A New 12-Lead ECG Prognostic Score.

BACKGROUND: The Diagonal Line Rule (DLR) is an educational pattern recognition tool for the classification of 12-lead electrocardiograms (ECGs) as normal or abnormal. OBJECTIVE: To develop a score using the DLR for the risk stratification of abnormal ECGs. METHODS: Patients at the Palo Alto, VA, referred for a routine resting ECG between 1987 and 1999 were retrospectively considered. The initial ECGs of 43,798 patients were scored according to the DLR. The main outcome variable was cardiovascular mortality with 8 years of follow-up. RESULTS: ECG abnormalities identified by the DLR were combined with age, gender, and ST depression to develop an additive score. The score was validated and shown to stratify levels of cardiac risk with a 0.78 area under the receiver operating characteristic (ROC) curve for identifying those who had a cardiovascular death. CONCLUSION: The score effectively stratifies ECGs for prediction of risk of cardiovascular death.

Resting ST amplitude: prognosis and normal values in an ambulatory clinical population.

BACKGROUND: There is limited data describing ST segment amplitude in apparently healthy, asymptomatic populations. We analyzed ST amplitude in the standard resting electrocardiogram (ECG) in a large, multiethnic, stable, clinical population. METHODS: We evaluated computerized ST amplitude measurements from the resting ECGs of 29,281 ambulatory outpatients collected between 1987 and 1999 at the Palo Alto, VA. With the PR interval as the isoelectric line, both elevation criteria (≥0.1 mV, ≥0.15 mV, and ≥0.2 mV) and depression criteria (≤-0.05 mV or ≤-0.1 mV), were applied. Cox-Hazard survival analysis techniques were used to demonstrate in which leads ST amplitude displacement was associated with cardiovascular (CV) death. To create a cohort without ECG patterns clearly associated with disease, we excluded ECGs with inverted T waves, wide QRS, or diagnostic Q waves and coded the remaining "normal" ECGs for ST elevation and depression to determine a normal range. RESULTS: The only ST amplitudes that were significantly and independently associated with time to CV death when adjusted for age, gender, and ethnicity were ST depression in all of the lateral leads (I, V4 -V6 ). When isolated to the inferior leads, (II and AVF), no ST amplitude criteria were associated with CV death. Among the "normal ECG" subgroup the precordial leads exhibited the greatest median ST amplitudes and the most significant differences between the leads, genders and ethnicities. CONCLUSIONS: Significant differences in ST amplitude were present in the precordial leads according to gender and ethnicity. This was particularly apparent when amplitude threshold were set for comparisons. Our findings provide the normal range for ST amplitude that when exceeded, should raise clinical concern.

The ageing athlete: screening prior to vigorous exertion in asymptomatic adults without known cardiovascular disease.

The exercise electrocardiogram (ECG) is widely considered the best available test for screening asymptomatic adults without known cardiovascular (CV) disease prior to initiating a vigorous exercise programme due to its prognostic value, widespread availability and low cost. Observational studies have demonstrated an increased relative risk of CV events with positive screening exercise ECG tests in men with diabetes, advanced age, or multiple cardiac risk factors. Recent observational studies have not demonstrated similar prognostic value for exercise ECG testing in asymptomatic healthy women. Despite the predictive ability of exercise ECG testing in several groups, there have been no studies demonstrating a significant impact of screening on morbidity and mortality in completely asymptomatic patients, leading to significant discordance in consensus guidelines on screening. One prospective observational study is ongoing in Italy that may for the first time demonstrate the ability to decrease incident CV events using preparticipation screening exercise ECG testing in adult athletes with targeted exclusion from athletics. Until more conclusive data is available the authors currently recommend screening exercise ECG testing in asymptomatic men with diabetes and asymptomatic men over age 45 with two or more CV risk factors prior to initiating a vigorous exercise programme. Consideration should also be given to screening asymptomatic patients younger than 45 with particularly strong risk factor exposure or elderly patients with fewer than two risk factors.

Prognostic value of the computerized ECG in Hispanics.

