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

Abstract

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.

Infarto agudo de miocardio posterior aislado: el responsable de cambios sutiles en el electrocardiograma

“…On the other hand, since 1950 the Mexican Cardiology School has referred the fact that it is an isolated wall 8 and this nomenclature continues to be in the current guidelines of the European Society of Cardiology in 2017 and the American College of Cardiology Committee and the Joint Cardiology Clinical Practice Guidelines/American Heart Association in 2021 [9][10][11][12] .…”

“…The 12-lead EKG does not directly orient towards the posterior wall, therefore, none of the leads reveals the classic signs of posterior acute myocardial infarction (AMI), such as ST-segment elevation 8 , which leads to errors or delays in diagnosis 2 . However, it can be suspected when the opposite leads to the posterior wall (V1-V3) manifest "mirror" images characterized by a higher R wave voltage, ST-segment depression, and symmetrical, vertical, acuminate T wave in V1-V2; these changes can be predictive of PMI 8,9 .…”

“…In transmural posterior infarction, reciprocal changes will be observed in the leads of the anteroseptal section of the heart, which correspond to the loss of electrical force in a dorsal direction 13 . In addition to the horizontal depression of the ST segment in V1, V2, and V3 on the 12-lead EKG, there are other changes that should alert the clinician to the presence of posterior infarction, including the prominent R wave that constitutes the electrical representation of ventrally deflected electrical forces due to posterior necrosis 13 , prominent T wave, the combination of ST segment depression with a prominent positive T wave, coexistence of inferior or lateral infarction, and R/S wave ratio > 1, these latter criteria only being observed in V2 9,14 . The presence of any of these findings should be complemented by obtaining the electrocardiographic record of posterior leads V7, V8, V9, where ST-segment elevation ≥ 0.5 mm in two of these leads would be conclusive with the diagnosis of posterior infarction 13 .…”

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

“…In addition, typical RBBB is manifested by discordant T-wave inversions in V1-V3. In the ECGs presented, upright T waves in the context of tall R waves in the right precordial leads are highly suggestive of posterior MI [ 2 , 3 ]. Further, there is marked STD (>2 mm) in leads V2-V3, out of proportion to what is typically observed in RBBB.…”

“…Further, there is marked STD (>2 mm) in leads V2-V3, out of proportion to what is typically observed in RBBB. In the setting of chest pain, this should prompt the clinician to consider posterior ischemia [ 2 , 3 ].…”