Early detection and diagnosis of acute myocardial infarction: the potential for improved care with next-generation, user-friendly electrocardiographic body surface mapping

Intra- and interpersonal variation in body surface potentials of healthy subjects

Background

Body surface potential mapping (BSPM) can provide a detailed assessment of cardiac electrical activity and might be of potential added benefit in multiple cardiac diseases. Normal intra- and interpersonal variation in BSPM is not clearly described and could be of use in the distinction between normal variation and cardiac disease development.

Objective

The purpose of this study was to describe the effects of normal respiration, changes in body position, repeated electrode placement, and heart rate differences on BSPM signals in a healthy population.

Methods

Sixty-seven-lead BSPM was performed in healthy individuals during the resting supine position, a reclined position of 45°, an exercise-increased heart rate, and a follow-up measurement in the resting supine position after 1 week to determine the effect of repeated electrode placement. R-, S- and T-wave amplitudes in all leads were compared between the baseline supine position and the aforementioned conditions.

Results

Ten subjects were included {5 (50%) male; median age 28 years (interquartile range [IQR] 26-30 years)}. The R-wave showed the greatest amplitude variation across all conditions, with the largest changes caused by repeated electrode placement (maximum decrease -0.63 mV [IQR -0.69 to -0.22 mV]) and normal respiration (maximum increase 0.32 mV [IQR 0.08-0.55 mV]) and the smallest changes due to reclined position (maximum decrease -0.23 mV [IQR -0.28 to -0.15 mV]). Electrodes near standard precordial positions were most affected. The exercise-increased heart rate reduced the R-wave amplitude in left-sided electrodes and increased the S-wave amplitude in middle superior electrodes. T-wave amplitude generally increased after exercise.

Conclusion

Normal intrapersonal variation in BSPM signals was analyzed. Repeated electrode placement and normal respiration caused the largest amplitude changes. These findings may help differentiate normal variation from pathological changes in BSPM.

Door-to-balloon time and cardiac mortality in acute myocardial infarction by total occlusion of the left circumflex artery

BACKGROUND

Acute myocardial infarction (AMI) caused by total occlusion of the left circumflex artery (LCX) can present as non-ST-segment elevation myocardial infarction (NSTEMI). We evaluate whether door-to-balloon time (DBT) is associated with cardiac mortality in patients with total occlusion of the LCX.

PATIENTS AND METHODS

From the Korea Acute Myocardial Infarction Registry, patients with AMI who had total occlusion with a Thrombolysis In Myocardial Infarction flow grade of 0 were included. We determined the factors for delay in primary percutaneous coronary intervention (DBT>90 min) and evaluated cardiac mortality for a median period of 14 months.

RESULTS

Mean DBT was 68 min (interquartile range=50-156 min), and the achievement rate of DBT less than or equal to 90 min was 66.9% in the entire study population. More than half of patients with total occlusion of LCX were presented as NSTEMI (57.7%). Among patients with total occlusion of the LCX, the mean DBT was 136 min (interquartile range=60-484 min), and the achievement rate of DBT less than or equal to 90 min was 42.8%. On multivariate analysis, LCX occlusion was an important factor for DBT more than 90 min (odds ratio: 1.766, P<0.001). Among patients with LCX occlusion, cardiac mortality was higher in patients with ST-segment elevation (6.2 vs. 11.0%, P=0.024).

CONCLUSION

This study showed that LCX occlusion was a significant factor for the delay in primary percutaneous coronary intervention on account of presenting as NSTEMI. Cardiac mortality was not associated with DBT more than 90 min but with ST-segment elevation in AMI patients with total occlusion of the LCX.

