Detection of Exercise‐Induced Myocardial Ischemia by Multichannel Magnetocardiography in Single Vessel Coronary Artery Disease

Background: Detection of myocardial ischemia was studied with multichannel exercise magneto‐cardiography (MCG). A surface gradient method was applied to analyze cardiac magnetic fields. Methods: We studied 27 patients with single vessel coronary artery disease (CAD) and 17 healthy volunteers. The MCG was recorded over anterior chest during supine bicycle ergometry. The two‐dimensional direction of the maximum spatial magnetic field gradient was determined during the ST segment and at the T‐wave apex at different phases of stress test. Results: The CAD patient group was separated from controls by the orientation of the magnetic field gradient during the ST segment at cessation of exercise (CAD 167 ± 68° vs controls 106 ± 49°; P < 0.005) and at 4 minutes postexercise, but not at rest. The‐CAD patient group was separated from controls also by the orientation of the magnetic field gradient at the T‐wave apex at 4 minutes postexercise (CAD 87 ± 60° vs controls 58 ± 18° P < 0.05), but not at rest. The change in the orientation of the field gradient at the T‐wave apex 4 minutes postexercise, compared to baseline, was greater in CAD patients (31 ± 43°) than in controls (9 ± 8° P < 0.05). This change was larger in the patient group with stenosis in the right than in the left coronary artery (P < 0.05). Conclusions: Transient acute myocardial ischemia causes well‐recognizable changes in the magnetocardiogram at the ST segment and the T wave. The orientation of the maximum spatial gradient of the magnetic field can be used as a parameter to determine these changes.     

Value of the Corrected QT Interval Dispersion Obtained Exercise Electrocardiography in Determining Remote Vessel Disease in Patients with Healed Q‐Wave Myocardial Infarction

Background: QT and corrected QT dispersion (QTD, QTcD) obtained by using the standard 12‐lead ECG is a marker of nonhomogenous ventricular repolarization. QTD obtained from exercise ECG increases the diagnostic reliability of ST‐segment changes. The aim of this study was to investigate the diagnostic accuracy of the QTD and QTcD obtained by a 12‐lead ECG during the peak exercise in determining remote vessel disease in patients with healed Q‐wave MI. Methods: Eighty patients with healed Q‐wave Ml (mean age 54 ± 8 years; 71 men, 9 women; 29 anterior; 51 inferior Ml) who underwent exercise stress testing and coronary angiography were included in this study. Patients were divided into two groups, with (group I) and without (group II) remote vessel coronary artery disease. During peak exercise, sensitivity, specificity, negative and positive predictive value of the ST‐segment depression, and QTcD were compared between both groups. Moreover, the resting and peak exercise ECG parameters were compared between group I and group II. Results: In coronary angiography, remote vessel disease was detected in 48 patients (group I). In determining remote vessel disease, the sensitivity, specificity, and the negative and positive predictive values of the peak exercise QTcD ≧ 70 ms were significantly higher than those of the peak exercise ST‐segment depression (81%, 63%, 69%, and 76% vs 71%, 53%, 55%, and 69%, respectively; P < 0.01 for all comparisons). In group I, QTD and QTcD were significantly higher in patients with anterior wall Ml than those with inferior wall Ml both during the resting and peak exercise ECG. In group II, the resting QTD and QTcD were significantly higher in patients with anterior wall MI than those with inferior wall MI. In patients with anterior wall MI and inferior wall Ml, QTD and QTcD significantly increased with exercise in group I. Conclusion: In patients with healed Q‐wave Ml, the value of QTcD ≧ 70 ms increases the diagnostic: accuracy of the exercise stress testing in determining remote vessel disease. A.N.E. 2002;7(3):228–233     

Temporal Analysis of the Depolarization Wave of Healed Myocardial Infarction in Body Surface Potential Mapping

