Second harmonic transthoracic echocardiography: the new reference screening method for the detection of patent foramen ovale.

AIM: Transesophageal echocardiography (TEE) is still considered as the reference method for the non-invasive detection of right-to-left shunts. Echocardiographic laboratories are spending most of their time performing TEE studies to exclude a thromboembolic cardiac disease. In a considerable proportion of these patients the question can be simplified to exclude a PFO. Replacing these TEE studies by TTE would result in a considerable gain in time and money. We evaluated the value of transthoracic echocardiography with second harmonic imaging (TTE) (SH) and peripheral intravenous agitated saline solutions in the detection of patent foramen ovale (PFO) in a large cohort of patients.

METHODS: In 256 consecutive patients, TEE and TTE (SH) with the consecutive administration of three intravenous contrast injections of agitated saline injections before the release phase of the Valsalva manoeuvre were performed. Semi-quantification and timing of contrast passage were assessed during both imaging modalities. A shunt was present if at least one imaging modality showed microbubbles appearing in the left atrium. PFO was defined when these bubbles appeared early and arteriovenous pulmonary malformations were suspected if bubbles appeared late after the opacification of the right atrium. Shunts were considered important when >20 bubbles were present in one frame in the left atrium or left ventricle.

RESULTS: From the 256 patients, 60 presented a passage of contrast from the right to the left atrium in at least one imaging modality. PFO was detected by TEE in 53 patients and by TTE in 55 patients (sensitivity: 90.5% and specificity: 96.5% if TEE is accepted as the golden standard) (p>0.05). Considering only the important shunts TEE detected 39 important shunts and TTE 46 important shunts (sensitivity: 89.7% and specificity: 94.6%) (p>0.05). AV pulmonary malformations were detected by TEE in 7 patients and by TTE in 10 patients (sensitivity: 85.7% and specificity: 98.3%) (p>0.05).

CONCLUSIONS: In this large cohort of patients TTE (SH) is as accurate as TEE for the detection of PFO and late right-to-left shunts. If the only purpose of TEE is the detection of PFO such as in young cryptogenic stroke patients and in divers, TEE can be replaced by TTE (SH).