Diagnosis of myocardial infarction and ischemia in the setting of bundle branch block and cardiac pacing

Abstract

The diagnosis of myocardial infarction (MI) in the presence of left bundle branch block (LBBB) or during ventricular pacing (VP) is challenging because of inherent changes in the sequence of ventricular depolarization and repolarization associated with both conditions. Although LBBB and right ventricular (RV) pacing may both produce abnormalities in the ECG, it is often possible to diagnose an acute MI (AMI) or an old MI based on selected morphologic changes. Primary ST-segment changes scoring 3 points or greater according to the Sgarbossa criteria are highly predictive of an AMI in patients with LBBB or RV pacing. The modified Sgarbossa criteria are useful for the diagnosis of AMI in patients with LBBB; however, these criteria have not yet been studied in the setting of RV pacing. Although changes of the QRS complex are not particularly sensitive for the diagnosis of an old MI in the setting of LBBB or RV pacing, the qR complex and Cabrera sign are highly specific for the presence of an old infarct. Diagnosing AMI in the setting of biventricular (BiV) pacing is challenging. To date there is minimal evidence suggesting that the traditional electrocardiographic criteria for diagnosis of AMI in bundle branch block may be applicable to patients with BiV pacing and positive QRS complexes on their ECG in lead V1. This report is a careful review of the electrocardiographic criteria facilitating the diagnosis of acute and remote MI in patients with LBBB and/or VP.

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

“…The association of f(QRS-T) angle with larger scar tissue can be explained as follows: ischemic or infarcted myocardial zone is electrically inert resulting abnormal conduction occurs through infarct area due to regional cellular changes (Herweg, Marcus, & Barold, 2016 TA B L E 5 Univariate and multivariate analysis for determining the independent predictors of in-hospital mortality information about the postprocedural f(QRS-T) angle, we think that these findings should be supported by larger prospective studies.…”

“…When all of this results were evaluated, we can suggest that both widened baseline f(QRS‐T) and widened post‐procedural f(QRS‐T) angles in STEMI patients associated with extent of myocardial scar tissue irrespective of MI localization. The association of f(QRS‐T) angle with larger scar tissue can be explained as follows: ischemic or infarcted myocardial zone is electrically inert resulting abnormal conduction occurs through infarct area due to regional cellular changes (Herweg, Marcus, & Barold, ). This condition may manifest heterogeneity between depolarization and repolarization waveform to result in widened post‐procedural f(QRS‐T) angle on surface ECG.…”

Selective and nonselective His bundle pacing unmasks pathological Q waves on the electrocardiogram

“…In the current case, the His bundle could be paced both selectively (threshold of However, these markers are neither sensitive nor specific and not useful to assess the localization of myocardial infarction [2][3][4]. Of note, neither Cabrera's nor Chapman's sign were present in our patient during any type of pacing, while qR in I and QS in aVL observed during right ventricular pacing were non-diagnostic because of outflow tract/high septal pacing lead position [5].…”

Left bundle branch block as equivalent of ST-segment elevation myocardial infarction: when yes, when not?

“…Although Sgarbossa's criteria are an important advance, they have the limitation of their low sensitivity. In a meta-analysis, a general sensitivity of 20% and specificity of 96% were observed, for a Sgarbossa score higher than or equal to three 14,15 . However, the combination of the first two criteria (ST-segment concordant elevation in any lead and ST-segment concordant depression in V1-V3), contributes to sensitivity and specificity increase by 37.2 and 96.6%, respectively 16 .…”

“…1) are based on a scoring system where three or more points are required for AMI diagnosis in the presence of LBBB, typically known as weighted criteria. Criteria without this scoring system can be also used and, in this case, any of the three criteria is accepted, a modality known as unweighted, which is more sensitive but less specific 4,14 . These criteria largely contributed to solve multiple problems when facing an ECG with LBBB in patients with ischemic symptoms; however, the study had two important limitations, 1,4 and thus it is not surprising that the attempts to validate the electrocardiographic criteria have shown a useful specificity but poor sensitivity: -The study used creatine kinase MB (CK-MB) elevation as AMI outcome instead of using acute coronary occlusion angiographic evidence, which limits the sensitivity of the rule, since it combines STEMI and non-ST AMI in the definition of its outcome.…”