Background: We studied the ability of different time segments of the depolarization wave recorded with body surface potential mapping (BSPM) to detect and localize myocardial infarction (MI). Methods: BSPM was recorded in 24 patients with remote MI and in 24 healthy controls. Cine and contrast‐enhanced magnetic resonance imaging (MRI) was used as a reference method. Patients were grouped according to anatomical location of their MI. The QRS complex was divided into six temporally equal segments, for which time integrals were calculated. Results: The time segments of the QRS complex showed different MI detection capability depending on MI location. For anterior infarction the second segment of the QRS complex was the best in MI detection and the optimal area was on the right inferior quadrant of the thorax (time integral average ?1.5 ± 1.8 mVms patients, 1.0 ± 1.6 mVms controls, P = 0.002). For lateral infarction the first segment of the QRS complex performed best and the optimal area for MI detection was the left fourth intercostal area (time integral average 1.8 ± 1.0 mVms patients, 0.7 ± 0.5 mVms controls, P = 0.024). For inferior and posterior MI the mid‐phases of the QRS complex were the best and the optimal area was the mid‐inferior area of the thorax (time integral average ?6.2 ± 8.3 mVms patients, 3.3 ± 4.3 mVms controls, P = 0.002; ?9.1 ± 6.1 mVms patients, 0.6 ± 7.1 mVms controls, P = 0.001, respectively). Conclusions: Time segment analysis of the depolarization wave offers potential for improving the detection and localization of healed MI.     

Electrocardiographic signs of remote myocardial infarction

Twelve-lead electrocardiogram is an integral part of the evaluation of an acute and a remote myocardial infarction (MI). Electrocardiographic signs of an acute ST-elevation MI are more precise than those of an acute non-ST-elevation MI. Recognition of a remote MI is more difficult because once the repolarization abnormalities (ST-segment and T-wave changes) stabilize after an acute MI resolves, then the Q wave remains as the only universally recognized sign of MI. In addition, there is no specific sign of a non-Q-wave MI or a non-ST-elevation MI, or in fact of an ST-elevation MI that did not result in Q waves. The fragmented QRS (fQRS) is another recently described sign of a remote MI. It is defined by the presence of an additional R wave (R') or notching in the nadir of the S wave, or the presence of >1 R' (fragmentation) in 2 contiguous leads corresponding to a major coronary artery territory. The specificity of fQRS is inferior to that of a Q wave for an MI scar (89% vs 99%). However, fQRS has a superior sensitivity and a negative predictive value compared with a Q wave. In addition, there is an incremental gain in the sensitivity up to 91.4% when these 2 signs (fQRS and Q wave) are combined. The repolarization abnormalities of MI may also persist indefinitely as a sign of a remote MI in few patients. These abnormalities include persistent ST elevation, ST depression, nonspecific ST-T wave changes, and T-wave inversion.     

Changes occurring in the postinfarction ECG in relation to age, sex, and previous myocardial infarction

Minnesota codes (MC), expressing Q-QS, ST segment, and T wave abnormalities in ECGs taken during the acute event and at a 1-year follow-up were studied in 256 survivors of myocardial infarction (MI). On the 1-year ECGs large Q waves (MC 1.1) were more common in patients with a history of previous MI than in those with a first MI. Regression of Q-QS, ST segment, and T wave changes occurred more extensively in first MIs, whereas progression of MC Q-QS and ST segment signs tended to be common in those with recurrent MI. On the acute ECGs large Q waves were more frequent in men (52%) than in women (36%), but ST segment depression of 1 mm or more (MC 4.1) was predominant in women in both the acute and 1-year ECGs. This ECG sign was related to the advanced age of the patients. There was no significant sex difference in the regression of the Q-QS signs, but the disappearance of ST and T wave changes occurred more extensively in men. The ECG returned to normal in 12% of men with a first MI but only infrequently in women and men with recurrent MI.     