BACKGROUND: The prevalence and prognostic values of electrocardiogram (ECG) abnormalities in Hispanics have not been compared to other ethnicities in a large population. Despite a worse cardiovascular risk profile, the prevalence of cardiovascular disease is lower in Hispanics compared to non-Hispanics. HYPOTHESIS: We hypothesized that ECG abnormalities were less common in Hispanics and were not as strongly associated with cardiovascular mortality. METHODS: 45,563 ECGs ordered for usual clinical indications in a Veteran's hospital were available for analysis. 1,392 patients who died within one week of the ECG were excluded. Demographic characteristics were recorded and the population was followed for an average of 7.5 years using the California Death Index. The presence of baseline ECG characteristics were recorded and analyzed using the GE/Marquette computerized ECG system. Age, sex and heart rate adjusted Cox hazard ratio analyses were performed. RESULTS: Being Hispanic was associated with lower cardiovascular death, with a hazard ratio (HR) of 0.76 (95% CI 0.65-0.89). Findings such as atrial fibrillation, presence of Q-waves, left ventricular hypertrophy (LVH), upright T-waves in aortic valve replacement (aVR) and cardiac Infarction Injury Scores > 6 were significantly less prevalent in Hispanics than in non-Hispanics. These findings were similarly associated with increased cardiovascular mortality in both groups, each with a HR of approximately 2. CONCLUSION: The lower prevalence of ECG characteristics associated with coronary heart disease, atrial fibrillation and left ventricular hypertrophy support prior observations that cardiovascular disease is less prevalent in the Hispanic population. These findings, however, are similarly associated with increased mortality compared to non-Hispanics.

Exercise testing and training: clinical applications.

The application of exercise in clinical cardiology continues to progress because of research findings. Advances have occurred in the applications, methodology and interpretation of exercise testing. Exercise training has been documented to have a place in the primary prevention of coronary heart disease. In regard to cardiac rehabilitation, both early ambulation and early discharge are safe and beneficial in patients with uncomplicated infarction, and a subsequent exercise program is at least as effective as other interventions. High intensity exercise training in the patient with heart disease may be necessary to cause changes in myocardial perfusion and performance, but it carries an increased risk.

Screening for asymptomatic coronary artery disease.

Because it will be some time before the primary prevention of cardiovascular disease is a reality, it is advisable to evaluate screening methods for detecting latent cardiovascular disease. Because risk factor screening and techniques with the patient at rest have limited sensitivity, exercise testing that brings out abnormalities not present at rest deserves consideration. Numerous studies have shown the exercise electrocardiogram to have a sensitivity of approximately 50% and a specificity of 90%. The different reported predictive values are related to its use in populations with different prevalences of disease. Various techniques have been recommended to improve the sensitivity and specificity of exercise testing, including other exercise measurements, computerized probability estimates, nuclear cardiology, cardiokymography, cardiac fluoroscopy and risk factor analysis. There is promise that these techniques will improve attempts to screen asymptomatic subjects for coronary disease.

Spatial R wave amplitude changes during exercise: relation with left ventricular ischemia and function.

Thirty patients who exhibited increased and 65 patients decreased spatial R wave amplitude during exercise testing were compared for left ventricular function and ischemic variables. Spatial R wave amplitude was derived from the three-dimensional Frank X, Y, Z leads using computerized methods. All patients had stable coronary artery disease and they were classified into two groups: one that attained a higher (n = 48) and one a lower (n = 47) median value of maximal heart rate during exercise (161 beats/min). Within these two groups, patients with increasing or decreasing spatial R wave amplitude during exercise were analyzed for differences in oxygen consumption, exercise-induced changes in spatial R wave amplitude, ST segment depression laterally (ST60, lead X), ST displacement spatially, left ventricular ejection fraction at rest, change in left ventricular ejection fraction with exercise and thallium-201 ischemia during exercise. Significant differences were demonstrated only in exercise-induced spatial R wave amplitude changes (p less than 0.0001). There was no significant correlation between exercise-induced change in heart rate and change in spatial R wave amplitude in either the group with increasing or the group with decreasing spatial R wave amplitude. It is concluded that changes in spatial R wave amplitude during exercise are not related to ischemic electrocardiographic or thallium-201 imaging changes or to left ventricular ejection fraction determined at rest or during exercise.

