How do I assess left ventricular diastolic function?

Introduction The assessment of left ventricular (LV) diastolic function is frequently required in patients admitted to intensive care units (ICUs). LV diastolic dysfunction refers to abnormal (i.e., prolonged) relaxation associated with an augmented contribution of left atrial contraction to LV filling (sinus rhythm) and a progressive increase in filling pressure.1 Clinical evaluation relies primarily on transthoracic echocardiography in patients presenting with acute respiratory failure to identify pulmonary venous congestion or assess tolerance to fluid resuscitation.2 This assessment is based on two-dimensional imaging, pulse-wave mitral Doppler imaging, and tissue Doppler imaging applied to both the septal and lateral aspects of the mitral annulus. Although critical care echocardiography (CCE) uses multiple views and parameters to hemodynamically assess ICU patients, the sole apical four-chamber view provides the information required to characterize LV diastolic function and semi-quantitatively assess the associated LV filling pressure.1 Herein, a three-step diagnostic workup is proposed. First step: two-dimensional examination In the apical four-chamber view, two-dimensional imaging may depict cardiomyopathy known to be associated with LV diastolic dysfunction (e.g., ischemic, hypertrophic, or infiltrative cardiomyopathy) and allow the assessment of its severity (LV remodeling, ejection fraction). Dilatation of the left atrium (measurement of the left atrial volume) and constant bulging of the interatrial septum towards the right atrium throughout the cardiac and respiratory cycles reflect chronically elevated LV filling pressures (Figure 1). When present, these findings strongly suggest underlying LV diastolic dysfunction, with potential pulmonary venous congestion. Alternatively, they can result from severe mitral valve disease (e.g., mitral regurgitation), volume overload (e.g., anuric patients), or chronic atrial fibrillation. When these findings are absent, elevated LV filling pressure cannot be confidently excluded. Accordingly, LV diastolic function and the associated filling pressure must be systematically assessed whenever the clinical presentation suggests hydrostatic pulmonary edema.1Figure 1.: Illustration of the main cardiopathies known to be associated with left ventricular diastolic dysfunction and associated elevated filling pressures in the apical four-chamber view. Left atrial dilatation reflects chronically elevated filling pressures. Of note, left ventricular ejection fraction can be reduced or preserved. LA, left atrium; LV, left ventricle; LVEF, left ventricular ejection fraction; RA, right atrium; RV, right ventricle.Second step: Doppler examination This examination is conducted in the apical four-chamber view (Figure 2). The pulsed-wave mitral Doppler profile is influenced by numerous parameters unrelated to LV relaxation and filling pressure (Table 1). Nevertheless, an apparently normal profile or restrictive profile in conjunction with a cardiomyopathy known to be associated with LV diastolic dysfunction, suggests an underlying elevated filling pressure.1 The E-wave maximal velocity and deceleration time are the two main parameters of interest that remain valid in patients without sinus rhythm (Table 1). To further assess LV relaxation and filling pressure, tissue Doppler imaging of the mitral annulus must be used to measure E′ maximal velocity and average E/E′ (Table 1). These Doppler parameters are reproducible but may rapidly change according to the loading conditions.3 The practical time sequence of data acquisition is detailed in Figure 2. The additional value of tissue Doppler imaging of the mitral ring is particularly relevant in patients with underlying severe diastolic dysfunction, irrespective of LV systolic function (Figure 3). Importantly, the measurement of left atrial volume has not been validated using transesophageal echocardiography, and this approach tends to slightly underestimate E′ maximal velocity.4 An advanced level in CCE is required to assess LV diastolic function and filling pressure.5 In experienced hands, the reproducibility of Doppler velocity measurement is excellent (≤5%).3 In the near future, artificial intelligence incorporated into ultrasound systems will undoubtedly guide operators in the acquisition and interpretation of relevant data for LV diastolic function and filling pressure assessments.6 