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Papers by David Mortara
significantly during the session. The agreement between ECG-based potassium estimator and the ref... more significantly during the session. The agreement between ECG-based potassium estimator and the reference potassium measurements was good (absolute error: 0.49±0.16 mM) for most of the sessions (30/39) except for 9 (absolute error: 1.17±0.36 mM) in which the presence of a systematic error all along the session did not allow reliable estimates. Bland-Altman analysis showed that the overall systematic error was almost null (-0.03 mM) whereas the standard deviation was 0.83 mM. The manual correction of the bias over each dialysis session resulted in excellent results for all patients. Preliminary results are promising although further investigation is required to understand the reason for session-dependent bias in some patients.
Journal of electrocardiology
A fraction of routine resting ECG's are taken with electrode positions interchanged, leading ... more A fraction of routine resting ECG's are taken with electrode positions interchanged, leading to possible clinical misinterpretation. Develop and test a method to detect and prevent electrode reversals at the electrocardiograph before the ECG is acquired. The algorithm is based on QRS axis and P amplitudes for limb electrode reversals, and P-Q-RS amplitude distances to detect chest electrode reversals. The evaluation method involved a large (>18,000) hospital database for which serial ECG's were available and was based on simulated juxtapositions. The 7 most common lead reversals could be detected with a specificity of 99.8% per type and an average sensitivity of 90%, excluding LA-LL reversal (22% sensitivity). Results are similar to retrospective studies that used smaller, more homogeneous datasets. The early warning system reduces the ECG's recorded with reversal by 80%, at the price of a modest false alert rate of 1.4%.
Journal of the American College of Cardiology, 2014
Maintenance of normal potassium homeostasis is increasingly an important limiting factor in the t... more Maintenance of normal potassium homeostasis is increasingly an important limiting factor in the therapy of several diseases including patients with heart failure. Nowadays, quantification of potassium concentration in the blood ([K + ]) is invasive and laboratory-based. The aims of the study were to develop a method quantifying [K + ] from the electrocardiogram (ECG) and validate it on 13 hemodialysis (HD) and 7 congenital long-QT type 2 (LQT2) patients. Reference values were obtained from blood samples. An ECG-based potassium estimator (K ECG ) was defined and compared to the reference values. Data from 33/39 HD sessions gave consistent results. In 6 sessions, the presence of a systematic error inhibited reliable estimates. Patient specific calibration allowed good agreement in all HD patients (error: -0.04±0.61mM). As expected, [K + ] was significantly underestimated in LQT2 patients (error: 1.24±0.75mM, p<0.01). Preliminary results show K ECG estimates can be an effective tool for hyper/hypokalemic risk patient monitoring at home.
Journal of Electrocardiology, 2014
Breathing is a critical component of cardiopulmonary function, but few tools exist to evaluate re... more Breathing is a critical component of cardiopulmonary function, but few tools exist to evaluate respiration in ambulatory patients. Holter monitoring allows accurate diagnosis of a host of cardiac issues, and several investigators have demonstrated the ability to detect respiratory effort on the electrocardiogram. In this study we introduce a myogram signal derived from 12-lead, high frequency Holter as a means of detecting respiratory effort. Using the combined myogram and ECG signal, four novel variables were created: total number of Cheyne-Stokes episodes; the BWRatio, the ratio of power (above baseline) measured one second after peak-to-peak respiratory power, an assessment of the &amp;amp;amp;amp;amp;quot;shape&amp;amp;amp;amp;amp;quot; of the respiratory effort; DRR, the change in RR interval centering around peak inspiration; and minutes of synchronized breathing, a fixed ratio of heart beats to respiratory cycles. These variables were assessed in 24-hour recordings from three cohorts: healthy volunteers (n=33), heart failure subjects from the GISSI HF trial (n=383), and subjects receiving implantable defibrillators with severely depressed left ventricular function enrolled in the M2Risk trial (n=470). We observed a statistically significant 6-fold increase in the number of Cheyne-Stokes episodes (p=0.01 by ANOVA), decreases in BWRatio (p&amp;amp;amp;amp;amp;lt;0.001), as well as decrease in DRR in heart failure subjects; only minutes of synchronized breathing was not significantly decreased in heart failure. This study provides &amp;amp;amp;amp;amp;quot;proof of concept&amp;amp;amp;amp;amp;quot; that novel variables incorporating Holter-derived respiration can distinguish healthy subjects from heart failure. The utility of these variables for predicting heart failure, arrhythmia, and death risk in prospective studies needs to be assessed.
