AMI in (bi)ventricular pacing - do not discard the ECG

BACKGROUND

There is a growing number of patients with ventricular paced rhythm, who present to the emergency department with chest pain. The diagnosis of ST-segment elevation myocardial infarction (STEMI) and subsequent percutaneous coronary intervention (PCI) is often postponed, as the 12 leads-electrocardiogram (ECG) is discarded as not interpretable. There is a growing body of literature that suggests that Smith-modified Sgarbossa criteria can be applied for the diagnosis of STEMI in patients with paced rhythms. These criteria were originally developed for the interpretation of ECGs in patients with a left bundle branch block (LBBB) and chest pain, but have been expanded to paced ECGs.

METHODOLOGY

We present three case reports with chest pain and right ventricular or biventricular pacing.

FINDINGS

In all three cases, the Smith-modified Sgarbossa was positive and the diagnosis of STEMI could have been made early on.

IMPLICATIONS

It remains important to look for ST-segment deviations and to compare the symptomatic ECG with previous asymptomatic ECGs. As the number of patients with potential acute myocardial infarction (AMI) and paced rhythms is likely to rise in the future, these criteria should be known to emergency physicians and cardiologists.

Diagnosis of Occlusion Myocardial Infarction in Patients with Left Bundle Branch Block and Paced Rhythms

PURPOSE OF REVIEW

A number of criteria have been developed to aid with the diagnosis of occlusion myocardial infarction (OMI) in patients with left bundle branch block (LBBB) and ventricular paced rhythms (VPR). The current guidelines do not provide clear preference for any specific ECG criteria in LBBB and paced rhythm patients.

RECENT FINDINGS

This review delineates the difficulties of electrocardiographic diagnosis of OMI in both LBBB and VPR patients. We describe the original Sgarbossa and the newer criteria and their diagnostic performances. We highlight the expected changes of newer pacing modalities and how they may interfere with the electrocardiographic diagnosis of OMI. We recommend utilizing the Cai et al. algorithm, which combines clinical assessment with the Smith Modified Sgarbossa ECG criteria, for both LBBB and right ventricular pacing patients with suspected OMI. There is limited data concerning ECG changes of OMI in patients with the newer pacing modalities, such as biventricular, His-bundle, or left bundle branch pacing.

Anterior wall ST-elevation myocardial infarction in biventricular paced rhythm

There is a lack of evidence on electrocardiographic criteria for ST-elevation myocardial infarction (STEMI) in patients with biventricular paced rhythm. In all previous case reports of STEMI in biventricular paced rhythm, concordant ST-elevations and/or discordant ST-elevations >5 mm were present. This report describes the case of a patient with anterior STEMI and discordant ST-elevations of less than 5 mm during biventricular stimulation with epicardial left ventricular lead and highlights the importance of comparing the electrocardiogram to previous recordings when STEMI is suspected.

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

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.

Difficult ECGs in STEMI: lessons learned from serial sampling of pre- and in-hospital ECGs

Prehospital interpretation of electrocardiograms (ECGs) is crucial to ensure early diagnosis and optimal treatment of patients with ST elevation myocardial infarction (STEMI). Recognition of ST-segment elevations (STE) by qualified personnel in the prehospital phase has successfully reduced the delay from the first medical contact to reperfusion. A few other ECG patterns without true STE, referred to as "STEMI equivalents", bear the same prognostic significance, reflect imminent or ongoing transmural ischemia, but are less easily identified. Hyperacute T waves, de Winter ST-T complex, Wellens' syndrome, and posterior STEMI, as well as myocardial infarction in the presence of left bundle branch block, paced rhythm or left ventricular hypertrophy, among others are diagnostic challenges. This article reviews some critical examples of ischemic ECG patterns that may be ephemeral, misinterpreted by medical staff or not identified by automated ECG algorithms, and it emphasizes the importance of serial ECG acquisition.