[Low sensitivity of the echocardiograph compared with contrast transcranial Doppler in right-to-left shunt]

Abstract

Background: Contrast transcranial Doppler (c-TCD) has a high sensitivity for detecting right-to-left shunt (RLS), and is probably higher than transthoracic echocardiography (TTE) and comparable with transesophageal echocardiography (TEE).

Objective: To evaluate the accuracy of echocardiography (TTE and TEE) to detect RLS compared to c-TCD.

Material and methods: Observational study of patients <55 years old with cerebral ischaemia of undetermined origin (2007-2009). All underwent c-TCD monitoring to detect RLS, at rest and after Valsalva manoeuvre (VM). The TTE and TEE were performed when indicated by our cerebrovascular protocol. The accuracy of TTE and TEE for detecting RLS was calculated by comparing them with c-TCD.

Results: A total of 115 patients with c-TCD, mean age 43.3 (SD 10.3) years, 51.3% male. The TTE was performed in 102, and TEE in 81, patients. RLS detection was higher with c-TCD than with TTE (67.6% vs. 22.5%, P=.001) or TEE (77.8% vs. 53.1%, P=.001). The TTE, compared with c-TCD after MV showed: sensitivity 31.8%, specificity 96.9%, positive predictive value (PPV) 95.6%, negative predictive value (NPV) 40.5% and accuracy 52.9% to detect RLS. TEE, compared with c-TCD after MV showed: sensitivity 63.4%, specificity 83.3%, PPV 93%, NPV 39.4% and accuracy 67.9%. The accuracy of TTE and TEE improved when they were compared with c-TCD at rest.

Conclusions: TTE and TEE show a considerable number of false negatives for RLS detection. Clinical studies should consider the c-TCD as the best technique to diagnose RLS when a paradoxical embolism is suspected.