Heart rate adjustment of ST segment depression and performance of the exercise electrocardiogram: a critical evaluation

Clinical significance of ST-segment depression during atrial fibrillation rhythm for subsequent heart failure events

Aims

The clinical significance of ST-segment depression during atrial fibrillation (AF) rhythm has not been fully evaluated. The aim of the present study was to explore the association of ST-segment depression during AF rhythm with subsequent heart failure (HF) events.

Methods and results

The study enrolled 2718 AF patients whose baseline electrocardiography (ECG) was available from a Japanese community-based prospective survey. We assessed the association of ST-segment depression in baseline ECG during AF rhythm with clinical outcomes. The primary ednpoint was a composite HF endpoint: cardiac death or hospitalization due to HF. The prevalence of ST-segment depression was 25.4% (upsloping 6.6%, horizontal 18.8%, downsloping 10.1%). Patients with ST-segment depression were older and had more comorbidities than those without. During the median follow-up of 6.0 years, the incidence rate of the composite HF endpoint was significantly higher in patients with ST-segment depression than those without (5.3% vs. 3.6% per patient-year, log-rank P < 0.01). The higher risk was present in horizontal or downsloping ST-segment depression, but not in upsloping one. By multivariable analysis, ST-segment depression was an independent predictor for the composite HF endpoint (hazard ratio 1.23, 95% confidence interval 1.03-1.49, P = 0.03). In addition, ST-segment depression at anterior leads, unlike inferior or lateral leads, was not associated with higher risk for the composite HF endpoint.

Conclusion

ST-segment depression during AF rhythm was associated with subsequent HF risk; however, the association was affected by type and distribution of ST-segment depression.

ST/HR variables in firefighter exercise ECG - relation to ischemic heart disease

Exercise electrocardiography (ExECG) is regularly performed by Swedish firefighters by law. Heart rate-corrected analysis of ST segment variables (ST/HR) has shown improved prediction of ischemic heart disease (IHD) compared to ST depression alone. This has not previously been extensively studied in asymptomatic persons with a low probability of IHD. We therefore evaluated the predictive performance of ST/HR analysis in firefighter ExECG. ExECG was studied in 521 male firefighters. During 8.4 ± 2.1 years, 2.3% (n = 12) were verified with IHD by catheterization or myocardial scintigraphy (age 51.5 ± 5.5 years) and were compared with firefighters without imaging proof of IHD (44.2 ± 10.1 years). The predictive value of ST depression, ST/HR index, ST/HR slope, and area and rotation of the ST/HR loop was calculated as age-adjusted odds ratios (OR), in 10 ECG leads. Predictive accuracy was analyzed with receiver operating characteristics (ROC) analysis. ST/HR index ≤-1.6 μV/bpm and ST/HR slope ≤-2.4 μV/bpm were associated with increased IHD risk in three individual leads (all OR > 1.0, P < 0.05). ST/HR loop area lower than the fifth percentile of non-IHD subjects indicated IHD risk in V4, V5, aVF, II, and -aVR (P < 0.05). ST depression ≤-0.1 mV was associated with IHD only in V4 (OR, 9.6, CI, 2.3-40.0). ROC analysis of each of these variables yielded areas under the curve of 0.72 or lower for all variables and leads. Clockwise-rotated ST/HR loops was associated with increased risk in most leads compared to counterclockwise rotation. The limited clinical value of ExECG in low-risk populations was emphasized, but if performed, ST/HR analysis should probably be given more importance.

False-positive stress testing: Does endothelial vascular dysfunction contribute to ST-segment depression in women? A pilot study

BACKGROUND

The utility of exercise-induced ST-segment depression for diagnosing ischemic heart disease (IHD) in women is unclear.

HYPOTHESIS

Based on evidence that IHD pathophysiology in women involves coronary vascular dysfunction, we hypothesized that coronary vascular dysfunction contributes to exercise electrocardiography (Ex-ECG) ST-depression in the absence of obstructive coronary artery disease, so-called false positive results. We tested our hypothesis in a pilot study evaluating the relationship between peripheral vascular endothelial function and Ex-ECG.

METHODS

Twenty-nine asymptomatic women without cardiac risk factors underwent maximal Bruce protocol exercise treadmill testing and peripheral endothelial function assessment using peripheral arterial tonometry (Itamar EndoPAT 2000) to measure reactive hyperemia index (RHI). The relationship between RHI and Ex-ECG ST-segment depression was evaluated using logistic regression and differences in subgroups using 2-tailed t tests.

RESULTS

Mean age was 54 ± 7 years, body mass index 25 ± 4 kg/m² , and RHI 2.51 ± 0.66. Three women (10%) had RHI <1.68, consistent with abnormal peripheral endothelial function, whereas 18 women (62%) met criteria for positive Ex-ECG based on ST-segment depression in contiguous leads. Women with and without ST-segment depression had similar baseline and exercise vital signs, metabolic equivalents achieved, and RHI (all P > 0.05). RHI did not predict ST-segment depression.

CONCLUSIONS

Our pilot study demonstrates high prevalence of exercise-induced ST-segment depression in asymptomatic, middle-aged, overweight women. Peripheral vascular endothelial dysfunction did not predict Ex-ECG ST-segment depression. Further work is needed to investigate the utility of vascular endothelial testing and Ex-ECG for IHD diagnostic and management purposes in women.

