Cutting Balloons

Kenneth Chin

The cutting balloon is a device having three or four sharp metal microtome blades (0.25 mm high) mounted longitudinally on the surface of a non-compliant balloon (1). During dilatation, the device produces three or four endovascular surgical incisions. An intravascular ultrasonographic study demonstrated that the longitudinal incisions in the plaque and vessel wall reduce true dissection rates and also produce a nominal decrease in vessel area (2). Thus, cutting balloon angioplasty may limit the degree of traumatic vessel wall injury typically encountered in conventional balloon angioplasty (BA).

The cutting balloon proximal catheter shaft is a hypotube. This hypotube contains the inflation lumen for the balloon. The distal shaft is made of flexible Hytrol material and contains two lumens. One lumen is for balloon inflation, and the second lumen is a guidewire lumen. The distal shaft is coated with a hydrophilic coating. The guidewire exit port is 24 cm from the catheter tip. The port facilitates rapid exchanges.

TECHNICAL CONSIDERATIONS

Cutting balloons are available in quarter sizes from 2 to 4 mm in diameter. Available balloon lengths are 6 mm, 10 mm, and 15 mm. The new Ultra cutting balloon incorporates a smaller hydrophilic-coated shaft of 2.6 mm. The selection of the cutting balloon size should be based on 1.1:1 balloon-to-artery ratio. The 3.5 to 4.0 mm cutting balloons have four atherotomes; other sizes have only three atherotomes. Generally, a cutting balloon has a higher profile than a coronary angioplasty balloon and also is less flexible.

Negative wet preparation of the cutting balloon, outside the body and with the sheath on, is advised. The physician should attempt to deliver the cutting balloon directly to the lesion. However, if the cutting balloon fails to cross the lesion, predilatation with a smaller balloon may be required. The cutting balloon should be inflated slowly, at 1 atm/5 sec, up to 8 to 10 atm. When using the cutting balloon in long segments, the distal portion of the target lesion should be treated first. Overlapping dilatation of the proximal lesion segments then may be performed. It is not advisable to perform repeated dilatation on the same lesion segments.

After usage, the cutting balloon device is deflated by dialing down on the inflation-deflation control and then pulled to negative. The vacuum is maintained on the cutting balloon device, and the deflation is verified under fluoroscopy. This will ensure that the atherotomes are fully invaginated into the balloon, so that they do not cause any dissections upon withdrawal into the guiding catheter.

MECHANISM OF VASODILATATION

Hara et al. (3) reported their experience with an intravascular ultrasound examination of 40 lesions treated with cutting balloon angioplasty and 25 lesions treated with conventional BA, before and after the intervention. Intravascular ultrasound measurements included the vessel area, luminal area, and plaque area. Vessel expansion was evaluated as the ratio of the postprocedural vessel area to that before intervention. The vessel area was 13.9 ± 3.2 and 14.8 ± 3.2 mm² after cutting balloon angioplasty versus conventional angioplasty, respectively, whereas the luminal area was 5.5 ± 1.2 versus 5.7 ± 1.2 mm², and the plaque area was 8.5 ± 2.7 versus 9.1 ± 2.2 mm², respectively. The vessel was smaller and the plaque area significantly smaller after cutting balloon angioplasty.

These investigators noted that the vessel expansion allowed for a 45% luminal enlargement and 55% plaque compression or shift after cutting balloon angioplasty. This is in contrast to conventional angioplasty, in which vessel expansion accounted for 67% and plaque compression or
shift for 33% of luminal enlargement (Fig. 11.1). The vessel expansion ratio was significantly smaller after cutting balloon angioplasty than after conventional angioplasty (1.05 versus 1.22; p <0.05). These findings suggest that the predominant mechanism of dilatation after cutting balloon angioplasty is plaque compression or shift rather than vessel expansion, unlike in conventional angioplasty.

Figure 11.1. Mechanism of luminal increase at the lesion site after cutting balloon angioplasty (CBA) and conventional angioplasty. In the cutting balloon group, plaque area reduction accounted for 55% of the luminal increase and vessel expansion accounted for 45%, whereas the respective values were 33% and 67% in the conventional angioplasty group.

