Right-Sided Infective Endocarditis

1. Case Discussion

This section is meant to put the case into the context of similar cases, to explain specific treatment decisions, and to share additional relevant information that is not included in the case presentation.

Right-sided Infective Endocarditis (RSIE) represents 5–10% of all IE cases, making it a rare clinical entity.¹ It is most commonly found in patients with a history of intravenous drug use; however, it is also associated with patients on dialysis, or have intra-cardiac devices, congenital heart diseases or immunocompromised states.¹ The diagnosis of RSIE is often delayed because its signs and symptoms are relatively different than LSIE which is the specific target of the modified Duke's criteria.² The patient presented here satisfied both of the major criteria of positive blood cultures and endocardial involvement.

Common symptoms include cough, hemoptysis, dyspnea, chest pain and persistent fever. The primary diagnostic modalities are echocardiography and blood cultures. The main anatomic structure affected is the tricuspid valve (82%) and Staphylococcus aureus is the predominant organism involved (60-90%).³ RSIE has a better prognosis (i.e. lower mortality of 3-30%) than LSIE (27-38%) given its lack of systemic circulatory involvement which can lead to invasion and abscess formation.¹

The mainstay of medical treatment is antibiotics; however, if refractory, surgery is indicated in cases of: right-sided heart failure (due to severe tricuspid regurgitation), persistent bacteremia (i.e. greater than 7 days) refractory to culture-directed antibiotics, and tricuspid valve vegetations greater than 20 mm in length.¹ While the patient presented here was only on day two of antibiotics, he did have a vegetation that was 29 mm in length which warranted surgical exploration.

This patient was triaged as a COVID rule-out given he was known positive with chills, shortness of breath, recently productive cough and vital signs confirming hypoxia, tachycardia, tachypnea and fever. Due to COVID's widespread nature currently in New York, physicians may tend to exhibit an anchoring bias by fixating on COVID when a patient's symptoms can be explained by an alternate diagnosis. Upon closer re-examination, this patient did have an intravenous drug use history, track marks and an echo showing a valvular vegetation - all factors attributed to classic endocarditis.

2. Visual Case History

This is the body of the submission. The case discussion presents a description of the clinical scenario associated with the figure(s) / video(s). This should be a maximum of 1,000 words.

A 31 year-old male recently positive for SARS-CoV-2 presented to the ER with shortness of breath. He described his dyspnea as exertional, progressively worsening over the last week and associated with chills, pleuritic chest pain and new-onset blood tinged sputum. The patient's initial vital signs were a blood pressure of 102/61 mm Hg, heart rate of 119 beats per minute, respiratory rate of 22 per minute, temperature of 100.6º and an oxygen-saturation of 88% on room air. He was triaged to the ER's COVID unit and placed on two liters of nasal cannula where he improved to 94%. On examination, the patient had bibasilar diminished breath sounds with tachypnea but no other evidence of respiratory distress and tachycardia with a grade II systolic murmur of which he had no known history.

An EKG showed sinus tachycardia but was otherwise normal and a portable chest x-ray was negative for bilateral infiltrates. The patient complained of persistent shortness of breath and pleuritic chest pain even while on supplemental oxygen so it was increased to four liters and a bedside ultrasound was done which showed a large tricuspid valve vegetation.

The patient's laboratory studies further revealed a low sodium of 117 mEq/L with a normal glucose of 112 mg/dL, elevated creatinine of 4 mg/dL with no known baseline, elevated troponin of 0.21 ng/mL, anion gap of 16 mEq/L, elevated white blood cell count of 18’000/µL with 33% bands, low platelets of 70’000/µL and an initial lactic acid of 1.6 mmol/L. During the encounter, the patient's mother volunteered that he had a history of heroin use and upon re-examination, subtle track marks were appreciated on the dorsum of both hands.

A formal echocardiogram verified a large, mobile vegetative mass on the tricuspid valve's anterior leaflet measuring 2.9 by 1.5 cm that extended into the right atrium and ventricle with moderate regurgitation. A CT chest without contrast showed multiple, bilateral, wedge-shaped nodular opacities that measured 4.5 by 2.5 cm in the right lower lobe posteriorly and 1.3 by 1.1 cm in the left upper lobe laterally. Given the patient's clinical context and ultrasound results, the nodules were determined to most likely be septic emboli in origin.

The patient was started on broad spectrum antibiotics and a nephrology consult recommended conservative hydration for the AKI and hyponatremia. He was admitted to the ICU where on day two, blood cultures grew two out of two Gram-positive cocci. Despite being on vancomycin for 48 hours, he was persistently febrile, hypotensive, tachycardic and oxygen dependent. He was evaluated by cardiology who recommended transfer and surgical evaluation at a tertiary care facility given the size of the vegetation and its mobility, the fever despite culture-directed antibiotics and thus the likelihood of further decompensation. The family agreed and the patient was transferred accordingly. Questions and Answers with a Brief Rationale True & false and / or multiple-choice questions

Questions and Answers with a Brief Rationale True & false and / or multiple-choice questions

Question 1

Question Type True / False

Question Text – Right sided infective endocarditis portends a poorer prognosis than left sided infective endocarditis.

Answer Options

• a)True
• b)False

Correct Answer = False

Explain why this is the correct answer (max. 500 characters)

RSIE actually has a better prognosis (i.e. lower mortality of 3-30%) than LSIE (27-38% mortality) given its physiologically predicted sequelae. Because the right side of the heart supplies pulmonary rather than systemic circulation in a normal anatomical heart, this will protect RSIE patients from downstream systemic invasion and abscess formation which are classically associated with LSIE and greater mortality rates.

Question 2

Question Type multiple choice

Question Text Which of the following is NOT an indication of surgical treatment of right sided infective endocarditis?

Answer Options

• a)right-sided heart failure (due to severe tricuspid valve regurgitation),
• b)persistent bacteremia (i.e. greater than 7 days) refractory to culture-directed antibiotic treatment
• c)tricuspid valve vegetations greater than 30 mm in length

Correct Answer = C

Explain why this is the correct answer (max. 500 characters)

While the mainstay of infective endocarditis treatment is antibiotics, there are three primary indications where surgery is indicated. In the above question, both A & B are true. For C however, tricuspid valve vegetations greater than 20 mm in length is an indication for surgery, not 30 mm.

Figure. 1, Figure. 2, Figure. 3

Figure. 1.

Transthoracic echocardiogram (TTE) showing labeled tricuspid vegetation on four-chamber apical view during systole.

Figure. 2.

Transthoracic echocardiogram (TTE) showing labeled tricuspid vegetation on four-chamber apical view during diastole.

Figure. 3.

CT chest without contrast showing a transverse section of bilateral lung bases with labeled and multiple wedge-shaped consolidations concerning for septic emboli.

Clip. 4. Video clip of TTE showing labeled tricuspid vegetation on four-chamber apical view.

Declaration of Competing Interest

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