Gene therapy to stimulate angiogenesis to treat diffuse coronary artery disease

Cardiac gene therapy offers a strategy to treat diffuse coronary artery disease (CAD), a disorder with no therapeutic options. The use of genes to revascularize the ischemic myocardium has been the focus of two decades of preclinical research with a variety of angiogenic mediators, including vascular endothelial growth factor, fibroblast growth factor, hepatocyte growth factor, and others encoded by DNA plasmids or adenovirus vectors. The multifaceted challenge for developing efficient induction of collateral vessels in the ischemic heart requires a choice for route of delivery, dosing level, a relevant animal model, duration of treatment, and assessment of phenotype for efficacy. Overall, studies of gene therapy for ischemia in experimental models are very encouraging, with clear evidence of safety and efficacy, strongly supporting the concept that gene therapy to induce angiogenesis is a viable therapeutic approach for CAD. Clinical studies of cardiac gene therapy with angiogenic factors have added substantially to the evidence for efficacy, but definitive studies have not yet led to commercial approval. This review provides the general concepts for angiogenesis-based therapeutic approaches for diffuse CAD and summarizes the results from key studies in the field with recommendations for refinement to a successful product design and evaluation.

Improved detection of ischemic heart disease by combining high-frequency electrocardiogram analysis with exercise stress echocardiography

Background and Objectives

Because the exercise treadmill test (ETT) based on ST-segment analysis is limited due to low sensitivity and specificity, there has been an interest in the additional analysis of high-frequency components of QRS (HFQRS) for the detection of coronary artery disease (CAD). We sought to evaluate the feasibility and clinical usefulness of HFQRS analysis during exercise stress echocardiography (ESE).

Subjects and Methods

We evaluated 175 patients (age 57±9,118 men) who performed ESE and either coronary computed tomographic angiography or coronary angiography. ETT was performed using the HyperQ stress system for both conventional ST-segment analysis and HFQRS intensity analysis.

Results

Thirty-two patients (31%) had significant CAD. The sensitivity and specificity of HFQRS analysis were 68.8% and 74.8%, respectively. The combined model, including HFQRS analysis and ESE, provided the best diagnostic accuracy, with the area under the receiver-operating characteristics curve (AUC) of 0.948 {95% confidence interval (CI)=0.913-0.984} compared with ST-segment analysis (AUC 0.679, 95% CI=0.592-0.766).

Conclusion

HFQRS analysis during ESE is feasible and may provide additional diagnostic information for the detection of significant CAD.

Impact of advanced exercise ECG analysis on cost of coronary artery disease management

BACKGROUND

Conventional analysis of exercise electrocardiogram (EX-ECG) has limited accuracy. This study aims to evaluate the potential impact of improving EX-ECG accuracy on costs of diagnosis and number of misdiagnoses of coronary artery disease (CAD).

METHODS

A decision-tree model was simulated including sequential application of diagnostic procedures for suspected CAD. The model was structured in two main branches (presence or absence of CAD). A probabilistic sensitivity analysis was then performed for several combinations of improvement in test sensitivity and specificity.

RESULTS

A clear trend in cost reduction was observed at improving EX-ECG specificity (about 8-8.5 million dollars, corresponding to a 5.6-7.6% reduction according to the prevalence level). Wrong diagnoses counted for 9-13% of test. Improvements in test parameters lead to reductions in wrong diagnoses, especially when increasing specificity (8.8-12.5%).

CONCLUSIONS

A proper improvement in EX-ECG sensitivity and specificity would have a relevant impact on the costs of CAD management, while reducing the number of misdiagnoses.

Evaluation of ST‐segment changes during and after maximal exercise tests in one‐, two‐ and three‐vessel coronary artery disease

OBJECTIVE

To relate ECG and heart rate (HR) variables during and after exercise testing with the presence of one-, two- or three-vessel disease defined by angiography.

DESIGN

Seventy-three male patients with stable angina pectoris and angiographically verified coronary artery disease underwent a maximal exercise test. From 12-lead ECG recordings and computer averaging ST-amplitude and HR data were measured in consecutive 10-s intervals.

RESULTS

In univariate analysis, patients with three-vessel disease had lower maximal exercise capacity, a shorter time to >1 mm ST-depression, more often a clockwise ST/HR recovery loop, more frequently a post-exercise downward ST-segment slope, and a greater ST-deficit at 3.5 min after exercise than patients with one-vessel disease. In multivariate analysis, time to >1 mm ST-depression discriminated between patients with three- and one-vessel disease. In patients with an intermediate time to >1 mm ST-depression a clockwise ST/HR recovery loop and/or a downsloping ST-segment in the post-exercise period were significantly more prevalent in severe vessel disease.

CONCLUSION

Patients with three-vessel disease had a significantly shorter time to >1 mm ST-depression during exercise and more often an abnormal post-exercise ST/HR reaction than those with one-vessel disease.

Age-adjusted modification of the Duke Treadmill Score nomogram

BACKGROUND

The Duke Treadmill Score (DTS) is an established clinical tool for risk stratification of patients referred for exercise testing, but it does not consider age. We aimed to determine if age could improve the prognostic power of the DTS and if so, to modify the DTS nomogram to include age.

METHODS

Of 1,959 patients referred for exercise testing from 1997 to 2006, 1,759 male veterans (age range 23-86 years) remained after exclusion of female and patients with heart failure. Cardiovascular mortality was the main outcome considered.

RESULTS

Cox survival analysis was performed entering age and the DTS; both were significant (P <or= .002) with similar Wald Z values (5.4 and -3.1) and regression coefficients but opposite signs. The score: age-DTS yielded an area under the receiver operating characteristic curve of 0.80 compared with 0.76 for the DTS (P < .001). Using this equation, a nomogram was constructed by adding age to the original DTS nomogram. The point at which the age-DTS line intersects the drawing line from the DTS to the corresponding value for age indicates average annual cardiovascular (CV) mortality adjusted for age. For a DTS associated with a 2.5% annual CV mortality, an age of 30 compared with 70 decreased CV risk by a factor of 10 to less than 0.2% (P < .05, log-rank test).

CONCLUSIONS

We propose an age-adjusted DTS nomogram that improves the prognostic estimates of average annual CV mortality over the DTS alone. This nomogram requires external validation and extension to women.

