Detection of stress-induced myocardial ischemia from the depolarization phase of the cardiac cycle—a preliminary study

Background

Electrocardiogram (ECG)-based detection of ischemia is typically dependent on identifying changes in repolarization. Analysis of high-frequency QRS (HFQRS) components, related to the depolarization phase of the cardiac action potential, has been reported to better identify ischemia. Our aim was to test the hypothesis that HFQRS analysis is both more sensitive and specific than standard ECG for detecting exercise-induced ischemia in patients undergoing exercise myocardial perfusion imaging (MPI).

Methods

Exercise MPI was performed in 133 consecutive patients (age, 63 ± 12; 100 males) and used as the gold standard for ischemia. Patients with QRS duration more than 120 milliseconds (n = 20), technical problems (n = 8), or inconclusive MPI (n = 4) were excluded, leaving 101 patients for analysis. Conventional ECG was combined with high-resolution ECG acquisition that was digitized and analyzed using the HyperQ System (BSP, Tel Aviv, Israel). The relative HFQRS intensity change during exercise was used as an index of ischemia.

Results

Of the 101 patients who were included in the analysis, 19 exhibited MPI ischemia. The HFQRS index of ischemia was found to be more sensitive (79% vs 41%; P < .05) and more specific (71% vs 57%; P < .05) than conventional ST analysis.

Conclusions

The HFQRS analysis was more sensitive and specific than conventional ECG interpretation in detecting exercise-induced ischemia and exhibited enhanced diagnostic performance in both women and men. Thus, it may aid in the noninvasive diagnosis of ischemic heart disease.     

QRS Score: A Composite Index of Exercise‐Induced Changes in the Q,R, and S Waves During Exercise Stress Testing in Patients with Ischemic Heart Disease

Background: To detect ischemic heart disease, the exercise‐induced ST‐segment displacement is the most frequently used ECG parameter. However, the value of this marker was proven to be limited with varying sensitivity and specificity. A new parameter, called QRS score, emerged to improve the efficacy of exercise testing. Methods: Our study aimed at evaluating the diagnostic value of QRS score in ischemic heart disease, investigating males and females separately, and examining the effects of heart rate and antiischemic medication. QRS score and cumulative ST depression were calculated in 212 patients and correlated to the findings of the stress myocardial perfusion SPECT (197 subjects) or coronary angiography (54 subjects). Results: An inverse correlation could be found between the QRS score and the results of myocardial SPECT and coronary angiography in the whole population, especially in males; females did not show a significant relationship. In patients with conclusive tests (achieving 85% of the maximal predicted heart rate) QRS score correlated significantly with the results of the stress myocardial perfusion SPECT and coronary angiography. The sensitivity, specificity, and validity of the QRS score surpassed those of the cumulative ST depression in the entire population as well as in patients with conclusive tests. The antiischemic medication did not affect correlation values. Conclusion: QRS score was significantly related to the extent of myocardial ischemia and the severity of coronary heart disease, thus along with the analysis of ST‐segment displacement may contribute to the more precise evaluation of exercise testing. A.N.E. 2001;6(4):310–318     

Feature-tracking cardiovascular magnetic resonance as a novel technique for the assessment of mechanical dyssynchrony

Background

Myocardial tagging using cardiovascular magnetic resonance (CMR) is the gold-standard for the assessment of myocardial mechanics. Feature-tracking cardiovascular magnetic resonance (FT-CMR) has been validated against myocardial tagging. We explore the potential of FT-CMR in the assessment of mechanical dyssynchrony, with reference to patients with cardiomyopathy and healthy controls.

Methods

Healthy controls (n = 55, age: 42.9 ± 13 yrs, LVEF: 70 ± 5%, QRS: 88 ± 9 ms) and patients with cardiomyopathy (n = 108, age: 64.7 ± 12 yrs, LVEF: 29 ± 6%, QRS: 147 ± 29 ms) underwent FT-CMR for the assessment of the circumferential (CURE) and radial (RURE) uniformity ratio estimate based on myocardial strain (both CURE and RURE: 0 to 1; 1 = perfect synchrony)

Results

CURE (0.79 ± 0.14 vs. 0.97 ± 0.02) and RURE (0.71 ± 0.14 vs. 0.91 ± 0.04) were lower in patients with cardiomyopathy than in healthy controls (both p < 0.0001). CURE (area under the receiver-operator characteristic curve [AUC]: 0.96), RURE (AUC: 0.96) and an average of these (CURE:RURE_AVG, AUC: 0.98) had an excellent ability to discriminate between patients with cardiomyopathy and controls (sensitivity 90%; specificity 98% at a cut-off of 0.89). The time taken for semi-automatically tracking myocardial borders was 5.9 ± 1.4 min.

