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Right and left ventricular long-axis function in the fetus using angular M-mode
J S Carvalho1, C O'Sullivan, E A Shinebourne
1Department of Fetal Cardiology, Royal Brompton Hospital, London, UK. j.carvalho@rbh.nthames.nhs.uk
Objective:
Long-axis function is determined by the longitudinally oriented myocardial fibers. Postnatally, conventional M-mode is used to assess tricuspid and mitral valve ring movements in relation to the cardiac apex. During fetal life, this is precluded by variable fetal position. We assessed the feasibility of determining right and left ventricular long-axis function in the fetus.
Methods:
A prospective, pilot study. The four-chamber view obtained during routine fetal echocardiography was recorded in a cineloop to which B-mode guided M-mode echocardiography was applied using angular M-mode. This allowed retrospective and correct placement of the cursor line from cardiac apex to tricuspid or mitral valve rings. M-mode tracings of the valve ring movements in relation to the apex were derived from the originally stored loop. Data from 18 fetuses (17-29 weeks of gestation) were available for analysis. Total excursion of the valve rings was measured offline. A second cursor line was simultaneously placed in the left ventricular outflow tract during color flow mapping for timing purposes (n = 6).
Results:
Right and left ventricular long-axis recordings were obtained in 18 and 14 cases, respectively. Total right ventricular excursion was 5.2 mm (SD, 0.9 mm) (range, 3.9-7.2 mm). Total left ventricular free wall excursion was 4.5 mm (SD, 1.1 mm) (range, 3.0-6.8 mm). For paired data, the mean of differences (right ventricle-left ventricle) was 0.8 mm (95% confidence interval 0.5-1.2). The valve rings moved towards the apex during systole (shortening) and away from it during diastole (lengthening). Peak downward movement coincided with cessation of aortic flow and diastolic lengthening with flow through the atrioventricular valves.
Conclusion:
Long-axis function in the fetus is feasible if M-mode angle correction is used. There was no clinically significant difference between tricuspid and mitral valve excursions. The pattern of atrioventricular valve movement is coordinate and similar to that of adults. Long-axis function offers a new avenue to study systolic and diastolic function in the fetus.