Bicuspid aortic valve

To the Editor:

We read with great interest the 'article by Hager et al (October 2004), (1) who report comparable usefulness of helical CT (HCT) scanning and cardiovascular MRI (CMIR) for the noninvasive evaluation of the thoracic aorta in patients with aortic coarctation. (1) However, CMR not only allows detailed imaging of the entire aorta, but it also allows quantification of parameters of left ventricular function, aortic valve function, and collateral circulation in aortic coarctation patients. Steady-state free precession CMR is the most accurate imaging modality for measuring ventricular volumes, owing to its high accuracy and good reproducibility. It allows calculation of left ventricular systolic, diastolic, stroke volumes, and ejection fraction. Assessment of left ventricular mass--a parameter with prognostic significance--by CMR has also been shown much more reproducible and accurate than echocardiography, and has an excellent correlation with postmortem ventricular weights. (2) CMR velocity mapping can be used to quantify the degree of stenosis and/or regurgitation of frequently found bicuspid aortic valves. Insight in the functional significance of native aortic coarctation or residual aortic stenosis can be gained by assessing the recruitment of collateral circulation by comparing the flow volume through the aorta just distal to the stenosis with the flow volume through the descending aorta at the level of the diaphragm, (3) So, in agreement with Therrien et al, (4) we believe that for the postoperative assessment of aortic coarctation patients, CMR is very much the preferred imaging modality and that aortic coarctation patients should be cared for in a specialized center with experience and appropriate CMR imaging facilities.

Joris W. J. Vriend, MD

Thomas Oosterhof MD

Barbara Mulder, MD

Academic Medical Center

Amsterdam, the Netherlands

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal. org/misc/reprints.shtml).

Correspondence to: Joris W. J. Vriend, MD, Academic Medical Center, B2-216, Department of Cardiology, Meibergdreef 9, 1105 AZ Amsterdam, the Netherlands; e-mail: J.W.Vriend@ amc.uva.nl

REFERENCES

(1) Hager A, Kaemmerer H, Leppert A, et al. Follow-up of adults with coarctation of the aorta: comparison of helical CT and MRI, and impact on assessing diameter changes. Chest 2004; 126:1169-1176

(2) Bottini PB, Carr AA, Prisant LM, et al. Magnetic resonance imaging compared to echocardiography to assess left ventricular mass in the hypertensive patient. Am J Hypertens 1995; 8:221-228

(3) Steffens JC, Bourne MW, Sakuma H, et al. Quantification of collateral blood flow in coarctation of the aorta by velocity encoded cine magnetic resonance imaging. Circulation 1994; 90:937-943

(4) Therrien J, Thorne SA, Wright A, et al. Repaired coarctation: a "cost-effective" approach to identify complications in adults. J Am Coll Cardiol 2000; 35:997-1002

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