The 'mill-wheel' murmur and computed tomography of intracardiac air emboli

Abstract

The 'water-wheel' or 'mill-wheel' murmur is classically associated with large intracardiac air emboli and described as a "characteristic splashing auscultatory sound due to the presence of gas in the cardiac chambers." We used 64-slice computed tomography (slice thickness, 0.5 mm; revolution time, 400 msec) and 3D fly-through software imagery to capture previously unreported intracardiac air-blood interface dynamics associated with this murmur and ineffective right ventricular contraction in a porcine model.

Figure 1.

Fly-through (lower left panel) view and planar images (upper left, upper right, and lower right) of an air embolus within the right ventricle, demonstrating reflected waves at the air–blood interface. Arrows demonstrate fluid-surface features consistent with bubbles within the right ventricle. A, anterior; P, posterior; L, left; R, right; S, superior; I, inferior.

Figure 2.

Two rotated views of air (bubble) accumulation in the right ventricle (RV), right atrium (RA), pulmonary artery (PA), and extracardiac thoracic veins (tubular).