When echo gets in the way: physiological factors affecting Doppler data

Transthoracic echocardiography (TTE) is widely used as a pre-operative screening tool. It can provide extensive information about cardiac function and underlying pathology, which could influence decisions regarding surgery. This patient was referred for TTE as part of the pre-op screening, as he had a biological prosthetic aortic valve. This was a rare case where misleading TTE measurements inadvertently led to the patient being referred for transcatheter aortic valve replacement (TAVR), which delayed non-cardiac surgery. Routine pre-op TTE in a district hospital showed severely increased gradients compared to the previous year, so the patient was referred to a tertiary centre for TAVR. However peri-operative trans-oesophageal echocardiography (TOE) showed lower gradients and satisfactory valve area. The cause of high gradients at the time of pre-op screening was retrospectively attributed to profound anaemia present at the time. When the anaemia was corrected, the prosthetic valve gradients reduced to levels similar to the previous year. This case reiterates the fact that Echocardiographers should be familiar with haemodynamic factors that could affect the validity of Doppler measurements that use Bernoulli's equation and the continuity principle. This report also looks at how echocardiographers can mitigate the effects of non-valvar factors.