DISCUSSION.
In this population of asymptomatic patients with sAR and normal LV systolic function, baseline diastolic parameters were prognostic markers of cardiovascular events; among them, LASr played a strong independent predictor role. In addition, our results also showed that LV volumes had greater prognostic value that LV diameters in patients with asymptomatic sAR.
In accordance with current clinical practice guidelines (1), aortic valve replacement in patients with sAR should be limited to symptomatic patients or those with LV dysfunction. However, there are possible advantages of an early surgery in valvular heart disease in order to prevent sudden cardiac death, persistent LV systolic dysfunction or worse perioperative and postoperative outcomes. In addition, considering the development of new percutaneous treatments less aggressive than cardiac surgery, identifying those conditions associated with a worse prognosis and who may benefit from an early intervention, seems important.
Previous studies have analyzed the role of the diastolic function in sAR undergoing aortic valve replacement. Ma et al described that LV diastolic disfunction, analyzed by the integration of 2 echocardiographic parameters (LA volume index and E/e’ ratio) is highly prevalent in patients undergoing aortic valve replacement and might improve after surgery (11). In a similar way, Cayli et al (12) reported that diastolic function is a reliable parameter in predicting outcomes in patients with sAR and LV dysfunction. They found that preoperative diastolic disfunction had an adverse impact on the recovery of the cardiac function after surgery and justify this finding due to the correlation of the myocardial fibrosis and worse diastolic function. Kim et al , also found that preoperative E/e’ ratio was correlated with postoperative improvement of LVEF (13).
To the best of our knowledge, this study is the first to evaluate the clinical relevance of baseline diastolic function parameters in patients with asymptomatic sAR. In our sample, E wave, E/e´ratio, SPAP and LA size and function, have significant prognostic value in these patients. Among the analyzed diastolic function parameters, we found that LASr played a strong independent predictor role in outcomes, stronger than LA diameter and LA volume. In patients with sAR, the volume and pressure overload promote LV dilatation and eccentric hypertrophy; in this context, LA function estimated by strain can be reduced even in the absence of LA dilatation, mainly due to interstitial fibrosis, and reflects LV filling pressure. In fact, LA volume has been shown to have low sensitivity in the early detection of LA dysfunction in the setting of LV diastolic dysfunction (14).
There are few data available on AR and LA function and its prognosis implications. Salas Pacheco et al (15) demonstrated that in patients with severe aortic disease (AR and aortic stenosis) LASr was the main variable associated with pulmonary hypertension, they considered that the maintenance of LASr function may be one explanation for the absence of pulmonary hypertension in some patients with severe aortic disease. In isolated aortic stenosis, LA enlargement is recognized as a marker of aortic stenosis severity as well as predictor of postoperative clinical outcomes independently of mean transaortic gradient and LV mass (16). Even more, LASr has been shown as an independent predictor of prognosis in patients with aortic stenosis (17).
We used automated quantification technique for the LA strain assessment, which has the potential advantages of time saving and greater accuracy and reproducibility of the measurements (18). Its implementation could lead to simplify these measurements, making it possible to obtain the deformation parameters in the daily clinical practice.
Finally, although the objective of the study was to analyze diastolic function in patients with sAR, an interesting finding has been that LV volumes have more prognostic value than LV diameters. This finding is in accordance with current guidelines (8) that considered the LV size should be routinely assessed by calculating volumes and the biplane method as the currently recommended 2D method to assess LVEF, however the indications for valve replacement in sAR are still based on LV diameters (1). Previous studies described that LV long axis diameter is closely related with LV systolic and diastolic function in patients with chronic severe AR and that LV long axis function is impaired prior to deterioration of LV global systolic function in these patients, which might indicate subclinical LV dysfunction (19). Therefore, a global assessment of the LV size and function seems necessary, beyond that provided by the determination of isolated diameters.
Although further studies, with large sample size, are required to stablish cut off points, we believe that careful assessment of diastolic function including LA strain, could be useful to identify high risk patients who could benefit from shortening follow up periods and early aortic surgery.