Background. Restenosis after successful balloon angioplasty remains problematic. Early elastic response after angioplasty is significant when considering the possible development of restenosis. The purpose of this study was to compare early elastic recoil within 10 minutes after successful percutaneous transluminal coronary angioplasty and early lumen loss at 24 hours after angioplasty in a cutting balloon group and a conventional balloon group. Methods. Extent of early elastic recoil was quantitatively measured as the difference of mean balloon diameter at maximal inflation pressure and minimal luminal diameter after angioplasty in 82 cutting balloon-treated lesions and 51 conventional balloon-treated lesions. Results. Reference diameter and balloon/artery ratio were similar between the cutting balloon and conventional balloon groups (2.89 ± 0.47 mm vs. 2.88 ± 0.60 mm; 1.19 ± 0.11 vs. 1.19 ± 0.13, respectively). Early elastic recoil after angioplasty was significantly smaller in the cutting balloon than the conventional balloon group (0.96 ± 0.40 mm vs. 1.12 ± 0.37 mm, respectively; p = 0.04). Also, the mean amount of lumen loss from 10 minutes after angioplasty to 24 hours after was significantly smaller in the cutting balloon than the conventional balloon group (0.08 ± 0.28 mm vs. 0.20 ± 0.33 mm, respectively; p = 0.02). Conclusion. There is significantly less early elastic recoil in the cutting balloon angioplasty than in the conventional balloon angioplasty group. The efficacy of cutting balloon continues 24 hours after angioplasty.

       Percutaneous transluminal coronary angioplasty (PTCA) by conventional balloon is the primary technique used for percutaneous coronary revascularization. However, restenosis after successful coronary balloon angioplasty remains a problem. Although neointimal proliferation is important in restenosis, early elastic behavior after balloon angioplasty may also play a significant role. Early elastic recoil after conventional balloon angioplasty was observed to be a luminal diameter loss of 17–50% immediately after balloon deflation.1–7 Restenosis was significantly greater in patients with early elastic recoil.6
       The cutting balloon apparatus contains 3–4 longitudinal microminiaturized microtome blades, or “atherotomes”. “Controlled” sharp, longitudinal incisions in the diseased arterial segment result in less severe arterial injury and fewer major dissections than conventional balloon angioplasty.8 Theoretically, the mechanisms of cutting balloon angioplasty may lead to less elastic recoil and less late restenosis. Angiographic restenosis rates are lower in cutting balloon angioplasty than in conventional balloon angioplasty.9,10
       This study was undertaken to compare early elastic recoil within 10 minutes after successful angioplasty and early lumen loss at 24 hours after angioplasty in cutting balloon and conventional balloon groups.

Methods

       Patient population. From a total of 924 patients undergoing percutaneous coronary intervention at Komaki City Hospital between September 1994 and January 1998, we identified 121 patients with 133 lesions that were suitable for cutting balloon angioplasty and matched the criteria defined below. We performed cutting balloon angioplasty in 73 patients with 82 lesions, and conventional balloon angioplasty in 48 patients with 51 lesions. All patients underwent repeat coronary angiography 24 hours after successful angioplasty. In the cutting balloon group, coronary angioplasty was performed only by cutting balloon. Adjunctive conventional balloon angioplasty was not considered. Exclusion criteria included total occlusions, significant left main coronary artery disease, ostial lesions, lesions containing extensive calcification, tortuous lesions proximal to the target lesion, angiographically visible thrombus, bypass graft lesions, in-stent restenotic lesions, vessel diameters < 2.0 mm and acute myocardial infarction (TIMI 0 or 1). Successful coronary angioplasty was defined as < 50% diameter stenosis of the vessel lumen after angioplasty, without stenting or severe coronary dissection (NHLBI C–F). Written, informed consent was obtained from all patients before the procedure was undertaken.

       Coronary angioplasty procedure. Percutaneous coronary angioplasty was performed by the femoral approach. During catheterization, a bolus of 10,000 IU of intravenous heparin and 5 mg of intracoronary isosorbide dinitrate were given immediately before the angioplasty procedure. The ratio of dilating balloon to the reference vessel diameter used was visually estimated to be between 1.1 and 1.3. Inflation time and pressure were left to the discretion of the operators. Balloon inflations were repeated until there was an acceptable gain in lumen diameter, and during each inflation a film sequence of the contrast-filled balloon was obtained. Medications after angioplasty (up to the 24-hour repeat angiogram) consisted of a continuous infusion of intravenous heparin, intravenous nitroglycerin, aspirin and a calcium channel blocker.

