A 62-year-old Caucasian man comes to the emergency department (ED) and complains of crushing substernal chest pain. The pain started one hour ago while he was shoveling snow on his driveway. At the onset of his pain, he took nitroglycerin sublingually, but the pain did not get any better and he was taken to the ED by his son. He has a history of coronary artery disease, hypertension, hyperlipidemia, and osteoarthritis. He is on daily aspirin, metoprolol, lisinopril, atorvastatin, and naproxen as needed. In the ED, his electrocardiogram reveals a normal sinus rhythm with no acute ST-T wave changes. He is given morphine for his pain, started on nitroglycerin drip, and admitted to the telemetry floor. The next day, an adenosine thallium stress test reveals a moderate size reversible perfusion defect in the lateral wall of the left ventricle. Which of the following coronary vessels is most likely to have a significant occlusion?

Question

A 62-year-old Caucasian man comes to the emergency department (ED) and complains of crushing substernal chest pain.  The pain started one hour ago while he was shoveling snow on his driveway.  At the onset of his pain, he took nitroglycerin sublingually, but the pain did not get any better and he was taken to the ED by his son.  He has a history of coronary artery disease, hypertension, hyperlipidemia, and osteoarthritis.  He is on daily aspirin, metoprolol, lisinopril, atorvastatin, and naproxen as needed.  In the ED, his electrocardiogram reveals a normal sinus rhythm with no acute ST-T wave changes.  He is given morphine for his pain, started on nitroglycerin drip, and admitted to the telemetry floor.  The next day, an adenosine thallium stress test reveals a moderate size reversible perfusion defect in the lateral wall of the left ventricle.  Which of the following coronary vessels is most likely to have a significant occlusion?

Quizplus · Accepted Answer

Explanation: In all patients with known or suspected coronary artery disease, exercise or pharmacological stress testing with radionuclide myocardial perfusion imaging (thallium or technetium-99m) is useful for confirming the diagnoses and for risk stratification. The pharmacologic stress agents (adenosine and dipyridamole) act by producing coronary vasodilatation and increasing the coronary flow rate and velocity. In normal coronary vessels, the resulting vasodilation increases the blood flow; however, in areas with severe stenosis, there is already a compensatory microvascular dilatation at rest to maintain normal blood flow, so no further increase in the flow occurs. The resulting heterogenous blood flow due to the stenotic or occluded region is detected by radionuclide imaging studies as a perfusion defect. After establishing the presence of a defect, the next step is to localize the affected myocardial region in order to identify the culprit vessel. All coronary arteries supply a specific region of the ventricle. In this case, the patient's adenosine thallium stress test revealed a perfusion defect in the lateral wall of the left ventricle. The culprit vessel is most probably the left circumflex artery, which runs laterally in the left atrioventricular groove to supply the lateral and posterolateral parts of the left ventricle. (Choices B and C) The left main coronary artery arises from the left coronary ostium and branches off into the left anterior descending (LAD) artery and left circumflex artery. The LAD artery runs along the anterior interventricular groove and supplies the anterior wall of the left ventricle. Diagonal branches from the LAD artery also run downward to supply the anterolateral wall of the left ventricle. (Choice D) The right coronary artery runs in the right atrioventricular groove to supply the right ventricle and inferoposterior walls of the left ventricle. Educational Objective: The left circumflex coronary artery runs in the left atrioventricular groove to supply the lateral wall of the left ventricle.

A 62-Year-Old Caucasian Man Comes to the Emergency Department (ED) And