Strain is now an Integral Component in Left Ventricular Diastolic Function Assessment

Abstract This editorial reviews the evolving role of strain measurements in the assessment of left ventricular diastolic function (DF) using echocardiography, with a focus on key guidelines from the American Society of Echocardiography (ASE) and the British Society of Echocardiography (BSE). Both organizations now incorporate various strain parameters, including global longitudinal strain (GLS), left atrial reservoir strain (LARS), and left atrial contractile strain (LACS), within their diagnostic algorithms to improve evaluation of DF and left ventricular filling pressure (LVFP). Complexities of DF evaluation, the need for updated laboratory equipment and expertise, and the importance of these advanced measures in guiding patient care have been emphasized. Keywords: diastolic function, guidelines, strain, left ventricle, left ventricle filling pressure, left atrial mean pressure Editorial Diastolic function (DF) of the left ventricle is typically the first parameter affected in most cardiac conditions. Its assessment is crucial for the comprehensive evaluation of cardiac patients, particularly those presenting with shortness of breath or symptoms of heart failure. Echocardiography remains the most effective and widely available tool for this purpose. Unlike systolic function, which can be evaluated using a limited set of parameters such as ejection fraction (EF) or global longitudinal strain (GLS), assessment of DF is more intricate, requiring the acquisition and analysis of multiple parameters that are synthesized through sophisticated algorithms to reach a conclusion. The assessment process generally consists of three steps: first, the presence of diastolic dysfunction (DD) is determined; next, left atrial mean or left ventricular filling pressure (LVFP) is assessed (normal or increased), and finally, DD is graded. Guidelines for Diastolic Function Assessment Numerous guidelines have been proposed for the evaluation of left ventricular DF. The American Society of Echocardiography (ASE) leads in this area, publishing three sets of guidelines in 2009, 2015 (European association of cardiovascular imaging also contributed), and 2025 [1-3]. The British Society of Echocardiography (BSE) released their first guidelines in 2013 and updated them in 2024 [4]. Other agencies have also contributed with guidelines on this topic. Initially, both ASE and BSE guidelines considered EF in the assessment of LV DF, offering separate algorithms for patients with normal and reduced EF. However, in its most recent edition, ASE has removed this dichotomy, now analyzing all patients using a unified algorithm. Parameters and Algorithmic Approaches Basic parameters (labelled as primary and secondary by ASE, or routine and supplementary by BSE) include flow velocities, time durations, and ratios measured at three sites: trans-mitral flow (E, A, E/A ratio, and deceleration time, A-wave duration, isovolumic relaxation time-IVRT), mitral annular velocity by tissue Doppler imaging (e’ and E/e’), and pulmonary vein flow (S and D duration and velocity, S/D, as well as Ar and Ar-A durations). Also included are tricuspid regurgitation velocity (TRV), left atrial volume index (LAVI), and left ventricular mass index (LVMI). These parameters are integrated into diagnostic algorithms. BSE takes GLS as routine parameter, whereas in ASE this parameter has not been included. ASE considers LARS as a primary parameter, which has been considered a routine parameter by BSE. Supplementary (ASE) or non-routine (BSE) parameters—such as the L-wave, changes in mitral in-flow pattern with Valsalva maneuver, PR early diastolic velocity, diastolic mitral regurgitation, and propagation velocity (Vp), E/Vp, TE-e’, and IVRT/ TE-e’, are considered in indeterminate cases or in special populations. Challenges and the Role of Strain Analysis Analysis of DF using these parameters can leave a significant number of patients unclassifiable or indeterminate (10-30% in various studies). Recently, strain analysis of both the left ventricle and left atrium has shown promise in addressing this gap. Due to its robustness, angle-independence, and ease of use, strain can be applied rapidly both online and offline. Incorporating strain parameters into earlier versions of the ASE guidelines in various clinical studies has significantly reduced the number of patients whose DF cannot be determined. Singh et al. demonstrated that grading LV diastolic function solely on LARS is effective, as this parameter exhibits a continuous decline with worsening DDF. Moreover, LARS cut-offs are clearly distinct across the three DDF groups [5]. Wang et al. found that, among 823 patients, 14% were initially indeterminate for DDF; applying LA strain to this group allowed further classification, aligning outcome risks with those predicted by the original 2016 guidelines [6]. Sameui first compared the 2009 and 2016 