Cardiologists caution against limited echocardiogram use in outpatient settings

Tuesday, 26 Oct 2021

Limited echocardiograms have gained favour during the COVID pandemic, but the practice isn’t necessarily sufficient to detect structural heart disease in outpatient settings or for unselected indications, Australian cardiologists say.

A study reviewing the efficacy of the “Quick Six”, a set of six images anecdotally considered the most important screening views for determining cardiac structure and function, found the tool only had a sensitivity, specificity and accuracy of 71.2%, 57.1% and 65.4%, respectively.

The images, taken from the parasternal long axis view with and without colour Doppler over the aortic and mitral valves, and apical four-chamber view with and without Doppler over the mitral and tricuspid valves of 203 adult outpatients, were reviewed by echocardiography-specialised and non-specialised cardiologists and sonographers.

The three practitioner groups had similar overall accuracy with the tool and there was no difference in ECG-specialised and non-specialised cardiologists’ sensitivity or specificity, lead author and Flinders Medical Centre cardiologist Dr Katherine Tiver and her team wrote in Heart, Lung and Circulation.

Meanwhile, sonographers had higher sensitivity but less specificity than the other groups.

Limited echocardiography has been turning heads recently as an attractive, lower-cost alternative to standard ECG services, given the increasing demand for echocardiography and potential to limit COVID-19 transmission risk between patients and sonographers.

“Between 2012 and 2017, the number of echocardiography services provided in Australia increased by 7% on average each year,” Dr Tiver and her team wrote.

Yet a previous study showed a fair proportion of ECG referrals in Australian regional and tertiary hospitals were inappropriate, at 20% and 10%, respectively.

Limited testing could help reduce this burden by ensuring that only patients with abnormalities undergo full ECGs, the authors suggested.

It could also cut sonographer-patient exposure time to better protect cardiac sonographers who are at “uniquely high risk for [COVID-19] viral transmission, as they are within the droplet zone for > 20 minutes in order to perform a standard echocardiogram”, they wrote.

While focussed cardiac ultrasound examination is used to screen for “key life-threatening pathologies” in emergencies, left ventricular function-focussed transthoracic echocardiogram (LV-TTE) can be used where left ventricular systolic function is the indication for ECG and Medicare now funds limited studies, such as targeted reassessment of pericardial effusion, there is currently “no established general screening echocardiogram protocol in the literature for all indications”.

Dr Tiver and her team hoped the “Quick Six” could help fill this gap, given the included images perceived importance.

“In its current form, [the proposed six view ECG study] is not an adequate screening tool for the initial assessment of structural heart disease for unselected indications, with an overall sensitivity of 71% [when performed an interpreted by experienced personnel],” they wrote.

“Caution is especially recommended in extrapolating its use to non-specialised settings.”

“Further work is needed to refine the modality to establish safety, and to establish real world efficacy,” they concluded.

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