P4419The association between ECG voltage and left-ventricular mass, sex, body size and the distance between the heart and chest wall in college athletes

Background

The ECG is widely used in pre-participation evaluation (PPE) of athletes (ATH). While it is assumed that greater than normal QRS voltages reflect physiologically increased left ventricular mass (LVM), this has not been adequately demonstrated in ATH.

Purpose

To examine the relation between QRS voltage on surface ECG and LVM and explore if the distance from the chest wall to mid-LV (CWLVdis) affects QRS voltage in ATH.

Methods

We examined digitized ECG data and echocardiograms in college ATH, obtained as part of routine PPE in years 2010–16. ECG parameters included R and S-wave voltage components of the Sokolow-Lyon (S-L) and Cornell criteria for LV hypertrophy (i.e. SV1 + RV5-V6 and RaVL + SV3, respectively). Transthoracic 2D echocardiography was used to determine LVM (area-length method) and the CWLVdis (detailed in Fig1A). S-L positive (SV1 + RV5-V6 >35 mV or RaVL >11 mV) ATH were compared to S-L negative by t-test, and univariate correlation and multivariable regression analysis was used to explore independent effects of body characteristics, sex, LVM and CWLVdis on QRS voltage.

Results

Included were 227 ATH (age 18.6±0.7 yr; 85% male; 60%/33% Caucasian/Afro-american). Of these, 66% played American football, 18% volleyball and 16% basketball.

Overall, mean LVM was 174±37 g (range 96–284 g), and BSA-indexed LVM was 78±12 g/m2 (range 49–108 g/m2). Mean CWLVdis was 8.5±1.1 cm (range 5.6–11.3 cm) and was greater in males (p<0.001, Fig1B).

Forty-six ATH (24%, all male) were S-L positive and no ATH were positive according to Cornell criteria. S-L positive ATH had lower BMI (25.3±3.5 vs 26.9±4.9, p=0.012), greater absolute LVM (189.1±31.3 vs. 170.1±37.4 g, p=0.002) and greater BSA-indexed LVM (85.3±10.3 vs. 76.6±11.7 g/m2, p<0.001) than S-L negative ATH. The CWLVdis was similar between S-L positive and negative ATH (8.4±1.2 vs. 8.6±1.1, respectively, p=0.213).

CWLVdis was more strongly correlated to body mass (r=0.73, p<0.001, Fig. 1C) than to height (r=0.34, p<0.001). LVM correlated weakly to ECG voltage as combined in the S-L or Cornell criteria (Fig. 1C). CWLVdis was weakly correlated with R in aVL, V5 and V6 (r=0.21, 0.16 and 0.16, all p<0.02).

In multivariate analysis, male sex (β=0.31), LVM (β=0.45) and body mass index (β=-0.37) were independently associated with the S-L summed voltage (R2 0.26, p<0.001). For Cornell summed voltage, only sex was an independent predictor (β=0.48, R2 0.22, p<001).

Figure 1

Conclusion

The R and S wave ECG amplitudes used in the two most common ECG criteria for LV hypertrophy were weakly related in the highest to lowest order to sex, LVM, body size and the distance from the LV to the chest wall in our college ATH.

Does exercise protect from coronary artery disease?

New studies support a lifestyle of regular physical activity. Regular physical activity most likely decreases one's risk for coronary heart disease and helps to decrease other risk factors. The inclusion of regular moderate exercise in one's life-style makes good sense for many reasons. It can improve the quality of life by avoiding illness and the quality is definitely improved in those in whom physical performance is important. Some say that physical exercise will increase the quantity of life but the extra years gained are spent exercising.

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.

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.

Homocysteine and hypertension in persons with spinal cord injury

STUDY DESIGN

Cross-sectional analysis of a convenience sample of locally recruited participants, including both patients and volunteers.

OBJECTIVES

To determine whether there is an association between plasma homocysteine and hypertension in persons with spinal cord injury (SCI).

SETTING

Spinal Cord Injury Service of the Veterans Affairs Palo Alto Medical Center (California, United States of America).

METHODS

The incidence of hypertension, dyslipidemia, insulin resistance, and the presence of metabolic syndrome were determined in 168 individuals with SCI (mean age 50.2 +/- 12.8 years). Fasting lipids, insulin, glucose, plasma homocysteine, and anthropometric data was gathered for each subject.

RESULTS

Blood pressure values (P < 0.001) and mean arterial pressure (P < 0.05) increased with higher plasma homocysteine levels. Homocysteine values were also significantly greater among individuals with hypertension compared with those who were normotensive or prehypertensive (P < 0.0001). There was an inverse relationship between plasma homocysteine levels and glomerular filtration rate and effective renal plasma flow (P < 0.05).

CONCLUSIONS

Plasma homocysteine levels are elevated in persons with SCI who have hypertension and inversely related to renal function, which suggests that renal dysfunction may be a link between homocysteine and hypertension in persons with SCI.

SPONSORSHIP

Funded by the VA Rehabilitation Research and Development Service, Merit Review Grant #B2549R.

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.

Clinical and exercise test predictors of all-cause mortality: results from > 6,000 consecutive referred male patients

OBJECTIVE

To report the prevalence of abnormal treadmill test responses and their association with mortality in a large consecutive series of patients referred for standard exercise tests, with testing performed and reported in a standardized fashion.

