Diagnosis of diastolic dysfunction in the emergency department: really at reach for minimally trained sonologists? A call for a wise approach to heart failure with preserved ejection fraction diagnosis in the ER

HFpEF demands a multi-parametric echocardiographic assessment. In this retrospective analysis of data from a previous observational study on stable hypertensive patients, Del Rios et al. considered a single echocardiographic variable in order to assess concordance of EPs and cardiologists in the diagnosis of diastolic dysfunction: medial/lateral averaged mitral annular tissue doppler (TDI) protodiastolic velocity. Other authors have recently investigated the possibility of diagnosing HFpEF by EPs receiving a dedicated training in cardiac bedside ultrasound [7], or suggested an approach to the issue in the form of concept paper [8]. Others have proposed a simplified approach to diastolic dysfunction diagnosis in specific critical care populations [9]. All these authors, consistently with the known complexity of this diagnosis and in line with current echocardiographic recommendations, have tackled the issue by combining several ultrasound-derived indices. More recently Johansen et al. have demonstrated in a community-based study that a combination of three relatively easy to obtain parameters (e’, E/e’ and indexed left atrial volume) was able to stratify the population for increasing risk of cardiac major adverse events [10]. The last Recommendations for the Evaluation of Left Ventricular Diastolic Function by Echocardiography are in fact explicit in warning that none of the echocardiographic indices should be used in isolation, as some measurements may fall in the normal range despite the presence of diastolic dysfunction due to the several hemodynamic factors that may affect each signal [11].

TDI acquisition can be technically challenging. Althought E/E’ is key to assess diastolic dysfunction with good reproducibility and reliability, a series of technical issues can affect the accurate measurement of mitral annular TDI. Protodiastolic mitral annular velocity (TDI E’), the cornerstone of diastolic dysfunction diagnosis, reflects mitral annulus motion that precedes filling; it correlates well with invasive measures of the time constant of myocardial relaxation tau although it is not entirely governed by relaxation [12]. There are a number of pathological conditions that impair myocardial relaxation and restoration forces with increased lengthening load (LA pressure), resulting in reduced and delayed longitudinal motion and E’ velocity. TDI E’ measurement mandates optimal 2D images to be adequately sampled, being thus affected by gain and filter adjustment, sufficient visualization of mitral annulus, absence of mitral annulus severe calcifications/prosthesis, correct angle (< 20°) of insolation, and adjustment according to the plane of cardiac motion [13, 14]. All these technicalities, with their inherent operator-dependency and learning curve, place this kind of echocardiographic assessment beyond the reach of a limited ultrasound training.

TDI interpretation conceals several pitfalls that should not be neglected. There are a variety of pathological conditions where TDI E’ could be normal in presence of altered cardiac dynamics: constrictive physiology [15], patients with moderate to severe primary MR and normal LV relaxation due to increased flow across the regurgitant valve [16], discordance between lateral and septal E’ in advanced systolic heart failure [17], atrial fibrillation, ventricular dys-synchrony or, moreover, regional wall motion abnormalities [13]. None of these conditions are addressed in simplified approaches, such as the one proposed by Del Rios et al.

Limited bedside ultrasound diagnostic tests are accurate in specific patient populations, and only when interpreted in tight conjunction with clinical data. One of the basic assumptions of Focused Cardiac UltraSound (FOCUS) (and point of care ultrasound in general) is that the limited ultrasound exam is sufficiently informative only when it is part of a clinical-ultrasound integrated approach [18, 19], not as standalone diagnostic test (e.g. only in shocked patients the absence of severe right ventricular failure allows to rule out pulmonary embolism as a cause). In other words, the limitations of the simplified approach are “compensated” by the magnitude of the ultrasound abnormality (gross finding, easier to detect) and by the specific clinical picture (high pre-test probability). In this respect, a cohort of patients without symptoms of congestive heart failure does not seem to be particularly suitable to test the (even preliminary) hypothesis that diastolic dysfunction may fall within the purview of FoCUS.

Core of HFpEF diagnosis is the demonstration of elevated left atrial pressures. Patients may exhibit diastolic dysfunction (as detected by a reduced TDI mitral annular E’) unrelated to their respiratory symptoms, i.e. without having high left atrial pressures and congestive HF. Rather than diastolic dysfunction per se, what matters in the approach to patients with suspected acute heart failure is the finding of positive echocardiographic indices of increased left atrial pressures [13]. These should be indices sufficiently validated in decompensated/critical patients, (such as E/E’, pulmonary veins systolic fraction, E/A, DTE), and are usually assessed with a semi-quantitative approach [20].