LETTER TO THE EDITOR
Reply
Peter Gheeraert, MDa and
José P. S. Henriques, MD
a Department of Cardiology, University Hospital, De Pintelaan 185, B-9000 Gent, Belgium
peter.gheeraert{at}rug.ac.be
We thank J. Mikkelsson for his comments on our article (1). The authors would like to take this opportunity to discuss the effects of patient selection and points of interest in more detail when our results are compared with studies on sudden cardiac death (SCD).
We studied out-of-hospital ventricular fibrillation (VF) in the early phase of acute myocardial infarction (AMI). To compare our study with studies on SCD, two main points deserve attention. First, we focused on the early phase of AMI. In victims of SCD identification of subjects that were in the early phase of AMI is extremely challenging. Standard histological techniques underestimate the true frequency of early AMI. The articles on SCD cited by Mikkelsson confirmed that only 5 to 21% of victims were in the early phase of AMI. Presence of a fresh coronary occlusion or ruptured plaque also varied between 23 and 82%, reflecting heterogeneity of methodology or studied populations. Diagnosis of early phase of AMI in our study was based on ST segment elevation and angiographically confirmed presence of a fresh coronary occlusion. Identical criteria were applied for the control group. Second, we specifically focused on VF and not on all fatal arrhythmias as a whole. Severe bradyarrhythmias are reported up to 30% in SCD (2). In studies on SCD the fatal arrhythmia is seldom specified. In our study VF was confirmed by rhythm recordings. So, studies on SCD are impossible to compare with our study as long as VF, early phase of AMI and coronary anatomy are not simultaneously specified.
The main finding of our study was that acute occlusion in the left coronary artery is associated with greater risk for out-of-hospital VF compared with the right coronary artery in the early phase of AMI. This finding is not the result of differential selection. We fully agree that the AMI patients in our study do not represent all patients with AMI. To reach the group of "AMI with VF," patients had to survive VF. To explain our findings by selection bias, as suggested by Mikkelsson, one has to assume that patients with out-of-hospital VF and occlusion of left coronary artery have a higher probability of being admitted than patients with out-of-hospital VF and occlusion of right coronary artery. To the best of our knowledge, there are no data suggestive of this assumption.
The comments of Mikkelsson and our article raise another important field of interest: What is the effect of site of occlusion on life-threatening bradyarrhythmias in the early phase of AMI? Therefore, studies on SCD that document bradyarrhythmias, early phase of AMI and coronary anatomy would be very interesting.
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References
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1. Gheeraert PJ, Henriques JPS, De Buyzere ML, et al. Out-of-hospital ventricular fibrillation in patients with acute myocardial infarction: coronary angiographic determinants. J Am Coll Cardiol. 2000;35:144–150[Abstract/Free Full Text]
2. Liberthson RR, Nagel EL, Hirschman JC, Nussenfeld SR, Blackbourne BD, Davies JH. Pathophysiologic observations in prehospital ventricular fibrillation and sudden cardiac death. Circulation. 1974;49:790–798[Abstract/Free Full Text]
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