Improving employees' telephone skills.
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Communication↗
Biomedical subjects
T Farrell
Publications and source records attributed to T Farrell.
Myoclonus associated with propafenone.
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Aged↗
Temporal influences on the prediction of postinfarction mortality by heart rate variability: a comparison with the left ventricular ejection fraction.
OBJECTIVE: To examine the influence of the duration of follow up on the values of heart rate variability (HRV) and the left ventricular ejection fraction (LVEF) for predicting mortality after infarction. BACKGROUND: HRV is an index of autonomic balance that identifies patients at a high risk of arrhythmic events. The index is most depressed during the first few weeks after myocardial infarction whereas left ventricular function tends to deteriorate with time. HYPOTHESIS: The value of depressed HRV measured before discharge from hospital for predicting mortality after infarction should decline with time. METHODS: The HRV and the LVEF were assessed in 433 survivors of a first acute myocardial infarction: HRV < 20 units and LVEF < 40% were taken as cut off points. Kaplan-Meier survival functions for total cardiac mortality and sudden cardiac death were calculated for the whole five year follow up period and for different intervening periods. RESULTS: During follow up of four weeks to five years there were 46 (10.6%) deaths and 15 (3.5%) patients died suddenly. Within the whole follow up period, HRV < 20 units and LVEF < 40% were both strongly associated with total cardiac mortality (p < 0.0001), but HRV was an independent predictor of total cardiac mortality only during the first six months of follow up. There were no deaths predicted by HRV < 20 units after the first year of follow up whereas LVEF < 40% had a sensitivity of 43% and a positive predictive accuracy of 9% for predicting death during this period. HRV < 20 units was better than LVEF < 40% in predicting sudden deaths during the first year of follow up but was an independent predictor only of those sudden deaths occurring within six months of infarction. CONCLUSIONS: The duration of follow up affects the prediction of sudden death and total cardiac mortality from HRV. Reduced HRV as measured before discharge from hospital does not seem to retain independent prognostic value after six months of follow up. These findings have potential implications for the serial evaluation of HRV and for the prevention of sudden death after myocardial infarction.
Death, Sudden, Cardiac↗
Identification of inappropriate radiological referrals with suspected gallstones: a prospective audit.
The objective of this study was to derive and test clinical scoring system in order to predict the presence of gallstones and to identify inappropriate referrals. The design of this scoring system comprised a prospective audit of all referrals with suspected gallstones and a prospective validation of the system on new patients. The subjects used in the study consisted of 300 inpatient, outpatient and general practitioner referrals to a radiology department with suspected gallstones during the period 1984-1986 (1st cohort) and 200 similar referrals from 1987 to 1988 (2nd cohort). The main outcome measures were gallstones as determined by oral cholecystogram and/or ultrasound of the gallbladder. 32.7% and 24.0% of referrals in the first and second cohorts, respectively, had gallstones. A scoring system to predict gallstones was derived on the first cohort based on age, Murphy's sign, duration and type of pain, presence or absence of flatulence, and source of referral. This scoring system discriminated well between those with and without stones in both cohorts. Low risk groups, comprising about 15% of the referrals in each cohort, were identified with a prevalence of gallstones of 4.5% (1st cohort) and 3.0% (2nd cohort). If these patients had not been referred the radiological workload would have dropped by 15%, with a very small reduction in diagnostic yield. We conclude that prior to radiological assessment it is possible, on the basis of source of referral and symptoms, to identify a group of patients with a low prevalence of gallstones. These cases, with a low diagnostic yield, contribute substantially to the workload of a radiological department.
Adult↗
Evaluation of ocular health among alachlor manufacturing workers.