Context-aware sensing of physiological signals

Recent advancement in microsensor technology permits miniaturization of conventional physiological sensors. Combined with low-power, energy-aware embedded systems and low power wireless interfaces, these sensors now enable patient monitoring in home and workplace environments in addition to the clinic. Low energy operation is critical for meeting typical long operating lifetime requirements. Some of these physiological sensors, such as electrocardiographs (ECG), introduce large energy demand because of the need for high sampling rate and resolution, and also introduce limitations due to reduced user wearability. In this paper, we show how context-aware sensing can provide the required monitoring capability while eliminating the need for energy-intensive continuous ECG signal acquisition. We have implemented a wearable system based on standard widely-used handheld computing hardware components. This system relies on a new software architecture and an embedded inference engine developed for these standard platforms. The performance of the system is evaluated using experimental data sets acquired for subjects wearing this system during an exercise sequence. This same approach can be used in context-aware monitoring of diverse physiological signals in a patient's daily life.

Receiver operating characteristic (ROC) curves and the definition of threshold levels to diagnose coronary artery disease on electrocardiographic stress testing. Part II: the use of ROC curves in the choice of electrocardiographic stress test markers of ischaemia

A common problem in diagnostic medicine, when performing a diagnostic test, is to obtain an accurate discrimination between 'normal' cases and cases with disease, owing to the overlapping distributions of these populations. In clinical practice, it is exceedingly rare that a chosen cut point will achieve perfect discrimination between normal cases and those with disease, and one has to select the best compromise between sensitivity and specificity by comparing the diagnostic performance of different tests or diagnostic criteria available. Receiver operating characteristic (or receiver operator characteristic, ROC) curves allow systematic and intuitively appealing descriptions of the diagnostic performance of a test and a comparison of the performance of different tests or diagnostic criteria. This review will analyse the basic principles underlying ROC curves and their specific application to the choice of optimal parameters on exercise electrocardiographic stress testing. Part II will be devoted to the comparative analysis of various parameters derived from exercise stress testing for the diagnosis of underlying coronary artery disease.

Contributions of myocardial ischemia and heart rate to ST segment changes in patients with or without coronary artery disease

BACKGROUND

ST changes related to ischemia at different heart rates (HRs) have not been well described. We aimed to analyze ST dynamic changes by vectorcardiography (VCG) during pacing-induced HR changes for subjects with proven coronary artery disease (CAD) and without (non-CAD).

METHODS

Symptomatic CAD patients scheduled for elective surgery were enrolled along with a non-CAD group. During anesthesia, both groups were placed at multiple ascending levels. VCG ST data, and in particular in ST change vector magnitude (STC-VM) from baseline, along with arterial and great coronary artery vein (GCV) blood samples were collected to determine regional myocardial lactate production.

RESULTS

A total of 35 CAD and 10 non-CAD patients were studied over six incremental 10 beat/min HR increases. STC-VM mean levels increased in the CAD group from 9+/-5 to 131+/-37 microV (standard deviation) compared with non-CAD subjects with 8+/-3-76+/-34 microV. Myocardial ischemia (lactate production) was noted at higher HRs and the positive predictive value for STC-VM to detect ischemia was 58% with the negative predictive value being 88%. STC-VM at 54 microV showed a sensitivity of 88% and a specificity of 75% for identification of ischemia.

CONCLUSIONS

Both HR and ischemia at higher HRs contribute to VCG ST elevation. Established ST ischemia detection concerning HR levels is suboptimal, and further attention to the effects of HR on ST segments is needed to improve electrocardiographic ischemia criteria.

Comparison of the prognostic value of the stress-recovery index versus standard electrocardiographic criteria in patients with a negative exercise electrocardiogram

To verify whether the stress recovery index (SRI) improves risk stratification in patients with a negative exercise electrocardiogram (ECG) using standard criteria, the SRI was derived in 708 consecutive patients with a negative exercise ECG. All-cause mortality and the combination of death or nonfatal myocardial infarction were target end points. The individual effect of clinical and exercise testing data on outcome was evaluated using Cox regression analysis with separate models for each group of variables. Model validation was performed using bootstrap adjusted by degree of optimism in estimates. Survival analysis was performed using a product-limit Kaplan-Meier method. During a 37-month follow-up, 22 deaths and 40 nonfatal acute coronary syndromes occurred. After adjusting for confounding variables, age (hazard ratio 1.62, 95% confidence interval [CI] 1.14 to 2.31 for interquartile difference), hypertension (hazard ratio 1.74, 95% CI 1.04 to 2.89), and SRI (hazard ratio 0.75, 95% CI 0.65 to 0.86 for interquartile difference) were predictive of death or nonfatal myocardial infarction. Moreover, SRI increased the prognostic power of the model on top of clinical and exercise testing variables and provided significant discrimination of survival. In conclusion, the SRI may help refine the prognostic stratification of patients with a negative exercise test result using standard electrocardiographic criteria.

