Predictors of Early and Late New-Onset Atrial Fibrillation in the Course of Acute Myocardial Infarction

We read the article “Early Versus Late New-Onset Atrial Fibrillation in Acute Myocardial Infarction: Differences in Clinical Characteristics and Predictors’’ by Shiyovich et al with interest. ¹ They reported that new-onset atrial fibrillation (AF) during different phases of acute myocardial infarction has different clinical characteristics.

It is well known that AF is a common arrhythmia in the setting of acute myocardial infarction. Predictors of this arrhythmia was evaluated by several studies. ^{2 –4} Shiyovich et al categorized new-onset AF as early and late. They reported the predictors according to this categorization. However, we have some concerns.

First, this is a retrospective study and most data were determined by consulting medical records that could have been incomplete. The duration of new-onset AF is not clear. Did they include patients with very short episodes of AF?

Second, in this study, patients with preexisting AF were excluded. However, they cannot exclude the presence of previous episodes of paroxysmal AF, especially in patients with enlarged left–right atrial dimensions. The authors ¹ reported that they define early-onset AF if onset and termination of AF episode was within 24 hours of admission. However, AF during acute MI may develop before hospital admission. Excluding this group may affect the predictors associated with early AF.

Third, they did not investigate other potential risk factors for new-onset AF, such as reperfusion type, thyroid function tests, medical management during hospitalization period, unsuccessful reperfusion or recurrent ischemia, Killip class, or diastolic function. ⁵

Fourth, they did not provide any data about the management of AF. Did they perform cardioversion for the early AF group? If yes, did they exclude these patients?

Overall, the authors ¹ reported valuable data about the new-onset AF in patients with acute myocardial infarction. We know that there is no clear definition for AF in this setting. However, standardization of study methods may help resolve this issue.