Using an outcomes-based approach to identify candidates for risk stratification after exercise treadmill testing

Enhancing the diagnostic specificity of exercise ECG testing in obstructive coronary artery disease: the role of the Selvester QRS score

BACKGROUND

Exercise ECG testing is a widely used, noninvasive tool for detecting obstructive coronary artery disease (OCAD). However, its diagnostic performance is often limited by low specificity, leading to false-positive results and unnecessary invasive procedures.

OBJECTIVE

This study aims to assess the potential of combining the Selvester QRS score with exercise ECG to enhance diagnostic specificity for OCAD in patients with suspected stable angina.

METHODS

This retrospective study included 203 patients who presented with chest pain, underwent exercise ECG and were assessed for OCAD by coronary angiography or computed tomography angiography. Receiver operating characteristic analysis identified the optimal Selvester QRS score cutoff and assessed the diagnostic performance of exercise ECG and the combined model. Multivariable logistic regression was performed in the exercise ECG positive and negative groups.

RESULTS

Of the 203 patients, 116 were diagnosed with OCAD. The optimal Selvester QRS score cutoff was ≥3, with a sensitivity of 83.6% and a specificity of 93.1%. The combination of a positive exercise ECG and a Selvester QRS score ≥3 achieved the highest specificity (98.9%). Regression analyses showed that Selvester QRS score ≥3 was an independent predictor of OCAD, even in patients with negative exercise ECG results (adjusted odds ratio: 7.018; P < 0.001).

CONCLUSION

The Selvester QRS score can improve the specificity of the exercise ECG in detecting OCAD in patients with suspected stable angina. This approach has the potential to reduce false positives and unnecessary invasive procedures by improving risk stratification.

Vall d'Hebron Risk Score II for myocardial infarction and cardiac death

OBJECTIVES

The aim of this study was to create a new Vall d'Hebron Risk Score-II (VH-RS-II) for non-fatal myocardial infarction (MI) and/or cardiac death (CD), excluding patients with coronary revascularisation (CR) during the follow-up.

METHODS

We analysed 5215 consecutive patients underwent gated single photon emission CT (SPECT); 2960 patients (age 64.2±11, male 58.1%) had no previous MI and/or CR, and 2255 patients (age 63.3±11, male 81.9%) had previous MI and/or CR. During a follow-up of 4.3±2.6 years, the cardiac event (MI and CD) was evaluated. This study was reviewed and approved by the ethics committee of our institution (number form trial register, PR(AG)168.2012). To obtain the predictor model, multivariate Cox regression analysis and multivariate logistic regression analysis were used. RS-VH-II was validated with 679 patients.

RESULTS

In patients without previous MI and/or CR, age (HR: 1.01; p<0.001), diabetes (HR: 2.1, p=0.001), metabolic equivalent (METs) (HR: 0.89, p=0.038), ST segment depression (HR: 1.4, p=0.011), ejection fraction (EF) (HR: 0.97, p<0.001) and summed stress score (HR: 1.2, p<0.001) were the independent predictors of CE (C-statistic: 0.8). In patients with previous MI and/or CR, age (HR: 1.06, p<0.001), male (HR: 1.9, p=0.047), smoker (HR: 1.5, p=0.047), METs (HR: 0.8, p<0.001), ST segment depression (HR: 1.4, p=0.002), EF (HR: 0.96; p<0.001) and summed difference score (HR: 1.03, p=0.06) were the independent predictors of CE (C-statistic:0.8).

CONCLUSION

The VH-RS-II obtained from different clinical exercise and gated SPECT variables allow the risk stratification for MI and CD in patients with or without previous MI and/or CR in due form.

A novel clinical risk prediction model for myocardial infarction, coronary revascularization, and cardiac death according to clinical, exercise, and gated SPECT variables (VH-RS)

AIMS

To create a risk score for cardiac events (CE) according to clinical, exercise, and gated SPECT variables.

