A 78-year-old vvoman is hospitalized due to acute myocardial infarction. The patient had been having intermittent chest pain for 3 days and came to the hospital when the pain became unremitting. She has type 2 diabetes mellitus, but her medical follov1-up has been poor. On the third day of hospitalization, the patient has sudden-onset shortness of breath due to pulmonary edema. Echocardiography confirms severe mitral
regurgitation. She is taken immediately to surgery, which reveals rupture of the posteromedial papillary muscle. This patient’s finding typically suggests compromised blood flow through which of the follovving coronary arteries?
- A . Conus branch
- b. Diagonal branch
- C. Left anterior descending
- D. Obtuse marginal
- E. Posterior descending
The mitral valve apparatus consists of the mitral valve annulus, anterior and posterior mitral leaflets, and chordae tendineae, which are tethered to the left ventricular wall via the anterolateral and posteromedial papillary muscles. Pathologic processes that disrupt any of these structures can lead to improper alignment of the mitral leaflets, resulting in mitral regurgitation and pulmonary edema.
The patient’s mitral regurgitation is the result of papillary muscle rupture, a life-threatening mechanical complication typically occurring 3-5 days following acute myocardial infarction. The anterolateral papillary muscle has a dual blood supply from the left anterior descending (LAD) and left circumflex arteries. In contrast, the posteromedial papillary muscle is supplied solely by the posterior descending artery, a branch of the right coronary artery (right dominant circulation) or left circumflex artery (left dominant circulation). Because blood flow to the posteromedial papillary muscle depends on a single artery, it is more likely to become ischemic and rupture following myocardial infarction.
(Choice A) The conus artery is an early branch of the proximal right coronary artery; it supplies the anterior area of the interventricular septum and conus of the pulmonary artery.
(Choice B) Diagonal arteries branch from the LAD artery and supply blood to the anterolateral walls of the left ventricle.
(Choice C) The LAD artery supplies the anterior l"lo thirds of the interventricular septum, anterior wall of the left ventricle, and anterolateral papillary muscle. Abrupt occlusion of the LAD rarely results in ischemic rupture of the anterolateral papillary muscle as this muscle also receives blood supply from the left circumflex artery.
(Choice D) The obtuse (left) marginal artery is a branch of the left circumflex artery and supplies the lateral wall of the left ventricle.