REDUCE INTRAVASCULAR ULTRASOUND STUDY

Recent intravascular ultrasound (IVUS) investigations of coronary arteries have suggested that luminal enlargement after BA is the combined effect of vessel stretching and plaque reduction (4, 5, 6, 7). The relative contribution of each mechanism, however, varies among reports, which may be explained in part by the fact that arterial response varies with plaque composition (8, 9). Mintz et al. (10) showed, using volumetric IVUS analysis, that axial plaque redistribution may be responsible for plaque reduction at the target site.

As part of the REDUCE (REstenosis ReDUction by Cutting balloon Evaluation) multicenter trial, an IVUS substudy was performed to assess the utility of cutting balloon angioplasty (11). Of the 800 patients enrolled in the REDUCE trial, IVUS was performed in 224 patients, based on operator discretion. However, a total of 180 patients were available for complete IVUS analysis (cutting balloon 89; balloon angioplasty 91).

The IVUS substudy demonstrated the following findings. The overall results suggest that the cutting balloon, using lower balloon inflation pressure, achieves a trend toward larger lumen gain and increased plaque reduction, compared with BA. In noncalcified lesions, the cutting balloon achieves similar luminal dimensions compared with BA, and the mechanisms of acute lumen gain achieved by the cutting balloon are characterized by increased plaque reduction and a trend toward less vessel expansion, compared with those by BA. In calcified lesions, the acute lumen gain achieved by the cutting balloon was significantly larger, through mechanisms similar to those of BA, which may be associated with the presence of dissection generated by controlled cutting.

The REDUCE IVUS study further clarifies that the mechanisms of acute lumen gain through the use of the cutting balloon are different from those of BA. Increased plaque reduction and smaller vessel expansion, as demonstrated in noncalcified lesions, may represent a reduction in vessel wall injury (12,13) and thus potentially contribute to a favorable healing process, as reported previously (14, 15, 16).

Interestingly, for calcified lesions, although the mechanisms of lumen gain was similar, the cutting balloon achieved a larger lumen than BA. The larger lumen gain in the cutting balloon group was associated with the presence of dissection, suggesting that controlled cutting of noncalcified parts of the calcified lesions may in part explain the achievement of a larger lumen gain. These results are consistent with previous studies that included both calcified and noncalcified lesions; patients with dissection had a higher acute gain than patients without dissection.

INDICATIONS

Multiple observational case series from North America, Europe, and Japan—as well as small randomized studies—have documented the safety and utility of cutting balloon angioplasty (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29) and a reduction in restenosis in patients treated with cutting balloon compared with percutaneous transluminal coronary angioplasty (PTCA) (30,31).

However, the use of the cutting balloon is currently confined to its niche application in interventional cardiology. The cutting balloon is useful particularly in the subset of patients having fibrocalcific lesions, small vessels, and
complex lesions, including ostial and bifurcated lesions. Cutting balloons also are useful as an adjunct to brachytherapy for in-stent restenosis and in bare metal stenting in vessels larger than 3 mm.

Drug-Eluting Stents

In the era of drug-eluting stents (DESs), the cutting balloon may be used for intervention in fibrocalcific lesions, in-stent restenosis, small vessels, ostial lesions, and bifurcated lesions.

Figure 11.2. (A) Severe high-grade fibrocalcific ostial RCA lesion in an 81-year-old woman (B) Pretreatment with a 3.5 × 10 mm cutting balloon inflated at 8 atm. (C) Placement of the 3.5 × 24 mm Cypher stent, with about 1 mm of the proximal edge of the stent protruding into the aorta, to ensure complete ostial coverage. (D) Buddy wire technique during stent deployment to ensure adequate backup support when the guiding catheter is backed away from the ostium. Black arrow indicates Choice PT Extrasupport wire. White arrow indicates the BMW wire. (E) Postdilatation with a 4.5 × 15 mm Quantum Maverick Balloon at 18 atm and final flaring of the proximal end of the stent in the aorta. (F) Final angiogram showing an acceptable result. (G) Nine-month follow-up angiogram.