High-Resolution Body Surface Potential Mapping in Exercise Assessment of Ischemic Heart Disease

Standard 12-lead ECG exercise testing is commonly used for screening of ischemic heart disease (IHD). We studied if high-resolution body surface potential mapping (HR-BSPM) during exercise offers advantages over current standards in noninvasive evaluation of IHD. This study was carried out on 90 IHD patients and 33 healthy controls. The 67-lead HR-BSPM was recorded at rest and during exercise. Twenty-one ECG parameters including classical ST criteria were compared. The effectiveness of methods was verified based on the results of SPECT and coronary angiography. The most effective parameters in the diagnosis of IHD were: amplitude parameter ΔST60 and δT parameter showing T-wave morphology changes during exercise. The sensitivities/specificities of ΔST60 and δT parameters for the HR-BSPM were 70/69 and 59/62%, while for the standard 12-lead ECG system they were: 63/62 and 59/56%. These results demonstrate the usefulness of HR-BSPM measurements during exercise. HR-BSPM resulted in higher sensitivities and specificities compared to the standard 12-lead exercise test. The advantage was partially associated with observed ischemic changes outside standard precordial leads position that were not visible when using the standard 12-lead exercise test. This justifies research into the optimization of the number and position of ECG leads in exercise testing.

ST-segment changes in high-resolution body surface potential maps measured during exercise to assess myocardial ischemia: a pilot study

INTRODUCTION

The aim of the study was to assess myocardial ischemia by analysis of ST-segment changes in high-resolution body surface potential maps (HR-BSPM) measured at rest and during an exercise stress test.

MATERIAL AND METHODS

The study was carried out on a group of 28 patients with stable coronary artery disease and 15 healthy volunteers. The HR-BSPM were measured at rest and during the exercise stress test on a supine ergometer. The workload was increased in stages by 25 W every 2 min, beginning at 50 W. The maps of ST-segment depression (ST60) were calculated from time averaged recordings at rest and at maximal workload.

RESULTS

The efficiency in detection of myocardial ischemia was higher for HR-BSPM than for standard 12-lead electrocardiography (ECG) when both methods were evaluated by outcomes of coronarography. The sensitivity of HR-BSPM was 82.4% while for the standard 12-lead ECG exercise stress test it was 58.8%. For some patients significant changes in the ST segment were observed at stress HR-BSPM but were not visible in standard 12-lead ECG recorded under the same conditions.

CONCLUSIONS

Obtained high values of sensitivity and specificity in myocardial ischemia detection suggest that maps of ST60 calculated from HR-BSPM can improve detection of patients with ischemic heart disease in comparison to the standard electrocardiographic exercise stress test examinations.

The effect of precordial lead displacement on ECG morphology

Inaccurate electrode placement and differences in inter-individual human anatomies can lead to misinterpretation of ECG examination. The aim of the study was to investigate the effect of precordial electrodes displacement on morphology of the ECG signal in a group of 60 patients with diagnosed cardiac disease. Shapes of ECG signals recorded from precordial leads were compared with signals interpolated at the points located at a distance up to 5 cm from lead location. Shape differences of the QRS and ST-T-U complexes were quantified using the distribution function method, correlation coefficient, root-mean-square error (RMSE), and normalized RMSE. The relative variability (RV) index was calculated to quantify inter-individual variability. ECG morphology changes were prominent in all shape parameters beyond 2 cm distance to precordial leads. Lead V2 was the most sensitive to displacement errors, followed by leads V3, V1, and V4, for which the direction of electrodes displacement plays a key role. No visible changes in ECG morphology were observed in leads V5 and V6, only scaling effect of signal amplitude. The RV ranged from 0.639 to 0.989. Distortions in ECG tracings increase with the distance from precordial lead, which are specific to chosen electrode, direction of displacement, and for ECG segment selected for calculations.

Infarct artery distribution and clinical outcomes in occluded artery trial subjects presenting with non-ST-segment elevation myocardial infarction (from the long-term follow-up of Occluded Artery Trial [OAT])