Radionuclide imaging correlatives of heart rate impairment during maximal exercise testing.

A lower than normal heart rate response to maximal dynamic exercise, known as chronotropic incompetence or heart rate impairment, has been demonstrated to have a poor prognosis. In order to better describe patients with this finding, 156 men with coronary heart disease were evaluated. All patients were studied with maximal exercise testing, including measurements of oxygen consumption, exercise electrocardiograms, thallium scintigraphy and radionuclide ventriculography. Chronotropic incompetence was defined as a maximal heart rate 1 standard error of the estimate below the regression line of age versus maximal heart rate on two separate exercise tests. In patients so defined, mean maximal oxygen consumption was significantly lowered and angina was the major reason for stopping exercise on the treadmill. Patients with chronotropic incompetence not limited by angina had more evidence of myocardial scar and dysfunction and had a greater prevalence of three vessel coronary disease than did patients with a normal heart rate response. Radionuclide testing results suggest that among patients with chronotropic incompetence, those with angina have a better prognosis than those who do not have angina but who may have myocardial dysfunction.

The effect of resting ST segment depression on the diagnostic characteristics of the exercise treadmill test.

OBJECTIVES: The aim of this study is to demonstrate the effect of resting ST segment depression on the diagnostic characteristics of the exercise treadmill test. BACKGROUND: Previous studies evaluating the effect of resting ST segment depression on the diagnostic characteristics of exercise treadmill test have been conducted on relatively small patient groups and based only on visual electrocardiogram (ECG) analysis. METHODS: A retrospective analysis of data collected prospectively was performed on consecutive patients referred for evaluation of chest pain. One thousand two hundred eighty-two patients without a prior myocardial infarction underwent standard exercise treadmill tests followed by coronary angiography, with coronary artery disease defined as a 50% narrowing in at least one major epicardial coronary artery. Sensitivity, specificity, predictive accuracy and area under the curve of the receiver operating characteristic (ROC) plots were calculated for patients with and without resting ST segment depression as determined by visual or computerized analysis of the baseline ECG. RESULTS: Sensitivity of the exercise treadmill test increased in 206 patients with resting ST segment depression determined by visual ECG analysis compared with patients without resting ST segment depression (77 +/- 7% vs. 45 +/- 4%) and specificity decreased (48 +/- 12% vs. 84 +/- 3%). With computerized analysis, sensitivity of the treadmill test increased in 349 patients with resting ST segment depression compared with patients without resting ST segment depression (71 +/- 6% vs. 42 +/- 4%) and specificity decreased (52 +/- 9% vs. 87 +/- 3%) (p < 0.0001 for all comparisons). There was no significant difference in the area under the curve of the ROC plots (0.66-0.69) or the predictive accuracy (62-68%) between the four subgroups. CONCLUSIONS: The diagnostic accuracy and high sensitivity of the exercise treadmill test in a large cohort of patients with resting ST segment depression and no prior myocardial infarction support the initial use of the test for diagnosis of coronary artery disease. The classification of resting ST segment depression by method of analysis (visual vs. computerized) did not affect the results.

Noninvasive testing in the evaluation of myocardial ischemia: agreement among tests.

The purpose of this study was to investigate the relations among four exercise-induced phenomena--angina, ST segment depression, decrease in ejection fraction and thallium perfusion defects--and to determine their impact on aerobic capacity. One hundred fifty-six men (mean age 52 +/- 8 years) with documented coronary heart disease were studied with radionuclide ventriculography during supine bicycle exercise, thallium scintigraphy and treadmill testing with computerized electrocardiography and maximal oxygen uptake. Of 624 administered tests, 243 results (39%) were considered to indicate ischemia. The average number of abnormal tests was 1.6 per patient and, when considered as continuous variables, their results correlated poorly. Correlations did not improve when adjusting for heart rate achieved or by eliminating patients with coronary artery bypass surgery or myocardial infarction. Statistical methods of comparing degree of interest agreement yielded surprisingly weak relations among the four tests of ischemia. Treadmill performance was markedly impaired by angina, but much less impaired by other indicators of ischemia. It is concluded that the usual test responses implying ischemia have weak agreement when uniformly applied to patients with known coronary artery disease.

