Emergency physician use of tissue Doppler bedside echocardiography in detecting diastolic dysfunction: an exploratory study

Introduction This study evaluates the agreement between emergency physician (EP) assessment of diastolic dysfunction (DD) by a simplified approach using average peak mitral excursion velocity (eʹA) and an independent cardiologist’s diagnosis of DD by estimating left atrial (LA) pressure using American Society of Echocardiography (ASE) guidelines. Methods This was a secondary analysis of 48 limited bedside echocardiograms (LBE) performed as a part of a research study of patients presenting to the Emergency Department (ED) with elevated blood pressure but without decompensated heart failure. EPs diagnosed DD based on eʹA < 9 cm/s alone. A blinded board-certified cardiologist reviewed LBEs to estimate LA filling pressures following ASE guidelines. An unweighted kappa measure was calculated to determine agreement between EP and cardiologist. Results Six LBEs were deemed indeterminate by the cardiologist and excluded from the analysis. Agreement was reached in 41 out of 48 cases (85.4%). The unweighted kappa coefficient was 0.74 (95% CI 0.57–0.92). EPs identified 18 out of 20 LBEs diagnosed with diastolic dysfunction by the cardiologist. Conclusion There is a good agreement between (eʹA) by EP and cardiologist interpretation of LBEs. Future studies should investigate this simplified approach as a one-step method of screening for LV diastolic dysfunction in the ED.


Introduction
Diastolic dysfunction (DD) is an alteration of relaxation, filling, and/or distensibility of the left ventricle [1]. DD can lead to diastolic heart failure and increases the risk of readmission rates and in-hospital mortality [2]. The increased prevalence of DD has led to growing interest in early detection in acute care settings [3,4].
The American Society of Echocardiography (ASE) guidelines outline a detailed algorithm for the diagnosis of DD which includes (1) spectral pulsed wave Doppler of transmitral inflow; (2) pulsed wave Doppler profile of pulmonary venous flow; (3) mitral annulus downward velocity measurements (eʹ) using tissue Doppler imaging (TDI) at the septum (eʹ S ) and lateral wall (eʹ L ); and (4) left atrial (LA) volumes [5]. Obtaining these multiple measurements may be time-consuming and difficult for the average EP.
Average peak mitral annulus velocity by TDI (eʹ A = [eʹ S + eʹ L ]/2) has been described as an acceptable single-step method for assessing LV relaxation, using eʹ A < 9 cm/s as a threshold [6][7][8][9]. TDI measurements can be obtained in 30 s with nearly 100% success rate, even with poor echocardiographic windows [10,11]. This simplified approach may be more suitable for use by EPs with limited experience in echocardiography.
The purpose of this study was to ascertain inter-rater agreement in DD determination between eʹ A < 9 cm/s measured by EPs and cardiologist interpretation of LBEs following the ASE guidelines.

Study design
This was a secondary data set analysis of LBEs completed as part of a prospective, cross-sectional with longitudinal Open Access *Correspondence: mdelrios@uic.edu 1 Department of Emergency Medicine, University of Illinois at Chicago, Chicago, Illinois, USA Full list of author information is available at the end of the article follow-up study (details provided elsewhere) of patients presenting to the emergency department (ED) with asymptomatic elevated blood pressure [12,13].

Study protocol and measurements
LBEs were performed based on research staff availability by EPs (two emergency ultrasound fellowship-trained faculties and one emergency ultrasound fellow) who had performed at least 100 LBEs through routine clinical care and who underwent training and demonstrated proficiency in diastology with a board-certified cardiologist. A sonosite M-Turbo ultrasound system equipped with a harmonic 4.0-MHz variable-frequency phased-array transducer was used to obtain images and measurements. Studies were digitally archived for cardiologist review.
EPs utilized electrocardiogram (EKG) rhythm strips to time diastole. EPs determined eʹ A by averaging eʹ S and eʹ L measurements. EPs considered an eʹ A < 9 cm/s as evidence of DD without adjustment for age or other risk factors. A board-certified cardiologist with an ASE level III echocardiography certification independently reviewed LBE images while blinded to EP interpretation. The cardiologist rated the images in accordance to the 2009 ASE guidelines [8] and upon reviewing digital recordings of the following: parasternal long view for determination of LV wall thickness, apical four-chamber view for estimation of LA size, E and A measurements, eʹ S and eʹ L , E/eʹ ratios to assess LA pressure, estimation of LA size, and the EKG rhythm strip (see Table 1 for comparison of data interpretation).

Data analysis
EPs and cardiologist indicated DD present, DD absent, or indeterminate for each LBE study. A 3 × 3 contingency table provided a summary of agreement. Inter-rater reliability between EPs and the cardiologist was determined using an unweighted kappa with 95% confidence interval (CI) coefficient using Stata Release 15, StataCorp.

Results
Forty-eight studies were submitted to the cardiologist for review. Cardiologist and EP agreement are summarized in Table 2. Agreement was reached in 41 out of 48 cases (85.4%). The unweighted kappa coefficient was 0.74 (95% CI 0.57-0.92).

Discussion
Diastolic dysfunction is prevalent and delays in diagnosis can lead to increased morbidity and mortality. EPs with focused training in diastology may identify diastolic dysfunction with high sensitivity compared to a cardiologist trained in echocardiography. Previous studies have demonstrated that EPs can identify DD with high sensitivity, but either did not include TDI as part of their assessment [14] or reported only moderate agreement with cardiologist interpretation [4]. One study showed that EPs who met minimum requirements for LBEs based on American College of Emergency Physicians guidelines demonstrated high inter-rater agreement in the assessment of DD using primarily TDI, but failed to compare EP to a cardiologist interpretation [15]. Our study addresses the limitations of previous evidence by demonstrating that by  following a more simplified approach using eʹ A alone, EPs can identify DD with high level of agreement compared to a cardiologist following the ASE guidelines.

Limitations
Our sample size and convenience sampling may have introduced selection bias thus preventing a definitive correlation between eʹ A and DD. EPs did not screen for regional wall motion abnormalities. Because wall motion abnormalities of the left ventricular basal segments can influence mitral annulus TDI diastolic velocities, this may have led to an overestimation of DD prevalence. Moreover, comparison was limited to cardiologist interpretation of LBE images, which may not be representative of typical exams obtained by a technician or specialist. A larger, multi-center study comparing EP assessment of eʹ A against performance of a comprehensive echocardiogram can help establish external validity.

Conclusions
This study highlights a promising simplified approach for identifying DD by EPs. Relying on eʹ A alone achieved good agreement for determination of DD compared to LBE interpretation by cardiologist. Future studies should further investigate this simplified approach as a onestep method of screening for LV DD in the emergency department.