Cycle-ergometry stress testing and use of chronotropic reserve adjustment of ST depression for identification of significant coronary artery disease in clinical practice

Diagnostic reliability of indexations of peak exercise ST segment depression (DeltaST) for heart rate reserve (HRi) or chronotropic reserve (CR) to identify significant coronary artery disease (CAD) by cycle-ergometer exercise testing has not been evaluated previously. Exercise testing by upright cycle-ergometer (25 W/3 min) were performed in consecutive patients in primary prevention with history of exercise-related chest discomfort and cardiovascular risk factors, or with overt peripheral artery disease, with or type-2 diabetes associated with two or more additional cardiovascular risk factors. Coronary angiography was performed after the test to assess significant CAD. Three different criteria for definition of inducible myocardial ischemia were tested versus significant CAD: peak DeltaST>or=100 microV, ST/HRi>1.69 microV/bpm or ST/CR>1.76 microV/%. Diagnostic accuracy vs. CAD of DeltaST>or=100 microV, of ST/HRi>1.69 microV/bpm, and of ST/CR>1.76 microV/% were 78%, 72%, and 89% respectively; sensitivity and specificity of the three criteria were 91% and 50%, 84% and 43%, 88% and 93%, respectively. Abnormal ST/CR predicted CAD independent of risk factors, pre-test probability, and more strongly than DeltaST. Combination of ST/HRi and ST/CR criteria did not improve CAD prediction. In conclusions, in clinical setting in patients in primary prevention but with moderate-to-high pre-test probability of CAD, exercise testing by cycle-ergometry and use of ST/CR>1.76 microV/% showed elevated sensitivity and specificity, and the best accuracy for diagnosis of significant CAD.

Exercise-induced QT/R-R–interval hysteresis as a predictor of myocardial ischemia

OBJECTIVES

Exercise-induced QT/RR hysteresis exists when, for a given R-R interval, the QT interval duration is shorter during recovery after exercise than during exercise. We sought to assess the association between QT/RR hysteresis and imaging evidence of myocardial ischemia.

BACKGROUND

Because ischemia induces cellular disturbances known to decrease membrane action potential duration, we hypothesized a correlation between QT/RR and myocardial ischemia.

METHODS

We digitally analyzed 4-second samples of QT duration and R-R-interval duration in 260 patients referred for treadmill exercise stress and rest single photon emission computed tomography myocardial perfusion imaging; a cool-down period was used after exercise. None of the patients were in atrial fibrillation or used digoxin, and none had marked baseline electrocardiographic abnormalities. Stress and rest myocardial perfusion images were analyzed visually and quantitatively to define the extent and severity of stress-induced ischemia. QT/RR hysteresis was calculated using a computerized algorithm.

RESULTS

There were 82 patients (32%) who manifested myocardial ischemia by single photon emission computed tomography myocardial perfusion imaging. The likelihood of ischemia increased with increasing QT/RR hysteresis, with prevalence according to quartiles of 20%, 30%, 26%, and 49% (P = .003 for trend). In analyses adjusting for ST-segment changes, exercise capacity, heart rate recovery, and other confounders, QT/RR hysteresis was independently predictive of presence of myocardial ischemia (adjusted odds ratio for 100-point increase of QT/RR hysteresis, 1.61; 95% confidence interval, 1.22-2.12; P = .0008). QT/RR hysteresis was also predictive of severe ischemia.

CONCLUSION

Exercise-induced QT/RR hysteresis is a strong and independent predictor of myocardial ischemia and provides additional information beyond that afforded by standard ST-segment measures.

Exercise testing in asymptomatic adults: a statement for professionals from the American Heart Association Council on Clinical Cardiology, Subcommittee on Exercise, Cardiac Rehabilitation, and Prevention

Along with coronary artery calcium scanning, ankle-brachial index measurement, and carotid artery ultrasound, exercise electrocardiography has been proposed as a screening tool for asymptomatic subjects thought to be at intermediate risk for developing clinical coronary disease. A wealth of data indicate that exercise testing can be used to assess and refine prognosis, particularly when emphasis is placed on nonelectrocardiographic measures such as exercise capacity, chronotropic response, heart rate recovery, and ventricular ectopy. Nevertheless, randomized trial data on the clinical value of screening exercise testing are absent; that is, it is not known whether a strategy of routine screening exercise testing in selected subjects reduces the risk for premature mortality or major cardiac morbidity. The writing group believes that a large-scale randomized trial of such a strategy should be performed.

Improved capacity of exercise electrocardiography in the detection of coronary artery disease by focusing on diagnostic variables during the early recovery phase

The temporal distribution of the diagnostic information for the detection of coronary artery disease (CAD) provided by exercise-induced electrocardiographic (ECG) ST-segment amplitude changes in different ECG leads in men and women has not been fully investigated. To shed further light in this area, 1877 electrocardiograms selected from 8322 patients undergoing a routine exercise test on a bicycle ergometer were evaluated. ST-segment amplitude and the difference between heart rate-matched recovery and exercise ST-segment amplitudes (ST/HR difference) were measured. Coronary artery disease was verified angiographically in 669 patients and excluded in 1208 patients by angiography (n = 119), by myocardial scintigraphy (n = 250), or on clinical grounds (n = 839). The diagnostic performance of the 2 ECG methods used was assessed by constructing receiver operating characteristic curves for each sampling point every 12 seconds during 10 minutes of recovery as well as the last 4 minutes of exercise for the ST-segment amplitude. ST-segment amplitude performed better after exercise than during exercise and best within the first 2 minutes of recovery. Its diagnostic ability did not differ from the ST-amplitude hysteresis assessed by the difference between recovery ST-segment amplitude and exercise ST-segment amplitude at matched heart rate. Both methods performed better in men and the diagnostic information appeared mainly in leads I, -aVR, II, V 4 , V 5 , and V 6 . The best discrimination of CAD is provided by analysis of ST-segment amplitude changes in 6 specific leads early during the recovery phase. This information should be targeted by exercise ECG diagnostic methods.

