Use of saline contrast echo timing to distinguish intracardiac and extracardiac shunts: failure of the 3- to 5-beat rule.

Patent foramen ovale (PFO) is thought to be associated with cryptogenic stroke and migraine headache. Saline contrast echocardiography (SCE) is the gold standard for identifying the presence of right-to-left shunt, whether from PFO or pulmonary arteriovenous malformation (PAVM). The timing of left heart contrast entry during SCE is used to distinguish a PFO from a PAVM, a method that is not as specific as previously thought. In this report, we describe a patient with a SCE demonstrating the early appearance of left heart bubbles during good effort Valsalva injections that is ultimately proven to be due to a PAVM. The case illustrates the limited specificity of left heart contrast timing during SCE as the sole criteria for differentiating intracardiac and extracardiac shunts.