Modulation of ventricular repolarization in patients with transient left ventricular apical ballooning: a case control study

Objective: Even though diffuse T wave inversion and prolongation of the QT interval in the surface electrocardiogram (ECG) have been consistently reported in patients with transient stress‐induced left ventricular apical ballooning (AB), ventricular repolarization has not yet been systematically investigated in this clinical entity. Background: AB, an emerging syndrome that mimics acute ST‐segment elevation myocardial infarction (MI), is characterized by reversible left ventricular wall motion abnormalities in the absence of obstructive coronary heart disease and significant QT interval prolongation. Methods: We prospectively enrolled 22 consecutive patients (21 women, median age 65 years) with transient left ventricular AB. A total of 22 age‐, gender‐, body‐mass‐index‐, and left‐ventricular‐function‐matched patients with acute anterior ST‐segment elevation MI undergoing successful direct percutaneous coronary intervention for a proximal occlusion of the LAD, as well as 22 healthy volunteers served as control groups. Beat‐to‐beat QT interval and QT interval dynamicity were determined from 24‐hour Holter ECGs, recorded on the third day after hospital admission. Results: There were no significant differences in baseline clinical characteristics, except higher peak enzyme release in MI patients. Compared with MI patients, AB patients exhibited significantly prolonged mean QT intervals and rate‐corrected QT intervals (QT: 418 ± 37 vs 384 ± 33 msec, P < 0.01; QTc_Bazett: 446 ± 40 vs 424 ± 35 msec, P < 0.05; QTc_Fridericia: 437 ± 35 vs 412 ± 31 msec, P < 0.05). Mean RR intervals tended to be higher in AB patients, without reaching statistical significance (877 ± 96 vs 831 ± 102 msec, P = NS). The linear regression slope of QT intervals plotted against RR intervals was significantly flatter in AB patients at both day‐ and nighttime (QT/RR slope_day: 0.18 ± 0.04 vs 0.22 ± 0.06, P < 0.01; QT/RR slope_night: 0.12 ± 0.03 vs 0.17 ± 0.05, P < 0.01). Conclusion: The present study is the first to demonstrate significant differences of QT interval modulation in patients with transient left ventricular AB and acute ST‐segment elevation MI. Even though transient AB is associated with a significant QT interval prolongation, rate adaptation of ventricular repolarization (i.e., QT dynamicity) is not significantly altered, suggesting a differential effect of autonomic nervous activity on the ventricular myocardium in transient AB and in acute MI.     

Diagnostic Value of Exercise‐Induced ST‐Segment Elevation in Q‐Wave Leads. After Recent Myocardial Infarction

Background: Exercise‐induced ST‐segment elevation in an infarct territory with abnormal Q waves is a known marker for more severe left ventricular wall‐motion abnormalities. However, it is reported, that exercise‐induced ST‐segment elevation in infarct leads may indicate residual viability in the intarctregion. The aim of the study was to test whether exercise‐induced ST‐segment elevation is related to left ventricular (LV) dysfunction or to persistent viability in patients with previous myocardial infarction (MI). Methods: 145 consecutive patients (119 men, 26 women, age 58 ± 11 years) 2–3 weeks after Q‐wave Ml but without ST elevation at rest ECG were enrolled in the study. All patients underwent a target heart rate or symptom‐limited exercise testing (ET) with Bruce protocol. Exercise‐induced ST‐segment elevation < 1 mm above the baseline ST segment level (80 ms after J point) in more than 1 ECG lead with Q wave was considered to be significant. Patients were divided in two groups according to ET results: group I, 25 patients with significant exercise‐induced ST‐segment elevation and group II, 120 patients without exercise‐induced ST‐segment elevation. All patients underwent rest ECHO and low dose dobutamine stress echo (LOSE) within 7 days after ET. LV function was estimated using ejection fraction (EF). Results: More severe LV dysfunction was observed in patients from group 1 (EF 31 ± 8.16% vs EF 45 ± 10.3%). Myocardial viability (defined as an improvement of regional systolic wall thickening in the regions with resting regional wall‐motion abnormalities during LOSE 5 to 15 g/kg/min was recognized in 8 patients (32%) in group I and 31 patients (25.8%) in group II. There was no relation between exercise‐induced ST‐segment elevation and myocardial viability (chi‐square test: 2,809; NS). Conclusions: Exercise‐induced ST‐segment elevation in most cases is associated with left ventricular dysfunction. Patients with exercise‐induced ST‐segment elevation have a lower EF than those without and greater severity of resting wall‐motion abnormalities. Our results suggest that exercise‐induced ST‐segment elevation is not related to residual myocardial viability.     