METHODS AND RESULTS

We analysed 5707 consecutive patients; 3181 patients (age 64.2 ± 11 years, male 59.6%) with suspected coronary artery disease (CAD) [without previous myocardial infarction (MI) or coronary revascularization (CR)] and 2526 patients (age 63.3 ± 11 years, male 81.7%) with established CAD (with previous MI or CR). To create the Vall d'Hebron Risk Score (VH-RS), first we analyse the predictors of CE (non-fatal MI, CR, and/or cardiac death), then the probability of CE for every patient according to the predictive variables. According to risk we stratified patients into four risk levels: very low risk (VLR), low risk (LR), moderate risk (MR), and high risk (HRi) using Multiple Cox Regression analysis models. Finally, we validate the VH-RS in another prospective cohort of 734 patients. In patients with suspected CAD; age (P < 0.001); gender (P = 0.001); hyperlipidaemia (P < 0.001); nitrates (P = 0.04); ejection fraction (EF) (P = 0.001); summed stress score (P < 0.001); METs (P < 0.001); exercise angina (P = 0.006); and mm of ST segment depression (P = 0.004) were the independent predictors of CE (C-statistic: 0.8; P < 0.001). In patients with established CAD, EF (P < 0.001); summed difference score (P = 0.001); age (P < 0.001); smoker (P = 0.002); nitrates (P = 0.003); exercise angina (P = 0.001); METs (P < 0.001); and mm of ST segment depression (P = 0.011) were the independent predictors of CE (C-statistic: 0.7; P < 0.001). The risk score obtained from these variables allows the stratification of patients into four risk levels: VLR, LR, MR, and HRi.

CONCLUSIONS

The cardiac risk stratification by mean of clinical, exercise, and gated SPECT variables is an objective aid to assessing an individual's cardiac risk.

Cardiovascular outcomes are predicted by exercise-stress myocardial perfusion imaging: Impact on death, myocardial infarction, and coronary revascularization procedures

BACKGROUND

The aim of this study was to determine the impact of myocardial perfusion imaging (MPI) on the outcomes of death, myocardial infarction (MI), and late coronary revascularization procedures.

METHODS

In patients undergoing exercise-stress MPI (January 1, 2003-March 31, 2007), we determined the impact of summed stress score (SSS) and percent left ventricular (LV) ischemia on (a) death or MI and (b) composite of death, MI, or late coronary revascularization occurring more than 90 days post-MPI.

RESULTS

During 35,007 person-years of follow-up among 9,605 patients (mean ± SD age 54.4 ± 13.2 years, 60.3% men), there were 290 deaths, 175 MIs, and 525 coronary revascularization procedures. Of those who attained ≥10 metabolic equivalents (METS) workload, major stress perfusion defects (SSS ≥7) were present in 4.2% overall and in 3.7% without ST-segment shifts, whereas large ischemic defects (≥10% LV ischemia) were present in 1% overall and 0.7% without ST-segment shifts. For those with 1% to 4%, 5% to 9%, and ≥10% LV ischemia, adjusted hazard ratios were 1.40 (95% CI 1.13-1.73, P = .002), 2.07 (95% CI 1.56-2.74, P < .001), and 3.03 (95% CI 2.21-4.16, P < .001) for the outcome of late revascularization, MI, or death versus no ischemia. Summed stress scores ≥7 were associated with increased risk of death or MI, with an adjusted hazard ratio of 1.57 (95% CI 1.16-2.13, P = .004) compared with those with no stress perfusion defects.

CONCLUSION

Although workload ≥10 METS conferred lower frequency of major ischemia (≥10%), %LV ischemia predicted the occurrence of cardiovascular events and death (eg, MI, late coronary revascularization, or death). Presence of a large stress perfusion defect (SSS ≥7) predicted increased risk of MI or death.

Progression of coronary artery calcium predicts all-cause mortality

OBJECTIVES

This study examined a large cohort to assess whether progression of coronary artery calcium (CAC) was associated with all-cause mortality, and which among 3 different methods to assess CAC progression provided the best estimate of risk.

BACKGROUND

Serial assessment of CAC scores has been proposed as a method to follow progression of coronary artery disease, and it has been suggested that excessive CAC progression may be a useful noninvasive predictor of the patient's risk of future events. However, the optimal method to measure calcium progression has not been well established.

METHODS

The study sample consisted of 4,609 consecutive asymptomatic individuals referred by primary physicians for CAC measurement with electron beam tomography, who underwent repeat screening. Three general statistical approaches were taken: 1) the absolute difference between follow-up and baseline CAC score; 2) percent annualized differences between follow-up and baseline CAC score; and 3) difference between square root of baseline and square root of follow-up CAC score >2.5 (the "SQRT method").

