Relationship between corrected TIMI frame counts at three weeks and late survival after myocardial infarction.

OBJECTIVES: To evaluate the corrected Thrombolysis in Myocardial Infarction (TIMI) frame count (CTFC) as a predictor of late survival after myocardial infarction. BACKGROUND: Thrombolysis in Myocardial Infarction flow grades predict late survival after myocardial infarction. The CTFC provides a more reproducible measurement of infarct-related artery blood flow than the TIMI flow grade, and has been linked to 30-day outcomes, but it has not yet been established how the CTFC correlates with late survival. METHODS: Of 1,001 patients with acute myocardial infarction presenting within 4 h of symptom onset, 882 underwent angiography at approximately three weeks. Infarct artery flow was assessed, blinded to clinical outcomes, according to the CTFC and TIMI flow grade. Late cardiac mortality and survival were determined in 97.5% of patients. RESULTS: The mean CTFC was 40 +/- 29 in 644 patent infarct arteries (median, 34 [interquartile range, 24 to 47]). The CTFC, assessed as a continuous univariate variable, was found to be a predictor of five-year survival, as was the TIMI flow grade (both p < 0.001). On multivariate analysis, factors associated with five-year survival included the ejection fraction or end-systolic volume index (both p < 0.001); exercise duration (p = 0.005), age (p = 0.008), diabetes (p = 0.02) and CTFC (p = 0.02) or TIMI flow (p = 0.02). The same factors, except for the CTFC and TIMI flow grade, were predictors of 10-year survival. CONCLUSIONS: The CTFC three weeks after myocardial infarction was an independent predictor of five-year survival, but not 10-year survival. Although the CTFC provided additional prognostic information within TIMI flow grades, its superiority was not demonstrated.

Survival 12 years after randomization to streptokinase: the influence of thrombolysis in myocardial infarction flow at three to four weeks.

OBJECTIVES: The purpose of this study was to determine whether the mortality benefit of intravenous streptokinase administered within 4 h of the onset of acute myocardial infarction is maintained at 12 years, and whether Thrombolysis in Myocardial Infarction (TIMI) flow grades independently influence late survival. BACKGROUND: Treatment with reperfusion therapies and achievement of TIMI 3 flow are associated with increased short- and medium-term survival after infarction. Whether infarct artery flow independently influences survival more than five years after infarction is unknown. METHODS: The late survival of patients randomized to receive either streptokinase (1,500,000 IU over 30 to 60 min) or a matching placebo within 4 h of symptom onset in 1984-1986 was determined. Angiography was performed in surviving patients at three to four weeks, and TIMI flow grades were assessed blind to randomization and outcomes. The late vital status was determined in 99% of patients. RESULTS: Patients randomized to receive streptokinase (n = 107) had improved survival compared with those randomized to placebo (n = 112) at five years (84% vs. 70%; p = 0.023) and 12 years (66% vs. 51%; p = 0.022). At five years 94% of patients with TIMI grade 3 flow, 81% of those with TIMI grade 2 flow and 72% of those with TIMI grade 0-1 flow survived (p = 0.005). At 12 years 72% of patients with TIMI 3, 67% of those with TIMI 2 and 54% of those with TIMI 0-1 flow survived (p = 0.023). Multivariate analysis identified the ejection fraction (p = 0.014), exercise duration (p = 0.013) and TIMI 3 flow (p = 0.04 compared with TIMI 0-2 flow) as important factors for five-year survival. At 12 years multivariate predictors of late survival were the ejection fraction (p = 0.006), exercise duration (p = 0.003) and myocardial score (p = 0.013). The end-systolic volume index was similar to the ejection fraction as a predictor of survival at five and 12 years. CONCLUSIONS: The survival benefits of streptokinase persist for 12 years after infarction. TIMI flow at three to four weeks is an independent predictor of five-year survival.

Waiting times and prioritization for coronary artery bypass surgery in New Zealand.

