its high mortality identification of patients at high risk is crucial for optimized treatment strategies such as heart transplantation prior to causative amyloid therapy. Various parameters have been proposed for risk stratification, but failed consistently in the identification of high risk patients. We report rapidity of progression of left ventricular wall thickness (LVT) as a powerful predictor of death in patients with light-chain CA. Methods and Materials: LVT progression was compared to electro- cardiographic, echocardiographic, and clinical parameters in 39 pa- tients (56.51.4 years) with histologically proven CA. Results: 17 deaths occurred (1-/3-year-survival 62.1/55.0%). LVT pro- gression of the deceased patients was 2.020.85 mm/month compared to 0.190.03 mm/month of survivors (p0.001). In patients with autologous stem cell transplantation (n=22, 54%) LVT progression was reduced compared to patients without stem cell transplantation (0.210.04 mm/month vs. 1.450.57 mm/month, p0.005). LVT progression correlated with maximal LVT and absolute increase of LVT. LVT progression was more rapid in patients with impaired LV ejection fraction (LV-EF) than preserved LV-EF (2.161.04 mm/month versus 0.300.13 mm/month; p0.001). It closely correlated with survival, whereas initial, maximum, or absolute increase in LVT did not. Further univariate predictors of survival were LV-EF, stem cell transplantation, low voltage pattern, but not diastolic dysfunction. Multivariate analysis identified LVT progression as the only independent parameter for survival (in trend impaired LV-EF, p=0.09). Conclusions: LVT progression appears to represent a valuable indica- tor for risk assessment in light-chain CA potentially superior to param- eters as LV-EF, low voltage pattern, and autologous stem cell transplan- tation identifying patients for optimized treatment strategies such as heart transplantation prior to causative therapy. 503 MECHANICAL DYSSYNCHRONY IN PEDIATRIC CARDIOMYOPATHY M.K. Friedberg, 1 N.H. Silverman, 1 A.M. Dubin, 1 D.N. Rosenthal, 1 1 Division of Pediatric Cardiology, Stanford University, Palo Alto, CA Purpose: Mechanical dyssynchrony (MD) predicts response to cardiac resynchronization therapy (CRT) in adults with cardiomyopathy (CM) but has not been studied in pediatric CM. We studied MD in 25 children (107 y) with CM (FS%27) and 25 healthy cntrls using tissue Doppler (TDI) and vector velocity imaging (VVI). Methods and Materials: QRS to onset (Ts-onset) and peak (Ts-peak) systolic velocity (S’) intervals were measured by TDI to define lt and rt intra-ventricular delays and lt-rt inter-ventricular delay. Using VVI, time to peak S’ velocity, strain and strain rate were measured in 6 + 12 LV segments and standard deviation (SD) of these intervals calculated as a dyssynchrony index. We correlated mechanical and electrical dyssyn- chrony and MD and systolic function. Results: Children with CM had significant MD. Intra + inter-ventricular delays by TDI, and SD of time to peak S’, strain and strain rate by VVI were 2-3 times higher in CM pts than cntrls (Table). SD of time to peak strain did not correlate with QRS duration (r=0.02) and was similar between CM pts with narrow ( median 86 msec) and wide QRS ( 86 msec) (2018 v 2114 msec, p=0.89). QRS-peak S’ (velocity) did not differ between narrow and wide QRS groups (2822 vs 4233 msec, p=0.2). Conclusions: Children with CM have MD. Mechanical, rather than electrical dyssynchrony, may identify potential pediatric candidates for CRT. Dr Friedberg was a Glaser Pediatric research fellow. 504 LEFT VENTRICULAR SYSTOLIC ASYNCHRONY IN PEDIATRIC AND ADOLESCENT PATIENTS WITH CONGESTIVE HEART FAILURE G. Srinath, 1 A. Ali, 2 G. Rosenthal, 1 R. Grimm, 2 R. Sterba, 1 E. Saarel, 4 A. Younoszai, 3 G. Boyle, 11 Pediatric Cardiology, The Cleveland Clinic Foundation, Cleveland, OH; 2 Adult Cardiology, The Cleveland Clinic Foundation, Cleveland, OH; 3 Pediatric Cardiology, Children’s Hospital, Denver, CO; 4 Pediatric Cardiology, Primary Childrens Medical Center, Salt Lake City, UT Purpose: To study left ventricular (LV) systolic asynchrony in pediatric and adolescent patients with heart failure (HF). LV systolic asynchrony is common in adult patients with HF. Echocardiographic measures of LV systolic asynchrony in pediatric patients with chronic heart failure have not been defined. Methods and Materials: Sixteen children with HF and 11 normal children were prospectively evaluated in the congenital heart center of Cleveland Clinic. Echocardiography was performed with tissue Doppler imaging using six basal and six mid-segmental models, parasternal M-mode, and pulse wave Doppler. The degree of systolic intra-ventric- ular asynchrony was assessed by; the maximal difference in time to peak myocardial systolic contraction (Ts), the standard deviation of Ts (Ts-SD) of 12 LV segments, Septal-posterior wall motion delay (SPWMD) and inter-ventricular asynchrony by pulmonary and aortic Doppler flow. Results: The ages of those in the HF (7  5.9) and control group (9.4  5.7) were similar. The QRS durations were similar in (controls 91  12.3 ms v HF 81.7  20, p = NS) both. Measures of intra-ventricular asynchrony using maximal difference in Ts (controls 41.1 ms v HF 106.5 ms, p = 0.0003), standard deviation of Ts (Ts-SD) (controls 12.2  3.2 ms v HF 35.5  17.2 ms, p = 0.0002), and SPWMD (controls 43.4  14.9 ms v HF 116.6  48.9 ms, p = 0.0007) was prolonged in the heart failure patients compared with normal control. However, inter-ventric- ular asynchrony (controls 14.7  9.2 ms v HF 23.8  20.5 ms, p = 0.26) was not significantly prolonged in the HF group. When Ts – SD of  32.6 ms ( 2 SD of normal controls) was used to define significant systolic asynchrony, it was not found in control subjects but was present in 6 (46%) patients with HF. Stepwise multiple regression analysis showed that LVEDV was an independent predictor of systolic asynchrony. Conclusions: LV systolic asynchrony is common in pediatric patients with heart failure irrespective of QRS duration. QRS duration is not a determinant of systolic asynchrony in pediatric patients. Mechanical Dyssynchrony Control Cardiomyopathy p TDI Ts-Onset (msec) LV IntraV* 7.5  6.5 19  16 0.003 RV IntraV* 10  11 26  21 0.015 InterV†delay 14  11.5 25  21 0.08 TDI Ts-peak (msec) LV IntraV* 15  11 35.5  29 0.0024 RV IntraV* 11.5  7 26  21 0.015 InterV† 20.5  14 48  30 0.002 VVI velocity SD (cm/s) 6 seg 9  7 40  27 0.0002 12 seg 11  7 35  25 0.0007 VVI strain SD (%) 6 seg 8  7.5 22  16 0.0035 12 seg 8  6 19  14 0.0041 VVI strain rate SD 6 seg 8  10 25  28 0.014 12 seg 11  9 25  24 0.015  Intra V, Intra-ventricular delay † InterV, Inter-ventricular delay. The Journal of Heart and Lung Transplantation Abstracts S241 Volume 26, Number 2S