The value of both ST-segment and QRS complex changes during acute coronary occlusion for prediction of reperfusion-induced myocardial salvage in a canine model

Intravenous metoprolol during ongoing STEMI ameliorates markers of ischemic injury: a METOCARD-CNIC trial electrocardiographic study

Besides its protective effect against neutrophil-mediated injury at reperfusion, intravenous (IV) metoprolol was recently shown to reduce the progression of ischemic injury in a pig model of ST-segment elevation myocardial infarction (STEMI). Here, we tested the hypothesis that IV metoprolol administration in humans with ongoing STEMI blunts the time‑dependent progression of ischemic injury assessed by serial electrocardiogram (ECG) evaluations before reperfusion. The METOCARD-CNIC trial randomized 270 anterior STEMI patients to IV metoprolol or control before reperfusion by percutaneous coronary intervention (PCI). In 139 patients (69 IV metoprolol, 70 controls), two ECGs were available (ECG-1 before randomization, ECG-2 pre-PCI). Between-group ECG differences were analyzed using univariate and multivariate regression models. No significant between-group differences were observed on ECG-1. On ECG-2, patients who received IV metoprolol had a narrower QRS than those in the control group (84 ms vs. 90 ms, p = 0.029), a lower prevalence of QRS distortion (10% vs. 26%, p = 0.017), and a lower sum of anterior and total ST-segment elevation (10.1 mm vs. 13.6 mm, p = 0.014 and 10.4 mm vs. 14.0 mm, p = 0.015, respectively). Adjusted analysis revealed similar results. Significant associations were observed between ECG-2 variables and cardiac magnetic resonance imaging measurements (extent of myocardial edema, infarct size, microvascular obstruction, and left-ventricular ejection fraction) after STEMI. In summary, IV metoprolol administration before reperfusion ameliorates ECG markers of myocardial ischemia in anterior STEMI patients. These data confirm that IV metoprolol is able to reduce ischemic injury and highlight the ability of ECG analysis to provide relevant real-time information on the effect of cardioprotective therapies before reperfusion.

Effect of Ischemic Preconditioning and Postconditioning on Exosome-Rich Fraction microRNA Levels, in Relation with Electrophysiological Parameters and Ventricular Arrhythmia in Experimental Closed-Chest Reperfused Myocardial Infarction

We investigated the antiarrhythmic effects of ischemic preconditioning (IPC) and postconditioning (PostC) by intracardiac electrocardiogram (ECG) and measured circulating microRNAs (miRs) that are related to cardiac conduction. Domestic pigs underwent 90-min. percutaneous occlusion of the mid left anterior coronary artery, followed by reperfusion. The animals were divided into three groups: acute myocardial infarction (AMI, n = 7), ischemic preconditioning-acute myocardial infarction (IPC-AMI) (n = 9), or AMI-PostC (n = 5). IPC was induced by three 5-min. episodes of repetitive ischemia/reperfusion cycles (rI/R) before AMI. PostC was induced by six 30-s rI/R immediately after induction of reperfusion 90 min after occlusion. Before the angiographic procedure, a NOGA endocardial mapping catheter was placed again the distal anterior ventricular endocardium to record the intracardiac electrogram (R-amplitude, ST-Elevation, ST-area under the curve (AUC), QRS width, and corrected QT time (QTc)) during the entire procedure. An arrhythmia score was calculated. Cardiac MRI was performed after one-month. IPC led to significantly lower ST-elevation, heart rate, and arrhythmia score during ischemia. PostC induced a rapid recovery of R-amplitude, decrease in QTc, and lower arrhythmia score during reperfusion. Slightly higher levels of miR-26 and miR-133 were observed in AMI compared to groups IPC-AMI and AMI-PostC. Significantly lower levels of miR-1, miR-208, and miR-328 were measured in the AMI-PostC group as compared to animals in group AMI and IPC-AMI. The arrhythmia score was not significantly associated with miRNA plasma levels. Cardiac MRI showed significantly smaller infarct size in the IPC-AMI group when compared to the AMI and AMI-PostC groups. Thus, IPC led to better left ventricular ejection fraction at one-month and it exerted antiarrhythmic effects during ischemia, whereas PostC exhibited antiarrhythmic properties after reperfusion, with significant downregulaton of ischemia-related miRNAs.

Ischemic QRS prolongation as a predictor of ventricular fibrillation in a canine model

OBJECTIVES

An acute coronary occlusion and its possible subsequent complications is one of the most common causes of death. One such complication is ventricular fibrillation (VF) due to myocardial ischemia. The severity of ischemia is related to the amount of coronary arterial collateral flow. In dog studies collateral flow has also been shown to be associated with QRS prolongation. The aim of this study was to investigate whether ischemic QRS prolongation (IQP) is associated with impending VF in an experimental acute ischemia dog model.

METHODS

Degree of IQP and occurrence of VF were measured in dogs (n = 21) during coronary occlusion for 15 min and also during subsequent reperfusion (experiments conducted in 1984).

RESULTS

There was a significant difference in absolute IQP between dogs which developed VF during reperfusion (47 ± 29 ms, mean ± SD) and those which did not (12 ± 10 ms; p = .001).

CONCLUSIONS

IQP during acute coronary occlusion is associated with reperfusion VF in an experimental dog model and might therefore be a potential predictor of malignant arrhythmias in patients with acute coronary syndrome.

Association between QRS duration on prehospital ECG and mortality in patients with suspected STEMI

BACKGROUND

QRS duration has previously shown association with mortality in patients with acute myocardial infarction treated with thrombolytics, less is known in patients with suspected ST segment elevation myocardial infarction (STEMI) when assessing QRS duration on prehospital ECG. Thus, the objective was to investigate the prognostic effect of QRS duration on prehospital ECG and presence of classic left and right bundle branch block (LBBB/RBBB) for all-cause mortality in patients with suspected STEMI.

METHOD

In total 2105 consecutive patients (mean age 64±13years, 72% men) with suspected STEMI were prospectively included. QRS duration was registered from automated QRS measurement on prehospital ECG and patients were divided according to quartiles of QRS duration (<89ms, 89-98ms, 99-111ms and >111ms). Primary endpoint was all-cause 30-day mortality. Predictors of all-cause mortality were assessed using Cox proportional hazards analysis.

RESULTS

Among all patients median QRS duration was 98ms (IQR 88-112ms). RBBB-morphology was seen in 126 patients (6.0%) and LBBB in 88 patients (4.2%), 80% were treated with percutaneous coronary intervention and the final diagnosis was STEMI in 1777 patients (84%). Thirty-day mortality was 7.6% in patients with suspected STEMI. In multivariable analysis, QRS duration>111ms (hazard ratio (HR) 3.08; 95% confidence interval (CI): 1.71-5.57, p=0.0002), LBBB - morphology (HR 3.0; 95% CI: 1.38-6.53, p=0.006) and RBBB (HR 3.68; 95% CI: 1.95-6.95, p<0.0001) were associated with 30 day all-cause mortality.

CONCLUSION

In patients with suspected STEMI, QRS prolongation, LBBB, and RBBB on prehospital ECG are associated with increased risk of death.

An electrocardiographic sign of ischemic preconditioning

Ischemic preconditioning is a form of intrinsic cardioprotection where an episode of sublethal ischemia protects against subsequent episodes of ischemia. Identifying a clinical biomarker of preconditioning could have important clinical implications, and prior work has focused on the electrocardiographic ST segment. However, the electrophysiology biomarker of preconditioning is increased action potential duration (APD) shortening with subsequent ischemic episodes, and APD shortening should primarily alter the T wave, not the ST segment. We translated findings from simulations to canine to patient models of preconditioning to test the hypothesis that the combination of increased [delta (Δ)] T wave amplitude with decreased ST segment elevation characterizes preconditioning. In simulations, decreased APD caused increased T wave amplitude with minimal ST segment elevation. In contrast, decreased action potential amplitude increased ST segment elevation significantly. In a canine model of preconditioning (9 mongrel dogs undergoing 4 ischemia-reperfusion episodes), ST segment amplitude increased more than T wave amplitude during the first ischemic episode [ΔT/ΔST slope = 0.81, 95% confidence interval (CI) 0.46-1.15]; however, during subsequent ischemic episodes the T wave increased significantly more than the ST segment (ΔT/ΔST slope = 2.43, CI 2.07-2.80) (P < 0.001 for interaction of occlusions 2 vs. 1). A similar result was observed in patients (9 patients undergoing 2 consecutive prolonged occlusions during elective percutaneous coronary intervention), with an increase in slope of ΔT/ΔST of 0.13 (CI -0.15 to 0.42) in the first occlusion to 1.02 (CI 0.31-1.73) in the second occlusion (P = 0.02). This integrated analysis of the T wave and ST segment goes beyond the standard approach to only analyze ST elevation, and detects cellular electrophysiology changes of preconditioning.

Roles of collateral arterial flow and ischemic preconditioning in protection of acutely ischemic myocardium

The extent and rate at which necrosis develops in experimental acute myocardial infarction in the dog heart is presented together with an analysis of the role played by protective mechanisms in myocyte death. Preconditioning with ischemia delays but does not prevent myocyte death. Arterial collateral flows exceeding 30% of control flow essentially prevent myocyte death, while lesser amounts of collateral flow delay myocyte death to a variable extent. Flows of <0.09mlmin(-1)g(-1) wet exert no protective effect. Cell death occurs as quickly as it does with zero flow. Electrocardiography provides a means of detection of the preconditioned state in the dog heart in that the amount of ST elevation observed during the preconditioning episode is reduced during subsequent episodes of ischemia. Also, marked depression of arterial collateral flow can be detected by an increase in the duration of the QRS segment.

Directionality and proportionality of the ST and ventricular gradient difference vectors during acute ischemia

BACKGROUND

The ECG is important in diagnosis and triage in the initial phase of the acute coronary syndrome (ACS). The primary goal of making an ECG at first medical contact should be the reliable detection of cardiac ischemia, thus facilitating a correct triage by corroborating the diagnosis of ACS. Ischemia detection by ST amplitude analysis is limited to situations in which there is an identifiable J point. The ventricular gradient (VG) is independent of conduction and might be an alternative ECG-based variable for ischemia detection.

METHODS

We studied vectorcardiograms (VCGs) synthesized of the ECGs of 67 patients who underwent elective PTCA with prolonged balloon occlusions (mean±SD occlusion duration 214±77s), and computed, during occlusions, the changes of the ST and VG vectors with respect to baseline, ΔST and ΔVG, and the angle between these vectors, ∠(ΔST, ΔVG). We then analyzed directionality and proportionality of ΔST and ΔVG by performing linear regressions of ∠(ΔST, ΔVG) on time after occlusion, and of ΔVG on ΔST, respectively.

RESULTS

Linear regression of ∠(ΔST, ΔVG) on time after occlusion yielded a slope of 1.55*10(-3) °/s and an intercept of 11.96°; r(2)<0.001 (NS). Linear regression of ΔVG on ΔST on all data yielded a slope of 253mV and an intercept of 14.4mV•ms; r(2)=0.75 (P<0.001). Broken stick linear regression (breakpoint ΔST=0.255mV) yielded slopes of 330mV and 160mV, intercepts of 5.6mV•ms and 47.2mV•ms, and r(2) values of 0.66 (P<0.001) and 0.63 (P<0.001) for the smaller and larger ΔST values, respectively.

CONCLUSION

Our study suggests that, because of the directionality and proportionality between ΔST and ΔVG, the change in the ventricular gradient, ΔVG, between a reference ECG and an ischemic ECG is a meaningful measure of ischemia.

Transient and rapid QRS-widening associated with a J-wave pattern predicts impending ventricular fibrillation in experimental myocardial infarction

BACKGROUND

Certain types of the early repolarization phenomenon, previously considered to be benign, have been reported to be associated with ventricular fibrillation (VF), both in population-based studies and in the myocardial infarction (MI) settings.

OBJECTIVE

To analyze whether QRS widening and appearance of a J-wave pattern in experimental MI settings is predictive of VF.

METHODS

MI was induced in 32 pigs by 40-minute inflation of an angioplasty balloon in the left descending artery, and electrocardiogram was continuously recorded. Multilead QRS boundaries were computed, and QRS duration was calculated on a beat-to-beat basis during the occlusion period for each pig. An association between QRS widening and subsequent VF was studied using receiver operating characteristic curve analysis. Electrocardiograms at maximum QRS duration were reviewed for the presence of a J-wave pattern.

RESULTS

Sixteen animals had VF episodes during the occlusion period. Two peaks of QRS widening were found in all animals: the first peak immediately on left descending artery occlusion and the second peak 19.1 ± 4.0 minutes later. The magnitude of changes in the QRS width over time had significant interindividual differences. A QRS widening of ≥28 ms during a 3-minute time window was observed in 14 animals and predicted impending VF (selectivity 80%, specificity 73%, positive predictive value 57%, and negative predictive value 89%; P = .008). In 10 of 14 (71%) pigs, a J-wave pattern appeared at maximal QRS duration. The appearance of a J-wave pattern predicted VF with selectivity 80%, specificity 68%, positive predictive value 53%, and negative predictive value 88% (P = .02).

CONCLUSION

Transient QRS widening, commonly associated with a J-wave pattern, appears to predict impending VF in acute ischemia settings and motivates further clinical studies for monitoring immediate risk of VF in MI.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

A new electrocardiographic marker of myocardial reperfusion in patients with acute ST-segment elevation myocardial infarction treated with primary percutaneous intervention: the value of QRS duration

AIMS

Although ischaemia-induced QRS complex changes have been described previously, their relation with reperfusion status is not clear. We aimed to investigate the relation of QRS duration with reperfusion at tissue level compared to myocardial blush in patients with acute myocardial infarction who underwent successful primary percutaneous coronary angioplasty.

METHODS AND RESULTS

One hundred and forty-eight patients were enrolled. Based on the post-angioplasty myocardial blush grade (MBG), patients were divided into reperfusion (grades 2 and 3) and impaired reperfusion (grades 0 and 1) groups. Although the two groups did not differ in terms of admission QRS duration (81±17 vs. 79±15 msec, p=0.473), the patients in the impaired reperfusion group had a significantly longer QRS duration both at immediate post-angioplasty (78±18 vs. 68±17 msec, p=0.001) and at the 60th minute ECG (77±17 vs. 60±17 msec, p<0.001). Patients in the impaired reperfusion group revealed significantly less narrowing of QRS duration in the post-angioplasty 60th minute ECG (6±5 vs. 20±5 msec, p<0.001) when compared to the patients in the reperfusion group. After adjusting all variables, QRS narrowing in the 60th minute ECG was determined as an independent electrocardiographic predictor of reperfusion (OR:1.39, 95% CI: 1.25-1.54, p<0.001).

CONCLUSIONS

We demonstrated that QRS duration is a strong indicator of myocardial reperfusion status.

Myocardial ischemia analysis based on electrocardiogram QRS complex

Electrocardiogram (ECG) is an economic, convenient, and non-invasive detecting tool in myocardial ischemia (MI), and its clinical appearance is mainly exhibited by the changes in ST-T complex. Recently, QRS complex characters were proposed to analyze MI by more and more researchers. In this paper, various QRS complex characters were extracted in ECG signals, and their relationship was analyzed systematically. As a result, these characters were divided into two groups, and there existed good relationship among them for each group, while the poor relationship between the groups. Then these QRS complex characters were applied for statistical analysis on MI, and five characters had significant differences after ECG recording verification, which were: QRS upward and downward slopes, transient heart rate, angle R and angle Q. On the other hand, these QRS complex characters were analyzed in frequency domain. Experimental results showed that the frequency features of RR interval series (Heart Rate Variability, HRV), and QRS barycenter sequence had significant differences between MI states and normal states. Moreover, QRS barycenter sequence performed better.

