John J. Wang

Comparison of epicardial potential maps derived from the 12-lead electrocardiograms with scintigraphic images during controlled myocardial ischemia ☆ ☆☆

Our aim was to cross-validate electrocardiographic (ECG) and scintigraphic imaging of acute myocardial ischemia. The former method was based on inverse calculation of heart-surface potentials from the body-surface ECGs, and the latter, on a single photon emission computed tomography (SPECT). A boundary-element torso model with 352 body-surface and 202 heart-surface nodes was used to perform the ECG inverse solution. Potentials at 352 body-surface nodes were calculated from those acquired at 12-lead ECG measurement sites using regression coefficients developed from a design set (n = 892) of body-surface potential mapping (BSPM) data. The test set (n = 18) consisted of BSPM data from patients who underwent a balloon-inflation angioplasty of either the left anterior descending coronary artery (LAD) (n = 7), left circumflex coronary artery (LCx) (n = 2), or the right coronary artery (RCA) (n = 9). Body-surface potential mapping distributions at J point for 352 nodes were estimated from the 12-lead ECG, and an agreement with those estimated from 120 leads was assessed by a correlation coefficient (CC) (in percent). These estimates yielded very similar BSPM distributions, with a CC of 91.0% ± 8.1% (mean ± SD) for the entire test set and 94.1% ± 1.4%, 96.7% ± 0.8%, and 87.4% ± 10.3% for LAD, LCx, and RCA subgroups, respectively. Corresponding heart-surface potential distributions obtained by inverse solution correlated with a lower CC of 69.3% ± 18.0% overall and 73.7% ± 10.8%, 84.7% ± 1.1%, and 62.6% ± 21.8%, respectively, for subgroups. Bulls-eye displays of heart-surface potentials calculated from estimated BSPM distributions had an area of positive potentials that qualitatively corresponded, in general, with the underperfused territory suggested by SPECT images. For the LAD and LCx groups, all 9 ECG-derived bulls-eye images indicated the expected territory; for the RCA group, 6 of 9 ECG-derived images were as expected; 2 of 3 misclassified cases had very small ECG changes in response to coronary-artery occlusion, and their SPECT images showed indiscernible patterns. In conclusion, our findings demonstrate that noninvasive ECG imaging based on just the 12-lead ECG might provide useful estimates of the regions of myocardial ischemia that agree with those provided by scintigraphic techniques.

Atrial fibrillation detection using stationary wavelet transform analysis

Atrial fibrillation (AF) is a common cardiac arrythmia that is usually developed for elder people with aging. AF may result in complications such as chest pain or even heart failure in later stage. Based on the characteristics of surface ECG, AF can be detected by several methods. A particular investigation on the fibrillatory waveform reveals the inherent structure of AF signals. As opposed to traditional frequency domain methods, we utilize the stationary wavelet transform to extract the information from ECG signal which differentiates AF and non-AF cases based on some feature extraction and selection processes. A linear classifier is then designed for computational efficiency. The proposed method eliminates the need for QRST cancellation step which is required for frequency domain methods and provides a more systematic approach for AF detection. Extensive experiments are tested on signals from the MIT-BIH Atrial Fibrillation Database to show the superior performance of the proposed algorithm.

Discrimination of ST deviation caused by acute coronary occlusion from normal variants and other abnormal conditions, using computed electrocardiographic imaging based on 12-lead ECG.

BACKGROUND Many graphical methods for displaying ST-segment deviation in the ECG have been tried for enhancing decision-making in patients with suspected acute coronary syndromes. Computed electrocardiographic imaging (CEI), based on a mathematical inverse solution, has been recently applied to transform ST-J point measurements made in conventional 12-lead ECG into a display of epicardial potentials in bulls-eye format. The purpose of this study is to assess utility of CEI in the clinical setting. METHODS In 99 patients with stable coronary disease, 12-lead ECGs were recorded during elective percutaneous coronary intervention (PCI), first before balloon-catheter insertion and then when an intracoronary balloon blocked blood supply to a region of myocardium for more than 4minutes (typically 5minutes). Four groups of patients were additionally studied, namely those with preexcitation, pericarditis, early repolarization syndrome (ERS), and left ventricular hypertrophy (LVH) with strain. Comparisons between performances of published criteria for ST-elevation myocardial infarction (STEMI) and quantitative as well as visual assessment of CEI images were based on sensitivities and specificities. RESULTS Visual assessment of CEI outperformed STEMI criteria. This was especially evident for the capability of detecting LCx occlusion with sensitivities for STEMI criteria=35% and for visual assessment of CEI by 2 physicians=71%, i. e. twice as many patients were correctly identified by CEI. False positive rates for CEI were low in patients with LVH with strain as well as with preexcitation for both methods. For pericarditis and ERS, visual as well as quantitative assessment of CEI performed better than STEMI criteria. CONCLUSION Visual assessment of CEI is a promising method for increasing the accuracy of ECG-based triage to PCI or conservative care.

Detection of myocardial ischemia by vessel-specific leads derived from the 12-lead electrocardiogram and its subsets.