BACKGROUND

Exercise testing is widely performed, but few databases exist of large numbers of consecutive tests performed on patients referred for routine clinical purposes using standardized methods. Even fewer of the available databases have information regarding all-cause mortality as an outcome.

METHODS

All patients referred for evaluation at two university-affiliated Veterans Affairs medical centers who underwent exercise treadmill testing for clinical indications between 1987 and 2000 were determined to be dead or alive using the Social Security death index after a mean 6.2 years (median, 7 years) of follow-up. Clinical and exercise test variables were collected prospectively according to standard definitions; testing and data management were performed in a standardized fashion using a computer-assisted protocol. All-cause mortality was utilized as the end point for follow-up. Standard survival analysis was performed, including Kaplan-Meier curves and a Cox hazard model.

RESULTS

There were 6,213 male patients (mean +/- SD age, 59 +/- 11 years) who underwent standard exercise ECG treadmill testing over the study period with a mean follow-up duration of 6.2 +/- 3.7 years. There were no complications of testing in this clinically referred population, 78% of whom were referred for chest pain, or risk factors or signs or symptoms of ischemic heart disease. Overlapping thirds had typical angina or history of myocardial infarction (MI). Five hundred seventy-nine patients had prior coronary artery bypass surgery, and 522 patients had a history of congestive heart failure (CHF). Indications for testing were in accordance with published guidelines. Twenty percent died over the follow-up period, for an average annual mortality rate of 2.6%. Cox hazard function chose the following variables in rank order as independently and significantly associated with time to death: exercise capacity (metabolic equivalents < 5, age > 65 years, history of CHF, and history of MI. A score based on these variables (summing up the four variables [if yes = 1 point]) classified patients into low-risk, medium-risk, and high-risk groups. The high-risk group (score > or = 3) has a hazard ratio of 5.0 (95% confidence interval, 4.7 to 5.3) and a 5-year mortality rate of 31%.

CONCLUSION

This comprehensive analysis provides rates of various abnormal responses that can be expected in patients referred for exercise testing at a typical medical center. Four simple variables combined as a score powerfully stratified patients according to prognosis.

Clinical utility of the exercise ECG in patients with diabetes and chest pain

OBJECTIVE

The purpose of this study was to determine the characteristics of exercise treadmill testing in diabetic patients presenting with chest pain.

BACKGROUND

The diagnosis of coronary artery disease (CAD) in diabetic patients is confounded by different manifestations of coronary disease than are seen in the general population. Because of the association of diabetes with accelerated CAD, it is critical to assess the diagnostic utility of the standard exercise test in diabetic patients with chest pain.

METHODS

This study was a retrospective analysis of standard exercise test results in 1,282 male patients without prior myocardial infarction who had undergone coronary angiography and were being evaluated for possible CAD at two Veterans' Administration institutions.

RESULTS

In patients with diabetes, 38% had an abnormal exercise test result, and the prevalence of angiographic CAD was 69%; the sensitivity of the exercise test was 47% (95% confidence interval [CI], 41 to 58), and specificity was 81% (95% CI, 68 to 89). In patients without diabetes, 38% had an abnormal exercise test result, and the prevalence of angiographic CAD was 58%; the sensitivity of the exercise test was 52% (95% CI, 48 to 56), and specificity was 80% (95% CI, 76 to 83). The receiver operating characteristic curves were also similar in both diabetic and nondiabetic patients (0.67 and 0.68, respectively).

CONCLUSION

These data demonstrate that the standard exercise test has similar diagnostic characteristics in diabetic as in nondiabetic patients.

Diagnostic exercise tests on 4000 consecutive men

OBJECTIVE

Our purpose was to report the prevalence of abnormal treadmill test responses and their association with mortality in a large consecutive series of patients referred for standard diagnostic exercise tests, with testing performed and reported in a standardized fashion.

BACKGROUND

Exercise testing is widely performed, but an analysis of responses has not been presented for a large number of consecutive tests performed on patients referred for diagnosis of cardiac disease.

METHODS

All patients referred for evaluation at 2 university-affiliated Veterans Affairs Medical Centers who underwent exercise treadmill tests for clinical indications between 1987 and 2000 were determined to be dead or alive according to the Social Security Death Index after a mean 5.9-year follow-up. Patients with established heart disease (ie, prior coronary bypass surgery, myocardial infarction, or congestive heart failure) were excluded from analyses. Clinical and exercise test variables were collected prospectively according to standard definitions; testing and data management were performed in a standardized fashion with a computer-assisted protocol. All-cause mortality was used as the end point for follow-up. Standard survival analysis was performed, including Kaplan-Meier curves and a Cox hazard model.

RESULTS

After the exclusions, 3974 men (mean age 57.5 +/- 11 years) had standard diagnostic exercise testing over the study period with a mean of 5.9 (+/-3.7) years of follow-up (64% of all tested). There were no complications of testing in this clinically referred population, 82% of whom were referred for chest pain, risk factors, or signs and symptoms of ischemic heart disease. Five hundred forty-nine (14%) had a history of typical angina. Indications for testing were in accordance with published guidelines. A total of 545 died, yielding an annual mortality rate of 1.8%. The Cox hazard model chose the following variables in rank order as independently associated with time to death: change in rate pressure product, age greater than 65 years, METs less than 5, and electrocardiographic left ventricular hypertrophy. A score based on these variables classified patients into low-, medium-, and high-risk groups. The high-risk group with a score greater than 3 has a hazard ratio of 4 (95% confidence interval 3.82-4.27) and an annual mortality rate of 4%.

