Spontaneous coronary artery dissecton (SCAD) treatment is currently a mater of debate as scarce data are available for the interventonal cardiologists. In the present review, we introduce 4 representatve clinical scenarios in which different interventonal strategies were carried out. Subsequently, we discuss different tools and useful techniques for the treatment of SCAD, presentng the advantages and drawbacks of the conservatve approach versus percutaneous coronary interventon with drug elutng stent or bioresorbable scaffolds implantaton, and/or cutng balloon angioplasty.

Spontaneous coronary artery dissecton (SCAD) is an acute spontaneous separaton between the layers of the coronary artery wall, causing the formaton of a false lumen with or without intmal rupture. By definiton, this should not be related to external trauma, direct instrumentaton (iatrogenesis) nor complicated atherosclerosis.1,2 The dissecton can both act as an obstacle for the blood flow and as a path for clot actvaton. SCAD is an important cause of myocardial infarcton, though probably under-diagnosed. The incidence of SCAD in consecutve angiographic case series ranges between 0.07 and 0.2%and rises up to 2-4% in the coronary angiographies performed during acute coronary syndromes.1-3 Importantly, it has been reported to underlie 35% of myocardial infarctons in young female populaton.3 Generally, patents suffering SCAD show a smaller burden of coronary risk factors and are younger in age than the typical patents affected by atherosclerotc acute coronary syndromes.4,5 There is stll lack of consensus concerning the best treatment for SCAD; a couple of studies have reported outcomes of patents conservatvely managed, treated with coronary angioplasty or with surgical coronary by-pass graf. However, no randomized trial is available, and the predictors of success for each of the therapeutc approaches are currently under investgaton.

In the present review we reported the experience with four SCAD cases treated with different approaches that illustrate the array of strategies that are currently available.

A 45-year-old woman with no cardiovascular risk factors and a familial history of Ehler-Danlos syndrome was admited for chest pain with transient electrocardiogram (EKG) inferior ST-elevaton. Coronary angiogram showed a severe and long narrowing from the proximal to the mid-distal segments of the right coronary artery (RCA), compatble with an angiographic type 2b SCAD patern (according to the latest classificaton proposed),1 with thrombolysis in myocardial infarcton (TIMI) 3 flow (Figure 1A). Given her clinical stability, she was deemed for conservatve management. The patent developed EKG and echocardiographic signs of limited inferior necrosis but was asymptomatc and preserved a normal ejecton fracton (EF). A surveillance scheduled coronary angiogram performed 1 week later showed a normal coronary artery suggestng the complete reabsorption of intramural hematoma (Figure 1B). Single antplatelet therapy with acetylsalicylic acid was prescribed. Patent remains asymptomatc afer more than 2 years of clinical follow-up.

A 42-year-old woman on estrogenic hormonal therapy and a history of multple sclerosis treated with interferon presented with anterior ST-elevaton myocardial infarcton (STEMI). Emergent coronary angiogram showed spontaneous dissecton of distal lef anterior descending (LAD) (Figure 2A), which was subsequently complicated by a superimposed iatrogenic dissecton of lef main, proximal LAD and proximal circumflex artery with severe hemodynamic impairment (Figure 2A). Percutaneous coronary interventon (PCI) was performed with implantaton of 6 drug elutng stents (total stent length = 140 mm) involving lef main, LAD and proximal circumflex (LCX) (Figure 2B). The patent was discharged asymptomatc, with a moderated reducton of EF. Afer few months a myocardial single-photon emission computed tomography demonstrated no inducible ischemia. Three years later, the patent was hospitalized with a diagnosis of non-ST-elevaton myocardial infarcton (NSTEMI) due to a diffuse spontaneous dissecton of LCX and obtuse marginal branch downstream from the previous stentng (Figure 2C). The patent was stable and therefore was conservatvely managed. Long-term dual antplatelet therapy (DAPT) was prescribed and interrupted 2 years afer because of menorrhagia, metrorrhagia causing anemia. She is to date asymptomatc afer approximately 3 years from the latest dissecton.

A 45-year-old hypertensive woman was admited for NSTEMI. The coronary angiography showed type 2-3 spontaneous coronary dissecton in mid-LAD with TIMI flow grade 3 (Figure 3A). Although an inital conservatve approach was adopted, the patent experienced recurrent chest pain and developed EKG signs of acute asymptomatc anterior ischemia in the fifh day of hospitalizaton. Coronary angiography was repeated, showing significant worsening of the LAD narrowing, causing sub-occlusion of true lumen (Figure 3B). PCI was performed under optcal coherence tomography (OCT) imaging guidance with successful implantaton of two overlapped magnesium-made bio-reabsorbable scaffold (Figure 3C). Afer a few days asymptomatc, the patent was discharged and prescribed at least three years of DAPT. Surveillance angiogram showed a good angiographic and imaging outcome.

