QT interval shortening and ST elevation in intracoronary ECG during PTCA

Accuracy of intracoronary ECG parameters for myocardial ischemia detection

INTRODUCTION

The electrocardiogram (ECG) is a valuable diagnostic tool for the diagnosis of myocardial ischemia during acute coronary syndrome. Aside from the commonly used ST-segment shift indicative of ischemia, several other ECG parameters are pathophysiologically reasonable. Thus, the goal of this study was to assess the accuracy of different ischemia parameters as obtained by the highly susceptible intracoronary ECG (icECG).

METHOD

This was a retrospective observational study in 100 patients with chronic coronary syndrome. From each patient, a non-ischemic as well as ischemic icECG at the end of a one-minute proximal coronary balloon occlusion was available, and analysed twice by three different physicians, as well as once together for consensual results. The evaluated parameters were icECG ST-segment shift (mV), ST-integral (mV*sec), T-wave-integral (mV*sec), T-peak (mV), T-peak-to-end time (TPE; msec) and QTc-time (msec).

RESULTS

All six icECG parameters showed significant differences between the non-ischemic and the ischemic recording. Using the icECG recording during coronary patency or occlusion as criterion for absent or present myocardial ischemia, ROC-analysis of icECG ST-segment shift showed an area under the curve (AUC) of 0.963 ± 0.029 (p < 0.0001). AUC for ST-integral was 0.899 ± 0.044 (p < 0.0001), for T-wave integral 0.791 ± 0.059 (p < 0.0001), for T-peak 0.811 ± 0.057 (p < 0.0001), for TPE 0.667 ± 0.068 (p < 0.0001), and for QTc-time 0.770 ± 0.061 (p < 0.0001). The best cut-off point for the detection of ischemia by icECG ST-segment shift was 0.365 mV (sensitivity 90%, specificity 95%).

CONCLUSION

When tested in a setting with artificially induced absolute myocardial ischemia, icECG ST-segment shift at a threshold of 0.365 mV most accurately distinguishes between absent and present ischemia.

A modeling and machine learning approach to ECG feature engineering for the detection of ischemia using pseudo-ECG

Early detection of coronary heart disease (CHD) has the potential to prevent the millions of deaths that this disease causes worldwide every year. However, there exist few automatic methods to detect CHD at an early stage. A challenge in the development of these methods is the absence of relevant datasets for their training and validation. Here, the ten Tusscher-Panfilov 2006 model and the O’Hara-Rudy model for human myocytes were used to create two populations of models that were in concordance with data obtained from healthy individuals (control populations) and included inter-subject variability. The effects of ischemia were subsequently included in the control populations to simulate the effects of mild and severe ischemic events on single cells, full ischemic cables of cells and cables of cells with various sizes of ischemic regions. Action potential and pseudo-ECG biomarkers were measured to assess how the evolution of ischemia could be quantified. Finally, two neural network classifiers were trained to identify the different degrees of ischemia using the pseudo-ECG biomarkers. The control populations showed action potential and pseudo-ECG biomarkers within the physiological ranges and the trends in the biomarkers commonly identified in ischemic patients were observed in the ischemic populations. On the one hand, inter-subject variability in the ischemic pseudo-ECGs precluded the detection and classification of early ischemic events using any single biomarker. On the other hand, the neural networks showed sensitivity and positive predictive value above 95%. Additionally, the neural networks revealed that the biomarkers that were relevant for the detection of ischemia were different from those relevant for its classification. This work showed that a computational approach could be used, when data is scarce, to validate proof-of-concept machine learning methods to detect ischemic events.

A tale of two formulas: Differentiation of subtle anterior MI from benign ST segment elevation

BACKGROUND

It may sometimes be difficult to differentiate subtle ST-segment elevation (STE) due to anterior myocardial infarction (MI) from benign variant (BV) STE. Recently, two related formulas were proposed for this purpose. However, they have never been tested in an external population.

