Discussion
In the current study investigating the prevalence and demographic and
clinical characteristics of AF in patients with de novo myocardial
infarction, we found a lower prevalence rate of 3.1%, in contrast to
previous studies in the literature.1,2 The exclusion
of patients with a previous history of revascularization and diagnosis
of stable coronary artery disease (SCAD) as well as the relatively
younger age of the enrolled population is thought to play a main role in
the lower than expected prevalence of AF in our study. SCAD and AF share
common risk factors and patients with a long history of SCAD and its
risk factors also show increased risk of incident AF.5In addition, coronary revascularization procedures, particularly CABG,
have been found to create a predisposition to incident
AF.6 For this reason, the authors are of the opinion
that the exclusion of patients with SCAD and revascularization history
were the main factors behind the low percentage of AF patients in the
study population. Furthermore, a positive correlation between age and AF
has been confirmed in many registries.7 The relatively
young mean age (approximately 60 years old) of patients enrolled in our
study may also have resulted in the lower prevalence of AF in our study
population. Theoretically, patients without previous diagnosis of SCAD
and/or without history of revascularization may be younger and have
fewer AF risk factors. Although ethnicity may play a role for
differences in the prevalence of AF, no evidence has been reported
showing different rates of AF between Turkey and the rest of the
world.8 However, acute coronary syndrome registries
conducted in Turkey report younger average ages in patients admitted
with acute MI than in European countries and the United
States.9,10 We believe that the younger age pattern
may have an effect on lower AF prevalence in our study than that of
other global registries.
Our study also found that non-ST-elevation myocardial infarction
(NSTEMI) presentation was higher in the AF population than in patients
without AF, with approximately 70% of AF patients presenting with
NSTEMI. Age is a common risk factor of both AF and NSTEMI. The current
literature shows a positive correlation between increasing age and the
rate of NSTEMI in the MI population and a higher prevalence of AF in
patients with non-ST segment elevation acute coronary syndrome
(NSTE-ACS).11 On the other hand, AF with fast
ventricular response can precipitate Type 2 MI that commonly presents
with ST segment changes rather than elevation on admission
ECG.1 However, while this study did not find any
differences in the prevalence of MINOCA between the AF and non-AF
groups, possible type II error cannot be ignored.
Advanced age, female gender, lower LV ejection fraction (LVEF), higher
Killip class, obesity, presence of multiple comorbidities, and
hemodynamic instability are associated with AF.2Similar to previous studies, patients in the AF group were older than in
the non-AF group and the proportion of women to men in the AF group was
higher than that in the non-AF group. Previous registries revealed that
with advanced age, gender difference in MI patients lessens and the
female/male ratio increases.12 AF patients were an
average of twelve years older than non-AF patients in our study, which
may explain the gender difference between the AF and non-AF groups.
Additionally, smoking is more common in men than in women in the Turkish
population.13 The authors believe that the observed
difference in smoking between the groups may be due to the female
dominance in the AF group. Hypertension is an essential predictor of AF
development14 and higher hypertension prevalence in
the AF group can play a role in the development of AF in advanced age
(64.7% vs. 48.5%, p=0.023). In addition, we should pay attention to
type I statistical error in evaluations of differences of gender,
smoking, and prevalence of hypertension in this context. Lower LVEF in
the AF group (45.0% [30.0-50.0] vs. 50.0% [35.0-55.0],
p=0.008) can be explained by the higher burden of comorbidities such as
advanced age and hypertension in AF patients. Loss of atrial kick and
possible tachycardiomyopathy are other factors that may result in lower
EF and have been found to be responsible for worse hemodynamic status
and increased mortality.15 Accordingly, the ratio of
Killip class 3 and 4 patients at admission was higher in the AF group in
our study.
An interesting finding in our study was the relatively low percentage of
patients who were initially treated by the thrombolytic therapy.
ST-elevation myocardial infarction (STEMI) patients made up nearly half
of the study population (46.0%) but only 3.0% of all patients received
thrombolytic treatment before coronary angiography. Even in the AF
group, while 31.3% of patients presented with STEMI, none received
thrombolytic therapy. It is possible that the lower preference for
thrombolytic therapy as an initial reperfusion choice may be related to
the well-organized ambulance system and sufficient number of invasive
cardiology centers which are capable of performing 7/24 primary PCI
around the country.
