The existence of a left-sided third mogul positioned just below the left mainstem bronchus is never normal. If present, it most commonly represents a prominent left atrial appendage due to left atrial enlargement. Less commonly, a third left mogul may be caused by a sinus of Valsalva aneurysm or an abnormal right ventricular outflow tract. An abnormal right ventricular outflow tract may be caused by a corrected transposition, tetralogy of Fallot, a single ventricle with a rudimentary chamber, or Ebstein’s anomaly. flovent inhaler
In patients who have a third mogul present, further analysis of the mediastinal contours can often assist in the roentgenographic differential diagnosis. Patients with an enlarged left atrial appendage tend to have a prominent second mogul. In contrast, patients with a sinus of Valsalva aneurysm or an abnormal right ventricular outflow tract typically have a small second mogul. Among the conditions associated with a third mogul due to an abnormal ventricular outflow tract, patients with Ebstein’s anomaly have a small left first mogul and a large right fourth mogul, while those with the tetralogy of Fallot have a prominent first mogul. Further considerations based on the presence or absence of pulmonary vascular engorgement can additionally aid in differential diagnosis.
The presence of a third mogul and a small second mogul in the present patient combined with the physical findings suggested the diagnosis of an unruptured sinus of Valsalva aneurysm with aortic valvular insufficiency. An echocardiogram showed the aneurysm (Fig 3) in addition to the findings of clinically important aortic insufficiency, normal left ventricular systolic function, and normal left atrial size. Results of the clinical evaluation suggested that the sinus of Valsalva aneurysm prevented proper closure of the aortic valve and thereby caused aortic insufficiency, left ventricular volume overload, and left ventricular failure. An initial dramatic improvement with diuresis and afterload reduction suggested that the patient might do well with medical management. Recurrent symptoms, however, necessitated aneurysm resection and prosthetic replacement of the aortic valve. After recovery from surgery and resolution of cardiac failure, the Cheyne-Stokes respirations resolved, and the third mogul disappeared (Fig 4). As demonstrated by the present patient, integration of clinical findings with the observations from skiagraphy can result in early diagnosis and expedient therapy.
Figure 3. Echocardiograms of normal and abnormal findings for comparison. Upper, Two-dimensional echocardiogram from the parasternal short axis view demonstrates normal anatomy of the aortic valve. Arrowheads point to three leaflets; a=aortic valve orifice during systole; LA=left atrium; RA=right atrium; RV=right ventricle. Lower, Two-dimensional echocardiogram demonstrates a left sinus of Valsalva aneurysm(s). Abbreviations same as upper.
Figure 4. Postoperative chest roentgenogram reveals the disappearance of the third mediastinal mogul.