Intravascular Ultrasound Findings in “Pseudostenosis” During Coronary Angioplasty

The “pseudostenosis” is a well-known angiographic finding observed when the guidewire crosses markedly angulated coronary segments, most commonly in right coronary arteries.1–9 This phenomenon is produced by the straightening of angulated segments by the guidewire. It looks like a new stenosis, not present in basal angiography, and can be difficult to distinguish from spasm, dissection or even thrombus. The persistence after nitroglycerin intracoronary injection and reversal of the “stenosis” after guidewire withdrawal provides the definitive diagnosis. However it may be difficult to move the guidewire back especially when the previous forward advance of the guidewire was complex and time consuming. These angiographic appearances must be recognized to avoid unnecessary stenting of arterial segments that are not diseased. We have performed intravascular ultrasound (IVUS) studies in 7 cases with pseudostenosis, all in right coronary artery, and we present our observations. Methods. Patients undergoing PTCA with demonstrated pseudostenosis (angiographic normalization only after guidewire withdrawal) in normally or mild diseased basal coronary segments were included. In all cases a femoral artery access site was used. All patients received heparin (100 U/Kg or 70 U/Kg when using abcximab) and activated clotting time was measured throughout the procedure in order to maintain values over 250. In all cases a relatively stiff guidewire (flexible 0.014, Stabilizer,™ Cordis Corporation, Miami Lakes, Florida) was used in order to provide support and facilitate stent advancement. Stent implantation was performed in all patients with or without predilatation, depending on operator preference. Abciximab administration was left to the operator’s criteria. Intracoronary nitroglycerin (200–300 mg) was administered before every set of angiograms and IVUS pullbacks. IVUS examination was performed using a solid state system (In-vision™ Imaging System with a 20 Mhz Avanar F/X 2.9 Fr catheter, Jomed Inc., Rancho Cordova, Calif.). The transducer was withdrawn manually from a position distal to the “new stenosis”. After on-line evaluation, the study was stored (hard disk and CD) for off-line interpretation. We selected for analysis the tomographic images corresponding to the pseudostenosis and the adjacent reference segments (within 5–10 mm). We have selected for presentation the three cases with the best quality images. All patients were on aspirin (100 mg/day) therapy prior to the procedure and afterwards were treated with clopidogrel (initial dose before sheath removal of 300 mg and 7 mg/day for one month) combined with aspirin. Sheath removal was performed in all patients 1–2 hours after the procedure using vascular closure devices (Vasoseal, Datascope, Mahwah, New Jersey). Patient 1. A 71-year-old male patient with unstable angina, Troponin I elevation and ST changes (depression with pain) in inferior leads. Coronary angiography revealed a severe subtotal lesion in the distal right coronary artery (Figure 1). Once the guidewire crossed the lesion a pseudostenosis appearance was observed in a tortuous proximal segment of the artery. An IVUS study was done, showing the images in Figure 1 at the artifact level. A stent, 3.5 mm diameter and 15 mm length, was implanted in the distal lesion. After guidewire withdrawal, the original RCA contour with resolution of the proximal focal lesion was visible. Patient 2. A 72-year-old male patient with recent Q-wave inferior myocardial infarction was treated with fibrinolysis. A predischarge treadmill test was positive for ischemia, showing ST depression in inferior leads. Coronary angiography revealed a moderate stenosis in the distal RCA (Figure 2). A severe straightening of a proximal segment was observed after a flexible 0.014 guidewire placement. The artery was evaluated with IVUS showing a complex lumen morphology with dissection and ulceration in the distal lesion. The images obtained in the pseudostenosis are shown in Figure 2. A stent (3.5 mm diameter and 18 mm length) was implanted in the distal lesion. Complete resolution of the angiographic artifact was obtained after guidewire removal. Patient 3. A 78-year-old female with a recent non-Q inferior myocardial infarction and post-infarction angina presented for treatment. Coronary angiography showed multivessel disease with severe lesions in the proximal RCA and posterior interventricular branch and a moderate lesion in mid RCA (Figure 3). Marked tortuosity of the RCA was evident. A guidewire was passed across the proximal stenosis. A marked and complex pseudostenosis was observed in the mid RCA segment and an IVUS study was performed in the artery. The images corresponding to the straightened segment are shown in Figure 3. One stent was implanted in the proximal lesion, 3 mm diameter and 24 mm length. Complete return to the basal angiographic morphology in the mid RCA was observed after guidewire removal. Results. No resistance to the advancement of the IVUS catheter was evident in any patient. The patients did not complain of angina during IVUS exploration and no flow compromises were observed immediately after examination. The common ultrasonographic findings observed in all cases are the following (Figure 4): a) elliptical shape of the cross-sectional vessel and lumen areas; b) vessel cross-sectional areas are normally circular in adjacent reference segments; c) eccentric simple plaque distribution with the largest amount of plaque over the minor axis (in one or both sides). The vessel wall bends at the least atheromatous segments; d) a three-layered pattern of intimal thickening on a flattened wall overlying a hypo-echogenic space. This finding was present to a widely variable degree; e) no presence of complex lumen morphology (images suggesting the presence of dissection, ulceration or thrombus). There was no evidence of severe atherosclerosis (minimal lumen area > 4 mm2 and area stenosis Discussion. Vessel spasm and dissection are well known complications of PTCA. The use of coronary angioplasty equipment can make considerable changes in the course and tortuosity of the vessels. Most of the time these are neither noticeable nor clinically important. However, occasionally the guidewires may produce severe straightening of markedly angulated arterial segments which may resemble spasm or dissection.1–9 The right coronary artery is thought to be particularly susceptible to this phenomenon because the artery is embedded in the epicardial fat pad and runs relatively freely in the atrioventricular groove.2–5 However, this artifact has also been described in the internal mammary artery, the left main coronary artery and in peripheral vessels during interventional procedures.1,6–8 This phenomenon causes artifactual coronary lesions, with luminal narrowing as severe as shown in Figure 3 with subtotal occlusion. This finding was associated with eccentric plaque distribution with the largest amount of plaque over the minor axis (in one or both sides) because the vessel wall bends at the least atheromatous segments. Another interesting observation was the presence of a three-layered pattern of intimal thickening on a flattened wall overlying a hypoechogenic space. This pattern was present in all cases to varying degrees. Finally, the absence of complex lumen morphology (no images suggesting the presence of dissections, ulcerations or thrombi) or severe atherosclerosis (minimal lumen area > 4 mm2 and area stenosis Conclusion. We can conclude that in the presence of suspected pseudostenosis and when reasonable doubts persist about diagnosis, IVUS may provide help in the decision making, ruling out severe atherosclerosis, dissections or thrombi and avoiding the unnecessary treatment of these segments.

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