Stuart W. Rosner

The exercise electrocardiogram: Differences in interpretation: Report of a technical group on exercise electrocardiography

Abstract Exercise electrocardiography is a valuable clinical tool with which quantitative evaluations and comparisons are now being attempted in many fields of cardiovascular investigation. Among a series of studies by a technical group on exercise electrocardiography, an assessment was made of observer variation in the clinical interpretation of ST-T responses during and after exercise. Interobserver variation among 14 cardiologists was great; individually assigned frequencies of abnormal responses after exercise in a mixed sample of records ranged from 5 to 58 per cent. Disagreement was greater for the diagnosis made during than for that made after exercise. Introbserver variation was also so great that use of the same observer for all exercise electrocardiographic readings would not necessarily provide acceptable reliability. The chief factors in disagreement were the lack of defined criteria for interpretation, in particular uncertainty about the significance of J-point ST-T depression, and technical quality of the records. Observer agreement was substantially increased when records were coded by unambiguous criteria or when simple measurements were made of the ST-T response after exercise.

Computer analysis of the exercise electrocardiogram

Abstract A computer system has been developed to analyze the exercise electrocardiogram. Every 6 seconds the computer program searches for a region free of artifact and shifting baseline. Once a region is located, amplitudes are measured and corrected to a horizontal line. The measurements include Q, R and S wave amplitudes and durations, amplitudes along the ST-T wave for a duration equal to half the R-R interval, and four amplitudes preceding the QRS complex. The measurements from each time-block are printed with the elapsed time from onset of recording. A programmed computer compares each set of measurement values to a template for the occurrence of significant change. When a significant difference appears, the new measurements serve as the next template. This time-varying template method preserves the significant measurements for the physician. The accuracy of computer measurements and the features of speed and automatic function suggest the use of this system wherever the monitored electrocardiogram has clinical value.

Atrial Tachysystole with Block

Two patients are reported who demonstrated bouts of rapid atrial activity with associated AV block at times unrelated to the administration of digitalis. The criteria of Lown and Levine for the differentiation of PAT with block from atrial flutter are examined. The application of atrial rate in the region of the arbitrary borderline is not a useful criterion. Determination of P-wave direction in leads II and III cannot be made in the presence of an undulating baseline. Identification, when possible, is not sufficient evidence for distinguishing the two arrhythmias. The appearance of the baseline may not warrant the decisive weight commonly given to it. A combination of recording instrument characteristics, the appearance of atrial repolarization at critical rates, as well as subjective factors may explain the undulatory baseline rather than denote a special electrocardiographic entity. Alternation of the P-P cycle length in PAT with block occurs inconstantly and is not an intrinsic property of the arrhythmia. Digitalis, which has a vagal effect, may contribute to the presence of this [see figure in the PDF file] phenomenon. The occurrence of ventricular premature contractions, response to carotid sinus pressure, and the AV ratio are nonspecific findings. The mode of termination of the arrhythmia may also lack specificity. Restoration of sinus rhythm following potassium administration will be, at times, coincidental. Moreover, the successful outcome of such a therapeutic trial is evidence of digitalis intoxication not proof of a specific arrhythmia. Experimental and clinical evidence has firmly established that digitalis is capable of producing an atrial arrhythmia attended by AV block. This report does not contest the observation. A critical review of the contrasting features of atrial flutter and PAT with block and an analysis of the data in the present cases suggest that the electrocardiogram does not provide a means for the clear-cut separation of atrial tachycardia from flutter in certain cases and questions the existence of such a division. The term atrial tachysystole with block is offered as a designation for such tracings.

A computer program for computation and interpretation of pulmonary function data

Abstract The operation of a pulmonary function laboratory involves numerous computational procedures which are tedious and contribute significantly to the total time-expense of patient examination. Since the calculations are typically invariant, repetitive tasks, automatic computation is feasible. Automatic equation solving offers many benefits: precision, speed, the means of saving human time, and hence the opportunity for increased productivity. We have begun to investigate this field using a relatively small digital computer. Our previous work was concerned with use of a computer to analyze the expiratory and inspiratory spirogram, and resting and maximal voluntary ventilation (1–5). Analysis is accomplished by recording analog signals from the spirometer on magnetic tape for subsequent digitization and computer analysis. In our latest development, the measurements from these automatic analyses are used in conjunction with technician measurements to provide digital data for computer use.

Beat-to-beat variation in the split second heart sound

Abstract The respiratory variation of the split second heart sound was recorded for a series of consecutive beats in normal persons by using a high-frequency phonocardiographic technic. The component sounds were inscribed as discrete transients permitting the measurement of small time intervals from the onset of each. In some individuals, A 2 and P 2 were recorded as a composite of a series of clearly defined high frequency vibrations. Maximal splitting occurred during inspiration and resulted from the earlier occurrence of A 2 and delay in P 2 . The latter effect was predominant for the group, although the mechanism of widening and narrowing the split varied between individuals and between beats in a single individual. Hemodynamic events affecting closure of the aortic and pulmonic valves are discussed and attention is focused on the existing problem of the role of the lung on left heart venous return.

Atrial tachysystole with block

Two patients are reported who demonstrated bouts of rapid atrial activity with associated AV block at times unrelated to the administration of digitalis. The criteria of Lown and Levine for the differentiation of PAT with block from atrial flutter are examined. The application of atrial rate in the region of the arbitrary borderline is not a useful criterion. Determination of P-wave direction in leads II and III cannot be made in the presence of an undulating baseline. Identification, when possible, is not sufficient evidence for distinguishing the two arrhythmias. The appearance of the baseline may not warrant the decisive weight commonly given to it. A combination of recording instrument characteristics, the appearance of atrial repolarization at critical rates, as well as subjective factors may explain the undulatory baseline rather than denote a special electrocardiographic entity. Alternation of the P-P cycle length in PAT with block occurs inconstantly and is not an intrinsic property of the arrhythmia. Digitalis, which has a vagal effect, may contribute to the presence of this[see figure in the PDF file]phenomenon. The occurrence of ventricular premature contractions, response to carotid sinus pressure, and the AV ratio are nonspecific findings. The mode of termination of the arrhythmia may also lack specificity. Restoration of sinus rhythm following potassium administration will be, at times, coincidental. Moreover, the successful outcome of such a therapeutic trial is evidence of digitalis intoxication not proof of a specific arrhythmia.Experimental and clinical evidence has firmly established that digitalis is capable of producing an atrial arrhythmia attended by AV block. This report does not contest the observation. A critical review of the contrasting features of atrial flutter and PAT with block and an analysis of the data in the present cases suggest that the electrocardiogram does not provide a means for the clear-cut separation of atrial tachycardia from flutter in certain cases and questions the existence of such a division. The term atrial tachysystole with block is offered as a designation for such tracings.