       Quantitative coronary analysis. Patients were examined angiographically before, 10 minutes after, and 24 hours after angioplasty. Five mg of intracoronary isosorbide dinitrate were administered prior to performing coronary angiogram. The percent diameter stenosis, reference diameter, minimal luminal diameter and lesion length were determined using an automated edge detection system (Cardiovascular Measurement System, Medis Medical Imaging Systems, Nuenen, The Netherlands). The basic method of analysis was described in a previous report.11 The mean balloon diameter at the highest inflation pressure was also determined. Acute coronary recoil after angioplasty was calculated as the mean balloon diameter at the maximal inflation pressure minus the minimal luminal diameter after angioplasty. The percent acute recoil was also calculated as (acute recoil/inflated balloon diameter at the maximal inflation pressure) x 100.

       Statistical analysis. Individual quantitative data were used to calculate mean values and standard deviations. Comparisons between groups for continuous data were performed with Mann-Whitney’s U-test. Differences between proportions were assessed by Chi-square analysis. A p-value < 0.05 was considered significant.

Results

       Baseline clinical characteristics are shown in Table 1. Clinical presentations and risk factor prevalences were not different between the cutting balloon group and the conventional balloon group.
       Table 2 shows baseline angiographic and procedural angiographic data. There were no significant differences in the distribution and ACC/AHA classification of lesions between the two groups. The balloon diameter to reference artery ratio was 1.19 ± 0.11 in the cutting balloon group and 1.19 ± 0.13 in the conventional balloon group (p = NS). Maximal inflation pressure was lower in the cutting balloon group (6.5 ± 0.9 atm vs. 7.3 ± 2.4 atm in the conventional balloon group; p = 0.004). Both the longest inflation time (159 ± 61 seconds vs. 204 ± 72 seconds; p = 0.004) and the total inflation time (220 ± 119 seconds vs. 529 ± 316 seconds; p < 0.0001) were shorter in the cutting balloon group than in the conventional balloon group.

       Angiographic analysis. The results of reference diameter, minimal luminal diameter, diameter stenosis and lesion length at baseline, 10 minutes after, and 24 hours after angioplasty are shown in Table 2. At baseline, there were no differences in reference diameter and in stenotic severity between groups. Lesion calcification was observed in 18% of the cutting balloon group and in 22% of the conventional balloon group (p = NS). There were no significant minimal luminal diameter differences at baseline (0.87 ± 0.36 mm vs. 0.79 ± 0.24 mm) or at 10 minutes after angioplasty (2.03 ± 0.44 mm vs. 1.90 ± 0.52 mm), but there was a significant difference in minimal luminal diameter 24 hours after the procedure (1.94 ± 0.41 mm vs. 1.64 ± 0.41 mm; p = 0.001) between the cutting balloon group and the conventional balloon group, respectively. There was no significant difference in percent diameter stenosis at baseline (70.8 ± 9.2% vs. 71.8 ± 8.9%), but there were significant differences in percent stenosis 10 minutes after (29.1 ± 10.6% vs. 33.1 ± 12.5%; p = 0.04) and 24 hours after angioplasty (31.4 ± 11.5% vs. 39.8 ± 12.8%; p = 0.0003) between the cutting balloon group and the conventional balloon group, respectively. There were no total occlusions at 24-hour follow-up angiograms in either group.

Figure 1

omparison in percent acute recoil 10 minutes and 24 hours after angioplasty between the cutting balloon group and the conventional balloon group. Percent acute recoil was calculated as (acute recoil/mean balloon diameter at maximal inflation pressure) x 100.

       Acute gain and acute coronary recoil. There was no significant difference in the acute gain between the cutting balloon group and the conventional balloon group (1.15 ± 0.49 mm vs. 1.08 ± 0.60 mm, respectively). The early recoil within 10 minutes after angioplasty was significantly smaller in the cutting balloon group than in the conventional balloon group (0.96 ± 0.40 mm vs. 1.12 ± 0.37 mm, respectively; p = 0.04). Also, acute recoil at 24 hours after angioplasty was significantly smaller in the cutting balloon group than in the conventional balloon group (1.05 ± 0.41 mm vs. 1.32 ± 0.44 mm, respectively; p = 0.0007).
       Percent acute recoil 10 minutes and 24 hours after angioplasty was significantly lower in the cutting balloon group than in the conventional balloon group (32.0 ± 11.9% vs. 37.4 ± 11.6%, p = 0.02; 34.7 ± 11.6% vs. 43.6 ± 12.4%, p <0.0001, respectively) (Figure 1). The mean amount of lumen loss from 10 minutes after to 24 hours after angioplasty was significantly smaller in the cutting balloon group than in the conventional balloon group (0.08 ± 0.28 mm vs. 0.20 ± 0.33 mm, respectively; p = 0.02) (Figure 2).

Figure 2

Comparison in early lumen loss from 10 minutes to 24 hours after percutaneous transluminal coronary angioplasty between the cutting balloon group and the conventional balloon group.