Effects of ischemic preconditioning and arterial collateral flow on ST-segment elevation and QRS complex prolongation in a canine model of acute coronary occlusion

BACKGROUND

During acute myocardial infarction, both ST elevation and QRS distortion on the initial electrocardiogram (ECG) have been correlated with poorer prognosis. Studies in dogs and humans suggest that these ECG markers provide information about myocardial protection from both collateral blood flow and ischemic preconditioning.

METHODS

In a protocol designed to precondition the heart with ischemia, we examined both ST-segment elevation and QRS complex prolongation in lead II of the ECG in 23 mongrel dogs during the first and fourth episode of 5 minutes of left circumflex artery occlusion. Myocardial collateral flow was measured during each of these episodes by injection of radioactive microspheres 2.5 minutes into the episode of ischemia.

RESULTS

During ischemia, the degree of elevation of the ST segments was reduced markedly in hearts preconditioned with ischemia and/or in hearts with the greatest amounts of collateral arterial flow. During the first episode of ischemia, the ST segments increased to a similar extent in severe and moderate ischemia, but less in hearts in which the ischemia was mild. However, marked QRS prolongation was present only in hearts with severe ischemia, and decreased when the hearts were preconditioned. In addition, large ischemic beds exhibited the most marked QRS prolongation, whereas small but even severely ischemic beds showed little or no change in QRS duration.

CONCLUSION

Both ST elevation and QRS prolongation are reduced by the presence of collateral flow and ischemic preconditioning. The QRS complex merits further study as an important marker of the degree of myocardial protection during human acute myocardial ischemia/infarction.

In vivo cardioprotection by S-nitroso-2-mercaptopropionyl glycine

The reversible S-nitrosation and inhibition of mitochondrial complex I is a potential mechanism of cardioprotection, recruited by ischemic preconditioning (IPC), S-nitrosothiols, and nitrite. Previously, to exploit this mechanism, the mitochondrial S-nitrosating agent S-nitroso-2-mercaptopropionyl glycine (SNO-MPG) was developed, and protected perfused hearts and isolated cardiomyocytes against ischemia-reperfusion (IR) injury. In the present study, the murine left anterior descending coronary artery (LAD) occlusion model of IR injury was employed, to determine the protective efficacy of SNO-MPG in vivo. Intraperitoneal administration of 1 mg/kg SNO-MPG, 30 min prior to occlusion, significantly reduced myocardial infarction and improved EKG parameters, following 30 min occlusion plus 2 or 24 h reperfusion. SNO-MPG protected to the same degree as IPC, and notably was also protective when administered at reperfusion. Cardioprotection was accompanied by increased mitochondrial protein S-nitrosothiol content, and inhibition of complex I, both of which were reversed after 2 h reperfusion. Finally, hearts from mice harboring a heterozygous mutation in the complex I NDUSF4 subunit were refractory to protection by either SNO-MPG or IPC, suggesting that a fully functional complex I, capable of reversible inhibition is critical for cardioprotection. Overall, these results are consistent with a role for mitochondrial S-nitrosation and complex I inhibition in the cardioprotective mechanism of IPC and SNO-MPG in vivo.

Relationship of admission QRS duration and changes in QRS duration with myocardial reperfusion in patients with acute ST segment elevation myocardial infarction (STEMI) treated with fibrinolytic therapy

BACKGROUND

Although ischemia induced QRS complex changes have been described previously, their relationship with impaired reperfusion, which is known to be associated with poor clinical outcomes, is not clear.

