Follow-up of iatrogenic aorto-coronary "Dunning" dissections by cardiac computed tomography imaging

Iatrogenic aorto-coronary dissections following percutaneous coronary interventions (PCI) represent rare but potentially life threatening complications [1]. The overall incidence is estimated around 0.02% and more common in patients with acute myocardial infarction compared to elective PCI [2]. Dunning et al. classified these dissections into three groups, where the local involvement of the ipsilateral cusp was defined as class I, the extension along the ascending aorta of less than 40 mm as class II and more than 40 mm as class III [2]. Patients with limited aortic involvement (class I and II) were described to be managed successfully by a “wait-and-see” strategy or PCI with implantation of a stent at the coronary dissection entry [2]. In contrast, Dunning dissections (DD) of type III require treatment by cardiovascular surgery [2]. While surgical treatment is still under debate, it is still under ongoing debate whether PCI with implantation of drug eluting stents (DES) at the aorto-ostial dissection might represent a valuable treatment alternative even in extensive dissections [3]. Nonetheless, large-scaled randomized controlled studies evaluating the best treatment choice in patients with DD are not available and the current scientific knowledge is limited to single case series [2].

Because patients suffering from DD underlie an increased risk of death, they may ultimately profit from an accurate diagnostic follow-up to guarantee best medical treatment [4]. However, no cCTA imaging algorithm for follow-up was yet developed in order to ensure an accurate treatment of this rare disease entity. Therefore, this study aims to describe our institutional experience to follow-up these high-risk patients.

The present retrospective and observational study outlines clinically relevant aspects about the timely diagnosis, treatment and imaging follow-up of patients suffering from iatrogenic aorto-coronary dissections i.e. Dunning dissection (DD) as a consequence of PCI during routine clinical care.

Modern interventional cardiology allows the chance of treating most complex and technically challenging coronary lesions by PCI [6]. The most important advantage from the patient’s perspective represents the minimally invasive treatment approach compared to open-heart surgery. As reported by Dunning et al. the rate of iatrogenic aorto-coronary dissections is higher during PCI of patients suffering from an acute myocardial infarction (0.19%) or of elective patients (0.03%) compared to conventional diagnostic coronary angiographies (<0.01%) [2]. Within the present cohort DD occurred mostly during elective and planned complex PCI and in one patient suffering from NSTEMI with subsequent cardiogenic shock. The most frequent causes of dissection occurred during interventions of the RCA (88%) and CTOs (38%). All PCIs were complex interventions being affirmed by a median SYNTAX-II-score of 35.3. After high-risk PCIs such as a PCI of a CTO close-meshed follow-up and clinical assessment is mandatory to ensure a successful outcome, because the risk of aorto-coronary dissections was markedly increased by 1.8% [7].

The vast majority occurred during PCI of the RCA, while the exact underlying pathomechanism still remains unclear [1, 8]. Within the present study the most important risk factors for Dunning dissections as being estimated by the PCI-operator contain a too deep intubation and engagement with the catheter (50%), use of an AL 1 catheter (50%), use of a mother in child catheter (50%) and subintimal wire tracking or wire externalization (13%). According to the literature, further potential risk factors seem to be the tortuous anatomy and smaller size auf the RCA, the degree of calcification mainly the aortic root, the type and manipulation of used guiding catheters, heavy coronary calcification and wires during the intervention [4, 9, 10].

Aorto-coronary dissections extending into the aortic root as described in this study were treated with central ostial PCI/DES implantation being positioned by an overlap into the ascending aorta after diagnostic confirmation by angiography. If interventional entry sealing could not perform rapidly, a conservative wait-and-see approach has a high risk of uncontrollable dissections with consecutive major vascular complications [3]. Therefore, the exact extension of the dissection is mandatory to know, while coronary angiography often underestimates the extent of the dissection due to inadequate contrast opacification. Some authors recommend intravascular ultrasound (IVUS) guided coronary stenting to ensure complete coverage of the DD and exact placement of the stent to entirely cover the ostium [11, 12]. Furthermore, only slight and few contrast should be injected carefully and directly over the guiding catheter in order not to sustain or even increase the dissection entry. IVUS or CTA may be applied instead of these direct contrast injections at coronary ostia via catheters.

The technical advances in ECG-gated CTA scanner technologies with low-radiation dose and high resolution images allow to show progression or regression of the dissection [13]. Novel technical developments allow to reduce the noise and residual artifacts with simultaneous detail preservation even in low-dose cCTA images [14, 15].

Therefore, CTA is ideally suited to confirm the presence of residual aortocoronary dissection and evaluation of its exact extent and later noninvasive follow-up. Tansie et al. investigated retrospectively eight patients with DD and described their CTA findings. Similar to our population the main side of the dissection was the ostium of the RCA (88%), but in their case series the majority of the DD occurred during conventional coronary angiography (62.5%) [16].

As DD are rare and need immediate treatment, thus randomized multicenter clinical trials are missing and even in the future will be difficult to realize. This single center experience emphasizes the use of CTAs at follow-up in order to control the exact extension of the dissection as soon as the patient is hemodynamically stable, before discharge and after a follow-up period of 3 to 6 months.

DD are rare but serious complications of coronary interventions, while the extent of the dissection is defined at angiography. This study demonstrates that cCTA plays a valuable role for detection and follow-up of patients with DD. While using high-resolution scanners, cCTA can be helpful to provide precious information about the origin and extent of the dissection and is therefore a helpful tool for non-invasive follow-up.