Discussion
In our study, the value of AEMD durations measured with the co-use of
preoperative ECG and TTE (using TDI) in predicting PoAF was investigated
in isolated CABG patients. It was found that the AEMD durations were
statistically significantly longer in our group with PoAF. Although the
difference between the groups in the LA antero-posterior diameters was
not detected in TTE measurements, LA maximum volume was significantly
higher in the group with PoAF. LV lateral Ea and LV medial Ea velocities
were found to be lower in the group with PoAF, and this was an
indication that diastolic dysfunction was more common in the group with
PoAF. Also, LA lateral AEMD was found as an independent predictive
factor in the multivariate logistic regression analysis we conducted to
determine predictors for PoAF development.
PoAF is a cardiac arrhythmia that increases morbidity and mortality by
affecting ventricular functions, causing hemodynamic impairment and
increasing the risk of thromboembolic events. Its incidence after
cardiac surgery is 20-40% (1). The PoAF incidence was 26.88% in our
study, which included isolated CABG patients. Several studies were
conducted to identify the risk factors of PoAF development. Advanced
age, high body surface area, white ethnicity, hypertension, LV
hypertrophy, use of preoperative digoxin, obstructive pulmonary disease,
presence of postoperative LV diastolic and systolic dysfunction,
preoperative high LA volume measurement, presence of postoperative low
atrial filling fraction, and increased adrenergic drug use after surgery
were associated with PoAF development (9-16). Also, the use of P wave
duration with signal-averaged ECG to predict PoAF development was
evaluated, and it was found that patients developing PoAF had
preoperative prolonged P wave durations (17). In fact, when all these
risk factors are evaluated, all of these parameters appear before usas
the cause or result of atrial remodeling. Atrial remodeling triggers the
development of PoAF by causing the development of multiple reentrant
waves that initiate and possibly maintain AF (18).
The main finding of our study was that the AEMD durations measured by
ECG and TTE (using TDI), which is a noninvasive method, was
significantly longer in the group with PoAF. It is recently acknowledged
that AEMD duration is a non-invasive evaluation method of atrial
conduction time, and AEMD duration measurement is an easy, fast and
reliable method. AEMD is defined as the delay between the detected
electrical activity onset (P wave onset in superficial ECG) and the
contraction in atrial myocardium (“late diastolic wave = Aa wave”
evaluated with TDI). It was emphasized in many studies that the
prolongation of AEMD durations was the independent marker of new-onset
or recurrent AF (19-21). Determining the P wave duration in
signal-averaged ECG is also useful for predicting the atrial
electromechanic conduction times, but its use in clinical practice is
limited because it requires special equipment, and evaluation of its
results is time-consuming. However, AEMD, which is a new
echocardiographic parameter, was confirmed to be correlated with P wave
durations detected by using signal-averaged ECG (17,20).
In a study conducted by Özlü et al., it was reported that LA maximum
volume and AEMD duration were the independent predictors of PoAF
development after CABG surgery (23). Although their results support the
results of our study, unlike our study, only inter-atrial
electromechanical delay (the difference between LV lateral AEMD and RV
lateral AEMD) was evaluated in this study. In another study conducted by
Fujiwara et al., 88 off-pump CABG patients were included, AEMD durations
were measured with preoperative TTE (using TDI), and in addition, left
atrial volume index (LAVI) was calculated (24). Patients were monitored
with ECG telemetry for 7 days postoperatively. As a result, they
concluded that PoAF was detected in 35 patients (39.8%), and the AEMD
duration (OR: 1.11, 95% CI: 1.06-1.16, p = 0.0001) and LAVI (OR: 1.11,
95% CI: 1.02–1.20, p = 0.01) were independent predictors of PoAF
development with multivariate logistic regression analysis. They also
conducted ROC Curve Analysis, and reported that AUC: 0.85 for AEMD
(sensitivity: 74.3% and specificity: 86.8%) (23). Although a different
CABG technique was applied in this study compared to our study, our
results were similar. In our study, we also found the LA lateral AEMD
was an independent predictive factor for PoAF development (OR: 1.03,
95% CI: 1,001-1.06, p=0.04); and AUC: 0.741 for LA lateral AEMD in ROC
Curve analysis (95% CI: 0.633-0.849, p <0.001). LA lateral
AEMD duration is significantly correlated with LA diameter and LA
maximum volume (25). These data may explain the importance of AEMD
durations, which is an indicator of pathological changes in the atrium,
for predicting PoAF. The LV lateral AEMD parameters were not included
the univariate and multivariate analysis because EMD parameters were
similar in atrial and ventricular site.
There are limited studies emphasizing the importance of AEMD in
predicting the development of PoAF in other cardiac operations such as
aortic valve and mitral valve surgeries (26,27). Takahashi et al.
monitored patients who underwent aortic valve replacement with ECG
telemetry for 7 days, and reported that the PoAF incidence was as high
as 65% (41 of 63 patients). They measured the AEMD duration with
preoperative TTE (using TDI), and concluded that it was an independent
predictor for the development of POAF (OR: 1.07, 95% CI: 1.02–1.13; p
= 0.0072) (24). In the same center, PoAF development was investigated in
patients with mitral valve replacement due to mitral stenosis, and as a
result, LA lateral AEMD duration was found to be an independent
predictor for the development of POAF (OR, 1.04; 95% CI: 1.01–1.07; p
= 0.0048). Also, in ROC Curve Analysis, the AEMD duration cut-off value
for the development of POAF was reported as 159.4 ms (27). Unlike our
study, in these studies, the AEMD time was taken as the time between the
P wave start at ECG and the mitral lateral Aa peak point measured with
TDI; however, in our study, the time between the onset of the mitral
lateral Aa was measured.
In the present study, it was concluded that advanced age, hypertension,
LA maximum volume height and the increase in LA lateral AEMD, which is a
marker of diastolic heart failure, are risk factors for the development
of PoAF. The presence of LV diastolic dysfunction in predicting PoAF
development comes to the forefront in many studies unlike LV systolic
dysfunction (16, 19). In our study, we believe that the significantly
lower LV lateral Ea and LV medial Ea velocities, among the parameters
indicating LV diastolic function in the group with PoAF, is the probable
cause of high PAP and diuretic usage rates in the group with PoAF. In
their prospective study that included 275 elective CABG patients, Gibson
et al. reported that LV systolic function was not an independent
predictive factor for PoAF (19). Similarly, in our study, EF values were
similar in groups with and without PoAF.
Our study had some limitations. One of the limitations of the study was
that it had a single-centered, and non-randomized design with a
relatively low number of patients. Another limitation was that our
results are limited to postoperative new-onset, in-hospital AF, and the
development of PoAF after the patients were discharged was not
evaluated. Also, the development of PoAF is multifactorial; and it was
another limitation that only parameters that had possible major impacts
(e.g. age, hypertension, conventional TTE and TDI measurements, etc.)
were included in the statistical evaluation of our study data. For this
reason, the predictive effect of AEMD durations on the development of
PoAF must be confirmed with broader prospective studies with longer
follow-up times in patients undergoing CABG.