Conclusion

Dyssynchrony measures derived from FT-CMR, such as CURE and RURE, provide almost absolute discrimination between patients with cardiomyopathy and healthy controls. The rapid acquisition of these measures, which does not require specialized CMR sequences, has potential for the assessment of mechanical dyssynchrony in clinical practice.     

New ST-segment elevation myocardial infarction criteria for left bundle branch block based on QRS area

Background

ECG detection of ST-segment elevation myocardial infarction (STEMI) in the presence of left bundle-branch block (LBBB) is challenging due to ST deviation from the altered conduction. The purpose of this study was to introduce a new algorithm for STEMI detection in LBBB and compare the performance to three existing algorithms.

Methods

Source data of the study group (143 with acute MI and 239 controls) comes from multiple sources. ECGs were selected by computer interpretation of LBBB. Acute MI reference was hospital discharge diagnosis. Automated measurements came from the Philips DXL algorithm. Three existing algorithms were compared, (1) Sgarbossa criteria, (2) Selvester 10% RS criteria and (3) Smith 25% S-wave criteria. The new algorithm uses an ST threshold based on QRS area. All algorithms share the concordant ST elevation and anterior ST depression criteria from the Sgarbossa score. The difference is in the threshold for discordant ST elevation. The Sgarbossa, Selvester, Smith and Philips discordant ST elevation criteria are (1) ST elevation ≥ 500 μV, (2) ST elevation ≥ 10% of |S|-|R| plus STEMI limits, (3) ST elevation ≥ 25% of the S-wave amplitude and (4) ST elevation ≥ 100 μV + 1050 μV/Ash * QRS area. The Smith S-wave and Philips QRS area criteria were tested using both a single and 2 lead requirement. Algorithm performance was measured by sensitivity, specificity, and positive likelihood ratio (LR +).

Results

Algorithm performance can be organized in bands of similar sensitivity and specificity ranging from Sgarbossa score ≥ 3 with the lowest sensitivity and highest specificity, 13.3% and 97.9%, to the Selvester 10% rule with the highest sensitivity and lower specificity of 30.1% and 93.2%. The Smith S-wave and Philips QRS area algorithms were in the middle band with sensitivity and specificity of (20.3%, 94.9%) and (23.8%, 95.8%) respectively.

Conclusion

As can be seen from the difference between Sgarbossa score ≥ 3 and other algorithms for STEMI in LBBB, a discordant ST elevation criterion improves the sensitivity for detection but also results in a drop in specificity. For applications of automated STEMI detection that require higher sensitivity, the Selvester algorithm is better. For applications that require a low false positive rate such as relying on the algorithm for pre-hospital activation of cardiac catheterization laboratory for urgent PCI, it may be better to use the 2 lead Philips QRS area or Smith 25% S-wave algorithm.     

Enhanced recognition of ischemia by three variable analysis of the exercise stress test

Background

ECG ST-segment deviations have been the standard measure of coronary artery disease (CAD) during the exercise stress test (EST). Our past research has shown other ECG variables to be significant in EST. This study evaluates the benefit of routinely combining these variables in the detection of CAD.

Methods

Sequential patients (n = 439) with suspected CAD referred for EST had their cases reviewed. Clinical and ECG variables were associated with myocardial perfusion imaging (MPI) scintigrams used to detect ischemia during maximum EST.

Results

An increase in P-wave duration was the most sensitive predictor of ischemia with a sensitivity of 64.3%, a specificity of 86.5%, and a positive predictive power (PPP) of 57.8%. ST elevation ≥ 1 mm in lead AVR had a sensitivity of 53.1%, a specificity of 78.3%, and a PPP of 41.3%. ST depression ≥ 1 mm in leads V₄–V₆ had a sensitivity of 11.2%, a specificity of 94.7%, and a PPP of 37.9%. When these variables were combined, specificity and PPP increased to 100% (p < 0.001).

