Detection of Wall Motion Abnormalities during Ambulatory Echocardiography Using a Novel Ultrasound Transducer

Abstract

This investigation was designed to determine whether transient wall motion abnormalities due to myocardial ischemia induced by walking could be detected by ambulatory echocardiography. Two groups were studied. Group 1 consisted of 10 males (mean age 34 years) who had no symptoms of angina. Group 2 consisted of eight selected patients (mean 61 years) with angina and angiographic evidence of coronary artery disease. The 2.5 MHz transducer is spherical in its distal part and mounted in an external housing to permit steering in 360°. The external housing was attached to the chest wall using an adhesive patch. The transducer was placed in the 3rd or 4th intercostal space at the left sternal border to permit imaging of the left ventricle (LV) in its short axis and attached to the chest wall. The transducer was interfaced with an Acuson Cypress echocardiography system which was placed on a mobile cart. To permit portability, the echocardiography system was powered by a capacitor (UPS device). The subjects were asked to walk along the corridor as fast as possible for 10 minutes or until the onset of symptoms while pushing the cart. The short axis of the LV was displayed on a monitor and recorded on optical disks. The heart rate, systolic blood pressure (SBP), and double product of Group 1 at rest were 77 ± 3 beats/min, 119 ± 13 mmHg, and 9,150 ± 868, respectively, and increased to 106 ± 8 beats/min, 129 ± 15 mmHg, and 1,3793 ± 2,176 with walking. The baseline heart rate, SBP, and double product were 71 ± 12 beats/min, 130 ± 14 mmHg, and 8,555 ± 1,928 in Group 2 and increased to 94 ± 14 beats/min, 135 ± 20 mmHg, and 12,480 ± 3,830 with walking. All patients in Group 1 had normal wall motion at rest and during walking. Patients in Group 2 had normal wall motion during rest and new wall motion abnormalities were noted in all subjects during walking (anterior septum and/or anterolateral wall in seven, posterolateral wall in one). The wall motion abnormalities resolved shortly after discontinuation of walking. Ambulatory echocardiography permitted the detection of transient wall motion abnormalities in patients with coronary artery disease (CAD). This technique could be potentially useful in evaluating selected patients for myocardial ischemia.