MATERIALS AND METHODS

Consecutive patients from May 2017 to January 2018, who were admitted with the diagnosis of acute anterior STEMI, were enrolled. Electrocardiograms were systematically reviewed and only subtle ones were included. First 200 consecutive patients with noncardiac chest pain were also enrolled as a control group. Relevant electrocardiographic parameters were measured.

RESULTS

A total of 379 anterior MI and 200 BV-STE cases were enrolled during study period. A total of 241 patients in STEMI group were excluded for not matching subtleness criteria, four patients in control group were also excluded because of prior left-anterior descending artery intervention. The three-variable formula, with recommended cut-point of 23.5, had a sensitivity, specificity, and diagnostic accuracy of 73.9%, 86.7%, and 81.4%, respectively. The four-variable formula, with the published cut-point of 18.2, had a sensitivity, specificity, and diagnostic accuracy of 83.3%, 87.7%, and 85.9%, respectively.

CONCLUSION

Three- and four-variable formulas with recommended cutoffs have a reasonable sensitivity, specificity, and diagnostic accuracy in differentiating subtle STEMI with BV-STE. Although both perform well, the four-variable formula has a higher sensitivity, specificity, and diagnostic accuracy and should be preferred.

QT prolongation is an independent predictor of mortality in end-stage renal disease

BACKGROUND

Coronary artery disease (CAD) is the predominant cause of sudden cardiac death in the general population, and sudden cardiac death is the leading cause of mortality in end-stage renal disease (ESRD).

HYPOTHESIS

QT-interval prolongation is an independent prognosticator in ESRD.

METHODS

We reviewed clinical, electrocardiographic, stress test, and coronary angiography data on ESRD patients evaluated for transplantation at our institution between 2000 and 2004 who underwent coronary angiography. The QT interval was corrected for heart rate and QRS duration (QTc). All-cause mortality data were prospectively collected and verified against the Social Security Death Index database.

RESULTS

During 40 +/- 28 months of follow-up, 132 of the 280 (47%) patients died prior to renal transplantation. Patients with a prolonged QTc (39%) had 1-, 3-, and 5-year death-rates of 12%, 36%, and 47%, respectively, vs 8%, 24%, and 36% for those with normal QTc (log-rank P = 0.03). In a multivariate Cox regression model that adjusted for age, gender, diabetes mellitus, myocardial infarction, presence and severity of CAD on angiography, left ventricular (LV) hypertrophy, LV ejection fraction (EF), and multiple other variables, QTc remained to be an independent predictor of survival (hazard ratio [HR]: 1.008, 95% confidence interval [CI]: 1.001-1.014, P = 0.016). Female gender, decreasing LVEF, and decreasing severity of CAD on angiography were independent predictors of prolonged QTc.

CONCLUSIONS

QTc prolongation is an independent predictor of mortality in ESRD patients being evaluated for renal transplantation. The prognostic information gained from the QTc is additive to that provided by the LVEF and the severity of CAD.

Stress-induced QTc-interval shortening as an ancillary marker of ischemia in patients with complete left bundle branch block

BACKGROUND

In patients with left bundle branch block (LBBB), ischemia-induced repolarization changes associated with QTc-interval shortening may be recorded during coronary angioplasty. We aimed to assess whether these repolarization changes may be predictive of severe coronary artery disease in patients with LBBB.

METHODS

Fifty noninfarcted LBBB patients underwent dipyridamole stress test and coronary angiography for chest pain. To localize the site of ischemia, we considered four groups of conventional ECG leads (V1-V2-V3; V4-V5-V6; aVL-I; III-aVF-II), exploring the anteroseptal, lateral, high-lateral, and inferior left ventricular walls. ST-T changes and QTc intervals were estimated at rest and peak stress, lead by lead, in each group of leads and the fractional percentage difference between rest-stress QTc intervals ([DELTA]QTc) was calculated. A [DELTA]QTc greater than -10% was used to define significant QTc-interval shortening. Coronary stenosis of more than 70% and more than 90% were considered 'significant' and 'severe'.