Earlier toxicology studies found that one strain of rat (Long-Evans) developed severe ocular lesions when fed high doses of alachlor, a chloracetanilide active ingredient in some preemergent herbicides used for corn, soybean, and peanut crops. Because of a lack of eye effects in feeding studies conducted in dogs and other rodent species and strains, the effect was believed to be specific to Long-Evans rats. Nevertheless, to determine whether there were ocular effects among alachlor-exposed workers, we examined a group of the highest exposed alachlor production workers (n = 135) for the presence of a specific eye abnormality, analogous to the initiating lesion in Long-Evans rats, called pigmentary dispersion syndrome. A similar examination was given to unexposed coworkers and relatives (n = 84) to provide comparison rates. None of the exposed workers were found to have pigmentary dispersion syndrome, and prevalence rates for other eye abnormalities were similar for exposed and unexposed study participants. These results suggest that humans exposed to alachlor are not at increased risk of developing ocular disease.
Acetamides↗
Improved identification of late potentials by adjustment of the number of analyzed segments of the spectral temporal mapping of the signal-averaged electrocardiogram.
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Electrocardiography↗
Influence of thrombolytic therapy on the evolution of baroreflex sensitivity after myocardial infarction.
Depressed baroreceptor sensitivity (BRS) has been associated with an increased risk of ventricular arrhythmias and sudden cardiac death after myocardial infarction, but the influence of thrombolytic therapy on BRS has not been examined. To determine the effect of thrombolytic therapy on the evolution of BRS after myocardial infarction, BRS was assessed at 6 days, 6 weeks, and 3 months in 76 patients, 53 (70%) of whom had received thrombolytic therapy. The mean age (57 vs 57 years), sites of infarction, and the proportion of patients taking beta-blockers (68% vs 52%) did not differ between patients who did and those who did not receive thrombolytic therapy. There was no difference in predischarge mean left ventricular ejection fractions (42% vs 46%) between the two groups of patients, but mean baseline BRS was 9.2 (0.8) msec/mm Hg in patients who were treated with thrombolysis and 5.9 (1.3) msec/mm Hg in those who were not (p = 0.03). At 6 weeks the corresponding values were 9.7 (1.1) and 11.1 (2.8) msec/mm Hg (p = 0.6) and at 3 months 9.1 (1.0) and 6.5 (1.1) msec/mm Hg (p = 0.07). At baseline 13% of patients who were treated with thrombolysis and 13% of those who were not had BRS < 3.0 msec/mm Hg, but at 3 months 9% of patients who were treated with thrombolytic agents compared with 17% of those who had BRS < 3.0 msec/mm Hg. In conclusion, early after myocardial infarction mean BRS was higher in patients treated with thrombolysis compared with nontreated patients.(ABSTRACT TRUNCATED AT 250 WORDS)
Aging↗
Autonomic correlates of late infarct artery patency after first myocardial infarction.
Occlusion of the infarct-related artery has recently been associated with an increased risk of sudden death, particularly in patients with poor left ventricular function. Depressed heart rate variability (HRV) also identifies postinfarction patients at an increased risk of sudden death. The correlation between infarct artery patency, left ventricular function, and HRV was therefore examined in 186 survivors of a first myocardial infarction. Predischarge coronary angiography and Holter monitoring were carried out in 186 patients with a first acute myocardial infarction. Coronary angiography was performed because of abnormal predischarge exercise test findings. Mean age (56 +/- 9 years) and the proportions of type and site of infarction did not differ between patients with occluded or patent arteries or between patients who did or did not undergo coronary angiography. The mean left ventricular ejection fraction (EF) was 55 +/- 15% in patients with patent and 49 +/- 14% in those with occluded infarct arteries (p < 0.001), and the EF was < 40% in 17% and 28% of the respective groups (p < 0.05). HRV was < 20 U in 7 (18%) of the 39 patients with an EF < 40% but in only 7 (5%) of the 147 patients with an EF > 40% (p < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Effect of thrombolytic therapy on the predictive value of signal-averaged electrocardiography after acute myocardial infarction.
Standard time domain variables from signal-averaged electrocardiography were examined in a population of 331 survivors of acute myocardial infarction. Of these subjects, 130 received early (less than 24 hours) thrombolytic therapy. During a follow-up of greater than or equal to 10 months, there were 17 arrhythmic events (8.5%) (sudden death or sustained symptomatic ventricular tachycardia) in the group without thrombolysis and 8 (6.2%) in those with thrombolysis. Statistically, highly significant differences between the signal-averaged electrocardiographic variables of patients with and without arrhythmic events were found in the group without thrombolysis, whereas only root-mean-square voltage of the terminal 40 ms of the signal-averaged QRS complex was statistically associated with outcome (the differences in the other 2 indexes being not significant) in patients with thrombolysis. When using 2 previously published categoric criteria for the diagnosis of abnormal signal-averaged electrocardiography, the performance of these criteria in predicting arrhythmic events was substantially better in the group without thrombolysis than in those with thrombolysis (positive predictive accuracy greater than 3 times lower). Retrospectively adjusted receiver-operator characteristics showed that for a sensitivity of 30%, the maximum achievable positive predictive accuracy of signal-averaged electrocardiography for arrhythmic events was 100% in the group without thrombolysis, but only 27% in those with thrombolysis. It is concluded that standard signal-averaged electrocardiography after acute myocardial infarction is less informative in patients who receive thrombolytic treatment.
Adult↗
Differences between predictive characteristics of signal-averaged electrocardiographic variables for postinfarction sudden death and ventricular tachycardia.
Several studies indicate that the electrophysiologic substrate for sustained ventricular tachycardia differs from that of ventricular fibrillation. This prospective study examined whether there were clinically relevant differences between the predictive values of the standard time-domain signal-averaged (SA) electrocardiographic (ECG) variables for ventricular tachycardia and sudden death after myocardial infarction. Predischarge SA electrocardiograms were recorded in 332 patients after infarction. During a follow-up period of greater than or equal to 6 months, there were 12 sudden deaths (3.6%), 14 patients (4.2%) developed spontaneous sustained ventricular tachycardia and 20 patients (6%) died of circulatory failure. The sensitivity, specificity and positive predictive accuracy of the numerical values of the time-domain SA electrocardiographic variables for predicting sudden death and ventricular tachycardia were compared. The optimal criteria for predicting ventricular tachycardia required the positivity of greater than or equal to 2 of the standard time-domain SA variables, whereas the optimal criteria for predicting sudden death required the positivity of all 3 variables. A high specificity was sustained over a wider range of sensitivity for sudden death than it was for ventricular tachycardia and the values of the variables which provided the same sensitivity for sudden death and ventricular tachycardia were different. For a sensitivity of 70%, the positive predictive accuracy was 31% for predicting sudden death and 13% for predicting ventricular tachycardia. The study concludes that differences in the predictive characteristics of variables for ventricular tachycardia and sudden death may be used to refine postinfarction risk stratification.
Adult↗
Frequency versus time domain analysis of signal-averaged electrocardiograms. I. Reproducibility of the results.
Three repeated signal-averaged electrocardiographic (ECG) recordings were made in 40 subjects (15 healthy volunteers, 10 patients with ventricular tachycardia without apparent heart disease and 15 patients with ventricular tachycardia after myocardial infarction). In each subject, the three recordings were made within 25 min. The recordings were subsequently analyzed by 1) the conventional time domain method of signal-averaged ECG analysis with use of filter settings of 25 to 250 Hz and 40 to 250 Hz, 2) a spectral analysis method computing the energy area within the spectral boundaries of 40 to 140 Hz and the ratio between the energies of areas within the boundaries 40 to 140 Hz and 0 to 40 Hz, and 3) spectral temporal mapping computing the "normality factor." The study compared the reproducibility of these three approaches to the analysis of signal-averaged ECGs. First, the reproducibility of the diagnostic conclusions (that is, of the diagnosis of late potentials) was compared for the time domain method and for spectral temporal mapping. Second, the reproducibility of the numeric values of individual indexes provided by different methods was compared for all methods by computing the ratios between standard deviations of measurements in individual patients and standard deviation of all measurements. The reproducibility of diagnostic conclusions was significantly higher for the time domain method than for spectral temporal mapping (p less than 0.05, sign test). The numeric reproducibility of the normality factors produced by spectral temporal mapping was significantly lower than the numeric reproducibility of the values of all indexes provided by time domain, spectral area and spectral area ratio methods (p less than 0.05 to 0.00005, Wilcoxon tests). Spectral temporal mapping was the least reproducible method for the analysis of signal-averaged ECGs.
