Further to Kenny et al's response to our editorial view (1) of their original paper (2), we completely agree that long-term surveillance after coarctation stenting is required to detect complications but would re- iterate that this must also apply to balloon dilation and surgical repairs too. Given that these patients will need life-long follow up and continued imaging it is important that such imaging carries a low risk to the patient and is sensitive to vascular complications that may arise both at the site of repair and at the aortic valve and ascending aorta.

While MRI scanning cannot detect circumferential stent fracture, it occurs in the setting of a resistant lesion and by its very occurrence is accompanied by a recurrent gradient that is detectable on echocardiography or MRI velocity scanning. Current MRI imaging sequences are now able to provide good wall definition even with stainless steel stents and as MRI becomes more widely available should allow a reduction in the need for CT scanning in this setting just to detect aneurysm formation. We use CT now only when urgency dictates and MRI is not readily available for logistic reasons.

As Kenny et al acknowledge, the assessment of coarctation by MRI scanning is comprehensive and without any risks from radiation and we believe should become the preferred modality supplemented by interval echocardiography and clinical examination.

1. Rosenthal E, Bell A. Optimal imaging after coarctation stenting. Heart 2010; 96:1169-71.

2. Chakrabarti S, Kenny D, Morgan G, et al. Balloon expandable stent implantation for native and recurrent coarctation of the aorta : prospective computed tomography assessment of stent integrity, aneurysm formation and stenosis relief. Heart 2010; 96:1212-16.

Conflict of Interest:

None declared

To the Editor: We thank Dr Rosenthal and Bell for their insightful editorial comments 1 relating to our study. 2 There is little doubt that until we have longer follow-up on the incidence of potential adverse events following coarctation stenting, some form of advanced imaging is required and this is endorsed by ongoing large follow-up studies. 3 Although we agree that with specific imaging techniques MRI may provide information regarding complications particularly in newer platinum stents, there are numerous reports demonstrating almost complete loss of signal with stainless steel stents when imaging with MRI. 4 Although the authors have demonstrated a case where protrusion of the aortic wall is seen with MRI following a stainless steel stent, smaller aneurysms have been missed (personal communication Professor Andrew Taylor). In many countries including the US, platinum stents are not available and stainless steel stents are almost exclusively used. MRI as the authors point out is less available than CT and this has implications for patient follow-up requiring patients to travel to a specialised centre for imaging and this has had implications on patient compliance in our region. As the authors also point out MRI will not detect stent fractures, however it is not true that it is only complications of these that require intervention. It is our practice to re-stent in the setting of a circumferential stent fracture and this may be missed with MRI. Also the ability of MRI to demonstrate increased flow velocity distal to the stent is very dependent on where the restenosis occurs within the stent and where the velocity sample is acquired below the stent. CT offers excellent in-stent imaging allowing pre-procedural planning of further intervention and limiting unnecessary catheter procedures. It is beyond argument that MRI offers more functional data on left ventricular dynamics however this requires time and cost and is not usually indicated in the setting of specific post-stent follow-up imaging. We fully accept the radiation doses associated with CT and the authors are correct to point out that this dose is cumulative, however the ultimate goal of a screening tool should be to provide sensitive and specific data to guide further management. MRI may provide this in selected cases but it is questionable whether it will do so over the general population and over the range of stents used in coarctation of the aorta and thus we continue to advocate the use of CT with continued efforts to minimise radiation doses.

References:

1. Rosenthal E, Bell A. Optimal imaging after coarctation stenting. Heart 2010; 96:1169-71.

2. Chakrabarti S, Kenny D, Morgan G, et al. Balloon expandable stent implantation for native and recurrent coarctation of the aorta : prospective computed tomography assessment of stent integrity, aneurysm formation and stenosis relief. Heart 2010; 96:1212-16.

3. Forbes TJ, Moore P, Pedra CA, et al. Intermediate follow-up following intravascular stenting for treatment of coarctation of the aorta. Catheter Cardiovasc Interv 2007;70:569-77.

4. Wang Y, Truong TN, Yen C, et al. Quantitative evaluation of susceptibility and shielding effects of nitinol, platinum, and stainless steel stents. Magn Reson Med 2003; 49:972-6.

Conflict of Interest:

None declared