We hypothesized that the insensitivity of the electrocardiogram in identifying acute circumflex occlusion would result in differences in the distribution of the infarct-related artery (IRA) between patients with non-ST-segment elevation myocardial infarction (NSTEMI) and STEMI enrolled in the Occluded Artery Trial. We also sought to evaluate the effect of percutaneous coronary intervention to the IRA on the clinical outcomes for patients with NSTEMI. Overall, those with NSTEMI constituted 13% (n = 283) of the trial population. The circumflex IRA was overrepresented in the NSTEMI group compared to the STEMI group (42.5 vs 11.2%; p <0.0001). The 7-year clinical outcomes for the patients with NSTEMI randomized to percutaneous coronary intervention and optimal medical therapy versus optimal medical therapy alone were similar for the primary composite of death, myocardial infarction, and class IV congestive heart failure (22.3% vs 20.2%, hazard ratio 1.20, 99% confidence interval 0.60 to 2.40; p = 0.51) and the individual end points of death (13.8% vs 17.0%, hazard ratio 0.82, 99% confidence interval 0.37 to 1.84; p = 0.53), myocardial infarction (6.1 vs 5.1%, hazard ratio 1.11, 99% confidence interval 0.28 to 4.41; p = 0.84), and class IV congestive heart failure (6.7% vs 6.0%, hazard ratio 1.50, 99% confidence interval 0.37 to 6.02; p = 0.45). No interaction was seen between the electrocardiographically determined myocardial infarction type and treatment effect (p = NS). In conclusion, the occluded circumflex IRA is overrepresented in the NSTEMI population. Consistent with the overall trial results, stable patients with NSTEMI and a totally occluded IRA did not benefit from randomization to percutaneous coronary intervention.

Comparison of an automated algorithm to expert physician interpretation of 80-lead body surface mapping in the evaluation of acute myocardial ischemia and infarction in patients presenting to the emergency department with chest pain: results from the Optimal Cardiovascular Diagnostic Evaluation Enabling Faster Treatment of Myocardial Infarction trial

INTRODUCTION/BACKGROUND

Eighty-lead (80 L) body surface map (BSM) technology provides electrocardiogram data for the clinician to interpret. A BSM device also offers an automated interpretation. Little information is available about the performance of automated algorithm interpretation in comparison to human interpretation of the 80 L BSM.

METHODS

Interpretations of BSMs by automated algorithm and a core laboratory of physician readers from The Optimal Cardiovascular Diagnostic Evaluation Enabling Faster Treatment of Myocardial Infarction trial were compared. The κ statistic and its 95% confidence interval for concordance were calculated. The effect of BSM quality on concordance was also analyzed.

RESULTS

3405 maps for 1601 subjects were reviewed by the core laboratory and automated algorithm. There was a combined concordance rate of 87.3% (κ = 0.46; 95% confidence interval, 0.40-0.52). A decrease in signal quality was associated with a decrease in concordance between human and automated algorithm interpretation (κ = 0.52 for good quality vs κ = 0.30 for poor quality).

CONCLUSION

A moderate degree of concordance was noted between physician and automated algorithm interpretation of 80 L BSMs. Signal quality of 80 L electrocardiographic BSM directly affected concordance.

euHeart: personalized and integrated cardiac care using patient-specific cardiovascular modelling

The loss of cardiac pump function accounts for a significant increase in both mortality and morbidity in Western society, where there is currently a one in four lifetime risk, and costs associated with acute and long-term hospital treatments are accelerating. The significance of cardiac disease has motivated the application of state-of-the-art clinical imaging techniques and functional signal analysis to aid diagnosis and clinical planning. Measurements of cardiac function currently provide high-resolution datasets for characterizing cardiac patients. However, the clinical practice of using population-based metrics derived from separate image or signal-based datasets often indicates contradictory treatments plans owing to inter-individual variability in pathophysiology. To address this issue, the goal of our work, demonstrated in this study through four specific clinical applications, is to integrate multiple types of functional data into a consistent framework using multi-scale computational modelling.

Electrocardiologic and related methods of non-invasive detection and risk stratification in myocardial ischemia: state of the art and perspectives

Background: Electrocardiographic methods still provide the bulk of cardiovascular diagnostics. Cardiac ischemia is associated with typical alterations in cardiac biosignals that have to be measured, analyzed by mathematical algorithms and allegorized for further clinical diagnostics. The fast growing fields of biomedical engineering and applied sciences are intensely focused on generating new approaches to cardiac biosignal analysis for diagnosis and risk stratification in myocardial ischemia.

Objectives: To present and review the state of the art in and new approaches to electrocardiologic methods for non-invasive detection and risk stratification in coronary artery disease (CAD) and myocardial ischemia; secondarily, to explore the future perspectives of these methods.

