A 63-year-old woman with apical hypertrophic cardiomyopathy, complaining of moderate effort dyspnea and with no history of cerebrovascular accidents, was referred to our Department for hemodynamic characterization and possible percutaneous closure of a secundum ASD. Before catheterization, however, multiplane color Doppler TEE revealed a turbulent, continuous left-to-right shunt within a double contour image of the atrial septum (Figure 1), that is the hallmark of PFO. Moreover, the presence of 16-mm wall thickness localized at the mid-distal interventricular septum confirmed the presence of an apical hypertrophic cardiomyopathy. At cardiac catheterization, performed under general anesthesia and TEE monitoring, pulmonary-to-systemic flow ratio was 1.4, without pulmonary arterial hypertension and with normal pulmonary resistance. Provocative maneuvers during contrast injections into the right femoral vein were not able to reverse the shunt. Coronary arteries were normal and LV angiography confirmed apical hypertrophy (Figure 2 and Video 1-See additional file 1). LV early- and end-diastolic pressures were 2 and 12 mmHg, respectively. The atrial septum was then crossed with a multipurpose diagnostic catheter: a pressure gradient was present between left (10 mmHg) and right (4 mmHg) atrium and, at TEE, the color jet appeared widened. Pulmonary venous angiography (Figure 3 and Video 2-See additional file 2) confirmed the left-to-right shunt through the abnormal interatrial communication.
Before proceeding to PFO closure, we performed a hemodynamic evaluation aimed at assessing the effect of the increased LV preload due to the abolition of the left-to-right shunt. For this purpose, an exchange stiff guide wire was kept in the left upper pulmonary vein and an Amplatzer (AGA Medical Corporation, Golden Valley, MN, USA) sizing balloon was introduced over the wire across the PFO and inflated to abolish the shunt [7]. LV early- and end-diastolic pressures, 5 minutes after SB inflation, rose up to 5 and 18 mmHg, respectively (Figure 4). Such a worsening of LV diastolic function due to the PFO occlusion suggested us not to perform the definitive procedure with the Amplatzer occluder.
The wide application of contrast TEE has revealed that paradoxical embolism through a PFO is likely to represent an under-recognized cause of stroke [8], but fewer reports have highlighted the possibility of a stable left-to-right shunt through a PFO [9], since the foramen ovale is generally considered an unidirectional flap-like valvular structure, that is functionally closed when left atrial pressure is higher than right. Nevertheless, it has been speculated that the foramen ovale may increase in size and allow a left-to-right overflow secondary to pressure-induced left atrial enlargement [5]; such a shunt may be easily misdiagnosed as secundum ASD at transthoracic echocardiography. Moreover, in the case of LV restrictive physiology, like in hypertrophic cardiomyopathy, a continuous left-to-right shunt through a PFO may act as an unloading mechanism for the left atrial chamber finalized at reducing LV filling pressures. Therefore it may be useful, in such cases and prior to any interventional procedure, to perform, under the controlled conditions due to general anesthesia, a rapid hemodynamic evaluation of the effect of the transient abolition of the shunt on LV function. This evaluation can easily be obtained with the inflation of the sizing balloon across the interatrial communication. The percutaneous closure procedure should not be performed if a worsening of LV function occurs.
