Journal o f the American Socicty o f Echocardiography Volume 9 N u m b e r 3 Abstracts 389

4 0 1 F TWO-DIMENSIONAL LEFT VENTRICULAR MASS AND VOLUME DETERMINATION: NORMAL RANGES 1N THE FIRST YEAR OF LIFE Erik C. Michelfelder MD, Susan Bemti, Achi Ludomirsky ME) University of Michigan Medical Center, Ann Arbor, MI

The normal range of left ventricnlar mass (LVM), determined by 2- D echocardiography, has not been well established in infants. The purpose of this study was to determine the normal range of LV mass, volume, and mass/volume ratio by 2-D echocardiography in infants less than one year of age. Echocardiographic studies of 27 patients referred for evaluation of cardiac murmur, without cardiac disease, were reviewed. Patient age was 2d-9mo (mean, 3.4mo). M/F ratio was 15/12. Patient height and body surface area (BSA) were noted. LV volumes were determined using the area-length (AL) equation V = 5/6(AL),.where A = LV cross-sectional area m the parasternal short axis vmw, and L = LV long axis measured from the apical 4-chamber (A4C) view. LVM was calculated as the difference in epi- and endocardial volume times myocardial density. LVM/volume ratio was calculated as L V M / L V end- diastolic volume. Digital planimetry of the LV in the A4C view allowed estimation of LVM using a truncated ellipse (TE) model. LVM was also determined using standard M-mode. Values were calculated as the average of 3 consecutive cardiac cycles. Linear regression analysis generated growth curves and 95% tolerance limits. 2-D LVM (r-0.93, p<0.001) and end-diastolic volume (r-0 93, p<0.001) correlated well with height; 2-D LVM (r=0.92, p<0.001) and end-diastolic volume (I=0.91, p<0.001) also correlated welI with BSA. AL and TE methods agreed well 0=0.99); however, AL values were slightly greater than TE values (mean difference 1.89gin, limits of agreement 0.39-3.39gm). AL and m-mode estimates agreed poorly (r=0.84, mean difference 2.29gm, limits of agreement -3.75 to 8.33). Mean LVM:volume ratio was 1.23 _+ 0.21 grrdcm 2, and was not related to height (r-0.06) or BSA (r=0.07). Conclusions: 1.) LVM correlates in a linear fashion with height and BSA in the first year of life; 2.) LVM/volume ratio is constant in the first year of life; 3.) AL and TE estimations of LVM agree well; 4.) M-mode determination of LVM does not agree well with 2-D estimates.

4 0 1 H WALL STRESS ANALYSIS/VOLUME INFUSION IN PEDIATRIC SEPTIC SHOCK: ANALYSIS OF PRELOAD DEFICIT Steve Kaine, MD, Arwa Saidi, MD, Ricardo Pignatelli, MD, Tim Feltes, MD, Texas Children's Hospital, Houston, TX

Introduction: Wall stress analysis (WSA) has been used to charac[erize LV systolic mechanics in sepsis (Crit Care Med 22:1647/94). LV preload, reflecting both filling pressure (intravasculai volume) and compliance, is decreased in these patients beyond the initial treatment phase. To determine the mechanism for persistent preload deficit, we studied the effects of acute volume administration on LV systolic mechanics in septic children. Methods: Pts (N=4) with ACP/SCCMCC criteria for septic shock were studied using WSA following initial fluid resuscitation (63 _+ 43 ml/kg). Exclusions included: increased ICP, PEEP > 12, renal failure, anasarca or pulmonary edema, CVP~o,o > 15. LV end- diastolic dimension (EDD) and functional preload index (FPI) were calculated using age-adjusted Z-scores for stress-shortening (preload- dependent) and stress-velocity indices (preload-independen0 as previously described. A Z-score < - 2 was regarded as a significant preload deficit. EDD & FPI before (EDDb~.o~, FPlb~J~,,~) and after (EDD~oE,,,~, FPI~o~o,=) volume infusion (5% albumin, 10-15 ml/kg) were measured. AEDD~, AFPI~ [(EDD or FPLo,o~)-( EDD or FPtb,,~r~o.)/ml] were also calculated. Controls (N 5) were a comparable group of children with stractnratly normal hearts undergoing electrophysiologic catheterization. Decreased AEDD~, AFPL vs controls indicates decreased LV emnpliance. Results:

I[Iudex Control Septic Shock 12 Value ] EDDh~,o,~.~ -1.7 + 0.7 1.1 ± 3.0 0.64 EDDv,,I~o,, -1.2 ± 0.8 -0.3 ± 2.4 0.48

]AEDD~ +0.5 ± 0.4 +0.7 -+ 0.7 0.62 [FPlh~ +0.3 ± 0.5 4. l ± 2.4 <0.01 /VPlv,,,,~, + 1.6 -+ 0.4 -2.9 +_ 2.6 <0.0l /,SFPL + 1.3 -+ 0.4 + 1.2 -+ 1.5 0.84 (Mean -+ SD)

Conclusions: Comparable changes in LV preload indices following volume infusion in these two groups indicate that children with septic shock have a persistent intravaseular volume depletion despite initial fluid resuscitation and are not consistent with significant impairement of LV compliance.