Discussion

       We found that cutting balloon angioplasty showed significantly less early elastic recoil than conventional balloon angioplasty. Minor deterioration of the minimal luminal diameter was found during the first 24 hours after successful cutting balloon angioplasty as compared with conventional balloon angioplasty.
       The mechanisms of conventional balloon angioplasty include fissuring and disruption of the atherosclerotic plaque, dehiscence of the atheroma from the underlying media, tearing of the intima and stretching of the lesser diseased or nondiseased arterial segment.12 Intracoronary ultrasound imaging showed that lumen enlargement after balloon angioplasty was the combined result of wall stretching, plaque compression and deep tearing of the plaque or coronary dissection.13–15 Baptista observed that wall stretching was the most important mechanism of lumen enlargement in vessels with disease-free walls.13 Due to the elastic properties of coronary arteries, restitution of the elastic forces resulting from overstretching of the uninvolved arterial wall segment may be responsible for an immediate or progressive loss of part of the luminal increase gained during balloon inflation. Early elastic recoil after conventional balloon angioplasty was observed to be a luminal diameter loss of 17–50% immediately after balloon deflation.1–7 Rodriguez showed that early loss due to elastic recoil occurred within 1 hour of coronary balloon angioplasty.16 Early recoil of the treated lesions was more likely to develop restenosis at follow-up.5,6 Restenosis was significantly greater in lesions exhibiting > 0.3 mm loss in minimal luminal diameters and/or > 10% increase in diameter stenosis at 24-hour angiography after successful PTCA.6 Implantation of Palmaz-Schatz stent eliminated the decrease in vessel dimensions caused by elastic recoil after balloon angioplasty.4 Therefore, coronary stenting in such a high-risk group with early minimal luminal diameter loss after successful angioplasty reduced the incidence of restenosis.17
       Cutting balloons contain 3–4 longitudinal microminiaturized microtome blades which are used to make sharp, longitudinal incisions in the diseased arterial segment before dilating. This results in less severe arterial injury and fewer major dissections than conventional balloon angioplasty.8 Honye et al. observed a higher restenosis rate in concentric plaques without dissection, suggesting that limited wall dissection can be beneficial for long-term lumen patency.18 Controlled incision of plaques by cutting balloon might lead to less late restenosis. We previously reported a 23% angiographic restenosis rate in the cutting balloon group and 42% in the conventional balloon group.9 Ergene et al. similarly reported 27% angiographic restenosis rate for the cutting balloon and 47% for the conventional balloon procedures.10
       Our results revealed that early elastic recoil within 10 minutes after angioplasty was significantly smaller in the cutting balloon group (0.96 ± 0.40 mm vs. 1.12 ± 0.37 mm in the conventional balloon group; p = 0.04). In addition, the mean amount of lumen loss during the first 24 hours after angioplasty was also significantly smaller in the cutting balloon group (0.08 ± 0.28 mm vs. 0.20 ± 0.33 mm in the conventional balloon group; p = 0.02). Greater arterial stretching during angioplasty was associated with more recoil; that is, the most important predictor of absolute and relative recoil was the balloon to artery ratio.1,5,7 As the balloon to artery ratio was similar between the cutting balloon group and the conventional balloon group (1.19 ± 0.11 vs. 1.19 ± 0.13, respectively; p = NS), the influence of the balloon to artery ratio on acute recoil was negligible in this study. The underlying mechanism of less elastic recoil with cutting balloon than with conventional balloon is unknown. “Controlled” incision with the cutting balloon may result in plaque compression or cutting through some of the smooth muscle layer rather than stretching of the disease-free wall. This may lead to less elastic recoil. Reducing early elastic recoil with cutting balloon might be one of the important factors inhibiting restenosis.

       Study limitations. This study has several limitations. First, it was an uncontrolled retrospective observational study limited to a subset of patients who underwent successful coronary intervention. By protocol, vessels with significant dissections were not included in the analysis. Second, coronary angiograms were obtained in several projections taking into account the asymmetry of stenotic lesions. However, views of the inflated balloon were obtained in a single projection, with a balloon cross-section that was assumed to be circular at maximal inflation pressure. Although balloons appeared fully expanded without visible indentation, it is possible that constraints provided by eccentric stenoses would have limited the expansion of the balloon in some directions. Third, although vessel wall and lumen areas are more objectively quantifiable by intravascular ultrasound, we didn’t perform this procedure in our analysis. Finally, late follow-up data were not assessed, so the relationship between acute elastic recoil and late restenosis was not clearly evident in this population.

Conclusion

       Our data demonstrated that the magnitude of early elastic recoil after balloon angioplasty is smaller in cutting balloon angioplasty than in conventional balloon angioplasty. “Controlled” incision with cutting balloon may result in plaque compression or cutting through some of the smooth muscle layer rather than a stretching of a disease-free wall, and this may lead to less elastic recoil. Less elastic recoil by cutting balloon will probably result in reduced late angiographic restenosis.

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