Audit of the two-week pathway for patients with suspected cancer of the head and neck and the influence of socioeconomic status.

Rates of head and neck cancer are high in patients with a low socioeconomic status (SES) and outcomes are often poor. The degree to which people from different socioeconomic groups use the fast-track, two-week suspected cancer referral system is, however, unclear. The aim of this audit was therefore to analyse these referrals with reference to SES, and to focus on differences in clinical characteristics, source of referral, and rates of disease. The sample included all patients who were referred to the head and neck department at an inner-city hospital in the northwest of England between July and September 2017. According to the Index of Multiple Deprivation (IMD), most (62%) of them lived in the most deprived quintile. A total of 390 referrals were analysed of which 60% were female, 53% were under 60 years of age, 33% smoked, and 69% consumed fewer than 10 units of alcohol/week. Only 24 were referred by dentists, but these accounted for almost one quarter of those referred to maxillofacial surgery. Common symptoms included a swelling or lump (n=153, 39%), hoarseness (n=101, 26%), ulcer (n=29, 7%), and sore throat (n=23, 6%). Forty-five per cent were referred with other symptoms. A total of 28 (7%) were diagnosed with cancer of the head and neck. Rates were higher in patients referred by dentists (p=0.02) and in those who drank more alcohol (p=0.02). The positive predictive value was higher in the least deprived (17%) than in the most deprived (6%). In primary care, more education that is aimed specifically at people of lower SES might reduce the number of "worried well" and lessen the pressure on departments to achieve the two-week target.

Exercise-induced changes in the QT interval duration and dispersion in patients with sudden cardiac death after myocardial infarction.

BACKGROUND: Prolongation of the QT interval and increased QT dispersion have been proposed to be associated with arrhythmic risk after myocardial infarction. However, controversy remains regarding the prognostic value of ventricular repolarization abnormalities in the risk stratification of patients surviving acute myocardial infarction. HYPOTHESIS AND OBJECTIVE: The QT interval is sensitive to myocardial ischaemia, and exercise-induced ischaemia may change the QT interval regionally, resulting in increased QT dispersion. This study examined whether there are abnormalities of ventricular repolarization during exercise and whether assessment of the exercise-induced changes in QT interval duration and dispersion would be able to differentiate patients at high risk from those at low risk of sudden cardiac death after myocardial infarction. METHODS: Twenty-six post-myocardial infarction patients (mean age 54.5+/-8.9 years, 22 men) were retrospectively studied. Thirteen patients who died suddenly (SCD patients) during a follow-up of 39+/-6 months were compared to 13 patients who remained event-free, i.e. no ventricular tachyarrhythmias, no reinfarction, no by-pass (MI survivors). The two groups were pair-matched for age, gender, site of infarction, left ventricular ejection fraction and use of beta blocker. A further 13 patients with chest pain, normal coronary arteriograms and negative exercise test results were studied as controls. They were age and gender matched with the post-infarction patients. A 12-lead exercise ECG was recorded from each patient before, during and after exercise. QT and RR interval were measured on the exercise ECGs at each stage and QT dispersion was defined as the difference between the maximum and minimum QT intervals across the 12-lead ECG. RESULTS: There were no significant differences in RR, QT and QTc (Bazett's and Fridericia's correction) intervals, or QT dispersion between any groups before exercise. A significant difference in QT and QT dispersion was found at peak exercise between post-infarction patients and controls (P=0.03 and P=0.0001, respectively), but no difference was observed between SCD patients and MI survivors. The maximum QTc at peak exercise was longer in SCD patients compared with MI survivors (P=0.02) and a maximum QTc>440 ms (Bazett's correction) was common in SCD patients but not in MI survivors or controls (62%, 15%, 15%, P=0.01). The differences in QT, QTc or QT dispersion observed at peak exercise were no longer significant after exercise. CONCLUSIONS: Exercise-induced prolongation of the QTc interval differentiates patients at high risk of sudden cardiac death from those at low risk, whereas exercise-induced changes in QT dispersion failed to identify patients at high risk of sudden cardiac death after myocardial infarction.

