Frequency and evolution of thin-capped fibroatheromas in left main coronary artery as assessed by serial virtual histology intravascular ultrasound analysis.

Background: The objective of the current study was to assess thin-capped fibroatheroma (TCFA) of the left main coronary artery (LMCA) and its changes after statin therapy.

Methods: We assessed the frequency and distribution of virtual histology intravascular ultrasound (VH-IVUS) thin-capped fibroatheroma (VH-TCFA) in the LMCA in 500 patients. Serial VH-IVUS examinations were available in 50 patients at 12-month follow-up.

Results: The incidence of LM-TCFA was 8.8% (44/500). IVUS LMCA length was longer in patients with VH-TCFA vs without VH-TCFA. Reference external elastic membrane (EEM) area was similar, but reference lumen area and minimal lumen area were smaller in LMCA with VH-TCFA vs without VH-TCFA (P<.001). LMCA with VH-TCFA had a higher plaque burden (P<.001), a larger necrotic core area (P<.001), and more dense calcium (P<.001) at the maximum necrotic core (NC) site vs LMCA without VH-TCFA. In patients with an LMCA length greater than the median, 62% were located in the distal half of the LMCA. After 12 months of statin therapy, only 44.4% (4/9) of VH-TCFA had evolved to a non- VH-TCFA phenotype and 3 new VH-TCFA had appeared.

Conclusion: VH-TCFAs are clustered in the distal half of the LMCA with infrequent positive remodeling. It might persist despite the usual dose of statin therapy. Further study should confirm the changes in large vessels like the LMCA.