Finally, the apical four-chamber view is the reference imaging window used to assess both the size and systolic function of the right ventricle, which may be impaired in the presence of long-standing postcapillary pulmonary hypertension. Table 1 - Characteristics and limitations of Doppler parameters used to assess left ventricular diastolic function and filling pressure. Information Limitation Feasibility & reproducibility Pulse-wave spectral Doppler Maximal E wave velocity (cm/s or m/s) • Net result for LV diastolic properties, loading conditions, age, heart rate, pericardial or ventricular interactions• Remains valid in nonsinus rhythm • Influenced by factors unrelated to LV diastolic function and filling pressure• Peak velocity challenging to identify if tachycardia is present (fused E and A waves) +++ E wave deceleration time (ms) Challenging to accurately measure (tachycardia, double slope of E wave) + A wave (cm/s or m/s) Reflects the contribution of left atrial contraction to LV filling at end-diastole Peak velocity is challenging to identify if tachycardia is present (fused E and A waves) ++ E/A ratio (no unit) Reflects the relative contribution of LV relaxation and atrial contraction to LV filling Influenced by tachycardia and loading conditions +++ Pulse-wave tissue Doppler imaging Maximal E′ wave velocity, lateral mitral annulus (cm/s) Reflects the relaxation of LV longitudinal fibers Not valid for regional wall motion abnormality involving basal segments or mitral annuloplasty +++ Maximal E′ wave velocity, septal mitral annulus (cm/s) Average E/E′ (no unit) Reflects LV filling pressures Combined limitations of each component (E and E′) +++ Continuous-wave Doppler Maximal tricuspid regurgitation velocity (m/s) Reflects systolic right ventricular-to-atrial pressure gradienta • Dependent on imaging quality• Risk of underestimation (suboptimal Doppler beam alignment with flow, low cardiac output)• Does not distinguish between pre- and post-capillary pulmonary hypertension + aWhen adding the value of central venous pressure (or right atrial pressure) in the absence of pulmonary valve stenosis, the systolic pulmonary artery pressure can be estimated using the modified Bernouilli equation.LV indicates left ventricle. Figure 2.: Practical time sequence for the assessment of left ventricular diastolic function and filling pressures in the apical four-chamber view. An adequate apical four-chamber view requires the avoidance of any foreshortening and obtaining a vertical left ventricular cavity along the long axis in the center of the image (Image 1). This two-dimensional view allows visual identification of potential left ventricular remodeling for left-sided valvulopathies, to assess left ventricular ejection fraction, and to measure left atrial volume using the Simpson’s method (Image 2; 116 ml). When tricuspid regurgitation is present, the peak velocity must be measured to assess the systolic pressure gradient between the right cardiac cavities using continuous-wave Doppler (Image 3). Image depth is then reduced to center the two-dimensional image on the left ventricle (Image 4). This allows the precise placement of the pulse-wave Doppler sample at the extremities of the mitral valve leaflets during diastole (mitral valve opening) to obtain the mitral Doppler profile (Image 5). The baseline Doppler velocity (0 line on Y axis) and the velocity scale are optimized to magnify the Doppler envelope and allow accurate measurement, while setting a maximal sweep speed of typically 150 mm/s (Image 6). Tissue Doppler imaging is then started (Image 7). The image field is narrowed to increase the frame rate and obtain optimized tissue Doppler resolution and is focused successively on the lateral and septal aspects of the mitral ring (Image 8). Tissue Doppler tracing is then obtained with a clearly identifiable early diastolic E′ wave, and a late diastolic A′ wave in patients with sinus rhythm. Lateral tissue Doppler velocities are typically higher than septal Doppler velocities (Image 9). The baseline Doppler velocity (0 line on Y axis) and the velocity scale are optimized to magnify the Doppler envelope and allow accurate measurement, while setting a maximal sweep speed of typically 150 mm/s (Image 10). The peak E′ wave velocity is only measured, since it reflects the maximal velocity of left ventricular longitudinal fiber lengthening during early diastole, hence indirectly, left ventricular relaxation. A, late diastolic peak