title: Left axis deviation: a reassessment.
abstract: This report deals with the ramifications of the concept of left axis deviation. In early life, the leftward shift of the frontal plane QRS axis is determined chiefly, if not solely, by the relative weights of the ventricles. Once adult ventricular weight ratios are reached, there is a long period of axis stability, then a gradual leftward drift of the QRS, governed principally by left anterior fascicular conduction. Thus, the normal QRS axis is age-dependent, and left axis deviation must be considered accordingly.
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging; D001283:Atrioventricular Node / Q000503:physiopathology; D002036:Bundle of His / Q000503:physiopathology; D002037:Bundle-Branch Block / Q000503:physiopathology; D006332:Cardiomegaly / Q000503:physiopathology; D009202:Cardiomyopathies / Q000503:physiopathology; D003327:Coronary Disease / Q000503:physiopathology; D004562:Electrocardiography; D004719:Endomyocardial Fibrosis / Q000503:physiopathology; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006330:Heart Defects, Congenital / Q000503:physiopathology; D006331:Heart Diseases / Q000503:physiopathology*; D006801:Humans; D006947:Hyperkalemia / Q000503:physiopathology; D007223:Infant; D007231:Infant, Newborn; D007738:Kyphosis / Q000503:physiopathology; D008875:Middle Aged; D009203:Myocardial Infarction / Q000150:complications / Q000503:physiopathology; D011247:Pregnancy; D011656:Pulmonary Emphysema / Q000503:physiopathology; D012600:Scoliosis / Q000503:physiopathology; D013008:Somatotypes