Balloon-Assisted Microdissection "BAM" Technique for Balloon-Uncrossable Chronic Total Occlusions

Abstract: Background. After successful guidewire passage, failure to cross the occluded segment with a balloon is the most common cause of procedural failure in coronary chronic total occlusion (CTO) intervention. We evaluated the safety and efficacy of the balloon-assisted microdissection (BAM) technique for treating these complex balloon-uncrossable lesions. Methods. We identified consecutive cases treated with BAM for balloon-uncrossable CTOs between January 2012 and February 2015 at two experienced CTO percutaneous coronary intervention (PCI) centers and reviewed their clinical and angiographic characteristics and procedural outcomes. Results. During the study period, a total of 17 patients had BAM performed for balloon-uncrossable CTOs. Mean age was 65.5 ± 8.7 years and 94% of patients were males who often had prior myocardial infarction, PCI, and coronary artery bypass graft surgery. The most common CTO target vessel was the right coronary artery. Mean J-CTO score was 2.6 ± 1.1. Despite high lesion complexity, overall procedural success was 94% and BAM facilitated success in approximately one-half of these cases. All BAM failure cases except 1 were successfully recanalized utilizing additional techniques. No patient experienced a major complication. Conclusion. BAM is a simple, inexpensive, and safe technique that can facilitate crossing of balloon-uncrossable CTOs and can be considered as first-line treatment for these complex lesions.

J INVASIVE CARDIOL 2016;28(4):E37-E41

Key words: percutaneous coronary intervention, chronic total occlusion, balloon uncrossable

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Balloon-uncrossable chronic total occlusions (CTOs) are lesions that cannot be crossed with a balloon or any microcatheters after successful guidewire crossing. These lesions are encountered in approximately 6% of CTO percutaneous coronary interventions (PCIs)¹ and can be challenging to treat.² Standard techniques such as enhanced guide-catheter support and microcatheter lesion modification³ may fail to treat these lesions. Furthermore, recent published techniques to overcome these resistant occlusions may be difficult to adopt^4,5 and may only be used by highly advanced and experienced CTO operators. We describe a simple balloon-assisted microdissection (BAM) technique to facilitate the balloon crossing of “balloon-uncrossable” CTOs.

Methods

Study design. We examined the procedural characteristics and outcomes of consecutive patients treated at two experienced CTO-PCI centers (University of Manitoba, Winnipeg, Canada and VA North Texas Health Care System, Dallas, Texas) in whom BAM was utilized to treat balloon-uncrossable CTOs between January 2012 and February 2015. Baseline clinical and angiographic characteristics, procedural techniques, and in-hospital outcomes were examined. The study was approved by each center’s institutional review board.

Description of the BAM technique. After successful antegrade crossing of the occluded segment with a guidewire, a small, low-profile, compliant balloon (usually 1.5 mm in diameter) is advanced to the lesion, abutting against the resistant proximal cap. The balloon is then inflated to high pressure until it ruptures and causes microdissections around and into the cap. This weakens the lesion and its cap. When rupture occurs as evident by rapidly decreasing pressure on the endoflator, negative pressure is immediately applied followed by neutral placement to avoid blood entry. BAM can sufficiently modify the plaque to allow subsequent delivery of balloons into the lesion for successful treatment.  This technique is illustrated in Figure 1 and a successful case application is demonstrated in Figure 2.

Study endpoints and definitions. CTOs were defined as coronary obstructions with Thrombolysis in Myocardial Infarction (TIMI) flow grade 0 of at least 3 months duration. Estimation of the occlusion duration was based on first onset of angina symptoms, prior history of myocardial infarction in the target vessel territory, or comparison with a prior angiogram.

Technical success of BAM was defined as successful delivery of balloons and/or microcatheters into the occluded segment immediately after BAM technique with final achievement of <30% residual angiographic stenosis and TIMI 3 antegrade flow through the CTO vessel and its major side branches. Procedural success was defined as technical success without in-hospital major adverse cardiac event (MACE). MACE included death, Q-wave myocardial infarction (MI), recurrent cardiac symptoms requiring repeat target-vessel PCI or coronary artery bypass graft (CABG) surgery, cardiac tamponade requiring pericardiocentesis, or stroke as a result of the CTO-PCI procedure. Significant coronary perforation was defined as perforation requiring pericardiocentesis, embolization, or stent-graft placement. Stent thrombosis was defined according to the Academic Research Consortium definition.⁶Vascular complications were defined as >5 cm hematoma, retroperitoneal bleed, and/or vascular access-site bleeding requiring blood transfusions.

The J-CTO score was calculated as described by Morino et al.⁷Post-PCI MI was defined as two out of three criteria: (1) ischemic symptoms; (2) an increase in creatine kinase (CK) >3x the upper limit of normal; and (3) ischemic changes on electrocardiogram. Cardiac enzymes were routinely performed 12 hours post procedure.  

