Figura 1. Acute thrombotic occlusion of the circumflex artery in right anterior oblique view with ca...

Figura 2. Initial result after Cx rechanneling and distal angioplasty.

Figura 3. Angiographic result after stent implantation in the distal third of the circumflex artery.

Figura 4. “Dogbone” shaped stent underexpanded in its middle third.

Figura 5. Final result of the expanded stent after using the OPN balloon at 50 atmospheres.

Figura 6. Final angiographic result after total stent expansion at high pressure.

Introduction

When dealing with fibrotic and calcified coronary lesions, especially in cases where a stent is underexpanded, non-compliant (NC) balloons are an essential part in the interventional cardiologist toolbox. These balloons are designed with limited expansion capabilities, maintaining their diameter even at high pressure, which makes them ideal for post-dilation of underexpanded stents or the pretreatment of resistant lesions.

In cases of severely calcified plaque, standard balloons may not provide sufficient force to adequately dilate the lesion. Non-compliant balloons, on the other hand, can be insufflated to high pressures without overstretching, providing the radial force needed to fracture resistant calcified plaque and ensure optimal stent expansion. This is particularly valuable when deploying a stent that fails to fully expand due to lesion rigidity, which can lead to stent malapposition and adverse outcomes such as restenosis or thrombosis.

Beyond addressing underexpanded stents, NC balloons are frequently used as a preparatory step in lesions resistant to regular balloon inflation. This strategy ensures that the lesion will be adequately dilated before stenting, thus reducing the risk of future complications.

Compared to more advanced and costly techniques like laser atherectomy, intravascular lithotripsy, or rotational atherectomy, NC balloons are a cost-effective solution in many cases1.

While laser and atherectomy devices are invaluable for certain complex lesions, they involve higher equipment costs and are not always readily available. On the contrary, NC balloons offer a simpler and more affordable approach that is widely accessible and versatile to be used in a variety of challenging scenarios.

In conclusion, in the case presented, NC balloons were an essential component of the interventional toolkit, particularly within the treatment of fibrotic or calcified lesions. Their ability to generate high-pressure insufflation, combined with their cost advantages, makes these devices a practical and cost-efficient option for this type of coronary intervention.

Clinical case

A 57-year-old man presented with intense chest pain lasting 3 hours. He was a chronic smoker for 30 years, had type II diabetes for 15 years, hypothyroidism for 12 years, and hypertension for 10 years. Eight months before, he had suffered a stroke in the right middle cerebral artery, from which he fully recovered with medical treatment. His current medical treatment included aspirin, clopidogrel, atorvastatin, metformin, glimepiride, levothyroxine, telmisartan, and pantoprazole. His hemodynamic parameters were heart rate at 85 beats per minute, blood pressure at 100/70 mmHg, and oxygen saturation by pulse oximetry of 98%. The ECG showed sinus rhythm, with an inferior wall myocardial infarction, and the echocardiogram revealed inferolateral and posterior hypokinesia with an LVEF of 48%. He received aspirin 325 mg, ticagrelor 180 mg, and atorvastatin 80 mg, before being transferred to the cardiac cath lab. Coronary angiography via right radial access showed a normal left main coronary artery, 80% tubular stenosis of the left anterior descending artery (LAD), 100% thrombotic occlusion of the middle left circumflex artery (LCx) (Figure 1), and 90% stenosis of the proximal non-dominant right coronary artery (RCA). A decision was made to revascularize the left circumflex artery, considering it the culprit lesion. The left coronary artery was accessed with a 6-Fr Extra Back Up (EBU) 3.5 guiding catheter, and the lesion was crossed with a 0.014” Runthrough guidewire (Terumo, Japan) and pre-dilated with a 2.0 × 12-mm semi-compliant balloon at 12 atmospheres. About 90% stenosis was observed in the middle circumflex artery, followed by the visualization of 3 branches: obtuse marginal (OM), left posterior descending, and distal circumflex artery (Figure 2). The OM and distal circumflex artery showed significant stenosis: 80%. A decision was made to first place a stent directly in the distal circumflex artery (Figure 3), followed by stent implantation in the middle circumflex artery up to the major OM artery. A separate 0.014” guidewire was used in the distal circumflex artery, and a 2.5 × 24-mm Promus Elite stent (Boston Scientific) was deployed at 14 atmospheres in the middle third. After stent implantation, a waist observed in the mid-stent segment was post-dilated with a 2.75 × 8-mm non-compliant balloon at 16 atmospheres. However, residual stenosis persisted, and the balloon maintained a “dogbone” shape (Figure 4). Several attempts at gradual, controlled, and cautious insufflation at high pressure, up to 24 atmospheres, failed. An attempt was made with a previously used 2.5 × 15-mm OPN balloon (SIS MEDICAL AG, Switzerland), which also failed. A decision was then made to use a 2.0 × 10-mm OPN NC balloon as a last resort. This balloon went over the lesion and was gradually and cautiously insufflated at very high pressure, until the waist ultimately disappeared at 40 atmospheres (Figure 5). The stented segment was then post-dilated with the 2.75 × 8-mm NC balloon at 14-18 atmospheres. The LCx-OM lesion was then adequately dilated with a 2.5-mm NC balloon, and a 2.75 × 33-mm Xience Prime (Abbott, USA) stent was deployed from LCx-OM at 12 atmospheres. The stented segment was finally post-dilated with good final TIMI III flow (Figure 6).