Conclusions

EST evaluation solely by ST deviation fails to identify a significant portion of ischemic cases. Combinations of ΔPWD, ST elevation in AVR, and ST depression improved the identification of ischemia.     

Minimum salvaged myocardium after rescue percutaneous coronary intervention: quantification by cardiac magnetic resonance

Introduction and objectives

When fibrinolysis fails in patients with ST elevation myocardial infarction, they are referred for a rescue percutaneous coronary intervention (PCI). However, there is still no evidence of how much myocardium potentially at risk we can actually salvage after rescue PCI.

Methods

Fifty consecutive patients. Cardiac magnetic resonance was performed within 6 days. Myocardial necrosis was defined by the extent of abnormal late enhancement, myocardium at risk by extent of edema, and the amount of salvaged myocardium by the difference between myocardium at risk and myocardial necrosis. Finally, myocardial salvage index (MSI) resulted from the fraction (area-at-risk minus infarct-size)/area-at-risk.

Results

The mean time elapsed between pain onset and fibrinolitic agent administration was 176 ± 113 min; time lysis-rescue = PCI 209 ± 122 min; time pain onset-PCI = 390 ± 152 min. The area at risk was 37% ± 13% and infarct size 34.5% ± 13%. Salvaged myocardium was 3% ± 4% and MSI 9 ± 8. Salvaged myocardium and MSI were similar between patients with the artery open on arrival at the catheterization lab (Thrombolysis in Myocardial Infarction [TIMI] 3) and those with TIMI flow ≤2 (3.3% ± 3.6% and 8.2 ± 6.9 in TIMI 0-2 vs 3.0% ± 3.7% and 10.8 ± 10.9 in TIMI 3; P = .80 and 0.31, respectively). No significant difference was observed between patients who went through rescue PCI within a shorter time and those with longer delay times.

Conclusions

The myocardial salvage after rescue PCI quantified by cardiac magnetic resonance is very small. The long delay times between pain onset and the opening of the infarct-related artery with PCI are most probably the reason for such a minimal effect of rescue PCI.Full English text available from: www.revespcardiol.org     

The Initial Electrocardiographic Pattern in Acute Myocardial Infarction

Background: The ECG is the most widely used accessory for early diagnosis and risk stratification of patients with acute myocardial infarction (AMI). Previous studies have concentrated on the association between either the number of leads with ST segment deviation (elevation and depression) or the total amount of ST segment elevation and/or depression and prognosis. However, the results are conflicting. Methods: A different method is to use the grades of ischemia as an estimate of infarct or size and prognosis. Grade I ischemia is defined as tall peak T waves with < 0.1 mV ST segment elevation; grade II as ST segment elevation with positive T waves, without distortion of the terminal portion of the QRS; and grade III as ST segment elevation, positive T waves, and distortion of the terminal portion of the QRS. Grade III ischemia on the admission ECG is associated with larger final infarct size and increased mortality. Results: In patients with inferior wall AMI, especially those with prior infarction, the pattern of precordial ST segment depression is even more important and maximal ST depression in V4-V6 is associated with high mortality. Moreover, meticulous interpretation of the initial ECG pattern provides information about the probable site of the culprit obstructive coronary lesion. Conclusion: Thus, the admission ECG of AMI can assist not only in diagnosis, but also in estimation of infarct size, correlation with the underlying coronary anatomy and risk stratification.     

Use of electrocardiographic depolarization abnormalities for detection of stress-induced ischemia as defined by myocardial perfusion imaging