Statistical methods. Descriptive statistics were used to report the clinical characteristics, angiographic characteristics, and in-hospital outcomes. All procedures were categorized based on use of BAM or no use of BAM and compared in terms of baseline clinical characteristics, angiographic characteristics, and procedural data. Continuous variables were presented as mean ± standard deviation for normally distributed variables or median (interquartile range) for non-normally distributed data and compared with Student’s t-test or Wilcoxon rank-sum test, as appropriate. Categorical variables were presented as percentages and compared with the Chi-square test or Fischer’s exact test, as appropriate. All analyses were performed using JMP version 12.0 (SAS). The level of significance was set at P<.05.

Results

Patient and lesion characteristics. During the study period, BAM was used in 17 patients. Baseline clinical characteristics are presented in Table 1. Most patients were men (94%) with a mean age of 65.5 ± 8.7 years and high prevalence of prior PCI (71%) and prior CABG surgery (53%).  Angiographic lesion characteristics are detailed in Table 2. The right coronary artery was the most common CTO target vessel (71%), with proximal location being the most common lesion site (59%).  The treated CTOs were complex (mean J-CTO score, 2.6 ± 1.1) with long lengths (median, 40 mm) and high prevalence of calcification (76%); 18% of these lesions had a previous failed attempt and almost one-half had blunt-stump proximal cap morphology.

Procedural details and outcomes. Technical details and outcomes are presented in Table 3. Overall, technical success with the BAM technique was achieved in 8 out of 17 patients (47%) and overall procedural success was 94%.  Among 9 patients with unsuccessful BAM, all except 1 patient had successful CTO revascularization after application of additional techniques: excimer laser coronary angioplasty (n = 3), rotational atherectomy (n = 1), subintimal plaque modification (n = 2), and retrograde approach (n = 2). No patient developed in-hospital MACE and no patient experienced coronary dissection or perforation.

There were no differences in clinical characteristics between patients with successful and unsuccessful application of BAM technique. However, the unsuccessful group had higher prevalence of prior CABG, calcification, severe tortuosity, longer occlusion, and higher J-CTO score (Table 4). This group also had smaller reference vessel diameter. There were no differences in procedural success or adverse outcomes between the two groups.

Discussion

Our study demonstrates that the BAM technique can be safely applied for balloon-uncrossable CTOs and is successful in facilitating balloon crossing in approximately one-half of cases.

Failure to cross a CTO with a balloon after successful guidewire crossing is the most common cause of CTO-PCI failure² and is encountered in approximately 6% of CTO-PCI cases.¹ Balloon-uncrossable CTOs can be complex procedures requiring longer procedure and fluoroscopy times and higher contrast volume administration. Techniques to treat balloon-uncrossable CTOs can be broadly classified into two general categories: (1) enhanced guide-catheter support; and (2) plaque modification. Enhanced guide-catheter support can be achieved by using supportive guide-catheter shapes, guide-catheter extensions⁸ and anchoring techniques (side-branch anchor or distal anchor, including subintimal distal anchor⁴). Lesion modification techniques include use of various microcatheters such as the Tornus³ (Asahi Intecc), Corsair, Caravel (Asahi Intecc), Finecross (Terumo), Turnpike, Turnpike LP, Turnpike Spiral, and Turnpike Gold (Vascular Solutions), combined balloon/microcatheters (Threader, Boston Scientific), subintimal plaque modification,⁵ laser,⁹ and rotational atherectomy. However, many of these techniques may be unsuccessful and entail high cost and/or advanced skillsets that may not be widely available. Balloon-assisted microdissection (BAM) is a simple, widely available, and low-cost technique that can be used as an initial strategy to treat these complex lesions. In this technique, a small-diameter balloon (1.2-1.5 mm) is advanced as far as possible into the lesion and inflated until intentional rupture is achieved. When the balloon ruptures, it causes microdissections into the plaque and can sufficiently weaken the lesion to allow subsequent delivery of balloons for predilation and successful stent delivery. As shown in our case series, this technique contributed to successful lesion treatment in approximately one-half of the cases and when unsuccessful, additional techniques were applied to achieve an overall 94% success rate. A high success rate was achieved despite high lesion complexity including multiple prior failed attempts, blunt proximal cap, calcification, long lesion length, and high J-CTO score.⁷ In addition, there was a high number of patients with prior CABG, which has been shown to be associated with lower technical success rate.¹⁰ Despite these highly complex lesions, a 50% success rate is considered favorable given its simplicity and low cost. Therefore, this technique can be considered to be the first-line treatment for balloon-uncrossable lesions.

Technique limitations. Despite its usefulness, the BAM technique also has limitations. First, air embolism could occur after balloon rupture and was observed in 1 case; it was treated conservatively with rapid resolution. Therefore, meticulous balloon preparation is recommended. After balloon rupture, its inner lumen might collapse and entrap the wire, necessitating wire removal along with the ruptured balloon. This may result in procedural failure since lesion recrossing with another guidewire might not be possible, especially in these difficult lesions. This tends to occur more frequently with smaller 1.25 mm-diameter balloons and therefore, we recommend utilizing 1.5 mm-diameter balloons.

Conclusion

BAM is a simple, safe, effective, and low-cost option for treating balloon-uncrossable CTOs and can be considered as the first-line treatment for these complex lesions.

References 

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