ST segment shifts are poor predictors of subsequent Q wave evolution in acute myocardial infarction. A natural history study of early non-Q wave infarction

Acute ST segment elevation is regarded generally as the sine qua non of evolving Q wave myocardial infarction (MI) because such electrocardiographic (ECG) injury is believed to be a marker of transmural ischemia and a forerunner of transmural necrosis. Alternatively, ST segment depression with or without T wave inversion is viewed as the dominant ECG feature of non-Q wave MI. However, this hypothesis has not been assessed prospectively in an acute MI population. We analyzed 2,304 serial ECGs at study entry (admission), day 2, day 3, and predischarge (mean, 10.2 +/- 2 days) from 576 patients with creatine kinase MB confirmed acute non-Q wave MI to determine what percentage of patients with early ST segment elevation culminated in subsequent Q wave development. Of this group, 187 patients (32%) exhibited 1 mm or greater ST segment elevation in two or more contiguous entry ECG leads. Of those patients whose non-Q wave MI could be localized on the basis of diagnostic admission ST segment shifts, the prevalence of early ST segment elevation was 43% (187 of 439). The sum total mean (+/- SD) peak ST segment elevation by lead group (anterior, inferior, lateral) was 4.0 +/- 2.4, 4.5 +/- 2.4, and 2.5 +/- 0.6 mm, respectively. Despite this, only 20% of patients with ST segment elevation (37 of 187) developed Q waves. Of 252 patients who exhibited early ST segment depression or T wave inversion or both, 39 (15%) evolved subsequent Q waves. Thus, while the prevalence of early ST segment elevation in acute evolving non-Q wave MI was higher than previously reported, 80% of patients with and 85% of patients without ST segment elevation and absent Q waves on the admission ECG did not develop subsequent Q waves during a 2-week period of observation (p = NS). In addition, when patients with ST segment elevation were compared with patients with ST segment depression or T wave inversions or both, there were no between-group differences in log peak creatine kinase (404 vs. 383 IU), reinfarction (6% vs. 8%), postinfarction angina (50% vs. 42%), or early recurrent ischemia (49% vs. 45%), defined as postinfarction angina with transient ECG changes. Thus, in patients who present with initial acute non-Q wave MI, ST segment shifts on admission are unreliable predictors of subsequent Q wave evolution and do not discriminate significant differences in postinfarction outcome. In particular, ST segment elevation during the early hours of evolving infarction is not an invariable harbinger of subsequent Q wave development.     

T‐Wave Abnormalities Are a Better Predictor of Cardiovascular Mortality than ST Depression on the Resting Electrocardiogram

Background: ST depression and T‐wave amplitude abnormalities are known to be independent predictors of cardiovascular (CV) death, but a direct comparison between them has not been described. Methods: Analyses were performed on the first electrocardiogram (ECG) digitally recorded on 46,950 consecutive patients at the Palo Alto Veterans Affairs Medical Center since 1987. Females and patients with electrocardiograms exhibiting bundle branch block, left ventricular hypertrophy, electronic pacing, diagnostic Q waves, or Wolff–Parkinson–White syndrome were excluded, leaving 31,074 male patients for analysis (mean age 55 ± 14). There were 1878 (6.0%) cardiovascular deaths (mean follow‐up of 6 ± 4 years). Electrocardiograms were classified using Minnesota code according to the degree of ST depression and T‐wave abnormality, and the nine possible combinations of ST segment and T‐wave abnormalities were recoded for analysis. Results: The combination of major abnormalities in ST segments and T‐waves carried the greatest hazard [3.2 (CI 2.7–3.8)]. Minor ST depression combined with more severe T‐wave abnormalities carried a hazard of 3.1 (CI 2.5–3.7), whereas minor T‐wave abnormalities combined with more severe ST depression carried a hazard of only 1.9 (CI 1.6–2.3). Conclusion: While both ST segment depression and abnormal T‐wave amplitude are clinically important, T‐wave abnormalities appear to be greater predictors of cardiovascular mortality.     

Menstrual Cycle and ST Height

Background: Sex hormones and menstrual cycle effects on ST height have not yet been clearly identified. Methods: Twenty‐two young, healthy women (aged 22–32 years) were included in this study. Twelve‐lead ECGs were registered during menses, follicular and luteal phase of the menstrual cycle at baseline, and after double autonomic blockade (DAB). Chest leads V2–V4 and limb leads I and II were chosen for analysis. ST height was measured manually at J‐Point and 40 ms after the J‐Point, and values were corrected for QRS amplitude (J‐Point/QRS, 40 ms/QRS). Repeated measure ANOVA was used to analyze differences in ST height among the three phases of the menstrual cycle. A P‐value < 0.05 was considered as significant. Results: At baseline, ST height, QTc, and T wave amplitude were not significantly different among the three phases of the menstrual cycle. After double autonomic blockade, ST height at 40 ms, J‐Point/QRS, and 40 ms/QRS was significantly higher during follicular versus luteal phase (0.152 ± 0.413 mm versus ?0.007 ± 0.427 mm, P = 0.0059 at 40 ms; ?0.001 ± 0.030 versus ?0.015 ± 0.032, P = 0.0039 at J‐Point/QRS; 0.013 ± 0.031 versus ?0.004 ± 0.032, P = 0.0005 at 40 ms/QRS) as was the QTc. ST height differences at J‐Point were not significantly different (?0.046 ± 0.395 mm follicular, ?0.167 ± 0.448 mm luteal, and ?0.083 ± 0.492 mm menses, P = 0.1014). Conclusion: ST height and QTc varied among the three phases of the menstrual cycle, predominantly after double autonomic blockade. Female sex hormones that vary throughout the menstrual cycle may modulate measures of repolarization.     

The Predictive Value of Exercise QRS Duration Changes for Post‐PTCA Coronary Events

Background: The sensitivity and predictive values of exercise ECG testing using ST‐T criteria after percutaneous transluminal coronary angioplasty (PTCA) are low, precluding its routine use for screening for restenosis. The predictive value of QRS duration criteria during exercise testing (ET) ECG after PTCA for future coronary events has not been reported. The aim of the study was to compare QRS duration changes with ST‐T criteria during ET, as a predictor of coronary events after PTCA. Methods: A prospective study of 206 consecutive patients who underwent ET at a mean of 34 ± 14 days after their first PTCA, and were the followed for a mean of 23 ± 9 months. Patients were divided by QRS duration into two groups—Q1: ischemic response (QRS duration prolongation of more than 3 ms relative to the resting duration), and Q2: normal response (QRS duration shortening or without change from resting duration). Patients were also divided by their ST‐T response, S1: ischemic response, and S2: normal response. Results: During follow‐up 52 patients (58%) experienced restenosis or MI, or underwent CABG—Q1: 44 (85%), Q2: 8(15%) (P < 0.0002), S1: 8 (15%), S2: 44 (85%), (P < 0.641) , two patients died—Q1: 1 (1%) and Q2: 1 (1%). For QRS and ST‐T, the relative risk of having at least one of the coronary events was 4.02 (CI 2.1–9.9) versus 1.13 (CI 0.8–2.9), respectively. The sensitivity for future coronary events was 85% and 52% and the specificity was 48% and 98% for the QRS and ST‐T criteria, respectively. Conclusion: QRS prolongation during peak ET ECG after PTCA is a more sensitive marker than ST‐T criteria for detection of patients at risk for later coronary events.     

Relationship between QRS duration and repolarization abnormalities in patients with wolff-parkinson-white syndrome

Marked T wave abnormalities in 12-lead electrocardiograms often appear after radiofrequency ablation in patients with Wolff-Parkinson-White (WPW) syndrome. Durations of the QRS complex before ablation have been reported to be significantly greater in patients with repolarization abnormalities after ablation than in those with normal repolarization. However, there has been no report concerning the relationship between QRS duration and repolarization abnormalities before ablation. It has been reported that QRST isointegral maps are dependent on local cellular repolarization properties but largely independent of activation sequence, and that they provide quantitative information about repolarization abnormalities. Isointegral maps were constructed from data recorded in 34 patients with WPW syndrome and QRS durations of 0.1 second or longer (21 patients with left-sided accessory pathways and 13 with right-sided pathways) in order to investigate the relationship between QRS duration and abnormalities in repolarization properties during preexcitation. Body surface ECGs were recorded with an 87-lead system at a sampling interval of 1 ms. The QRST values (mean ± 2SD) from 607 normal individuals were taken to represent the normal range. The area with abnormally low QRST values was designated as the −2SD area and the sum of the QRST values (ΣQRST) in this area was calculated. The QRS duration was found to be significantly related to ΣQRST. These results demonstrate that the patients with WPW syndrome had abnormalities in local repolarization properties that were significantly related to QRS duration during preexcitation. The degree of preexcitation may be important in producing these abnormalities in patients with manifest WPW syndrome. This may result in T wave abnormalities after ablation of the accessory pathway attributable to cardiac memory.     