High-frequency mid-QRS (HFQRS) analysis was recently introduced as a tool for identification of stress-induced ischemia. The diagnostic performance of this electrocardiographic technique has not been determined in a large cohort of patients. This study compared the diagnostic performance of HFQRS analysis to conventional ST-segment analysis in detecting exercise-induced ischemia. The study included 996 patients (56 ± 10 years of age, 670 men) referred for exercise myocardial perfusion imaging (MPI), which served as the gold standard of ischemia. High-resolution electrocardiogram was used for computer analysis of HFQRS signals. Number of electrocardiographic leads with ≥50% decrease of HFQRS intensity (L(50%)) was used as an index of ischemia. Perfusion images were evaluated semiquantitatively. Receiver operating characteristic analysis demonstrated an L(50%) ≥3 as the criterion that yielded optimal sensitivity and specificity for diagnosing moderate/severe ischemia. Compared to ST-segment analysis HFQRS analysis was more sensitive (69% vs 39%, p <0.005) and more specific (86% vs 82%, p <0.05). L(50%) correlated with amount of MPI ischemia (R(2) = 0.75, p <0.0001). Multivariate logistic regression analysis demonstrated a significant incremental diagnostic value for the addition of HFQRS data to a model containing pretest and conventional exercise parameters. L(50%) was the best predictor of mild or moderate/severe MPI ischemia. In conclusion, computerized HFQRS analysis improved the diagnostic performance of conventional stress electrocardiogram in detecting exercise-induced ischemia. Thus, this technique might aid in the noninvasive evaluation of coronary artery disease.     

Difference vectors to describe dynamics of the ST segment and the ventricular gradient in acute ischemia

Background

The ECG is important in the diagnosis and triage of the acute coronary syndrome (ACS), especially in the hyperacute phase, the “golden hours,” during which myocardial salvage possibilities are largest. An important triaging decision to be taken is whether or not a patient requires primary PCI, for which, as mentioned in the guidelines, the presence of an ST elevation (STE) pattern in the ECG is a major criterion. However, preexisting non-zero ST amplitudes (diagnostic, but also non-diagnostic) can obscure or even preclude this diagnosis.

Methods

In this study, we investigated the potential diagnostic possibilities of ischemia detection by means of changes in the ST vector, ΔST, and changes in the VG (QRST integral) vector, ΔVG. We studied the vectorcardiograms (VCGs) synthesized of the ECGs of 84 patients who underwent elective PTCA. Mean ± SD balloon occlusion times were 260 ± 76 s. The ECG ischemia diagnosis (ST elevation, STE, or non-ST-elevation, NSTE), magnitudes and orientations of the ST and VG vectors, and the differences ΔST and ΔVG with the baseline ECG were measured after 3 min of balloon occlusion.

Results

Planar angles between the ΔST and ΔVG vectors were 14.9 ± 14.0°. Linear regression of ΔVG on ΔST yielded ΔVG = 324·ΔST (r = 0.85; P < 0.0001, ΔST in mV). We adopted ΔST > 0.05 mV, and the corresponding ΔVG > 16.2 mV·ms as ischemia thresholds. The classical criteria characterized the ECGs of 46/84 (55%) patients after 3 min of occlusion as STE ECGs. Combined application of the ΔST and ΔVG criteria identified 73/84 (87%) of the patients as ischemic.

Conclusion

Differential diagnosis by ΔST and ΔVG (requiring an earlier made non-ischemic baseline ECG) could dramatically improve ECG guided detection of patients who urgently require catheter intervention.     

24小时动态心电图对冠心病的诊断价值

对41例胸痛患者进行24小时动态心电图(AECG)及冠状动脉造影检查,其中24例在作上述检查2—3周内进行平板运动试验。10例正常冠状动脉患者AECG显示心肌缺血者仅1例,特异性90％;冠状动脉病变31例中显示心肌缺血20例,敏感性65％。心肌缺血检出敏感性与冠状动脉病变程度有关,多支病变为78％,单支病变为46％(P<0.01).AECG对单支病变患者,心肌缺血检出率明显低于平板运动试验(P<0.01);对多支病变患者,心肌缺血检出率与平板运动试验相同,均为88％。     

Spatial distribution of exercise-induced ST-segment depression and U-wave inversion in identifying the ischemic site in patients with coronary artery disease

