Louie E K, Liu D, Reynertson S I, Loeb H S, McKiernan T L, Scanlon P J, Hariman R J
Hines Veterans Administration Hospital, Illinois, USA.
J Am Coll Cardiol. 1998 Dec;32(7):2081-6. doi: 10.1016/s0735-1097(98)00508-7.
This study compared left atrial and left atrial appendage contraction velocities in sinus rhythm before and after a brief period of atrial fibrillation in a canine model.
In patients, left atrial appendage contraction velocities measured during sinus rhythm after cardioversion from atrial fibrillation are depressed relative to left atrial appendage emptying velocities measured during atrial fibrillation, suggesting that the left atrial appendage is mechanically "stunned."
This phenomenon was studied in a canine model of acute (60 min) pacing-induced atrial fibrillation followed by spontaneous reversion to sinus rhythm using epicardial and transesophageal pulsed wave Doppler. Unique features of the model include: 1) comparison of left atrial function postconversion to baseline sinus rhythm rather than to measurements during atrial fibrillation, 2) control of the duration of atrial fibrillation and 3) elimination of the extraneous influences of direct current shock and antiarrhythmic agents, which may independently depress left atrial function.
Hemodynamic conditions (heart rate, mean arterial pressure, cardiac output, mean pulmonary artery pressure, mean right atrial pressure and mean left atrial pressure) at baseline, during 60 min of atrial fibrillation and after reversion to sinus rhythm were constant throughout the study period. Peak left atrial contraction velocities (measured from the transmitral flow velocity profile) were significantly (p < 0.02) reduced to 64+/-22% of baseline values upon spontaneous conversion of atrial fibrillation to sinus rhythm and recovered to basal values by 20 min after resumption of sinus rhythm. Peak left atrial appendage contraction velocities were significantly (p < 0.001) reduced to 49+/-24% of baseline values upon spontaneous conversion of atrial fibrillation to sinus rhythm and recovered to basal values by 40 min after reversion to sinus rhythm.
Even brief (60 min) periods of atrial fibrillation in normal canine hearts result in marked depression of global left atrial systolic function and regional left atrial (left atrial appendage) systolic function upon resumption of sinus rhythm. This "mechanical stunning" of left atrial systolic function appears to be more profound and of longer duration for the left atrial appendage compared with the left atrium as a whole, which may predispose the appendage to blood stasis and thrombus formation. Chronic models of atrial fibrillation need to be developed to examine the impact of longer periods of atrial fibrillation upon the magnitude and duration of postconversion left atrial "stunning."
本研究在犬模型中比较了短暂房颤前后窦性心律时左心房及左心耳的收缩速度。
在患者中，房颤转复后窦性心律期间测得的左心耳收缩速度相对于房颤期间测得的左心耳排空速度降低，提示左心耳出现机械性“顿抑”。
使用心外膜和经食管脉冲波多普勒，在急性（60分钟）起搏诱导的房颤犬模型中研究这一现象，随后观察其自发恢复窦性心律的情况。该模型的独特之处包括：1）将转复后左心房功能与基线窦性心律时进行比较，而非与房颤期间的测量值比较；2）控制房颤持续时间；3）消除直流电休克和抗心律失常药物的额外影响，这些因素可能独立降低左心房功能。
在整个研究期间，基线、60分钟房颤期间及恢复窦性心律后，血流动力学状况（心率、平均动脉压、心输出量、平均肺动脉压、平均右心房压和平均左心房压）保持恒定。房颤自发转为窦性心律后，左心房收缩峰值速度（从二尖瓣血流速度曲线测量）显著降低（p<0.02），降至基线值的64±22%，恢复窦性心律20分钟后恢复至基础值。房颤自发转为窦性心律后，左心耳收缩峰值速度显著降低（p<0.001），降至基线值的49±24%，恢复窦性心律40分钟后恢复至基础值。
即使是正常犬心脏短暂（60分钟）的房颤，恢复窦性心律后也会导致左心房整体收缩功能和局部左心房（左心耳）收缩功能明显降低。与整个左心房相比，左心耳收缩功能的这种“机械性顿抑”似乎更严重，持续时间更长，这可能使心耳易发生血液淤滞和血栓形成。需要建立慢性房颤模型，以研究较长时间房颤对转复后左心房“顿抑”的程度和持续时间的影响。
