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Interpretation of findings using Holter ECG recordings
Letters to the Editor
Interpretation of findings using Holter ECG recordings To the Editor: Holter recording has become a valuable part of the physician's armamentarium in the clinical diagnosis, evaluation, and management of patients. But, as noted with previous new or innovative diagnostic methods, its results can best be correctly interpreted only when baseline observations of both healthy and diseased populations using the new method have been established. As a result of the relative lack of such baseline Holter recording electrocardiographic observations, the danger of misinterpretation or overinterpretation of Holter recording studies of inhomogeueous populations without appropriate controls is greater. Such factors seem to be operative (at least in part) in the clinical report entitled "Incidence of arrhythmias and ST-segment changes in elderly patients during barium enema studies" (AM. HEART J. 90:688, 1975). The authors examined a group of 58 hospitalized patients, all over the age of 60 years, with a standard 12-lead electrocardiogram, a resting 100 cycle rhythm strip (presumably 1 to 2 minutes), and then during a barium enema examination with Holter recording (indicated by the text as usually 10 to 45 minutes). Aspects of the study which warrant consideration prior to interpretation of the data include the control observations and the patients studied. It has been previously recognized~-~ that Holter recordings (long or short duration) are a more sensitive method of detecting electrocardiographic abnormality in various populations than either a standard 12-lead electrocardiogram or a two-minute electrocardiographic rhythm strip. Therefore it is not surprising t h a t "new arrhythmias" (despite the relative stringent criteria cbosen) were detected by Holter recording during the barium enema examination when compared to control 12-lead electrocardiograms or a control resting 100 cycle rhythm strip, for these arrhythmias may have been detected with or without the barium enema. A more appropriate control for comparison might have included a Holter recording of the same patient without the variables being examined (dehydration, fear, systemic arterial pressure changes, and barium enema examination) with careful attention to maintain the same clinical status, time of examination, and medications. Even then, variability of cardiac dysrhythmia (day to day) would have to be considered. Thus to ascribe all of the arrhythmias of Fig. I to the incidence of new arrhythmias is both misleading and incorrect. Prevalence or the presence of cardiac dysrhythmia during barium enema examination was defined in this sample of hospitalized patients, not incidence or the risk of developing dysrhythmia during such an examination. These comments are especially pertinent when it is realized that the study population examined was 60 years old or older. Although reference observation data of cardiac dysrhythmia in various populations (healthy and diseased) have not been totally defined, early studies indicate that cardiac dysrhythmia increases with age, and as many as 81 per cent of one cohort of such men age
824
60 to 65 had ventricular arrhythmia detected b y Holter recording. 4 Thus a Holter recording examination of the selected patients even dm-ing usual activities would be expected to disclose appreciable cardiac dysrhythmia. Review of the authors' results in Table I indicates more "Positive ECG during barium enema" in the older age groups and suggests age, per se, was a factor in the findings. Whether such dysrhythmia in older persons is due to latent cardiac disease is unknown. Notwithstanding these comments, it is understandable how the authors and others (myself included) might expect the barium enema examination with its associated stresses to have a provocative or causal influence on cardiac dysrhythmia. This risk of new cardiac dysrhythmia (i.e., incidence), however, may be surprisingly small, for as the authors stated "the effect of evacuation of the barium and of distention of the colon had little influence on our results." Thus, although I agree with the summary remarks in some respects, the study did not clearly define the incidence of developing arrhythmias and significant ST-segment depression attributable to the barium enema examination, and clinicians should be cautious not to derive an especially ominous inference with regard to the effects of the barium enema examination on cardiac dysrhythmia.
Harold L. Kennedy, M.D. Department of Cardiovascular Services and Clinical Investigations U.S. Public Health Service Hospital 3100 Wyman Park Drive Baltimore, Md. 21211 Department of Social and Preventive Medicine University of Maryland
REFERENCES 1.
Crawford, M., O'Rourke, R. A., Ramakrishna, N., Henning, H., and Ross, J., Jr.: Comparative effectiveness of exercise testing and continuous monitoring for detecting arrhythmias in patients with previous myocardial infarction, Circulation 50:301, 1974. 2. Ryan, M., Lown, B., and Horn, H.: Comparison of ventricular ectopic activity during 24-hour monitoring and exercise testing in patients with coronary heart disease, N. Engl. J. Med. 292:224, 1975. 3. Poblete, P. F., Kennedy, H. L , Underhill, S. J., and Warbasse, J. R.: Incidence and detection of ventricular arrhythmia in ischemic heart disease, Clin. Res. 23:202, 1975. 4. Hinkle, L. E., Carver, S. T., and Argyras,'D. C.: The prognostic significance of ventricular premature complexes in healthy people and in people with coronary heart disease, Acta Cardiologica (Suppl.) 1 8:5, 1974.