Adult↗
Frequency versus time domain analysis of signal-averaged electrocardiograms. II. Identification of patients with ventricular tachycardia after myocardial infarction.
Late potentials detected by the time domain signal-averaged electrocardiogram (ECG) are a well established marker for ventricular tachycardia in patients after a myocardial infarction, but the value of frequency domain analysis of the signal-averaged ECG in identifying these patients remains controversial. This study compared the results of time domain, frequency domain and spectral temporal mapping analyses of the signal-averaged ECG in 30 postinfarction patients with spontaneous sustained ventricular tachycardia and in 30 postinfarction patients without ventricular tachycardia matched for age, gender and infarct site. No patient with bundle branch block was included. Time domain signal-averaged ECG indexes were significantly different in patients with and without ventricular tachycardia (p less than 0.001). Frequency domain results were not consistently different between these groups. The values of the normality factor of spectral temporal mapping were significantly lower in patients with ventricular tachycardia (p less than 0.04). Results of the time domain signal-averaged ECG were abnormal in 22 patients with ventricular tachycardia (73%) but in only 3 control patients (10%) (p less than 0.001). Spectral temporal mapping results were abnormal in 21 patients with ventricular tachycardia (70%) compared with 12 control patients (40%) (p less than 0.04). When the optimal numeric values of dichotomy points were computed for patient stratification at different sensitivity levels, time domain analysis identified patients with ventricular tachycardia with significantly fewer false positive results than were obtained with either frequency analysis or spectral temporal mapping. It is concluded that frequency domain analysis and spectral temporal mapping of the signal-averaged ECG did not improve the identification of postinfarction patients with ventricular tachycardia and without bundle branch block.
Aged↗
Frequency versus time domain analysis of signal-averaged electrocardiograms. III. Stratification of postinfarction patients for arrhythmic events.
The predictive characteristics of spectral temporal analysis and time domain analysis of the signal-averaged electrocardiogram (ECG) for postinfarction arrhythmic events were compared in 257 patients. During a 6-month follow-up period, 7 patients (2.7%) died suddenly and 9 (3.5%) developed spontaneous sustained ventricular tachycardia. The mean numeric values of the standard time domain signal-averaged ECG variables in patients without arrhythmic events differed significantly from those in patients with arrhythmic events. The mean values of the spectral temporal signal-averaged ECG variables did not differ between the two patient groups. A strategy requiring positivity in any two time domain signal-averaged ECG variables provided the optimal receiver operating characteristic curves for predicting arrhythmic events. With spectral temporal analysis, a strategy using the Hanning window and diagnosing a positive signal-averaged ECG when two variables were abnormal provided the optimal curve for predicting arrhythmic events. Receiver operating characteristic curves showed that over a wide range of sensitivity, time domain variables had higher specificity for predicting arrhythmic events than did spectral temporal variables. Time domain analysis also provided significantly fewer false positive results than did spectral temporal analysis up to sensitivity values of 70%. It is concluded that time domain analysis of the signal-averaged ECG is superior to spectral temporal analysis for predicting arrhythmic events after myocardial infarction.
Adult↗
Late potentials after acute myocardial infarction. Performance of different criteria for the prediction of arrhythmic complications.
