Striking increases in carotid artery wall thickness in healthy subjects

Background: Atherosclerosis has long been thought to develop over time in a linear manner from gradual wall thickening to advanced thick lesions. However, evidence has emerged indicating a phasic rather than linear progression with time. A major reason for this non-linear pattern appears to be the occurrence of hemorrhages in the arterial wall, although data on this issue are still scarce. We studied the occurrence of temporarily impressive thickenings of the carotid arterial wall in a cohort of healthy postmenopausal women who were followed up for 3 years with regular carotid ultrasound examinations.

Methods: The women were the European participants of a randomized placebo-controlled trial into the effect of hormone replacement therapy on progression of carotid intima-media thickness (CIMT). For a period of 3 years, the women underwent a standardized carotid ultrasound protocol every 6 months. Common, bifurcation and internal carotid segments were scanned on both sides, stored on videotape, and the near and far wall CIMT was measured on defined angles and segments, also in areas of plaque. Adverse events were routinely recorded. At the completion of the study, all segment-specific measurements were evaluated for outliers. Images were retrieved from videotape and evaluated whether the outlier resulted from a real morphological change or 'measurement error'.

Results: The 509 healthy postmenopausal women, free from previous symptomatic cardiovascular disease, underwent 3,812 carotid ultrasound scans during the study, and 44,924 carotid segments were evaluated. In 203 segments of 188 participants outliers were observed. True morphological changes were found in 12 participants, equivalent to a 3-year risk of 2.4%. These changes did not give rise to clinical symptoms. In the 6 women of whom we had follow-up measurements, the changes were reversed within 6-12 months.

Conclusion: We observed acute increases in CIMT among 2.4% of healthy postmenopausal European women followed for 3 years. When assuming these were the result of vessel wall hemorrhages, our findings add to the body of evidence suggesting that vessel wall hemorrhages contribute to atherosclerosis development and also appear to occur clinically silent.