A 50-year-old woman with no cardiovascular risk factors was admited with an anterior STEMI. The coronary angiography showed spontaneous dissecton of distal LAD. Afer successfully wiring the distal vessel, several dilatatons with a 3.0/10 mm cutng balloon at 12 atmospheres were performed (Figure 4A). Because the absence of symptoms and TIMI 3 flow afer dilataton, the operator opted to avoid stentng. The good result achieved in the acute phase (persistence of dissecton flap but preserved flow) was confirmed with electve coronary angiography afer one week and one year (Figure 4B). The patent was discharged with EF 40% and with indicaton for one year of DAPT.

No randomized trials comparing conservatve versus interventonal strategies have ever been carried out so far in SCAD. The challenge of conductng such studies is due to the low incidence of the disease plus the varied severity of clinical presentatons.

Today the available literature shows that the therapeutc strategy is conditoned by clinical presentaton and stability, coupled with angiographic characteristcs (site and extension of dissecton or TIMI flow).6 The fact that PCI in SCAD is burdened with a high complicaton rate favors a conservatve approach over a revascularizaton strategy (either PCI or coronary artery bypass grafing) whenever clinically possible (i.e. stable patent without ongoing ischemia).

Furthermore, there is a general understanding that, with a conservatve treatment, dissectons tend to heal completely over a certain period of tme: with angiographic evidence from about 1 month afer the acute episode.2,3,7 Therefore, when revascularizaton is not required (i.e. in hemodynamically stable patent) the conservatve management should be the first choice for these patents.

As mentoned above, revascularizaton is associated with high rates of failure and complicatons, likely due to an exaggerated vessel fragility.1,2,8 This includes the risk of catheter-induced iatrogenic dissecton of proximal-ostal locatons, which may lead to serious clinical consequences and complex interventons (Figure 5).

Additonally, patents receiving a conservatve strategy showed beter in-hospital outcomes compared to the ones receiving revascularizaton, though similar long-term outcomes.4,6 Distal locaton of the dissecton and TIMI flow II or III may be considered predictve factors to favor the adopton of a conservatve approach.6

Nevertheless, our group recently highlighted the unpredictability of SCAD and the importance of a close clinical surveillance following an inital conservatve strategy. In this case series,9 among four patents with similar angiographic and clinical presentaton, two cases experienced a malignant evoluton with need of emergent PCI and extensive stentng (including lef main) while in the other two cases complete angiographic healing was demonstrated in follow-up angiograms.

Revascularizaton should be reserved for high-risk patents with ongoing ischemia, lef main artery dissecton, ventricular arrhythmias or hemodynamic instability.

Procedural success of PCI in SCAD is dramatcally low compared to that in the atherosclerotc populaton. The main studies assessing the role of PCI have shown a high rate of complicatons and unfavorable outcomes.10 For an optmal procedural planificaton, careful assessment of the involved segment (proximal vs distal), lesion length and vessel sizing is mandatory in order to consider all potental challenges and feasibility.

Since SCAD is a disease related to the weakening of the arterial wall, entering the true lumen with a guidewire is quite challenging. Consequently, PCI may easily lead to iatrogenic dissecton or may provoke propagaton of the existng one. Furthermore, even when true lumen is appropriately wired, the subsequent implantaton of stent may determine the squeezing of the intramural hematoma (with possible extension of the dissecton itself) and increase the risk of in-stent restenosis and stent thrombosis.

In an Italian series of 134 SCAD patents where successful PCI was achieved in 72.5%, patents treated conservatvely had lower in-hospital major cardiac adverse events compared with those treated with revascularizaton (3.8% vs. 16.1%).6 Likewise, in the Mayo Clinic series of 189 patents, PCI failure occurred in 53%, and emergency coronary artery bypass grafing was required in 13%.8,10

Wiring of the true lumen distal to the dissecton site is probably the most challenging part of the procedure. As a first-line approach, we suggest using floppy non-plastc wires to navigate in the true lumen compressed by the intramural hematoma. If the wire fails to advance into the true lumen, especially in the case of complete occlusion of the vessel, hydrophilic wires could be used in order to facilitate distal re-entry in the true lumen. A distal tp microcatheter injecton is ofen necessary to confirm correct positon in the true lumen before any balloon dilataton (Figure 6). Intravascular ultrasound (IVUS) guidance may be employed to identfy the false lumen and ensure correct wire placement within the true lumen. Likewise, IVUS will be useful for stent sizing.

In fact, choosing the right length and dimension of the stent represents the next challenge. The distal coronary segments are the most frequently affected and these may be too small for stentng. Moreover, hematoma resorpton could lead to late stent malpositon (stent under-sizing).