Currently used electrocardiographic criteria for identifying patients with ST-elevation myocardial infarction (STEMI) perform with high specificity but low sensitivity. Our aim was to enhance ischemia-detection ability of conventional STEMI criteria based on 12-lead electrocardiogram (ECG) by adding new criteria using 3 vessel-specific leads (VSLs) derived from 12-lead ECG. Study data consisted of 12-lead ECGs acquired during 99 ischemic episodes caused by balloon inflation in, respectively, left anterior descending coronary artery (LAD; n = 35), right coronary artery (RCA; n = 47), and left circumflex coronary artery (LCx; n = 17). ST deviation was measured at J point in 12 standard leads, and for 3 VSLs, its value was derived from 12-lead ECG by using 8 independent predictor leads or just a pair of precordial leads combined with a pair of limb leads. Mean values of sensitivity (SE) and specificity (SP) of ischemia detection achieved with conventional STEMI vs VSL criteria were then obtained from bootstrap trials. We found that the detection of ischemic state by conventional criteria achieved the mean SE/SP of 60%/96% in the total set of ischemic episodes, 74%/97% in the LAD subgroup, 60%/94% in the RCA subgroup, and 36%/100% in the LCx subgroup. In comparison, the mean SE/SP values of VSLs derived from 8 independent leads of 12-lead ECG were, at 125-microV threshold, 76%(*)/96% in the total set, 91%(*)/97% in the LAD subgroup, 70%/94% in the RCA subgroup, and 71%(*)/100% in the LCx subgroup (with asterisk denoting a statistically significant increase). The mean SE/SP of VSLs derived from some of the 4-predictor lead sets (namely, those including lead V(3)) matched or exceeded values achieved by VSLs derived from 8 predictors; for instance, with predictor leads I, II, V(3), V(6) derived VSLs attained at 125-microV threshold the mean SE/SP of 80%(*)/95% in the total set, 91%(*)/97% in the LAD subgroup, 74%/92% in the RCA subgroup, and 71%(*)/100% in the LCx subgroup. Based on these results, we conclude that, in our data set, 3 VSLs derived from the complete standard 12-lead ECG-and even from its subsets-can identify acute ischemia better than existing STEMI criteria.

Validation of the vessel-specific leads (VSLs) for acute ischemia detection on a dataset with non-ischemic ST-segment deviation

Existing criteria recommended by ACC/ESC for identifying patients with ST-elevation myocardial infarction (STEMI) from the 12-lead ECG perform with high specificity (SP), but low sensitivity (SE). In our previous study, we found that the SE of acute ischemia detection can be markedly improved without any loss of SP by calculating, from the 12-lead ECG, ST elevation in 3 vessel-specific leads (VSLs). To further validate the method, we evaluated the SP using a dataset with non-ischemic ST-segment changes, consisting of 12-lead ECGs of 100 patients. These ECGs were chosen to represent five causes of pathological ST deviation, other than acute coronary occlusion: ventricular pre-excitation, acute pericarditis, early-repolarization syndrome, left ventricular hypertrophy, and left bundle branch block. Both STEMI and VSL criteria were tested by calculating SP as the performance measure. We found that SP of the STEMI criteria was 100%, 4%, 29%, 100%, and 64%, respectively, for the five subgroups. The corresponding values of SP for the VSLs were 92%, 88%, 100%, 77%, and 68%. For the entire group, SP was 57% for the STEMI criteria and significantly higher for the VSLs at 83%. Thus, the VSLs not only are more sensitive in detecting acute ischemia, but also significantly more specific in rejecting patients with non-ischemic ST deviation than the existing STEMI criteria.

Criteria for ECG detection of acute myocardial ischemia: Sensitivity versus specificity

BACKGROUND Criteria for electrocardiographic detection of acute myocardial ischemia recommended by the Consensus Document of ESC/ACCF/AHA/WHF consist of two parts: The ST elevation myocardial infarction (STEMI) criteria based on ST elevation (ST↑) in 10 pairs of contiguous leads and the other on ST depression (ST↓) in the same 10 contiguous pairs. Our aim was to assess sensitivity (SE) and specificity (SP) of these criteria-and to seek their possible improvements-in three databases of 12‑lead ECGs. METHODS We used (1) STAFF III data of controlled ischemic episodes recorded from 99 patients (pts) during percutaneous coronary intervention (PCI) involving either left anterior descending (LAD) coronary artery, right coronary artery (RCA), or left circumflex (LCx) coronary artery. (2) Data from the University of Glasgow for 58 pts with acute myocardial infarction (AMI) and 58 pts without AMI, as confirmed by MRI. (3) Data from Lund University retrieved from a centralized ECG management system for 100 pts with various pathological ST changes-other than acute coronary occlusion-including ventricular pre-excitation, acute pericarditis, early repolarization syndrome, left ventricular hypertrophy, and left bundle branch block. ST measurements at J-point in ECGs of all 315 pts were obtained automatically on the averaged beat with manual review and the recommended criteria as well as their proposed modifications, were applied. Performance measures included SE, SP, positive predictive value (PPV), and benefit-to-harm ratio (BHR), defined as the ratio of true-positive vs. false-positive detections. RESULTS We found that the SE of widely-used STEMI criteria can be indeed improved by the additional ST↓ criteria, but at the cost of markedly decreased SP. In contrast, using ST↑ in only 3 additional contiguous pairs of leads (STEMI13) can boost SE without any loss of SP. In the STAFF III database, SE/SP/PPV were 56/98/97% for the STEMI, 79/79/79% for the STEMI with added ST↓ and 67/97/96% for the STEMI13. In the Glasgow database, corresponding SE/SP/PPV were 43/98/96%, 84/90/89%, and 55/98/97%. For the Lund database, SP was 56% for the STEMI, 24% for the STEMI with ST↓, and 56% for the STEMI13. CONCLUSION Current recommended criteria for detecting acute myocardial ischemia, involving ST↓, boost SE of widely-used STEMI criteria, at the cost of SP. To keep the SP high, we propose either the adjustment of threshold for the added ST↓ criteria or a selective use of ST↓ only in contiguous leads V2 and V3 plus ST↑ in lead pairs (aVL, -III) and (III, -aVL).