AssessmentsCoronary artery disease: Pathology review
USMLE® Step 1 style questions USMLE
A 60-year-old man comes to the emergency department due to 20 minutes of crushing chest pain and diaphoresis that began suddenly while watching television. According to the patient’s partner, lately he has had occasional chest pain occurring during rest that resolved after a few minutes. Medical history is significant for hyperlipidemia, hypertension, and diabetes mellitus. The patient has not been compliant with the medications. The patient’s temperature is 37.0°C (98.6° F), pulse is 80/min, respirations are 20/min, and blood pressure is 135/85 mm Hg. The patient appears to be in acute distress and in pain. Cardiac examination shows an additional sound just prior to S1 on auscultation. ECG demonstrates ST segment elevation in leads V1-V5. While being prepared for percutaneous coronary intervention, the patient suddenly dies. Following this patient’s death, an autopsy is performed to better understand the underlying pathology. At the time of this patient's death, which of the following sets of findings is most likely to be seen in the anterior wall of the myocardium?
Content Reviewers:Yifan Xiao, MD
Contributors:Kaylee Neff, Jake Ryan, Antonia Syrnioti, MD, Ahmad El-Gammal, MBBS, Robyn Hughes, MScBMC, Samantha McBundy, MFA, CMI
In an urban emergency department, 3 people came in for chest pain. The first is Anish, a 54 year old man with a known history of hypertension, hyperlipidemia, and 25-pack year smoking. He’s complaining of shortness of breath, and squeezing, retrosternal chest pain that radiates to his neck, jaw and left arm. He’s been having these episodes but they only come after riding his bicycle for at least 20 minutes, and is relieved once he rests. Investigations reveal a normal ECG and normal troponin levels. Next, is Erica, a 66-year old woman with a history of diabetes mellitus who complains of sudden-onset shortness of breath, fatigue and dizziness, but no chest pain. An ECG reveals ST-segment depression, and troponin levels are elevated. Finally, There’s Tyrion, a 45-year old man, with a known history of hypertension, diabetes, and hyperlipidemia. He complains of epigastric abdominal pain at rest, shortness of breath, sweating and lightheadedness for the past 30 minutes. His blood pressure is 80/60, and his heart is 45 beats per minute. An ECG reveals ST-segment elevation in leads II, III and aVF.
All three have coronary artery disease which is defined as an imbalance between myocardial oxygen demand and supply from the coronary arteries. Reduced oxygen supply to the heart is defined myocardial ischemia, which results in a severely reduced ability of the heart muscle ability to contract. If this is prolonged, it can go on to cause myocardial infarction, otherwise known as heart attack, which refers to death of heart muscle. Now, coronary artery disease is usually caused by atherosclerosis of the coronary arteries. Risk factors for atherosclerosis can be divided into non-modifiable ones, which include age, with men greater than 45 years and women greater than 55 years being at risk, and family history of coronary artery disease, and modifiable ones, like lipid abnormalities including elevated LDL or low HDL levels, as well as hypertension, diabetes mellitus and smoking. Coronary artery disease can present in many ways, including stable angina, Prinzmetal angina, acute coronary syndrome - which includes unstable angina, non-ST-segment elevation myocardial infarction, or NSTEMI, ST-segment elevation myocardial infarction, or STEMI, chronic ischemic heart disease, and sudden cardiac death.
Now, aside from atherosclerosis, there are other less common causes of coronary artery disease, such as coronary artery embolus vasculitis and vasospasm. In a coronary embolism, pieces of a clot from another site break off and can travel into a coronary artery, occluding it. Risk factors for a coronary embolism include atrial fibrillation, infective endocarditis, a left atrial or ventricular thrombus or in individuals undergoing cardiac catheterization. As for vasculitis, coronary artery disease in young children should prompt you to consider Kawasaki disease, a medium-vessel vasculitis that classically causes a coronary artery aneurysm. Also, other vasculitides like polyarteritis nodosa can also cause coronary artery disease. Now, coronary artery vasospasm, meaning the smooth muscles around the arteries constrict extremely tightly, may also reduce blood flow and result in coronary artery disease. Then, another cause of coronary artery disease is aortic valve stenosis. See, the right and left main coronary arteries branch off the base of the aorta, and so in aortic stenosis, not enough blood gets through the aorta and into the coronaries, resulting in myocardial ischemia. Also, any cause of concentric ventricular hypertrophy, such as aortic valve stenosis, hypertension, or hypertrophic cardiomyopathy may result in coronary artery disease, because you essentially have more heart muscle to supply.
Now let’s take a look at the presentations of coronary artery disease, starting with stable angina! This occurs secondary to myocardial ischemia, caused by a fixed atherosclerotic plaque occluding more than 75 percent of the coronary artery lumen. What you must remember here is that this results in reversible cell injury. An infarction, on the other hand, is when there’s irreversible cell injury or cell death.Now, stable angina manifests as a deep, poorly localized, squeezing, crushing or suffocating retrosternal pain that may radiate to the arm, jaw or neck. Lots of adjectives. It’s often accompanied by other symptoms, such as shortness of breath, nausea, vomiting, diaphoresis, fatigue or dizziness. A high yiel