Methods: In follow-up to the Expert Discussion at the 2008 Workshop on "Biosignal Analysis" of the German Society of Biomedical Engineering in Potsdam, Germany, we comprehensively searched the pertinent literature and databases and compiled the results into this review. Then, we categorized the state-of-the-art methods and selected new approaches based on their applications in detection and risk stratification of myocardial ischemia. Finally, we compared the pros and cons of the methods and explored their future potentials for cardiology.

Results: Resting ECG, particularly suited for detecting ST-elevation myocardial infarctions, and exercise ECG, for the diagnosis of stable CAD, are state-of-the-art methods. New exercise-free methods for detecting stable CAD include cardiogoniometry (CGM); methods for detecting acute coronary syndrome without ST elevation are Body Surface Potential Mapping, functional imaging and CGM. Heart rate variability and blood pressure variability analyses, microvolt T-wave alternans and signal-averaged ECG mainly serve in detecting and stratifying the risk for lethal arrythmias in patients with myocardial ischemia or previous myocardial infarctions. Telemedicine and ambient-assisted living support the electrocardiological monitoring of at-risk patients.

Conclusions: There are many promising methods for the exercise-free, non-invasive detection of CAD and myocardial ischemia in the stable and acute phases. In the coming years, these new methods will help enhance state-of-the-art procedures in routine diagnostics. The future can expect that equally novel methods for risk stratification and telemedicine will transition into clinical routine.

Magnitude and consequences of missing the acute infarct-related circumflex artery

Emergent reperfusion strategies are integral to providing optimal patient outcomes in the setting of acute coronary artery occlusion. ST-segment elevation on the surface 12-lead electrocardiogram, although specific as a surrogate marker, is insensitive to acute posterior circulation coronary artery occlusion. Studies of non-ST-segment elevation acute coronary syndrome consistently identify patients who have epicardial vessel occlusion at the time of initial angiography, which is usually delayed for hours or days after the initial presentation. In addition, studies of ST-segment elevation myocardial infarction often divulge a disparity in identification of the infarct-related artery, with an underrepresentation of the left circumflex artery. Taken together, it is likely that many patients with left circumflex artery occlusion are "missed" during the early phases of myocardial infarction due to the electrocardiographically silent nature of the posterior territory, resulting in delayed myocardial salvage and worse cardiovascular outcomes. In this review, we report on the magnitude of missed left circumflex infarction and the consequences of this delay in diagnosis. We review the electrocardiographic findings of left circumflex occlusion and discuss strategies to enhance early identification. Heightened awareness of this clinical scenario and the available methods to avoid missing this elusive diagnosis are imperative in our quest to further improve the outcomes of patients with acute myocardial infarction.

Acute detection of ST-elevation myocardial infarction missed on standard 12-Lead ECG with a novel 80-lead real-time digital body surface map: primary results from the multicenter OCCULT MI trial

STUDY OBJECTIVE

Although 80-lead ECG body surface mapping is more sensitive for ST-elevation myocardial infarction (STEMI) than the 12-lead ECG, its clinical utility in chest pain in the emergency department (ED) has not been studied. We sought to determine the prevalence, clinical care patterns, and clinical outcomes of patients with STEMI identified on 80-lead but not on 12-lead (80-lead-only STEMI).

METHODS

The Optimal Cardiovascular Diagnostic Evaluation Enabling Faster Treatment of Myocardial Infarction trial was a multicenter prospective observational study of moderate- to high-risk chest pain patients presenting to the ED. Patients received simultaneous 12-lead and 80-lead ECGs as part of their initial evaluation and were treated according to the standard of care, with clinicians blinded to the 80-lead results. The primary outcome of the trial was door-to-sheath time in patients with 80-lead-only STEMI versus patients with STEMI identified by 12-lead alone (12-lead STEMI). Secondary outcomes included angiographic and clinical outcomes at 30 days.

RESULTS

One thousand eight hundred thirty patients were evaluated, 91 had a discharge diagnosis of 12-lead STEMI, and 25 patients met criteria for 80-lead-only STEMI. Eighty-four of the 91 12-lead STEMI patients underwent cardiac catheterization, with a median door-to-sheath time of 54 minutes, versus 14 of the 25 80-lead-only STEMI patients, with a door-to-sheath time of 1,002 minutes (estimated treatment difference in median=881; 95% confidence interval 181 to 1,079 minutes). Clinical outcomes and revascularization rates, however, were similar between 80-lead-only STEMI and 12-lead STEMI patients.