Eighty-seven unipolar electrocardiograms were simultaneously recorded before and after symptom-limited treadmill exercise in 75 patients with coronary artery narrowing (greater than equal to 70%) and without previous myocardial infarction. Body surface distributions of ST segment depression were divided into 3 types; upper, lower, and diffuse types. Body surface distributions of U-wave inversion were divided into 2 types; upper, and lower types. These distribution patterns were compared with the location of ischemia determined by T1-201 exercise myocardial perfusion imaging. For ST-segment depression, a considerable number of patients had diffuse-type ST depression, whether the site of ischemia was anterior (22/32, 69%), inferior (18/27, 67%) or both (5/5, 100%). However, upper-type ST depression was associated with anterior ischemia, and lower-type ST depression, with inferior ischemia. The sensitivity and specificity of the spatial distribution of ST depression in identifying the myocardial ischemic site were 27% and 95% for anterior ischemia. The sensitivity and specificity of the spatial distribution of St depression in identifying the myocardial ischemic site were 27% and 95% for anterior ischemia respectively, and 28% and 88% for inferior ischemia, respectively. The incidence of U-wave inversion was moderate (29/75, 39%), but the distribution pattern was specific for the site of ischemia; upper-type U inversion associated with anterior ischemia, and lower type with inferior ischemia. The sensitivity and specificity were 59% and 100% for anterior ischemia respectively, and 22% and 100% for inferior ischemia respectively. By a combination of ST-depression and U-inversion, the sensitivity and specificity were 78% and 95% for anterior ischemia, and 44% and 88% for inferior ischemia. Body surface electrocardiographic mapping provided important information in the non-invasive diagnosis of the site of myocardial ischemia.     

The Value of Upsloping ST Depression in Diagnosing Myocardial Ischemia

We evaluated the value of upsloping ST‐segment depression in predicting the severity of myocardial ischemia. Comparison of the exercise electrocardiographic changes was made to myocardial perfusion images and coronary angiograms as the criteria for ischemia. We retrospectively reviewed 621 patients who underwent exercise technetium‐99m tetrofosmin single photon emission computed tomography (SPECT) for the assessment of suspected or known coronary artery disease followed by coronary angiography within a 3‐month period. The test sensitivity and specificity of 1 mm horizontal or downsloping ST depression in predicting reversible ischemia as assessed by gated SPECT imaging (GSI) were 65% and 87%, respectively. The corresponding values were 67% and 94% compared to coronary angiography. The sensitivity and specificity of gated SPECT imaging compared to coronary angiography were 78% and 89%. On the other hand when 1 mm upsloping ST depression at 70 ms past the J‐point was regarded as abnormal, along with horizontal and downsloping, the sensitivity and specificity were 82% and 90% compared to myocardial perfusion imaging, and 77% and 92% as assessed by coronary angiography. We conclude that upsloping ST‐segment depression is associated with an increased risk of coronary artery disease and is a valuable predictor of myocardial ischemia.     

Effect of acadesine,a new metabolic agent,on exercise-induced myocardial ischemia in chronic stable angina

Summary Acadesine, the first of a class of adenosine-regulating agents, has been shown to possess antiischemic properties in animal models. The aim of the study was to assess the effect of acadesine on exercise-induced myocardial ischemia in patients with chronic stable angina pectoris. Twelve patients with stable angina entered a five-way, randomized double-blind study comparing the effects of four doses of acadesine with placebo on time to 1 mm ST-segment depression and other parameters of exercise tolerance. At each study period patients underwent baseline exercise testing, followed by drug or placebo infusion after a 60 minute rest period. The exercise test was repeated after 30 minutes infusion, which continued throughout recovery. Time to angina, time to 1 mm ST depression, and total exercise time during the placebo infusion were 301.1±45.3, 314.8±50.9, and 399.4±47.6 seconds. The placebo-adjusted percentage change in time to 1-mm ST segment with acadesine 6, 12, 24, and 48 mg/kg was –0.1±6.2%, 11.1±13.8%, 12.9±8.6%, and –3.2±6.8%, respectively (p=NS vs. baseline). Time to angina, total exercise time, and recovery time of the ST segment were not consistently altered by acadesine. The lack of effect across all acadesine doses is consistent with animal data from ischemia-reperfusion injury studies, where a clear dose dependency was present with a loss of effect at higher doses. Alternatively, the extent of ischemia induced by treadmill exercise may have been insufficient for the antiischemic activity of acadesine to be evident.     

