Effect of plaque debulking and stenting on short- and long-term outcomes after revascularization of chronic total occlusions

Patient population

Between July 1996 and July 1997, a total of 150 consecutive patients underwent successful recanalization of 176 totally occluded native coronary arteries (duration of occlusion >2 weeks). These patients represent 73% of the total number of patients with a chronic total occlusion in whom recanalization had been attempted.

Patients were treated with either of two different strategies: 1) lesion modification (debulking) by excimer laser, rotational or directional atherectomy followed by stent deployment in 44 patients (50 lesions), or 2) conventional balloon angioplasty followed by stent placement in 106 patients (126 lesions). Following hospital discharge, patients were either seen at the clinic by the research nurse or contacted by telephone or mail for late clinical follow-up.

Procedure

Device strategy was selected based on vessel size and anatomy, preprocedural lesion configuration (i.e., lesion eccentricity, ulceration, irregularity, calcification, thrombus or ostial location) and the absence of clinical contraindications at the discretion of the operator. Debulking was achieved with excimer laser, directional coronary atherectomy (DCA) or rotational atherectomy, as previously described (20).

Adjunctive medical therapy

During the procedure, heparin bolus was administered to achieve an activated clotting time >300 s. Aspirin therapy, 325 mg, was started at least 24 h before the procedure and continued indefinitely. Ticlopidine, 500 mg, was given before the procedure and treatment with it was continued for four weeks (250 mg orally twice daily). Glycoprotein IIb/IIIa inhibitors were used in <2% of the patients in both groups.

Angiographic analysis

Quantitative angiographic analysis was done at the Angiographic Core Laboratory by an independent observer who was unaware of the purpose or outcome of the study. The analysis was done on end-diastolic cine frames demonstrating the stenosis in its more severe and nonforeshortening projection, using a computer-assisted, automated algorithm (ARTREK, Quantitative Cardiac Systems) and using standard morphologic criteria (21). The contrast-filled catheter was used as the calibration standard. Reference vessel size was assessed from the postprocedural images.

Intravascular ultrasound

Intracoronary ultrasound (IVUS) studies were performed after intracoronary injection of 200 μg of nitroglycerin with one of the two commercially available systems as previously described (22). In each case, the transducer was advanced approximately 10 mm beyond the lesion and withdrawn automatically at 0.5 mm/s to the aorto-ostial junction. On-line analysis during the procedure was reported to the operator regarding reference vessel diameter, minimal lumen diameter (MLD), stent and lumen cross-sectional area and stent apposition. The images were recorded on a 1/2-in. high-resolution S-VHS tape for off-line analysis and independently reviewed at the IVUS Core Laboratory.

Definitions

A “total occlusion” was defined as complete interruption of the vessel with Thrombolysis in Myocardial Infarction (TIMI) grade flow 0 (23). “Angiographic success” was defined as recanalization of the artery with a <50% residual diameter stenosis with restoration of TIMI 3 flow. Q-wave myocardial infarction (MI) was defined by the development of new Q waves on the postprocedural ECG. Non-Q-wave MI was defined as the elevation of CPK-MB ≥5 times of normal values without the appearance on new Q waves.

Statistical analysis

Statistical analysis was performed using software (StatView 4.01; Abacus Concepts; Berkeley, California). Continuous data are presented as mean ±SD. Comparisons between groups were performed using the chi-square test to analyze differences in categorical variables, and the Student ttest was used for continuous variables. Follow-up events were analyzed by the Kaplan-Meier method. Freedom from target lesion revascularization (TLR) and for late events was generated for both groups and differences between them compared with the log rank test. Cox proportional hazards regression analysis was performed to determine the independent correlates of TLR and late events. Clinical, morphologic and procedural variables were entered into a multiple logistic regression model to determine the following independent correlates of TLR and event-free survival: age, gender, history of diabetes, lesion length, ostial location, left anterior descending coronary artery, restenotic lesion, preprocedural reference vessel diameter, final MLD and final cross-sectional area (CSA). The level of significance was p < 0.05.

Patient characteristics

The baseline clinical characteristics for all 150 patients with 176 totally occluded native coronary lesions who had undergone either one of the two treatment strategies are shown in Table 1. Mean age was 59 ± 12 years (range, 30 to 88 years), and 113 (75.8%) were male. The group undergoing debulking before stenting included more male patients, with a higher, but not significant, number of diabetic patients and patients who had undergone aortocoronary bypass surgery. Accelerated angina was present in 66.7% of patients who had undergone stenting and in 68.2% of patients who had undergone debulking prior to stenting (p = NS), whereas recurrent angina after an MI was present in 15.7% and 11.4%, respectively (p = NS).

Revascularization strategies

Debulking was performed prior to stenting in 44 patients with 50 lesions. Excimer laser was used in 34 lesions (68%), rotational atherectomy in 10 lesions (19%) and directional atherectomy in 6 lesions (13%). Stent alone was used in 106 patients with 126 lesions. A single stent was deployed in 47 patients (31%), 2 stents in 56 patients (37%) and >3 stents in 47 patients (31%). An average of 2.03 ± 1.06 stents were used in each patient.

Angiographic and IVUS characteristics

Intravascular ultrasound was performed in 86.1% of the lesions after successful recanalization of the artery and at the end of the procedure. The angiographic and IVUS characteristics for these lesions are detailed in Table 2. The left anterior descending artery (LAD) was the target vessel in 50% of the patients who had undergone debulking with stent deployment, compared with 21% in the other group (p = 0.001). These patients also had longer lesions than the patients who had undergone stenting alone (10.4 ± 6.5 mm vs. 23.0 ± 14.1 mm, p = 0.03). Postrecanalization, prestenting reference vessel diameter, preprocedural lesion CSA, final lumen CSA and final MLD were slightly larger in patients who had undergone stenting alone, although the differences were not statistically significant (Table 2).

In-hospital events

Clinical events during hospitalization are presented in Table 3. Death, Q-wave and non Q-wave MI rates did not differ significantly between the two groups. Major vascular complications requiring surgical repair or blood transfusion were also similar between the groups.

Clinical follow-up

Data were available for 98% of the patients, at mean follow-up time of 14 ± 8 months (Table 4). There were no deaths during this period in either of the two groups. There was a higher incidence of Q-wave MI in the debulking plus stent group compared with the stent alone group (7% vs. 0%, p = 0.02). The incidence of TLR was similar for both groups respectively (16.4% vs. 14.4%, p = NS). By Cox regression analysis, age was identified as the only independent predictor of TLR (odds ratio: 0.958; confidence interval, 0.93 to 0.98, p = 0.0008).

Study limitations

The present study was a retrospective analysis, and therefore the conclusions and results are subject to the limitations inherent in all such reports. Operator evaluation of each individual case, the selection of debulking before stent deployment and the specific device used may be important limitations. Patients did not undergo routine follow-up catheterization to assess the angiographic restenosis rate and early reocclusion rate, which has been shown to be high and may be clinically silent because of preexisting collateral flow (19). However, we found an encouraging relatively low rate of clinical restenosis for a population of patients in whom results have been discouraging in the past with balloon angioplasty alone (31,32). Application of a debulking strategy was implemented without a protocol to dictate a specific reduction in plaque burden. Thus, we did not necessarily evaluate “optimal” (or “maximal”) debulking in this study. It is unknown whether debulking with high ablation efficiency in this type of lesions might yield even better results. Finally, the small study population may not allow for appropriate correction of baseline imbalances between the groups. This may have introduced a bias against the debulking plus stent approach, as this group included longer and more LAD lesions.