CONCLUSION

This comprehensive analysis provides rates of various abnormal responses that can be expected in men referred for diagnostic exercise testing at typical Veterans Administration Medical Centers. Four simple variables combined as a score predict all-cause mortality after clinical decisions for therapy are prescribed.

Effects of chronotropic incompetence and beta-blocker use on the exercise treadmill test in men

OBJECTIVE

Our purpose was to assess the diagnostic characteristics of the exercise test in patients who fail to reach conventional target heart rates and in patients on beta-blockers.

BACKGROUND

Exercise test results are often considered "inadequate" or "nondiagnostic" in patients taking beta-blockers and in patients who do not achieve 85% of their age-predicted maximal heart rate.

METHODS

The results of exercise tests and coronary angiography performed to evaluate chest pain in 1282 male patients without a prior history of myocardial infarction, coronary revascularization, diagnostic Q wave on the baseline electrocardiogram, or previous cardiac catheterization were analyzed with respect to beta-blocker exposure and failure to reach 85% age-predicted maximal heart rate. Sensitivity, specificity, and predictive accuracy of exercise testing, as well as area under the curve for the receiver operating characteristic plots were calculated for these subgroups with use of coronary angiography as the reference. The angiographic criterion for significant coronary artery disease was 50% narrowing or greater in one or more major coronary arteries.

RESULTS

The population was divided into 4 exclusive groups on the basis of whether they reached their target heart rates and whether they were receiving beta-blockers. Sixty to 40 percent of this clinical population failed to reach target heart rate, of which 24% (n = 303) were receiving beta-blockers and 40% (n = 518) were not. The group of patients who reached target heart rate and were not taking beta-blockers was taken as the reference group (n = 409). The group of patients supposedly beta-blocked but who reached the target heart rate (n = 52) had hemodynamic and test characteristics similar to those of the reference group and most likely were not taking their beta-blockers or were not adequately dosed. The prevalence of angiographic coronary disease was significantly higher in the 2 groups failing to reach target heart rate, both in the presence and absence of beta-blockers, compared with the reference group (68% and 64%, respectively, vs 49%, P <.01). Although the areas under the curve of the receiver operating characteristic curves for ST depression of the groups failing to reach target heart rate were not significantly different from the reference group, the predictive accuracy and sensitivity were significantly lower for 1 mm of ST depression in the beta-blocked group who did not reach target heart rate (predictive accuracy of 56% vs 67%, sensitivity of 44% vs 58%, P <.01). The only way to maintain sensitivity with the standard exercise test in the beta-blocker group who failed to reach target heart rate was to use a treadmill score or 0.5-mm ST depression as the criteria for abnormal.

CONCLUSION

Sensitivity and predictive accuracy of standard ST criteria for exercise-induced ST depression are significantly decreased in male patients who are taking beta-blockers and do not reach target heart rate. In those who fail to reach target heart rate and are not beta-blocked, sensitivity and predictive accuracy are maintained.

Simple treadmill score to diagnose coronary disease

OBJECTIVE

Our aim was to derive and validate a simplified treadmill score for predicting the probability of angiographically confirmed coronary artery disease (CAD).

BACKGROUND

The American College of Cardiology/American Heart Association guidelines for exercise testing recommend the use of multivariable equations to enhance the diagnostic characteristics of the standard treadmill test. Most of these equations use complicated statistical techniques to provide diagnostic estimates of CAD. Simplified scores derived from such equations that require physicians only to add points have been developed for pretest estimates of disease and for prognosis. However, no simplified score has been developed specifically for the diagnosis of CAD using exercise test results.

METHODS

Consecutive patients referred for evaluation of chest pain who underwent standard treadmill testing followed by coronary angiography were studied. A logistic regression model was used to predict clinically significant (> or = 50% stenosis) CAD and then the variables and coefficients were used to derive a simplified score. The simplified score was calculated as follows: (6 x maximal heart rate code) + (5 x ST-segment depression code) + (4 x age code) + angina pectoris code + hypercholesterolemia code + diabetes code + treadmill angina index code. The simplified score had a range from 6 to 95, with < 40 designated as low probability, between 40 and 60 was intermediate probability, and > 60 was high probability for CAD.

RESULTS

A total of 1,282 male patients without a prior myocardial infarction underwent exercise treadmill testing and coronary angiography in the derivation group, and there were 476 male patients in the validation group from another institution. The area under the receiver operating characteristic curve (+/- SE) for the ST-segment response alone was 0.67 as compared to 0.79 +/- 0.01 for the diagnostic score (p > 0.001). The prevalence of significant disease for the men was 27% in the low-probability group, 62% in the intermediate-probability group, and 92% in the high-probability group, which was similar to the prevalence in the validation group, with 22%, 58%, and 92% in low-, intermediate-, and high-probability groups, respectively. The low-probability group had < 4% prevalence of severe disease. In both populations, 7 more patients out of 100 were correctly classified than with the use of ST-segment criteria. When used as a clinical management strategy, the score has a sensitivity of 88% and a specificity of 96%.

CONCLUSION

This simplified exercise score that estimates the probability of CAD can be easily applied without a calculator and is a useful and valid tool that can help physicians manage patients presenting with chest pain.

