Rapid Evolution from Coronary Dissection to Pseudoaneurysm After Stent Implantation: A Glimpse at the Pathogenesis Using Intrava

Coronary dissection during percutaneous coronary intervention (PCI) occurs frequently and is associated with variable evolution, including the development of acute closure with serious clinical consequences. Stent sealing of the false lumen is a common practice designed to prevent this complication. Coronary dissection can evolve into aneurysm or pseudoaneurysm.1 This phenomenon has been previously described as occurring more than three months after PCI despite stent implantation.2,3 We present a case of very early evolution of dissection to pseudoaneurysm after stenting. The pathogenesis of this phenomenon was clarified by intravascular ultrasound (IVUS). Case Report. A 53-year-old woman with coronary artery disease risk factors of dyslipidemia and smoking was admitted to the hospital due to chest discomfort accompanied with inverted T-waves on electrocardiogram leads V3–V6. She was diagnosed with unstable angina and was catheterized. Severe focal stenosis of the mid left anterior descending (LAD) artery (Figure 1) and total occlusion of the first marginal branch were demonstrated. PCI was performed in the mid LAD lesion. A 0.014´´ floppy guidewire (Choice, Boston Scientific/Scimed, Inc., Maple Grove, Minnesota) was negotiated through the LAD, and balloon dilatation at 7 atmospheres (atm) was performed with a 2.5 mm diameter balloon catheter (Worldpass, Cordis Corporation, Miami Lakes, Florida). Resolution of the flow-limiting stenosis was obtained, but the presence of extravasation of contrast compatible with a type C coronary dissection was observed (Figure 2). A 3-mm diameter, 9-mm length coronary stent (GFX, Arterial Vascular Engineering, Santa Rosa, California) was deployed at the dissection site at 12 atm. A widely open lumen without residual dissection was achieved (Figure 3). The patient was treated with ticlopidine and aspirin and discharged home the next morning. Six weeks after the initial procedure, typical anginal pain reappeared, and the patient was readmitted to the hospital with the diagnosis of unstable angina. Coronary angiography was performed; it demonstrated a widely open stent, severe focal stenosis at the proximal end of the stent, and saccular extravasation of contrast with a neck originating in the mid-portion of the stent, compatible with coronary aneurysm (Figure 4). An IVUS study was performed in order to elucidate the nature of the findings. A 3.2 French, 30 MHz Clearview Ultra IVUS catheter (Boston Scientific/Scimed, Inc.) was advanced into the LAD. Immediately proximal to the end of the stent, a significant crescent-like lesion (lumen area, 2.4 mm2; minimal lumen diameter, 1.1 x 2.4 mm) was detected (Figure 5). IVUS analysis demonstrated symmetric, incomplete expansion of the stent from the proximal stent body through the aneurysmatic region up to almost the distal stent edge. The distal stent outlet showed complete stent apposition to the vessel wall. In the region of the proximal stent body, there was no contact between the vessel wall and the stent struts in a 360° arc of vessel circumference, with a cross-sectional vessel area of 10.8 mm2, cross-sectional stent area of 4.0 mm2 and minimal luminal diameter of 2.0 mm. The proximal entrance of the aneurysm lumen was located 3.5 mm distal to the proximal stent edge. In the region of the aneurysm, there was no stent to vessel wall contact in a 270° arc . Discussion. In this case, detailed information about the stent/vessel interaction was obtained by performing intravascular ultrasound. Incomplete stent expansion and unsuccessful sealing of the dissection entry site may have contributed to the aneurysm formation. Development of coronary aneurysm or pseudoaneurysm after PCI is not a rare finding. A rate of 3.9% has been described after PTCA,1 10% after direct atherectomy,4 and 3.5–5% after stenting.2 In these previous reports, IVUS was not employed, and differentiation between aneurysm and pseudoaneurysm was not made. The cause of these findings after PCI is unclear. The use of larger balloons or high-pressure inflation,5,6 the performance of PTCA in the setting of acute myocardial infarction, the development of restenosis and an inadequate biological healing process as occurs during treatment with anti-inflammatory drugs or in cases with systemic arteritis, have all been proposed as etiological factors.7 Coronary dissection has also been considered a possible cause of coronary aneurysm after PCI. After stent implantation, Slota et al.2 showed a trend of more frequent aneurysm