RESULTS

According to dipyridamole stress test response, two groups were identified: group I (35 patients) with dipyridamole-induced ischemia and group II (15 patients) without dipyridamole-induced ischemia. The wall motion score index at peak stress (compared with resting wall motion score index) was significantly higher in group I (1.98 +/- 0.13 vs. 1.28 +/- 0.08, P < 0.0001) than in group II (1.36 +/- 0.18 vs. 1.25 +/- 0.08, P = 0.296). The patients of group I showed a significant QTc-interval shortening ([DELTA]QTc = -16.9 +/- 3.9%), whereas this did not happen in patients of group II ([DELTA]QTc = +8.8 +/- 2.4%, P < 0.0001). The patients of group I also had a more severe stenosis in the vessel related to the stress-induced dyssynergic area (I = 90.5 +/- 9.5 vs. II = 34.3 +/- 31.1%; P < 0.0001).

CONCLUSION

In patients with LBBB, stress-induced pseudonormalization pattern, associated with QTc-interval shortening, allows the identification of cardiac areas supplied by severely stenosed coronary arteries.

Effect of balloon inflation-induced acute ischemia on QT dispersion during percutaneous transluminal coronary angioplasty

BACKGROUND

QT dispersion (QTd = QTmax-QTmin) measured as interlead variability of QT interval reflects the spatial inhomogeneity of ventricular repolarization times, and increased QTd may provide a substrate for malignant ventricular arrhythmias. Ischemia is associated with regional abnormalities of conduction and repolarization.

HYPOTHESIS

This study aimed to investigate the effect of acute ischemia on QTd during successful percutaneous transluminal coronary angioplasty (PTCA).

METHODS

Forty-three patients (10 women, 33 men, mean age 56 years) were enrolled in the study. Electrocardiogram (ECG) recordings were taken before PTCA and during balloon inflation period. QT maximum (QTmax), QT minimum (QTmin), and QTd (QTmax-QTmin) values were calculated from the surface ECG.

RESULTS

There was no difference among QTmax values (p = 0.6). Mean QTmin during balloon inflation was lower than before PTCA (368 +/- 45 vs. 380 +/- 41 ms, p = 0.002). The difference between QTd values before and during balloon inflation was statistically important (65 +/- 9 vs. 76 +/- 10 ms, p = 0.001). This difference is caused by a decrease in QTmin during balloon inflation.

CONCLUSION

Acute reversible myocardial ischemia induced by balloon inflation causes an increase in QTd value, and this increment is the result of a decrease in QTmin interval. Therefore, QTd may be a marker of reversible myocardial ischemia.

Association between the corrected QT intervals and combined intimal-medial thickness of the carotid artery in patients with type 2 diabetes

The main purpose of this study was to determine whether cardiac autonomic neuropathy or coronary atherosclerosis is the more important factor affecting prolongation of the corrected QT interval (QTc) in patients with type 2 diabetes. We studied the association between QTc and the coefficient of variance of the heart rate variation (CV(RR)), which reflects cardiac autonomic neuropathy, and the combined intimal-medial thickness (IMT) of the common carotid artery, which reflects coronary atherosclerosis. In addition, we also investigated the relationship between the QTc and blood pressure, serum lipid concentrations, hemoglobin A(1C) (HbA(1C)) concentration, and duration of diabetes. We studied 75 patients with type 2 diabetes and 30 age-matched healthy individuals. The QT interval was measured in lead II of the electrocardiogram (ECG) and was corrected using Bazett's formula. Cardiac neuropathy was assessed by measuring CV(RR). Atherosclerosis was evaluated by measuring the combined IMT of the common carotid artery using B-mode ultrasonography. The QTc in patients with type 2 diabetes was significantly longer than in healthy individuals (P <.0001). The QTc more closely correlated with the IMT of the carotid artery (r = 0.7206, P <.0001), compared with CV(RR) (r = -0.3188, P =.0053), although both were statistically significant. The QTc also correlated positively with the systolic (SBP) and diastolic blood pressure (DBP) (r = 0.4371, P <.0001, r = 0.3632, P =.0014, respectively). Based on stepwise regression analysis with the QTc interval as the dependent variable, the IMT of the carotid artery had the most significant association with the QTc (beta = 0.6882, P =.0004). In conclusion, QTc prolongation in the setting of diabetes might be caused primarily by coronary atherosclerosis rather than by cardiac autonomic neuropathy.