Exercise testing in the new millennium

In the changing economic times, internists and family physicians are becoming the main performers of the standard exercise test. The education of those noncardiologists who wish to perform exercise testing is quite important. In the new millennium, the American College of Cardiology/American Heart Association evidence-based guidelines on exercise testing continue to have a large impact. Used for diagnosis or prognosis, exercise scores such as the Duke exercise score will be applied to each test. Increased computerization and the internet will bring inexpensive web-enabled devices for sophisticated exercise testing into the doctor's office and allow remote over-reading services.

Computer applications in the interpretation of the exercise electrocardiogram

The exercise electrocardiogram remains the noninvasive diagnostic test of first choice in patients with coronary artery disease. While new technology offers novel diagnostic possibilities and the ability to assess patients unsuitable for exercise testing, no other investigation has to this point furnished the quality of functional information and value-for-predictive accuracy of exercise electrocardiography. In this article, we describe how this central position in the work up of the cardiac patient has been secured through the evolution of the microprocessor. Particularly important has been its ability to harness and present large volumes of raw data, to derive and manipulate multivariate equations for diagnostic prediction, and to run 'expert' systems which can pool demographic and exercise test data, calculate risk scores, and prompt the nonexpert with advice on current management. These key features explain the pivotal role of the exercise test in the diagnostic, and increasingly prognostic, armoury of the cardiovascular clinician.

A survey of exercise testing: methods, utilization, interpretation, and safety in the VAHCS

BACKGROUND

Healthcare organizations are being graded in terms of their adherence to practice guidelines. The authors sought information on practice patterns of exercise testing within the Veterans Affairs Health Care System (VAHCS) to determine how well current practice patterns adhere to current guidelines. In addition, we sought to update past surveys to determine methods, indications, utilization of alternative diagnostic modalities, criteria for interpretation, safety, and physician supervision of exercise testing within the VAHCS.

METHODS

Questionnaires were sent to 72 of the largest Veterans Affairs Medical Centers with cardiology divisions. The centers were queried regarding volume and type of exercise testing (standard, nuclear, and echocardiographic), indications, safety, protocols used, and criteria for interpretation.

RESULTS

Seventy-one questionnaires were returned, comprising a total of 75,828 exercise tests performed within the last year. Virtually all indications for exercise testing fit the American Heart Association/American College of Cardiology (AHA/ACC) guidelines Class I criteria; 46% of patients were tested for the evaluation of chest pain; 14% were tested to evaluate patients at high risk for coronary artery disease; 10% were preoperative evaluations; and 8% were post-myocardial infarction evaluations. The most commonly used diagnostic test was the standard exercise electrocardiogram; a patient was five times more likely to undergo a standard exercise electrocardiogram or nuclear exercise test than an exercise or pharmacologic echocardiogram. The largest proportion of centers (49%) used 1.0-mm horizontal or downsloping ST depression as a criterion for an abnormal test, although 22% considered 1.5-mm upsloping ST depression to be abnormal, and 25% relied on a treadmill score. Seventy-eight percent of respondents used the treadmill, and of these, 82% used the Bruce or modified Bruce protocol. Four major cardiac events were reported (three myocardial infarctions, one sustained ventricular tachycardia) representing an event rate of 1.2/10,000. A physician was present during 73% of all standard exercise tests; 21% of respondents reported that a physician was required to be present "only for high-risk patients."

CONCLUSION

Indications for exercise testing are in close agreement with the AHA/ACC guidelines; thus, the test continues to have an important role in diagnosis and prognosis among patients with or suspected of having coronary artery disease. The exercise test is an extremely safe procedure, with an event rate similar to other recent surveys. However, a great deal of variation exists in terms of criteria for abnormal results and whether physician presence is required during exercise testing.

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.

Does elevated cardiac troponin I in patients with unstable angina predict ischemia on stress testing?

To help guide physicians in their evaluation of patients with acute coronary syndromes, we investigated whether elevated cardiac troponin I in patients presenting with unstable angina predicts ischemia on stress testing. Elevated cardiac troponin I in patients who present with chest pain and normal creatine kinase levels is associated with ischemia on stress testing, as well as with future cardiac events.

The electrocardiographic exercise test in a population with reduced workup bias: diagnostic performance, computerized interpretation, and multivariable prediction. Veterans Affairs Cooperative Study in Health Services #016 (QUEXTA) Study Group. Quantitative Exercise Testing and Angiography

BACKGROUND

Empirical scores, computerized ST-segment measurements, and equations have been proposed as tools for improving the diagnostic performance of the exercise test.

OBJECTIVE

To compare the diagnostic utility of these scores, measurements, and equations with that of visual ST-segment measurements in patients with reduced workup bias.

DESIGN

Prospective analysis.

SETTING

12 university-affiliated Veterans Affairs Medical Centers.

PATIENTS

814 consecutive patients who presented with angina pectoris and agreed to undergo both exercise testing and coronary angiography.

MEASUREMENTS

Digital electrocardiographic recorders and angiographic calipers were used for testing at each site, and test results were sent to core laboratories.

RESULTS

Although 25% of patients had previously had testing, workup bias was reduced, as shown by comparison with a pilot study group. This reduction resulted in a sensitivity of 45% and a specificity of 85% for visual analysis. Computerized measurements and visual analysis had similar diagnostic power. Equations incorporating nonelectrocardiographic variables and either visual or computerized ST-segment measurement had similar discrimination and were superior to single ST-segment measurements. These equations correctly classified 5 more patients of every 100 tested (areas under the receiver-operating characteristic curve, 0.80 for equations and 0.68 for visual analysis; P < 0.001) in this population with a 50% prevalence of disease.