Stepwise strategy on the cost of risk stratification after acute myocardial infarction: a retrospective simulation study.

Stratification of postinfarction patients at high risk of mortality and/or other adverse events can be improved by combining several prognostic markers. As the clinical impact of risk stratification has only recently emerged in prospective trials, there are a lack of data regarding the cost-effectiveness of multimarker strategies. This study performed a comprehensive search of a postinfarction database and simulated different risk stratification strategies involving left ventricular ejection fraction, signal-averaged electrocardiography, Holter monitoring, and heart rate variability, The parameters were assessed before discharge in 417 survivors of acute myocardial infarction followed-up for 1 year. Cardiac mortality was used as the clinical endpoint. A statistical computer model of a stepwise strategy using every feasible sequence of the four tests was used and, based on prices derived from European and American centers, the cost estimates of all possible combinations were compared. During the 1 year after myocardial infarction there were 24 cardiac deaths (5.8%). In all the population, 6% had all four tests positive (cardiac mortality 20%); 25% had at least three tests positive (cardiac mortality 12.5%); 58% had at least two tests positive (cardiac mortality 8.3%); and 92% presented with at least one test positive (cardiac mortality 6.3%). The cost of performing all the tests ranged between $398 and $1,887 for each patient. However, by selecting patients according to a step wise strategy, the costs ranged from $96 (> or = 1 test positive) to $510 (for the least expensive sequences of four tests positive). For each of the centers considered, the costs resulting from the risk stratification protocol were determined by the number of variables combined and sequences of tests adopted. Thus, a step wise strategy using the combination of all four parameters, starting with analysis of Holter variables and finishing with signal-averaged electrocardiography, appears to be the most appropriate and the least expensive approach for selecting patients at high risk of cardiac death.

Selection of dichotomy limits for multifactorial prediction of arrhythmic events and mortality in survivors of acute myocardial infarction.

AIMS: To evaluate the predictive value and optimum dichotomy limits for different combinations of prognostic indicators for the prediction of arrhythmic events and cardiac mortality in post-infarction patients. BACKGROUND: Studies of new interventions based on risk stratification after myocardial infarction have often used a single variable as a predictor of risk. However, whether the dichotomy limits of these single variables, derived from univariate analyses, should be altered when such variables are combined for the prediction of risk after myocardial infarction has not been examined. METHODS: Left ventricular ejection fraction, signal-averaged electrocardiography, heart rate variability index, mean heart rate and ventricular extrasystole frequency were recorded pre-discharge in 439 survivors of their first myocardial infarction. Arrhythmic events and cardiac mortality were recorded during 1 year (range 1-6 years) follow-up. RESULTS: During follow-up for at least 1 year, there were 25 cardiac deaths and 23 arrhythmic events. Different optimum dichotomy limits were obtained for the prediction of cardiac mortality vs arrhythmic events, for different combinations of variables, for different selected levels of sensitivity and for different numbers of variables abnormal before identification of those at risk. The dichotomy limit of the heart rate variability index for the prediction of events appeared to be the least affected by the inclusion of other variables. For example, when predicting arrhythmic events using combinations of left ventricular ejection fraction and/or heart rate variability, the optimum dichotomy limits when each variable was used alone was 32% and 18 units respectively; 43% and 18 units when either left ventricular ejection fraction or heart rate variability are required to be abnormal, and 52% and 19 units when both are required to be abnormal before identification of those at risk of arrhythmic events. CONCLUSIONS: Dichotomy limits derived from univariate analyses do not optimally predict events when used in the multivariate setting. Risk stratification can be improved by using several variables in combination and is further improved by using dichotomy limits of these variables which are different from those used in or derived from univariate analyses.

Stepwise strategy of using short- and long-term heart rate variability for risk stratification after myocardial infarction.