Background The duration of the QT interval is only a gross estimate of repolarization. Besides it... more Background The duration of the QT interval is only a gross estimate of repolarization. Besides its limited accuracy and reproducibility, it does not provide information on the morphology of the T wave; thus, morphologic alterations such as notches can be only qualitatively described but not objectively quantified. Methods and Results To measure the complexity of repolarization in the long-QT syndrome
Journal of the American College of Cardiology, 1996
It !; wall known that dishomogeneous repoladzation is an~ythmogenio; however techniques to quanti... more It !; wall known that dishomogeneous repoladzation is an~ythmogenio; however techniques to quantify complexity of repolarization are scanty. Principal components analysis is a method to assess the degree of correlation between a family of wc, veforms. When applied to T waves, it defines the components of repofadzation. Usually, the first component a~:¢ounts for most of repolarization, whereas a dishomogeneous rapoladzatian is indicated by a relevant contribution of the second and other components. We applied principal component analysis to algorithmic, ally defined JT intervals in 491 ECG recordings obtained during 12-leeds Holler monitoring (Mortara inst.), in controls (ctrls;n = 8) and in Long QT Syndrome lots (LQTS:n = 13). A mean of 24 ± 3 ECG traces taken houdy during monitoring were used for each subject, The second/first component ratio (complexity) was 17 ± 5% in ntds and 41 ± 15=/o in LQTS (p < 0,001). Dynamic measurement of JT interval complexity showed that in LQT$ the 24 hra Standard Deviation of second component was much higher than in control individuals (3 vs 13=/o; p < 0.001 ). For L QT$, multiple regression analysis showed no correlation between complexity of T wave and QTc interval or QT¢ dispemion. These data show that principal component analysis identifies large dilferance3 between LQTS and ctrls. LQTS pts preeent a higher complexity of repoladzation and a larger circadian variability. This new index of dishomoganeity of vantricular repolarization is observer.independent and provides novel information not redundant with QT and QT dispersion.
Journal of the American College of Cardiology, 1984
... Training on Computer-Measured ST Segment Displacement in Patients With Coronary Artery Diseas... more ... Training on Computer-Measured ST Segment Displacement in Patients With Coronary Artery Disease JONATHAN MYERS, MA, STAFFAN AHNVE, MD, FACC, VICTOR FROELICHER, MD, FACC, MARTHA LIVINGSTON, RN , MA ... Kattus A, Jorgenson CR, Wordern RE, Alvaro AB ...
Journal of the American College of Cardiology, 1996
JACC Felmzaz~ 1996 ABSTRACTS ~ Poster 121A variations can be diseOclged by 244~0ur ECG recomtng~ ... more JACC Felmzaz~ 1996 ABSTRACTS ~ Poster 121A variations can be diseOclged by 244~0ur ECG recomtng~ VR vsdagons ms), be more informative than conventional QT Inte~al measurements to evaluate myooa~dig ~apolaJ~.a~en.
Journal of Electrocardiology, 1980
Studies based on analysis of QRS notching and slurring have suggested an increase in high frequen... more Studies based on analysis of QRS notching and slurring have suggested an increase in high frequency QRS potentials following myocardial infarction (MI). We investigated the sensitivity and specificity of an indirect, but easily quantitated index of high frequency potentials--the peak-to-peak amplitude of the high frequency signal. A commercially-available micro-processor ECG system was employed with a QRS-averaging program to reduce random noise and an 80-300 Hz filter to selectively record higher frequency potentials. High frequency ECGs were recorded in leads II, III and aVF in 40 normal men and 41 patients with prior inferior MI. Peak-to-peak amplitude of the high frequency signal was less than or equal to 35 micro V in one or more of these leads in 18 of 41 MI patients (44%) compared with only 1 of 40 normals (2.5%) (P < 0.001). In the infarct group, reduced peak amplitude of the high frequency signal was also noted in some leads where the standard ECG did not show pathologic Q waves. This diminution in peak amplitude probably reflects a reduction in high frequency voltage. Therefore, contrary to previous theory, MI may actually cause a decrease in high frequency potentials as part of an overall loss of electromotive force or a slowing of conduction associated with myocardial necrosis. Quantitative high frequency QRS measurements may be of critical value in selected cases.
Journal of Electrocardiology, 2002
1. J Electrocardiol. 2002;35 Suppl:207-30. The first ISCE Board of "Trustees" o... more 1. J Electrocardiol. 2002;35 Suppl:207-30. The first ISCE Board of "Trustees" overview panel session: ischemia monitoring, state of the art. International Society of Computerized Electrocardiology. Booker KJ, Drew BJ, Lux RL ...
Journal of Electrocardiology, 2011
Journal of Electrocardiology, Volume 44, Issue 2, Pages e2, March 2011, Authors:Cristiana Corsi; ... more Journal of Electrocardiology, Volume 44, Issue 2, Pages e2, March 2011, Authors:Cristiana Corsi; Stefano Severi; Mark Haigney; Johan De Bie; David Mortara. Journal Home, Register or Login: Password: Auto-Login [Reminder]. ...
American Heart Journal, 1998
The type of practitioners who use the standard exercise test is changing. Once a tool of the card... more The type of practitioners who use the standard exercise test is changing. Once a tool of the cardiologist, the standard exercise test is now being performed by internists and other noncardiologists. Because this change could be facilitated by computerization similar to the computerized interpretation programs available for the resting electrocardiograph (ECG), we performed this analysis. A secondary aim was to demonstrate the effects of medication status and resting ECG abnormalities on test diagnostic characteristics because these factors affect utility of the exercise test by the generalist. A retrospective analysis was performed of consecutive patients referred at 2 university-affiliated Veteran&amp;#39;s Affairs Medical Centers and a Hungarian Hospital for evaluation of chest pain and possible ischemic heart disease. There were 1384 consecutive male patients without a prior myocardial infarction with complete data who had exercise tests and coronary angiography between 1987 and 1997. Measurements included clinical, exercise test data, and visual interpretation of the ECG recordings as well as more than 100 computed measurements from the digitized ECG recordings and compilation of angiographic data from clinical reports. The computer measurements had similar diagnostic power compared with visual interpretation. Computerized measurements from maximal exercise or recovery were equivalent or superior to all other measurements. Prediction equations applied by computer were superior to single ECG measurements. Beta-blockers had no effect on test characteristics, whereas resting ST depression was associated with decreased specificity and increased sensitivity. Computerized exercise ST measurements are comparable to visual ST measurements by a cardiologist; computerized scores that included clinical and exercise test results exhibited the greatest diagnostic power. Applying scores with a computer allows the practicing physician to improve the diagnostic characteristics of the standard exercise test. This approach is successful even when there is resting ST depression, thus lessening the need for more expensive nuclear or imaging studies.
American Heart Journal, 2014
Automated measurements of electrocardiographic (ECG) intervals are widely used by clinicians for ... more Automated measurements of electrocardiographic (ECG) intervals are widely used by clinicians for individual patient diagnosis and by investigators in population studies. We examined whether clinically significant systematic differences exist in ECG intervals measured by current generation digital electrocardiographs from different manufacturers and whether differences, if present, are dependent on the degree of abnormality of the selected ECGs. Measurements of RR interval, PR interval, QRS duration, and QT interval were made blindly by 4 major manufacturers of digital electrocardiographs used in the United States from 600 XML files of ECG tracings stored in the US FDA ECG warehouse and released for the purpose of this study by the Cardiac Safety Research Consortium. Included were 3 groups based on expected QT interval and degree of repolarization abnormality, comprising 200 ECGs each from (1) placebo or baseline study period in normal subjects during thorough QT studies, (2) peak moxifloxacin effect in otherwise normal subjects during thorough QT studies, and (3) patients with genotyped variants of congenital long QT syndrome (LQTS). Differences of means between manufacturers were generally small in the normal and moxifloxacin subjects, but in the LQTS patients, differences of means ranged from 2.0 to 14.0 ms for QRS duration and from 0.8 to 18.1 ms for the QT interval. Mean absolute differences between algorithms were similar for QRS duration and QT intervals in the normal and in the moxifloxacin subjects (mean ≤6 ms) but were significantly larger in patients with LQTS. Small but statistically significant group differences in mean interval and duration measurements and means of individual absolute differences exist among automated algorithms of widely used, current generation digital electrocardiographs. Measurement differences, including QRS duration and the QT interval, are greatest for the most abnormal ECGs.
Clinical Neurophysiology, 2014
Autonomic dysfunction has been demonstrated in patients with rapid eye movement sleep behavior di... more Autonomic dysfunction has been demonstrated in patients with rapid eye movement sleep behavior disorder utilizing heart rate variability parameters. We hypothesized that isolated rapid eye movement sleep without atonia is similarly associated with autonomic dysfunction as demonstrated by a reduction in heart rate variability. An evaluation of 120 records demonstrating rapid eye movement sleep without atonia during polysomnography was performed. Many (n=99) were discarded owing to factors potentially affecting heart rate variability. The remaining 21 records were matched with 21 records of patients demonstrating normal REM atonia, and subjected to electrocardiogram analysis. The parameters measured included R to R interval (RR) length, RR standard deviation, heart rate variability power, and very low frequency, low frequency, and high frequency bands. Autonomic dysfunction was seen in patients with isolated rapid eye movement sleep without atonia as denoted by a reduction in heart rate variability compared to those with normal REM atonia. Significant differences between the groups were demonstrated in RR standard deviation (mean difference=0.1502±0.317, 95% confidence interval [95% CI]=0.006, 0.295, p=0.042), heart rate variability power (mean difference=0.3005±0.635, 95% CI=0.011, 0.589, p=0.042), and the low frequency band (mean difference=0.3166±0.616 ms(2), 95% CI=0.036, 0.597, p=0.029), and a borderline significant reduction in the high frequency band (mean difference=0.3121±0.686 ms(2), 95% CI=0.000, 0.624, p=0.050). Our data confirms the hypothesis that heart rate variability is reduced in patients with isolated rapid eye movement sleep without atonia. The values obtained are consistent with previous findings in rapid eye movement behavior sleep disorder patients. This is the first report of autonomic dysfunction in isolated rapid eye movement sleep without atonia, revealing the need for further evaluation of the clinical significance and potential implications of this finding.
significantly during the session. The agreement between ECG-based potassium estimator and the ref... more significantly during the session. The agreement between ECG-based potassium estimator and the reference potassium measurements was good (absolute error: 0.49±0.16 mM) for most of the sessions (30/39) except for 9 (absolute error: 1.17±0.36 mM) in which the presence of a systematic error all along the session did not allow reliable estimates. Bland-Altman analysis showed that the overall systematic error was almost null (-0.03 mM) whereas the standard deviation was 0.83 mM. The manual correction of the bias over each dialysis session resulted in excellent results for all patients. Preliminary results are promising although further investigation is required to understand the reason for session-dependent bias in some patients.
Journal of electrocardiology
A fraction of routine resting ECG's are taken with electrode positions interchanged, leading ... more A fraction of routine resting ECG's are taken with electrode positions interchanged, leading to possible clinical misinterpretation. Develop and test a method to detect and prevent electrode reversals at the electrocardiograph before the ECG is acquired. The algorithm is based on QRS axis and P amplitudes for limb electrode reversals, and P-Q-RS amplitude distances to detect chest electrode reversals. The evaluation method involved a large (>18,000) hospital database for which serial ECG's were available and was based on simulated juxtapositions. The 7 most common lead reversals could be detected with a specificity of 99.8% per type and an average sensitivity of 90%, excluding LA-LL reversal (22% sensitivity). Results are similar to retrospective studies that used smaller, more homogeneous datasets. The early warning system reduces the ECG's recorded with reversal by 80%, at the price of a modest false alert rate of 1.4%.
Journal of the American College of Cardiology, 2014
Maintenance of normal potassium homeostasis is increasingly an important limiting factor in the t... more Maintenance of normal potassium homeostasis is increasingly an important limiting factor in the therapy of several diseases including patients with heart failure. Nowadays, quantification of potassium concentration in the blood ([K + ]) is invasive and laboratory-based. The aims of the study were to develop a method quantifying [K + ] from the electrocardiogram (ECG) and validate it on 13 hemodialysis (HD) and 7 congenital long-QT type 2 (LQT2) patients. Reference values were obtained from blood samples. An ECG-based potassium estimator (K ECG ) was defined and compared to the reference values. Data from 33/39 HD sessions gave consistent results. In 6 sessions, the presence of a systematic error inhibited reliable estimates. Patient specific calibration allowed good agreement in all HD patients (error: -0.04±0.61mM). As expected, [K + ] was significantly underestimated in LQT2 patients (error: 1.24±0.75mM, p<0.01). Preliminary results show K ECG estimates can be an effective tool for hyper/hypokalemic risk patient monitoring at home.
Journal of Electrocardiology, 2014
Breathing is a critical component of cardiopulmonary function, but few tools exist to evaluate re... more Breathing is a critical component of cardiopulmonary function, but few tools exist to evaluate respiration in ambulatory patients. Holter monitoring allows accurate diagnosis of a host of cardiac issues, and several investigators have demonstrated the ability to detect respiratory effort on the electrocardiogram. In this study we introduce a myogram signal derived from 12-lead, high frequency Holter as a means of detecting respiratory effort. Using the combined myogram and ECG signal, four novel variables were created: total number of Cheyne-Stokes episodes; the BWRatio, the ratio of power (above baseline) measured one second after peak-to-peak respiratory power, an assessment of the &amp;amp;amp;amp;amp;quot;shape&amp;amp;amp;amp;amp;quot; of the respiratory effort; DRR, the change in RR interval centering around peak inspiration; and minutes of synchronized breathing, a fixed ratio of heart beats to respiratory cycles. These variables were assessed in 24-hour recordings from three cohorts: healthy volunteers (n=33), heart failure subjects from the GISSI HF trial (n=383), and subjects receiving implantable defibrillators with severely depressed left ventricular function enrolled in the M2Risk trial (n=470). We observed a statistically significant 6-fold increase in the number of Cheyne-Stokes episodes (p=0.01 by ANOVA), decreases in BWRatio (p&amp;amp;amp;amp;amp;lt;0.001), as well as decrease in DRR in heart failure subjects; only minutes of synchronized breathing was not significantly decreased in heart failure. This study provides &amp;amp;amp;amp;amp;quot;proof of concept&amp;amp;amp;amp;amp;quot; that novel variables incorporating Holter-derived respiration can distinguish healthy subjects from heart failure. The utility of these variables for predicting heart failure, arrhythmia, and death risk in prospective studies needs to be assessed.
Background The duration of the QT interval is only a gross estimate of repolarization. Besides it... more Background The duration of the QT interval is only a gross estimate of repolarization. Besides its limited accuracy and reproducibility, it does not provide information on the morphology of the T wave; thus, morphologic alterations such as notches can be only qualitatively described but not objectively quantified. Methods and Results To measure the complexity of repolarization in the long-QT syndrome
Journal of the American College of Cardiology, 1996
It !; wall known that dishomogeneous repoladzation is an~ythmogenio; however techniques to quanti... more It !; wall known that dishomogeneous repoladzation is an~ythmogenio; however techniques to quantify complexity of repolarization are scanty. Principal components analysis is a method to assess the degree of correlation between a family of wc, veforms. When applied to T waves, it defines the components of repofadzation. Usually, the first component a~:¢ounts for most of repolarization, whereas a dishomogeneous rapoladzatian is indicated by a relevant contribution of the second and other components. We applied principal component analysis to algorithmic, ally defined JT intervals in 491 ECG recordings obtained during 12-leeds Holler monitoring (Mortara inst.), in controls (ctrls;n = 8) and in Long QT Syndrome lots (LQTS:n = 13). A mean of 24 ± 3 ECG traces taken houdy during monitoring were used for each subject, The second/first component ratio (complexity) was 17 ± 5% in ntds and 41 ± 15=/o in LQTS (p < 0,001). Dynamic measurement of JT interval complexity showed that in LQT$ the 24 hra Standard Deviation of second component was much higher than in control individuals (3 vs 13=/o; p < 0.001 ). For L QT$, multiple regression analysis showed no correlation between complexity of T wave and QTc interval or QT¢ dispemion. These data show that principal component analysis identifies large dilferance3 between LQTS and ctrls. LQTS pts preeent a higher complexity of repoladzation and a larger circadian variability. This new index of dishomoganeity of vantricular repolarization is observer.independent and provides novel information not redundant with QT and QT dispersion.