Mechanisms of ventricular fibrillation during coronary angioplasty: increased incidence for the small orifice caliber of the right coronary artery

BACKGROUND

Ventricular fibrillation (VF) is not an infrequent complication of percutaneous transluminal coronary angioplasty (PTCA). However, it is not clear why there is a marked discrepancy in the higher incidence of VF during right coronary artery (RCA) approach.

METHODS AND RESULTS

We analyzed in detail every case of VF occurring in 905 consecutive PTCA procedures to investigate possible mechanisms. Sixteen patients (M/F=15/1, mean age: 71 +/- 8 years) with VF during PTCA for the RCA as Group I. Those 51 patients (M/F=48/3, mean age: 70 +/- 9 years) without VF during PTCA for the RCA engagement were designated as Group II. Patients were equipped with cardiac event recorder (CardioCall, Reynolds Medical, UK) before the PTCA, and we set the time period 1 min before and after the event. The lead II was selected to check the QRS width, QTc interval, ST segment change and RR interval before and after event. A total of 905 PTCA procedures were included. There were 561 procedures for the left coronary artery and three events (0.5%) with spontaneous VF. However, there were 16 events (4.6%) of VF during 344 PTCA procedures for the right coronary artery. The incidence of VF for the right side PTCA was significantly higher than for the left side. The orifice of RCA in Group I was smaller than Group II (orifice of RCA in Group I vs. Group II - 2.7+/-0.8 vs. 4.1+/-1.2 mm, P<0.001). Most cases (68.7%) presented with ST segment depression before the onset of VF.

CONCLUSION

A small caliber of RCA and associated ST segment changes played important roles in the patients with VF during the PTCA.

Use of intracoronary electrocardiography for detecting ST-T, QTc, and U wave changes during coronary balloon angioplasty

Intracoronary electrocardiography (IC-ECG) is a more sensitive method than surface ECG to detect electrical changes during percutaneous transluminal coronary angioplasty (PTCA). It also provides direct monitoring of ST-T segment, QTc intervals, and U-wave genesis during balloon inflation. These changes are reflective of myocardial ischemia. The authors studied the effect of transient myocardial ischemia on ST-T segment, QTc intervals, and U-wave appearance by comparing standard and perfusion balloon angioplasty. PTCA of left anterior descending artery was performed in 14 patients using the standard balloons and in 11 patients using the perfusion balloons. Patients with perfusion balloon angioplasty had less ST-T elevation (0.15 +/- 0.05 mV versus 1.04 +/- 0.19 mV, P < 0.001), less QTc-shortening intervals (0.01 +/- 0.02 seconds versus -0.05 +/- 0.04 seconds, P < 0.001), and less positive U waves (two versus nine). The authors concluded that balloon angioplasty with perfusion balloons is associated with less ischemia as reflected by ST-T, QTc-shortening intervals, and U-wave changes. There was more positive U-wave appearance with the standard balloon angioplasty, which implies more ischemia. In addition, QTc-shortening intervals are associated with the development of U waves during standard balloon angioplasty. These findings suggest that IC-ECG is a sensitive tool in detecting myocardial ischemia. IC-ECG may also help to clarify the nature of chest pain during PTCA in some patients. Like QT dispersion (QTd), QTc-shortening intervals and new U waves can have prognostic implications and additional studies are needed to define this role.

Changes in ventricular repolarization during percutaneous transluminal coronary angioplasty in humans assessed by QT interval, QT dispersion and T vector loop morphology

OBJECTIVES

Based on clinical, epidemiological, and experimental data, transient cardiac ischaemia is one of the major triggering factors of malignant ventricular arrhythmia. According to animal studies, increased dispersion of repolarization is of pathophysiological relevance in this context. Therefore we explored the impact of myocardial ischaemia during single vessel coronary angioplasty on the change in ventricular repolarization, measured by QT and JT intervals and their dispersion in the 12-lead electrocardiogram. We also assessed a novel method, the 3-dimensional T vector loop, to find out whether it was sensitive to changes in ventricular repolarization during ischaemia, and whether there was any correlation with changes in the dispersion of the QT and/or JT intervals.

