Calcified coronary nodules: pathophysiology, diagnosis, and interventional challenges

Calcified coronary nodules (CCNs) represent a distinct and under-recognized form of coronary artery calcification with significant implications for percutaneous coronary intervention (PCI). Unlike superficial or sheet-like calcifications, CCNs are characterized by protruding, irregular calcium deposits that disrupt luminal integrity, promote thrombus formation, and hinder optimal stent expansion. They have been implicated in acute coronary syndromes (ACS), in-stent restenosis (ISR), and PCI failure, yet they are underappreciated on angiography. This review provides a comprehensive overview of the pathophysiology, diagnostic modalities, and interventional challenges associated with CCNs. Intravascular imaging, particularly optical coherence tomography (OCT) and intravascular ultrasound (IVUS), plays a crucial role in distinguishing nodular from concentric or superficial calcium, thereby guiding appropriate lesion preparation strategies. It also facilitates differentiation between eruptive and non-eruptive nodules, which exhibit distinct prognostic and therapeutic characteristics. Various calcium modification techniques-including rotational atherectomy, orbital atherectomy, intravascular lithotripsy, and scoring/cutting balloons-offer specific advantages and limitations in treating nodular calcium. We also discuss evolving interventional strategies to optimize PCI outcomes and note that restenosis rates with covered stents are unacceptably high, making them unsuitable as a treatment option. Finally, we highlight the need for further research into hybrid calcium modification techniques and long-term PCI outcomes in patients with CCNs. Coronary artery bypass grafting remains a viable alternative.