Today drug elutng stent (DES) are considered the standard of care for the invasive treatment of the atherosclerotc disease. However, in the past years, doubts about DES use in patents with SCAD were raised.11 As a mater of fact, DES reduce the risk of neointmal growth, but on the other side they may potentally delay the healing of the dissected vessel. Recently, a large observatonal study compared the use of DES against bare metal stent (BMS) and demonstrated the same advantages of DES observed in atherosclerotc disease over BMS even in patents with SCAD.12

In any case, when a stent is to be implanted, less conventonal interventonal approaches can be considered to reduce the number of adverse outcomes:1-3,13

When approaching a long-dissected segment, operators usually prefer to implant long/multple overlapped stents in order to cover the entre dissected segment. However, this exposes these generally young patents to the lifelong risk of restenosis and thrombosis.15

For this reason, bio-resorbable scaffolds (BRS) were proposed for the treatment of SCAD,16,17 in several case series in which bioreabsorbable device was used (AbsorbTM, Abbot Vascular, Abbot Park, IL, USA).18,19 Recently, the first case of use of BRS magnesium made magmaris (BiotronikTM, Buelach, Switzerland) scaffold for SCAD treatment was also reported by our group.20,21-

The use of bioresorbable coronary scaffolds could be advantageous as there is general evidence that the temporary presence of the scaffold could reduce the risk of late maladjustment and thrombosis afer resorpton of IMH.20 BRS provide a temporary support to seal the dissecton and would potentally allow complete vessel healing over tme. Coronary arteries affected by spontaneous dissecton are usually free from hard plaque or heavy calcificaton which makes easier a full expansion of the scaffold avoiding the need for aggressive pre- and post-dilataton, strongly recommended for BRS in atherosclerotc vessels. Moreover, BRS compared to permanent metallic DES could potentally reduce the risk of malappositon afer IMH reabsorpton. BRS are also useful when a long scaffolding is demanding, especially considering the young age of the most part of patents.

Nevertheless, some drawbacks must be underscored. Firstly, the inital enthusiasm kept on these devices has been tempered by clinical trials showing an increased risk of target lesion failure, both early and late afer implantaton of first-generaton AbsorbTM in comparison to DES.22 Newer generaton of scaffolds with faster reabsorpton process and improved platorms will probably overcome these issues in the future even avoiding the risk of prolonging DAPT over tme in such patents. Moreover, most of the failure burden of BRS derives from the use of it in small-caliber vessels (2.5 mm).23 As a mater of fact, such vessels are usually managed conservatvely in SCAD. Finally, intracoronary imaging metculous guidance should be central in any BRS implantaton to achieve a satsfactory deployment and avoid complicatons.

As alternatve to deploy a stent/scaffold is to use cutng balloon only leaving the vessel prosthesis-free. The experience with such device is stll limited to case reports, but the concept is very intriguing.24 The basis derives from the potental to fenestrate the intmal-medial layer and depressurize the false lumen, restoring flow and alleviatng acute ischemia. Conversely, there is a theoretcal potental risk of coronary rupture, thus the use of an undersized balloon is probably a reasonable opton.

Among other specific devices, a ratonale for the use of selfexpandable stent (SES) has been recently proposed. Basically, SES could potentally overcome the risk of late malappositon of the struts (due to the underestmaton of the vessel caliber) finalizing the expansion of the stent once the IMH reabsorpton is completed. However the role of SES is limited to the best of our knowledge to a single case report.25

Use of intravascular imaging techniques [(IVUS) or optcal coherent tomography (OCT)] plays a relevant role in confirming SCAD diagnosis when angiographic appearance is ambiguous. But more importantly, it probably should be an essental tool to guide PCI.2 As discussed previously, imaging is helpful to prove the correct positon of the intracoronary wire; to accurately size the lumen in order to choose the right dimensions of the stent; to verify the complete stent appositon and the whole coverage of the disease and potentally to show coexistent atherosclerosis or other vascular disorder. On the other hand, extraordinary costs and availability may limit the use of intravascular imaging techniques. Moreover, requirement of antcoagulaton could provoke hematoma extension. Finally, vessel instrumentaton can produce iatrogenic damage and superimposed dissectons, as a consequence of the wire, the guiding catheter or the contrast infusion in case of OCT. In a single-center study, some degree of iatrogenic damage was seen in a fifh of the cases were intracoronary imaging was used for diagnosing SCAD, which led to unplanned PCI in most of them.26

SCAD represents today a coronary conditon with unique pathophysiological characteristcs clearly different from the common atherosclerosis. Therefore, when a PCI strategy is preferred, a tailored approached is required taking advantages from extensive use of imaging whenever it is feasible. Finally new technologies answer generatons of scaffold have to keep in mind in order to avoid a permanent extensive stentng of an artery usually free from atherosclerosis and with a good chance of complete healing over tme. However, dedicated trial should be conducted to define their safety and effectveness in long term.