Diagnostic and Therapeutic Endoscopy, Vol. 7, Pp. 15--20 Reprints Available Directly from the Publisher Photocopying Permitted by License Only (c) 2000 Opa (overseas Publishers Association) N.v. Percutaneous Transluminal Angioscopy during Coronary Intervention

To investigate the feasibility of angioscopic-guided percutaneous transluminal coronary angioplasty and to elucidate the mechanism of efficacy of coronary stenting for acute myocardial infarction, we performed coronary angioscopy in 102 patients with stable angina or acute myocardial infarction. Thrombi and intimal flaps were observed in most patients after coronary angioplasty. Large intimal splits were seen in one third of patients. Stents were inserted in 10 patients who were revealed to have a large flap or protruding split to the inner lumen. Thrombolytic agents were administered in 2 patients with large thrombi. Additional treatments were required in 32% of patients. No acute myocardial infarction or unstable angina occurred in patients during hospitalization. Thus, angioscopy of the coronary lumen enables clinicians to determine the most appropriate and least risky coronary intervention strategy. In patients with acute myocardial infarction, angioscopy revealed occlusive or protruding thrombi in 34 of 35 patients. The protruding thrombi disappeared after stenting. The frequency of large intimal flaps increased after predilatation with balloon , but these disappeared after stenting. The present angioscopic study demonstrates that the coronary stent compresses the occlusive or protruding thrombi and covers the ruptured thrombogenic plaque. Consequently, smooth-surfaced and wide vessel lumen are obtained.


zunok@nms.ac.
p.distinguish between a thrombus and a plaque [5,6].Therefore, angioscopy facilitates not only in the correlation of anatomical and pathological fea- tures but also in the monitoring of coronary inter- ventions.Recently, the coronary stent has been widely used for the management of abrupt or threaded occlusion during percutaneous translum- inal coronary angioplasty (PTCA) (bailout) and for the management of acute myocardial infarction [7].H wever, why stenting is efficacious against acute myocardial infarction remains unclear.The purpose of this study is to investigate the feasibility of angioscopic-guided PTCA and to elucidate the mechanism of efficacy of coronary stenting for acute myocardial infarction.


CORONARY ANGIOSCOPY

Coronary angioscopy was performed using of a 4.5 F monorail typed rapid exchange angioscope.

Before coronary angioscopy, the white balance was adjusted for color correction.The coronary lumen could been observed in 5cm long segments by inflating the occlusion cuff on the outer catheter and by moving the optic bundle.Warm saline (0.6-0.8 ml/sec) was injected into the coronary lumen to obtain a clear view.Light power was adjusted to avoid refraction and to obtain adequate color.The images were displayed on the monitor and recor- ded on S-VHS.Angioscopic find

gs can be classi- fi
d into the following 7 categories: thrombus, hemorrhage, dissection, intimal flap, intimal sp it, ulceration and stable atheroma, according to color, mobility, irregularity of intraluminal surface, shape and protrusion into the inner lumen.


ANGIOSCOPIC-GUIDED PTCA

Patients Forty patients diagnosed with stable angina or old myocardial infarction underwent coronary angioscopy immediately after PTCA.PTCA was successfully in all patients by angiographic criteria (residual minimum lumen diameter <= 50%).


Results

Immediately following coronary intervention, the angioscopic visualization of 40 lesions of the 40 patients were reviewed in the cardiac catheteliza- tion room.Angioscopy could not be reviewed in 3 patients because of delivery failure of the angio- scope (2 patients) and inadequate visualization (1 patient).
herefore, 37 patients comprised the study population.The baseline clinical and angio- graphic characteristics of these 37 patients are shown in Table I.Thrembi were observed in most patients after angioplasty despite the use of anti- coagulant and antiplatelet agen

before
nd the during procedure.Intimal flaps were also observed in most patients.Large intimal splits were seen in one third of patients (Table II).Angiography  no acute or subacute coronary occlusions occur- red.Tissue plasminogen activator was adminis- tered intracoronary using the guide catheter in 2 patients with large thrombi.Thrombi were partially dissolved.Additional treatment during coronary intervention was provided in 12 of 37 patients (32.4%) (Fig. 2).No acute myocardial infarction or unstable angina was observed in patients during hospitalization, nor at 6-month postoperative follow-up.


THE MECHANISM OF EFFICACY OF STENT AGAINST ACUTE MYOCARDIAL INFARCTION FIGURE

Angioscopic-guided PTCA.After balloon angio- plasty (POBA), large protruding disruption was observed by angioscopy (right upper), but coronary arteriography failed to disclose disruption (left upper).After stenting, disruption was sealed with stent (right lower).Large coronary lumen was obtained (left lower).

