Contribution of velocity profiles at the left ventricular outflow tract tocalculations of stroke volume: A magnetic resonance imaging study

Objective: The goal of the study was to determine whether the central veloc ity of the left ventricular outflow tract represents the mean velocity of t he total outflow area. Methods: Thirteen healthy men. (mean age, 30 +/- 6 y ears) and nine patients with aortic valve disease (seven with aortic regurg itation and two with aortic valve stenosis) were examined. Cine gradient ec ho images were obtained in the left ventricular outflow long axis. Cine ima ges with velocity mapping were obtained in the short axis of the outflow tr act. Values for peak velocity were obtained on the right-left axis and on t he anteroposterior axis. Distances were measured along the axes from the ri ght and anterior edges of the outflow tract at the point of peak velocity. Percentages of the distances for outflow diameter were calculated. Peak vel ocity at the Left ventricular outflow tract using pulsed-Doppler method wer e also measured. Results: lit normal subjects and in patients, on the right -left axis, the peak velocity was 87 +/- 16 and 72 +/- 11 cm/sec, respectiv ely, and the distance from the right edge of outflow tract corresponded to 19% +/- 8% and 21% +/- 7%, respectively. On the anteroposterior axis, the p eak velocity was 86 +/- 16 and 60 +/- 9 cm/sec, and the corresponding dista nce from the anterior edge was 30% +/- 13% and 41% +/- 12% for normal subje cts and patients, respectively. The central velocity of the outflow tract w as 74 +/- 15 cm/sec, whereas the mean of the total outflow tract was 74 +/- 13 cm/sec. Central and mean velocities of the outflow tracts as revealed b y magnetic resonance imaging showed a close and highly significant correlat ion in both groups. Velocity obtained by pulsed-Doppler method and mean vel ocity of the outflow tract by magnetic resonance imaging also showed signif icant correlation in both groups. Conclusions: Central velocity at the left ventricular outflow tract represented the mean of the total outflow tract both in normal subjects and in patients with aortic valve disease. The stro ke volume measured by pulsed Doppler is therefore considered reliable if th e sampling point is placed exactly at the center of the outflow.