velocity of the mitral Doppler signal during atrial contraction in patients with sinus rhythm; A′, late diastolic peak velocity of tissue Doppler imaging; E, early diastolic peak velocity of the mitral Doppler signal during left ventricular relaxation; E′, early diastolic peak velocity of tissue Doppler imaging at the lateral or septal aspect of the mitral ring; LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle; TR, tricuspid regurgitation assessed using continuous-wave Doppler.Figure 3.: Assessment of left ventricular filling pressure in a patient with a medical history of long-standing hypertension treated with beta-blockers. Two-dimensional assessment revealed concentric left ventricular hypertrophy with a normal ejection fraction of 60%. The pulse-wave mitral Doppler profile depicts a type I pattern with an E/A ratio of 0.7 and a markedly prolonged E wave deceleration time of approximately 400 ms. The peak tissue Doppler E′ velocities are dramatically reduced on both mitral ring aspects (<6 cm/s), denoting severe impairment of left ventricular relaxation. Accordingly, the average E/E′ velocity of 14 is consistent with elevated left ventricular filling pressure, despite a relatively low maximal E wave mitral Doppler velocity of 0.66 m/s.Third step: interpretation From a clinical perspective, identifying LV diastolic dysfunction is of interest through the required determination of its grade (i.e., severity) and, hence, the semiquantitative assessment of associated (elevated) LV filling pressures. Current recommendations for the assessment of LV diastolic function using echocardiography have been established for patients with symptoms of dyspnea or heart failure who have been referred to cardiology departments.7 The background results from epidemiological studies show prognostic information based on the severity (or grade) of LV diastolic dysfunction.7 Accordingly, these guidelines have not been adapted for ICU patients, in whom the prevalence of cardiopathy is lower and LV filling pressures are frequently less elevated.8 Because LV diastolic and systolic properties are tightly linked, current guidelines recommend considering LV systolic dysfunction (i.e., reduced LV ejection fraction) as systematically associated with LV diastolic dysfunction, the grade of which must be determined.7 This definition contributes to the high prevalence of sepsis-induced LV diastolic dysfunction in ICU patients and may partially explain the lack of an association with outcomes in a recent multicenter study, in contrast to previous cohorts of patients with sepsis.9 Left atrial strain appears to be a promising tool that provides additional information on left atrial function in patients with altered LV diastolic properties; however, its clinical use remains limited by its feasibility in the challenging setting of unstable ICU patients.10 Pulmonary artery occlusion pressure can be adequately predicted using CCE for high or low values.8,11–13 The additional clinical value of tissue Doppler imaging appears to be limited in noncardiac patients.8 As the baseline LV diastolic properties in a patient are frequently unknown before ICU admission, the evolution of LV filling pressure is relevant to monitoring using repeated Doppler assessments, such as for the diagnosis of weaning-induced pulmonary edema.14 In ventilated patients with acute respiratory distress syndrome, CCE can confidently rule out a cardiogenic pulmonary edema in depicting normal LV diastolic properties for the patient’s age and nonelevated filling pressure, with a typical average E/E′ of less than 8.1,8 Clinical message LV diastolic dysfunction and associated LV filling pressure are relevant for the assessment of ICU patients when pulmonary venous congestion is clinically suspected. Although CCE does not accurately predict the actual pulmonary occlusion pressure, it allows for a semiquantitative assessment of LV filling pressures. When undetermined, CCE should be repeated to evaluate the effect of treatment on LV filling pressure and interpret this hemodynamic information in light of the clinical course. To optimize the diagnostic value of CCE, examinations should be performed at the time of respiratory compromise to document the associated LV filling profile, which can be rapidly modified (improved) by initial empirical management. Acknowledgments None. Conflict of interest The author declares that they have no conflicts of interest with regard to the content of this report.