The use of contrast echocardiography for the detection of cardiac shunts.

Recently, debate has erupted about the clinical significance of cardiovascular shunts. Several major health problems such as stroke and migraine have been associated with patent foramen ovale (PFO) with right-to-left shunt (RLS). The nature of the relationship between these syndromes and PFO is not clearly understood. Technical advances have led to more therapeutic options including device closure of PFO, hence prevention of such a PFO-related stroke has become feasible. Therefore, optimal diagnosis of PFO has become of greater clinical importance. Contrast echocardiography with non-transpulmonary contrast agents has been the cornerstone in diagnosis of PFO with RLS for over four decades. Despite being a relatively invasive procedure, transesophageal echocardiography (TEE) is considered the gold standard for detection of RLS. Several other echocardiographic techniques such as transthoracic echocardiography (TTE) with second harmonic imaging and transcranial Doppler ultrasonography (TCD) have shown increased sensitivity and specificity compared to TEE for the detection of PFO with RLS. Moreover, improvement of skills and techniques used for detection of these shunts has led to greater detection of small and large sized RLS in the echocardiographic laboratory. This review gives and overview of the echocardiographic techniques, contrast agents and manoeuvres used for detection of the major cardiovascular shunts and their clinical relevance to major health problems.