Toshiharu Niki

Prominent anterior QRS force as a manifestation of left septal fascicular block

Summary In the examination of 1,000 consecutive VCG records, prominent anterior QRS force (PAF) was frequently observed in ischemic heart disease, diabetes mellitus and hypertrophic cardiomyopathy not combined with high posterior infarction or right ventricular hypetrophy. PAF was observed especially in higher incidence in angina pectoris, papillary muscle dysfunction and hypertrophic cardiomyopathy. In a case of papillary muscle dysfunction who died suddenly, the septal fascicle of the left bundle was found to be markedly fibrotic by serial histological examination of the intraventricular conduction system. A case of angina pectoris with PAF later developed anteroseptal myocardial infarction. Ischemia of the anterior wall of the left ventricle might cause prominence or absence of the anterior QRS force in VCG. The prominence may be explained by left septal fascicular block, and the absence may be caused by the loss of the electromotive forces of the heart due to myocardial necrosis. Intermittent PAF was also observed, which was an important finding to support the existence of this new type of fascicular block. Left septal fascicular block should be considered as a type of conduction disturbance of the division of the left bundle in addition to the well-known left anterior or posterior hemiblock.

Comparison of the subunit compositions and ATPase activities of myosin in the myocardium and conduction system

The light chains and ATPase activities of specialized and ordinary muscle myosin from bovine heart were compared. The specialized heart muscle was composed of the A-V node, bundle of His, and right and left bundle branches. The yield of myosin from the specialized heart muscle was approximately 20% of that from the ordinary heart muscle. On sodium dodecyl sulfate (SDS)-polyacrylamide gel (10%) electrophoresis, ordinary heart myosin gave two bands of low molecular weight (light chains) as reported previously, whereas specialized heart myosin gave three bands. By comparison of the electrophoretic mobilities of these light chains with those of proteins of known molecular weight, the molecular weights of the two myosin light chains from ordinary heart muscle were estimated as 25 000 (LC1) and 18 000 (LC2), and those of the three bands of specialized heart myosin as 25 000 (LC1), 22 500 (LC1′) and 18 000 (LC2). There was approximately 3.5 mol of myosin light chains/mol of myosin in both tissue (Ordinary heart muscle: LC1 1.7 mol, LC2 1.8 mol; Specialized heart muscle: LC1 0.9 mol, LC1′ 1.1 mol, LC2 1.5 mol). The specific activities of myosin K+-EDTA- and Ca2+-activated ATPase (Vmax values in μmol phosphate/mg/min) in the two types of heart myosin were similar. These results suggest the existence of a new type of cardiac myosin isoenzyme in specialized heart muscle.

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.

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.