Focus on CAD/ACS Diagnoses

By Laura Brasseur

SAN DIEGO—"Evaluation of chest pain is really all about not missing CAD [coronary artery disease], and in particular not missing things that could be ACS [acute coronary syndrome], and calling them something else and sending the patient home," said Nora Goldschlager, MD, professor of medicine, University of California, San Francisco, during the recent meeting of the American College of Physicians.

Nora Goldschlager, MD

That patient, whose chest pain was misdiagnosed, "then has a non–ST-segment elevation or sudden death in the parking lot," Dr Goldschlager warns. And this happens often, even though "rule out CAD" is on your list, and ACS perhaps at the top of that list of diagnoses to rule out in any patient complaining of chest pain. "The list is pretty inclusive in terms of things we see," she says. "There are no zebras here; they are all horses."

The differential diagnosis of chest pain is broken into 3 main etiologies: syndromes that are not caused by myocardial ischemia; ischemia that is not caused by CAD; and ischemic chest pain syndromes. Recognizing common pitfalls in the diagnosis of chest pain can help avoid unnecessary treatments and may prevent unnecessary death.

Chest Pain Not Caused by Myocardial Ischemia

Pericarditis. This condition is very different from myocardial ischemia. Pericarditis is often associated with a trigger, such as viral illness, a bypass done 2 weeks earlier, or pneumonia. It can also be idiopathic. Some features of pericarditis are not anginal, even though they may be better perceived during effort, because of its pleuritic component. Patients typically have no history of angina. Pericarditis is not an effort-associated syndrome in the same way that angina is, unless there is pleuropericarditis. For many patients, the only complaint is left-shoulder pain. "If there is unremitting left-shoulder pain, always make sure that you have listened for and excluded a pericardial friction rub," Dr Goldschlager says. Also carefully examine the 12-lead electrocardiogram (ECG).

Aortic dissection. "These are the sickest patients you may see in your practice," she says. Their pain is a "12" on a scale of 1 to 10, and it migrates, depending on where the dissection occurred. Many patients also have hypertension. Aortic dissection should also be suspected in pregnant women.

GI disorders. The most common conditions on the "rule out CAD" list are gastroesophageal reflux disease (GERD), esophageal spasm, esophageal rupture, and peptic ulcer disease. Esophageal pain tends to last hours, typically does not radiate (although it can), and tends to be nonexertional. The history will reveal that the pain is meal-related and is relieved with antacids. Most patients have other gastrointestinal (GI) complaints. If you have any doubt about the diagnosis, a workup for CAD is needed. In esophageal rupture, the patient is usually acutely ill and is not improving; a chest x-ray will reveal findings suggestive of rupture. Esophageal spasm can pre-sent exactly like angina, with burning pain that radiates to the throat, back, or intrascapular region. "What it doesn't tend to do," Dr Goldschlager says, "is go to the jaw and the teeth, which angina can and does do."

Other syndromes. Musculoskeletal conditions, such as cervical spine disease, can also present with chest pain. You can often reach the diagnosis by asking the patient what he was doing when he developed the chest pain. Other conditions to consider in the differential diagnosis are pulmonary embolism and pneumomediastinum.

Ischemia Not Caused by CAD

Aortic valve disease. Chest pain can be associated with aortic valve disease, especially stenosis, and obstructive or nonobstructive hypertrophic cardiomyopathy. Dyspnea usually accompanies the chest pain in these patients. Syncope is another common finding. These patients have left ventricular (LV) hypertrophy and demand ischemia. The subendocardium is working hard to develop the tension and pressure needed to open the aortic valve. But because of the transmyocardial coronary artery blood flow gradient, epicardial perfusion is greater than subendocardial perfusion. As a result, the subendocardium has the least amount of coronary flow despite performing the greatest amount of work.

Dilated cardiomyopathy. Chest pain in patients with nonischemic dilated cardiomyopathy can be very similar to ischemia-related chest pain. But these individuals will have normal coronary arteries on angiography. "This is one of the reasons that diuretic therapy is used in heart failure patients—to try to shrink the intracavitary size so that less myocardial oxygen consumption is needed to perform the activities of daily living," Dr Goldschlager said.

