WBR0460
| Author | [[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Yazan Daaboul, M.D.)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Anatomy |
| Sub Category | SubCategory::Cardiology |
| Prompt | [[Prompt::A 56-year-old man presents to the emergency department (ED) with complaints of chest pain and shortness of breath. On arrival, and ECG demonstrates ST-segment elevation in 2 consecutive leads, and blood work-up is remarkable for elevated serum troponin concentration. The diagnosis of STEMI is made, and the patient is transferred to the cardiac catheterization lab for an emergent percutaneous coronary intervention (PCI). Cardiac catheterization reveals a total occlusion of the right coronary artery (RCA). Which of the following anatomical locations of the heart is most likely affected as a result of this patient’s STEMI?]] |
| Answer A | AnswerA::Anterior interventricular septum |
| Answer A Explanation | AnswerAExp::The LAD usually provides the blood supply to the anterior interventricular septum. |
| Answer B | AnswerB::Left atrium |
| Answer B Explanation | AnswerBExp::The left main coronary artery usually provides the blood supply to the left atrium. |
| Answer C | AnswerC::Anterolateral papillary muscle |
| Answer C Explanation | AnswerCExp::The anterior papillary muscle most commonly receives a dual blood supply from the LAD and the LCx. |
| Answer D | AnswerD::Sinoatrial (SA) node |
| Answer D Explanation | AnswerDExp::The RCA usually provides the blood supply to the SA node. |
| Answer E | AnswerE::Apex |
| Answer E Explanation | AnswerEExp::The apex of the heart receives a dual blood supply from the LAD and the PDA. The LDA provides the majority of the blood supply to the apex. |
| Right Answer | RightAnswer::D |
| Explanation | [[Explanation::There are two main epicardial arteries that supply the myocardium: the left coronary artery (LCA) and the right coronary artery (RCA). The heart is supplied by these two arteries and their branches in such a way that the LCA supplies mainly the left ventricle, whereas the RCA supplies the right atrium and ventricle, the SA node, the inferior wall, posterior interventricular septum, and posteromedial papillary muscle in approximately 85 % of the cases.
The RCA originates above the right cusp of the aortic valve. It travels down the right atrioventricular groove, towards the crux of the heart. In addition to supplying blood to the right ventricle (RV), the RCA supplies 25% to 35% of the left ventricle (LV). The LCA normally arises from the aortic sinus above the left cusp of the aortic valve and supplies the majority of the blood flow to the left ventricle. In fact, the LCA supplies the posterolateral side of the LV as well as the anterior part of the LV, which includes the anterolateral myocardium, the apex, the anterior interventricular septum, and the anterolateral papillary muscle. The origin of the LCA is called the left main coronary artery, and it bifurcates into the following two main branches: Left anterior descending (LAD) artery and Left circumflex artery (LCx). The dominance of coronary circulation is determined by the type of arteries that supply the posterior and inferior wall of the left ventricle. The artery that supplies the posterior descending artery (PDA) and the posterolateral artery (PLA) determines the coronary dominance. Approximately 60 - 70% of the general population are right-dominant, 25% are co-dominant, and 15% are left-dominant. |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Coronary artery, WBRKeyword::Sinoatrial node, WBRKeyword::SA, WBRKeyword::blood supply, WBRKeyword::cardiovascular system, WBRKeyword::cardiology |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |