Evaluación de los algoritmos de Smith para el diagnóstico de infarto agudo de miocardio en presencia de bloqueo de rama izquierda del haz de His

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.

New Electrocardiographic Algorithm for the Diagnosis of Acute Myocardial Infarction in Patients With Left Bundle Branch Block

Background

Current electrocardiographic algorithms lack sensitivity to diagnose acute myocardial infarction (AMI) in the presence of left bundle branch block.

Methods and Results

A multicenter retrospective cohort study including consecutive patients with suspected AMI and left bundle branch block, referred for primary percutaneous coronary intervention between 2009 and 2018. Pre‐2015 patients formed the derivation cohort (n=163, 61 with AMI); patients between 2015 and 2018 formed the validation cohort (n=107, 40 with AMI). A control group of patients without suspected AMI was also studied (n=214). Different electrocardiographic criteria were tested. A total of 484 patients were studied. A new electrocardiographic algorithm (BARCELONA algorithm) was derived and validated. The algorithm is positive in the presence of ST deviation ≥1 mm (0.1 mV) concordant with QRS polarity, in any lead, or ST deviation ≥1 mm (0.1 mV) discordant with the QRS, in leads with max (R|S) voltage (the voltage of the largest deflection of the QRS, ie, R or S wave) ≤6 mm (0.6 mV). In both the derivation and the validation cohort, the BARCELONA algorithm achieved the highest sensitivity (93%–95%), negative predictive value (96%–97%), efficiency (91%–94%) and area under the receiver operating characteristic curve (0.92–0.93), significantly higher than previous electrocardiographic rules (P<0.01); the specificity was good in both groups (89%–94%) as well as the control group (90%).

Conclusions

In patients with left bundle branch block referred for primary percutaneous coronary intervention, the BARCELONA algorithm was specific and highly sensitive for the diagnosis of AMI, leading to a diagnostic accuracy comparable to that obtained by ECG in patients without left bundle branch block.

Validation of the diagnosis and triage algorithm for acute myocardial infarction in the setting of left bundle branch block

BACKGROUND

Detecting acute ST-segment elevation myocardial infarction (STEMI) in the setting of left bundle branch block (LBBB) remains a challenge to clinicians. Several diagnostic and triage algorithms have been proposed to accurately identify LBBB patients with an acute culprit vessel. We aimed to validate the algorithm proposed by Cai et al., which uses patients' hemodynamic status and the modified Sgarbossa electrocardiography criteria to guide reperfusion therapy.

METHODS

This retrospective study was performed with a chart review in emergency departments (EDs) of 2 medical centers, 2 regional hospitals, and 1 local hospital. From January 2010 to December 2014, 2432 consecutive patients were diagnosed as having STEMI in the ED, including 65 patients with LBBB (2.6%).

RESULTS

The patients with LBBB were older and more frequently presented with acute pulmonary edema (58.5% vs 22.1%, p < 0.001), cardiogenic shock (16.9% vs 6.3% p = 0.006), and VT/VF episodes (7.7% vs 2.2%, p = 0.034) and had a higher 30-day mortality rate (20.0% vs 10.4% p = 0.032) than those without LBBB. We then tested the algorithm proposed by Cai et al. and noted a sensitivity of 93.8% in identifying a culprit lesion.

CONCLUSIONS

The inconsistency of the guideline recommendations reflects the uncertainty of diagnostic and therapeutic strategies and the pressing need for tools to accurately identify the true acute myocardial infarction in patients presenting with chest pain and LBBB. The algorithm proposed by Cai et al. had good sensitivity and would allow emergency physicians to implement the timely treatment protocol for this high-risk population.

Atypical Electrocardiographic Presentations in Need of Primary Percutaneous Coronary Intervention

Early initiation of reperfusion therapy remains the cornerstone of successful management for ST-elevation myocardial infarction (STEMI). Rapid restoration of coronary blood flow relies on prompt recognition of the typical ST-segment elevation on a 12-lead electrocardiogram (ECG)-a surrogate for coronary occlusion or critical stenosis-allowing timely activation of the STEMI protocol cascade, with a major positive impact in mortality and clinical outcomes. However, atypical, very high risk ECG patterns-known as "STEMI equivalents"-are present in 10% to 25% of patients with ongoing myocardial ischemia in need of urgent primary percutaneous coronary intervention. Though briefly mentioned in the current recommendations, structured clinical data on those specific ECG presentations are lacking. By thoroughly searching MEDLINE and EMBASE we conducted a structured review of non-STEMI, albeit very high risk, ECG patterns of acute coronary syndrome, often associated with coronary occlusion or critical stenosis. After screening 997 studies, we identified the following distinct "STEMI equivalent" ECG patterns: Wellens' syndrome, de Winter sign, hyperacute T waves, left bundle branch block-including paced rhythm-and right bundle branch block. For each pattern, a brief summary of the existing evidence, together with the sensitivity, specificity, and positive predictive value-whenever available-are presented. In conclusion, prompt recognition of "STEMI equivalent" ECG patterns is crucial for every physician or paramedic dealing with acute coronary syndrome patients in the emergency department or the prehospital setting, as misinterpretation of those high risk presentations can lead to reperfusion delays and worse outcomes.