Coronary artery disease diagnosis based on exercise electrocardiogram indexes from repolarisation, depolarisation and heart rate variability

Several indexes have been reported to improve the accuracy of exercise test electrocardiogram (ECG) analysis in the diagnosis of coronary artery disease (CAD), compared with the classical ST depression criterion. Some of them combine repolarisation measurements with heart rate (HR) information (such as the so-called ST/HR hysteresis); others are obtained from the depolarisation period (such as the Athens QRS score); finally, there are heart rate variability (HRV) indexes that account for the nervous system activity. The aim of this study was to identify the best exercise ECG indexes for CAD diagnosis. First, a method to automatically estimate repolarisation and depolarisation indexes in the presence of noise during a stress test was developed. The method is divided into three stages: first, a preprocessing step, where QRS detection, filtering and baseline beat rejection are applied to the raw ECG, prior to a weighted averaging; secondly, a post-processing step in which potentially noisy averaged beats are identified and discarded based on their noise variance; finally, the measurement step, in which ECG indexes are computed from the averaged beats. Then, a multivariate discriminant analysis was applied to classify patients referred for the exercise test into two groups: ischaemic (positive coronary angiography) and low-risk (Framingham risk index < 5%). HR-corrected repolarisation indexes improved the sensitivity (SE) and specificity (SP) of the classical exercise test (SE = 90%, SP = 79% against SE = 65%, SP = 66%). Depolarisation indexes also achieved an improvement over ST depression measurements (SE = 78%, SP = 81%). HRV indexes obtained the best classification results in our study population (SE = 94%, SP = 92%) by means of the very high-frequency power (VHF) (0.4-1 Hz) at stress peak.

Relation between platelet response to exercise and coronary angiographic findings in patients with effort angina

BACKGROUND

Platelet reactivity is increased by exercise in patients with obstructive coronary artery disease (CAD) but not in patients with syndrome X. In this study, we prospectively investigated whether the platelet response to exercise might help distinguish, among patients with angina, those with obstructive CAD from those with normal coronary arteries (NCAs).

METHODS AND RESULTS

Venous blood samples were collected before and 5 minutes after exercise from 194 consecutive patients with stable angina. Platelet reactivity was measured by the platelet function analyzer (PFA)-100 system as the time for flowing whole blood to occlude a collagen-adenosine diphosphate ring (closure time). Coronary angiography showed CAD in 163 patients (84%) and NCA in 31 patients (16%). Baseline closure time was shorter in NCA patients (78.0+/-16 versus 95.5+/-23 seconds, P<0.0001). With exercise, closure time decreased in CAD patients (-15.5 seconds; 95% confidence limits [CL], -13.0 to -18.0 seconds; P<0.0001), but increased in NCA patients (12.5 seconds; 95% CL, 7.4 to 17.7 seconds; P=0.0004). An increase in closure time with exercise > or =10 seconds had 100% specificity and positive predictive value for NCAs. Similarly, a decrease > or =10 seconds had 100% specificity and positive predictive value for CAD. A closure time change (increase or decrease) > or =10 seconds allowed a correct classification of 55% of all patients.

CONCLUSIONS

Among patients with stable angina, the response of platelet reactivity to exercise was predictive of normal or stenosed coronary arteries at angiography. Specifically, an increase in closure time with exercise > or =10 seconds was invariably associated with the presence of NCA.

Safety of local delivery of low- and intermediate-dose adenovirus gene transfer vectors to individuals with a spectrum of morbid conditions

To help define the safety profile of the use of adenovirus (Ad) gene transfer vectors in humans, this report summarizes our experience since April 1993 of the local administration of E1(-)/E3(-) Ad vectors to humans using low (<10(9) particle units) or intermediate (10(9)-10(11) particle units) doses. Included in the study are 90 individuals and 12 controls, with diverse comorbid conditions, including cystic fibrosis, colon cancer metastatic to liver, severe coronary artery disease, and peripheral vascular disease, as well as normals. These individuals received 140 different administrations of vector, with up to seven administrations to a single individual. The vectors used include three different transgenes (human cystic fibrosis transmembrane conductance regulator cDNA, E. coli cytosine deaminase gene, and the human vascular endothelial growth factor 121 cDNA) administered by six different routes (nasal epithelium, bronchial epithelium, percutaneous to solid tumor, intradermal, epicardial injection of the myocardium, and skeletal muscle). The total population was followed for 130.4 patient-years. The study assesses adverse events, common laboratory tests, and long-term follow-up, including incidence of death or development of malignancy. The total group incidence of major adverse events linked to an Ad vector was 0.7%. There were no deaths attributable to the Ad vectors per se, and the incidence of malignancy was within that expected for the population. Overall, the observations are consistent with the concept that local administration of low and intermediate doses of Ad vectors appears to be well tolerated.

Postexercise ischemia is associated with increased neuropeptide Y in patients with coronary artery disease

BACKGROUND

Neurohormones may influence vascular tone both during and after exercise. Neuropeptide Y (NPY), which is costored and released with norepinephrine (NE) during sympathetic activity, is a potent vasoconstrictor with a relatively long half-life. We therefore examined its possible association with the ischemic response to exercise in patients with coronary artery disease.

METHODS AND RESULTS

Twenty-nine male patients with effort-induced angina pectoris underwent a symptom-limited exercise test. In addition to conventional ST-segment analysis, we examined ischemia on the basis of heart rate (HR)-adjusted ST-segment changes through calculation of the ST/HR slope during the final 4 minutes of exercise and of the ST/HR recovery loop after exercise. Blood samples were taken before, during, and after exercise for an analysis of several neurohormones. Mean ST-segment depression was -223+/-20.2 microV (P:<0.0001) just before the termination of exercise, followed by a gradual normalization, but it remained significant after 10 minutes (-49+/-8.9 microV, P:<0.0001). At the end of exercise, the ST/HR slope, which reflects myocardial ischemia, was -6.0+/-0.77 microV/HR. In most patients, ST-segment levels at a given HR were lower during recovery than during exercise, here referred to as ST "deficit." Exercise increased the plasma levels of NPY, NE, epinephrine, and N-terminal proatrial natriuretic peptide, but big endothelin remained unchanged. Although NE and epinephrine peaked at maximal exercise, the highest levels of NPY and N-terminal proatrial natriuretic peptide were observed 4 minutes after exercise. The maximal increase in the NPY correlated significantly with ST-segment depression at 3 minutes after exercise (r=-0.61, P:= 0.0005), the ST deficit at the corresponding time point (r=-0.66, P:= 0.0001), and the duration of ST-segment depression after exercise (r= 0.42, P:=0.02). In contrast, no such correlations were found for NE.

