MILOU: Minimize Intra Luminal Obstructive Underexpansion: A Prospective, Multi-Center Randomized Trial for the Evaluation of Calcified Coronary Lesion Preparation With the Naviscore Scoring Balloon

Percutaneous transluminal coronary angioplasty (PTCA) is the main technique in percutaneous coronary intervention (PCI). It aims to restore coronary blood flow by mechanically enlarging a stenotic arterial segment through controlled balloon inflation within the vessel lumen. The acute luminal gain with balloon angioplasty is the result of multiple mechanisms, ranging from percolation and longitudinal redistribution of atheroma, to plaque fracture, and overstretching of the vessel wall, often accompanied by intimal tearing and medial dissection. While contemporary drug-eluting technologies have significantly improved long-term clinical outcomes, fibrocalcified atheromatous intracoronary plaques still present a significant challenge for stent crossing and optimal deployment.

Research has demonstrated that suboptimal stent expansion and malapposition are significant contributing factors to restenosis and stent thrombosis rates, regardless of the type of stent used. Intravascular imaging registries have identified that twenty to thirty percent of deployed stents remain under-expanded or malapposed in daily clinical practice. Severe coronary calcification can make it difficult to deliver devices and can limit the expansion of stents, which can result in suboptimal improvement in blood flow and an increased risk of adverse events, including target lesion failure. Furthermore, heavily calcified lesions have been found to be associated with higher rates of vessel dissection, perforation and impaired anti-proliferative drug delivery, resulting from the mechanical barrier of the calcium burden.

In order to achieve successful stent deployment, optimal preparation of fibro-calcific lesions is essential and involves a number of plaque modification strategies. Focused force angioplasty is a procedure that targets specific locations of the plaque, focusing inflation forces on the area to induce localized stress and facilitate cracking. It is crucial to ensure that the pre-dilatation balloon is correctly sized to maximise safety by minimising the risk of advanced coronary perforation or severe medial damage. It is imperative that sizing compliance chart data is followed rigorously, as compliant balloons can display an unpredictable non-linear expansion behaviour at higher pressures, whereas non-compliant balloons maintain a stable volume, concentrating their dilating force directly at the calcified site up to their rated burst pressure. Semi-compliant pre-dilatation balloons often expand asymmetrically in resistant lesions, increasing the risk of edge dissections. The sizing and performance of scoring devices and non-compliant balloons remains limited in contemporary clinical literature. This randomised trial is designed to evaluate the post-market clinical performance, safety and comparative effectiveness of the Naviscore scoring balloon catheter manufactured by iVascular.