RESULTS

The average interscan time was 3.1 years, and there were 288 deaths. Progression of CAC was significantly associated with mortality regardless of the method used to assess progression (p < 0.0001). After adjusting for baseline score, age, sex, and time between scans, the best CAC progression model to predict mortality was the SQRT method (hazard ratio [HR]: 3.34; 95% confidence interval [CI]: 2.65 to 4.21; p < 0.0001), followed by a >15% yearly increase (HR: 2.98; 95% CI: 2.20 to 4.95; p < 0.0001). Progression was very limited and did not predict mortality in patients with baseline CAC = 0.

CONCLUSIONS

The CAC progression added incremental value in predicting all-cause mortality over baseline score, time between scans, demographics, and cardiovascular risk factors. Serial assessment may have clinical value in assessing plaque progression and future cardiovascular risk.

Incremental prognostic value of the exercise electrocardiogram in the initial assessment of patients with suspected angina: cohort study

OBJECTIVE

To determine whether resting and exercise electrocardiograms (ECGs) provide prognostic value that is incremental to that obtained from the clinical history in ambulatory patients with suspected angina attending chest pain clinics.

DESIGN

Multicentre cohort study.

SETTING

Rapid access chest pain clinics of six hospitals in England.

PARTICIPANTS

8176 consecutive patients with suspected angina and no previous diagnosis of coronary artery disease, all of whom had a resting ECG recorded. 4848 patients with a summary exercise ECG result recorded (positive, negative, equivocal for ischaemia) comprised the summary ECG subset of whom 1422 with more detailed exercise ECG data recorded comprised the detailed ECG subset.

MAIN OUTCOME MEASURE

Composite of death due to coronary heart disease or non-fatal acute coronary syndrome during median follow-up of 2.46 years.

RESULTS

Receiver operating characteristics curves for the basic clinical assessment model alone and with the results of resting ECGs were superimposed with little difference in the C statistic. With the exercise ECGs the C statistic in the summary ECG subset increased from 0.70 (95% confidence interval 0.68 to 0.73) to 0.74 (0.71 to 0.76) and in the detailed ECG subset from 0.74 (0.70 to 0.79) to 0.78 (0.74 to 0.82). However, risk stratified cumulative probabilities of the primary end point at one year and six years for all three prognostic indices (clinical assessment only; clinical assessment plus resting ECG; clinical assessment plus resting ECG plus exercise ECG) showed only small differences at all time points and at all levels of risk.

CONCLUSION

In ambulatory patients with suspected angina, basic clinical assessment encompasses nearly all the prognostic value of resting ECGs and most of the prognostic value of exercise ECGs. The limited incremental value of these widely applied tests emphasises the need for more effective methods of risk stratification in this group of patients.

Long-term prognosis associated with coronary calcification: observations from a registry of 25,253 patients

OBJECTIVES

The purpose of this study was to develop risk-adjusted multivariable models that include risk factors and coronary artery calcium (CAC) scores measured with electron-beam tomography in asymptomatic patients for the prediction of all-cause mortality.

BACKGROUND

Several smaller studies have documented the efficacy of CAC testing for assessment of cardiovascular risk. Larger studies with longer follow-up will lend strength to the hypothesis that CAC testing will improve outcomes, cost-effectiveness, and safety of primary prevention efforts.

METHODS

We used an observational outcome study of a cohort of 25,253 consecutive, asymptomatic individuals referred by their primary physician for CAC scanning to assess cardiovascular risk. Multivariable Cox proportional hazards models were developed to predict all-cause mortality. Risk-adjusted models incorporated traditional risk factors for coronary disease and CAC scores.

RESULTS

The frequency of CAC scores was 44%, 14%, 20%, 13%, 6%, and 4% for scores of 0, 1 to 10, 11 to 100, 101 to 400, 401 to 1,000, and >1,000, respectively. During a mean follow-up of 6.8 +/- 3 years, the death rate was 2% (510 deaths). The CAC was an independent predictor of mortality in a multivariable model controlling for age, gender, ethnicity, and cardiac risk factors (model chi-square = 2,017, p < 0.0001). The addition of CAC to traditional risk factors increased the concordance index significantly (0.61 for risk factors vs. 0.81 for the CAC score, p < 0.0001). Risk-adjusted relative risk ratios for CAC were 2.2-, 4.5-, 6.4-, 9.2-, 10.4-, and 12.5-fold for scores of 11 to 100, 101 to 299, 300 to 399, 400 to 699, 700 to 999, and >1,000, respectively (p < 0.0001), when compared with a score of 0. Ten-year survival (after adjustment for risk factors, including age) was 99.4% for a CAC score of 0 and worsened to 87.8% for a score of >1,000 (p < 0.0001).

