QRST changes during and after percutaneous transluminal coronary angioplasty

Body Surface Potential Mapping: Contemporary Applications and Future Perspectives

Body surface potential mapping (BSPM) is a noninvasive modality to assess cardiac bioelectric activity with a rich history of practical applications for both research and clinical investigation. BSPM provides comprehensive acquisition of bioelectric signals across the entire thorax, allowing for more complex and extensive analysis than the standard electrocardiogram (ECG). Despite its advantages, BSPM is not a common clinical tool. BSPM does, however, serve as a valuable research tool and as an input for other modes of analysis such as electrocardiographic imaging and, more recently, machine learning and artificial intelligence. In this report, we examine contemporary uses of BSPM, and provide an assessment of its future prospects in both clinical and research environments. We assess the state of the art of BSPM implementations and explore modern applications of advanced modeling and statistical analysis of BSPM data. We predict that BSPM will continue to be a valuable research tool, and will find clinical utility at the intersection of computational modeling approaches and artificial intelligence.

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.

QRS prolongation in the prediction of clinical cardiac events in patients with acute heart failure: analysis of data from the Korean Acute Heart Failure Registry

OBJECTIVES

A prolonged QRS duration has been associated with an unfavorable prognosis in chronic compensated heart failure (HF). However, its predictive value during an admission for acute HF is limited, even in HF with a preserved ejection fraction (EF). The purpose of this study was to evaluate the prognostic utility of the QRS duration in acute HF.

METHODS

Analyses were performed using data from 1,489 patients with a 2-year follow-up. The patients were selected from the Korean Acute Heart Failure Registry and were divided into three groups according to QRS duration (≤80, 81-119 or ≥120 ms). The all-cause mortality and readmission for HF were assessed.

RESULTS

During the study period, 774 primary events occurred (359 deaths and 415 HF). The event frequencies were higher in patients with a prolonged QRS duration. The increased risk associated with the QRS duration was also demonstrated after adjustment for cardiac outcome variables. The prognostic significance of the QRS duration was demonstrated in patients with reduced EF but not in those with a preserved EF.

CONCLUSIONS

A prolonged QRS duration could be a significant predictor of the 2-year cardiac outcome in patients with acute HF, particularly in those with a reduced EF.

Analysis of QRS loop changes in the beat-to-beat Vectocardiogram of ischemic patients undergoing PTCA

In the present work, we have studied dynamic changes of QRS loop in the Vectocardiogram (VCG) of 80 patients that underwent Percutaneous Transluminal Coronary Angioplasty (PTCA). The VCG was obtained for each patient using the XYZ orthogonal leads of their electrocardiographic (ECG) records acquired before, during and after PTCA procedure. In order to analyze the variations of VCG, it has been proposed in this study the following parameters a) Maximum module of the cardiac depolarization vector, b) Volume, c) and Area of vectocardiographic loop corresponding to the QRS complex of each beat, d) Maximum distance between Centroid and the Loop, e) Angle between the XY plane and the Optimum Plane, f) Relation between the Area and Perimeter. The results obtained indicate that the parameters proposed show significant statistics differences (p-value<0.05) before, during (with some exceptions at the first minute of balloon inflation) and after PTCA. We conclude that the variations observed in the proposed parameters correctly represent not only the morphological changes in the depolarization VCG but also they reflect the modifications in the levels of cardiac ischemia induced by PTCA.

Effect of ischemia on implantable defibrillator intracardiac shock electrograms

INTRODUCTION

Few attempts have been made to extract information from the ventricular electrogram (EGM) recorded by implantable cardioverter defibrillators (ICD) aside from the discrimination of supraventricular tachycardia and ventricular tachycardia. The current study aims to examine the effect of ischemia in the major coronary artery distributions on the shock EGM from ICDs.

METHODS

Domestic crossbred pigs (n = 10, 20-40 kg) were implanted with a dual-coil right ventricular defibrillation system. Through the femoral approach, percutaneous balloon occlusion of the major coronary arteries was performed. The left anterior descending (LAD), left circumflex (LCx), and right coronary (RCA) arteries were occluded in random order for 3-5 minutes with 30-minute periods of reperfusion in between and the shock EGMs were recorded and analyzed.

RESULTS

During peak ischemia, R wave amplitude increased by a mean of 204.3% (P = 0.003), increased by a mean of 73.8% (P = 0.0009), and decreased by a mean of 28.0% (P = 0.109) in the LAD, LCx, and RCA territories, respectively. During peak ischemia ST segments elevated by a mean of 105.3% (P = 0.041), elevated by a mean of 114.9% (P = 0.064), and decreased by a mean of 584.5% (P = 0.006) in the LAD, LCx, and RCA territories, respectively.

CONCLUSIONS

Ischemia affects ICD shock EGMs in a manner that appears to vary depending on the culprit vessel. Our data demonstrate the feasibility of ischemia detection from ICD shock EGMs.

Body surface potential mapping improves detection of ST segment alteration during percutaneous coronary intervention

BACKGROUND

The 12-lead electrocardiogram underestimates ST segment alteration in acute coronary syndromes compared with multi-lead body surface mapping. We assessed whether 80-lead mapping would improve detection of ST alteration during percutaneous coronary intervention.

METHODS

Simultaneous maps and 12-lead electrocardiograms were recorded pre-procedure, during balloon inflation and post-procedure from patients undergoing elective intervention to native coronary arteries. Recordings were obtained from 39 inflations (19 patients). All arteries were successfully stented.

