CORRESPONDENCE
Preconditioning, collateral recruitment and adenosine
Fabrizio Tomai, MD, FACC, FESCa,
Filippo Crea, MD, FACC, FESCa and
Pier A. Gioffrè, MD, FESCa
a Divisione di Cardiochirurgia, Università di Roma Tor Vergata, European Hospital, Via Portuense 700, Rome, Italy
We read with interest the recent article by Billinger et al. (1). It shows that the myocardial adaptation to repetitive ischemia during percutaneous transluminal coronary angioplasty (PTCA) is partially due to collateral recruitment, which accounted for 30% of the observed variation in intracoronary ST segment shifts and is mainly related to ischemic preconditioning. These findings are in agreement with several previous reports by our group (2–4) and others (5,6) using the PTCA model of ischemic preconditioning. However, it is surprising that, by contrast to extensive evidence supporting a prominent role for adenosine and its receptors in mediating the cardioprotective effects of preconditioning in both experimental (7–9) and clinical (10–12) studies, Billinger et al. (1) failed to show pharmacologic preconditioning with adenosine during PTCA. However, the authors measured ST segment shifts only 1 min after the beginning of balloon inflation, a period insufficient for the achievement of the full evolution of ST segment shift, as previously demonstrated (6). Furthermore, for the assessment of myocardial ischemia severity, Billinger et al. (1) adjusted ST segment amplitude with QRS amplitude. This adjusted index of myocardial ischemia remains to be validated in the experimental setting of repeated balloon inflations, especially because during PTCA there are changes in the QRS amplitude, which are variably correlated (r2 = 0.29 to 0.81) with those of ST segment shifts (13). Surprisingly, unadjusted ST segment changes, which have been experimentally validated (14,15), are not provided. Thus, it would be interesting to know whether the results obtained by Billinger et al. (1) regarding the effects of adenosine on preconditioning are confirmed when absolute ST segment changes measured after 2 min of balloon inflation are utilized. Similar considerations apply to the relation between changes of ST segment shift and those of collateral flow index. This would make it possible to compare their results with those of several previous published studies on this topic (2–6,10–12,16).
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References
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References