CONCLUSIONS

This large observational data series shows that CAC provides independent incremental information in addition to traditional risk factors in the prediction of all-cause mortality.

Prognostic value of cardiac risk factors and coronary artery calcium screening for all-cause mortality

PURPOSE

To develop risk-adjusted multivariable models that included risk factors and coronary calcium scores determined with electron-beam computed tomography (CT) in asymptomatic patients for the prediction of all-cause mortality.

MATERIALS AND METHODS

We followed up a cohort of 10,377 asymptomatic individuals undergoing cardiac risk factor evaluation and coronary calcium screening with electron-beam CT. Multivariable Cox proportional hazards models were developed to predict all-cause mortality. Risk-adjusted models incorporated traditional risk factors for coronary disease and coronary calcium scores.

RESULTS

Cardiac risk factors such as family history of coronary disease (69%), hypercholesterolemia (62%), hypertension (44%), smoking (40%), and diabetes (9%) were prevalent. The frequency of coronary calcium scores was 57%, 20%, 14%, 6%, and 3% for scores of 10 or less, 11-100, 101-400, 401-1,000, and greater than 1,000, respectively. During a mean follow-up of 5.0 years +/- 0.0086 (standard error of the mean), the death rate was 2.4%. In a risk-adjusted model (model chi2 = 388.2, P <.001), coronary calcium was an independent predictor of mortality (P <.001). Risk-adjusted relative risk values for coronary calcium were 1.64, 1.74, 2.54, and 4.03 for scores of 11-100, 101-400, 401-1,000, and greater than 1,000, respectively (P <.001 for all values), as compared with that for a score of 10 or less. Five-year risk-adjusted survival was 99.0% for a calcium score of 10 or less and 95.0% for a score of greater than 1,000 (P <.001). With a receiver operating characteristic curve, the concordance index increased from 0.72 for cardiac risk factors alone to 0.78 (P <.001) when the calcium score was added to a multivariable model for prediction of death.

CONCLUSION

This large observational data series shows that coronary calcium provides independent incremental information in addition to traditional risk factors in the prediction of all-cause mortality.

Prognostic value of stress echocardiography in women with high (> or = 80%) probability of coronary artery disease

OBJECTIVE

To assess the prognostic significance of stress echocardiography in women with a high probability of coronary artery disease (CAD).

SETTING

Secondary and tertiary cardiology unit at a university teaching hospital.

PARTICIPANTS

A total of 135 women (mean (SD) age 63 (9) years) with pre-test probability of CAD > or = 80% were selected from a database of patients investigated by treadmill or dobutamine stress echocardiography between 1995 and 1998.

MAIN OUTCOME MEASURES

Patients were followed up for occurrence of subsequent cardiac events (cardiac death, myocardial infarction, admission with unstable angina, and revascularisation) using a structured telephone interview and case note review.

RESULTS

Each patient had between two and seven (mean 3.5) CAD risk factors and pre-test probability of CAD > or = 80%. Ninety three patients (68.9%) had negative stress echocardiography. Mean (SD) follow up was 20.1 (8.5) months. There were six events in the positive stress echocardiography group (two cardiac deaths, one unstable angina, three revascularisations), and one event in the negative stress echocardiography group. Cox regression analysis showed positive stress echocardiography (p = 0.02) and age (p = 0.03) to be the only univariate predictors and positive stress echocardiography to be the only independent predictor of future cardiac events (relative risk 8.9, confidence interval 1.0 to 76.5, p = 0.04). Cumulative event free survival to 38 months was 98% in the negative stress echocardiography and 50.7% in the positive stress echocardiography groups.

CONCLUSION

In women with high pre-test likelihood of CAD: (1) negative stress echocardiography identifies a subgroup with low risk of cardiac events who do not require further invasive investigation and (2) positive stress echocardiography identifies a subgroup with increased risk of subsequent cardiac events.