Utility of the prehospital electrocardiogram in diagnosing acute coronary syndromes: the Myocardial Infarction Triage and Intervention (MITI) project

Objectives. We sought to determine whether the prehospital electrocardiogram (ECG) improves the diagnosis of an acute coronary syndrome.Background. The ECG is the most widely used screening test for evaluating patients with chest pain.Methods. Prehospital and in-hospital ECGs were obtained in 3,027 consecutive patients with symptoms of suspected acute myocardial infarction, 362 of whom were randomized to prehospital versus hospital thrombolysis and 2,665 of whom did not participate in the randomized trial. Prehospital and hospital records were abstracted for clinical characteristics and diagnostic outcome.Results. ST segment and T and Q wave abnormalities suggestive of myocardial ischemia or infarction were more common on both the prehospital and hospital ECGs of patients with as compared with those without acute coronary syndromes (p ≤ 0.00001). Those with prehospital thrombolysis were more likely to show resolution of ST segment elevation by the time of hospital admission (14% vs. 5% in patients treated in the hospital, p = 0.004). In patients not considered for prehospital thrombolysis, both persistent and transient ST segment and T or Q wave abnormalities discriminated those with from those without acute coronary ischemia or infarction. Compared with ST segment elevation on a single ECG, added consideration of dynamic changes in ST segment elevation between serial ECGs improved the sensitivity for an acute coronary syndrome from 34% to 46% and reduced specificity from 96% to 93% (both p < 0.00004). Overall, compared with abnormalities observed on a single ECG, consideration of serial evolution in ST segment, T or Q wave or left bundle branch block (LBBB) abnormalities between the prehospital and initial hospital ECG improved the diagnostic sensitivity for an acute coronary syndrome from 80% to 87%, with a fall in specificity from 60% to 50% (both p < 0.000006).Conclusions. ECG abnormalities are an early manifestation of acute coronary syndromes and can be identified by the prehospital ECG. Compared with a single ECG, the additional effect of evolving ST segment, T or Q waves or LBBB between serially obtained prehospital and hospital ECGs enhanced the diagnosis of acute coronary syndromes, but with a fall in specificity.     

Consideration of QRS complex in addition to ST-segment abnormalities in the estimation of the “risk region” during acute anterior or inferior myocardial infarction

The myocardial area at risk (MaR) is an important aspect in acute ST-elevation myocardial infarction (STEMI). It represents the myocardium at the onset of the STEMI that is ischemic and could become infarcted if no reperfusion occurs. The MaR, therefore, has clinical value because it gives an indication of the amount of myocardium that could potentially be salvaged by rapid reperfusion therapy. The most validated method for measuring the MaR is ^99mTc-sestamibi SPECT, but this technique is not easily applied in the clinical setting. Another method that can be used for measuring the MaR is the standard ECG-based scoring system, Aldrich ST score, which is more easily applied. This ECG-based scoring system can be used to estimate the extent of acute ischemia for anterior or inferior left ventricular locations, by considering quantitative changes in the ST-segment. Deviations in the ST-segment baseline that occur following an acute coronary occlusion represent the ischemic changes in the transmurally ischemic myocardium. In most instances however, the ECG is not available at the very first moments of STEMI and as times passes the ischemic myocardium becomes necrotic with regression of the ST-segment deviation along with progressive changes of the QRS complex. Thus over the time course of the acute event, the Aldrich ST score would be expected to progressively underestimate the MaR, as was seen in studies with SPECT as gold standard; anterior STEMI (r = 0.21, p = 0.32) and inferior STEMI (r = 0.17, p = 0.36). Another standard ECG-based scoring system is the Selvester QRS score, which can be used to estimate the final infarct size by considering the quantitative changes in the QRS complex. Therefore, additional consideration of the Selvester QRS score in the acute phase could potentially provide the “component” of infarcted myocardium that is missing when the Aldrich ST score alone is used to determine the MaR in the acute phase, as was seen in studies with SPECT as gold standard: anterior STEMI (r = 0.47, p = 0.02) and inferior STEMI (r = 0.58, p < 0.001). The aim of this review will be to discuss the findings regarding the combining of the Aldrich ST score and initial Selvester QRS score in determining the MaR at the onset of the event in acute anterior or inferior ST-elevation myocardial infarction.     

New Electrocardiographic Criteria to Differentiate Acute Pericarditis and Myocardial Infarction

Objective

Transmural myocardial ischemia induces changes in QRS complex and QT interval duration but, theoretically, these changes might not occur in acute pericarditis provided that the injury is not transmural. This study aims to assess whether QRS and QT duration permit distinguishing acute pericarditis and acute transmural myocardial ischemia.

Methods

Clinical records and 12-lead electrocardiogram (ECG) at ×2 magnification were analyzed in 79 patients with acute pericarditis and in 71 with acute ST-segment elevation myocardial infarction (STEMI).