阵发性室上性心动过速时ST－T改变的临床意义

回顾性分析经射频消融治疗的４１８例阵发性室上性心动过速（ＰＳＶＴ）发作时的体表１２导联心电图，以了解ＳＴ－Ｔ改变的临床意义。结果表明３０５例房室折返性心动过速（ＡＶＲＴ）中，ＳＴ段下移≥２ｍｍ且持续≥８０ｍｓ和（或）Ｔ波倒置者有１８１例（５９．３４％），明显高于房室结折返性心动过速（ＡＶＮＲＴ）患者（２８／１１３，２４．７８％）Ｐ＜０．００５。并且此差异不能被心率所矫正。此外左游离壁旁道患者ＳＴ段压低多分布在Ｖ３～Ｖ６导联，而右后和左后隔旁道患者倒置的Ｔ波和（或）ＳＴ段压低多发生于Ｉ、ＩＩ、ａＶＦ导联。提示ＰＳＶＴ时心电图上ＳＴ－Ｔ改变可作为区分ＡＶＲＴ和ＡＶＮＲＴ的一个有用指标，并且可能还有粗略的旁道定位价值     

The role of baseline and post‐procedural frontal plane QRS‐T angles for cardiac risk assessment in patients with acute STEMI

Background

To our knowledge, no study so far investigated the importance of post‐procedural frontal QRS‐T angle f(QRS‐T) in ST segment elevation myocardial infarction (STEMI). The aim of our study was to investigate the role of baseline and post‐procedural f(QRS‐T) angles for determining high risk STEMI patients, and the success of reperfusion.

Methods

A total of 248 patients with first acute STEMI that underwent primary percutaneous coronary intervention (pPCI) or thrombolytic therapy (TT) between 2013 and 2014 were included in this study. Baseline f(QRS‐T) angle was defined as the angle which measured from the first ECG at the time of hospital admission. Post‐procedural (QRS‐T) angle was defined according to the treatment strategy as follows: the angle which measured from the post‐PCI ECG in patients treated with pPCI; the angle which measured from the ECG taken 90 min after onset of therapy in patients treated with TT.

Results

The baseline (101.9° ± 48.0 vs. 72.1° ± 49.1, p = 0.014) and post‐procedural f(QRS‐T) angles (95.7° ± 48.1 vs. 58.1° ± 47.1, p = 0.002) were significantly higher in patients who developed in‐hospital mortality than the patients who did not develop in‐hospital mortality. Also, f(QRS‐T) angle measured at 90 min was significantly lower in patients with successful thrombolysis group compared to failed thrombolysis group (53.2° ± 42.8 vs. 77.3° ± 52.9, p = 0.033), whereas baseline f(QRS‐T) angle was similar between two groups (78.6° ± 53.4 vs. 78.9° ± 54.0, p = 0.976). Multivariate analysis showed that post‐procedural f(QRS‐T) angle ≥89.6° (odds ratio: 3.541, 95% confidence interval: 1.235–10.154, p = 0.019), but not baseline f(QRS‐T) angle, was independent predictor of in‐hospital mortality.

Conclusion

f(QRS‐T) angle may be used as a beneficial tool for determining high risk patients in acute STEMI. Unlike previous studies, we showed for the first time that that post‐procedural f(QRS‐T) can predict in‐hospital mortality and TT failure.