Limitations of electrocardiographic scoring systems for estimation of left ventricular function.

Four electrocardiographic scoring systems for the assessment of left ventricular function or presence of myocardial infarction were evaluated in 231 patients with coronary artery disease. Electrocardiographic scores were compared with radionuclide ejection fraction and thallium perfusion studies. The correlation between Wagner's modified QRS score and ejection fraction was only fair (r = -0.60). Askenazi's sum of R wave voltage score correlated poorly with ejection fraction (r = 0.44), as did Gottwik's sum of voltage score from the Frank lead electrocardiogram (r = 0.44). Rautaharju's Cardiac Infarction Injury Score did not reliably predict presence of infarction in the patient group, nor did it correlate well with ejection fraction (r = -0.49). None of the correlations were significantly improved when only patients with a history of a myocardial infarction, a thallium defect compatible with a scar or a diagnostic Q wave were considered. Although Wagner's QRS score correlated best with ejection fraction, all scoring systems had limited clinical usefulness for estimating ejection fraction.

Treadmill performance and cardiac function in selected patients with coronary heart disease.

To investigate the cardiac determinants of treadmill performance in patients able to exercise to volitional fatigue, 88 patients with coronary heart disease free of angina pectoris were tested. The exercise tests included supine bicycle radionuclide ventriculography, thallium scintigraphy and treadmill testing with expired gas analysis. The number of abnormal Q wave locations, ejection fraction, end-diastolic volume, cardiac output, exercise-induced ST segment depression and thallium scar and ischemia scores were the cardiac variables considered. Rest and exercise ejection fractions were highly correlated to thallium scar score (r = -0.72 to -0.75, p less than 0.001), but not to maximal oxygen consumption (r = 0.19 to 0.25, p less than 0.05). Fifty-five percent of the variability in predicting treadmill time or estimated maximal oxygen consumption was explained by treadmill test-induced change in heart rate (39%), thallium ischemia score (12%) and cardiac output at rest (4%). The change in heart rate induced by the treadmill test explained only 27% of the variability in measured maximal oxygen consumption. Myocardial damage predicted ejection fraction at rest and the ability to increase heart rate with treadmill exercise appeared as an essential component of exercise capacity. Exercise capacity was only minimally affected by asymptomatic ischemia and was relatively independent of ventricular function.

Failure of transdermal nitroglycerin to improve exercise capacity in patients with angina pectoris.

Sixteen patients with stable angina pectoris were studied in a double blind crossover manner utilizing treadmill exercise testing with the direct measurement of total body oxygen uptake, 1 and 24 hours after application of a 20 cm2 transdermal nitroglycerin system and identical placebo. Testing was performed after a 3 day lead-in period of treatment with either an active patch or placebo. Points of analysis were peak angina and the submaximal work load occurring at 4 minutes of exercise. No statistically significant differences were observed between nitroglycerin and placebo treatment in any of the rest hemodynamic or peak angina variables at 1 or 24 hours. A significant increase in the rate-pressure product at the submaximal work load was observed 1 hour after transdermal nitroglycerin relative to placebo application. However, no significant differences were observed in any of the other measured variables at the submaximal work load, 1 or 24 hours after nitroglycerin application. The once daily application of a 20 cm2 transdermal nitroglycerin system was ineffective in altering the exercise capacity of patients with angina pectoris. The lack of efficacy at 1 hour appears to be due to inadequate nitroglycerin blood levels; at 24 hours it may be due to tolerance.

Use of clinical data in predicting improvement in exercise capacity after cardiac rehabilitation.

