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The effect of brief hyperventilation on the precordial T waves of 350 normal adults is described. Evidence is presented that brief hyperventilation initiates a vagal reflex which results in the T-wave inversion. Supportive data are also given to exclude respiratory alkalosis as a possible mechanism. Caution is advised in interpreting isolated T-wave inversions as indicative of organic heart disease. It is proposed that isolated T-wave inversion be deleted as a criterion for a "positive" exercise test.

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The clinical applicability of the routine electrocardiogram and the chest roentgenogram in assessing advanced pulmonary emphysema is shown by a correlative study on 150 adults with moderately severe and severe pulmonary emphysema determined by pulmonary function studies. From these data a rather uniform electrocardiographic pattern has emerged entitled "the electrocardiographic pentalogy of pulmonary emphysema" which by itself suggests the presence of an advanced emphysematous state.A previous publication' established the ,&-,Lpresence of exaggerated P waves and resultant T-a wave inscription ill leads II, III, and aVF of the adult electrocardiogram in patients with severe emphysema. Continued focus upon the electrocardiogram of patients with advanced pulmonary emphysema has resulted in the identification of an electrocardiographic pattern which, by itself, suggests the presence of an advanced emphysematous state. This pattern will be referred to as the "electrocardiographic pentalogy of pulmonary emphysema; " it consists of (1) exaggerated P waves in leads II, III, and aVF, (2) prominent T-a waves in leads II, III, and aVF, (3) vertical cardiac position, which at times may be extreme, (4) MATERIALS AND METHODSOne hundred and fifty emphysemnatous adult patients were selected for study on whom 1 or more routine electrocardiograms and chest roentgenograms were available. All patients had moderately severe or severe pulmonary emphysema as established by pulmonary function tests.2 The arbitrary classification based on alteration of function is shown on table 1.The routine 12-lead electrocardiogram was classified into 6 groups according to the presenting pattern, namely, (1) the electrocardiographic pentalogy of pulmonary emphysema, as previously outlined, (2) the partial pentalogy, in which the degree of clockwise rotation and low voltage across the left precordium was less marked, (3) absent T-a-wave patterns, with marked degrees of vertical position, clockwise rotation, and low voltage, (4) the pattern of the short P-R interval and depressed RST segment, with vertical cardiac position, variable degrees of clockwise rotation, and left ventricular low voltage, which has previously been described,' (5) instances of right ventricular preponderance, patterns of right ventricular dilatation and patterns of right bundle-branch block, and (6) essentially normal electrocardiograms. Included in groups I and II are 9 instances of unusual cardiac axis presentation that superficially suggest left axis deviation but, in fact, are expressions of severe vertical position.

A simple, rapid, and reliable determination of plasma digitoxin levels is now available for clinical use. It can be determined in any clinical laboratory capable of determining a serum phosphorus if ATPase enzyme is available. Maintenance plasma levels range between 10 and 40 mµg/ml with a mean value of 25 mµg/ml. There is overlapping of maintenance and toxic serum levels in the higher ranges. Values over 45 mµg/ml warrant careful evaluation for digitalis intoxication. Maintenance plasma levels can be achieved with or without the usual digitalizing dosage if time is not a factor. The daily regression rate is variable in cases of digitalis intoxication following drug withdrawal. ECG changes (the degree of ST-segment depression, PR-interval prolongation, and multifocal premature contractions) were not good criteria for digitalis intoxication, although PR intervals above 0.24 sec consistently correlated with high plasma digitoxin levels. Variable second and third degree A-V block associated with mental confusion was a frequent presenting feature of digitalis toxicity.