Over the last decades, important efforts have been made to miniaturise echocardiographic machines without losing too much accuracy. The first step was to move from big cumbersome machines to echocardiographic laptops. Recently, hand-held ultrasound machines have been developed (see Figure 1). This evolution should facilitate point-of-care cardiac ultrasound – that is, ultrasonography performed and interpreted by the clinician at the patient’s bedside. This phenomenon of miniaturisation is not unique to cardiology but is seen in most disciplines of medicine.1 The use of hand-held ultrasound machines will continue to diffuse across all medical specialities.
Recent data underline the potential utility of pocket-size echocardiography (PSE) as a fast anatomical screening tool alongside clinical examination (which includes interrogating the patient and using a stethoscope) in the outpatient clinic and at the patient’s bedside in hospital (except in the accident and emergency [A&E] department).2–8
Data on the use of PSE in the A&E department is lacking. However, using the data from the non-emergency hospital and outpatient settings allows us to define the potential strengths, as well as the important issues that will need to be resolved, of PSE in the specific setting of the A&E department.
The most important questions the cardiology community will need to answer in the near future are:2,9
- what are the most appropriate clinical settings where PSE can be introduced and result in improved patient care?
- who should perform PSE? (this question will open the discussion on adequate training and assessment of the necessary skills); and
- what will be the exact level of reimbursement of PSE compared with a complete echocardiographic examination?
Pocket-size Echocardiography in two Non-urgent Settings
Recent sudies have underlined the appropriateness of the use of PSE in the outpatient clinic and in the non-urgent hospital setting.
PSE gives additional diagnostic information on top of clinical examination with a stethoscope.2–8 Galderisi et al. found that, compared with physical examination use of the PSE on top of the physical examination lead to the suplementary diagnosis of increased wall thickenes of the left ventricle in 12% of the patients, decreased left-ventricular ejection fraction (LVEF) (+10.2 %), pericardial effusion (+8.2 %), left atrial dilatation (+7.6 %), valve calcifications (+6.9 %), dilatation of the inferior vena cava (+4.6 %), pleural effusion (+3 %), left-ventricular dilatation (+2.6 %), comet tails (+2.6 %) andright-ventricular dilatation (+1.6 %).4 PSE has been shown to give accurate measurements of LVEF, an accurate estimate of pericardial effusion and cavity dimensions, and a rough estimate by colour Doppler of the presence of regurgitant and stenotic valvular disease.4–5
PSE used in these two non-urgent settings results in less inappropriate referrals to the busy echocardiography laboratory for unnecessary routine examinations and, to a lesser extent, in more appropriate referrals. Cardim et al. showed that physical examination only and physical examination plus PSE both came to the same conclusion regarding referral to the echocardiography laboratory in 19.6 % of patients; however, physical examination plus PSE resulted in the additional referral of another 14.3 % of patients, and found that a further 30.7 % of patients had been inadequately referred by physical examination only.6 The same authors found that the increase in the duration of the consultation using PSE on top of the stethoscope was only 180±86 seconds (range 45–420 seconds).6
Galderisi et al. and Liebo et al. clearly demonstrated that the results obtained with PSE were significantly better when it was used by experienced practitioners compared with trainees.4,8 Galderisi et al. found a sensitivity and specificity of the PSE device, compared to the highendechocardiographic machine as the reference technique are 97 % and 84 % for experts and 87 % and 72 % for trainees.4
Important Issues to Resolve in the Setting of the Accident and Emergency Department
Education and Training
Most of the studies showing the excellent accuracy of PSE, compared with the reference high-end digital ultrasound systems, used trained ultrasonographers or cardiologists to analyse and store the image data.3–8 Their results cannot be extrapolated to a clinical scenario in which a PSE device would be used by a trainee. Even with high-end digital echocardiographic machines, the accuracy of echocardiographic data is operator-dependent, and this will only be amplified with PSE.4,8 With PSE, the adequate storage of ultrasound pictures and loops is crucial, especially if the focus of the use of the PSE device is the evaluation of left-ventricular function and cavity size. Cardiac ultrasound specialists will unanimously confirm that the adequate interpretation of regional wall motion abnormalities, integrating wall motion and thickening, is one of the most difficult tasks in cardiac ultrasound, requiring the highest expertise and perfect endocardial border determination (see Figure 2).