Independent of other established risk factors, depressed heart rate variability (HRV) has been shown to be a powerful predictor of cardiac events after MI. Unfortunately, the need of 24-hour ECG recording and subsequent laborious editing of Holter data limits the clinical use of long-term HRV. In order to perform post-MI risk stratification more efficiently, we evaluated the value of short-term HRV estimates for preselection of patients who might benefit from long-term HRV assessment. Two measures were assessed from 24-hour ambulatory ECGs recorded in 729 survivors of acute MI prior to hospital discharge. In addition to a complete 24-hour HRV index, a standard deviation of normal-to-normal RR intervals (SDNN) was obtained from the first stationary and ectopic free 5-minute segment of the Holter recording. Predictive power (relation between positive predictive accuracy and sensitivity) of a complete 24-hour HRV index in identifying patients who suffered from cardiac mortality or arrhythmic events during a 2-year follow-up was compared to the predictive power of assessing the 24-hour HRV index limited to 50%, 40%, or 20% of patients with the lowest values of 5-minute SDNN. The HRV index was significantly lower in patients who died (19 +/- 11 units) or had an arrhythmic event (AE) (18 +/- 11 units) compared to those who survived without an event (28 +/- 10 resp. 27 +/- 11 units; P < 0.001). Similarly, 5-minute SDNN was significantly lower in patients who died (25 +/- 12 ms) or suffered an AE (26 +/- 13 ms) compared to survivors (40 +/- 19 ms resp. 39 +/- 19 ms; P < 0.001). When limited to patients with depressed 5-minute SDNN, assessment of the HRV index performed better than 5-minute SDNN alone in positive prediction of cardiac events. Preselected assessment of the lowest HRV index in 50% to 20% of the total population yielded a 2-year cardiac event prediction rate as high as analysis of the HRV index in all patients. Long-term HRV assessment for risk stratification after MI in patients preselected by depressed short-term SDNN is safe and efficient, and allows a practical identification of patients with the highest likelihood of cardiac events during long-term follow-up.

Distinction between arrhythmic and nonarrhythmic death after acute myocardial infarction based on heart rate variability, signal-averaged electrocardiogram, ventricular arrhythmias and left ventricular ejection fraction.

OBJECTIVES: We investigated whether heart rate variability, the signal-averaged electrocardiogram (ECG), ventricular arrhythmias and left ventricular ejection fraction predict the mechanism of cardiac death after myocardial infarction. BACKGROUND: Postinfarction risk stratification studies have almost exclusively focused on predicting the risk of arrhythmic death. The factors that identify and distinguish persons at risk for arrhythmic and nonarrhythmic death are poorly known. METHODS: Heart rate variability, the signal-averaged ECG, ventricular arrhythmias and left ventricular ejection fraction were assessed in 575 survivors of acute myocardial infarction. The patients were followed up for 2 years; arrhythmic and nonarrhythmic cardiac deaths were used as clinical end points. During the follow-up period, 47 cardiac deaths occurred, 29 (62%) arrhythmic and 18 (38%) nonarrhythmic. RESULTS: All risk factors were associated with cardiac mortality in univariate analysis. With the exception of left ventricular ejection fraction, they were also predictors of arrhythmic death. Depressed heart rate variability (p < 0.001), ventricular ectopic beats (p < 0.001) and low ejection fraction (p < 0.001) were related to nonarrhythmic death. In multivariate analysis, depressed heart rate variability (p < 0.001) and runs of ventricular tachycardia (p < 0.05) predicted arrhythmic death. Nonarrhythmic death was associated with depressed heart rate variability (p < 0.001), ventricular ectopic beats (p < 0.001) and low ejection fraction (p < 0.01). By selecting patients with depressed heart rate variability, long filtered QRS duration or ventricular arrhythmias and excluding patients with the lowest ejection fraction, we identified a group in which 75% of deaths were arrhythmic. Similarly, by selecting patients with a low ejection fraction and excluding patients with the lowest heart rate variability, we identified a group in which 75% of deaths were nonarrhythmic. CONCLUSIONS: Arrhythmic death was associated predominantly with depressed heart rate variability and ventricular tachycardia runs, and nonarrhythmic death with low ejection fraction, ventricular ectopic beats and depressed heart rate variability. A combination of risk factors identified patient groups in which a majority of deaths were either arrhythmic or nonarrhythmic.

