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Re: Endothelial dysfunction and necrotic core plaques

To the Editor: We read with great interest the paper published by S Lavi et al [1] and feel that it is worthy of comment. We admire the foresight and technical expertise that has gone into creating this study, to try and prove a worthy concept. However, we do have an issue regarding the measurement of Necrotic Core in minimal plaques. The authors state that after selecting the appropriate frames "two independent investigators" measured each frame and the results were calculated. Sections with endothelial dysfunction had larger necrotic core plaques: 0.13 (0.03– 0.33) mm2 vs 0.0 (0.0–0.07), p<0.001 and more dense calcium: 0.03 (IQR 0.0–0.13) mm2 vs 0.0 (0.0– 0.10) mm2, p<0.01).

The absolute value of these numbers calculated for constituent plaque area is very small (in keeping with the modest disease) Have the authors performed intra and inter-observer variability testing to prove that they are able to reproduce this level of accuracy? Having analysed thousands of IVUS-VH frames and published work on IVUS-VH variability [2], we are aware that minimal discrepancies in manual border detection, between operators, can significantly influence calculated plaque measurements.

If the authors cannot prove from an in-house variability study that their individual variability measurements are less than the calculated plaque areas, then their results are invalid. We would be grateful for a response to this important measurement issue.

References

1. S Lavi, J-H Bae, C S Rihal, et al. Segmental coronary endothelial dysfunction in patients with minimal atherosclerosis is associated with necrotic core plaques. Heart 2009;95:1525–1530. doi:10.1136/hrt.2009.166017