Results

ECG leads with maximal ST-segment elevation showed longer QRS complex and shorter QT interval than leads with isoelectric ST segment in patients with STEMI (QRS: 85.9 ± 13.6 ms vs 81.3 ± 10.4 ms, P = .01; QT: 364.4 ± 38.6 vs 370.9 ± 37.0 ms, P = .04), but not in patients with pericarditis (QRS: 81.5 ± 12.5 ms vs 81.0 ± 7.9 ms, P = .69; QT: 347.9 ± 32.4 vs 347.3 ± 35.1 ms, P = .83). QT interval dispersion among the 12-ECG leads was greater in STEMI than in patients with pericarditis (69.8 ± 20.8 ms vs 50.6 ± 20.2 ms, P <.001). The diagnostic yield of classical ECG criteria (PR deviation and J point level in lead aVR and the number of leads with ST-segment elevation, ST-segment depression, and PR-segment depression) increased significantly (P = .012) when the QRS and QT changes were added to the diagnostic algorithm.

Conclusions

Patients with acute STEMI, but not those with acute pericarditis, show prolongation of QRS complex and shortening of QT interval in ECG leads with ST-segment elevation. These new findings may improve the differential diagnostic yield of the classical ECG criteria.     

Improvement of myocardial function and perfusion after successful percutaneous revascularization in patients with chronic total coronary occlusion

Background

Percutaneous coronary intervention (PCI) for chronic total occlusion (CTO) of a coronary artery can provide benefits in terms of myocardial function and survival but the procedure is complex and the success rate is relatively low. To assess these benefits, myocardial function, ischemia and viability should be clearly determined by means of a reliable diagnostic test. This study aimed to assess ventricular function and myocardial ischemia before and after PCI for CTO using cardiac magnetic resonance (CMR). NYHA functional class was also assessed before and after PCI.

Methods and results

CMR studies were performed in 43 consecutive patients (7 females; aged 64 ± 9.6 y.o.) with CTO scheduled for PCI and repeated 6 months post-PCI. PCI was successful in 33 (77%) of them. In this group CMR had shown inducible perfusion defects in 26 (79%) before PCI, while they were observed in 10 (30%) post-PCI CMR study (p < 0.001). The number of segments showing inducible perfusion defect (3.4 ± 2 prevs. 2.9 ± 4.5 post-PCI, p = 0.002) was significantly reduced in this group. Regional contractile function of segments showing viability also improved significantly in the group with successful CTO PCI compared to the group with an unsuccessful procedure. NYHA functional class for angina also improved in patients with successful revascularization while it remained unchanged in the group with unsuccessful procedures.

Conclusions

A successful CTO PCI leads to a reduction in inducible myocardial ischemia and to an improvement in regional wall motion, which results in clinical improvement.     

Caveolin-3 expression and caveolae are required for isoflurane-induced cardiac protection from hypoxia and ischemia/reperfusion injury

Volatile anesthetics protect the heart from ischemia/reperfusion injury but the mechanisms for this protection are poorly understood. Caveolae, sarcolemmal invaginations, and caveolins, scaffolding proteins in caveolae, localize molecules involved in cardiac protection. We tested the hypothesis that caveolae and caveolins are essential for volatile anesthetic-induced cardiac protection using cardiac myocytes (CMs) from adult rats and in vivo studies in caveolin-3 knockout mice (Cav-3^−/−). We incubated CM with methyl-β-cyclodextrin (MβCD) or colchicine to disrupt caveolae formation, and then exposed the myocytes to the volatile anesthetic isoflurane (30 min, 1.4%), followed by simulated ischemia/reperfusion (SI/R). Isoflurane protected CM from SI/R [23.2 ± 1.6% vs. 71.0 ± 5.8% cell death (assessed by trypan blue exclusion), P < 0.001] but this protection was abolished by MβCD or colchicine (84.9 ± 5.5% and 64.5 ± 6.1% cell death, P < 0.001). Membrane fractionation by sucrose density gradient centrifugation of CM treated with MβCD or colchicine revealed that buoyant (caveolae-enriched) fractions had decreased phosphocaveolin-1 and caveolin-3 compared to control CM. Cardiac protection in vivo was assessed by measurement of infarct size relative to the area at risk and cardiac troponin levels. Isoflurane-induced a reduction in infarct size and cardiac troponin relative to control (infarct size: 26.5% ± 2.6% vs. 45.3% ± 5.4%, P < 0.01; troponin: 27.7 ± 4.4 vs. 77.7 ± 11.8 ng/ml, P < 0.05). Isoflurane-induced cardiac protection was abolished in Cav-3^−/− mice (infarct size: 53.4% ± 6.1% vs. 53.2% ± 3.5%, P < 0.01; troponin: 102.1 ± 22.3 vs. 105.9 ± 8.2 ng/ml, P < 0.01). Isoflurane-induced cardiac protection is thus dependent on the presence of caveolae and the expression of caveolin-3. We conclude that caveolae and caveolin-3 are critical for volatile anesthetic-induced protection of the heart from ischemia/reperfusion injury.     