Left axis deviation To the Editor: We were interested in the paper by Drs. Grayzel and Neyshaboori1 concerning the etiologic factors of left axis
June, 1976, Vol. 9I, No. 6
Interpretation of findings using Holter ECG recordings To the Editor: Holter recording has become a valuable part of the physician's armamentarium in the clinical diagnosis, evaluation, and management of patients. But, as noted with previous new or innovative diagnostic methods, its results can best be correctly interpreted only when baseline observations of both healthy and diseased populations using the new method have been established. As a result of the relative lack of such baseline Holter recording electrocardiographic observations, the danger of misinterpretation or overinterpretation of Holter recording studies of inhomogeueous populations without appropriate controls is greater. Such factors seem to be operative (at least in part) in the clinical report entitled "Incidence of arrhythmias and ST-segment changes in elderly patients during barium enema studies" (AM. HEART J. 90:688, 1975). The authors examined a group of 58 hospitalized patients, all over the age of 60 years, with a standard 12-lead electrocardiogram, a resting 100 cycle rhythm strip (presumably 1 to 2 minutes), and then during a barium enema examination with Holter recording (indicated by the text as usually 10 to 45 minutes). Aspects of the study which warrant consideration prior to interpretation of the data include the control observations and the patients studied. It has been previously recognized~-~ that Holter recordings (long or short duration) are a more sensitive method of detecting electrocardiographic abnormality in various populations than either a standard 12-lead electrocardiogram or a two-minute electrocardiographic rhythm strip. Therefore it is not surprising t h a t "new arrhythmias" (despite the relative stringent criteria cbosen) were detected by Holter recording during the barium enema examination when compared to control 12-lead electrocardiograms or a control resting 100 cycle rhythm strip, for these arrhythmias may have been detected with or without the barium enema. A more appropriate control for comparison might have included a Holter recording of the same patient without the variables being examined (dehydration, fear, systemic arterial pressure changes, and barium enema examination) with careful attention to maintain the same clinical status, time of examination, and medications. Even then, variability of cardiac dysrhythmia (day to day) would have to be considered. Thus to ascribe all of the arrhythmias of Fig. I to the incidence of new arrhythmias is both misleading and incorrect. Prevalence or the presence of cardiac dysrhythmia during barium enema examination was defined in this sample of hospitalized patients, not incidence or the risk of developing dysrhythmia during such an examination. These comments are especially pertinent when it is realized that the study population examined was 60 years old or older. Although reference observation data of cardiac dysrhythmia in various populations (healthy and diseased) have not been totally defined, early studies indicate that cardiac dysrhythmia increases with age, and as many as 81 per cent of one cohort of such men age
824
60 to 65 had ventricular arrhythmia detected b y Holter recording. 4 Thus a Holter recording examination of the selected patients even dm-ing usual activities would be expected to disclose appreciable cardiac dysrhythmia. Review of the authors' results in Table I indicates more "Positive ECG during barium enema" in the older age groups and suggests age, per se, was a factor in the findings. Whether such dysrhythmia in older persons is due to latent cardiac disease is unknown. Notwithstanding these comments, it is understandable how the authors and others (myself included) might expect the barium enema examination with its associated stresses to have a provocative or causal influence on cardiac dysrhythmia. This risk of new cardiac dysrhythmia (i.e., incidence), however, may be surprisingly small, for as the authors stated "the effect of evacuation of the barium and of distention of the colon had little influence on our results." Thus, although I agree with the summary remarks in some respects, the study did not clearly define the incidence of developing arrhythmias and significant ST-segment depression attributable to the barium enema examination, and clinicians should be cautious not to derive an especially ominous inference with regard to the effects of the barium enema examination on cardiac dysrhythmia.
Harold L. Kennedy, M.D. Department of Cardiovascular Services and Clinical Investigations U.S. Public Health Service Hospital 3100 Wyman Park Drive Baltimore, Md. 21211 Department of Social and Preventive Medicine University of Maryland
REFERENCES 1.
Crawford, M., O'Rourke, R. A., Ramakrishna, N., Henning, H., and Ross, J., Jr.: Comparative effectiveness of exercise testing and continuous monitoring for detecting arrhythmias in patients with previous myocardial infarction, Circulation 50:301, 1974. 2. Ryan, M., Lown, B., and Horn, H.: Comparison of ventricular ectopic activity during 24-hour monitoring and exercise testing in patients with coronary heart disease, N. Engl. J. Med. 292:224, 1975. 3. Poblete, P. F., Kennedy, H. L , Underhill, S. J., and Warbasse, J. R.: Incidence and detection of ventricular arrhythmia in ischemic heart disease, Clin. Res. 23:202, 1975. 4. Hinkle, L. E., Carver, S. T., and Argyras,'D. C.: The prognostic significance of ventricular premature complexes in healthy people and in people with coronary heart disease, Acta Cardiologica (Suppl.) 1 8:5, 1974.
Left axis deviation To the Editor: We were interested in the paper by Drs. Grayzel and Neyshaboori1 concerning the etiologic factors of left axis
June, 1976, Vol. 9I, No. 6