Transthoracic second harmonic two- and three-dimensional echocardiography for detection of patent foramen ovale.

AIMS: Transoesophageal echocardiography (TEE) with contrast administration is still considered as the reference method for the detection of patent foramen ovale (PFO) with interatrial shunt, but it is a semi-invasive exam. The aim of the present study is to evaluate a role of two- and three-dimensional transthoracic echocardiography (TTE and R3DTE) as a diagnostic alternative to transcranial Doppler ultrasound (TCD) and TEE for detection of atrial right-to-left shunt.

METHODS AND RESULTS: Seventy-five patients with history of cerebrovascular events were subjected to four diagnostic examinations: TCD, TTE, R3DTE, and TEE, with bubble contrast. Bubbles in the left atrium within three cardiac cycles were considered diagnostic for PFO and later as a pulmonary shunt. Greater than 20 bubbles in the left atrium were considered a large shunt and <20 a small shunt. Every exam was read blinded to the results of the others. From the 75 enrolled patients, 62 (82.6%) patients showed right-to-left shunt with TEE; the results were also positive in 53 patients using TCD (70.6%), in 53 using R3DTE (70.6%), and in 55 using TTE (73.3%) (P = NS). There is a statistically significant superiority for TEE in the capacity of detecting shunts compared with TCD (P < 0.024), TTE (P < 0.018), and R3DTE (P < 0.018). The TEE presents a superior ability to recognize mild/moderate interatrial shunts respect to other exams (P = 0.003), without differences for shunts of high degree. In comparison to the TEE, the sensitivity is 89% for TTE, 88% for R3DTE, and 85% for TCD; the specificity is 100% for TTE and R3DTE, and 90% for TCD; the positive predictive value is 100% for TTE and R3DTE, and 98% for TCD; and the negative predictive value is 65% for TTE, 65% for R3DTE, and 53% for TCD. Considering only for mild/moderate shunts, the diagnostic accuracy is clearly inferior (sensitivity 63% for TTE, 58% for R3DTE, and 53% for TCD).

CONCLUSION: In this cohort of patients, TEE confirms the role of 'gold standard' exam for the detection of PFO; the non-invasive methods, and the TTE in particular, present a good diagnostic accuracy, but are inferior to the TEE because of the low negative predictive value and the non-optimal detection of small shunts. If the only purpose of TEE is the detection of significative interatrial shunt, TEE can be replaced by TTE. The R3DTE presents a good diagnostic accuracy, provides a better anatomical definition of the interatrial septum, and may have a role in this setting of patients, but does not add a lot to the TTE for the diagnosis.