Journal of the American College of Cardiology, 1984
... Training on Computer-Measured ST Segment Displacement in Patients With Coronary Artery Diseas... more ... Training on Computer-Measured ST Segment Displacement in Patients With Coronary Artery Disease JONATHAN MYERS, MA, STAFFAN AHNVE, MD, FACC, VICTOR FROELICHER, MD, FACC, MARTHA LIVINGSTON, RN , MA ... Kattus A, Jorgenson CR, Wordern RE, Alvaro AB ...
Journal of the American College of Cardiology, 1996
JACC Felmzaz~ 1996 ABSTRACTS ~ Poster 121A variations can be diseOclged by 244~0ur ECG recomtng~ ... more JACC Felmzaz~ 1996 ABSTRACTS ~ Poster 121A variations can be diseOclged by 244~0ur ECG recomtng~ VR vsdagons ms), be more informative than conventional QT Inte~al measurements to evaluate myooa~dig ~apolaJ~.a~en.
Journal of Electrocardiology, 1980
Studies based on analysis of QRS notching and slurring have suggested an increase in high frequen... more Studies based on analysis of QRS notching and slurring have suggested an increase in high frequency QRS potentials following myocardial infarction (MI). We investigated the sensitivity and specificity of an indirect, but easily quantitated index of high frequency potentials--the peak-to-peak amplitude of the high frequency signal. A commercially-available micro-processor ECG system was employed with a QRS-averaging program to reduce random noise and an 80-300 Hz filter to selectively record higher frequency potentials. High frequency ECGs were recorded in leads II, III and aVF in 40 normal men and 41 patients with prior inferior MI. Peak-to-peak amplitude of the high frequency signal was less than or equal to 35 micro V in one or more of these leads in 18 of 41 MI patients (44%) compared with only 1 of 40 normals (2.5%) (P < 0.001). In the infarct group, reduced peak amplitude of the high frequency signal was also noted in some leads where the standard ECG did not show pathologic Q waves. This diminution in peak amplitude probably reflects a reduction in high frequency voltage. Therefore, contrary to previous theory, MI may actually cause a decrease in high frequency potentials as part of an overall loss of electromotive force or a slowing of conduction associated with myocardial necrosis. Quantitative high frequency QRS measurements may be of critical value in selected cases.
Journal of Electrocardiology, 2002
1. J Electrocardiol. 2002;35 Suppl:207-30. The first ISCE Board of "Trustees" o... more 1. J Electrocardiol. 2002;35 Suppl:207-30. The first ISCE Board of "Trustees" overview panel session: ischemia monitoring, state of the art. International Society of Computerized Electrocardiology. Booker KJ, Drew BJ, Lux RL ...
Journal of Electrocardiology, 2011
Journal of Electrocardiology, Volume 44, Issue 2, Pages e2, March 2011, Authors:Cristiana Corsi; ... more Journal of Electrocardiology, Volume 44, Issue 2, Pages e2, March 2011, Authors:Cristiana Corsi; Stefano Severi; Mark Haigney; Johan De Bie; David Mortara. Journal Home, Register or Login: Password: Auto-Login [Reminder]. ...
American Heart Journal, 1998
The type of practitioners who use the standard exercise test is changing. Once a tool of the card... more The type of practitioners who use the standard exercise test is changing. Once a tool of the cardiologist, the standard exercise test is now being performed by internists and other noncardiologists. Because this change could be facilitated by computerization similar to the computerized interpretation programs available for the resting electrocardiograph (ECG), we performed this analysis. A secondary aim was to demonstrate the effects of medication status and resting ECG abnormalities on test diagnostic characteristics because these factors affect utility of the exercise test by the generalist. A retrospective analysis was performed of consecutive patients referred at 2 university-affiliated Veteran&amp;#39;s Affairs Medical Centers and a Hungarian Hospital for evaluation of chest pain and possible ischemic heart disease. There were 1384 consecutive male patients without a prior myocardial infarction with complete data who had exercise tests and coronary angiography between 1987 and 1997. Measurements included clinical, exercise test data, and visual interpretation of the ECG recordings as well as more than 100 computed measurements from the digitized ECG recordings and compilation of angiographic data from clinical reports. The computer measurements had similar diagnostic power compared with visual interpretation. Computerized measurements from maximal exercise or recovery were equivalent or superior to all other measurements. Prediction equations applied by computer were superior to single ECG measurements. Beta-blockers had no effect on test characteristics, whereas resting ST depression was associated with decreased specificity and increased sensitivity. Computerized exercise ST measurements are comparable to visual ST measurements by a cardiologist; computerized scores that included clinical and exercise test results exhibited the greatest diagnostic power. Applying scores with a computer allows the practicing physician to improve the diagnostic characteristics of the standard exercise test. This approach is successful even when there is resting ST depression, thus lessening the need for more expensive nuclear or imaging studies.