Oral P2Y12 inhibitor loading was common in both AF and
non-AF patients. Although the AF group was found to have a higher oral
P2Y12 inhibitor loading rate (96.0% vs. 91.8%,
p=0.027) than the non-AF group, this can be an incidental finding and
accepted as an example of type I statistical error. The study also found
the use of oral P2Y12 inhibitors other than clopidogrel
to be relatively common in the AF group, with approximately one third of
patients in the AF group loaded with an oral P2Y12inhibitor other than clopidogrel. We believe that the relatively common
use of more potent P2Y12 inhibitors in AF population was
due to the lower percentage of AF patients who had been already taken
OAC therapy. It can be argued that with common OAC usage, potent
P2Y12 inhibitor loading ratios would be lower.
Ischemic stroke is a devastating complication of AF and MI patients with
AF carry a significant risk of stroke. Previously, it has been reported
that dual/triple therapy by adding an OAC decreases the risk of
stroke.16 Despite this stroke risk, most AF patients
admitted with MI were discharged without any OAC therapy. Many trials
have focused on finding the sweet spot between stroke, stent thrombosis,
and major bleeding risk and compared triple and dual therapy strategies
with different duration and different regimens. Almost all of reported
greater safety with dual therapy with OAC plus clopidogrel than triple
therapy.17 Current guidelines advise personalized
management of these patients according to bleeding and thrombosis
risk.18,19 It is also important to emphasize the low
percentage of oral anticoagulant usage in patients with AF before
emergency admission.
Underdiagnosed/overlooked AF, particularly in asymptomatic patients,
undertreatment, and compliance issues with OAC therapy may be the main
reasons for the lower percentage of OAC use in the study population.
These results show the importance of successful and timely diagnosis of
AF, patient education on OAC therapy, and transparent performance
metrics and guideline adaptation for health providers.
In conclusion, the study reports a lower percentage of AF prevalence in
the de novo MI population than previous studies of enrolled unselected
MI and ACS cohorts. It also demonstrated the underuse of OAC in AF
patients, emphasizing the vital role of opportunistic diagnostic
strategies, patient education, and implementations for guideline
adaptation.
Study limitations: The study had several limitations discussed
below. Regarding the cross-sectional design of the study, it was not
possible to obtain short and long-term prognostic metrics of the patient
population. Due to the relatively small sample size of the AF
population, possible type II statistical errors may have affected the
comparative data. Some demographic and clinical characteristics of the
study population may be specific to the Turkish population and thus not
reflect a global perspective. MI was defined in line with the Third
Universal Definition of Myocardial Infarction. However, the current
Fourth Universal Definition of Myocardial Infarction was published after
the starting date of study and protocol revisions were not made due to
possible risks of harmonization between pre- and post-revision data. AF
diagnosis was based on a12 lead ECG performed at admission, meaning that
incident AF could not be captured and differentiated from existing
chronic patterns. For this reason, the organizing committee required the
completion of a form from the investigators in case with suspicion of
incident AF. Similarly, we did not receive any data about the patterns
of AF (ie first diagnosed, paroxysmal, persistent, etc). A higher rate
of first diagnosed AF patterns may explain the dramatic percentages of
OAC use in the study population.
Author contributions: Concept: A.C, U.O.T.; Design: U.O.T.,
A.C.; Supervision: U.O.T., M.Z., O.E.; Materials: A.C., C.E., G.A.,
Y.D., O.A.O., S.K., Y.C., I.U., M.B.T., R.D., V.P., H.O., M.O., K.T.,
D.K., N.C., M.G., S.I., F.Y.C., H.A., A.A., M.Z., O.E., U.O.T.; Data:
A.C., S.K.; Analysis: A.C., S.K., U.O.T.; Literature search: A.C.,
U.O.T; Writing: A.C., U.O.T; Critical revision: U.O.T., M.Z., O.E.
Funding: This work was supported by the Cardiovascular Academy
Society of Turkey [grant number: KVAK 2018/01].
Acknowledgements: The study was presented at European Society
of Cardiology Congress, Paris 2019.
Conflict of interest: none declared.