Physiology Antero-inferior Myocardial Infarction

Question

Antero-inferior Myocardial Infarction

A 52-year-old man presented with the chief complaints of fatigue and difficulty breathing. During the history the patient reported that he had suffered some chest pain, but attributed it to indigestion. Auscultation detected fluid in the lungs and a harsh murmur was present throughout systole. An electrocardiogram (EKG) showed signs of an antero-inferior myocardial infarction and a two-dimensional echocardiogram revealed a ruptured papillary muscle in the left ventricle. The patient was diagnosed with acute mitral regurgitation secondary to a myocardial infarction. He successfully underwent surgery for replacement of the mitral valve.

What is the anatomy of the mitral valve apparatus?

Which artery was involved in producing the infarct of the papillary muscle?

Why did auscultation detect fluid in the lungs?

Answer 1

Anatomy of mitral valve: The valve is composed of leaflets that are connected to chordae tendineae on the ventricular side. These connect to medial and lateral papillary muscles on the walls of the left ventricle.

Artery of infarct: Since this is an anterior-inferior MI that affected blood supply to the mitral papillary muscles, it must have occurred in a branch of the LAD, such as the diagonal branch.

Fluid in the lungs: This is most likely a direct result of mitral regurgitation, which leads to back-flow of blood into the pulmonary system and increased hydro-static pressure, which causes fluid to seep into the interstitium.