American Heart Journal, 2014
Automated measurements of electrocardiographic (ECG) intervals are widely used by clinicians for ... more Automated measurements of electrocardiographic (ECG) intervals are widely used by clinicians for individual patient diagnosis and by investigators in population studies. We examined whether clinically significant systematic differences exist in ECG intervals measured by current generation digital electrocardiographs from different manufacturers and whether differences, if present, are dependent on the degree of abnormality of the selected ECGs. Measurements of RR interval, PR interval, QRS duration, and QT interval were made blindly by 4 major manufacturers of digital electrocardiographs used in the United States from 600 XML files of ECG tracings stored in the US FDA ECG warehouse and released for the purpose of this study by the Cardiac Safety Research Consortium. Included were 3 groups based on expected QT interval and degree of repolarization abnormality, comprising 200 ECGs each from (1) placebo or baseline study period in normal subjects during thorough QT studies, (2) peak moxifloxacin effect in otherwise normal subjects during thorough QT studies, and (3) patients with genotyped variants of congenital long QT syndrome (LQTS). Differences of means between manufacturers were generally small in the normal and moxifloxacin subjects, but in the LQTS patients, differences of means ranged from 2.0 to 14.0 ms for QRS duration and from 0.8 to 18.1 ms for the QT interval. Mean absolute differences between algorithms were similar for QRS duration and QT intervals in the normal and in the moxifloxacin subjects (mean ≤6 ms) but were significantly larger in patients with LQTS. Small but statistically significant group differences in mean interval and duration measurements and means of individual absolute differences exist among automated algorithms of widely used, current generation digital electrocardiographs. Measurement differences, including QRS duration and the QT interval, are greatest for the most abnormal ECGs.
Clinical Neurophysiology, 2014
Autonomic dysfunction has been demonstrated in patients with rapid eye movement sleep behavior di... more Autonomic dysfunction has been demonstrated in patients with rapid eye movement sleep behavior disorder utilizing heart rate variability parameters. We hypothesized that isolated rapid eye movement sleep without atonia is similarly associated with autonomic dysfunction as demonstrated by a reduction in heart rate variability. An evaluation of 120 records demonstrating rapid eye movement sleep without atonia during polysomnography was performed. Many (n=99) were discarded owing to factors potentially affecting heart rate variability. The remaining 21 records were matched with 21 records of patients demonstrating normal REM atonia, and subjected to electrocardiogram analysis. The parameters measured included R to R interval (RR) length, RR standard deviation, heart rate variability power, and very low frequency, low frequency, and high frequency bands. Autonomic dysfunction was seen in patients with isolated rapid eye movement sleep without atonia as denoted by a reduction in heart rate variability compared to those with normal REM atonia. Significant differences between the groups were demonstrated in RR standard deviation (mean difference=0.1502±0.317, 95% confidence interval [95% CI]=0.006, 0.295, p=0.042), heart rate variability power (mean difference=0.3005±0.635, 95% CI=0.011, 0.589, p=0.042), and the low frequency band (mean difference=0.3166±0.616 ms(2), 95% CI=0.036, 0.597, p=0.029), and a borderline significant reduction in the high frequency band (mean difference=0.3121±0.686 ms(2), 95% CI=0.000, 0.624, p=0.050). Our data confirms the hypothesis that heart rate variability is reduced in patients with isolated rapid eye movement sleep without atonia. The values obtained are consistent with previous findings in rapid eye movement behavior sleep disorder patients. This is the first report of autonomic dysfunction in isolated rapid eye movement sleep without atonia, revealing the need for further evaluation of the clinical significance and potential implications of this finding.