Fibrocalcific Lesions

In pretreatment assessment, the use of IVUS can identify readily severe calcification before stent implantation. However, if IVUS is not available, and a predilatation approach before stent deployment is used, fibrocalcific lesions should be suspected if the conventional balloon fails to fully expand at 10 atm. The cutting balloon then can be used as an alternative to rotational atherectomy to modify the calcified plaque (32, 33, 34, 35, 36, 37, 38, 39, 40, 41) before stent deployment (Fig. 11.2).

Figure 11.2. (continued)

In-Stent Restenosis

Restenotic lesions, especially long, diffuse lesions, are noted to cause a “melon seeding” effect during balloon inflation. Inflation of a conventional balloon can cause the balloon to slip past the lesion and cause injury distally. The cutting balloon minimizes such slippage. In addition, the cutting balloon segments the intimal hyperplasia, which allows for its extrusion through the struts, thereby maximizing the lumen area for DES deployment (42, 43) (Fig. 11.3).

Small Vessels

The cutting balloon is useful in the treatment of small vessels of less than 3 mm diameter. The cutting balloon compresses the plaque, thus creating a larger lumen area for stent placement. Several registry data studies also have reported the advantages of using cutting balloons in small vessels (44, 45, 46).

Ostial Lesions

The “melon seeding” effect is often encountered upon balloon inflation in aorto-ostial lesions. Caution should be exercised in the direct stenting of aorto-ostial lesions, because stent malpositioning or even embolization can occur secondary to the melon seeding effect. Predilatation using a conventional angioplasty balloon may cause balloon slippage and distal injury to the vessels. The cutting balloon minimizes this slippage. Ostial lesions often are fibrocalcific and resistant to conventional angioplasty balloon dilatation (47, 48, 49, 50, 51, 52, 53). The cutting balloon can sever the fibrocalcific strands in short focal lesions, and because the cutting balloon is only 6 mm in length, it can control the injury zone, unlike in conventional BA.

Bifurcation Lesions

The feasibility and safety of the cutting balloon in bifurcation lesions has been reported in several observational
registries (54, 55, 56, 57, 58). Direct stenting and conventional BA in bifurcation lesions may cause plaque shifting. The cutting balloon has been demonstrated to minimize plaque shifting (59). Pretreatment using a sequential cutting balloon inflation in bifurcation lesions before stent deployment in the main vessel, followed by final kissing balloon inflation in both vessels, is one possible approach to the management of bifurcation lesion stenting. Provisional stenting of the side-branch vessel is done when suboptimal results are encountered. In short focal lesions, the cutting balloon is only 6 mm in length, thus controlling the injury zone, when compared to predilatation with a conventional balloon.

EFFECT IN LARGER NATIVE CORONARY ARTERIES

The mode of action of the cutting balloon is to create controlled linear incisions on the atherosclerotic plaque. It was hypothesized that the discrete longitudinal incisions created during balloon inflation might improve the success of angioplasty by reducing elastic recoil and minimizing internal injury, thereby minimizing the neointimal proliferative response. Theoretically, this effect may lead to a lower restenosis rate.

Figure 11.3. (A) High-grade in-stent restenosis of the protected mid left main stem (bare metal stent). (B) Pretreatment with a 3.5 × 10 mm cutting balloon at 6 atm. (C) Angiogram after pretreatment with the cutting balloon. (D) Placement of the 3.5 × 33 mm Cypher Stent extending about 2 mm into the aorta, to ensure full coverage of the ostial left main stem. (E) Postdilatation and flaring of the ostial left main with a 4.5 × 9 mm Quantum Maverick balloon at 18 atm. (F) Final angiographic result. (G) Nine-month follow-up angiogram.

Two randomized trials, the CUBA trial (Cutting Balloon versus Conventional Balloon Angioplasty) and the Cutting Balloon Global Randomized trial, were designed to test whether the use of the cutting balloon conferred a lower restenosis rate in native coronary arteries larger than 3 mm, compared to conventional BA.

