Letter by Ryding et al Regarding Article, “Impact of Pretreatment With Clopidogrel on Initial Patency and Outcome in Patients Treated With Primary Percutaneous Coronary Intervention for ST-Segment Elevation Myocardial Infarction: A Systematic Review”
To the Editor:
The meta-analysis by Vlaar et al1 raises an important question about the timing of clopidogrel treatment at the time of primary percutaneous coronary intervention. The conclusion that pretreatment with clopidogrel results in higher arterial patency rates, lower early mortality, and reinfarction is plausible. In our opinion, however, the analysis failed to take account of important confounders. First, we estimate that glycoprotein inhibitor usage was documented in 2803 of 4114 patients in the clopidogrel pretreatment group compared with only 1341 of 4315 patients in the delayed treatment group (P<0.0001). Furthermore, although the data on symptom onset to percutaneous coronary intervention time interval are incomplete, a further bias exists in favor of the clopidogrel pretreatment group (weighted means: 3.2 hours versus 3.8 hours). These 2 variables are likely to have a significant impact on the study outcomes and may be sufficient to account for the effect attributed to clopidogrel.2,3 In our opinion, the benefit of clopidogrel pretreatment in primary percutaneous coronary intervention remains undetermined particularly in the context of adjunctive glycoprotein inhibitor.
Vlaar PJ, Svilaas T, Damman K, de Smet BJ, Tijssen JG, Hillege HL, Zijlstra F. Impact of pretreatment with clopidogrel on initial patency and outcome in patients treated with primary percutaneous coronary intervention for ST-segment elevation myocardial infarction: a systematic review. Circulation. 2008; 118: 1828–1836.
Nallamothu B, Fox KA, Kennelly BM, Van de Werf F, Gore JM, Steg PG, Granger CB, Dabbous OH, Kline-Rogers E, Eagle KA, GRACE Investigators. Relationship of treatment delays and mortality in patients undergoing fibrinolysis and primary percutaneous coronary intervention: the global registry of acute coronary events. Heart. 2007; 93: 1552–1555.