[Risk of mortality after myocardial infarction: value of heart rate, its variability and left ventricular ejection fraction]. / Risque de mortalité après un infarctus du myocarde: apport de la fréquence cardiaque, de sa variabilité, et de la fraction d'éjection ventriculaire gauche.

Heart rate variability is a useful parameter for risk stratification after myocardial infarction. However, the relationship between heart rate itself and its variability has not been adequately studied. The authors compared the average RR interval of 24 hours recorded by Holter monitoring with the variability of heart rate and of left ventricular ejection fraction to assess the risk of death after myocardial infarction. A total of 579 patients was followed up for 2 years after acute myocardial infarction. During this period, there were 54 deaths, 42 of cardiac origin, 26 being classified as sudden death. The positive predictive value of left ventricular ejection fraction was lower than those of mean RR interval and the variability of heart rate for overall mortality, cardiac mortality and sudden death. The three indices were essentially equivalent for the prediction of non-sudden cardiac death. The positive predictive value of heart rate variability was better than the mean RR interval for sensitivities < 40%, for all cause mortality. However, for sensitivities > 40%, the two parameters were equivalent or slightly in favour of the mean heart rate over 24 hours. The authors conclude that the mean RR interval over 24 hours is an important prognostic index after myocardial infarction. This index is more powerful than left ventricular ejection fraction and comparable to heart rate variability.

Spectral turbulence versus time-domain analysis of signal-averaged ECG used for the prediction of different arrhythmic events in survivors of acute myocardial infarction.

INTRODUCTION: Spectral turbulence analysis of the signal-averaged ECG (SAECG) combines spectral analysis with statistical evaluation of spectrograms of individual parts of the QRS complex. It has been suggested that it may be superior to conventional time-domain analysis of the SAECG. METHODS AND RESULTS: This study compared the power of conventional time-domain (40 to 250 Hz) and spectral turbulence analyses of SAECG for the prediction of cardiac death, ventricular tachycardia, sudden arrhythmic death, and arrhythmic events (ventricular tachycardia or fibrillation, and/or sudden arrhythmic death) after acute myocardial infarction in 603 patients. The population excluded patients with bundle branch block and other conduction abnormalities. During the first 2 years of follow-up, there were 40 cardiac deaths, 21 cases of ventricular tachycardia, 1 sudden arrhythmic deaths, and 29 arrhythmic events. The positive predictive accuracy of spectral turbulence analysis was significantly higher than time-domain analysis for cardiac death at most levels of sensitivity (e.g., 26% vs 20% at 40% sensitivity, P < 0.05). The positive predictive accuracies of the two techniques were not statistically different for the prediction of ventricular tachycardia. For the prediction of sudden arrhythmic death and arrhythmic events, the positive predictive accuracy of spectral turbulence was better than that of time-domain analysis only at the higher levels of sensitivity (9% vs 2%, P < 0.001 for sudden arrhythmic death at 60% sensitivity, and 14% vs 11%, P < 0.05 for arrhythmic events at 60% sensitivity). CONCLUSIONS: Spectral turbulence analysis is essentially equivalent to time-domain analysis for the prediction of arrhythmic events after myocardial infarction. However, it performed significantly better than time-domain analysis for the prediction of cardiac death.

Predictive power of increased heart rate versus depressed left ventricular ejection fraction and heart rate variability for risk stratification after myocardial infarction. Results of a two-year follow-up study.