Cutting Balloon versus Conventional Balloon Angioplasty Trial

The CUBA trial was a prospective and randomized comparison of cutting balloon angioplasty versus conventional BA in native nonrestenotic coronary arteries. A total of 306 patients
were randomized, with 153 patients in the cutting balloon group and 153 in the convention angioplasty group (60).

Figure 11.3. (continued)

At 6 months follow-up in the CUBA trial, angiography and analysis were performed in 96% of patients. The restenosis rate was 42% in the conventional BA group versus 30% in the cutting balloon angioplasty group (RR = 1.66, 95% CI = 1.28; p = 0.047) (Table 11.1). When the restenosis rate was adjusted for vessel size, vessel location, and clinical presentation, the relative risk for restenosis after conventional BA when compared with cutting balloon angioplasty was 1.73 (9.5% CI = 1.02-2.92, p = 0.03) (61, 62, 63). This study confirms the lower restenosis rate after cutting balloon angioplasty versus conventional BA.

TABLE 11.1. CUBA TRIAL

Procedural Outcome	Cutting Balloon	Standard PTCA	p Value
Reference diameter (mm)	3.00 ± 0.4	2.95 ± 0.4	ns
MLD gain (mm)	1.50 ± 0.5	1.50 ± 0.5	ns
Myocardial infarction	2%	2%	ns
CABG	1%	0%	ns
Protocol success^*	11%	9%	ns
6-month angiographic restenosis	30%	42%	0.047
6-month late loss (mm)	0.37 ± 0.8	0.52 ± 0.7	0.09
^*Angiographic success without stent requirement or crossover.

The Cutting Balloon Global Randomized Trial

The Cutting Balloon Global Randomized trial was a randomized multicenter trial comparing the incidence of restenosis after cutting balloon angioplasty versus conventional BA in 1,238 patients (64); 617 patients were
randomized to cutting balloon treatment, and 621 to coronary angioplasty. The mean reference vessel diameter was 2.86 ± 0.49 mm, mean lesion length 8.9 ± 4.3 mm, and prevalence of diabetes mellitus in patients was 13%.

Repeat angiography was performed at 6 months in 551 (82%) and 559 (80%) of lesions treated with cutting balloon and conventional BA/PTCA, respectively. During the 6-month angiographic follow-up, the primary endpoint of binary angiographic restenosis was not significantly different between the two groups (CB 31.4% versus PTCA 30.4%, p = 0.75) (Table 11.2), and the follow-up minimal lumen diameter and percentage diameter stenosis also were similar.

A nonsignificant reduction in lower absolute late loss at 6 months in the cutting balloon arm (0.43 ± 0.61 versus 0.50 ± 0.60 mm, p = 0.06) failed to translate to lower angiographic restenosis rates, because the cutting balloon achieved a smaller acute gain than did PTCA (1.09 ± 0.54 versus 1.15 ± 0.53 mm, p = 0.04). In addition, the proportional response to injury, as measured by the late loss index, was not different between cutting balloon and PTCA arms (0.49 ± 0.04 versus 0.44 ± 0.05, p = 0.3)

At 270 days, clinical follow-up was available in 580 patients (94%) assigned to cutting balloon and 572 patients (92%) assigned to PTCA. The 30-day major adverse cardiac event (MACE) rate was 3.7% for the cutting balloon group versus 2.7% for the PTCA group (p = 0.34), and the 270-day MACE rate was 13.6% versus 15.1%, respectively (p = 0.47). Freedom from target vessel revascularization, however, was higher in the group treated with the cutting balloon (88.5%), compared with PTCA (84.6%, log-rank p = 0.04). In comparison to the PTCA arm, there was a higher incidence of myocardial infarction (MI), largely non-Q-wave, in the cutting balloon arm (4.7% versus 2.4% for PTCA, p = 0.03) and higher mortality at 9 months (1.3% versus 0.3%, p = 0.06).