development in patients with coronary dissection (8.9%) than in those without dissection (4.7%; p = 0.20). The reason for the development of an aneurysm or pseudoaneurysm after stenting is unknown. The creation of stent edge dissections, the presence of an uncovered entry site of a coronary dissection, and the failed sealing of a false lumen due to inappropriate stent deployment have been proposed to explain this phenomenon.2,7 IVUS has the potential to provide detailed anatomic information about aneurysm development after stent implantation, but only a few cases have been analyzed with this technique and reported in the literature. This case report describes the early development of aneurysm formation after stent implantation and the subsequent IVUS study. In a previous case reported by Kitzis et al.,8 a pseudoaneurysm was found 3 months after stent implantation. IVUS examination revealed a pseudoaneurysm of the artery proximal to the implanted stent. In another case, Regar et al.9 described coronary aneurysm development in the stented segment 6 months after bail-out stenting. IVUS demonstrated the uncovered entrance of the false lumen located proximal to the stent inlet, suggesting that this was the reason for the subsequent evolution of the aneurysm. In our case, the neck of the aneurysm was seen angiographically in the mid-portion of the stented segment. IVUS demonstrated the circumferential non-apposition of the stent to the artery wall. This was secondary to the differences between the diameter of the stent chosen and the real diameter of the artery in the stented segment. In addition, a severely restenosed segment was seen immediately proximal to the stent. The failure to seal the dissected false lumen and the increased flow velocity secondary to the proximal stent edge stenosis could explain the expansion of the false lumen. The natural history and treatment of coronary aneurysm are uncertain and a “preferred treatment” is not known. Aneurysm rupture and thrombus formation are harmful complications, but their frequency is unknown. The majority of authors recommend surgical intervention, such as bypass grafting and resection or ligation of the aneurysm. However, others have chosen medical treatment and also report good results.10,11 A covered stent, with isolation of the aneurysm cavity, is another possible treatment option. Conclusion. Despite coronary stenting, coronary aneurysm/pseudoaneurysm can develop rapidly following coronary dissection. IVUS can provide morphological demonstration of this phenomenon. Incomplete apposition of the stent to the artery wall could explain the rapid development of aneurysm following coronary dissection.

1. Egbert T, Bal HW, Plokker T, et al. Predictability and prognosis of PTCA-induced coronary artery aneurysm. Cathet Cardiovasc Diagn 1991;22:85–88. 2. Slota PA, Fischmann DL, Savage MP, et al. Frequency and outcome of development of coronary artery aneurysm after intracoronary stent placement and angioplasty. STRESS Trial Investigators. J Am Coll Cardiol 1997;79:1104–1106. 3. Hill JA, Margolis JR, Feldmann RL, et al. Coronary arterial aneurysm after balloon angioplasty. Am J Cardiol 1983;53:261–264. 4. Cohen AJ, Banks A, Cambler P, Edwars FH. Post-atherectomy coronary artery aneurysm. Ann Thorac Surg 1992;54:1216–1218. 5. Wolff MR, Resar JR, Stuart RS, Brinker JA. Coronary artery rupture and pseudoaneurysm formation resulting from percutaneous coronary angioscopy. Cathet Cardiovasc Diagn 1993;28:47–50. 6. Vassanelli C, Turri M, Morando G, et al. Coronary artery aneurysms after percutaneous coronary angioplasty: A not uncommon finding at elective follow-up angiography. Int J Cardiol 1989;22:151–156. 7. Rab ST, King III SB, Roubin GS, et al. Coronary aneurysms after stent placement: A suggestion of altered vessel wall healing in the presence of anti-inflammatory agents. J Am Coll Cardiol 1991;18:1524–1528. 8. Kitzis I, Kornowski R, Miller H. Delayed development of a pseudoaneurysm in the circumflex artery following angioplasty and stent placement treated with intravascular ultrasound guided stenting. Cathet Cardiovasc Diagn 1997;42:51–53. 9. Regar E, Klauss V, Henneke KH, et al. Coronary aneurysm after bailout stent implantation: Diagnosis of a false lumen with intravascular ultrasound. Cathet Cardiovasc Diagn 1997;41:407–410. 10. Alford WC, Stoney WS, Burrus GR, et al. Recognition and operative management of patients with arteriosclerotic coronary aneurysm. Ann Thorac Surg 1976;22:317–320. 11. Smith MD, Cowley MJ, Vetrovec GW. Aneurysm of the coronary artery: A report of three cases and review of the literature. Cathet Cardiovasc Diagn 1984;10:583–591.