Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.

A 58-year-old woman is hospitalized for acute left-sided flank pain. She has had fever and night sweats for 1 month and a 9.1-kg (20-lb) weight loss over 6 months.

On physical examination, temperature is 37.7 °C (99.8 °F), blood pressure is 135/88 mm Hg, pulse is 88/min, and respiration rate is 18/min. Heart sounds are normal. There is an early diastolic low-pitched sound after the S₂ with a diastolic murmur at the apex. There is tenderness of the left costophrenic angle. The abdomen is soft with normal bowel sounds and no tenderness. She does not have rash or petechiae, splinter hemorrhages, or Janeway lesions. Funduscopic examination is normal.

Laboratory studies:

Leukocyte count	14,000/uL (14.0 × 109/L) with no left shift
Creatinine	1.3 mg/dL (99.2 µmol/L)
Blood urea nitrogen	14 mg/dL (5.0 mmol/L)
Urinalysis	Microscopic hematuria, no crystals, negative for protein

Twelve-lead electrocardiography shows normal sinus rhythm. Echocardiogram shows a 5- by 4-cm left atrial echogenic mobile globular mass attached to the atrial septum with diastolic protrusion into the left ventricle. Abdominal radiograph shows a normal gas pattern and no renal calculi. Contrast-enhanced CT scan of the abdomen and pelvis shows a wedge-shaped hypoperfusion defect in the upper pole of the left kidney. Mean transmitral valve inflow gradient is 15 mm Hg. Three sets of blood cultures are negative for growth after 5 days.

Which of the following is the most appropriate treatment?

A) Cardiac surgery for resection of mass
B) Mitral valve replacement
C) Systemic anticoagulation with heparin
D) Vancomycin and tobramycin

MKSAP Answer and Critique

The correct answer is A) Cardiac surgery for resection of mass. This item is available to MKSAP 15 subscribers as item 18 in the Cardiology section. More information about MKSAP 15 is available online.

This patient has evidence of a systemic embolism to the left kidney causing flank pain and hematuria. No evidence of renal calculi is present. The history of fever, night sweats, and weight loss is consistent with a systemic illness. Echocardiography shows a left atrial mass with features consistent with a tumor, as evidenced by attachment to the atrial septum, echogenic texture, mobility, and protrusion into the mitral valve orifice obstructing inflow. This mass is most likely a left atrial myxoma, the most common tumor type of the left atrium. A left atrial myxoma does not metastasize to other organs, but it has significant associated morbidity. Left atrial myxoma causes fever, night sweats, and weight loss, and may embolize to the brain or other organs such as the kidney, as seen in this patient. Cardiac surgery to remove the left atrial mass is the best treatment and would be curative if the mass is a benign tumor. A primary malignant tumor is also a possibility, but surgical removal would also be the correct approach.

Echocardiography in this patient shows severe transmitral valve obstruction with a mean gradient of 15 mm Hg. Rheumatic mitral stenosis on auscultation can cause an early high-pitched diastolic sound (an opening snap) and a diastolic decrescendo murmur, similar to the findings in this patient. However, the opening sound in this patient is a low-pitched sound associated with a left atrial myxoma, a so-called “tumor plop.” Furthermore, the patient’s echocardiogram is inconsistent with primary mitral valve disease. The diastolic murmur in this patient is secondary to obstruction of the mitral valve orifice by the tumor, effectively a functional mitral stenosis. Thus, the appropriate cardiac surgery is removal of the left atrial mass rather than mitral valve replacement.

The left atrial mass is highly unlikely to be a thrombus given the presence of sinus rhythm and not atrial fibrillation. Systemic anticoagulation with heparin is not indicated.

The presentation of fever, night sweats, and weight loss is typical of endocarditis, and thus this diagnosis should be considered. However, blood cultures failed to confirm bacteremia, and echocardiography showed no vegetations. Empiric antibiotic therapy with vancomycin and tobramycin for presumed endocarditis in this patient who is hemodynamically stable and has an alternative explanation for her symptoms is not warranted.

Key Point

• Surgical removal of left atrial myxoma is curative and is the appropriate primary treatment.

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