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In a study of 45 cases of ventricular pre-excitation, 19 were classified as type A and 20 as type B according to Rosenbaum's criteria, which depend on the polarity of the major deflections in the right praecordial leads and not, as is commonly thought, on the direction of the delta vector. Six cases that could not be classified as type A or type B were termed intermediate. Vectorcardiograms were recorded from 29, and these showed a wide but continuous range of values for both the delta and the main QRS vectors in all three planes. Any classification based on these features must, therefore, depend on arbitrary quantitative data. Three patients in this series had associated right bundle-branch block. A review of the published reports on the association of pre-excitation and bundle-branch block failed to provide a rational basis for the classification of pre-excitation. It is emphasized that Rosenbaum's classification is empirical and its validity is questioned.

A prospective study was made of 80 patients during typical clinical episodes of acute myocardial infarction with biochemical and scalar electrocardiographic confirmation. Nine patients had bundle-branch block and 12 had had previous episodes of myocardial infarction. Serial electrocardiograms and vectorcardiograms were recorded during the first week in hospital. The most striking finding was that in more than half the cases there was disagreement between the electrocardiogram and vectorcardiogram in the localizationof infarction. The earliest evidence of infarction in the electrocardiogram is often restricted to ST and T changes though in the corresponding vectorcardiograms evidence of infarction may be present in the QRS loop. In those cases in which both electrocardiogram and vectorcardiogram show QRS abnormalities these are frequently detected earlier in the vectorcardiogram, but the converse is rare.