Functional importance of the left septal Purkinje network in the left ventricular conduction system

Changes of the activation sequence and vectorcardiogram (VCG) resulting from experimental block of specific sites of the left bundle branch were studied to determine the functional significance of the septal Purkinje network. Discrete block of the septal Purkinje network (11 dogs) resulted in slight delay of epicardial activation in the apical area. In lead Z of McFee system of VCG, the antero-posterior ratio was increased from 1.4 to 2.6, and the QRS loop tended to be displaced anteriorly. Discrete block of the left posterior division (9 dogs) resulted in slight delay of activation in the posterior basal area. Block of the left posterior division plus the septal Purkinje network (11 dogs) resulted in marked delay in activation of a wider area extending from the posterior basal area to the apical area. In lead X, the S wave became evident and the direction of the maximum QRS vector in the frontal plane showed significant right axis deviation. Discrete block of the left posterior division did not change the epicardial activation sequence or the direction of the maximum QRS vector, because there is extensive interconnection of the left ventricular conduction system. These results suggest that block of the septal Purkinje network itself may produce an electrocardiographic change and that this network may also be important in left anterior and posterior hemiblocks producing axis changes in the frontal plane of VCG.

Biochemical studies on energy metabolism in the conduction system of bovine heart

The conduction system of bovine heart was studied to clarify the characteristics of its energy metabolism. Results showed that its mitochondrial oxygen uptake was much lower than that of ordinary heart muscle with succinate as substrate but similar to that of ordinary heart muscle with glutamate + malate as substrate. The activity of succinate dehydrogenase was lower than that in ordinary heart muscle. The total activity of isozymes of lactate dehydrogenase was lower in the specialized heart muscle than in ordinary heart muscle. The main isozyme of lactate dehydrogenase in the specialized heart muscle was LDH 1 (H4). The cytoplasmic NAD+/NADH ratio as much higher in the specialized heart muscle than in ordinary heart muscle. These results suggest that in the specialized heart muscle energy is mainly derived from aerobic metabolism.

Studies on the QRS wave of the spatial magnitude electrocardiogram in ventricular septal defect

The QRS wave of the spatial magnitude electrocardiogram (ECG) was investigated in 86 cases of the ventricular septal defect (VSD). The relationship between the amplitude and the time interval of QRS wave of the spatial magnitude ECG and the various hemodynamic parameters obtained by the right heart catheterization and the defect area ascertained during the operations were evaluated.

Characteristics of energy metabolism in specialized muscle of bovine heart

Characterization of the energy metabolism pattern of the specialized heart muscle of bovine heart was studied in comparison with that of the ordinary heart muscle. Mitochondrial oxygen consumption of the specialized heart muscle was significantly lower than that of the ordinary heart muscle with succinate as the substrate. On the other hand, there was no significant difference in oxygen consumption between both heart muscles with glutamate + malate as the substrates. The activity levels of succinate dehydrogenase and lactate dehydrogenase were much lower than those of the ordinary heart muscle. The isozyme pattern of LDH of the specialized heart muscle consisted of one major component of LDH-1 (H4) and that of the ordinary heart muscle consisted of two major components of LDH-1 (H4) and LDH-2 (H3M). The ratio of NADH to NAD of the specialized heart muscle was remarkably lower than that of the ordinary heart muscle. These results indicate that the specialized heart muscle depends not only upon anaerobic metabolism but also upon aerobic metabolism for its energy supply.