     

Detection of Multivessel Disease Post Myocardial Infarction Using an Exercise‐Induced QRS Score

Objective: The aim of this study was to investigate the ability of Athens QRS score values to detect stenoses in other coronary arteries than the obstructed ones (which caused the myocardial infarction [MI]) in patients with a history of MI. Methods: We studied 125 patients (93 males and 32 females, mean age 54 ± 7 years [range 45–68 years]) with a history of MI (46 patients with anterior MI, 54 patients with inferior MI, 25 patients with lateral MI). All patients underwent treadmill exercise testing and coronary arteriography. Results: Athens QRS score values were inversely related to the extent of CAD: ?0.5 ± 0.3 mm for patients with 1‐VD (obstructed vessel), ?3.4 ± 2.2 mm for patients with 2‐VD (obstructed vessel and stenosis in another vessel), and ?5 ± 1.8 mm for patients with 3‐VD (obstructed vessel and stenoses in two more vessels). The ROC curves for the detection of multivessel disease showed that the area under the curve for QRS score values < ?3 mm is significantly higher than the curve for ST‐segment depression ≥1 mm (0.948 vs 0.792, P < 0.001). Conclusions: Values of the Athens QRS score less than ?3 may distinguish single‐ from multivessel coronary artery disease in patients with a history of MI.     

Myocardial infarction in thrombotic thrombocytopenic purpura: a single-center experience and literature review

Background: Several case reports and series have described myocardial infarctions (MIs) in patients hospitalized for thrombotic thrombocytopenic purpura (TTP). The exact magnitude and outcome of this complication are unknown. Methods: Electronic medical records for patients admitted to Wake Forest University Baptist Medical Center were examined from 1996 to 2005. Those patients having a diagnosis of TTP during the hospitalization period were included in the analysis. Only patients’ initial episodes of TTP were analyzed. Baseline cardiac and TTP risk factors were documented. Outcomes analyzed included MIs, arrhythmias, development of congestive heart failure and death. Results: Eighty‐five patients diagnosed with TTP were identified with 13 (15.3%) having MIs, as defined by an elevation of cardiac enzymes. Median troponin I value was 5.9 ng/mL (range 3.7–8.8 ng/mL). Twelve patients had non‐ST segment elevation MIs and one had ST segment elevation. Two of 13 patients who had echocardiographic analysis had documented wall motion abnormalities. There was no difference between non‐MI and MI patients in cardiac risk factors, prior cardiac events, history of thromboembolic disease or heart failure. There was no in‐hospital mortality difference. Conclusion: MI is an important complication of TTP, identified in 15.3% of patients in our study. Routine cardiovascular evaluation with cardiac enzymes, electrocardiography, and telemetry is warranted in acute TTP patients. Appropriate intervention is yet to be determined.     

Reproducibility of HTS-SQUID magnetocardiography in an unshielded clinical environment.

A new technology has been developed which measures the magnetic field of the human heart (magnetocardiogram, MCG) by using high temperature superconducting (HTS) sensors. These sensors can be operated at the temperature of liquid nitrogen without electromagnetic shielding. We tested the reproducibility of HTS-MCG measurements in healthy volunteers. Unshielded HTS-MCG measurements were performed in 18 healthy volunteers in left precordial position in two separate sessions in a clinical environment. The heart cycles of 10 min were averaged, smoothed, the baselines were adjusted, and the data were standardized to the respective areas under the curves (AUC) of the absolute values of the QRST amplitudes. The QRS complexes and the ST-T intervals were used to assess the reproducibility of the two measurements. Ratios (R(QRS), R(STT)) were calculated by dividing the AUC of the first measurement by the ones of the second measurement. The linear correlation coefficients (CORR(QRS), CORR(STT)) of the time intervals of the two measurements were calculated, too. The HTS-MCG signal was completely concealed by the high noise level in the raw data. The averaging and smoothing algorithms unmasked the QRS complex and the ST segment. A high reproducibility was found for the QRS complex (R(QRS)=1.2+/-0.3, CORR(QRS)=0.96+/-0.06). Similarly to the shape of the ECG it was characterized by three bends, the Q, R, and S waves. In the ST-T interval, the reproducibility was considerably lower (R(STT)=0.9+/-0.2, CORR(STT)=0.66+/-0.28). In contrast to the shape of the ECG, a baseline deflection after the T wave which may belong to U wave activity was found in a number of volunteers. HTS-MCG devices can be operated in a clinical environment without shielding. Whereas the reproducibility was found to be high for the depolarization interval, it was considerably lower for the ST segment and for the T wave. Therefore, before clinically applying HTS-MCG systems to the detection of repolarization abnormalities in acute coronary syndromes, further technical development of the systems is necessary to improve the signal-to-noise ratio.     

