McVie J G
J Clin Pathol. 1970 Apr;23(3):203-9. doi: 10.1136/jcp.23.3.203.
Two methods of detecting early inapparent myocardial infarcts have been studied and their value in diagnostic practice compared. The better method proved to be the determination of the potassium to sodium ratio (ionic ratio) which falls in infarcted tissue within minutes of the onset of anoxia. The second method was nitro blue tetrazolium staining of gross sections of myocardium which revealed any infarct older than three and a half hours. As staining is dependent upon enzyme activity, the latter method is disturbed by autolysis. It was shown, on the other hand, that the ionic ratio (K(+)/Na(+)) was not affected by autolysis and was therefore well suited to forensic practice. Sixteen non-infarcted control hearts, plus the nine from cases of sudden death due to causes other than myocardial infarction, all yielded high ionic ratios (K(+)/Na(+)), average 1.4, and stained normally with tetrazolium (the normal controls). Positive control was provided by 20 histologically proven infarcts of which the ionic ratios (K(+)/Na(+)) were all low (average 0.7). Histochemical staining with tetrazolium delineated infarcted areas in each case. In a series of 29 sudden deaths, a cause of death other than myocardial infarction was found at necropsy in nine, mentioned above as normal controls. The remaining 20 hearts were not infarcted histologically, but were shown to be infarcted by examination of the ionic ratios (K(+)/Na(+)). These ratios were low (average 0.8) including three borderline ratios. Confirmatory evidence of infarction included nitro blue tetrazolium staining which revealed infarcts in 10 of the 20 cases, and clinical and necropsy observations. The ionic ratio (K(+)/Na(+)) decreases as the age of the infarct increases for at least 24 hours. Thereafter as healing proceeds, the ratio gradually reverts to normal. Thus, previous infarction and replacement fibrosis do not significantly alter the ionic ratio (K(+)/Na(+)). Nor is it changed by left ventricular hypertrophy, the presence of congestive cardiac failure, or digitalis therapy. It is suggested that macroscopic tetrazolium staining is a useful screening test for early inapparent myocardial infarcts. In cases where no infarct is delineated with that method estimation of the ionic ratio (K(+)/Na(+)) should be carried out on myocardium removed from standard areas on the anterior and posterior left ventricular walls.
研究了两种检测早期隐匿性心肌梗死的方法，并比较了它们在诊断实践中的价值。结果证明，较好的方法是测定钾钠比（离子比），该比值在缺氧开始后几分钟内就在梗死组织中下降。第二种方法是对心肌大体切片进行硝基蓝四氮唑染色，该方法可显示出任何超过三个半小时的梗死灶。由于染色依赖于酶活性，后一种方法会受到自溶的干扰。另一方面，研究表明离子比（K(+)/Na(+)）不受自溶影响，因此非常适合法医实践。16个未梗死的对照心脏，加上9个因心肌梗死以外原因猝死病例的心脏，离子比（K(+)/Na(+)）均较高，平均为1.4，四氮唑染色正常（正常对照）。20个经组织学证实的梗死心脏提供了阳性对照，其离子比（K(+)/Na(+)）均较低（平均0.7）。四氮唑组织化学染色在每个病例中都勾勒出了梗死区域。在一系列29例猝死病例中，尸检发现9例死亡原因并非心肌梗死，上述病例作为正常对照。其余20个心脏组织学上未梗死，但通过检测离子比（K(+)/Na(+)）显示为梗死。这些比值较低（平均0.8），包括三个临界比值。梗死的确诊证据包括硝基蓝四氮唑染色，该染色在20例病例中的10例中显示有梗死灶，以及临床和尸检观察结果。离子比（K(+)/Na(+)）至少在24小时内随梗死时间的延长而降低。此后，随着愈合过程的进行，该比值逐渐恢复正常。因此，既往梗死和替代性纤维化不会显著改变离子比（K(+)/Na(+)）。左心室肥厚、充血性心力衰竭的存在或洋地黄治疗也不会改变该比值。建议宏观四氮唑染色是检测早期隐匿性心肌梗死的一种有用的筛查试验。在该方法未显示梗死灶的病例中，应在左心室前壁和后壁标准区域取下的心肌上进行离子比（K(+)/Na(+)）的测定。