TABLE 11.2. CUTTING BALLOON GLOBAL RANDOMIZED TRIAL QUANTITATIVE ANGIOGRAPHIC ANALYSIS

Lesion Characteristic		CB	PTCA	p Value
Immediately after procedure
	Reference vessel diameter (mm)	2.89 ± 0.49	2.93 ± 0.48	0.13
	Minimal lumen diameter (mm)	2.05 ± 0.52	2.13 ± 0.53	0.01
	Residual (%) diameter stenosis	29 ± 14	27 ± 13	0.01
	Acute gain (mm)	1.09 ± 0.54	1.15 ± 0.53	0.04
At 6-mo follow-up
	Reference vessel diameter (mm)	2.79 ± 0.46	2.83 ± 0.47	0.15
	Minimal lumen diameter (mm)	1.63 ± 0.62	1.65 ± 0.61	0.44
	Diameter stenosis (%)	42 ± 19	42 ± 19	0.99
	Binary restenosis rate (>50% stenosis)	31.4%	30.4%	0.75
	Late loss (mm)	0.43 ± 0.61	0.50 ± 0.60	0.06
Values are expressed as percentages (counts/sample size) or mean ± SD.

In summary, the proposed mechanism of controlled dilatation did not reduce the rate of angiographic restenosis for the cutting balloon compared with conventional BA.

SMALL VESSELS

Several registry and observational data studies have shown very encouraging results with the use of the cutting balloon in small vessels, compared with conventional BA (65, 66, 67, 68, 69, 70, 71, 72). Two large randomized trials were conducted to address this issue, the Cutting Balloon Angioplasty for Small Size Vessels (CBASS) trial and the Cutting Balloon Angioplasty versus Plain Old Balloon Angioplasty Study (CAPAS) trial.

Cutting Balloon Angioplasty for Small Size Vessels Trial

The CBASS trial was a multicenter trial to study the safety and efficacy of cutting balloon angioplasty for small vessels of less than 2.6 mm diameter versus conventional BA (73). Ninety-nine patients were studied, of which 50 were assigned to cutting balloon angioplasty and 49 patients were assigned to conventional angioplasty. The 4-month angiographic results were available in all the patients, of which the cutting balloon group showed a restenosis rate of 26% versus 48% restenosis in the conventional BA treatment (p <0.05) (Table 11.3). This preliminary small trial showed a significant benefit for the use of the cutting balloon in the management of small vessels, compared with conventional angioplasty.

Cutting Balloon Angioplasty versus Plain Old Balloon Angioplasty Randomized Study

The CAPAS trial in type B/C lesions was a prospective, randomized, single-center study comparing cutting balloon
angioplasty with conventional BA in small coronary arteries, less than 3 mm in diameter (74).

TABLE 11.3. CBASS TRIAL

4-Month Angio	Cutting Balloon n = 50	Angioplasty n = 49	p Value
% Diameter Stenosis	40 ± 30	51 ± 20	<0.05
Restenosis (%)	26	48	<0.05

Quantitative coronary angiography was performed before and after percutaneous coronary angioplasty and at 3-month follow-up. The primary endpoint was restenosis, defined as ≥50% diameter stenosis at follow-up. Clinical event rates at 1 year were assessed.

A total of 232 patients with 248 lesions were enrolled in the study; 120 lesions were assigned to cutting balloon angioplasty and 128 lesions to BA/PTCA. No differences were present in baseline characteristics between the two groups.

Preprocedural percent diameter stenosis (%DS) was similar (69.8% versus 69.6%). However, postprocedural and follow-up %DS were lower (26.2% versus 28.9%, p = .072; 40.8% versus 47.5%, p = .011) in the cutting balloon angioplasty group.

Angiography was repeated at 3 months in 229 of the 241 lesions (95.0%) eligible for follow-up: 111 of 118 lesions (94.1%) in the cutting balloon angioplasty group and 118 of 123 lesions (95.9%) in the PTCA group.

Restenosis was significantly lower (25.2% versus 41.5%, p = .009) in the cutting balloon angioplasty group (Table 11.4). At 1 year, event-free survival was achieved in 72.8% of the cutting balloon angioplasty group and in 61.0% of the conventional BA group (p = .047). The cumulative 1-year clinical outcome events are shown in Table 11.5, with a target lesion revascularization of 22.1% in the cutting balloon group and 33.9% in the conventional BA group (p = 0.049).

TABLE 11.4. CAPAS TRIAL

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