Published online before print June 8, 2006, doi: 10.1161/01.STR.0000227287.30311.54
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(Stroke. 2006;37:1647.)
© 2006 American Heart Association, Inc.
Letters to the Editor |
Response to Letter by Karapanayiotides et al
The Russell H. Morgan Department of Radiology and Radiological Sciences, The Johns Hopkins Hospital, Baltimore, Md
Department of Neurology, The Johns Hopkins Hospital, Baltimore, Md
Suburban Hospital, Bethesda, Md
CVPath, International Registry of Pathology, Gaithersburg, Md
Response:
Drs Karapanayiotides and Bogousslavsky describe their experience using a new ultrasound method for measuring fibrous cap thickness in carotid atheromas. They report an association between mean carotid atheroma cap thickness measurements <650 µm and ipsilateral ischemic events.1 The authors mistakenly surmise that our suggestion that a carotid atheroma cap is probably thin when it measures <200 µm is based on MRI data. In fact, this is based on pathological studies of ruptured plaques. In our article,2 we extrapolated our experience based on coronary atheroma specimen studies (ie, 65 µm threshold for thin caps3) to carotid atheromas, arriving at an estimate of 200 µm. This estimate is also based on our analysis of carotid atheroma specimens. In our experience, the thickness of the cap of a carotid atheroma adjacent to a rupture site is 72±55 µm (mean±SD); 95% of caps measured <165 µm within a limit of only 2 standard deviations (R.V., unpublished data). Therefore, we use 165 µm to define thin caps for carotid atheromas. We contend that the thickness of a ruptured cap is beyond the resolution of MRI, as stated in our limitations,2 but also beyond that of ultrasound. Despite this limitation, evaluation of cap thickness by MRI has enabled discrimination of symptomatic from asymptomatic plaques both retrospectively4 in a manner similar to that described by Drs Karapanayiotides and Bogousslavsky using ultrasound, and prospectively.5 Furthermore, MRI is also capable of detecting juxtaluminal thrombus,6 which is an important marker of rupture that may be difficult to discriminate by ultrasound.
References
1. Devuyst G, Karapanayiotides T, Ruchat P, Pusztaszeri M, Lobrinus JA, Jonasson L, Cuisinaire O, Kalangos A, Despland PA, Thiran JP, Bogousslavsky J. Ultrasound measurement of the fibrous cap in symptomatic and asymptomatic atheromatous carotid plaques. Circulation. 2005; 111: 2776–2782.
2. Wasserman BA, Wityk RJ, Trout HH III, Virmani R. Low-grade carotid stenosis: looking beyond the lumen with MRI. Stroke. 2005; 36: 2504–2513.
3. Burke AP, Farb A, Malcom GT, Liang YH, Smialek J, Virmani R. Coronary risk factors and plaque morphology in men with coronary disease who died suddenly. N Engl J Med. 1997; 336: 1276–1282.
4. Yuan C, Zhang SX, Polissar NL, Echelard D, Ortiz G, Davis JW, Ellington E, Ferguson MS, Hatsukami TS. Identification of fibrous cap rupture with magnetic resonance imaging is highly associated with recent transient ischemic attack or stroke. Circulation. 2002; 105: 181–185.
5. Takaya N, Yuan C, Chu B, Saam T, Underhill H, Cai J, Tran N, Polissar NL, Isaac C, Ferguson MS, Garden GA, Cramer SC, Maravilla KR, Hashimoto B, Hatsukami TS. Association between carotid plaque characteristics and subsequent ischemic cerebrovascular events: A prospective assessment with MRI–initial results. Stroke. 2006; 37: 818–823.
6. Kampschulte A, Ferguson MS, Kerwin WS, Polissar NL, Chu B, Saam T, Hatsukami TS, Yuan C. Differentiation of intraplaque versus juxtaluminal hemorrhage/thrombus in advanced human carotid atherosclerotic lesions by in vivo magnetic resonance imaging. Circulation. 2004; 110: 3239–3244.
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Stroke 2006 37: 1646.
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