Aarnoudse Wilbert, Fearon William F, Manoharan Ganesh, Geven Maartje, van de Vosse Frans, Rutten Marcel, De Bruyne Bernard, Pijls Nico H J
Department of Cardiology, Catharina Hospital Eindhoven, Eindhoven, The Netherlands.
Circulation. 2004 Oct 12;110(15):2137-42. doi: 10.1161/01.CIR.0000143893.18451.0E. Epub 2004 Oct 4.
Whether minimal microvascular resistance of the myocardium is affected by the presence of an epicardial stenosis is controversial. Recently, an index of microcirculatory resistance (IMR) was developed that is based on combined measurements of distal coronary pressure and thermodilution-derived mean transit time. In normal coronary arteries, IMR correlates well with true microvascular resistance. However, to be applicable in the case of an epicardial stenosis, IMR should account for collateral flow. We investigated the feasibility of determining IMR in humans and tested the hypothesis that microvascular resistance is independent of epicardial stenosis.
Thirty patients scheduled for percutaneous coronary intervention were studied. The stenosis was stented with a pressure guidewire, and coronary wedge pressure (P(w)) was measured during balloon occlusion. After successful stenting, a short compliant balloon with a diameter 1.0 mm smaller than the stent was placed in the stented segment and inflated with increasing pressures, creating a 10%, 50%, and 75% area stenosis. At each of the 3 degrees of stenosis, fractional flow reserve (FFR) and IMR were measured at steady-state maximum hyperemia induced by intravenous adenosine. A total of 90 measurements were performed in 30 patients. When uncorrected for P(w), an apparent increase in microvascular resistance was observed with increasing stenosis severity (IMR=24, 27, and 37 U for the 3 different degrees of stenosis; P<0.001). In contrast, when P(w) is appropriately accounted for, microvascular resistance did not change with stenosis severity (IMR=22, 23, and 23 U, respectively; P=0.28).
Minimal microvascular resistance does not change with epicardial stenosis severity, and IMR is a specific index of microvascular resistance when collateral flow is properly taken into account.
心肌最小微血管阻力是否受心外膜狭窄的影响存在争议。最近，基于冠状动脉远端压力和热稀释法测得的平均通过时间的联合测量，开发了一种微循环阻力指数（IMR）。在正常冠状动脉中，IMR与真正的微血管阻力密切相关。然而，为了适用于心外膜狭窄的情况，IMR应考虑侧支血流。我们研究了在人体中测定IMR的可行性，并检验了微血管阻力独立于心外膜狭窄的假设。
对30例计划进行经皮冠状动脉介入治疗的患者进行了研究。使用压力导丝对狭窄部位进行支架置入，并在球囊闭塞期间测量冠状动脉楔压（P(w)）。成功置入支架后，将直径比支架小1.0 mm的短顺应性球囊置于支架段，并逐渐增加压力使其膨胀，造成10%、50%和75%的面积狭窄。在这3种狭窄程度下，分别在静脉注射腺苷诱导的稳态最大充血时测量血流储备分数（FFR）和IMR。30例患者共进行了90次测量。当未校正P(w)时，随着狭窄程度的增加，微血管阻力明显增加（3种不同狭窄程度下的IMR分别为24、27和37 U；P<0.001）。相比之下，当适当考虑P(w)时，微血管阻力并不随狭窄程度而改变（IMR分别为22、23和23 U；P=0.28）。
最小微血管阻力不随心外膜狭窄程度而改变，当适当考虑侧支血流时，IMR是微血管阻力的一个特异性指标。