CONCLUSIONS

The present study has for the first time demonstrated a correlation between plasma NPY levels and the degree and duration of ST-segment depression after exercise in patients with coronary artery disease, which suggests that NPY may contribute to myocardial ischemia in these patients.

Transmyocardial laser revascularization with excimer laser: clinical results at 1 year

BACKGROUND

Transmyocardial laser revascularization, a new strategy for the treatment of diffuse ischemic heart disease, uses laser technology for the theoretical purpose of forming transmyocardial channels in the heart to increase perfusion to ischemic zones. This report summarizes our initial clinical experience with the procedure.

METHODS

Excimer transmyocardial laser revascularization was performed in a reversibly ischemic region of the heart in 15 patients. Ischemia and myocardial viability were evaluated by assessment of symptoms and of results of radionuclide single photon emission computed tomography imaging, exercise tolerance testing, and 24-hour Holter monitoring.

RESULTS

No adverse events occurred as a result of the laser revascularization, although 1 patient with preoperative ventricular arrhythmias died 48 hours postoperatively as a result of refractory ventricular tachycardia. Angina class decreased significantly from base line values in patients who had undergone the procedure (mean Canadian Cardiovascular Association angina class, 3.5+/-0.5 at base line, 1.6+/-0.6 at 1 month, 1.5+/-0.8 at 3 months, 1.9+/-0.9 at 6 months, 1.8+/-0.8 at 12 months; p<0.002), and nitroglycerin requirements were similarly decreased in patients who had undergone laser revascularization (mean g/wk of sublingual nitroglycerin, 19+/-4 at baseline, 5+/-3 at 1 month, 4+/-2 at 3 months, 4+/-2 at 6 months, 2+/-1 at 12 months; p<0.02). Exercise tolerance testing demonstrated increase in exercise duration compared with base line values (mean minutes, 7.4+/-3.1 at base line, 8.0+/-3.9 at 1 month, 8.5+/-4.4 at 3 months, and 9.0+/-3.9 at 12 months; p>0.05); those increases were not large enough to be statistically significant, however.

CONCLUSIONS

Our data are consistent with the concept that excimer transmyocardial laser revascularization in individuals with significant ischemic heart disease appears to be well tolerated, can be performed safely, and may lead to a reduction in ischemic symptomatology.

Heart rate adjustment of ST depression in patients with coronary disease and negative standard exercise tests

Heart rate (HR) adjustment of ST depression (STD) has been shown to correctly classify exercise test findings in up to 85% of normal subjects and patients with "equivocal" electrocardiographic (ECG) responses (> or =100 microV upsloping STD), but the performance of these methods in patients with truly negative ECG responses (<100 microV STD) has not been examined in detail. We reviewed negative standard exercise ECGs in 54 men and women (mean age 61 years) with coronary disease, comprising 16% of consecutive treadmill tests that were performed in 337 patients with angiographic coronary artery disease or stable angina. Mean STD was only 63 +/- 21 microV (0.63 mm) in these negative tests. Despite these subthreshold values for STD, the ST/HR index was abnormal (> or =1.6 microV/bpm) in 27 of 54 patients (50%) when STD was adjusted for the change in HR during exercise. Compared with patients with normal values for HR-adjusted STD, patients with an abnormal ST/HR index were slightly older (64 vs. 58 years, P < 0.05) and demonstrated a trend toward lower exercise duration (10.0 vs. 11.8 min). An abnormal ST/HR index was associated with greater subthreshold STD (73 vs. 53 microV, P < 0.0005) and smaller HR change (35 vs. 56 bpm, P < 0.0001) with exercise. Among the 27 patients with a normal ST/HR index by simple HR adjustment, 11 (44%) had abnormal ST/HR slopes (> or =2.4 microV/bpm) by the more complex linear regression method. Therefore, HR adjustment of STD contributes to the improved sensitivity of the exercise ECG by correct classification of some patients with truly negative standard tests. The magnitude of subthreshold STD and the extent of HR change with exercise both contribute to improved test performance. The increased sensitivity afforded by HR adjustment of STD highlights the importance of the precise measurement of subthreshold STD that is afforded by computerized ECG during exercise testing.

Six-month assessment of a phase I trial of angiogenic gene therapy for the treatment of coronary artery disease using direct intramyocardial administration of an adenovirus vector expressing the VEGF121 cDNA

OBJECTIVE

To summarize the 6-month follow-up of a cohort of patients with clinically significant coronary artery disease who received direct myocardial injection of an E1-E3- adenovirus (Ad) gene transfer vector (Ad(GV)VEGF121.10) expressing the human vascular endothelial growth factor (VEGF) 121 cDNA to induce therapeutic angiogenesis.

BACKGROUND

Therapeutic angiogenesis describes a novel approach to the treatment of vascular occlusive disease that uses the administration of growth factors known to induce neovascularization of ischemic tissues.

METHODS

Direct myocardial injection of Ad(GV)VEGF121.10 into an area of reversible ischemia was carried out in 21 patients as an adjunct to conventional coronary artery bypass grafting (group A, n = 15) or as sole therapy using a minithoracotomy (group B, n = 6).

RESULTS

No evidence of systemic or cardiac-related adverse events related to vector administration was observed up to 6 months after therapy. Trends toward improvement in angina class and exercise treadmill testing at 6-month follow-up in the sole therapy group suggest the effects of this therapy are persistent for > or =6 months.

