CORRESPONDENCE: LETTER TO THE EDITOR
Plaque Burden, Intravascular Ultrasound, and Distal Embolization Phenomenon
Italo Porto, MD,
Luca Testa, MD and
Adrian P. Banning, MD*
* Department of Cardiology, John Radcliffe Hospital Headley Way, Headington, OX3 9DU, Oxford, United Kingdom (Email: Adrian.Banning{at}orh.nhs.uk).
Although embolization of atherothrombotic material during stent deployment is probably ubiquitous, its causes and consequences remain poorly characterized. In a recent issue of the Journal, both Kawaguchi et al. (1) and Kawamoto et al. (2) suggested that vessels most likely to sustain distal embolization could be identified using virtual histology (VH) intravascular ultrasound (IVUS) to quantify the necrotic core. It was suggested that patients with plaques exhibiting these characteristics might benefit from selective use of distal protection devices. Neither study suggested that a relationship exists between original plaque volume and the occurrence of embolization.
In our opinion, these studies have a number of limitations. Kawaguchi et al. (1) chose ST-segment re-elevation immediately after stent implantation as a proxy for embolization. This parameter has not previously been linked to the more recognized end points of myocardial blush grade or 90-min ST-segment resolution (3). Additionally, the limited ability of the 20-MHz Eagle Eye IVUS catheter (Volcano Therapeutics, San Diego, California) to identify luminal thrombus may be particularly relevant in their patients who received only aspirin as a procedural antiplatelet therapy. Moreover, the possibility of side branch occlusion during stent deployment as a cause of myocardial necrosis does not appear to have been considered. In patients with stable angina, Kawamoto et al. (2) suggested that plaques with larger necrotic cores were more likely to exhibit high-intensity transient signals detected by a Doppler guidewire. Histopathological correlates between VH-IVUS and pathology are questionable, and neither study uses post-procedure IVUS imaging of residual plaque. Using 40-MHz IVUS imaging, a direct relationship has been demonstrated between the change in plaque volume and evidence of new myocardial necrosis (4). Thus, although it is perhaps intuitive that friable plaque elements are more likely to be liberated than are more readily compressed fibrotic components, further investigation is required.
In the accompanying editorial, Shah (5) questions whether no reflow is merely a marker of myocardial injury or whether it is the cause of further myocardial damage. There is currently no data to support the notion that, in established no reflow, administration of any pharmacologic agent has any impact on subsequent prognosis, and perfusion in areas of new myocardial necrosis remains impaired for at least 24 h despite normal perfusion in viable areas of myocardium subtended by the same vessel (6). These data suggest that no reflow is predominantly a marker of downstream myocardial necrosis. As more diffuse and challenging diseases are being tackled by percutaneous coronary intervention (PCI), further research into the prevention of plaque embolization is essential to allow further improvement in PCI outcomes.
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- Kawaguchi R, Oshima S, Jingu M, et al. Usefulness of virtual histology intravascular ultrasound to predict distal embolization for ST-segment elevation myocardial infarction J Am Coll Cardiol 2007;50:1641-1646.[Abstract/Free Full Text]
- Kawamoto T, Okura H, Koyama Y, et al. The relationship between coronary plaque characteristics and small embolic particles during coronary stent implantation J Am Coll Cardiol 2007;50:1635-1640.[Abstract/Free Full Text]
- Sorajja P, Gersh BJ, Costantini C, et al. Combined prognostic utility of ST-segment recovery and myocardial blush after primary percutaneous coronary intervention in acute myocardial infarction Eur Heart J 2005;26:667-674.[Abstract/Free Full Text]
- Porto I, Selvanayagam JB, Van Gaal WJ, et al. Plaque volume and occurrence and location of periprocedural myocardial necrosis after percutaneous coronary intervention: insights from delayed-enhancement magnetic resonance imaging, thrombolysis in myocardial infarction myocardial perfusion grade analysis, and intravascular ultrasound Circulation 2006;114:662-669.[Abstract/Free Full Text]
- Shah PK. Distal embolization after percutaneous coronary interventions: prediction, prevention, and relevance J Am Coll Cardiol 2007;50:1647-1648.[Free Full Text]
- Selvanayagam JB, Cheng AS, Jerosch-Herold M, et al. Effect of distal embolization on myocardial perfusion reserve after percutaneous coronary intervention: a quantitative magnetic resonance perfusion study Circulation 2007;116:1458-1464.[Abstract/Free Full Text]
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J. Am. Coll. Cardiol. 2008 51: 1324-1325.
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