A cornerstone of echocardiography is to ensure that normal reference intervals are available against which individual patients can be compared. Historical reference intervals have often been derived from studies or echo databases that included relatively small numbers of patients. Recent years have seen the publication of large, international, prospectively recruited studies from which the British Society of Echocardiography has now derived updated, robust reference intervals for use in echocardiographic practice within the UK.
In some circumstances, the Society has chosen to deviate from the combined European and American guidance. Principally, the Society wanted to ensure that reference intervals were derived from the most contemporaneous and prospectively acquired data; that reference intervals were derived from evidence that best applies to the British population; and finally that echo guidance and cut-offs reflect UK practice.
This document suggests a number of changes to currently used reference intervals, and in some circumstances this may lead to an individual who was previously labeled as ‘abnormal’ now being seen as ‘normal’ (and vice versa). It is recommended that the changes suggested within the guideline should be discussed with sonographers, cardiologists and general clinicians when integrating the new reference intervals into everyday practice to ensure a smooth transition in the care of patients. The rationale for all suggested changes to practice are discussed in the guideline document.
The key differences in the updated guidance are:
- Changes in the reference intervals for LV ejection fraction:
- A new ‘borderline low LV ejection fraction’ group of 50-54%
- Patients with an LV ejection fraction of 36-49% are defined as ‘impaired LV ejection fraction’. The Society no longer advocates division into ‘mild’ or ‘moderate’ LV impairment
- Changes in the assessment of LA volume:
- Measured using the Biplane Simpson’s method and indexed to BSA
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A new ‘borderline LA volume’ range of 34-38ml/m2
- Changes in the echocardiographic assessment of the right heart:
- Separate reference intervals for males and females
- New upper reference limits for RV outflow tract dimensions, RV body, and the right atrium
- Introduction of indexed values to allow for body habitus
- Changes in the assessment of the aortic root:
- Aortic dimensions now indexed for height and not BSA
- Should be obtained in end-diastole using inner-edge to inner-edge method
- Whereas previously there were different reference ranges for aortic dimensions according to age, the Society now produces age-independent ranges for men and women
Read the guideline
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The new guideline will not affect the March 2020 written exam. Find out what the changes mean for you.