Ventricular Fibrillation Complicating Acute Myocardial Infarction: Limitations of Study

Limitations of Study
Selection of patients for this kind of study is extremely difficult. We have excluded patients with predisposing factors whose role and relevance to the clinical situation studied is not well determined and are of uncertain clinical connection; for example, this study may well be hampered by removal of patients with hypokalemia; however, we believe that in this way a clear distinction may be obtained between delayed repolarization ventricular arrhythmias (a term adopted by Schweitzer and Mark) and VF with the multiform QRS configuration. This concept could be further consolidated by the relative lack of spontaneous conversion, the unlimited course, and the relatively good response to cardioversion of the multiform variety of VF, in contrast to what would be expected, respectively, concerning the clinical course of “torsade de pointes.” In our opinion, these observations may justify this approach to selection, which is particularly essential in patients with AMI. As mentioned before, patients included in this study were admitted to our coronary care unit within two hours of the onset of symptoms. Therefore, it is not inconceivable that the first group of patients in this study may not be representative of the larger number of individuals who died before the arrival of the mobile care unit or admittance to the hospital. One other limitation is the lack of coronary angiography in order to prove or disprove the occurrence of reperfusion.

Conclusions
Based on electrocardiographic criteria, two patterns of VF were recognized during AMI. They were well correlated with preestablished electrocardiographic stages of AMI and differed in their propensity for early recurrence. The basis of this electrocardiographic and clinical distinction is explained most probably by different pathophysiologic mechanisms and electro-physiologic properties of the myocardium. These suggestions remain speculative for the present time. Further correlated clinical-electrocardiographic studies should be considered to work towards a better understanding of the mechanisms involved and their clinical implications.