Improved Imaging of Aortic Coarctation

A 6-week-old girl with a history of failure to gain weight was referred to our institution for evaluation of a cardiac murmur. On physical examination, the patient weighed 4.5 kg. A nonspecific, grade 3/6 systolic murmur was present along the left sternal border. She had weak femoral pulses bilaterally. A clinical diagnosis of coarctation of the aorta was made. On transthoracic echocardiography, moderate aortic arch hypoplasia distal to the left carotid artery was visible, but it was difficult to see the area of juxtaductal coarctation on the 2-dimensional echocardiogram. The Doppler-estimated peak gradient was 38 mmHg, with a mean systolic gradient of 21 mmHg. The left ventricular size and systolic function were normal. Cardiac magnetic resonance imaging with gadolinium was performed to further delineate the area of coarctation. These images were not optimal until a 3-dimensional reconstruction was performed, which showed severe coarctation at the juxtaductal location.

In the operating room, transesophageal echocardiography (TEE) was performed with use of a miniaturized (3.3-mm, 10F) longitudinal, phased-array, intracardiac ultrasound probe (5.5–10 MHz, AcuNav™, Acuson, Inc.; Mountain View, Calif).¹ Unlike the transthoracic echocardiogram in this patient, excellent images of the area of coarctation were obtained with this probe, which defined the length and width of the coarctation (Fig. 1A). Color-flow Doppler echocardiography demonstrated continuous flow across the area of coarctation (Fig. 1B). Continuous-wave Doppler showed systolic peaking with diastolic runoff. The quality of the signal was good despite the fact that the image was virtually horizontal. Patch repair of the hypoplastic arch and the coarctation was performed. Postoperative evaluation with use of 2-dimensional TEE showed relief of the coarctation (Fig. 2A). On color-flow Doppler, a nonturbulent systolic forward flow was visible (Fig. 2B).

Fig. 1 Preoperative evaluation of coarctation of aorta by transesophageal echocardiography with use of the high-frequency intracardiac probe (Acunav™). A) A 2-dimensional image shows the length (1.5 cm, between the 2 asterisks*) and the width (arrow) of the coarctation. B) Color-flow Doppler shows continuous, turbulent flow in the area of coarctation.

Fig. 2 A) Postoperative 2-dimensional transesophageal echocardiographic images are consistent with adequate relief of coarctation. B) Postoperative color-flow Doppler shows normal systolic forward flow across the repaired coarctation.

Comment

The high-frequency (10-MHz) intracardiac probe provides very good near-field imaging of the descending thoracic aorta. The probe is very easily inserted, and we have not experienced any esophageal injuries with this technique; however, the mobility of the probe tip is limited. Because of the longitudinal imaging plane of this device, it is ideally suited for imaging the long axis of the descending aorta. Short-axis images are not possible but were not necessary in this patient. When evaluation of aortic coarctation is unsatisfactory by transthoracic echocardiography, use of this intracardiac imaging probe for TEE can be useful and may eliminate the need for magnetic resonance imaging.