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A 56-year-old man comes to the emergency department because of chest pain and pressure he experienced an hour ago while shoveling snow. He has had recurrent bouts of this pain over the past year, and he says that it usually radiates to his jaw and left arm, and goes away when he sits down to rest. Today's episode lasted five minutes, he has come to the ED at the urging of his family. He has a 10-year history of hyperlipidemia and type 2 diabetes mellitus. Current medications include atorvastatin and metformin. His temperature is 37.1°C (98.8°F), pulse is 87/min, respirations are 19/min, and blood pressure is 130/85 mm Hg. Initial laboratory studies show a troponin I level of less than 0.01 ng/mL. Chest X-ray and ECG show no abnormalities. Which of the following is the most likely diagnosis?
Content Reviewers:Rishi Desai, MD, MPH
Angina comes from the latin angere, which means to strangle, and pectoris comes from pectus, meaning chest—so angina pectoris loosely translates to “strangling of the chest”, which actually makes a lot of sense, because angina pectoris is caused by reduced blood flow which causes ischemia to the heart muscle, or lack of oxygen to the heart, almost like the heart’s being strangled which causes terrible chest pain.
Stable angina or chronic angina is the most common type of angina and it usually happens when the patient has greater than or equal to 70% stenosis, meaning 70% of the artery is blocked by plaque buildup.
This small opening that blood flows through might be enough to supply the heart during rest, but if the body demands more blood and oxygen, like during exercise or stressful situations, the heart has to work harder, and therefore needs more blood and oxygen itself.
It’s during these time of exertion or emotional stress that people with stable angina have chest pain, since the blood flow isn’t meeting the metabolic demands of the heart muscle, or myocardium.
But the pain usually goes away with rest.
Other heart conditions that might lead to stable angina are ones that cause a thickened heart muscle wall, which would require more oxygen.
This increase in muscle size can be due to hypertrophic cardiomyopathy from a genetic cause, or as a result from the heart having to pump against higher pressures, as is the case in aortic stenosis, which is a narrowing of the aortic valve, or hypertension.
These larger, thicker heart muscles require more oxygen, and if the patients can’t meet increasing demands, they feel pain in the form of angina.
Whatever the case, the heart needs blood, and if we look at the heart wall, there’s three layers—the outermost layer, the epicardium, then the myocardium in the middle, and the endocardium inside the heart.
The coronary arteries start up in the epicardium, and then dive down and supply all the heart tissue.
If blood flow’s reduced or the myocardium is thicker, blood has a harder time reaching this deeper layer just under the endocardium, called the subendocardium.
Therefore the classic finding with angina is subendocardial ischemia, meaning less oxygen is reaching the region just under the endocardium.
This ischemia is thought to trigger release of adenosine, bradykinin, and other molecules that stimulate nerve fibers in the myocardium that result in the sensation of pain.
That chest pain is usually described as feeling like pressure or squeezing and it can radiate to the left arm, jaw, shoulders, and back, and sometimes is accompanied by shortness of breath and diaphoresis or sweating.
Usually the pain and symptoms last less than 10 minutes, generally 2 to 5 minutes, and subside after the exertion or stress is taken away, and therefore the heart muscle isn’t demanding as much blood.
Now, unlike stable angina which describes when patients have pain only during periods of exertion or stress, but not during rest, there is also unstable angina which is when patients have pain during exercise or stress as well as during rest—it never really goes away.
Unstable angina is usually caused by rupture of atherosclerotic plaque with thrombosis, meaning a blood clot forms on top of a mound of plaque.
Although the occlusion might not block the entire vessel, there is now even less room left for blood to flow by, and the heart tissue is starting to feel starved for oxygen even while pumping at a normal rate.
- "Robbins Basic Pathology" Elsevier (2017)
- "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
- "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
- "Pathogenesis of angina pectoris" (1982)
- "Unstable angina pectoris: Pathogenesis and management" Current Problems in Cardiology (1989)
- "Management of Chronic Stable Angina" Critical Care Nursing Clinics of North America (2017)