Vegetation Stalagmite in Left Atrium
A Variant of Infective Endocarditis
Mitral valve prolapse (MVP) is a common disorder, occurring in 4% of the general population.1 It is associated with increased risk of infective endocarditis, and antibiotic prophylaxis is suggested in those high-risk patients who have systolic murmurs.2 The vast majority of cases involve the valve and its accessory apparatus. Herein, we present an unusual location of vegetation in a patient with MVP.
A 45-year-old woman had been diagnosed with MVP 1 month before admission at our institution, after a grade III/VI pansystolic murmur with late systolic click was heard during a regular health checkup. Echocardiography illustrated myxomatous change and prolapse of the anterior mitral leaflet, with severe eccentric mitral regurgitation. Because of intermittent fever, left flank pain, and tender skin erythema of both feet, the patient visited our emergency department, where blood pressure 113/76 mm Hg, heart rate 126 bpm, and body temperature 39.5°C were noted. Blood analysis showed white blood cell count of 11 400/mm3, hemoglobin level of 9.7 g/dL, C-reactive protein level of 12.4 mg/dL, and rheumatoid factor level of 23.7 U/mL. Abdominal computed tomography demonstrated several wedge-shaped low-density lesions in the spleen and both kidneys (Figure 1). Splenic and renal infarctions were diagnosed, which was assumed to be caused by infective endocarditis. Blood culture showed bacterial growth of Staphylococcus aureus. Transthoracic and transesophageal echocardiography subsequently identified vegetations over the anterior mitral leaflet and jet lesion site (1.1×0.9 cm), the latter being a swinging seaweed in the left atrium (Figure 2A and 2B; Movie). Three-dimensional echocardiography illustrated that the vegetation in the left atrium resembled a stalagmite (Figure 2C and 2D). The patient then underwent surgical intervention with replacement of the mitral valve and resection of the large vegetation within the left atrium (Figure 3). Chordae rupture of A1 and A2 areas was noted during operation. The patient was then begun on a complete course of antibiotics with teicoplanin plus ciprofloxacin and was discharged uneventfully. Reviewing the echocardiography performed 1 month before, a small overlooked vegetation (0.5×0.2 cm) on the knock-on site of the eccentric mitral regurgitant jet was noted (Figure 4, left).
The role of jet lesions in the pathogenesis of infective endocarditis is well known.3 The classic sites are usually located just distal to an orifice between a high-pressure jet and a low-pressure sink, such as the right ventricular margin in a ventricular septal defect. In addition, a high-pressure jet may also cause a direct injury of endothelium at its knock-on site, resulting in depositions of fibrins and platelets that may serve as a nidus of bacterial growth. We have reported this case of infective endocarditis in a patient with MVP who had unusual location of vegetation, with the growth process of the vegetation in the left atrium resembling the formation of a stalagmite. Eccentric mitral regurgitation is common in patients with mitral valve prolapse, which might be complicated with vegetation on the left atrial knock-on site. This patient represents a case of definitive infective endocarditis according to modified Duke criteria,4 with typical presentation during admission, including fever >38°C, positive blood culture of typical pathogen, oscillating intracardiac mass in the path of regurgitant jets, septic emboli that caused renal and splenic infarction, positive rheumatoid factor, and predisposing heart condition of mitral valve prolapse. However, the vegetation in this patient’s first echocardiography examination 1 month before admission reported here was overlooked because of a low index of suspicion. The embolic events, splenic and renal infarction, could have been avoided if the correct diagnosis had been made earlier. The tender skin erythema on both feet during admission was probably related to septic emboli, too. We have presented this case to demonstrate the nature of the growth of stalagmite-like vegetations and to alert physicians that in patients referred for echocardiography to evaluate eccentric regurgitation jet, more attention should be paid to the knock-on sites of the eccentric jets.
The online-only Data Supplement, consisting of a Movie, is available with this article at http://circ.ahajournals.org/cgi/content/full/116/13/e359/DC1.