MRI demonstrates potential for Ross procedure follow-up

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Image courtesy of Siemens.  

The Ross procedure uses a pulmonary autograft to conduct aortic valve replacement while a homograft valve is inserted in the pulmonary position. This procedure is frequently performed in the pediatric population with satisfactory long-term survival. However, the longevity of the homograft valve in the pulmonary position is reported to be limited owing to frequent homograft stenosis. This stenosis is the main cause for reoperation after a Ross procedure.

A prospective study conducted at Leiden University Medical Center in the Netherlands utilized MR imaging in the follow-up of homograft valve and right ventricular (RV) systolic and diastolic function in patients after the Ross procedure. The results, published this month in Radiology, suggest that the use of MRI may facilitate selecting patients who need reoperation after the Ross procedure for homograft valve dysfunction.

The scientists at Leiden University examined 17 Ross patients and 17 age- and gender-matched healthy control subjects with MRI. They chose the modality over the conventionally used echocardiography because ultrasound has limitations in its assessment of RV function owing to the complex RV geometry and a reduced acoustic window with increased patient age. The MR studies were conducted on a 1.5-Tesla system (NT 15 Gyroscan Intera, Philips Medical Systems).

The researchers reported that flow dynamics across the homograft valve were assessed by using velocity-encoded MR imaging just distal to the homograft valve. In the control group, velocity-encoded MRI was performed just distal to the pulmonary valve.

The systolic RV and left ventricular (LV) function were analyzed with the MASS software application (Medis), while biventricular end-diastolic volume (EDV) and end-systolic volume (ESV) were assessed by drawing the RV and LV endocardial contours at end diastole and end systole in all sections.

“Our study findings revealed RV hypertrophy and diastolic dysfunction in patients after the Ross procedure, in the presence of mild degrees of homograft stenosis,” the authors wrote. “Systolic RV function was preserved.”

In addition, they noted that the Ross patients showed higher peak flow velocities across the homograft valve.

“Also, a direct correlation was found between homograft peak flow velocity and RV mass, but not with LV mass, illustrating the functional effect of homograft stenosis on the RV,” they observed.

In this study, cardiac MR imaging revealed mild degrees of homograft stenosis in patients after the Ross procedure, as evidenced by higher peak flow velocities across the homograft valve, according to the researchers. The results demonstrated that MRI can be used as an integrated imaging tool to monitor homograft valve and RV function in patients after the Ross procedure. As such, the modality may facilitate better selection of patients who need reoperation after this procedure for homograft valve dysfunction.

“Although MR will not replace transthoracic echocardiography as the imaging technique of choice owing to higher costs and reduced availability, it should be considered when echocardiographic imaging is difficult or when actual homograft replacement is considered,” the authors wrote.