OBJECTIVES: To review the New Zealand coronary artery bypass priority score instituted in May 1996, and specifically to determine whether it prioritizes patients at high risk of cardiac events while waiting. The New Zealand score is compared with the Ontario urgency rating score, and waiting times for surgery are compared with the maximum times recommended by the Ontario consensus panel. DESIGN: Retrospective review of patients accepted for isolated coronary artery bypass surgery between 1 January 1993 and 31 January 1996. SETTING: Green Lane Hospital, Auckland, New Zealand. MAIN OUTCOME MEASURES: Waiting time, cardiac death, myocardial infarction, and cardiac readmission. RESULTS: The median waiting times were five days for hospital cases (n = 721) and 146 days for out of hospital cases (n = 701). Of the latter group, 28% waited more than a year, 33% had their surgery expedited because of worsening symptoms, and 19% failed to meet the cut off point set by the New Zealand score for acceptance onto the list. Twenty two patients died, 18 on the outpatient waiting list (waiting list mortality 2.6%, risk 0.28% per month of waiting), and 132 were readmitted, 12% with myocardial infarction and 76% with unstable angina. Risk factors for a composite end point of death or myocardial infarction and/or cardiac readmission were: previous coronary artery bypass surgery (p = 0. 001), class III or IV angina (p = 0.002), and hypertension (p = 0. 005). The New Zealand score did not identify those at risk. Excluding hospital cases, 32% had surgery within the time recommended by the Ontario consensus panel. CONCLUSIONS: Waiting times for coronary artery bypass surgery in New Zealand are considerably longer than those in Ontario, Canada. By using a numerical cut off point, implementation of the New Zealand priority scoring system has restricted access to coronary surgery on the basis of funding constraints rather than clinical appropriateness. The score does not add greatly to the clinicians' prioritization in predicting those patients who will suffer events while waiting.

Effects of early captopril administration after thrombolysis on regional wall motion in relation to infarct artery blood flow.

OBJECTIVES: To determine whether early administration of captopril lessens infarct zone regional wall motion abnormalities when infarct artery blood flow is abnormal. BACKGROUND: The interaction between angiotensin-converting enzyme (ACE) inhibitor therapy, ventricular function and infarct artery blood flow has not been well described. METHODS: A total of 493 patients aged < or = 75 years with first infarctions, presenting within 4 h of symptom onset, were randomized to receive 6.25 mg captopril, increasing to 50 mg t.d.s. or a matching placebo 2.1+/-0.4 h after commencing intravenous streptokinase (1.5 x 10(6) U over 30 to 60 min). Trial therapy was stopped 48 h prior to angiography at 3 weeks, to determine regional wall motion and infarct artery flow. RESULTS: There were no differences in ejection fractions or end-systolic volumes between patients randomized to receive captopril and those randomized to receive a placebo. Among patients with anterior infarction (n = 216), randomization to captopril resulted in fewer hypokinetic chords (40+/-13; vs. 44+/-13; p=0.028) and a trend toward fewer chords >2 SD below normal (26+/-17 vs. 30+/-17; p=0.052) in the infarct zone. In patients randomized to receive captopril who had anterior infarction and Thrombolysis in Myocardial Infarction (TIMI) 0-2, flow there were fewer hypokinetic chords (44+/-12 vs. 50+/-9; p=0.043) and a trend toward fewer chords >2 SD below normal (33+/-15 vs. 39+/-13; p=0.057). Patients receiving captopril who had anterior infarction and corrected TIMI frame counts > 27 had fewer hypokinetic chords (42+/-13 vs. 46+/-12; p=0.015) and fewer chords >2 SD below normal (27+/-17 vs. 32+/-17; p= 0.047). Captopril had no effect in patients with inferior infarction. There were 20 late cardiac deaths (median follow-up 4 years) in the captopril group and 35 in the placebo group (p=0.036). CONCLUSIONS: Randomization to receive captopril 2 h after streptokinase improved regional wall motion at 3 weeks. The greatest benefit was seen in patients with anterior infarction particularly when infarct artery blood flow is reduced.

Angiographic frame counts 90 minutes after streptokinase predict left ventricular function at 48 hours following myocardial infarction.