Angioscopic findings after PTCA and subsequent manageme

revealed
intimal flaps in only 2 patients and thrombi in patient.A stent was inserted in l0 patients who had a large flap or protruding split to the inner lumen in order to prevent abrupt occlu- sion of the coronary artery.After the insertion of the stent, large intimal flaps or protruding disrup- tions were sealed with the stent (Fig. 1).

ly tiny
laps were revealed by angioscopy.After stenting, Patients

Primary stenting was performed in 65 patients diagnosed with acute myocardial infarction.Thirty-five of these patients had undergone suc- cessful coronary angioscopy before coronary intervention by predilatation with a balloon and stenting.Baseline clinical and angiographic char- acteristics of the patients are shown in Table III.


Results

Thrombi were observed in 34 of 35 patients (97%).

All thrombi were occlusive or protruding before coronary intervention.After predilatation with a balloon, the frequency of protruding occlusive 100 9O 10 97% 51% 0% before interventio

after ballo
n after stentJng ansjoplasty FIGURE 3 Changes in protruding thrombi before and after stenting in patients with acute myocardial infarction.thrombi decreased from 97% to 51% (16 of 35).

Mural thrombi were observed in the remaining patients.After stenting, protruding thrombi disap- peared in all patients (Fig. 3).Large intimal flaps were observed in 11 of 35 patients (31%) before intervention.The frequency of large intimal flaps increased after predilatation with a balloon from 31% to 97%.However, large ntimal flaps were disappeared after stenting in all patients (Fig. 4).


DISCUSSION

Angioscopic-guided PTCA

Clinicians have conventionally used angiography to determine the clinical outcome of coronary intervention.Unfortunately, angiographic images capture only luminal features and, as such, do not accurately assess most endovascular therapies.Although intravascular ultrasoundography pro- vides cross-sectional images useful in the assess- ment and guidance of coronary interventions [8],

intravascular ultrasound images are limited in spe- cificity for thrombus formation and intimal flaps.

In the present study, angioscopy indicated that intimal flaps and thrombi were often present after balloon angioplasty.Previously we reported that the presence of a large flap, detected by angioscopy, was associated with acute coronary occlusion after conventional PTCA [9].Other investigators [10,11] using angioscopy also showed that the primary cause of pos -angioplasty occlu- sion was intimal flap in the majority of cases, in contrast to a thrombus in only a few cases.

Although previous angioscopic research identified the cause of acute occlusion after PTCA, few reports have reported the efficacy of angioscopic guidance in optimal coronary interventions.We inserted the stent at the site of the large flap or protruding disruptions which were observed by angioscopy, and thrombolytic therapy was pro- vided for patients with large thrombi after PTCA.

No recurrent ischemia occurred during patients' hospital stay following completion of this therapy.

Our present results support the findings of Teirst- ein et al. [12] by confirming the effectiveness of angioscopy during coronary stenting.Clinical decisions directly influenced by angioscopy in Teirstein et al.'s study included the initiation of intracoronary thrombolytic therapy for a throm- bus visualized angioscopically, repeat angioplasty when forming plaque was seen to be bulging into the lumen at the stent articulation site, and the replacement of additional stents replaced when angioscopy revealed significant proximal or distal disease/or an unsuspected gap between 2 tandem stents.Angioscopy influenced the clinical manage- ment of 18 (37.5%)

their patients.Likewise, Mirecki et al. [13] reported that angioscopy
chan- ged clinical management in 75% of patients, obviating the need for thrombolytic therapy and mechanical intervention, and altering the mechan- ical intervention chosen.In the present study, angioscopy influenced the clinical management of 12 out of 37 (33%) patients.Thus, angioscopy of the coronary lumen enables clinicians to determine the most appropriate and least risky coronary intervention strategy for a given patient.Further- more, angioscopy was useful for the prediction and the prevention of acute occlusion after PTCA.


THE MECHANISM OF FEASIBILITY OF STENT FOR ACUTE MYOCARDIAL INFARCTION

Early in the implantation of stents, it was thought that the use of these may be contraindicated if a thrombus was present in the infarcted vessel [14,15].Recently, however, many reports have shown that coronary stenting is feasible after acute myocardial infarction and is actually associated with excellent short-term outcomes [7].Interest-  ingly, this may turn out to be one of the most important applications of stenting despite the early concerns about stent thrombosis.However, the mechanism of favourable outcomes remains to be elucidated.We used angioscopy to examine the morphological ch