CONCLUSIONS

This study suggests that direct myocardial administration of Ad(GV)VEGF121.10 appears to be well tolerated in patients with clinically significant coronary artery disease. Initiation of phase II evaluation of this therapy appears warranted.

Angiogenesis gene therapy: phase I assessment of direct intramyocardial administration of an adenovirus vector expressing VEGF121 cDNA to individuals with clinically significant severe coronary artery disease

BACKGROUND

Therapeutic angiogenesis, a new experimental strategy for the treatment of vascular insufficiency, uses the administration of mediators known to induce vascular development in embryogenesis to induce neovascularization of ischemic adult tissues. This report summarizes a phase I clinical experience with a gene-therapy strategy that used an E1(-)E3(-) adenovirus (Ad) gene-transfer vector expressing human vascular endothelial growth factor (VEGF) 121 cDNA (Ad(GV)VEGF121.10) to induce therapeutic angiogenesis in the myocardium of individuals with clinically significant coronary artery disease.

METHODS AND RESULTS

Ad(GV)VEGF121.10 was administered to 21 individuals by direct myocardial injection into an area of reversible ischemia either as an adjunct to conventional coronary artery bypass grafting (group A, n=15) or as sole therapy via a minithoracotomy (group B, n=6). There was no evidence of systemic or cardiac-related adverse events related to vector administration. In both groups, coronary angiography and stress sestamibi scan assessment of wall motion 30 days after therapy suggested improvement in the area of vector administration. All patients reported improvement in angina class after therapy. In group B, in which gene transfer was the only therapy, treadmill exercise assessment suggested improvement in most individuals.

CONCLUSIONS

The data are consistent with the concept that direct myocardial administration of Ad(GV)VEGF121.10 to individuals with clinically significant coronary artery disease appears to be well tolerated, and initiation of phase II evaluation of this therapy is warranted.

Significance of exercise QT dispersion in patients with coronary artery disease who do not have exercise-induced ischemic ST-segment changes

The poor sensitivity and the poor predictive value of ST-segment depression have limited the usefulness of the exercise electrocardiogram (ECG) in the diagnosis and evaluation of coronary artery disease (CAD). The QT dispersion (QTD), recorded as the difference between maximal and minimal QT intervals on a 12-lead exercise ECG, is sensitive to myocardial ischemia and may improve the accuracy of exercise testing in patients with CAD who do not show an ST-segment depression. Exercise ECGs were analyzed in 50 subjects who had undergone coronary angiography for clinical indications. None of them showed an ST-segment depression during or after exercise: There were 25 patients with significant coronary artery stenosis and 25 without significant stenosis. The QTD measured before, immediately after, and 1 min after exercise was similar in the 2 groups. The QTD at 3 and 5 min after exercise was significantly greater in patients with CAD than in the controls, and the most marked difference in QTD was observed at 3 min after exercise. A QTD at 3 min after exercise of >60 ms had a sensitivity of 80% and specificity of 88% regarding the diagnosis of CAD. When a deltaQTD (post-exercise QTD minus QTD at rest) at 3 min after exercise of >0 ms was added to a QTD of >60 ms as a condition for positivity, the specificity increased to 96%. QTD measured at 3 min after exercise increases the accuracy of exercise testing in patients with CAD who do not show an ST-segment depression.

Predicting severe angiographic coronary artery disease using computerization of clinical and exercise test data

Currently the standard exercise test is shifting from being a tool for the cardiologist to utilization by the nonspecialist. This change could be facilitated by computerization similar to the interpretation programs available for the resting ECG. Therefore, we sought to determine if computerization of both exercise ECG measurements and prediction equations can substitute for visual analysis performed by cardiologists to predict which patients have severe angiographic coronary artery disease. We performed a retrospective analysis of consecutive patients referred for evaluation of possible or known coronary artery disease who underwent both exercise testing with digital recording of their exercise ECGs and coronary angiography at two university-affiliated Veteran's Affairs medical centers and a Hungarian hospital. There were 2,385 consecutive male patients with complete data who had exercise tests between 1987 and 1997. Measurements included clinical and exercise test data, and visual interpretation of the ECG paper tracings and > 100 computed measurements from the digitized ECG recordings and compilation of angiographic data from clinical reports. The computer measurements had similar diagnostic power compared with visual interpretation. Computerized ECG measurements from maximal exercise or recovery were equivalent or superior to all other measurements. Prediction equations applied by computer were only able to correctly classify two or three more patients out of 100 tested than ECG measurements alone. beta-Blockers had no effect on test characteristics while ST depression on the resting ECG decreased specificity. By setting probability limits using the scores from the equations, the population was divided into high-, intermediate-, and low-probability groups. A strategy using further testing in the intermediate group resulted in 86% sensitivity and 85% specificity for identifying patients with severe coronary disease. We conclude that computerized exercise ST measurements are comparable to visual ST measurements by a cardiologist and computerized scores only minimally improved the discriminatory power of the test. However, using these scores in a stratification algorithm allows the nonspecialist physician to improve the discriminatory characteristics of the standard exercise test even when resting ST depression is present. Computerization permitted accurate identification of patients with severe coronary disease who require referral.

Association of chronotropic incompetence with echocardiographic ischemia and prognosis

OBJECTIVES

This study sought to examine the prognostic importance of chronotropic incompetence among patients referred for stress echocardiography.

BACKGROUND

Although chronotropic incompetence has been shown to be predictive of an adverse prognosis, it is not clear if this association is independent of exercise-induced myocardial ischemia.

METHODS

Consecutive patients (146 men and 85 women; mean age 57 years) who were not taking beta-adrenergic blocking agents and were referred for symptom-limited exercise echocardiography were followed for a mean of 41 months. Chronotropic incompetence was assessed in two ways: (1) failure to achieve 85% of the age-predicted maximum heart rate and (2) a low chronotropic index, a heart rate response measure that accounts for effects of age, resting heart rate and physical fitness.