DESIGN

This study was prospective with consecutive patients. Only patients in sinus rhythm and without bundle branch block were included.

SETTING

All coronary angioplasties were performed at Norrlands University Hospital, Umeå. The analysis of the material was performed at the Karolinska Hospital, Stockholm.

SUBJECTS

Twenty-nine consecutive patients went through 30 elective one-vessel percutaneous transluminal coronary angioplasty (PTCA) procedures. PTCA was performed in 10 stenoses of the left anterior descending, 10 of the left circumflex, and 10 of the right coronary artery.

INTERVENTIONS

A 12-lead electrocardiogram was recorded continuously as part of routine monitoring of the patient during PTCA and the T vector loop was calculated from the simultaneously recorded. X, Y, Z leads.

MAIN OUTCOME MEASURES

Repolarization was assessed by the QRS, QT and JT intervals as well as by the T vector loop parameters (Tarea, Tavplan, and Teigenv) before and at the end of the first occlusion during PTCA.

RESULTS

PTCA, with an average occlusion time of 171 +/- 60 s (mean +/- SD), induced ischaemia on the 12-lead electrocardiogram in 73% of cases. The overall response for the 30 procedures was a significantly increased dispersion of ventricular repolarization, both corrected and uncorrected for heart rate. QT dispersion increased by, on average, 19% from 74 +/- 35 to 88 +/- 36 ms, QTc dispersion by 27% from 71 +/- 39 to 90 +/- 42 ms, and JTc dispersion by 19% from 78 +/- 32 to 94 +/- 43 ms (P < 0.05). The T vector loop became more circular and bulgy during occlusion (all three parameters changed by between 33% and 59%). There was a significant correlation between changes in one of the T vector loop parameters (Teigenv), and changes in JT and QT dispersion in the left anterior descending group.

CONCLUSIONS

Transient ischaemia during PTCA induced significant changes in ventricular repolarization, especially during occlusion of the left anterior descending artery and resulted in a significant increase in both QT and QTc dispersion. The degree of QT dispersion was such that several patients were at risk of ventricular arrhythmia, if a proper triggering extrasystole had occurred. In addition, and as an original observation, the 3-dimensional T vector loop morphology seemed even more sensitive to coronary occlusion than QT dispersion.

Usefulness of endocoronary electrocardiogram in the detection of myocardial viability and comparison with single-photon emission computed tomography Tl-201

In 20 patients who had recently had an acute myocardial infarction, we compared endocoronary electrocardiographic modifications recorded during angioplasty with thallium-201 for the detection of myocardial viability. Our data demonstrate that endocoronary electrocardiography can be an easy and reliable tool to assess viability, with sensitivity, specificity, and positive and negative predictive values of 100%, 80%, 94%, 100%, respectively.

Effect of coronary angioplasty on QT dispersion

Increased QT dispersion (QTmax-QTmin [QTd]) reflects inhomogeneous ventricular repolarization that may provide a substrate for serious arrhythmias and is associated with adverse clinical outcomes in patients with heart disease. Effective treatment of acute myocardial infarction or ventricular arrhythmias may reduce QTd, but the effect of coronary revascularization on QTd in patients without these conditions is unknown. In this study, QTd was measured before and 4 and 24 hours after successful angioplasty in 94 patients without ongoing symptomatic myocardial ischemia or malignant arrhythmias. QTd decreased from 434 +/- 17 msec before angioplasty to 354 +/- 15 msec 4 hours (p < 0.05) and 33 +/- 14 msec 24 hours after angioplasty (p < 0.05). QTd was improved in 64% of patients, worse in 28%, and unchanged in 8%. Thus angioplasty significantly improves QTd. This may reflect increased myocardial perfusion and may be inherently beneficial by reducing the propensity for arrhythmias.