CONCLUSIONS

Standard exercise tests had lower sensitivity but higher specificity in this population with reduced work-up bias than in previous studies. Computerized ST-segment measurements were similar to visual ST-segment measurements made by cardiologists. Considering more than ST-segment measurements can enhance the diagnostic power of the exercise test.

Relationship of left ventricular structure to maximal heart rate during exercise

Previous investigators using clinical, hemodynamic, or exercise parameters to predict maximal exercise heart rate (HRmax) have demonstrated age to be the major determinant. Regression coefficients have ranged from -0.3 to -0.6, leaving approximately two thirds of the variance in HRmax unexplained. Because cardiac size and function are directly related to stroke volume and should influence HRmax, we studied 114 male subjects (aged 19 to 73 years) with two-dimensional and M-mode echocardiography who underwent maximal treadmill testing with respiratory gas analysis. Seventy-three were normotensive (diastolic BP < 95 mm Hg) and 41 were hypertensive. As in previous studies, HRmax was inversely related to age (HRmax = 199-0.63[age], r = -0.47, p < 0.001). M-mode left ventricular (LV) diastolic dimension (LVD) added significantly to the explanation of the variance in HRmax (r = -0.57, p < 0.001) (HRmax = 236 - 0.72 [age]-6.8 [LVD]). Thus, the larger the heart, the lower the HRmax. No other echocardiographic measurement or derived parameter added significantly to the explanation of the variance in HRmax. To evaluate the effects of hypertension on HRmax, we studied hypertensives and normotensives separately. Only age was significantly related to HRmax in the normotensives (r = -0.50, p < 0.001). In the hypertensive subjects, however, both age and relative wall thickness (RWT) (which describes LV wall thickness in relation to LV chamber size) were significantly related to HRmax. Age explained 45% of the observed variance in HRmax (r = 0.67, p < 0.001) and RWT added modestly (9%) but significantly to the relationship (HRmax = 173-0.96[age]+94 [RWT], p < 0.001), together explaining 54% of the variance observed in HRmax. Thus, HRmax is inversely related to LVD and patients with larger ventricles achieve lower HRmax. In hypertensives, the amount of LV muscle mass in relation to chamber size is an additional predictor of HRmax. However, despite controlling for age, sex, and cardiovascular disease, and the inclusion of echocardiographic indices of cardiac size and function, a large portion of the variance in HRmax could not be explained. The unexplained variance in HRmax is most likely due to intersubject variability in resting cardiac size, volume, function, and other as yet undefined factors.

Exercise capacity and prognosis in patients with chronic atrial fibrillation

To evaluate the response of patients with chronic atrial fibrillation (AF) to exercise and to demonstrate if prognosis could be predicted, 200 male patients (64 +/- 1 years) with AF were identified retrospectively who underwent resting echocardiography and symptom-limited treadmill testing. They were classified by underlying disease into three subgroups: hypertension or no underlying disease (LONE; n = 102), ischemic heart disease (IHD; n = 45) and history of congestive heart failure or valvular disease (CHF-VD; n = 53). Maximal exercise capacities for LONE, IHD and CHF-VD were (mean +/- 1 SEM) 8.0 +/- 0.3, 6.4 +/- 0.4 and 6.0 +/- 0.3 metabolic equivalents, respectively (p < 0.01), and resting left ventricular ejection fractions were 61.7 +/- 1.6, 60.1 +/- 2.2 and 49.5 +/- 1.9%, respectively (p < 0.01). Stepwise multiple regression analysis demonstrated that, except for group classification (R2 = 0.13, p < 0.01), no clinical, exercise or morphologic variables could predict exercise capacity. After a mean 39.1-month follow-up (range 1-78), 17 of the 200 had died from cardiovascular causes. The rate of cardiac death using Kaplan-Meier survival analysis was significantly greater in CHF-VD patients (p < 0.01). However, Cox hazard function and Kaplan-Meier survival analysis demonstrated that neither echocardiographic measurements of cardiac size or function at rest, nor exercise or clinical variables were significant predictors of outcome. AF patients with a history of CHF and/or VD demonstrated a reduced exercise tolerance ad a worse prognosis than those without morphologic heart disease or those with IHD.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical and exercise test markers of prognosis in patients with stable coronary artery disease