Exercise electrocardiogram testing and prognosis. Novel markers and predictive instruments

Ample evidence now exists supporting the use of the exercise test primarily for prognostic, as opposed to diagnostic, purposes. Although limitations must be recognized, the Duke exercise treadmill score, the chronotropic response to exercise, and heart rate recovery appear to function as powerful and independent predictors of risk. With the possible exception of exercise-induced ischemia, as manifested by the ST-segment and angina components of the Duke exercise treadmill score, exercise predictors of risk are not clearly modifiable. Nonetheless, they are clinically quite useful since they may well identify patients who are or are not likely to gain benefit from further testing and aggressive therapies. How so? The "plain old" exercise treadmill test makes it possible to easily, safely, and inexpensively identify a large group of patients who are at low risk for death or major cardiac events. For this reason alone, the predictive instruments described in this article should be routinely incorporated into clinical practice. It makes no sense to perform expensive and potentially risky diagnostic tests, prescribe polypharmacy, or institute invasive therapeutic procedures in patients who are already at low risk. As an example, Weiner and colleagues found that coronary bypass grafting only benefited CASS registry patients who had a high-risk exercise test result. Future research will be needed to further refine risk stratification with the exercise test, and determine how best to use adjunctive imaging studies and to reduce risk among patients with prognostically important findings.

Prediction of mortality by exercise echocardiography: a strategy for combination with the duke treadmill score

BACKGROUND

In studies generally involving short follow-up, exercise echocardiography has been shown to predict composite end points. We sought to study the prediction of mortality with this test and to devise a strategy for combination with standard exercise testing.

METHODS AND RESULTS

Clinical, exercise testing, and echocardiographic data were collected in 5375 patients (aged 54+/-14 years, 3880 men) undergoing exercise echocardiography. The Duke treadmill score was derived from the results of treadmill exercise testing. Resting left ventricular (LV) function and the presence and severity of ischemia were interpreted by expert observers. Follow-up at 10.6 years (mean 5.5+/-1.9 years) was complete in 5211 patients (97%). The Duke score classified 59% of patients as low risk, 39% as intermediate risk, and 2% as high risk. Resting LV dysfunction was present in 1445 patients (27%), and the exercise echocardiogram was abnormal in 2525 patients (47%). Death occurred in 649 patients (12%). Over the first 6 years of follow-up, those with normal exercise echocardiograms had a mortality of 1% per year. Ischemia was an independent predictor of mortality. In sequential Cox models, the predictive power of clinical data was strengthened by adding the Duke score, resting LV function, and the results of exercise echocardiography. Exercise echocardiography was able to substratify patients with intermediate-risk Duke scores into groups with a yearly mortality of 2% to 7%.

CONCLUSIONS

A normal exercise echocardiogram confers a low risk of death, and positive results are an independent predictor of death; ischemia is incremental to other data. This test may be particularly useful in patients with intermediate-risk Duke treadmill scores.

Stress testing for risk stratification of patients with low to moderate probability of acute cardiac ischemia

In summary, this article focused on the use of stress testing to risk-stratify patients at the conclusion of their emergency evaluation for ACI. As discussed, those patients in the probably not ACI category require additional risk stratification prior to discharge. It should be kept in mind that patients in this category are heterogeneous, containing subgroups at both higher and lower risk of ACI and cardiac events. The patients with lower pretest probability for ACI may only need exercise testing in the ED. Patients with higher pretest probability should undergo myocardial perfusion or echocardiographic stress testing to maximize diagnostic and prognostic information. Prognostic information is the key to provocative testing in the ED. Prognostic information is the component that will help emergency physicians identify the patients who may be discharged home safely without having to worry about a 6% annual cardiac death rate and a 10% overall death rate over the next 30 months. Stress testing provides this key prognostic data, and it can be obtained in short-stay chest pain observation units in a safe, timely, and cost-effective fashion.

Diagnostic testing

The results of cardiac tests must always be interpreted through the lens of pretest probabilities created by the history and the physical examination. Tests should be chosen with a clear diagnostic and prognostic purpose in mind. A clear understanding of the relationship between the history and physical examination and more technologic diagnostic testing improves the primary care physician's ability to evaluate potential cardiac disease in an efficient and cost-effective manner.