Fifty-nine men with coronary heart disease underwent 1 year of supervised aerobic exercise. They performed exercise tests for maximal oxygen uptake, ST segment analysis, thallium scintigraphy and radionuclide ventriculography before and after the year of exercise. A computerized data base that included clinical descriptors and exercise test results was retrospectively reviewed to determine whether initial features could predict the patient's response to the exercise intervention. Poor correlations were found between the initial measurements and change in maximal oxygen consumption and other indexes of training effect. Patients who initially were in the poorest state of fitness showed the most improvement with training. None of the initial features from the history and physical examination, treadmill study or radionuclide studies was a good predictor of a beneficial result from the exercise program. The usual measurements of work intensity during training were poor predictors of outcome. A significant decrease in the amount of ischemia measured by thallium perfusion scintigraphy was demonstrated after training.

Does the rest electrocardiogram after myocardial infarction determine the predictive value of exercise-induced ST depression? A 2 year follow-up study in a veteran population.

The failure of exercise-induced ST segment depression to consistently predict prognosis in patients after myocardial infarction could be a result of population differences and the rest electrocardiogram (ECG). These hypotheses were tested by studying 198 veterans who survived a myocardial infarction, underwent a submaximal predischarge treadmill exercise test and were followed up for cardiac events for 2 years. During the 2 years, 29 deaths, 19 reinfarctions and 28 revascularization procedures were documented. The prevalence of death or reinfarction was two times higher in patients who had exercise-induced ST depression than in patients who did not. However, in the 55 patients without Q waves, the risk increased to 11 times for an abnormal ST response. These findings suggest that exercise-induced ST depression only predicts high risk in patients after myocardial infarction whose ECG at rest does not exhibit Q waves and that differences in the prevalence of rest ECG patterns are the most likely explanation for the failure of agreement among prior studies.

Increased exercise capacity after digoxin administration in patients with heart failure.

Failure to objectively assess the effect of digitalis on exercise capacity has resulted in controversy regarding its use in patients with chronic congestive heart failure. To clarify this situation, maximal treadmill testing with respiratory gas exchange analysis was performed on 11 patients (mean age 57 +/- 9 years) with chronic congestive heart failure with and without digoxin therapy. Ten of the 11 had a consistent third sound gallop, and the mean ejection fraction of the group was 24 +/- 10%. Rest heart rate was significantly higher (91 +/- 16 versus 102 +/- 16 beats/min; p less than 0.05) and rest systolic blood pressure was significantly reduced in the absence of digoxin (130 +/- 23 versus 121 +/- 15 mm Hg; p less than 0.05). No differences in heart rate or blood pressure were observed during exercise. Significant increases in ventilatory oxygen uptake were observed with digoxin submaximally (3.0 mph, 0% grade), at the gas exchange anaerobic threshold and at maximal exercise (mean increase of 2.6 ml/kg per min; p less than 0.02). An improvement in the estimated ratio of ventilatory dead space to tidal volume (VD/VT), an index of physiologic efficiency, occurred throughout exercise during digoxin therapy, and there was a significant negative correlation between the change in maximal oxygen uptake and change in maximal estimated VD/VT (r = -0.63; p less than 0.05). Thus, digoxin therapy is associated with a significant improvement in exercise capacity in patients with chronic heart failure, most likely due to an improved matching of ventilation to perfusion.

A randomized trail of the effects of 1 year of exercise training on computer-measured ST segment displacement in patients with coronary artery disease.

As part of a randomized trial of the effects of 1 year of exercise training on patients with stable coronary artery disease, 48 patients who exercised and 59 control patients had computerized exercise electrocardiography performed initially and 1 year later. The patients who had exercise training as an intervention had a 9% increase in measured maximal oxygen consumption and significant decreases in heart rate at rest and during submaximal exercise. ST segment displacement was analyzed 60 ms after the end of the QRS complex in the three-dimensional X, Y and Z leads and utilizing the spatial amplitude derived from them. Statistical analysis by t testing yielded no significant differences between the groups except for less ST segment displacement at a matched work load, but this could be explained by a lowered heart rate. Analysis of variance yielded some minor differences within clinical subgroups, particularly in the spatial analysis. Obvious changes in exercise-induced ST segment depression could not be demonstrated in this heterogeneous group of selected volunteers with coronary artery disease secondary to an exercise program.

Heart rate recovery: validation and methodologic issues.