OBJECTIVES: The aim of this study was to compare the predictive value of mean RR interval assessed from predischarge Holter recordings with that of heart rate variability and left ventricular ejection fraction for risk stratification after myocardial infarction. BACKGROUND: Heart rate variability is a powerful tool for risk stratification after myocardial infarction. Although heart rate variability is related to heart rate, little is known of the prognostic value of 24-h mean heart rate. METHODS: A total of 579 patients surviving the acute phase of myocardial infarction were followed up for at least 2 years. Predischarge heart rate variability, 24-h mean RR interval and left ventricular ejection fraction were analyzed. RESULTS: During the first 2 years of follow-up, there were 54 deaths, 42 of which were cardiac (26 sudden). Shorter mean RR interval was a better predictor of all-cause mortality as well as cardiac and sudden death than depressed left ventricular ejection fraction. Depressed heart rate variability predicted the risk of death better than mean RR interval for sensitivities < 40%. For sensitivities > or = 40%, mean RR interval was as powerful as heart rate variability. All three variables performed equally well in predicting nonsudden cardiac death. For cardiac death prediction, a left ventricular ejection fraction < 35% had a 40% sensitivity, 78% specificity and 14% positive predictive accuracy; a mean RR interval < 700 ms had a 45% sensitivity, 85% specificity and 20% positive predictive accuracy; and a heart rate variability < 17 U had a 40% sensitivity, 86% specificity and 20% positive predictive accuracy. CONCLUSIONS: Predischarge 24-h mean heart rate is a strong predictor of mortality after myocardial infarction that can compete with left ventricular ejection fraction and heart rate variability.

Use of ventricular premature complexes for risk stratification after acute myocardial infarction in the thrombolytic era.

The independent predictive role of ventricular premature complex (VPC) frequency in the stratification of mortality risk after acute myocardial infarction (AMI) was established in the prethrombolytic era by extensive multicenter trials. Thrombolysis has lead to important changes in the natural history of patients after AMI, so that reassessment of established risk factors is now required. The prognostic significance of VPCs was assessed in 680 patients, of whom 379 received early thrombolytic therapy. All patients underwent 24-hour Holter monitoring in a drug-free state between 6 and 10 days after AMI. Patients were followed up for 1 to 8 years. During the first year of follow-up, cardiac death occurred in 33 patients, sudden death in 24, and sustained ventricular tachycardia in 20. Mean VPC frequency was significantly higher in patients who died of cardiac causes, in those who died suddenly, and in those with arrhythmic events during the first year of follow-up. This was also true when patients who did and did not undergo thrombolysis were considered separately. The positive predictive accuracy of VPC frequency in predicting adverse cardiac events was greater in patients who did than did not undergo thrombolysis. At a sensitivity level of 40%, the positive predictive accuracy for cardiac mortality and arrhythmic events for the group with thrombolysis was 19.4% and 25.8%, respectively, compared with 16% and 16% for those without thrombolysis. Moreover, the highest VPC frequency for the dichotomy of patients into high-and low-risk groups was 25 VPCs/hour for patients without thrombolysis. VPC frequency appears to be more highly predictive of prognosis after AMI in patients who have undergone thrombolysis than in those who have not, but the optimal frequency for dichotomy is higher in the former.

Day-to-day reproducibility of time-domain measures of heart rate variability in survivors of acute myocardial infarction.

We conclude that in clinically unchanged conditions, the time-domain HR variability measures derived from 24-hour ambulatory recordings of AMI survivors are stable during the early convalescent phase, and the day-to-day differences have only little effect on the result. The only exception appears to be the pNN50 parameter, the use of which should be favorably substituted by the rMSSD measurement. Geometric estimates of HR variability are highly and consistently correlated with statistical measures of overall HR variability, and may be used as substitutes for each other.

Numeric processing of Lorenz plots of R-R intervals from long-term ECGs. Comparison with time-domain measures of heart rate variability for risk stratification after myocardial infarction.

