Posterior myocardial infarction and complete right bundle- branch block

Atypical Presentations of Myocardial Infarction: A Systematic Review of Case Reports

There is a rising incidence of coronary artery diseases and myocardial infarction (MI). Mortality associated with acute MI (AMI) is directly linked to the time to receive treatment and missed diagnoses. Although health professionals are aware of typical AMI presentation, atypical MI is difficult to diagnose, which on the other hand, is likely to have an impact on morbidity and mortality. Therefore, it is prudent to know such atypical presentations, especially for emergency and primary care physicians. We aimed to systematically evaluate the clinical presentations of atypical MI and analyze them to characterize the common clinical presentations of atypical MI. We researched the PubMed database, did citation tracking, and performed Google Scholar advanced search to find the cases reported on the atypical presentation of MI published from January 2000 to September 2022. Articles of all languages were included; Google Translate was used to translate articles published in languages other than English. A total of 496 (56 PubMed articles, 340 citations from included PubMed articles, and 100 articles from Google Scholar advanced search) were screened; 52 case reports were evaluated, and their data were analyzed. Atypical presentations of myocardial infarction are vast; patients may have chest pain without typical characteristics of angina pain or may not have chest pain. No typical characterization could be done. Most patients were in their fifth decade or above of their life and commonly presented with pain and discomfort in the abdomen, head, and neck regions. Prodromal symptoms were consistent findings, and many patients had two to three comorbidities out of four common comorbidities, i.e., diabetes, hypertension, dyslipidemia, and substance abuse. A patient who is 50 years old or more, having comorbidities such as diabetes, hypertension, dyslipidemia, history of tobacco or marijuana usage, presenting with prodromal symptoms like shortness of breath, dizziness, fatigue, syncope, gastrointestinal discomfort or head/neck pain should be suspected for atypical MI.

ECG Changes in a Case of Posterior Myocardial Infarction in the Presence of Right Bundle Branch Block

A 70-year-old male with hypertension and diabetes presented to the emergency department with a 1-hour history of chest pain. Initial 12-lead ECG revealed a right bundle branch block (RBBB) and ST depression (STD) in V2-V4. The anterior STD prompted a 15-lead ECG in which there was no evidence of ST elevation (STE). With a positive troponin, cardiology was consulted and the patient was admitted as a high-risk non-ST-elevation myocardial infarction (NSTEMI). Subsequently, his chest pain returned without further ST changes, regardless the patient went for emergency coronary angiography, which found a complete occlusion of the left circumflex artery. Anterior STD is a normal finding in RBBB and posterior STEs in the posterior leads are not always present making the recognition of posterior STEMI difficult. This case highlights three findings in leads V1-V3 that are concerning for posterior ischemia in the context of chest pain and an RBBB: tall R waves, upright T waves, and marked STD > 2 mm. This should prompt serial 15-lead ECGs and prompt cardiology consultation.

Case report: Posterior myocardial infarction in presence of right bundle branch block: an old concept with new findings

Background

The diagnosis of acute ischaemic coronary syndromes in presence of an intra-ventricular conduction disturbance represents a clinical challenge. In the cardiac segmentation model the posterior wall is replaced by the basal inferior segment. However, in the clinical scenario of acute coronary syndrome the concept of posterior myocardial infarction (PMI) endures. The association of a PMI and right bundle branch block (RBBB) is a rare condition characterised by broad R waves and ventricular repolarization disorders in right precordial leads in both entities, which could lead to misinterpretation and delay in reperfusion therapy.

Case Summary

We describe a case report of a 74-year-old man with acute chest pain and an electrocardiogram with broad R waves, a 4 mm ST-segment downsloping (excessively discordant) in right precordial leads, RBBB, and ST-segment elevation in posterior leads. There was resolution of ST-segment downsloping in right precordial leads after percutaneous coronary intervention and stenting of the circumflex artery, with disturbance of the repolarization process only attributable to RBBB.

Discussion

Patients with acute chest pain with RBBB and a ST segment with an excessive downsloping (out of proportion of what is expected in isolated RBBB) suggest PMI with occlusion of the circumflex coronary artery.

Isolated Posterior Acute Myocardial Infarction Presenting to an Emergency Department: Diagnosis and Emergent Fibrinolytic Therapy

Objectives

Isolated posterior acute myocardial infarction (AMI) is rare and possibly underdiagnosed. The incidence of misdiagnosis in the emergency department (ED) is unknown. Delayed diagnosis may prevent timely treatment, particularly emergent fibrinolytic therapy. We describe the experience of an urban ED on this rare condition.

Methodology

A six years and seven months case series of isolated posterior AMI of initial presentation (as identified by inpatient discharge/death ICD-9-CM diagnosis code) was studied. Patients not admitted from the ED, those who developed isolated posterior AMI only after admission and/or those with concomitant ST segment elevation AMI involving other anatomical locations of the heart (e.g. inferior or lateral walls), were excluded.

Results

Eleven cases were included in the study. All the nine cases with electrocardiograms available for review demonstrated features consistent with isolated posterior AMI. Eight out of the eleven (72.7%) cases were correctly diagnosed as isolated posterior AMI in the ED. The other three cases were treated as non-ST elevation myocardial infarction (NSTEMI). Nevertheless, their lack of the typical symptoms of acute coronary syndrome and delayed presentation (more than 12 hours) precluded them from fibrinolytics. Three of the eleven cases received fibrinolytics (all streptokinase). All three cases survived to discharge and there were no haemorrhagic complications. None of the cases underwent emergent percutaneous coronary intervention.

Conclusion

The majority of cases with isolated posterior AMI (72.7%) were diagnosed in the ED. Although three cases were interpreted as NSTEMI, the use of fibrinolytic reperfusion therapy was not affected.