Our study shows that the tissue Doppler imaging‐derived index E/E′ is useful to predict the prognosis of patients with non‐valvular atrial fibrillation.
Non‐invasive evaluation of diastolic function by Doppler echocardiographic technique has been widely used in daily clinical settings.3,4,5,25,26
Previous Doppler echocardiographic studies have shown that a restrictive diastolic filling pattern or short deceleration time is a poor prognostic indicator in patients with systolic dysfunction.3,4,5
Deceleration time is also measured to estimate pulmonary artery wedge pressure in patients with atrial fibrillation.9,11
Recently, an alternative Doppler method to assess left ventricular filling pressure, namely tissue Doppler imaging, has been proposed and tested.13,14,15,16
The tissue Doppler imaging‐derived index of left ventricular filling, E/E′, has been shown to be useful to assess the left ventricular filling pressure.13,14,15
Nagueh et al14
showed that E/Ew (equivalent to E/E′) correlated well with pulmonary capillary wedge pressure. Similarly, Ommen et al16
compared E/E′ with the directly measured left ventricular filling pressure and reported that E/E′ > 15 indicates a raised left ventricular filling pressure. In addition, E/E′ was shown to correlate with left ventricular filling pressure in patients with non‐rheumatic atrial fibrillation.17
Recent studies have addressed the prognostic implication of E′ or E/E′ in patients with various cardiac diseases.18,19,20,21,27
Hillis et al20
reported that E/E′ is a strong predictor of mortality in patients after acute myocardial infarction. They showed that E/E′ > 15 predict poor outcome in patients with acute myocardial infarction. Wang et al19,27
reported that E′ was a strong predictor of cardiac mortality in patients with various cardiac diseases. More recently, McMahon and colleagues21
showed that E/E′ predicts adverse clinical outcome in children with hypertrophic cardiomyopathy. Our present study showed, for the first time, that E/E′ is the strongest independent echocardiographic prognostic predictor in patients with non‐valvular atrial fibrillation. Interestingly, LV‐DT, which has been known as a strong predictor of mortality in patients with systolic dysfunction, did not predict mortality in patients with non‐valvular atrial fibrillation in our present study. Previous echocardiographic Doppler studies have shown that LV‐DT predicted mortality in patients with sinus rhythm3,4,5
as well as with atrial fibrillation.10
Hurrell et al10
reported that in 74 patients with atrial fibrillation and poor left ventricular function (mean EF 39%), restrictive physiology (short LV‐DT) predicted poor prognosis. The difference between their series and our present study may in part be explained by the difference in our study populations. In our study, > 70% of the patients had normal systolic function (EF > 50%) and mean EF was 56%. Indeed, when we restricted the analysis to patients with decreased left ventricular systolic function (EF < 50%), the Kaplan–Meier cumulative survival curve showed a higher survival rate among patients with LV‐DT > 140 ms than among those with LV‐DT
The incidence of atrial fibrillation increases with age. Among the population aged > 65 years, about 10% have atrial fibrillation. Non‐valvular atrial fibrillation is an important clinical condition not only because of its strong relationship with ischaemic stroke but also as a cause of congestive heart failure and subsequent cardiac mortality and morbidity. Our results may have implications for the risk stratification of this patient population.
There are several limitations in this study. Firstly, we did not measure E and E′ simultaneously. Beat‐to‐beat variation of the Doppler‐derived indices may affect the calculation of E/E′ of patients with atrial fibrillation. Also, the Doppler value may change as left ventricular filling pressure changes. The relationship between serial changes in the E/E′ value and prognosis needs further investigation. Secondly, this was a relatively small, single‐centre, retrospective study. These results therefore need to be confirmed by a larger, prospective, multicentre study. Indeed, the lack of an association between LV‐DT or PV‐DT and prognosis may result from a possible selection bias towards patients with relatively better left ventricular systolic function; thus, our results may need further investigation in a large series including patients with poor left ventricular systolic function. Lastly, the effect of drugs or haemodynamic alteration on E/E′ and, as a result, prognosis has not been investigated.
In conclusion, the Doppler echocardiography and tissue Doppler imaging‐derived index of left ventricular filling, E/E′, is a strong predictor of cardiac mortality in patients with non‐valvular atrial fibrillation.