If PSE is to be introduced for point-of-care cardiac ultrasound in the A&E department, education and training will be of the utmost importance, since it will be less experienced physicians who will perform the examination and interpret the findings. Introducing a PSE device in the A&E department in the hands of non-experts could also raise medico-legal issues. The A&E department is a stressful environment, with critically ill patients, time constraints, technical acquisition problems and limited time for consulting with other staff members. Critical decisions have to be made and medical errors are likely to occur.9 Any change in strategy that may potentially increase the risk of errors must therefore be avoided.
PSE is an amazing piece of technology, but it still has shortcomings. The resolution of the images is pretty good, but the screen of course is small, making the detection of small abnormalities difficult. The accurate detection of small abnormalities, such as vegetations in endocarditis, is crucial in clinical diagnosis, especially in the emergency setting. The examination performed with a PSE device is not a complete echocardiographic examination. Major tools such as pulsed wave (PW) Doppler, continuous wave (CW) Doppler and tissue Doppler imaging are still lacking. Considering its shortcomings, PSE can only provide semi-quantitative information of the anatomy and haemodynamics of the heart. One can visualise aortic valve sclerosis, but cannot diagnose severe aortic valve stenosis with absolute certainty. One can use colour Doppler regurgitant flow jets to estimate valvular regurgitations, but cannot accurately quantify clinically important regurgitations, since no quantitative Doppler tools are available. Echocardiography laptops can be integrated in the hospital’s electronical system, and examinations performed in the A&E department can therefore be followed and supervised by an expert at the central echocardiography laboratory. This not yet possible with a PSE device.
Strategic Distribution of Cardiac Ultrasound Examinations in Emergency Settings
The same discussion about the risks and benefits of introducing a new imaging device in cardiac ultrasound practice took place when the echocardiography portable computer (echo-PC) was introduced. Mobile portable computer ultrasound systems are now widely used in A&E departments. The broader question is: does everybody need an ultrasound stethoscope in their pocket, in A&E departments where ultrasound systems with better spatial resolution and better digital storage and transmission capacities, as well as fully equipped platforms with all Doppler modalities included, are already available? Of course, an exception to this is the ambulance, where introducing PSE would provide a new and unique cardiac imaging modality.
Future Improvements and Potential Clinical Impact
PSE will never compete with high-end echocardiographic machines, and this should not be the goal. Due to the small screen, the imaging of very small abnormalities will always be more difficult, leading to reduced diagnostic accuracy. Because of the inherent time constraints of a point-of-care cardiac ultrasound examination, an extended physical examination using PSE does not equate with a comprehensive evaluation of the heart’s anatomy and haemodynamics. However, future technological improvements could enhance the performance of PSE.
The optimisation of the colour Doppler applications (frame rate, filter settings, etc.) as well as the introduction of PW and CW Doppler and of advanced quantification tools would increase the diagnostic possibilities of PSE, shifting its current semi-quantitative information status towards an exact quantitative ultrasound mini-platform. Using PSE for point-of-care cardiac ultrasound requires adequate digital storage and rapid image control by the echocardiography laboratory, in order to ensure quality and avoid potential diagnostic errors in the A&E department.
PSE is already widely available and definitely has a place in the outpatient clinic and in the non-urgent hospital setting. In these settings, if non-specialists in cardiac ultrasound are using PSE, quality control and training and education are mandatory. Of course, PSE does not replace an echocardiogram and has no place in the hospital’s echocardiography laboratory. In the A&E department, there is no room for error. Education, training and quality control are even more crucial here. The clinical utility of a liberal distribution of PSE in the A&E department, where echo-PC devices are widely available, seems at least debatable. The ambulance is perhaps a better place for PSE in the wider emergency setting.