4 0 1 G QUANTITATIVE VENTRICULAR ASSESSMENT WITH MAGNETIC RESONANCE IMAGING AND ECHOCARDIOGRAPHY IN PATIENTS WITH SINGLE RIGHT VENTRICLES

LI Bezold MD, TJ Forbes MD, R Pignatelli MD, GL Johnson MD, DL Keamey MD, DJ Fisher MD, RJ Gajarski MD, GW Vick ill MD, PhD, Texas Children's Hospital, Houston, TX.

Study Purposes: l) to evaluate magnetic resonance imaging (MR[) in estimating actual volumes of hearts with single right ventricle (RV) morphology; 2) to compare multiple echocardiographic volumetric methods to MRI in estimating RV volume in patients with single RV morphology. Methods: Casts were made from 11 cadaver hearts with single RV morphology. The casts were imaged using a 1.5 Tesla clinical MRI system, employing imaging parameters similar to those typically employed in patient studies. For MR/estimation of volumes we used a Simpson's role method that made no assumptions regarding ventriuular geometry. The casts were then immersed in water and the actual volume determined by volume displacement. The results were compared to the MRI estimates of veutrieular volume. In the second part of our stud), we performed cardiac MRI and echocardiographic examinations on 5 patients with single RV morphology Echocardiographic and MRI studies were completed within 3 days of each other. Echocardiographic volumetric techniques employed were single plane long axis, biplane long axis, modified biplane Iong axis and bullet methods. Results: MRI accurately estimated the actual volumes of the cadaver RV casts:

Actual volume (cc) - MRI volume (cc)*0,96, r 2 = 0.998. Of the echocardiographic methods employed for estimating single RV volume, the bullet method correlated best with MRI results:

MRI volume (cc) - Bullet volume (ec)*1.03 + 2(cc). r 2 = 0.99. The long axis echocardiographic methods consistently provided 16-35% lower estimates of RV volume than MRI. Comparative results were similar for RV mass and ejection fraction. Conclusions: MRI is a very accurate method of determining RV volumes and mass in patients with single RV nmrphology. Echocardiographic volume determination using the bullet method is also a reliable technique for assessment of RV volume and mass in patients with mm-phologic single RVs.

4 0 1 I ACQUISITION OF THREE DIMENSIONAL FETAL ECHO- CARDIOGRAMS USING AN EXTERNAL TRIGGER SOURCE Jeffrey Kwon, Elizabeth Shaffer MD, Robin Shandas Ph.D, Ole Knudson. Curt DeGroff MD, Lilliam Valdes-Cruz MD. The Children's Hospital, Denver, CO. Three dimensional (3D) fetal echocardiography is a promising method for detecting congenital heart disease in utero, offering improved spatial resolution over standard 2D fetal imaging. In order to reconstruct a 3D fetal echocardiogram, an adequate trigger source is necessary for proper timing in the 3D reconstruction algorithm. We used an external trigger source at the same frequency as the fetal heart rate for gating in the 3D acquisition process. M e t h o d s : We studied 7 fetuses varying from 23-32 weeks gestation. The average fetal heart rate was obtained by Doppler and used as the frequency of the external trigger source produced by a function generator. 3D acquisition on a Tonrtec system was obtained by sweeping the transducer across 45 o in increments varying from 0.2 to 1.0 °. Average acquisition time was 49 seconds. Respiration limits were not used. 3D reconstruction was performed using varying threshold and opacity limits. Results: Three dimensional images could be reconstructed from 4 fetuses. Reconstructions demonstrated enhanced visualization of the cardiac chambers, septae, forarnen ovale and septal insertion of the atrioventricular valves. In the 3 unsuccessful trials, excessive fetal movement and poor acoustic windows were the major obstacles. All 3D reconstructions had an artifact which was exhibited as sinusoidal movement of the internal structures. This artifact may he induced by variance in the fetal heart rate or maternal respiration. C o n c l u s i o n : Use of an external trigger source for gating is a promising technique for the 3D reconstruction of fetal echocardiograms. Major technical obstacles at present are variations in the fetal heart rate and fetal position during the acquisition time,