Portable echocardiography

As the number of patients presenting with acute conditions to emergency and intensive care units continues to grow traditional ward based models of care may no longer be adequate. Reorganisation of critical care services is a government priority, encapsulating the paradigm that rapid assessment and treatment of modifiable life threatening conditions is required regardless of the location of the patient.¹ Failures of all organ systems are potentially life threatening, but arguably the most catastrophic is failure of the cardiovascular system. Quick deployment of diagnostic aids to the bedside and identifying patients at risk therefore assume great importance.

Advances in microprocessor technology have permitted cardiac ultrasound to evolve from the crude 1953 oscilloscopes of Edler and Hertz through powerful but essentially immobile echocardiographs to portable battery powered devices that even incorporate the capacity for Doppler interrogation. This portability brings with it the opportunity for widespread use at the bedside with the potential to afford unprecedented benefit in immediate diagnosis. Such developments pose two major questions. What are the clinical applications of these portable machines, and what training should potential operators receive?

Clinical studies show that portable echocardiography can be used to initiate and modify treatment, particularly in patients with cardiac conditions. Investigators have shown that basic assessment of ventricular function, measurement of the dimensions of the ventricular chamber, and identification of structural lesions including valvular regurgitation or stenosis and pericardial effusions is possible in all patients except those least amenable to echocardiography. The sensitivity of portable echocardiography for the detection of cardiac abnormalities is higher than that of clinical examination and reaches 70-90% compared with conventional echocardiography.^2-5 Although portable echocardiography is not without notable limitations—particularly with relation to spectral Doppler, harmonic imaging, probe footprint size, resolution, and storage facilities—the procedure nevertheless seems adequate in trained hands, for limited studies where the context of the study and the clinical questions posed are clearly predefined.

As a result of limited studies several leading echocardiologists have concluded that novice non-cardiologists, with as little as three hours of training, are capable of making relatively reliable assessments by portable echocardiography of ventricular function and other life threatening conditions, including pericardial effusion.^6-9 In contrast to this general success of portable echocardiography, a study based in intensive care units indicated that up to 31% of important findings were missed, probably due to suboptimal imaging.¹⁰ Although the technology has advanced since this study, on the basis of our own experience we remain cautious. We agree with current recommendations that portable echocardiography should not be used to influence the management of patients by inexperienced clinicians.¹¹

Advocates of portable echocardiography have proposed that this technology should be incorporated into medical students' curriculums and ultimately disseminated generally. However, in the absence of definitive evidence from desperately needed field studies a pragmatic approach should be adopted, balancing the limited training needs of portable echocardiography to be performed acutely at the point of care with the comprehensive approach advocated for cardiologists.¹¹

Although most doctors have a fairly circumscribed knowledge of electrocardiography and radiology, they use these tools to address specific triage questions to guide urgent and powerful treatments (for example, thrombolysis for acute myocardial infarction) but ultimately defer to specialists for ongoing management. Training in portable echocardiography should not be aimed to produce clinicians capable of performing complete studies any more than we train doctors to perform or report computed tomography scans. Instead, by restricting operators to a minimum familiarity with acute illness, a specific training programme and competency criterion with national guidelines should be developed to educate doctors and allied healthcare professionals to integrate focused portable echocardiography into their existing clinical and resuscitation protocols. By using a limited number of specific scenarios applicable to the acute care setting a didactic syllabus (with a standardised reporting algorithm) and focused “rule in, rule out” questions, the simplified nature of these studies could be emphasised (potentially reducing false positives and negatives). Equally importantly, the limitations of the method should be taught, including the absolute requirement for images to be acquired and stored for urgent consultation with an expert where doubt remains.¹² Portable echocardiography should be used not to facilitate discharge but to trigger timely referral to a specialist and conventional detailed departmental echocardiography.

Ultimately if emergency doctors are educated under the auspices of this targeted tuition they will acquire a realistic appreciation of the role of portable echocardiography in acute care and the importance of continuous audit and assessment, and this will represent a major advance in the care for patients with acute conditions. Acquiring the requisite skills (comparable to the performance of a minimum of 150 studies) will require ongoing personal practice supported by feedback from local specialists and experienced seniors informally or as part of formal echocardiography rounds. Without this mentorship the intended dissemination of this technology will not be practicable and an opportunity will be missed. With it diagnostic abilities will be enhanced, facilitating rapid initiation of treatment and improving the outcome for patients.