Current management of coronary artery disease has taken a very aggressive approach in which cardiac catheterization plays a prominent role in patient evaluation and in which bypass and angioplasty are commonly used for therapy. The number of cardiac catheterizations and procedures, not surprisingly, have grown in tandem because angiography provides anatomic information that becomes the substrate for justifying interventions. Bypass surgery has been shown to confer a survival benefit compared with medical therapy in patients with multiple-vessel disease and left ventricular dysfunction, but it also is still used in other patient populations with equivocal indications. Comparison studies of percutaneous transluminal coronary angioplasty with medical management have indicated a slight advantage with percutaneous transluminal coronary angioplasty in limiting symptoms, but no evidence yet supports its survival benefit. Angioplasty, however, has become much more common in the last decade, particularly as the initial revascularization technique. Because cardiac catheterization is frequently the nodal branch point between invasive and noninvasive (i.e., medical) management, its application should be limited to high-risk candidates who would receive a survival benefit from these procedures or to those with intractable symptoms. Those who propose that catheterization is the best method for risk stratification argue that noninvasive testing requires physiologically significant disease and that morbid or fatal events can occur with rapid progression of minimal disease. From the studies reviewed, however, the extent of coronary angiographic disease is not clearly predictive of future cardiovascular events. Although some studies found the number of diseased vessels to be independent prognostic variables, most found that it did not add any additional prognostic information beyond that provided from noninvasive testing. Furthermore, there has been an argument that silent ischemia puts patients at higher risk of sudden death or infarction, and these patients need to be catheterized. However, numerous studies have shown that this concern is exaggerated. The studies reviewed found that except for patients with diabetes, those with "silent" or painless exercise-induced ST depression do not have a worse prognosis than those with symptomatic ST depression when cardiovascular death, sudden death, or acute myocardial infarction are considered Clinical and exercise test variables have been underused in estimating prognosis. Specifically, they are rarely used systematically to stratify patients into low-risk groups who do not need catheterization and high-risk groups who should undergo angiography because of possible lesions amenable to bypass or angioplasty.(ABSTRACT TRUNCATED AT 400 WORDS)

Diagnostic and prognostic accuracy of the exercise electrocardiogram in patients with preexisting right bundle branch block

The value of exercise testing in patients with right bundle branch block (RBBB) is uncertain. A retrospective review of 3609 patients who underwent exercise testing identified 163 (4.5%) with preexisting RBBB. After excluding those with coronary artery bypass graft(s), 133 patients remained and 48 (36%) had a prior myocardial infarction. Angiograms were available for 30 (23%) patients. After a mean follow-up of 33 +/- 23 months, seven patients had a fatal or nonfatal myocardial infarction. Twenty five (19%) patients had > or = 1 mm of non-upsloping ST depression in leads V5 or V6. With angiographic disease or previous myocardial infarction used as endpoints of coronary artery disease, the exercise test had a sensitivity of 27% (15/56), a specificity of 87% (67/77), and a predictive accuracy of 62% (82/133), (chi 2 = 4.04, p = 0.04). There were 24 deaths, a 10% annual mortality rate. Univariate analysis of clinical, exercise, and angiographic data revealed that nonsurvivors had a lower peak systolic blood pressure, a lower exercise capacity in METS, and a higher prevalence of coronary artery disease (p = 0.0001, p = 0.02, p = 0.03, respectively). Left ventricular ejection fraction and the amount of additional ST depression during exercise did not differ significantly (p = NS). Receiver operating characteristic curve analysis revealed that systolic blood pressure (area = 0.741, z = 5.22, p < 0.001) and exercise capacity (area = 0.66, z = 3.12, p = 0.009) were predictive of mortality, whereas additional ST depression during exercise (area = 0.588, z = 0.70, p = 0.24) was not.(ABSTRACT TRUNCATED AT 250 WORDS)

A nomogram to predict exercise capacity from a specific activity questionnaire and clinical data

Recent investigations suggested that clinical exercise testing can be optimized by individualizing the protocol, depending on the purpose of the test and the subject tested. This requires some knowledge of a patient's exercise capacity before beginning the test. The accuracy of a simple physical activity questionnaire and readily available clinical data in predicting subsequent treadmill performance was examined. A brief, self-administered questionnaire (VSAQ) was developed for veterans who were referred to exercise testing for clinical reasons. The VSAQ was designed to determine which specific daily activities were associated with symptoms of cardiovascular disease (fatigue, chest pain and shortness of breath). Two hundred twelve consecutive patients (mean age 62 +/- 8 years) referred for maximal exercise testing were studied. Clinical and demographic variables were added to VSAQ responses in a stepwise regression model to determine their ability to predict treadmill performance. Only metabolic equivalents by VSAQ, and age were significant predictors of treadmill performance; these 2 variables yielded R = 0.82 (SEE 1.43; p < 0.001), and explained 67% of the variance in exercise capacity. The regression equation reflecting the relation between age, VSAQ and exercise capacity was: achieved metabolic equivalents = 4.7 + 0.97 (VSAQ) - 0.06 (age). Using this equation, a nomogram was developed. Incorporating the VSAQ with the nomogram requires only a few minutes, and yields a reasonably accurate estimate of a patient's exercise capacity. Although the present equation is population-specific, a similar approach in different populations may be useful for individualizing protocols for clinical exercise testing.

Influence of right coronary artery stenosis on exercise test responses and survival in patients with left main or left main equivalent disease