RESULTS

The primary end point, a composite of death, nonfatal myocardial infarction, unstable angina and late (>3 months after the exercise test) myocardial revascularization, occurred in 41 patients. Failure to achieve 85% of the age-predicted maximum heart rate was predictive of events (relative risk [RR] 2.47, 95% confidence interval [CI] 1.28 to 4.79, p=0.007); similarly, a low chronotropic index was predictive (RR 2.44, 95% CI 1.31 to 4.55, p=0.005). Even after adjusting for myocardial ischemia and other possible confounders, failure to achieve 85% of age-predicted maximum heart rate was predictive (adjusted RR 2.20, 95% CI 1.11 to 4.37, p=0.02). A low chronotropic index also remained predictive (adjusted RR 1.85, 95% CI 0.98 to 3.47, p=0.06).

CONCLUSIONS

Chronotropic incompetence is predictive of an adverse cardiovascular prognosis even after adjusting for echocardiographic myocardial ischemia.

Can computerization of the exercise test replace the cardiologist?

BACKGROUND

The type of practitioners who use the standard exercise test is changing. Once a tool of the cardiologist, the standard exercise test is now being performed by internists and other noncardiologists. Because this change could be facilitated by computerization similar to the computerized interpretation programs available for the resting electrocardiograph (ECG), we performed this analysis. A secondary aim was to demonstrate the effects of medication status and resting ECG abnormalities on test diagnostic characteristics because these factors affect utility of the exercise test by the generalist.

METHODS AND RESULTS

A retrospective analysis was performed of consecutive patients referred at 2 university-affiliated Veteran's Affairs Medical Centers and a Hungarian Hospital for evaluation of chest pain and possible ischemic heart disease. There were 1384 consecutive male patients without a prior myocardial infarction with complete data who had exercise tests and coronary angiography between 1987 and 1997. Measurements included clinical, exercise test data, and visual interpretation of the ECG recordings as well as more than 100 computed measurements from the digitized ECG recordings and compilation of angiographic data from clinical reports. The computer measurements had similar diagnostic power compared with visual interpretation. Computerized measurements from maximal exercise or recovery were equivalent or superior to all other measurements. Prediction equations applied by computer were superior to single ECG measurements. Beta-blockers had no effect on test characteristics, whereas resting ST depression was associated with decreased specificity and increased sensitivity.

CONCLUSIONS

Computerized exercise ST measurements are comparable to visual ST measurements by a cardiologist; computerized scores that included clinical and exercise test results exhibited the greatest diagnostic power. Applying scores with a computer allows the practicing physician to improve the diagnostic characteristics of the standard exercise test. This approach is successful even when there is resting ST depression, thus lessening the need for more expensive nuclear or imaging studies.

Relation of exercise-induced myocardial ischemia to cardiac and carotid structure

There is a strong relation of carotid atherosclerosis to coronary artery disease and left ventricular hypertrophy. In addition, abnormalities of carotid structure are strongly associated with abnormal left ventricular geometry and structure. However, little is known regarding the relation of exercise-induced ST depression to carotid atherosclerosis, carotid, or left ventricular structure in the absence of apparent coronary disease. The relationship of exercise ECG myocardial ischemia to the presence of carotid atherosclerosis and to carotid and left ventricular structure was assessed in 204 asymptomatic subjects free of clinical evidence of cardiovascular disease. Myocardial ischemia on the exercise ECG, defined by a chronotropically adjusted ST/HR slope of >3.47 microV/bpm, was associated with a nearly threefold greater likelihood of discrete carotid atherosclerosis (50% [6 of 12] versus 17% [29 of 192], P=.007) and with older age, male sex, higher systolic and diastolic blood pressures, greater left ventricular mass and mass index, and greater common carotid artery intimal-medial thickness and cross-sectional area index. Stepwise logistic regression analyses, including standard risk factors, revealed that only carotid artery cross-sectional area index (P=.0007) and systolic blood pressure (P=.005) independently predicted an abnormal chronotropically adjusted ST/heart rate slope. Moreover, among 132 subjects with > or = 10 microV of ST-segment depression, only left ventricular mass index and carotid artery cross-sectional area index were significant predictors of the chronotropically adjusted ST/heart rate slope response. Subendocardial ischemia on the exercise ECG is strongly associated with the presence of carotid atherosclerosis and is related to systolic blood pressure, carotid artery cross-sectional area index, and left ventricular mass index, independent of age, sex, and other cardiac risk factors. These findings provide additional insights into the relation between coronary and carotid atherosclerosis and suggest that an association among ischemia and left ventricular and carotid structural abnormalities may contribute to the pathogenesis of coronary events.

Accuracy of heart rate-adjusted ST segments in populations with and without posttest referral bias

We compared the accuracy of the ST segment/heart rate (STHR) index and slope to standard criteria (> or =1 mm horizontal/downsloping ST-segment depression at J + 60 msec) in 1358 patients (152 underwent angiography). All exercise tests used the Cornell protocol and computer measurements of maximum ST-segment depression at J + 60 msec. Test accuracy was determined for the entire group with a probability-based method. Thresholds with equal specificity to standard criteria were determined. By using only patients who underwent angiography, neither STHR index nor slope was more accurate than standard criteria (maximum sensitivity: standard criteria, 42%; STHR index, 51%; STHR slope, 40%). However, by using the entire group, both STHR index and slope were more accurate than standard criteria, but only STHR index achieved statistical significance (maximum sensitivity: standard criteria, 31%; STHR index, 60%; STHR slope, 47%). We conclude that heart rate-adjusted ST-segment criteria are more accurate than standard ST-segment criteria. A lack of demonstration of improved accuracy of STHR index and slope only occurs in patients affected by posttest referral bias.