METHODS AND RESULTS

To investigate the relationship of QRS duration changes with myocardial reperfusion, we studied 165 acute myocardial infarction (MI) patients who were administered fibrinolytic therapy for reperfusion. For each patient, 12-lead electrocardiogram (ECG) with a paper speed of 50 mm/s was recorded on admission and repeated at the 60(th) and 90(th) min following fibrinolytic therapy. Based on the myocardial blush grades obtained from a control coronary angiography, patients were divided into reperfusion (grades 2, 3) and impaired reperfusion (grades 0, 1) groups. We detected impaired reperfusion in 74 patients. The patients in the impaired reperfusion group were older, more often diabetic, and had longer pain-to-needle intervals. They also had significantly longer QRS durations at admission compared to reperfusion group patients (91+/-11 vs 79+/-11 ms, p<0.001). Reperfusion group patients showed significantly greater resolution in QRS duration at the 90(th) min post fibrinolysis ECG (18+/-5 vs 5+/-4 ms, p<0.001). In regression analysis, the pain-to-needle time (odds ratio (OR): 0.55, 95% confidence interval (CI) 0.35-0.88, p=0.012), QRS duration on admission (OR: 0.80, 95% CI 0.67-0.97, p=0.021), and change in QRS duration at the post fibrinolysis 90(th) min ECG (OR: 2.43, 95% CI, 1.29-4.60, p=0.006) were determined as independent predictors of adequate reperfusion.

CONCLUSION

The present study, for the first time, has shown that admission QRS duration and post fibrinolysis 90(th) min QRS duration changes are related to tissue reperfusion in fibrinolytic administered acute MI patients.

Distortion of the terminal portion of the QRS is predictor of shock after primary percutaneous coronary intervention for acute myocardial infarction

BACKGROUND

Although invasive management of ST segment elevation myocardial infarction has improved the clinical outcome, cardiogenic shock (CS) remains an important issue. Our purpose was to asses the utility of the initial electrocardiogram in detecting patients who are at increased risk of CS after percutaneous coronary intervention for acute myocardial infarction.

METHODS

We evaluated 508 consecutive patients admitted in our Coronary Unit and treated by primary angioplasty within 12 h of an ST segment elevation myocardial infarction. Patients with cardiogenic shock at admission were excluded. Two groups were defined according to the presence of distortion of the terminal portion of the QRS in two or more adjacent leads (group 1) or the absence of this pattern (group 2).

RESULTS

There were 99 patients (20%) in group 1 and 409 (80%) in group 2. CS developed in 38 patients, 18 in group 1 (18%) and 20 in group 2 (5%), p<0.001. Seventeen patients died in hospital, 6 in group 1 (6%) and 11 in group 2 (3%), p 0.094. Multivariate analysis including clinical, electrocardiographic and angiographic variables showed distortion of the QRS as an independent predictor of cardiogenic shock (odds ratio 3.17, 95% confidence interval 1.44 to 6.96, p 0.004), together with Killip class at admission and TIMI 3 flow after revascularization.

CONCLUSIONS

Distortion of the terminal portion of the QRS complex is a strong predictor of cardiogenic shock in STEMI patients. Close hemodynamic monitoring should be warranted in patients showing this electrocardiographic pattern.

Relation of admission QRS duration with development of angiographic no-reflow in patients with acute ST-segment elevation myocardial infarction treated with primary percutaneous interventions

BACKGROUND

Although QRS-complex changes during ischemia have been described previously, their relation with no-reflow is not clear.

PURPOSE

To evaluate relation of admission QRS duration with angiographic no-reflow, we studied 162 patients who underwent primary angioplasty.

METHODS

Twelve-lead electrocardiogram with a paper speed of 50 mm/s was recorded on admission and repeated after angioplasty. Patients were divided into reflow and no-reflow groups based on postangioplasty coronary thrombolysis in myocardial infarction flow grade.

RESULTS

Patients in the no-reflow group (26 patients) were older (P = .001) and had significantly longer pain-to-balloon interval (P = .007). The patients in the no-reflow group had significantly longer QRS duration on admission electrocardiogram compared with patients in the reflow group (interquartile range, 80-93 [median, 84] milliseconds vs 60-80 [median, 76] milliseconds, respectively; P < .001). After adjusting all variables, QRS duration on admission was found to be independently related to angiographic no-reflow (odds ratio, 1.07; 95% confidence interval, 1.02-1.12; P = .003).

CONCLUSION

QRS duration on admission may be valuable in predicting no-reflow.