Tachycardia. This generally occurs in patients with fibrillations, she says, who do not have good heart rate control, especially if they are hypertensive. A useful clinical indicator is the "double product" (ie, heart rate "*" systolic blood pressure [BP]). The lower the double product at which the patient gets anginal pain, the more tenuous the coronary artery circulation. The higher the double product at which the patient gets symptoms, the more likely it represents demand ischemia.

Other ischemic syndromes without CAD are:

• Coronary artery embolism (unusual today)
• Syndrome X, common in women, characterized by an abnormal treadmill exercise test and normal coronary arteries on angiography
• Coronary artery dissection, an unusual condition that most often occurs in cocaine users
• Coronary arteritis can occur in any of the vasculitides; patients generally present with their vasculitis before their anginal-type chest pain syndrome
• Takotsubo cardiomyopathy, a poorly understood condition that appears to be related to stress, characterized by reversible LV dysfunction; symptoms similar to acute myocardial infarction (MI) but with normal coronary arteries; symptoms resolve within hours, and the ventricle returns to normal within days to weeks.

In general, when you see ischemia on the ECG, you must investigate whether it is demand ischemia, which you "can fix by fixing the heart rate and the BP," she says.

Ischemic Chest Pain Syndromes

Stable-effort angina. The same amount of work is required to bring on the chest pain in stable-effort angina, and the response to rest and to sublingual nitroglycerin is the same now as it was in the past year or 5 to 10 years. "You have a diagnosis," Dr Goldschlager says. "You don't need to do anything else—no percutaneous intervention, no catheterization, not even a consultation, unless there's something unusual about the patient's story or physical exam."

Unstable angina. Patients with unstable angina can be divided into risk categories according to clinical and ECG findings (Table, online). Admit high- and intermediate-risk patients to the hospital; as for low-risk patients, it depends on hospital policy.

ST-segment/non–ST-segment elevation MI. If the diagnosis is possible but cannot be confirmed with ECG or with cardiac markers, observe the patient. If she is fine, and her cardiac troponin levels are normal, she can be sent home. If she has recurrent chest pain, or her cardiac markers are positive, hospitalize her and order a workup for an ACS.

Common Pitfalls

Burning vs pain. Patients with myocardial ischemia often describe their angina not as pain but as a burning, which can lead the physician to think "gut." Since the pain of GERD can be retrosternal, the differential diagnosis can be challenging. The pain of myocardial ischemia is unremitting, effort related, and can radiate to the jaw and throat.

Even though GERD can be exacerbated by effort, GERD should be at the bottom of the differential. When a patient presents with any effort-related symptom—whether it is angina or an angina equivalent, such as breathlessness or claudication on effort—consider it ischemia until it is proven to be something else.

Age. The older the patient, the less classic the presentation. Profound, unexplained, sudden-onset fatigue is a marker of coronary circulation problems in older patients.

Physical exam. The physical examination is often unhelpful in the evaluation of chest pain. By the time you see the patient, he may already be feeling better. If you are seeing a patient in the hospital who has chest pain, conduct a very focused, quick physical examination. Major markers of myocardial ischemia on auscultation are:

• Transient gallops
• Transient paradoxically split second sound
• Mitral regurgitation.

ECG. Look for ST-segment elevation, depression, or pseudonormalization (ie, the ST-T waves look more normal during pain than not during; very-high-risk patient). But the ECG may not always present a straightforward picture.

When interpreting the ECG, says Dr Goldschlager, remember these caveats:

• You cannot always tell the age of a Q wave; it may be a sign of a past infarct or silent infarct
• Most people who get a defibrillator also get a dual-chamber pacemaker; MI cannot be assessed in paced patients or in those with left bundle-branch block
• Right bundle-branch block can obscure changes in V₁ through V₃; on the other hand, leads V₁, V₅, and V₆, and aVL can be easily read, because they reflect LV depolarization
• Flutter waves can deform ST segments, especially in leads V₂, V₃, and aVF, resulting in pseudo-ST changes, which should not be mistaken for ischemia
• Wide QRS complexes can be mistaken for ST elevation, resulting in the wrong therapy.
• Hyperkalemia can cause ST-segment elevation over the right pericardial leads and produce coved ST elevation in leads V₁ and V₂.