Letter by Niccoli et al Regarding Article, “Presence of Older Thrombus Is an Independent Predictor of Long-Term Mortality in Patients With ST-Elevation Myocardial Infarction Treated With Thrombus Aspiration During Primary Percutaneous Coronary Intervention”
To the Editor:
We read with great interest the article by Kramer et al1 on the association between thrombus age and long-term mortality in patients with ST-elevation myocardial infarction undergoing primary percutaneous coronary intervention. They propose that thrombus composition and thrombus age are associated with long-term clinical outcome after the adjunctive use of mechanical devices during primary percutaneous coronary intervention. Instead, we think that, rather than being a predictor of long-term mortality, older thrombus seems to be a predictor of the no-reflow phenomenon, which is known to affect prognosis.
First, patients with older thrombus had a higher incidence of distal embolization compared with patients with fresh thrombus (18% versus 12%, P=0.01) and a trend toward a lower rate of thrombolysis in myocardial infarction flow 3 at the end of the procedure (89% versus 92%, P=0.08). Both variables are related to the no-reflow phenomenon, which has been shown to carry a higher risk of mortality at follow-up.2 Furthermore, patients with older thrombus had a longer total ischemic time compared with patients having fresh thrombus (4.1±4.3 hours versus 3.3±2.4 hours, P=0.001), which would further enhance the possibility of structural no-reflow due to microvascular anatomic alterations.3 Unfortunately, the authors did not show the rate of final myocardial blush grade or ST-segment resolution, which are better known diagnostic tools for no-reflow in their analysis.4
Taken together, these considerations led us to suppose that the prognostic effect of older thrombus may be related to its association with no-reflow. Although multivariable analysis also includes final thrombolysis in myocardial infarction 3 as a measure of no-reflow, the phenomenon may be largely underestimated because ≤50% of patients’ no-reflow occurs in the presence of thrombolysis in myocardial infarction flow 3 when assessed by myocardial blush grade or lack of ST-segment resolution. We think it would be of interest to show in the multivariable model the risk associated with the presence of older thrombus after including no-reflow defined using expanded angiographic criteria or the ST-segment resolution.5
Kramer MC, van der Wal AC, Koch KT, Ploegmakers JP, van der Schaaf RJ, Henriques JP, Baan J Jr, Rittersma SZ, Vis MM, Piek JJ, Tijssen JG, de Winter RJ. Presence of older thrombus is an independent predictor of long-term mortality in patients with ST-elevation myocardial infarction treated with thrombus aspiration during primary percutaneous coronary intervention. Circulation. 2008; 118: 1810–1816.
Ito H, Okamura A, Iwakura K, Masuyama T, Hori M, Takiuchi S, Negoro S, Nakatsuchi Y, Taniyama Y, Higashino Y, Fujii K, Minamino T. Myocardial perfusion patterns related to thrombolysis in myocardial infarction perfusion grades after coronary angioplasty in patients with acute anterior wall myocardial infarction. Circulation. 1996; 93: 1993–1999.
Turschner O, D'hooge J, Dommke C, Claus P, Verbeken E, De Scheerder I, Bijnens B, Sutherland GR. The sequential changes in myocardial thickness and thickening which occur during acute transmural infarction, infarct reperfusion and the resultant expression of reperfusion injury. Eur Heart J. 2004; 25: 794–803.
Jaffe R, Charron T, Puley G, Dick A, Strauss BH. Microvascular obstruction and the no-reflow phenomenon after percutaneous coronary intervention. Circulation. 2008; 117: 3152–3156.
Niccoli G, Giubilato S, Russo E, Spaziani C, Leo A, Porto I, Leone AM, Burzotta F, Riondino S, Pulcinelli F, Biasucci LM, Crea F. Plasma levels of thromboxane A2 on admission are associated with no-reflow after primary percutaneous coronary intervention. Eur Heart J. 2008; 29: 1843–1850.