Division of Cardiology, Department of Internal Medicine, Cardiovascular Center, Seoul National University Hospital, Seoul, Korea.
Circ Cardiovasc Imaging. 2010 May;3(3):272-81. doi: 10.1161/CIRCIMAGING.109.890848. Epub 2010 Feb 27.
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.
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).
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.
左心室（LV）负荷条件对 LV 不同步的影响尚未阐明。我们改变 LV 负荷条件，以揭示其对有记录的非缺血性扩张型心肌病患者的超声心动图衍生的 LV 不同步指数（LVdys）的影响。
连续纳入 37 例患者。在基线测量后，使用下肢气动加压（Pcom）增加 LV 后负荷。随后，给予舌下硝酸甘油（SL-NG）以改变前负荷。在每种情况下计算常规超声心动图参数、LVdys（通过斑点追踪径向应变分析）和 LV 收缩末期壁应力（LV-ESWS）。在 Pcom 下，LVdys-6（定义为 6 个节段的径向应变达峰时间的最大差异）和 LV-ESWS 增加（对于 LVdys-6，基线时为 159+/-117ms，Pcom 时为 239+/-140ms，P<0.05；对于 LV-ESWS，基线时为 191+/-63g/m2，Pcom 时为 228+/-80g/m2，P<0.05）。在 SL-NG 应用后，这两个参数均显著降低（在 Pcom 下为 239+/-140ms，在 SL-NG 后为 147+/-103ms，P<0.05；在 Pcom 下为 228+/-80g/m2，在 SL-NG 后为 189+/-67g/m2，P<0.05）。当 LV 不同步的存在定义为前间隔和后间隔节段的径向应变达峰时间的绝对差异（LVdys-2）时，结果保持不变。当使用 130ms 作为截断值时，LV 不同步患者的比例发生显著变化（基线时为 29.7%，Pcom 时为 45.9%，SL-NG 时为 35.1%）。当 LV 不同步的存在定义为 6 个节段的径向应变达峰时间的标准差（LVdys-SD）时，结果相同。LVdys 和 LV-ESWS 之间存在适度但显著的相关性（LVdys-6 为 r=0.47，P<0.001；LVdys-2 为 r=0.41，P<0.001；LVdys-SD 为 r=0.46，P<0.001）。
据我们所知，本研究首次提供了 LVdys 与 LV 负荷状态之间显著关联的证据，反映了 LVdys 的动态性质。因此，在使用超声心动图 LVdys 进行心脏再同步治疗候选者的临床决策选择或作为预后替代标志物时，应考虑 LV 负荷条件。