Discussion

Fibrotic and calcified lesions are occasionally found during primary angioplasty2. They are more commonly seen in elderly patients with hypertension, diabetes, and renal insufficiency.

Fluoroscopic visualization of calcium is usually inadequate unless the lesion is highly calcified. Assessing highly fibrotic lesions using conventional angiography is also very difficult. In this case, direct stent implantation in the circumflex artery was initially considered as feasible and, possibly, the best alternative, considering acute coronary syndrome (ACS) as the clinical presentation. In ACS, direct stent implantation has been found to be superior to routine balloon pre-dilation as it avoids distal microembolization, slow flow, and thrombi migration3. However, we did not expect the highly fibrotic nature of the lesion. Since intravascular imaging was not available in the cath lab, we were unsure whether the lesion was fibrotic, calcified, or a combination of both.

The stented segment failed to dilate with a large non-compliant balloon at quite high pressure4. A smaller OPN NC balloon, which was 0.5 mm smaller than the vessel size, was very helpful and ultimately dilated the stent at 40 atmospheres.

While manufacturer guidelines recommend insufflating this balloon up to a maximum pressure of 35 atmospheres5, there have been reports of this balloon being used with up to 50 atmospheres. The key is to reduce the balloon size 0.25-0.5 mm smaller than vessel size before moving to higher pressures.

Furthermore, insufflation should be gradual and slow. There should always be a lined stent ready in case of rupture or urgency, especially when exceeding the recommended maximum pressure. We should note that other approaches include Shockwave IVL balloons and laser, but these options are quite expensive compared to the one we chose on this occasion6, 7.

There are several ongoing studies to elucidate between using high-pressure non-compliant balloons and coronary ultrasound system Shockwave IVL (Shockwave Medical, Inc. Santa Clara, CA, USA).

The high-pressure OPN balloon is being compared with Shockwave IVL in the ISAR-CALC2 (Comparison of Strategies to Prepare Severely Calcified Coronary Lesions; NCT05072730) study8, a trial in patients with severely calcified coronary lesions where non-dilatable coronary lesions are randomized to OPN or IVL. The primary endpoint of that study is the final minimal luminal diameter after stent implantation.

Finally, the VICTORY (Value of IVL Compared to OPN Non-Compliant Balloons for Treatment of Refractory Coronary Lesions; NCT05346068) study is a non-inferiority study to compare the impact of IVL with that of high-pressure balloons on final expansion, as assessed with optical coherence tomography in 280 patients with calcified coronary lesions.

Conclusion

In our case, an OPN balloon with a slightly smaller profile than the vessel diameter was used as a desperate measure to achieve adequate expansion of the severely underexpanded stent segment. Calcified and highly fibrotic lesions are a challenge for cardiologists and require careful management. Other approaches include the use of IVL balloons and laser atherectomy, but these approaches are limited by their higher cost and may not be routinely available in all cath labs.

1. Secco G, Ghione M, Mattesini M, et al. Very high-pressure dilatation for undilatable coronary lesions: indications and results with a new dedicated balloon. Eurointervention 2016:12:359-365.

2. Caiazzo G, Di Mario C, Kedhi E, De Luca G. Current Management of Highly Calcified Coronary Lesions: An Overview of the Current Status. J Clin Med 2023 Jul 23;12(14):4844.

3. Cosansu K, Ureyen CM, Vatan MB, Agac MT, Kilic H, Akdemir R. Impact of direct stenting on clinical outcomes for small vessel coronary artery disease in patients undergoing primary percutaneous coronary intervention for ST-elevation myocardial infarction. Postepy Kardiol Interwencyjnej 2019;15(4):404-411.

4. Raja Y, Routledge HC, Doshi SN. A noncompliant, high-pressure balloon to manage undilatable coronary lesions. Catheter Cardiovasc Interv 2010; 75:1067-73.

5. Díaz JF, Gómez-Menchero A, Cardenal R, Sánchez-González C, Sanghvi A. Extremely high-pressure dilation with a new noncompliant balloon. Tex Heart Inst J 2012;39(5):635-8.

6. Pham V, Bonnet M, Varenne O, et al. In-stent use of intravascular coronary lithotripsy for restenosis and stent underexpansion: a multicentre experience. Can J Cardiol 2022;38:1474-5.

7. Tovar Forero MN, Sardella G, Salvi N, et al. Coronary lithotripsy for the treatment of underexpanded stents: the international and multicentre CRUNCH registry. EuroIntervention 2022;18:574-81.

8. Scalamogna M, Abdel-Wahab M, Mashayekhi K, et al. Randomized ComparIson of Strategies to PrepAre SeveRely CALCified Coronary Lesions 2: Design and Rationale of the ISAR-CALC 2 Trial. Cardiovasc Rev Med 2023;49:22-27.

9. Riley RF, Patel MP, Abbott JD, et al. SCAI Expert Consensus Statement on the Management of Calcified Coronary Lesions. J Soc Cardiovasc Angiogr Interv. 2023;3(2):101259

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Failed conventional non-compliant balloon therapy in under expanded stent during acute coronary syndrome: Undersized non-compliant balloon to the rescue!

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