异丙肾上腺素增加清醒兔缺血性心力衰竭的呼吸曲线斜率
Isoprenaline increases Excursive Restitution Slope in the Conscious Rabbit with Ischaemic Heart Failure
摘要：
背景：QT/RR斜率增加被认为是心肌梗死后心源性猝死的预测指标。既往研究表明β-肾上腺素能刺激可增加QT/RR斜率，但β-肾上腺素能刺激对心力衰竭QT/RR斜率的影响尚不清楚。研究方法：新西兰白兔接受冠状动脉结扎（n=15）或假手术（n=11），并在右心室植入儿科起搏器电极导线进行长期ECG记录。手术后8周，未镇静的家兔静脉注射0.25至2.0 ml 1 μ mol/l异丙肾上腺素，同时测量QRS峰至QRS（RR）和Q峰至T峰（QT）间期。结果如下：结扎组（n=6）的LVEF低于假手术组（n=7，p<.0001），但基线RR相似（269 +/- 15 vs 292 +/- 23 ms，p=.07），QT（104 +/- 17 vs 91 +/- 9 ms，p=.1）和最小RR（204 +/- 11 vs 208 +/- 6 ms，p=.4）异丙肾上腺素诱导的间期（0.79 +/- 0.18 vs 0.73 +/- 0.14 ml，p=.6）。QT与TQ间期图的滞后显示双相恢复和负斜率区域。结扎兔的正斜率区域斜率>1（1.27 +/- 0.66），假手术兔的正斜率区域斜率<1（0.35 +/- 0.14，p= 0.004）。结扎兔的负斜率绝对值更大（-0.81 +/- 0.52 vs -0.35 +/- 0.14，p= 0.04）。结论：缺血性心力衰竭在β-肾上腺素能诱导的QT/TQ滞后过程中产生更陡的恢复斜率。这可能是心脏衰竭发生心律失常的倾向的基础。
英文摘要：
Background: An increased QT/RR slope is hypothesized to be predictive of sudden cardiac death after myocardial infarction. Previous studies have shown that beta-adrenergic stimulation increases QT/RR slope, but the effects of beta-adrenergic stimulation on QT/RR slope in heart failure are unknown. Methods: New Zealand White rabbits underwent coronary ligation (n=15) or sham surgery (n=11), and implantation of a pediatric pacemaker lead in the right ventricle for chronic ECG recording. Eight weeks after surgery, unsedated rabbits were given intravenous administrations of 0.25 to 2.0 ml of 1 micromol/l isoprenaline, while peak QRS to QRS (RR) and Q to T peak (QT) intervals were measured. Results: Ligated rabbits (n=6) had lower LVEF than sham rabbits (n=7, p<.0001), but similar baseline RR (269 +/- 15 vs 292 +/- 23 ms, p=.07), QT (104 +/- 17 vs 91 +/- 9 ms, p=.1) and minimum RR (204 +/- 11 vs 208 +/- 6 ms, p=.4) intervals induced by isoprenaline (0.79 +/- 0.18 vs 0.73 +/- 0.14 ml, p=.6). Hysteresis in QT vs TQ interval plots displayed biphasic restitution and regions of negative slope. The slope of the positive slope region was >1 in ligated rabbits (1.27 +/- 0.66) and <1 in sham rabbits (0.35 +/- 0.14, p=.004). Absolute value of the negative slope was greater in ligated rabbits (-0.81 +/- 0.52 vs -0.35 +/- 0.14, p=.04). Conclusion: Ischaemic heart failure produces steeper restitution slopes during beta-adrenergically induced QT/TQ hysteresis. This could underlie the propensity of failing hearts to arrhythmias.
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