OBJECTIVE: To assess whether the 90 minute corrected thrombolysis in myocardial infarction frame count (CTFC) in the infarct related artery predicts left ventricular function at 48 hours in patients with myocardial infarction treated with aspirin, streptokinase, and either heparin or Hirulog. DESIGN AND SETTING: Analysis of 251 patients with acute myocardial infarction enrolled in the international, multicentre Hirulog early reperfusion/occlusion (HERO-1) trial, who underwent both 90 minute coronary angiography and 48 hour left ventriculography. MAIN OUTCOME VARIABLES: The CTFC was determined in the infarct related artery 90 minutes after starting intravenous streptokinase (1.5 x 106 U over 30 to 60 minutes), and compared with indices of left ventricular function assessed by contrast ventriculography at 48 hours. RESULTS: A CTFC of 2 SD below normal (37% v 51%, p = 0.005), and trends towards higher left ventricular ejection fractions (60.9% v 58.2%, p = 0.11) and lower end systolic volumes (50.1 ml v 55.9 ml, p = 0.23). A CTFC of 2 SD below normal (41% v 52%, p = 0.025), a smaller end systolic volume (49.1 ml v 59.3 ml, p = 0.02), and a higher left ventricular ejection fraction (60.4% v 56.5%, p = 0.03). CONCLUSIONS: The 90 minute CTFC predicts left ventricular function at 48 hours following streptokinase. The CTFC associated with better ventricular function may be higher than values determined from a non-infarct population.

Influence of lead selection and population on automated measurement of QT dispersion.

BACKGROUND: The study of QT dispersion (QTd) is of increasing clinical interest, but there are very few data in large healthy populations. Furthermore, there is still discussion on the extent to which QTd reflects dispersion of measurement. This study addresses these problems. METHODS AND RESULTS: Twelve-lead ECGs recorded on 1501 apparently healthy adults and 1784 healthy neonates, infants, and children were used to derive normal limits of QTd and QT intervals by use of a fully automated approach. No age gradient or sex differences in QTd were seen and it was found that an upper limit of 50 ms was highly specific. Three-orthogonal-lead ECGs (n=1220) from the Common Standards for Quantitative Electrocardiography database were used to generate derived 12-lead ECGs, which had a significant increase in QTd of 10.1+/-13.1 ms compared with the original orthogonal-lead ECG but a mean difference of only 1.63+/-12.2 ms compared with the original 12-lead ECGs. In a population of 361 patients with old myocardial infarction, there was a statistically significant increase in mean QTd compared with that of the adult normal group (32.7+/-10.0 versus 24.53+/-8.2 ms; P<0. 0001). An estimate of computer measurement error was also obtained by creating 2 sets of 1220 ECGs from the original set of 1220. The mean error (difference in QTd on a paired basis) was found to be 0. 28+/-9.7 ms. CONCLUSIONS: These data indicate that QTd is age and sex independent, has a highly specific upper normal limit of 50 ms, is significantly lower in the 3-orthogonal-lead than in the 12-lead ECG, and is longer in patients with a previous myocardial infarction than in normal subjects.

The value of the coefficient of variation in assessing repeat variation in ECG measurements.

AIMS: The coefficient of variation is a popular measure for describing the amount of repeat variability present in ECG measurements from recording to recording. However, it can be misleading. The aim of the present study was to assess repeat variation (reclassification) in computer measured ECG criteria, i.e. positive to negative or vice versa, and compare this with the coefficient of variability. METHODS AND RESULTS: Two ECGs were obtained from each of 295 patients, one day apart, and separately from a further 364 patients, several minutes apart. All patients were considered to be in a stable condition. Estimates of the coefficients of variation were obtained for a number of ECG parameters used in the diagnosis of left ventricular hypertrophy. Corresponding reclassification rates of relevant ECG criteria were also calculated. Large coefficients of variation were observed in voltage parameters, e.g. R in V5 (20% for day-to-day recordings and 6% for minute-to-minute recordings) while the corresponding reclassification rates were 8% and 0% respectively. The repeat variation in the diagnosis of left ventricular hypertrophy was up to 5% for day-to-day recordings and up to 3% for minute-to-minute recordings based on several different criteria. CONCLUSION: A large coefficient of variation in a particular variable does not necessarily correspond to a high reclassification rate. A better measure of the impact of ECG variability for a particular measurement is obtained from its reclassification rate. In turn, this may have a minimal effect on the overall diagnosis of a particular abnormality.

Techniques for improving overall consistency of serial ECG analysis.

