Duarte I G, Shearer S T, MacDonald M J, Gott J P, Brown W M, Vinten-Johansen J, Guyton R A
Cardiothoracic Research Laboratory, Carlyle Fraser Heart Center, Emory University School of Medicine, Atlanta, Georgia 30365-2225, USA.
Ann Thorac Surg. 1998 Jun;65(6):1610-6. doi: 10.1016/s0003-4975(98)00241-0.
Tepid blood (TB) cardioplegia combines the improved rheologic characteristics and the augmented oxygen and substrate delivery of blood cardioplegia with the advantages of moderate hypothermia. In addition, the intramyocardial distribution of continuous TB cardioplegia may also be better than intermittent cold crystalloid (CC) cardioplegia. We sought to compare the distribution of TB and CC cardioplegia at varying infusion pressures.
In situ, isolated canine hearts were randomized to antegrade, continuous TB (28 degrees C, n = 8) or intermittent CC (n = 8) cardioplegia infused at 50, 75, and 100 mm Hg. The regional distribution of cardioplegia at each pressure was measured by 15-microm colored microspheres. Cardioplegia distribution was measured from three areas each of the right ventricle (inflow, outflow, and apex) and the left ventricle (anterior, lateral, and posterior). Left ventricular samples were subdivided into subepicardial, midmyocardial, and subendocardial.
Delivery of cardioplegia to all areas of the right and left ventricles showed a linear pressure-flow relationship over the range of pressures tested. Right ventricular distribution was two-thirds of that to the left ventricle, and left ventricular subepicardial distribution was approximately one half of subendocardial flow in both groups at all delivery pressures. However, the subendocardial to subepicardial ratio was significantly greater with TB cardioplegia than with CC cardioplegia. Transmural right ventricular cardioplegia flow was comparable in both groups. In contrast, left ventricular distribution of CC cardioplegia was greater than TB cardioplegia at all three pressures tested.
The pressure-flow relationship in both CC and TB cardioplegia is linear in both the right and left ventricular myocardium over clinically applicable delivery pressures. The distribution of cardioplegia to the right ventricle is not altered by increased pressure.
微温血（TB）心脏停搏液兼具血液心脏停搏液改善的流变学特性、增加的氧和底物输送以及中度低温的优势。此外，持续TB心脏停搏液的心肌内分布可能也优于间断冷晶体（CC）心脏停搏液。我们试图比较不同输注压力下TB和CC心脏停搏液的分布情况。
将原位分离的犬心随机分为顺行持续TB（28℃，n = 8）或间断CC（n = 8）心脏停搏液组，分别以50、75和100 mmHg的压力进行输注。通过15微米彩色微球测量各压力下心脏停搏液的区域分布。从右心室（流入、流出和心尖）和左心室（前壁、侧壁和后壁）的三个区域测量心脏停搏液分布。左心室样本再细分为心外膜下、心肌中层和心内膜下。
在测试的压力范围内，向左右心室所有区域输送心脏停搏液均呈现线性压力-流量关系。在所有输送压力下，右心室的分布是左心室的三分之二，两组左心室心外膜下分布约为心内膜下血流的一半。然而，TB心脏停搏液的心内膜下与心外膜下比值显著高于CC心脏停搏液。两组右心室跨壁心脏停搏液流量相当。相比之下，在所有测试的三个压力下，CC心脏停搏液的左心室分布均大于TB心脏停搏液。
在临床适用的输送压力范围内，CC和TB心脏停搏液在左右心室心肌中的压力-流量关系均为线性。压力增加不会改变心脏停搏液向右心室的分布。