Forty-two patients with angiographically documented left main coronary artery (LM) disease (luminal occlusion > or = 50%) and 30 patients with left main equivalent (LMEQ) disease (> or = 70% luminal occlusion of both the proximal left anterior descending artery and proximal left circumflex artery) were studied to determine the role of right coronary artery (RCA) involvement on exercise test responses and survival. Significant (> or = 70%) RCA stenosis was present in 30 (72%) of the 42 LM patients and 16 (53%) of the 30 LMEQ patients. No significant differences were observed between LM and LMEQ patients in any clinical or exercise variables or survival. Thus both groups were combined for analysis of the influence of RCA involvement (i.e., LM/LMEQ with RCA versus LM/LMEQ without RCA disease). Greater ischemic responses were observed in the LM/LMEQ group with significant stenosis of the RCA. The presence of RCA stenosis was associated with significantly greater horizontal or downsloping ST-segment depression during exercise (2.4 +/- 1.2 mm vs 1.3 +/- 1.4 mm; p < 0.001), and prolonged recovery time until normalization of the ST segment (3.2 +/- 1.4 min vs 2.0 +/- 1.9 min; p < 0.01). The LM/LMEQ without RCA disease group behaved like the subgroup with two-vessel disease, and responses of the LM/LMEQ group with RCA disease were similar to the group with three-vessel disease. The annual survival in LM/LMEQ with RCA disease was worse than that in LM/LMEQ without RCA disease (average annual mortality rates = 7.5% vs 1.0%, respectively; p = 0.05). Infarct-free survival in LM/LMEQ with RCA disease was also lower than that in LM/LMEQ without RCA disease. Thus although patients with LM and LMEQ were similar in terms of survival and exercise responses, the presence of RCA stenosis was associated with significantly greater ST-segment depression, a prolonged recovery time until normalization of the ST segment, a fivefold increase in the death rate, and higher morbidity from myocardial infarction over a 5-year period of follow-up. Involvement of the RCA should be considered when making decisions concerning medical-surgical management of patients with severe coronary artery disease.

Predictors of disease severity and survival in patients with coronary artery disease

BACKGROUND

The objective of this study was to determine whether coronary angiographic findings and survival could be predicted using standard clinical and exercise-test data.

METHODS

Five hundred and ninety-five men who had undergone both exercise treadmill testing and cardiac catheterization were followed for up to 5 years. Left main (LM) disease (> or = 50% stenosis) was present in 42 patients, whereas 30 patients had LM equivalent disease (> or = 70% stenosis of both the proximal left anterior descending and circumflex coronary artery disease (n = 152), one-vessel disease (n = 186), two-vessel disease (n = 118), three-vessel disease (n = 67), LM or LM equivalent disease without significant (> or = 70%) right coronary artery involvement (n = 26), and LM or LM equivalent disease with right coronary artery involvement (n = 46).

RESULTS

ST-segment depression was more marked, whereas ejection fraction, maximal heart rate, maximal systolic blood pressure, and exercise capacity were lower in each group as disease severity worsened. Using Kaplan-Meier analysis, the subgroup with the poorest survival was found to be those with LM or LM equivalent disease with right coronary artery disease, and the next worse was the three-vessel disease group, in which survival was poorer than in all other subgroups (P < 0.01). Stepwise regression analysis revealed that the most powerful predictor for coronary artery disease severity was exercise-induced ST depression (P < 0.001), but it predicted survival poorly. History of congestive heart failure, low ejection fraction (50% or lower), and poor exercise capacity (5 metabolic equivalents or less) emerged as strong predictors of survival using stepwise Cox regression analysis (P < 0.001).

CONCLUSION

Exercise-induced ST depression predicted the severity of angiographic disease but not survival, whereas the strongest predictors of survival were history of congestive heart failure, low ejection fraction, and poor exercise capacity.

Cardiovascular benefits of improved exercise capacity

The evidence suggesting that regular exercise can help to prevent coronary artery disease is overwhelming. While some studies have suggested that exercise will not provide health benefits, our inactive population needs to pay heed to the substantial data presented by the many international health organisations suggesting the opposite. The American Heart Association Medical/Scientific Statement on Exercise emphasised the large role regular aerobic physical activity plays in the prevention of cardiovascular disease. Several human studies have also demonstrated the positive effects of long term exercise on the human heart. For example, it has been shown that a consistent exercise programme can lessen the impact of atherosclerotic plaques through increasing coronary artery diameter. Echocardiography studies on a training group of competitive swimmers have shown that exercise training can induce rapid changes in left ventricular dimensions and mass, which can ultimately lead to an increased stroke volume and increased maximal oxygen consumption. Studies on sedentary individuals have also demonstrated an increase in maximal oxygen uptake with a regular endurance exercise programme. In addition to these health benefits, habitual dynamic exercise can also decrease the likelihood of a cardiac event. Others have demonstrated a 50% lower incidence of coronary events in those individuals maintaining rigorous activity 2 days a week. With the preponderance of evidence revealing the health benefits of habitual exercise, it is striking to learn that more than 50% of the US population exercises for less than 20 minutes, 3 days a week. The widespread nature of this sedentary lifestyle makes inactivity an attributable fraction of the total risk factors associated with cardiac disease. The amount of exercise needed to reduce the risk of coronary artery disease is a minimum aerobic workout of 30 minutes, 4 to 5 times a week, such as a vigorous walk. Comprehensive programmes promoting exercise training should be implemented at a level appropriate to an individual's capacity and need.

Nomogram based on metabolic equivalents and age for assessing aerobic exercise capacity in men

OBJECTIVES

The goal of this study was to create a nomogram, based on maximal exercise capacity (in metabolic equivalents [METs]) and age, for assessing a patient's ability to perform dynamic exercise to quantify the level of physical disability or relative capacity for physical activity.

BACKGROUND

Providing an estimation of exercise capacity relative to age is clinically useful. Such an estimate can be derived from measured or estimated maximal oxygen uptake (in METs) from treadmill exercise testing and age. It is an effective means of communicating to patients their cardiopulmonary status, encouraging improvement in exercise capacity and quantifying disability.

