Amitzur G, Manor D, Pressman A, Adam D, Hammerman H, Shofti R, Beyar R, Sideman S
Neufeld Cardiac Research Institute, Sheba Medical Center, Tel Hashomer, Israel.
Pacing Clin Electrophysiol. 1995 Apr;18(4 Pt 1):697-710. doi: 10.1111/j.1540-8159.1995.tb04664.x.
This study aims to test the assumptions that: (1) coronary arterial flow is attenuated in an early activated region by ventricular pacing; (2) asynchronous mechanical activation caused by ventricular pacing under controlled perfusion pressure and intact coronary tone is associated with reduced coronary flow compared to atrial pacing; and (3) abolishment of vascular tone under controlled perfusion pressure diminishes the expected difference in blood flow between atrial and ventricular pacing. Blood flow velocity (BFV) in the left anterior descending (LAD) and the left circumflex arteries (CFX) and a wall thickening index were measured in 14 open-chest dogs under normal conditions, and constant perfusion pressure. Four pacing sites were used: right atrium (RAp), mid-right ventricle (RVp), mid-left ventricle (LVp), and left ventricular apex (Apexp). Pacing modes were either sequential ventriculoatrial (VA) (protocol A, n = 7), or sequential atrioventricular (AV) (protocol B, n = 7), with a shorter AV difference (30 msec) than normal.
BFV was decreased in the LAD during RVp and Apexp pacing by 9.7%-12.9% versus RAp and by 11.6%-14.6% versus LVp (P < 0.05). No BFV variations were observed in the CFX. Flow velocity conductance (FVC = mean blood flow velocity divided by the mean aortic pressure) was higher by 16%-28% in the CFX for the three ventricular pacing sites versus the atrial pacing, and higher by 14.1% +/- 6.1% only in LVp versus RAp pacing in the LAD (P < 0.05). Wall thickening index reduced during ventricular pacing in all three ventricular sites by 50%-64% (P < 0.05) compared to atrial pacing. Under constant perfusion pressure, LAD blood flow decreased with ventricular pacing as compared to right atrial pacing; this was particularly pronounced during the diastolic phase (16.6%-45.5%, P < 0.02). Normalized oscillatory flow amplitude (OFAn) was reduced in RVp pacing compared to RAp and LVp pacing (16.2 +/- 3.5 and 21.7% +/- 4.1%, respectively, P < 0.03). The variations in blood flow and OFAn disappeared with adenosine-mediated maximum vasodilatation.
(1) Mean and phasic flows are reduced in the early activated LAD region by ventricular pacing (RVp, Apexp). (2) Under controlled perfusion pressure and intact vascular tone, ventricular pacing compromises blood flow compared with atrial pacing. (3) This effect disappears when vascular tone is eliminated by intracoronary injection of adenosine, suggesting that the coronary autoregulation is responsible for some of the effects.
本研究旨在验证以下假设：（1）心室起搏时，早期激活区域的冠状动脉血流会衰减；（2）在控制灌注压力和冠状动脉张力完整的情况下，心室起搏引起的异步机械激活与心房起搏相比，冠状动脉血流减少；（3）在控制灌注压力的情况下消除血管张力，可减少心房和心室起搏之间预期的血流差异。在14只开胸犬处于正常状态且灌注压力恒定的情况下，测量左前降支（LAD）和左旋支动脉（CFX）的血流速度（BFV）以及壁增厚指数。使用了四个起搏部位：右心房（RAp）、右心室中部（RVp）、左心室中部（LVp）和左心室心尖部（Apexp）。起搏模式为顺序性心室-心房（VA）（方案A，n = 7）或顺序性房室（AV）（方案B，n = 7），AV间期比正常情况短（30毫秒）。
与RAp相比，RVp和Apexp起搏时LAD的BFV降低了9.7%-12.9%，与LVp相比降低了11.6%-14.6%（P < 0.05）。CFX未观察到BFV变化。三个心室起搏部位的CFX的血流速度传导率（FVC = 平均血流速度除以平均主动脉压）比心房起搏高16%-28%，LAD中仅LVp与RAp起搏相比高14.1%±6.1%（P < 0.05）。与心房起搏相比，所有三个心室部位在心室起搏时壁增厚指数降低了50%-64%（P < 0.05）。在恒定灌注压力下，与右心房起搏相比，心室起搏时LAD血流减少；在舒张期尤为明显（16.6%-45.5%，P < 0.02）。与RAp和LVp起搏相比，RVp起搏时标准化振荡血流幅度（OFAn）降低（分别为16.2±3.5和21.7%±4.1%，P < 0.03）。腺苷介导的最大血管扩张使血流和OFAn的变化消失。
（1）心室起搏（RVp，Apexp）使早期激活的LAD区域的平均血流和搏动血流减少。（2）在控制灌注压力和血管张力完整的情况下，心室起搏与心房起搏相比会损害血流。（3）冠状动脉内注射腺苷消除血管张力后，这种效应消失，表明冠状动脉自动调节作用导致了部分效应。
