Ischemic QRS prolongation as a biomarker of myocardial injury in STEMI patients.

BACKGROUND: Patients with acute coronary occlusion (ACO) may not only have ischemia-related ST-segment changes but also changes in the QRS complex. It has recently been shown in dogs that a greater ischemic QRS prolongation (IQP) during ACO is related to lower collateral flow. This suggests that greater IQP could indicate more severe ischemia and thereby more rapid infarct development. Therefore, the purpose was to evaluate the relationship between IQP and measures of myocardial injury in patients presenting with acute ST-elevation myocardial infarction (STEMI). METHODS: Seventy-seven patients with first-time STEMI were retrospectively included from the recently published SOCCER trial. All patients underwent a cardiac magnetic resonance (CMR) examination 2-6 days after the acute event. Infarct size (IS), myocardium at risk (MaR), and myocardial salvage index (MSI) were assessed and related to IQP. IQP measures assessed were; computer-generated QRS duration, QRS duration at maximum ST deviation, absolute IQP and relative IQP, all derived from a pre-PCI, 12-lead ECG. RESULTS: Median absolute IQP was 10 ms (range 0-115 ms). There were no statistically significant correlations between measures of IQP and any of the CMR measures of myocardial injury (absolute IQP vs IS, r = 0.03, p = 0.80; MaR, r = -0.01, p = 0.89; MSI, r = -0.05, p = 0.68). CONCLUSIONS: Unlike previous experimental studies, the IQP was limited in patients presenting at the emergency room with first-time STEMI and no correlation was found between IQP and CMR variables of myocardial injury in these patients. Therefore, IQP does not seem to be a suitable biomarker for triaging patients in this clinical context.

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.

A 12-lead ECG-method for quantifying ischemia-induced QRS prolongation to estimate the severity of the acute myocardial event.

INTRODUCTION: Studies have shown terminal QRS distortion and resultant QRS prolongation during ischemia to be a sign of low cardiac protection and thus a faster rate of myocardial cell death. A recent study introduced a single lead method to quantify the severity of ischemia by estimating QRS prolongation. This paper introduces a 12-lead method that, in contrast to the previous method, does not require access to a prior ECG. METHODS: QRS duration was estimated in the lead that showed the maximal ST deviation according to a novel method. The degree of prolongation was determined by subtracting the measured QRS duration in the lead that showed the least ST deviation. RESULTS: The method is demonstrated in examples of acute occlusion in two of the major coronary arteries. CONCLUSION: This paper presents a 12-lead method to quantify the severity of ischemia, by measuring QRS prolongation, without requiring comparison with a previous ECG.

Ischemic QRS prolongation as a biomarker of severe myocardial ischemia.

BACKGROUND: Previous studies have shown that QRS prolongation is a sign of depressed collateral flow and increased rate of myocardial cell death during coronary occlusion. The aims of this study were to evaluate ischemic QRS prolongation as a biomarker of severe ischemia by establishing the relationship between prolongation and collateral flow experimentally in a dog model, and test if the same pattern of ischemic QRS prolongation occurs in man. METHODS: Degree of ischemic QRS prolongation was measured using a novel method in dogs (n=23) and patients (n=52) during coronary occlusion for 5min. Collateral arterial flow was assessed in the dogs. RESULTS: There was a significant correlation between QRS prolongation and collateral flow in dogs (r=0.61, p=0.008). Magnitude and temporal evolution of prolongation during ischemia were similar for dogs and humans (p=0.202 and p=0.911). CONCLUSION: Quantification of ischemic QRS prolongation could potentially be used as a biomarker for severe myocardial ischemia.

Specificity for each of the 46 criteria of the Selvester QRS score for electrocardiographic myocardial scar sizing in left bundle branch block.

BACKGROUND: The Selvester QRS score consists of a set of electrocardiographic criteria designed to identify, quantify and localize scar in the left ventricle using the morphology of the QRS complex. These criteria were updated in 2009 to expand their use to patients with underlying conduction abnormalities, but these versions have thus far only been validated in small and carefully selected populations. AIM: To determine the specificity for each of the criteria of the left bundle branch block (LBBB) modified Selvester QRS Score (LB-SS) in a population with strict LBBB and no myocardial scar as verified by cardiovascular magnetic resonance imaging with late gadolinium enhancement (CMR-LGE). METHODS: We identified ninety-nine patients with LBBB without scar on CMR-LGE, who underwent a clinically indicated CMR scan at three different centers. The ECG recording date was any time prior to or <30days after the CMR scan. The LB-SS was applied and specificity for detection of scar in each of the 46 separate criteria was determined. RESULTS: The specificity ranged between 41% and 100% for the 46 criteria of LB-SS and 27/46 (59%) met ≥95% specificity. The mean±SD specificity was 90%±14%. CONCLUSION: Several of the criteria in the LB-SS lack adequate specificity. Elimination or modification of these nonspecific QRS morphology criteria may improve the specificity of the overall LB-SS.

Prevalence of manual Strauss LBBB criteria in patients diagnosed with the automated Glasgow LBBB criteria.

INTRODUCTION: About one-third of patients undergoing cardiac resynchronization therapy because of left bundle branch block (LBBB) and heart failure do not improve. Strauss et al. have developed strict criteria to more accurately define complete LBBB in this patient group. The aim of this study was to investigate the prevalence of the manual application of the Strauss criteria for LBBB (QRS ≥ 140 ms in men, ≥ 130 ms in women, along with mid-QRS notching/slurring) in consecutive patients who have been diagnosed with LBBB by the automated Glasgow criteria (QRS ≥ 120 ms). METHOD: In 158 consecutive patients (78 females) diagnosed with LBBB according to the automated Glasgow criteria, the manual Strauss criteria were applied. RESULTS & CONCLUSION: A majority of patients (87%) diagnosed with LBBB using the Glasgow criteria were positive for the Strauss criteria. In 70% (13/20) of the cases of disagreement the reason for disagreement was short QRS duration.