This will be an investigator-initiated, multicentre, single-arm, open-label, prospective observational study. Patients with indication for PCI and undilatable (non-compliant balloon dilatation <80% at burst pressure) or uncrossable (not crossable with a "small-profile balloon" with adequate support, according to operator´s discretion) coronary lesions treated with ELCA will be included. Intravascular imaging will be highly recommendable and analysed in a central core-laboratory. Device success, angiographical success, procedural success, clinical success and related complications will be evaluated. Patients will be followed for 1 year after the procedure and clinical events will be recorded.

Inclusion Criteria:

• Patients aged over 18 years.
• Patients with either stable coronary artery disease or acute coronary syndromes as the clinical presentation.
• Patients with severe coronary lesions (>70% by visual estimation) in native vessels or coronary bypass grafts.
• "Uncrossable" coronary lesions (i.e., lesions that cannot be crossed with a 0.7:1 balloon after successful guidewire passage) or "Undilatable" lesions (i.e., those in which balloon dilation with a 1:1 non-compliant balloon at 18 atm results in less than 80% expansion relative to the distal reference vessel diameter; this group includes both de novo lesions and in-stent restenosis or underexpanded stents).

Exclusion Criteria:

• Patients with known allergies to aspirin (ASA), clopidogrel, prasugrel, or ticagrelor.
• Patients unable to provide informed consent, either personally or through a legal representative.
• Patients with clinical or hemodynamic instability defined as: sustained hypotension (systolic blood pressure ≤ 90 mmHg for ≥ 30 minutes or use of pharmacological and/or mechanical support to maintain an SBP ≥90 mmHg) or evidence of end-organ hypoperfusion including urine output of <30 mL/h, cool extremities, altered mental status, and/or serum lactate >2.0 mmol/L.
• Patients with significant comorbidities and a life expectancy of less than one year.

Patients with indication for PCI and undilatable or uncrossable lesions treated with ELCA

Individual participant data (IPD) will not be publicly shared; however, data sharing may be considered in selected cases upon reasonable request and with sufficient justification.