QRS波宽度及aVR导联ST段抬高对NSTE-ACS左主干或三支病变的预测作用

目的研究非ST段抬高型急性冠脉综合征(NSTE-ACS)患者心电图的QRS波宽度及aVR导联抬高幅度对冠状动脉左主干/三支病变的诊断价值。方法分析106例NSTE-ACS患者的体表心电图QRS波宽度及aVR导联ST段抬高幅度,通过与冠状动脉造影结果对比,研究其对诊断左主干/三支病变的敏感性、特异性和相关性。结果 QRS波宽度及aVR导联ST段抬高是左主干/三支病变的独立预测因子,OR值分别为9.04(95%CI,4.88～16.7)、7.10(95%CI,4.91～76.2);QRS间期≥90ms和aVR导联ST段抬高≥0.5mm预测左主干/三支病变的敏感性及特异性分别为88%、76%及88%、86%。结论 QRS波增宽及aVR导联ST段抬高是NSTE-ACS患者左主干/三支病变较为灵敏的预测因子。     

Diagnostic value of electrocardiogram and vectorcardiogram in postinfarction ventricular asynergy

The ability of ECG-VCG to predict the severity of postinfarction LV asynergy was evaluated in 152 patients with previous myocardial infarction who underwent left cineventriculography in the right anterior oblique view. Various ECG and VCG signs were examined in order to predict the existence of severe asynergy in general (dyskinesia or akinesia or severe hypokinesia) and of dyskinesia in particular. In patients with inferior myocardial infarction (Group A) persistent ST segment elevation was the only specific ECG sign (100%) of severe asynergy; it had a poor sensitivity (6.2%). Four frontal VCG signs (presence of terminal bite, y- greater than 0.18 mV, maximum early superior vector along x axis = MESV greater than or equal to 1.3 mV, duration of initial superior forces = DISF greater than 50 msec) increased the sensitivity of the ECG-VCG method to 75.8% while maintaining a 100% specificity. Regarding the diagnosis of dyskinesia, only the ECG sign of persistent ST segment elevation and the VCG sign of y- greater than or equal to 0.3 mV had a 100% specificity. The sensitivity of the ECG-VCG method was 33.3% (16.6% ECG and 16.6% VCG). In patients with anterior myocardial infarction (Group B), concerning the diagnosis of severe asynergy, the ECG signs of sigma ST greater than 3 mm in anterior leads; pathologic Q wave in four or more anterior leads (including D1 and aVL); and the presence of LAH or LAH + RBBB, had a 100% specificity and a good sensitivity (60.5%). The VCG sign of a narrow horizontal QRS loop increased the sensitivity of the ECG-VCG method to 71% while maintaining a 100% specificity. As for the diagnosis of dyskinesia, the ECG signs with a 100% specificity were sigma ST greater than or equal to 5 mm in anterior leads, a pathologic Q wave in more than five anterior leads (including I and a VL) and RBBB + LAH; these variables had a sensitivity of 48.3%. The VCG sign of a narrow horizontal QRS loop increased the sensitivity of the ECG-VCG method to 79.3% while maintaining a 100% specificity. In patients with inferior plus anterior myocardial infarction (Group A + B) the signs mentioned above for each group were evaluated, confirming a 100% specificity. Regarding the diagnosis of severe asynergy, the ECG signs had a sensitivity of 61.3%, while VCG increased the sensitivity of the ECG-VCG method to 90.3%.(ABSTRACT TRUNCATED AT 400 WORDS)