الفهرس 
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Abstract
Objectives: Despite having normal EF at rest, we hypothesize that HCM patients have differentially abnormal systolic function reserve limiting their exercise capacity compared to healthy subjects. METHODS: 40 HCM patients (39.1±12 years) and 33 healthy individuals underwent resting and peak exercise echocardiography using 2D-strain imaging. Peak longitudinal (Log) strain (εsys), strain rate (SRsys,SRe, SRa) were measured in apical views. Circumferential (circ) εsys, LV twist were analyzed from short axis views. LV systolic dyssynchrony was measured from regional longitudinal strain curves as SD of TTP (time from beginning of Q wave on ECG to peak εsys) between 12 segments. The differences between resting and peak exercise values were analyzed (Δ) and the functional reserve is calculated as Δ /resting value. RESULTS: In HCM, resting values for Longitudinal εsys, SRsys, SRe and SRa were significantly lower, while Circ εsys and twist were higher, compared to control (p<.0001). Functional systolic reserve increased during exercise in control (17±6%), and markedly attenuated in HCM (-23±28%) P<.001. At peak exercise, even with augmented circ εsys and twist in HCM (P<.01) it remained lower than control (P<.001). LV dyssynchrony was amplified during exercise in HCM compared to control (P<.001). Within entire population, exercise capacity was Summary 76 clearly correlated to systolic functional reserve. However when taken separately in HCM, it was mainly related to resting LV dyssynchrony and diastolic function. CONCLUSION: HCM patients have significantly limited systolic function reserve and more dynamic dyssynchrony with exercise compared to healthy subjects. 2D-Strain during stress could provide a new and reliable method to identify patients at higher cardiovascular risk.