In order to compare different criteria for the definition of late potentials in patients after myocardial infarction, three signal averaged ECG variables, duration of the signal-averaged QRS complex (QRS), root-mean-square voltage of the terminal 40 ms (RMS-40), and the duration of low amplitude signals less than 40 microV (LASD-40), were assessed in 332 survivors of acute myocardial infarction who were followed-up for at least 6 months, during which 12 patients died suddenly and 14 suffered symptomatic sustained ventricular tachycardia. The associations of the three variables with arrhythmic events were analysed in the total population, in infarct site and age-specific subgroups. The sensitivity and specificity for the prediction of arrhythmic events was computed (for all dichotomy points) and compared with nine published criteria for late potentials based on the same three variables. Analysis showed that (a) the total signal averaged QRS duration was a better predictor of arrhythmic events than the other two variables, (b) for arrhythmic events in cases of anterior infarctions, higher RMS-40 dichotomy limits and lower QRS and LASD-40 dichotomy limits were needed for cases of inferior infarction, (c) a multivariate stratification of arrhythmic events based on all three variables performed better in the anterior infarction population than in the inferior infarction population, (d) the strategy defining late potentials, which requires that two variables reach critical values, is better than the strategies that require that any one or all three variables reach critical values, (e) all the definitions of late potentials performed differently in the populations with anterior as compared to inferior infarctions; to identify groups at similar risk of arrhythmic events, different criteria defining late potentials should be used in these subpopulations.
Action Potentials↗
Comparison of the predictive characteristics of heart rate variability index and left ventricular ejection fraction for all-cause mortality, arrhythmic events and sudden death after acute myocardial infarction.
Heart rate (HR) variability index and left ventricular ejection fraction (EF) were compared for the prediction of all-cause mortality, arrhythmic events and sudden death in 385 survivors of acute myocardial infarction. For arrhythmic events, where, for a sensitivity of 75%, HR variability index had a specificity of 76%, EF had a specificity of only 45%. An EF of less than or equal to 40% had a sensitivity of 42% and a specificity of 75% for arrhythmic events; for the same sensitivity an HR variability index of 20 U had a specificity of 92%. An EF less than or equal to 40% had a sensitivity of 40% and a specificity of 73% for sudden death; HR variability index had a specificity of 83% for the same sensitivity. For all cause mortality, where, for a sensitivity of 75%, HR variability index had a specificity of 52%, EF had a specificity of 40%. It is concluded that HR variability index appears a better predictor of important postinfarction arrhythmic complications than left ventricular EF, but both indexes perform equally well in predicting all-cause mortality.
Adult↗
Age-related normal values of signal-averaged electrocardiographic variables after acute myocardial infarction.
The study examined standard time domain variables of a signal-averaged electrocardiogram (SAECG) in 328 survivors of acute myocardial infarction. The correlation of these variables with age and the influence of age on the prediction of postinfarction arrhythmic complication (sudden death [n = 12] or sustained ventricular tachycardia, or both [n = 14]) from the SAECG were investigated. Statistically highly significant correlations (p less than or equal to 0.00002) between age and SAECG variables were found. Compared with patients aged less than 60 years, the SAECG-based stratification of arrhythmic complications after myocardial infarction in patients greater than 60 years had lower sensitivity for the same values of specificity and lower specificity for the same values of sensitivity.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
The title 'Dr' for the dentist.
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Dentists↗
Multifactorial prediction of arrhythmic events after myocardial infarction. Combination of heart rate variability and left ventricular ejection fraction with other variables.
Autonomic dysfunction has recently been shown to identify postinfarction patients at a high risk of arrhythmic events. Therefore, the predictive characteristics of heart rate variability and the left ventricular ejection fraction in combination with other prognostic variables--mean heart rate, late potentials, and ventricular ectopic beat frequency greater than 10/hour (VE10)--were examined in 417 postinfarction patients. The heart rate variability index was the most important factor for the stratification of patients at high risk of arrhythmic events after myocardial infarction and optimum stratification was based on the combination of the heart rate variability index with late potentials or with frequent ventricular ectopic beats.
Death, Sudden, Cardiac↗