OBJECTIVE: To evaluate the tissue Doppler acceleration imaging (TDAI) data which can be used to determine the intramural site of origin of myocardial contraction in response to electrical stimulation. METHODS: Six open-chest pigs with left ventricle (LV) pacing were evaluated with TDAI. An epicardial surface scanning method was used to collect short-axis views of the left ventricle. The electrode was implanted from the epicardium through the anterior free wall to an intramural position. RESULTS: During pacing, the intramural onset of myocardial acceleration occurred within 33 ms after electrical stimulation and always surrounded the embedded subendocardial end of the pacing needle. The observed short-axis diameter of the area of initial myocardial acceleration ranged from 2.9 mm to 5.0 mm (4.2 +/- 0.9 mm, n = 6). The onset of myocardial acceleration allowed appreciation of the initial intramural myocardial contraction. The spatial size and acceleration magnitude of the initial myocardial acceleration distribution were irregular. CONCLUSION: Two-dimensional myocardial acceleration mapping can show the intramural site of origin of myocardial contraction in response to paced electrical stimulation. The location of myocardial acceleration conformed to the site of initial electrical stimulation. The delay to the earliest regional myocardial contraction, 33 ms after paced electrical stimulation, was related to the frame rate of image acquisition.
OBJECTIVE: To evaluate the tissue Doppler acceleration imaging (TDAI) data which can be used to determine the intramural site of origin of myocardial contraction in response to electrical stimulation. METHODS: Six open-chest pigs with left ventricle (LV) pacing were evaluated with TDAI. An epicardial surface scanning method was used to collect short-axis views of the left ventricle. The electrode was implanted from the epicardium through the anterior free wall to an intramural position. RESULTS: During pacing, the intramural onset of myocardial acceleration occurred within 33 ms after electrical stimulation and always surrounded the embedded subendocardial end of the pacing needle. The observed short-axis diameter of the area of initial myocardial acceleration ranged from 2.9 mm to 5.0 mm (4.2 +/- 0.9 mm, n = 6). The onset of myocardial acceleration allowed appreciation of the initial intramural myocardial contraction. The spatial size and acceleration magnitude of the initial myocardial acceleration distribution were irregular. CONCLUSION: Two-dimensional myocardial acceleration mapping can show the intramural site of origin of myocardial contraction in response to paced electrical stimulation. The location of myocardial acceleration conformed to the site of initial electrical stimulation. The delay to the earliest regional myocardial contraction, 33 ms after paced electrical stimulation, was related to the frame rate of image acquisition.
Authors: Norman McDicken; Adrian Thomson; Audrey White; Iqbal Toor; Gillian Gray; Carmel Moran; Robin J Watson; Tom Anderson Journal: Echo Res Pract Date: 2019-12-01