guidelines (ASE) for patient reclassification into DDF groups and then assessed the impact of adding strain to the 2016 guideline, showing a reclassification of 41% of patients between the two guidelines and an additional 4.1% with the inclusion of LA strain (LARS < 23%) [7]. Venkateshvaran A et al added LARS to ASE 2016 guidelines in various models and compared them with invasive data to determine pulmonary capillary wedge pressure (PCWP). They found “the ASE/EACVI algorithm (89% feasibility, 71% sensitivity, 68% specificity) demonstrated reasonable ability (AUC=0.69) and 68% accuracy to identify elevated LVFP. LARS displayed strong ability to identify elevated PCWP (AUC=0.76). Substituting TR peak velocity for LARS in the algorithm (69% sensitivity, 84% specificity) resulted in 91% feasibility, 81% accuracy, and stronger agreement with invasive measurements. Employing LARS as per expert consensus (71% sensitivity, 70% specificity) and adding LASR to conventional parameters (67% sensitivity, 84% specificity) also demonstrated greater feasibility (98% and 90%, respectively) and overall accuracy (70% and 80%, respectively) to estimate elevated PCWP” [8]. These findings provide strong evidence for including strain parameters in DF assessment. Comparison of BSE and ASE Approaches The BSE guidelines classify subjects based on several criteria. Initially, subjects are identified as having either normal or reduced function, using parameters such as ejection fraction (EF >50%), global longitudinal strain (GLS 14), and presence of myocardial disease. In normal subjects, E/e’ (> 14), left atrial volume index (LAVI >34 cc), and tricuspid regurgitation velocity (TRV >2.8 m/s) are assessed. Diastolic function (DF) status is determined into three classes: If majority of parameters are normal: Normal DF with normal LVFP if e’ (age-specific) is within normal range. Impaired DF with normal LVFP if e’ is less than normal. If majority of parameters are abnormal: Diastolic dysfunction with increased LVFP if majority of parameters are abnormal. In situations where only two parameters are available in this step with incongruent results, strain measures such as left atrial reservoir strain (LARS) and left atrial conduit strain (LACS) are utilized, dividing subjects into three groups: Normal DF with normal LVFP: LARS >30 or LACS >14% if e’ (age-specific) is within normal limits. Diastolic dysfunction with normal LVFP: LARS >30 or LACS >14% and e’ (age-specific) is reduced. Diastolic Dysfunction (DDF) with increased LVFP: LARS <18. Intermediate Group: LARS 18-30; consider two additional parameters (L-wave >20 cm/s and Ar-A duration >30 msec). Presence of any positive parameter confirms DDF with increased LVFP otherwise LVFP would be normal and presence/absence of DF is decided by e’ value. For patients with reduced left ventricular (LV) function, the same approach is followed. In these cases, the presence of DDF is already confirmed, and only the status of left ventricular filling pressure (LVFP) is assessed. If majority of parameters are in normal range LVFP is normal otherwise, diagnosed as increased. If only two parameters with incongruent results are available in the second step, strain measures are applied, classifying patients as follows: Normal Filling Pressure: LARS >24 or LACS > 14%. Increased Filling Pressure: LARS <18 or LACS <8. Intermediate Group: LARS 18-24; further assessment using L-wave (> 20 cm/s), Ar-A (> 30 ms), E wave deceleration time (DTE < 150 ms), and S/D (<1). The presence of any positive parameter indicates increased filling pressure. On the other hand, ASE guidelines treat all subjects as a single group, evaluating DF using two algorithms. First, the presence of DDF is confirmed, then left atrial mean pressure is estimated (normal or increased), and finally DDF is graded using the E/A ratio. LARS is included in the first algorithm along with three other parameters (E/A, E/e’, LAVI). The presence of two out of these four parameters, or any one along with reduced e’, indicates DDF. Increased left ventricular mass index serves as a supplementary parameter. LARS is also included in the second algorithm, with LAVI, S/D, and IVRT, to determine increased left atrial mean pressure. Thus, it is quite clear that BSE uses LV strain for classification of subjects in the first step as normal or reduced function and in indeterminate cases rely heavily on LA strain parameters (LARS and LACS) for further diagnoses of DDF. On the other hand, ASE uses LARS only as a parameter in their two algorithms and have not considered LV strain or LACS in their algorithms. Notably, BSE does not grade DDF, whereas ASE provides grading (by utilizing E/A). Special Populations and Advanced Measures Both guidelines incorporate LARS in evaluating diastolic function in special populations such as those with atrial fibrillation and pulmonary hypertension. The left atrial stiffness index, calculated by dividing E/e’ by LARS, is recommended by ASE for