OBJECTIVES: The goal of this study was to validate the prognostic value of the drop in heart rate (HR) after exercise, compare it to other test responses, evaluate its diagnostic value and clarify some of the methodologic issues surrounding its use. BACKGROUND: Studies have highlighted the value of a new prognostic feature of the treadmill test-rate of recovery of HR after exercise. These studies have had differing as well as controversial results and did not consider diagnostic test characteristics. METHODS: All patients were referred for evaluation of chest pain at two university-affiliated Veterans Affairs Medical Centers who underwent treadmill tests and coronary angiography between 1987 and 1999 as predicted after a mean seven years of follow-up. All-cause mortality was the end point for follow-up, and coronary angiography was the diagnostic gold standard. RESULTS: There were 2,193 male patients who had treadmill tests and coronary angiography. Heart rate recovery at 2 min after exercise outperformed other time points in prediction of death; a decrease of <22 beats/min had a hazard ratio of 2.6 (2.4 to 2.8 95% confidence interval). This new measurement was ranked similarly to traditional variables including age and metabolic equivalents but failed to have diagnostic power for discriminating those who had angiographic disease. CONCLUSIONS: Heart rate at 1 or 2 min of recovery has been validated as a prognostic measurement and should be recorded as part of all treadmill tests. This new measurement does not replace, but is supplemental to, established scores.

Comparison of the ramp versus standard exercise protocols.

To compare the hemodynamic and gas exchange responses of ramp treadmill and cycle ergometer tests with standard exercise protocols used clinically, 10 patients with chronic heart failure, 10 with coronary artery disease who were asymptomatic during exercise, 11 with coronary artery disease who were limited by angina during exercise and 10 age-matched normal subjects performed maximal exercise using six different exercise protocols. Gas exchange data were collected continuously during each of the following protocols, performed on separate days in randomized order: Bruce, Balke and an individualized ramp treadmill; 25 W/stage, 50 W/stage and an individualized ramp cycle ergometer test. Maximal oxygen uptake was 16% greater on the treadmill protocols combined (21.4 +/- 8 ml/kg per min) versus the cycle ergometer protocols combined (18.1 +/- 7 ml/kg per min) (p less than 0.01), although no differences were observed in maximal heart rate (131 +/- 24 versus 126 +/- 24 beats/min for the treadmill and cycle ergometer protocols, respectively). No major differences were observed in maximal heart rate or maximal oxygen uptake among the various treadmill protocols or among the various cycle ergometer protocols. The ratio of oxygen uptake to work rate, expressed as a slope, was highest for the ramp tests (slope +/- SEE ml/kg per min = 0.80 +/- 2.5 and 0.78 +/- 1.7 for ramp treadmill and ramp cycle ergometer, respectively). The slopes were poorest for the tests with the largest increments in work (0.62 +/- 4.0 and 0.59 +/- 2.8 for the Bruce treadmill and 50 W/stage cycle ergometer, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Exercise-induced silent ischemia: age, diabetes mellitus, previous myocardial infarction and prognosis.

The purposes of this study were 1) to determine the prognosis of silent ischemia in an unselected group of patients referred for exercise testing, and 2) to assess whether age or the presence of myocardial infarction or diabetes mellitus influences the prevalence of silent myocardial ischemia during exercise testing. The design was retrospective, with a 2 year mean follow-up period. The study group consisted of 1,747 predominantly male in-patients and outpatients referred for exercise testing at a 1,200 bed Veterans Administration hospital. The main result was that the mortality rate was significantly greater (p = 0.02) among patients with abnormal ST segment depression than in patients without ST depression. The presence or absence of angina pectoris during exercise testing was not significantly related to death. The prevalence of silent ischemia was not significantly different among patients categorized according to myocardial infarction or diabetes mellitus status, but was directly related to age. It is concluded that, in patients with an ischemic ST response to exercise testing, the presence or absence of angina pectoris during the test does not alter the risk of death. The prevalence of silent ischemia during exercise testing is not statistically different among patients with recent, past or no myocardial infarction or with insulin-dependent or noninsulin-dependent diabetes mellitus.