CONCLUSION

The 80-lead ECG provides an incremental 27.5% increase in STEMI detection versus the 12-lead. Patients with 80-lead-only STEMI have adverse outcomes similar to those of 12-lead STEMI patients but are treated with delayed or conservative invasive strategies.

Emergency physician high pretest probability for acute coronary syndrome correlates with adverse cardiovascular outcomes

OBJECTIVES

The value of unstructured physician estimate of risk for disease processes, other than acute coronary syndrome (ACS), has been demonstrated. The authors sought to evaluate the predictive value of unstructured physician estimate of risk for ACS in emergency department (ED) patients without obvious initial evidence of a cardiac event.

METHODS

This was a post hoc secondary analysis of the Internet Tracking Registry for Acute Coronary Syndromes (i*trACS), a prospectively collected multicenter data registry of patients over the age of 18 years presenting to the ED with symptoms of ACS between 1999 and 2001. In this registry, following patient history, physical exam, and electrocardiogram (ECG), the unstructured treating physician estimate of risk was recorded. A 30-day follow-up and a medical record review were used to determine rates of adverse cardiac events, death, myocardial infarction (MI), or revascularization procedure. The analysis included all patients with nondiagnostic ECG changes, normal initial biomarkers, and a non-MI initial impression from the registry and excluded those without complete data or who were lost to follow-up. Data were stratified by unstructured physician risk estimate: noncardiac, low risk, high risk, or unstable angina.

RESULTS

Of 15,608 unique patients in the registry, 10,145 met inclusion/exclusion criteria. Patients were defined as having unstable angina in 6.0% of cases; high risk, 23.5% of cases; low risk, 44.2%; and noncardiac, 26.3% of cases. Adverse cardiac event rates had an inverse relationship, decreasing from 22.0% (95% confidence interval [CI] = 18.8% to 25.6%) for unstable angina, 10.2% (95% CI = 9.0% to 11.5%) for those stratified as high risk, 2.2% (95% CI = 1.8% to 2.6%) for low risk, and to 1.8% (95% CI = 1.4% to 2.4%) for noncardiac. The relative risk (RR) of an adverse cardiac event for those with an initial label of unstable angina compared to those with a low-risk designation was 10.2 (95% CI = 8.0 to 13.0). The RR of an event for those with a high-risk initial impression compared to those with a low-risk initial impression was 4.7 (95% CI = 3.8 to 5.9). The risk of an event among those with a low-risk initial impression was the same as for those with a noncardiac initial impression (RR = 0.83, 95% CI = 0.6 to 1.2).

CONCLUSIONS

In ED patients without obvious initial evidence of a cardiac event, unstructured emergency physician (EP) estimate of risk correlates with adverse cardiac outcomes.

The triple work-up for emergency department patients with acute chest pain: how often does it occur?

OBJECTIVES

To measure the degree of overlap and diagnostic yield for evaluations of acute coronary syndrome (ACS), pulmonary embolism (PE), and aortic dissection (AD) among Emergency Department (ED) patients.

METHODS

We conducted a cross-sectional descriptive study of consecutive adult patients seen in the ED of a 78,000-annual-visit urban academic medical center. Patients who had received at least one of eight of the tests used in our ED to diagnose these three diseases were identified through three methods, and a final study population list was created. Overlap of evaluations and diagnostic yields were calculated by simple descriptive statistics.

RESULTS

Over a 2-week period, 626 patient encounters among 622 unique patients were identified. Among these 626 visits, 139 (22%) included diagnostic tests for more than one of the three diagnoses of interest. The majority of these multiple tests were for ACS plus PE (n = 121, 87% of all multiple tests), whereas a minority of patients received tests for ACS plus AD (n = 14, 10% of all multiple tests) or for the "triple work-up" of ACS plus PE plus AD (n = 4, 2.9% of all multiple tests).

CONCLUSION

Although the "triple work-up" evaluation for ACS, PE, and AD is relatively uncommon, a significant number of ED patients who are evaluated for at least one of these three major chest pain syndromes receive simultaneous testing for one of the others.