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Fig. 11. Midesophageal view showing agitated saline contrast (bubble) study injection into the left arm. Bubbles were seen entering the coronary sinus, then the left atrium (LA), and then into the right atrium (RA).

Therefore, a dynamically patent orifice acting similar to a flap valve is present and may respond to interatrial pressure changes (Fig. 12; please see companion DVD for corresponding video; see alsOo Chapter 17). Thus a right-to-left shunt may be present when right atrial pressures increase higher than left atrial pressures, such as with Valsalva, coughing, and so on. The defect may be functionally sealed when left atrial pressures exceed right, with only occasional right-to-left shunting.

The presence of this defect is easily evaluated with agitated saline contrast injection. Normally, the procedure is performed with and without Valsalva maneuver, as right-to-left shunting may not be seen under baseline conditions. The presence of contrast bubbles early after appearance in the right heart indicates the presence of right-to-left shunting. Color Doppler over the area of the fossa ovalis can often detect this defect. Transthoracic subcostal imaging or multiplane transesophageal echocardiography can usually illustrate the defect.

ECHOCARDIOGRAPHY IN THE MANAGEMENT OF ASDs

An accurate evaluation of the hemodynamic impact of the shunt is necessary following diagnosis. The degree of shunt flow is quantified by indexing pulmonary blood flow to systemic blood flow, the Qp/Qs ratio.

Traditionally, when pulmonary blood flow exceeds systemic blood flow by 50% (a Qp/Qs ratio of 1.5:1.0), repair of the defect is recommended. However, in the case of ASDs with smaller shunts (ratios of <1.5:1.0), repair may still be appropriate owing to the risks for other problems including atrial arrhythmias, progressive pulmonary hypertension, congestive failure, or paradoxic emboli. PFOs have been repaired after cryptogenic stroke, especially in young patients.

Percutaneous closure of secundum ASDs and PFOs have been performed using transcatheter devices in experienced centers. Recent clinical data suggests that percutaneous closure techniques are safe and effective, supporting a less invasive alternative to surgical closure. A variety of devices are available for transcatheter closure such as the Amplatzer and CardioSeal closure devices.

The deployment of transcatheter devices for ASD or PFOs are generally guided by echocardiography techniques (Fig. 12; please see companion DVD for corresponding video). Transesophageal echocardiog-raphy or intracardiac echocardiography are important tools for the morphological characterization of the lesion. For example, an accurate description of the ASD size and rim measurements is invaluable information in guiding device deployment. During PFO

Fig. 12. Stages of percutaneous closure of a secundum atrial septal defect (ASD; A) using an Amplatzer device are shown on transesophageal echocardiography guidance. Balloon sizing of the defect (B) is followed by sequential deployment of the left atrial and right atrial arms of the device (C) (picture insert: AMPLATZER® Septal Occluder ASD). Following release of the device, interrogation of the closure was performed using Color Doppler (D) and agitated saline contrast. (Please see companion DVD for corresponding video.)

Secumdum Asd Rim Adequate For Closure

Fig. 12. Stages of percutaneous closure of a secundum atrial septal defect (ASD; A) using an Amplatzer device are shown on transesophageal echocardiography guidance. Balloon sizing of the defect (B) is followed by sequential deployment of the left atrial and right atrial arms of the device (C) (picture insert: AMPLATZER® Septal Occluder ASD). Following release of the device, interrogation of the closure was performed using Color Doppler (D) and agitated saline contrast. (Please see companion DVD for corresponding video.)

closure, transeptal puncture can be guided as well as an assessment of the PFO tunnel size and septal stiffness. Overall, echocardiography during device deployment is important for device sizing, positioning, and the assessment of residual shunting postdevice deployment (Fig. 12; please see companion DVD for corresponding video).

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