Impact of loading condition on the 2D speckle tracking-derived left ventricular dyssynchrony index in nonischemic dilated cardiomyopathy.
BACKGROUND
The effects of left ventricular (LV) loading conditions on LV dyssynchrony have not been elucidated. We modified LV loading conditions to reveal their effects on echocardiography-derived LV dyssynchrony index (LVdys) in patients with documented nonischemic dilated cardiomyopathy.


RESULTS
Thirty-seven patients were consecutively enrolled. After baseline measurements, pneumatic compression of the lower extremities (Pcom) was used to increase LV afterload. Subsequently, sublingual nitroglycerin (SL-NG) was administered to modify preload. Conventional echocardiographic parameters, LVdys (by speckle-tracking radial strain analysis) and LV end-systolic wall stress (LV-ESWS), were calculated under each condition. LVdys-6 (defined as the maximal difference in time-to-peak radial strain between 6 myocardial segments) and LV-ESWS increased under Pcom (for LVdys-6, 159+/-117 at baseline versus 239+/-140 ms under Pcom, P<0.05; for LV-ESWS, 191+/-63 versus 228+/-80 g/m(2), P<0.05) After SL-NG application, both parameters decreased significantly (for LVdys-6, 239+/-140 under Pcom versus 147+/-103 ms after SL-NG, P<0.05; for LV-ESWS, 228+/-80 under Pcom versus 189+/-67 g/m(2) after SL-NG, P<0.05). When the presence of LV dyssynchrony was defined as the absolute difference in time-to-peak radial strain between the anteroseptal and posterior segments (LVdys-2), the results were unchanged. Using 130 ms as a cutoff value, the proportion of patients with LV dyssynchrony changed significantly (29.7% at baseline, 45.9% under Pcom, and 35.1% after SL-NG). When the presence of LV dyssynchrony was defined as standard deviation of the time to peak radial strain for 6 segments (LVdys-SD), the results were same. LVdys and LV-ESWS showed a modest but significant association with each other (r=0.47, P<0.001 for LVdys-6; r=0.41, P<0.001 for LVdys-2; r=0.46, P<0.001 for LVdys-SD).


CONCLUSIONS
To the best of our knowledge, the present study provides the first evidence of a significant association between LVdys and LV loading status, reflective of a dynamic nature of LVdys. Accordingly, LV loading conditions should be taken into account when echocardiographic LVdys is used for clinical decision-making of selecting candidates for cardiac resynchronization therapy or when it is used as a surrogate marker of prognosis.
Park
Hyo Eun
HE
Division of Cardiology, Department of Internal Medicine, Cardiovascular Center, Seoul National University Hospital, Seoul, Korea.
Chang
Sung-A
SA
Kim
Hyung-Kwan
HK
Shin
Dong-Ho
DH
Kim
Ji-Hyun
JH
Seo
Myung-Ki
MK
Kim
Yong-Jin
YJ
Cho
Goo-Yeong
GY
Sohn
Dae-Won
DW
Oh
Byung-Hee
BH
Park
Young-Bae
YB
D001794:Blood Pressure; D002311:Cardiomyopathy, Dilated / Q000150:complications / Q000000981:diagnostic imaging*; D015150:Echocardiography, Doppler / Q000379:methods; D005260:Female; D006339:Heart Rate; D006352:Heart Ventricles / Q000000981:diagnostic imaging*; D006801:Humans; D048228:Intermittent Pneumatic Compression Devices; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D018487:Ventricular Dysfunction, Left / Q000150:complications / Q000000981:diagnostic imaging*