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Chapter 8: The Cardiovascular System

A 69-year-old obese woman with hypertension and hyperlipidemia suffered a large transmural acute anterior wall myocardial infarct that resulted several days later in papillary muscle rupture and an incompetent mitral valve.

Which major coronary artery was occluded?

A. Right coronary artery

B. Left circumflex coronary artery

C. Left anterior descending coronary artery

D. Posterior papillary coronary artery

Answer: C

Explanation: The left anterior descending coronary artery supplies blood flow to the anterior wall of the left ventricle and the anterior two-thirds of the intraventricular septum. In most people, the right coronary artery is dominant. In these people the right coronary artery supplies blood flow to the right ventricle, the posterior wall of the left ventricle and the posterior third of the intraventricular septum, and the left circumflex coronary artery supplies blood flow to the lateral wall of the left ventricle. In people with a dominant left circumflex coronary artery, this artery carries blood flow to the posterior third of the intraventricular septum and a larger portion of the posterior left ventricular wall.

A 69-year-old obese woman with hypertension and hyperlipidemia suffered a large transmural acute anterior wall myocardial infarct that resulted several days later in papillary muscle rupture and an incompetent mitral valve.

What type of heart failure will eventually occur in this patient do the resulting significant loss of pump function?

A. Right heart only

B. Left heart only

C. Right heart first, then left heart too

D. Left heart first, then right heart too

Answer: D

Explanation: Infarction of a large portion of the anterior wall of the left ventricle will result initially in poor left ventricle pump function and left heart failure. In this case, the incompetent mitral valve caused by the papillary muscle rupture exacerbates the loss of left ventricle pump function due to blood regurgitation across the mitral valve. Right ventricular failure is not initially observed because there is no infarction of the right ventricle. However, with time the failure of the left ventricle will lead to backup of blood into the lungs and eventually into the right ventricle, leading also to right heart failure.

A 69-year-old obese woman with hypertension and hyperlipidemia suffered a large transmural acute anterior wall myocardial infarct that resulted several days later in papillary muscle rupture and an incompetent mitral valve.

What is the event that most likely caused the myocardial infarction?

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