Oreto G, Luzza F, Donato A, Satullo G, Calabrò M P, Consolo A, Arrigo F
Università di Messina, Istituto Pluridisciplinare di Clinica Medica, Italy.
Eur Heart J. 1992 May;13(5):634-7. doi: 10.1093/oxfordjournals.eurheartj.a060227.
The electrical resistivity of intracardiac blood is less than the resistivity of the surrounding tissues. This affects the transmission of cardiac forces to the body surface: the radial forces are enhanced, whereas the transmission of tangential forces is diminished (the Brody effect). Blood resistivity is directly related to haematocrit, hence, haematocrit changes are expected to affect the transmission of cardiac forces, resulting in changes in QRS complex voltage. To assess this hypothesis, a 12-lead electrocardiogram was recorded in 40 patients affected by thalassaemia before and after a transfusion of concentrated red cells. The voltage of each QRS component was carefully measured in every lead, and the sum of all R wave amplitudes (sigma R) was calculated. The post-transfusional electrocardiogram reflected a significant decrease in the R wave amplitude in every lead. sigma R also decreased, whereas S wave amplitude in lead V6 increased. A negative correlation between the ratio of haematocrit pre/post transfusion and that of the corresponding sigma R values was also observed (r = -0.434; P less than 0.01). An increase in haematocrit is therefore associated with a decrease in R wave amplitude. These findings explain why several patients with high haematocrit manifest relatively low voltage QRS complexes.
心腔内血液的电阻率低于周围组织的电阻率。这会影响心脏力量向体表的传导：径向力增强，而切向力的传导减弱（布罗迪效应）。血液电阻率与血细胞比容直接相关，因此，预计血细胞比容的变化会影响心脏力量的传导，导致QRS波群电压发生变化。为了评估这一假设，对40例地中海贫血患者在输注浓缩红细胞前后进行了12导联心电图记录。仔细测量每导联中每个QRS波成分的电压，并计算所有R波振幅之和（σR）。输血后的心电图显示每导联R波振幅显著降低。σR也降低，而V6导联的S波振幅增加。还观察到输血前后血细胞比容比值与相应的σR值比值之间呈负相关（r = -0.434；P<0.01）。因此，血细胞比容升高与R波振幅降低有关。这些发现解释了为什么一些血细胞比容高的患者表现出相对低电压的QRS波群。