Magnetocardiographic studies of ventricular repolarization in old inferior myocardial infarction

Isomagnetic maps of 50 normal subjects (control group) and 23 patients with old inferior myocardial infarction (IMI group) were recorded in order to analyse T wave abnormalities in inferior myocardial infarction. The T wave of the magnetocardiogram (MCG) in the control group showed negative deflections in the left upper portion and positive deflections in the right lower portion, thus resulting in a T vector directed leftward and inferiorly. The T wave of the IMI group was flat or positive in the left upper portion and flat or negative in the right lower portion, suggesting a T vector directed superiorly. In addition, opposing dipoles were observed in 36.4% of the IMI group; i.e. one directed superiorly, presumably due to inferior myocardial ischaemia, and the other directed inferiorly due to normal repolarization. Localized T vector abnormalities could be detected by the MCG in some cases, in which coronary T waves of the standard electrocardiogram had returned to normal. Furthermore, multiple dipoles were more frequently observed in the isomagnetic map than in the isopotential map (5 vs. 15; P less than 0.01). These results suggest that the MCG is helpful in diagnosing myocardial ischaemia when this is not detectable on the electrocardiogram.     

ST-T改变在鉴别窄QRS波心动过速中的价值

为评价ST T改变在鉴别窄QRS波心动过速中的价值 ,用SPSS分析 12 4例窄QRS波心动过速患者体表 12导联心电图的ST T改变 ,其中房室折返性心动过速 (AVRT) 72例 ,房室结折返性心动过速 (AVNRT) 5 2例。结果 :AVRT组Ⅰ aVL导联ST段压低幅度 (0 .10± 0 .0 7mV)大于AVNRT组 (0 .0 6± 0 .0 6mV) ,P =0 .0 0 2 ;AVRT组V1导联T波幅度 (0 .14± 0 .19mV)大于AVNRT组 (0 .0 1± 0 .13mV) ,P <0 .0 0 1。鉴别窄QRS波心动过速的预测指标为QRS波终末改变 (R2 =0 .6 0 4 ,P <0 .0 0 1)、V1导联T波方向 (R2 =0 .2 4 9,P <0 .0 0 1)、V1导联T波幅度 (R2 =0 .180 ,P <0 .0 0 1)、Ⅰ aVL导联ST段压低 (R2 =0 .0 4 3,P <0 .0 0 1)。QRS波终末改变阳性预测AVNRT的特异性 98.6 % ,敏感性 75 .0 % ;V1导联T波正向预测AVRT的特异性 6 7.3% ,敏感性 81.9%。结论 :ST T改变有助于鉴别窄QRS波心动过速。QRS波终末改变是鉴别窄QRS波心动过速的较强预测指标 ;V1导联T波方向与幅度、Ⅰ aVL导联ST段压低是鉴别窄QRS波心动过速的较弱预测指标。     

Electrocardiographic T Wave Abnormalities and the Risk of Sudden Cardiac Death: The Finnish Perspective

The identification of patients at risk for sudden cardiac death (SCD) is still a significant challenge to clinicians and scientists. Noninvasive identification of high‐risk patients has been of great interest, and several ventricular depolarization and repolarization abnormalities in the standard 12‐lead electrocardiogram (ECG) have been associated with increased vulnerability to lethal ventricular arrhythmias. Several benign and pathological conditions can induce changes in repolarization detected as alteration of the ST segment or T wave. Changes in the ST segment and T waves can be early markers of an underlying cardiovascular disease, and even minor ST‐T abnormalities have predicted reduced survival and increased risk of SCD in the adult population. In this review, we will discuss the current knowledge of the SCD risk with standard 12‐lead ECG T wave abnormalities in the general population, and possible T wave changes in various cardiac conditions predisposing to SCD.