed, oscillating, RV mass (20 × 15 mm) with peduncle arising from the anterior end of the moderator band	2-mm PFO. The mass was visualized in a modified 4-chamber midesophageal view.	Yes	Cardiac surgery	No
Harada. JInfecChem. 2024;30(11):1179-1181.	CR	-	60/F	No	No	S dysgalactiae	Yes	No	RA	No vegetation	Mobile mass on the fossa ovalis in the RA (17 × 9 mm).	No evaluation	No	No
Fagundo. Cureus. 2025;17(10):e94546.	CR	-	65/F	No	No	S intermedius	Yes	No	RA	Global hypokinesis and mild diastolic dysfunction. No valvular vegetations	Large multilobular RA mass as well as an interatrial shunt, likely a PFO. No valvular vegetations	No	PMA	No
Diaz-Navarro. Eur Heart J Case Rep. 2022;6(9):ytac376.	CR	60	20/M	No	No	Negative BC	Yes	No	RV	Multiple mobile masses in the RV arising from the moderator and other RV muscular bands (largest 20 × 10 mm). Mild TR	Not done	Yes	Cardiac surgery	No
Ariyoshi. J Community Hosp Intern Med Perspect. 2016;6(2):31113.	CR	2	38/M	No	No	S agalactiae	No	No	RV	No vegetation	Large, complex, multilobar, highly mobile echodensity seen in the RV (up to 40 mm) attached to chordae tendineae. Normal valves.	Yes	No	No
Ak. Interact Cardiovasc Thorac Surg. 2009;8(4):498–500.	CR	-	24/M	No	No	Negative BC	Yes	No	RV	Large (32 × 27 mm), slightly mobile and solid mass attached to the apical part of the RV septum. TV and PV morphologically normal. Moderate TR	Not done	Yes	Cardiac surgery	No
Wilson. Heart Lung Circ. 2016;25(10):e119-21.	CS	-	22/M	No	No	MSSA	No	No	RA	A 10 mm mass in the RA attached to the interatrial septum above the TV annulus without valvular abnormalities.	Not done	Yes	No	No
Wilson. Heart Lung Circ. 2016;25(10):e119-e121.	CS	6	20/M	No	No	MSSA	Yes	No	RA	Not reported	Vegetation at the junction of the RA and superior vena cava, and a large cavity around the TV annulus and aortic root extending up to the superior vena cava with no valvular involvement.	Yes	No	No
Martínez-Sellés. Int J Cardiol. 2021;328:158-162.a	CS	-	53/F	No	No	A fumigatus	-	-	RA	Vegetation in RA	Vegetation in RA	No evaluation	Cardiac surgery	No
Martínez-Sellés. Int J Cardiol. 2021;328:158-162.a	CS	8	42/F	No	No	A fumigatus	-	-	RA	Vegetation in RA	Vegetation in RA	No evaluation	No	Yes

A fumigatus = Aspergillus fumigatus; BC = blood culture; CHD = congenital heart disease; CIED = cardiovascular implantable electronic device; CR = case report; CS = case series; IDU = injection drug use; IE = infective endocarditis; IV = interventricular; MRSA = methicillin-resistant Staphylococcus aureus; MSSA = methicillin-susceptible Staphylococcus aureus; ND = not defined; PFO = patent foramen ovale; PMA = percutaneous mechanical aspiration; PV = pulmonary valve; RA = right atrium; RV = right ventricle; RVOT = right ventricular outflow tract; S = Streptococcus (agalactiae/dysgalactiae/intermedius); TEE = transesophageal echocardiography; TTE = transthoracic echocardiography; TR = tricuspid regurgitation; TV = tricuspid valve; VGS = viridans group streptococci; VSD = ventricular septal defect.

^a16 patients excluded: 11 valvular IE, 3 CIED-related IE, and 1 left mural IE.

This systematic review supports the notion that M-RSIE is a rare condition affecting mainly younger adults, most commonly caused by S aureus and involving the right ventricle. TTE enabled diagnosis in about two-thirds of cases, whereas TEE was particularly valuable for right atrial involvement; despite the frequent occurrence of septic pulmonary embolism and the need for surgery, overall mortality was low.

The scarcity of identified cases suggests that M-RSIE is rare. The largest published case series to date described 37 cases of MIE affecting both sides of the heart (0.7% of the series).² In that study, approximately 0.5% of the total IE cases reported were M-RSIE. Also noteworthy is the younger age of adult patients: the association with IDU, CHD, and OHT recipients may skew the data toward a younger population. The most frequently isolated pathogen was S aureus, underscoring the characteristic virulence of this pathogen. The proportion of cases with blood culture-negative endocarditis (BCNE) was high (>20%), though consistent with that reported in large series. Four cases with BCNE had prior exposure to antibiotics, the leading cause of BCNE.⁴ Three M-RSIE cases involving immunocompromised patients had IE caused by Aspergillus spp., a high proportion but consistent with that reported.² Overall, the predominance of aggressive microorganisms may explain why sepsis was a common clinical presentation. Conversely, the absence of valvular damage meant that heart failure was exceptional.

The predominant site of involvement was the right ventricle. The exclusion in our study of cases associated with central venous catheters and cardiovascular implantable electronic devices explains this predilection for the ventricular cavity, subjected to higher pressure and greater endothelial stress. Furthermore, this cavity receives regurgitant jets and contains anatomical structures, such as the moderator band or the right ventricular outflow tract, that could promote turbulent flow.

TTE was useful for diagnosis in two-thirds of the patients. While reporting bias favoring more severe or late-diagnosed cases may explain this strong performance of TTE, it may be due to its limitations in evaluating the right atrium.⁵ Additional imaging techniques were utilized with confirmatory results, with a remarkable usefulness of cardiac MRI in the evaluation of intracavitary vegetations.

A noteworthy finding is that nearly half of the patients underwent cardiac surgery. While valvular damage and heart failure constitute the primary indication for surgery in left-sided IE, this is not the case in right-sided IE, where surgical intervention is exceptional and where source control and prevention of embolisms may serve as main indications.

Lastly, despite the apparent severity, the observed mortality of 5% was low. While reporting bias favoring successful outcomes cannot be overlooked, we must acknowledge that we are dealing with right-sided IE occurring in generally younger adults without valvular involvement.

The systematic review has several limitations. First, there is an inherent risk of selective reporting bias from case reports. Furthermore, the included manuscripts present significant shortcomings in follow-up data, commonplace in retrospective investigations. Finally, the small number of cases identified in our review confines our ability to conduct valid comparisons.

To conclude, M-RSIE without intracardiac devices is a rare condition affecting younger adults both with and without clear predisposition. S aureus was the most common pathogen, with fungal cases observed in immunosuppressed patients. Ventricular involvement predominated, with TTE being useful for diagnosis in most patients. Cardiac surgery for source control and/or septic pulmonary embolism prevention was common, and despite the severity of the clinical presentation, the overall mortality rate was low.

Funding support and author disclosures

Dr Cuervo has received mobility grants from the Hospital Clínico de Barcelona, the Spanish Society of Infectious Diseases and Clinical Microbiology (Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica: SEIMC), and the Biomedical Research Network Center of Infectious Diseases (Centro de Investigación Biomédica en Red / Enfermedades Infecciosas: CIBERINFEC). Dr Miró has received a personal 80:20 research grant from the Institut d’Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain, during 2017-26. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.