Discussion
Similar to previously reported data, our study showed that nearly 12% of echocardiographic studies resulted in a classification of IndtDFx [15]. The writing committee of the latest American Society of Echocardiography endorse the reporting of LV filling status as follows: “normal, elevated or cannot be determined” especially in cases referred with symptoms of dyspnea and HF, in view of their prognostic information [6].
In this study we have demonstrated that patients with indtDFx by Doppler echocardiography criteria exhibit a similar clinical profile to patients with definite diastolic dysfunction. It was associated with established major cardiovascular disease risk factors and a two-fold relative risk of presenting HF symptoms compared to patients with normal diastolic function as assessed by echocardiography. IndtDFx may not be a benign condition and needs to be clinically defined.
All conventional classifiying parameters were responsible for the inability to determine diastolic function in the indtDFx groop, showing large variability and values overlapping with either groups. The fact that the indtDFx group exhibit similar clinical profile and intermediate parameters compared to DDFx may suggest that most of these patients were at an early stage of DDFx, with an already impaired diastolic function. Furthermore, LA phasic function analysis patients (subgroups) demonstated a similar pattern of clinical and conventional echocardiographic characterstics as our global database cohort and thus were representative of our population.
We found that LA phasic function parmaters like phasic LA minimal volume (LA geometry) and LA resevoir strain (LA function) in IndtDFX and DDFx were significantly different than in NDFx, and thus could be helpful in re- classification of IndtDFX as actual DDFx. Both parameters were probably related to the various aspects of LA remodeling following changes in relaxation and stiffening of the LV resulting in LA enlargement and reduced LA relaxation and contractility. Phasic LA minimal volume index was the only parameter that remained a significant correlates of HF symptoms by multivariate analysis. Interestingly, LA maximal volume, which is the mostly commonly measured parameter and generally associated with prognosis – was not found to be predictive of symptoms when tested along with LA strain and minimal volume. LA minimal volume was previously shown to have a better correlation with LA total ejection fraction compared to the maximal volume. We found LA maximal volume not helpful in redefining diastolic function. This is probably because the minimal volume holds both size and functional information of LA [16].. In a recent study looking at the correlation between LA function and risk of de novo HF admissions, LA function was a stronger predictor than LVEF, LV global strain, or even LA volume index, highlighting the importance of the LA in the evolution and progression of symptoms [17]. Future studies are requested to determine whether LA functional analysis may help re-defining the IndtDFx group [18] and more prospective studies are required to confirm LA minimal volume as a better predictor of outcome.