By Michael Kellner, MD and Meghan Kelly Herbst, MD, FACEP
Chief Complaint: Fever
Clip 1 - Parasternal Long-Axis Cardiac Ultrasound
Clip 2 - Apical 4-Chamber Cardiac Ultrasound
1. What are the significant findings in the above ultrasound clips?
2. What is your approach and differential diagnosis for this pathology?
3. Can emergency physicians reliably use point of care ultrasound (POCUS) to screen for this diagnosis?
A 29-year-old male was transferred from a small community outside hospital with hypotension, renal failure, and altered mental status. His girlfriend had found him on the floor in her apartment and called 91. She reported that he was using intravenous heroin in recent weeks. One day prior, he had complained he was “not feeling well.”
The outside hospital found the patient to be complaining of abdominal pain and diarrhea. After a negative abdomen and pelvis CT scan, he was given four liters of IV fluids, prophylactically treated with 4.5g intravenous Zosyn, then transferred to a larger hospital.
On arrival, the patient was tachypneic, diaphoretic, and not responsive to verbal stimuli. His vital signs were BP 87/41, HR 101, RR 48, temp 99.2 F (tympanic), O2 sat 99% on room air. He localized to painful stimuli with incomprehensible sounds. Pupils were 6mm and bilaterally reactive to light. A systolic murmur was audible, abdominal exam elicited moaning and localization to pain in all four quadrants, and rectal exam exhibited a significant volume of gross blood. Breath sounds were clear bilaterally, and no rash or lesions were appreciated on exam of the skin, eyes, or nailbeds.
POCUS was performed, and the above images were obtained (abdominal views were negative for intraperitoneal free fluid). The ICU team was notified of the findings, vancomycin started with concern of endocarditis, a central line placed, norepinephrine started, and the patient was intubated. His lab work was significant for a white blood cell count of 16.4 thou/uL, hemoglobin of 12.7 g/dL, platelet count of 29 thou/uL, potassium of 2.7 mmol/L, creatinine of 2.5 mg/dL, BUN of 90 mg/dL, CO2 of 13 mmol/L, lactic acid of 3.1 mmol/L, and troponin of 5.93 ng/mL. On day two following admission, the patient had multiple septic emboli to extremities, and a CT of the head showed diffuse emboli to the brain. The patient expired on day three.
Though not common, infective endocarditis carries up to 18% mortality, and its diagnosis can be challenging.1 Among intravenous drug users, the incidence of endocarditis is 1-5% per year.2 While the tricuspid valve is most commonly affected in this population, the mitral and aortic valves follow closely behind, with approximately equal frequency noted in one study.2,3 Emergency physician-performed POCUS echocardiography has already been established for detecting pericardial effusion, estimating left ventricular ejection fraction, and recognizing right heart strain.4 However, the diagnosis of endocarditis by emergency physicians using POCUS (and confirmed by cardiology performed echocardiography) has also been reported in the literature.5-7
In 2016, intensivists and emergency physicians summarized guidelines for the appropriate use of cardiac ultrasonography of critically ill patients and suggested patients with suspected endocarditis be screened with POCUS by operators of all levels of training. The rationale was that a physician with even a basic level of ultrasound training may be able to recognize obvious vegetations, which could help to identify the diagnosis quickly in high-risk patients. This recommendation is not strong, however, secondary to low quality evidence available at this time.8
In this patient, formal echocardiography confirmed the presence of a vegetation on the mitral valve leaflet (indicated in the image below), as well as on the aortic valve. While the POCUS did not identify the aortic valve vegetation, it prompted suspicion for endocarditis when treating providers were previously distracted by his abdominal pain.
Answers to Questions
1. Clips 1 and 2 demonstrate a mobile mitral valve mass consistent with a vegetation secondary to endocarditis in this young patient with fever. The classic finding is visualization of an irregularly shaped echogenic mass, usually on the upstream side of the valve with independent oscillating movement. Associated regurgitant flow may also be appreciated by applying color Doppler over the valve.
2. To assess for endocarditis, the examiner should perform a thorough POCUS of the heart to visualize the aortic, mitral, and tricuspid valves from multiple angles. The aortic valve may best be appreciated in a parasternal long view or apical 5-chamber view, the tricuspid valve may best be appreciated in a subxiphoid or apical 4-chamber view, and the mitral valve may best be appreciated in a parasternal long view or apical view. In each view, fan through the valve to identify a mobile, echogenic mass tethered to, but moving independently from, the valve itself. The differential diagnosis for an echogenic mass on a cardiac valve includes vegetation, tumor, thrombus, or artifact.9
3. Several case reports have demonstrated the usefulness of POCUS performed by emergency physicians for the diagnosis of endocarditis.5-7 These reports highlight the expedited management of septic patients with relatively large vegetations discovered on point-of-care cardiac ultrasound. One study suggests approximately 25% of vegetations less than 5mm, and 70% vegetations 6-10mm in size can be visualized.10 Another study found that transthoracic echocardiography is 84% sensitive for vegetations greater than 10mm in size.11 The available research is limited, and prospective studies to support the routine use of point-of-care cardiac ultrasound for endocarditis are lacking.
Emergency physicians using POCUS can identify and expedite treatment of endocarditis when vegetations are visualized, but cannot exclude this process after a negative scan. The ability to rapidly and effectively rule in a potentially dangerous condition like endocarditis, which can have varied and vague presentations, exemplifies the utility of POCUS to the emergency medicine provider.