How to deal with acute coronary syndromes

October 5, 2007

Acute coronary syndromes (ACS) are one of the most frequent conditions a family physician is likely to encounter. More than 2.3 million patients are admitted to U.S. hospitals every year for ACS symptoms. The problem is that what looks and feels like a myocardial infarction could be something as simple as GERD or anxiety.

Acute coronary syndromes (ACS) are one of the most frequent conditions a family physician is likely to encounter. More than 2.3 million patients are admitted to U.S. hospitals every year for ACS symptoms. The problem is that what looks and feels like a myocardial infarction could be something as simple as GERD or anxiety.

"We usually encounter somebody who experiences chest pain," said Clare Hawkins, MD, associate professor of family medicine at Baylor College of Medicine. "There are lots of things that do not cause crushing chest pain that are cardiac events and a lot of things that do cause crushing chest pain that are not cardiac events. It can be difficult to distinguish between them."

Distinguishing between what is and is not a serious cardiac event is so difficult that physicians are likely to make mistakes, Dr Hawkins cautioned during the American Academy of Family Physicians 2007 Scientific Assembly. Acute myocardial infarction, or AMI, is the most common cause of legal action against family physicians and internists, he said.

The reason? AMI is the most prevalent misdiagnosis by family physicians and by internists. AMI is also the most frequent and most expensive legal claim made against emergency department physicians, he added.

A number of serious, even life-threatening conditions mimic MI, he explained, included periocarditis, myocarditis, aortic dissection, pneumonia, and pulmonary embolism. Less serious confounders include GERD, esophageal rupture, intercostals spasm, and excessive worry about cardiac conditions brought on by an acute coronary event that happened to a close friend or relative.

The first step in dealing with what may be an acute coronary syndrome is to stratify the patient by risk. Patients at low risk can probably wait a day or even a weekend for more extensive evaluation. Patients at high risk may be sent to the catheter lab on the next available gurney.Factors that indicate a higher risk include a first order male relative who had a cardiac event before age 55, smoking, elevated lipids, diabetes, and a prior MI or percutaneous cardiac intervention (PCI).

Male gender is generally not a risk factor, Dr Hawkins noted. Cardiovascular disease is the number one killer of women, as it is of men. The primary gender difference is that women tend to present with coronary problems five to 10 years older than men. By middle age, he noted, men and women are equally likely to experience cardiac events.

A typical MI causes dull, heavy, crushing pressure and pain, he said, a feeling that patients often describe as "an elephant sitting on my chest." But a significant minority of MIs create sharp pain. Either way, the pain is typically central, radiating to the jaw, left arm, back, or shoulder. More than half of MIs are not associated with recent exercise or some other stress event.

Testing for a MI can be difficult, Dr Hawkins said. About 15% of patients with MI produce a normal EKG on admission. Even serial studies are only 50% sensitive for detecting an MI. An angiogram remains the gold standard for diagnosing an MI.

Patients often believe that MI is caused by a narrowing of a cardiac artery. Narrowing of the lumen plays a major role in angina, Dr Hawkins said, but a MI is triggered by the rupture or fissure of a lipid plaque that sparks a coagulation cascade. It is the blocking of an artery by a clot that stems blood flow and kills cardiac tissue.

"The core of intervention in ACS revolves around plaque rupture," Dr Hawkins explained. "You need to stop that coagulation cascade and remove the clot that has already formed."

Aspirin is generally the first medication given to any patient who is exhibiting what may be cardiac symptoms, he continued. The typical loading dose is 325 mg, chewed and swallowed as quickly as possible.

Beta blockers are also important in the acute phase because they lower cardiac oxygen demand. Patients with an acute MI should also be given thrombolytic agents as soon as possible.Troponin is the most reliable marker for cardiac death, Dr Hawkins said, followed by elevated CK. Most hospital protocols call for a series of tests beginning at admission and continuing over 12 to 18 hours. C-reactive protein, or CRP, can be a useful marker for inflammation, but is not specific to plaque rupture.

Anticoagulation therapy includes aspirin, clopidogrel, and heparin. Most institutions have moved from unfractionated heparin (UFH) to low molecular weight heparin (LMWH) despite significant cost differences. LMWH is easier to dose and effects are more predictable, Dr Hawkins explained.Some intensivists prefer UFH because LMWH can interfere with later PCI procedures. And anticoagulation with UFH can be halted simply by stopping the drip. LMWH activity persists for about 12 hours after administration.

Whether patients are treated by stenting or coronary bypass, discharge is a key time."Most of us forget to give patients appropriate instructions at discharge," Dr Hawkins noted.Patients tend to do better if they have written instructions to take home as well as oral information, he continued. Many patients also benefit from cardiac rehabilitation, which is often nonmedical personnel who are trained to coach them through their discharge treatment plan.

One of the most important elements of post-discharge treatment is continuing aspirin, beta blockers, ACE inhibitors, and statins. The most effective method seems to be starting discharge meds while the patient is still hospitalized. That helps emphasize the importance of specific medications."If you start statins and aspirin and other things in hospital, people are more likely to stay on them," Dr Hawkins said. "If you just tell them about it at discharge, drug information gets lost in the confusion of going home."