RESULTS

Mean 'lead specific' ST alteration (the difference in ST elevation/depression between pre-procedure and inflation recordings in the lead showing maximal ST alteration) was greater on the map than on electrocardiogram, both for ST elevation (0.16+/-0.02 vs. 0.06+/-0.01 mV; p<0.001) and ST depression (0.11+/-0.017 vs. -0.03+/-0.006 mV; p<0.001). During first inflations (n=19), mean lead specific ST elevation and depression on map were greater than on electrocardiogram (0.20+/-0.034 vs. 0.07+/-0.015 mV; p<0.001 and 0.11+/-0.029 vs. 0.03+/-0.009 mV; p=0.001, respectively). Mapping detected greater summated ST elevation and depression during inflation than electrocardiogram (0.04+/-0.005 vs. 0.021+/-0.003 mV; p<0.001 and 0.026+/-0.004 vs. 0.011+/-0.002 mV; p<0.001, respectively). Qualitative analysis of maps and electrocardiograms showed that 21/39 (53.8%) maps recorded during inflation met criteria for myocardial ischaemia compared with 7/39 (17.9%) electrocardiograms (p<0.001).

CONCLUSION

Body surface mapping compared with the 12-lead electrocardiogram improves detection of myocardial ischaemia during intervention.

Temporal evolution of traditional versus transformed ECG-based indexes in patients with induced myocardial ischemia

The time course of changes in the electrocardiogram as a result of myocardial ischemia induced during prolonged coronary angioplasty has been studied. We have analyzed the electrocardiogram evolution during the occlusion in terms of the Ischemic Changes Sensor, which is a parameter that describes the capacity of different indexes to detect induced changes. Traditional indexes at specific time locations (ST level, T wave amplitude and position, and durations of QT interval and QRS complex) and global indexes (based on the Karhunen-Loève transform as applied to the QRS complex, ST-T complex, ST segment and T wave) have been considered. The global indexes better detected ischemic changes than the traditional indexes. The most sensitive were the index for the ST-T complex (89%) in the Karhunen-Loève transform-derived group and for the ST level (61%) in the traditional group. Changes in the ventricular repolarization period usually appeared earlier (77% of patients) than changes in the depolarization period (23% of patients). A similar percentage of patients exhibited the earliest ischemic changes in the T wave (41%) and in the ST segment (36%). The evolution of the Ischemic Changes Sensor parameters showed that the majority (60%) of the total changes occurred during the first minute of occlusion. The results suggest that the use of global electrocardiogram indexes better reflect ischemic changes than do traditional indexes, such as the ST segment deviation.

Identification of the occluded artery in patients with myocardial ischemia induced by prolonged percutaneous transluminal coronary angioplasty using traditional vs transformed ECG-based indexes

We have studied the spatial properties of ischemic changes as induced by prolonged angioplasty and how the changes are related to different ECG indexes. Indexes based on measurements at specific points in time (ST level at J + 60 ms point, maximal T wave amplitude and position, QT interval, and QRS duration) and global indexes (based on the Karhunen-Loève transform and applied to the QRS complex, ST-T complex, ST segment, and T wave), considering both repolarization and depolarization information, were analyzed. The changes during the occlusion period of the different indexes were used as variables in a multivariate discriminant analysis to determine which indexes showed the best discrimination of the three major occlusion sites (corresponding to LAD, RCA, and LCX coronary arteries). Occlusions in LCX artery were the most difficult to classify. With three local indexes (ST60 level measured in lead V3, T wave amplitude in I, and ST60 in III) it was possible to correctly classify 76% of patients by the occlusion site, and with three KLT-derived indexes (first-order KLT index for ST-T complex in I and for QRS in leads V3 and I) 83% of correct classification was obtained. Using six indexes for local and KLT-derived indexes the correct classification was increased to 85 and 90% of patients, respectively. The use of different ECG indexes (from different intervals) on quasiorthogonal leads permitted the identification of the occluded artery in patients undergoing PTCA and may be extended to more general use.

Comparative study of local and Karhunen-Loève-based ST-T indexes in recordings from human subjects with induced myocardial ischemia

In this work we studied ST-T complex changes in the ECG as result of induced ischemia. The principal aim was to determine whether global changes in the ST-T complex were more sensitive markers of ischemic alterations than those based on measurements of changes at specific locations on ST segment or T wave. High-resolution ECGs from patients undergoing percutaneous transluminal coronary angioplasty in one of the major coronary arteries were analyzed to give a description of the period from the end of active depolarization (QRS complex) to the end of active repolarization (T wave). During artery occlusion traditional local measurements of the ST-T complex were compared to global measurements based on the Karhunen-Loève transform. An ischemic change sensor parameter was estimated for each of the studied indexes showing that global measurements detected changes better in the repolarization period in a larger number of leads and with higher sensitivity (more than 85%) than was done using local measurements (sensitivity of 64% with ST level, 33% with T-wave maximum position, and 37% with T-wave maximum amplitude). Using these global indexes it was found that most cases of ST-segment changes were accompanied by T-wave changes (72% of patients). With the use of traditional indexes 23% of patients showed no changes in the repolarization period, whereas with global indexes this percentage decreased to 8%. Thus a global representation of the entire ST-T complex appears to be more suitable than local measurements when studying the initial stages of myocardial ischemia.