Klaar Ursula, Berger Rudolf, Gwechenberger Marianne, Wutte Michael, Porenta Gerold, Sochor Heinz, Maurer Gerald, Baumgartner Helmut
Department of Cardiology, Vienna General Hospital, University of Vienna.
J Am Soc Echocardiogr. 2003 Sep;16(9):949-57. doi: 10.1016/S0894-7317(03)00477-2.
Because hibernation is considered a down-regulation of contractile function in response to reduced regional myocardial perfusion, hibernating myocardium is expected to be supplied by a critically stenosed or even occluded coronary artery. Thus, high-dose dobutamine has been postulated to cause ischemia and reworsening of myocardial function (biphasic response), whereas myocardium that demonstrates sustained improvement with high-dose dobutamine should not be supplied by a significantly stenosed vessel. This study evaluates the type of dobutamine response-biphasic versus sustained improvement-of dyssynergic myocardium in relation to its angiographically documented blood supply.
In 38 patients (5 women; mean age 60 +/- 9 years) with chronic coronary artery disease and impaired left ventricular ejection fraction (</=35%), dobutamine echocardiography and quantitative coronary angiography were performed within 4 weeks. Wall-motion response of dyssynergic myocardium to dobutamine, classified as no improvement, biphasic response, or sustained improvement, was compared with the angiographically documented blood supply (presence of coronary stenosis in the corresponding artery, collaterals, and stenoses of the collateral supplying artery) in a segment-by-segment analysis.
Of the 465 segments with abnormal wall motion at rest, 201 (47%) showed improvement during dobutamine infusion at low dose. Of these, 145 (72%) were supplied by significantly stenosed epicardial vessels. Only 27 (19%) of these 145 segments showed a biphasic response whereas in the remaining 118 segments wall-motion improvement persisted during high-dose dobutamine infusion. Although mean stenosis severity in the supplying vessel was significantly greater for segments presenting with biphasic response as compared with sustained improvement (95 +/- 7% and 86 +/- 12% luminal diameter reduction, respectively; P <.0001), 69% of segments with sustained improvement were supplied by a critically stenosed artery. Only 7 of 27 segments with biphasic response and 22 of 118 segments with sustained improvement had visible collaterals supplied by a vessel without significant stenosis. The percentage of segments viable by thallium-single photon emission computed tomography imaging was similar for those with sustained and biphasic response (96% and 83%, respectively).
In this group of patients with coronary artery disease and impaired left ventricular function, the great majority of dyssynergic segments that exhibited a sustained, rather than biphasic, dobutamine response were supplied by a critically stenosed artery. Furthermore, the percentage of segments viable by thallium-single photon emission computed tomography did not appear to be different for segments with sustained improvement and those with biphasic response. These findings challenge the hypothesis that biphasic response is the best criterion to identify viable myocardium.
由于冬眠被认为是心肌收缩功能因局部心肌灌注减少而出现的下调，因此预计冬眠心肌由严重狭窄甚至闭塞的冠状动脉供血。因此，有人推测高剂量多巴酚丁胺会导致缺血并使心肌功能恶化（双相反应），而高剂量多巴酚丁胺治疗后显示持续改善的心肌不应由严重狭窄的血管供血。本研究评估了运动失调心肌多巴酚丁胺反应的类型（双相反应与持续改善）与其血管造影记录的血供之间的关系。
对38例（5例女性；平均年龄60±9岁）患有慢性冠状动脉疾病且左心室射血分数受损（≤35%）的患者，在4周内进行了多巴酚丁胺超声心动图检查和定量冠状动脉造影。在逐段分析中，将运动失调心肌对多巴酚丁胺的壁运动反应（分为无改善、双相反应或持续改善）与血管造影记录的血供（相应动脉的冠状动脉狭窄情况、侧支循环以及侧支供血动脉的狭窄情况）进行比较。
在静息时壁运动异常的465个节段中，201个（47%）在低剂量多巴酚丁胺输注期间显示改善。其中，145个（72%）由严重狭窄的心外膜血管供血。这145个节段中只有27个（19%）显示双相反应，而其余118个节段在高剂量多巴酚丁胺输注期间壁运动持续改善。尽管与持续改善的节段相比，出现双相反应的节段供血血管的平均狭窄严重程度明显更高（管腔直径减少分别为95±7%和86±12%；P<.0001），但持续改善的节段中有69%由严重狭窄的动脉供血。双相反应的27个节段中只有7个以及持续改善的118个节段中有22个有由无明显狭窄的血管供应的可见侧支循环。铊单光子发射计算机断层扫描成像显示存活的节段百分比在持续反应和双相反应的节段中相似（分别为96%和83%）。
在这组患有冠状动脉疾病和左心室功能受损的患者中，绝大多数表现为持续而非双相多巴酚丁胺反应的运动失调节段由严重狭窄的动脉供血。此外，铊单光子发射计算机断层扫描显示存活的节段百分比在持续改善的节段和双相反应的节段中似乎没有差异。这些发现对双相反应是识别存活心肌的最佳标准这一假设提出了挑战。