The so-called "Lorenz plots" are scatterplots that show the R-R interval as a function of the preceding R-R intervals. Repeatedly, it has been proposed that these plots might be used for visualizing the variability of the heart rate and that the assessment of heart rate variability (HRV) from these plots might be superior to conventional measures of HRV. However, a precise numeric evaluation of the images of Lorenz plots have never been suggested. To classify the images of Lorenz plots, a computer package that measures their density was developed. For each rectangular area of the plot, the relative number of R1/R2 samples in that area is established and a function is created that assigns the maximum relative number of samples (i.e., the maximum density) to each size of an area of the plot. Plots that are very compact result in a sharply falling density function, while plots that are more diffuse lead to a flat density function. The distinction between such types of density function may be expressed as a logarithmic integral of the density function to express the "compactness" of the plot numerically. As the computational demands of this approach are intensive, an approximate method that restricts the measurement of the density to the area around the peak of the plot was also developed. The results of this approximate method correlate strongly with the full results (r = .98), and approximate measurement of one plot requires less than 1 minute of computer time. The approximate method has been applied to a set of 24-hour Holter records obtained from 637 survivors of acute myocardial infarction. For each record, the SDNN and SDANN values were also calculated as conventional measures of HRV. Both the density of the Lorenz plots and the conventional measures of HRV were used to investigate the differences among 48 patients who suffered an arrhythmic event (sudden death or sustained symptomatic ventricular tachycardia) during a 2-year follow-up period and the remaining 589 patients without arrhythmic postinfarction complications. At a sensitivity of 30%, the Lorenz plot density distinguished the patients with events with a positive predictive accuracy of 58%, while the SDNN and SDANN led to a positive predictive accuracy of only 23 and 18%, respectively. Thus, a detailed analysis of Lorenz plots is feasible and more clinically useful than the conventional measures of HRV.

Influence of the infarct site on the identification of patients with ventricular tachycardia after myocardial infarction based on the time-domain and spectral turbulence analysis of the signal-averaged electrocardiogram.

In a significant proportion of patients with sustained ventricular tachycardia (VT) following anterior myocardial infarction, the areas of slow conduction are activated early during cardiac depolarization. Therefore, they may not be detected by the standard time-domain analysis of the signal-averaged electrocardiogram (SAECG) which is limited to the terminal part of the QRS complex. Spectral turbulence analysis of the SAECG is a new frequency domain technique which examines the whole QRS complex and may improve identification of patients with sustained VT following anterior infarction. We compared the results of time-domain and spectral turbulence analyses of the SAECG in 53 postinfarction patients with sustained VT and in 53 age-, gender- and infarct site-matched patients without VT. The receiver operator characteristic curves have shown that the time-domain analysis resulted in better identification of patients with VT following inferior than following anterior infarction (e.g., at the sensitivity level of 90%, the corresponding values of specificity were 96 and 90%, respectively), whereas the spectral turbulence analysis performed better in the anterior site of infarction. When both time-domain and spectral turbulence analyses were combined, the accuracy of the SAECG for identification of patients with VT following anterior infarction improved, reaching a specificity of 97% at the sensitivity level of 90%. In conclusion (1) spectral turbulence analysis of the SAECG results in better identification of patients with VT following anterior than following inferior infarction, and (2) the combination of time-domain and spectral turbulence analyses of the SAECG may improve identification of patients with VT following anterior infarction.

A test of alternative supervision strategies for family planning services in Guatemala.

This report presents results of an operations research project that tested the impact and cost-effectiveness of alternative supervision schemes of reproductive health services in Guatemala. The strategies tested were (1) indirect supervision, in which one of the two annual supervised visits to each health unit was replaced by a one-day meeting at the district level with the supervisor; and (2) self-assessment, in which one supervised visit was replaced by a two-day workshop where participants filled out self-assessment checklists identifying quality of care problems and made a plan to solve identified problems during the following months. Health units in the two experimental groups showed greater increases in productivity than units receiving traditional supervision. In both alternative strategies, supervisors were able to reach a larger proportion of health units and service providers than through the traditional supervision system. The supervised cost per unit was also lower in the two experimental groups than in the control group. Few differences were observed between the experimental and control groups in terms of the satisfaction of service providers with their jobs and of clients with services received.

Unrecognized dyslipoproteinemia in United Kingdom families recruited to a genetic register because of unexplained coronary heart disease.