The techniques that improve the overall repeatability of computer interpretation of electrocardiograms (ECGs) that have been recorded several minutes apart from patients in a clinically stable condition are described. Estimates of the normal amounts of variability present in many ECG parameters that are used in the identification of a variety of cardiac abnormalities have been adopted in conjunction with smoothing techniques to form the basis of the new methodology. When applied to the Glasgow ECG analysis program, these new methods improve overall repeatability by about 31% when tested on a set of 263 pairs of ECGs. Randomly generated noise was added to the test set and an additional technique aimed at removing noise from the ECG tracings was used in conjunction with the smoothing methods. The observed improvement over the original repeatability was 63%.

Methods for improving the repeatability of automated ECG analysis.

Statistically-based smoothing techniques are described which have been applied to the existing framework of the Glasgow ECG Analysis program. These methods have been designed with the aim of improving repeatability in the computer interpretation of ECGs which have been recorded either several minutes or 24 hours apart from patients in a clinically stable condition. With respect to the ECG diagnosis of Left Ventricular Hypertrophy (LVH), these flexible methods have the effect to reducing the number of inconsistent day-to-day interpretations by 36% from 33 to 21 in 330 pairs of ECGs recorded one day apart. Similarly, when comparing agreement in the diagnosis of LVH in 249 pairs of ECGs which were recorded several minutes apart, the number of discordant computer interpretations was 6 using the new methodology, compared with 13 using conventional criteria, i.e. there was a 54% reduction in disagreements.

Effects of age, sex, and race on ECG interval measurements.

The effects of age, sex, and race on the electrocardiogram (ECG) were studied using three separate populations: a pediatric group of 1,782 neonates, infants, and children, and adult white group of 1,555 individuals, and an adult Chinese cohort of 503 individuals. All ECGs were processed using the same computer program, and various interval measurements were derived, including QRS duration, heart rate, QT dispersion, and selected Q-wave durations. Also, a small subgroup of 195 white subjects had a signal-averaged ECG recorded. In the pediatric group, there was a clear link between age and QRS duration, which increased linearly from about 1 year of age to adolescence. In the adults, the principal differences were an increased QRS duration in men compared with women both in the standard and signal-averaged ECG. Upper limits of normal heart rate also tended to be higher in women than in men in the two adult populations. Small racial differences could be seen in some measurements, but were not thought to be of clinical significance.

Smoothing techniques for improving the repeatability of the automated diagnosis of inferior myocardial infarction.

This study describes the implementation of novel techniques that have been designed with the aim of improving the repeatability of the diagnostic section of the Glasgow electrocardiographic (ECG) analysis program. Specific reference is made to the agreement in consecutive computer-assisted diagnoses of inferior myocardial infarction (IMI). Inherent repeat variation was estimated in ECG parameters of interest and used in conjunction with smoothing methods to produce a continuous Q-wave index ranging from 0 (no IMI) to 1 (IMI). A decision as to the presence or absence of IMI was then made on the basis of this smooth index. The sensitivity and specificity of the new approach remain unchanged from the conventional procedure when analyzing single ECGs. However, consistency in interpretation of day-to-day and minute-to-minute ECG interpretations was enhanced. Specific reference is made to the agreement between consecutive pairs of computer-assisted diagnoses of ECGs from the same patient with which one or both interpretations was that of IMI.

Improved repeatability of 12-lead ECG analysis using continuous scoring techniques.

This study describes a method for improving the day-to-day and minute-to-minute repeatability of the deterministic computer-assisted diagnosis of left ventricular hypertrophy. Conventional upper limits of normal for many age-dependent electrocardiographic parameters have been replaced by continuous equations, thereby, eliminating points of discontinuity that can contribute to lack of repeatability. Estimates of the normal amounts of variability present in many electrocardiographic parameters that are used in the diagnosis of left ventricular hypertrophy are calculated. These estimates are then used together with a smoothed version of a score function to form the basis of the new technique. The implementation of smoothing techniques enhances the repeatability of the Glasgow electrocardiographic analysis program. With respect to the electrocardiographic diagnosis of left ventricular hypertrophy, these methods eliminate 44% of the day-to-day and 50% of the minute-to-minute inconsistencies in computer reports.