METHODS

Exercise test results of 1,388 male patients (mean age 57 years, range 21 to 89) free of apparent heart disease who were referred for exercise testing for clinical reasons were retrospectively reviewed. This referral group as well as subgroups of active (n = 346) and sedentary (n = 253) patients were analyzed to determine norms for age and for age by decades for exercise test responses, including METs, maximal heart rate and maximal systolic blood pressure. Regression equations were calculated from this information, and a nomogram for calculating degree of exercise capacity from age and MET level achieved by a patient was created. A similar analysis was performed in a separate group of 244 apparently healthy, normal male volunteers (mean age 45 +/- 14 years, range 18 to 72) who underwent exercise testing with direct measurement of expired gases.

RESULTS

Equations for predicted METs for age were derived for the entire clinical referral group (METs = 18.0-0.15[Age]) and for the subgroups of active (METs = 18.7-0.15[Age]) and sedentary (METs = 16.6-0.16[Age]) patients. All results achieved statistical significance, with p values < 0.001. In the volunteer group of normal men who performed exercise testing with ventilatory gas exchange, the decline in maximal heart rate and METs with age was not as steep as in the referral group. Although the normal group confirmed nomograms published previously among similar subjects, the equations derived from the patients differed from those previously reported; in contrast to previous studies using healthy volunteers, the equations and nomograms for the referral group are more appropriate for patients typically referred for testing in a hospital or office-based internal medicine practice.

CONCLUSIONS

Norms for METs based on age are presented as well as population-specific nomograms that enable physicians to assess patients' exercise capacity relative to their age group.

Improved exercise test accuracy using discriminant function analysis and "recovery ST slope"

The objective of the study was to optimize the accuracy of the exercise test for predicting the presence of significant angiographic coronary artery disease. A retrospective analysis of stored digital exercise electrocardiographic data on 147 men who had undergone exercise testing and cardiac catheterization was performed. With significant coronary artery disease defined as > or = 70% stenosis, 95 patients had one or more vessel(s) diseased. None were receiving digoxin, had a myocardial infarction or previous coronary artery bypass graft, or exhibited left bundle branch block, left ventricular hypertrophy, Q waves, or ST depression on their resting electrocardiogram. Analysis was performed using the authors' averaging and measurement software at rest and at each 30 seconds throughout the exercise and recovery in leads II, V2, and V5. Discriminant function analysis was used to analyze pretest variables, as well as hemodynamic and electrocardiographic changes and symptoms during exercise. A discriminant function score was developed and compared to other treadmill scores. The setting was a 1,000 bed Veterans Affairs Medical Center (Long Beach, CA). Discriminant function analysis chose age, smoking status, presenting chest pain characteristics, and lead V5 ST slope in recovery to have independent power for separating those with and without coronary artery disease. A discriminant function score using these four variables was used to form a receiver operating characteristics curve (and derive receiver operating characteristics curve areas) for comparison to other exercise test methods and scores: (discriminant function score = .81; slope 3.5 minutes into recovery in lead V5 = .73; traditional ST amplitude method = .72; ST60/HR index (amplitude of ST depression 60 ms after the J point/delta heart rate) = .66; traditional ST amplitude/HR index (traditional method/delta heart rate) = .75; Hollenberg score = .68; Hollenberg areas only = .66; and ST integral = .66. Receiver operating characteristics curve analysis revealed a trend for the discriminant function score to be superior to all other measurements and scores. Recovery ST slope in lead V5 performed as well as or better than all other electrocardiographic criteria or treadmill scores except for the authors' discriminant function score.

Prediction of cardiovascular death by means of clinical and exercise test variables in patients selected for cardiac catheterization

The objective of this report is the development of a population-specific prediction rule based on clinical and exercise test data that would estimate the risk of cardiovascular death in patients selected for cardiac catheterization. Prospective data and follow-up information were obtained from patients who underwent cardiac catheterization soon after clinical assessment and exercise testing. Males (n = 588) referred for evaluation of coronary heart disease from 1984 to 1990 were selected after exclusion of patients with significant valvular heart disease and patients with prior cardiac surgery. Half had a prior myocardial infarction and half complained of typical angina pectoris. All patients performed a treadmill test and were selected for clinical reasons to undergo coronary angiography within 3 months. Over a mean follow-up period of 2.5 years (+/- 1.4 years), there were 39 cardiovascular deaths and 45 nonfatal myocardial infarctions. The Cox proportional hazards model demonstrated the following characteristics to be statistically significant independent predictors of time until cardiovascular death: history of congestive heart failure (hazards ratio of 4), ST depression on the resting ECG (hazards ratio of 3), and a drop in systolic blood pressure below the resting value during exercise (hazards ratio of 5). Exercise-induced ST depression was not associated with either death or nonfatal myocardial infarction. A simple score based on one item of clinical information (history of congestive heart failure), a resting ECG finding (ST depression), and an exercise test response (exertional hypotension) stratified our patients for 4 years after testing from 75% with a low risk (annual cardiac mortality rate of 1%), 17% with a moderate risk (annual mortality rate of 7%), and 1% with a high risk (annual cardiac mortality rate of 12%, with a hazards ratio of 20 and 95% confidence interval from 6 to 70X). It was concluded that the variables available from the usual noninvasive workup of patients with known or suspected coronary artery disease enable prediction of risk of cardiovascular death. Three quarters of those usually undergoing cardiac catheterization can be identified by simple noninvasive variables as being at such low risk that invasive intervention is unlikely to improve prognosis.