A register was built up of DNA from United Kingdom families with premature coronary heart disease and no perceived risk associations in the expectation that obscure causal factors could be defined through future genetic analysis. Referrals came from interested, predominantly cardiologic units in southern England. For inclusion, probands had documented coronary heart disease before age 55 years that was regarded as unexplained, in families with at least two living affected first-degree and two other members, in most families over two generations. Referred probands and family members completed a questionnaire on general health and habits and were examined for body mass index, blood pressure, resting electrocardiogram, and lipoprotein profile. Data are presented on 276 living members from 26 families, representing 75.4% of all members age 15 years and older. The striking observation was the extent of dyslipoproteinemia that was not identified by the referring units as relevant to the expression of accelerated coronary heart disease. This was expressed as hypercholesterolemia, reduced levels of high-density lipoprotein, or both, in comparison with profiles recorded over the same period and for a similar but unselected general British population. Further genetic analysis for a major occult risk factor in these families is inappropriate. Present concerns with potential adverse associations with low cholesterol, or with lipid-lowering treatment, should be addressed in the knowledge that uncontrolled dyslipoproteinemia also has severe adverse associations. These associations are still not widely appreciated in the management of patients and families with premature coronary heart disease.

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.

Influence of filtering techniques on the time-domain analysis, diagnosis, and clinical use of signal-averaged electrocardiogram.

In order to investigate the effect of different filtering techniques on the time-domain analysis of signal-averaged electrocardiogram (SAECG), recordings of 1,192 subjects were analyzed using Butterworth and Del Mar filters, both set at 40-250 Hz high and low pass frequencies. The recordings were taken from six clinically defined groups: (a) survivors of acute myocardial infarction (n = 553); (b) patients with sustained symptomatic postinfarction ventricular tachycardia (n = 89); (c) patients with hyperthropic cardiomyopathy (n = 219); (d) patients with dilated cardiomyopathy (n = 76); (e) direct relatives of patients with dilated cardiomyopathy (n = 170); and (f) normal healthy volunteers (n = 85). The study investigated differences between the SAECG results reported with both filters in three individual aspects: (1) numerical values of individual time-domain SAECG variables; (2) differences in SAECG findings of patients with postinfarction ventricular tachycardia and pair matched patients with uncomplicated follow-up after acute infarction; and (3) the power of SAECG findings to predict high risk of arrhythmic complication (sudden death and/or sustained ventricular tachycardia) among survivors of acute myocardial infarction. Compared with the Butterworth filter, the Del Mar filter led to a systematic difference of +8% in total QRS duration, was equally powerful in distinguishing between the pair matched patients with and without postinfarction ventricular tachycardia, and was statistically significantly more powerful in identifying those survivors of acute infarction who were at high risk of arrhythmic complications. The study concludes that the use of different filters may produce discordant results of SAECG analysis. Normal and abnormal values for various types of SAECG recording and analysis have to be established individually for different equipment and different software settings. These optimal cut-offs of SAECG variables should also take into account the clinical characteristics of patient groups.

Spectral turbulence analysis versus time-domain analysis of the signal-averaged ECG in survivors of acute myocardial infarction.

This study compared the time-domain and spectral turbulence analyses of signal-averaged electrocardiogram (ECG) for the prediction of risk after acute myocardial infarction. Signal-averaged ECGs were recorded in 553 survivors of acute myocardial infarction before hospital discharge. The study excluded cases with bundle branch block and other conduction abnormalities, and patients were followed for at least 1 year. During the first year of the follow-up period, 30 patients died and 20 presented with ventricular tachycardia/fibrillation. The signal-averaged ECG recordings were analyzed using conventional time domain at 40-250 Hz and spectral turbulence analyses. The indices provided by both types of analysis were compared in patients with and without endpoints. The optimum positive predictive characteristics were calculated for the prediction of all cause mortality and of ventricular tachycardia based on the time domain and on the spectral turbulence indices. Spectral turbulence analysis provided significantly lower positive predictive accuracy (14.5% at 40% sensitivity) than the time-domain analysis (26.7% at 40% sensitivity) for prediction of ventricular tachycardia/fibrillation during 1 year after infarction (P < .01). However, spectral turbulence analysis provided significantly higher positive predictive accuracy (27.2% at 30% sensitivity) than the time-domain analysis (16.9% at 30% sensitivity) for the prediction of 1-year all-cause mortality (P < .01). Thus, spectral turbulence analysis was inferior to the time-domain analysis in predicting ventricular tachycardia/fibrillation during the first year after myocardial infarction, but it was more powerful in predicting 1-year mortality.

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)