الفهرس 
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Abstract
Objectives:
Myocardial mechanical dysfunction and ventricular dyssynchrony are frequent findings in idiopathic dilated cardiomyopathy (IDCM). We hypothesized that IDCM patients have differentially abnormal functional reserve limiting their exercise capacity. We investigated response of LV deformation in longitudinal and circumferential direction, to exercise in IDCM using 2D-strain imaging and find its relationship to exercise capacity.
Methods:
30 IDCM patients(39.1±12 years) and 33 healthy individuals underwent resting and peak exercise echocardiography using 2D-strain imaging. Peak longitudinal 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:
The absolute values of longitudinal ɛsys and SRsys were significantly smaller in IDCM patients than control at segmental and global level both at rest and at peak exercise (P<.001). Functional reserve was markedly impaired in IDCM(εsys: 7±6% versus 28±5% SRsys: -39±11% versus 40±12%; SRe : -26±10% versus 48±9% SRa -
6±14 versus 21±22%; %Circ strain: 22.4±9.3 versus 33.4±50%) compared to control group (P<.0001). LV mechanical dyssynchrony (TTP-SD) was marked in IDCM at rest and amplified at peak stress (68±35, 104±70 ms) compared to control (28±17, 21±12 ms) P<.000. Exercise capacity in IDCM showed direct correlation to both systolic and diastolic reserve (P<.01). Multivariate regression analysis demonstrated that reserve in early diastole, ΔSRe (β 0.501; P=0.001) and late diastole, ΔSRa (β:0.722; P=0.007) were independent predictor of exercise capacity.
Conclusion:
IDCM patients have limited systolic and diastolic function reserve and more dynamic dyssynchrony with exercise compared to healthy individual. However functional reserve during diastole remains the principle and independent predictor of exercise capacity in this population.