New meds available for myocardial infarction

There are exciting new classes of drugs recommended in the new guidelines for management of acute myocardial infarction (AMI), according to Barbara Riegel, DNSc, RN, CS, FAAN, one of the authors of the updated guidelines, and a member of the executive committee for the American Heart Association (AHA) Council on Cardiovascular Nursing.

Here are new medications for AMIs recommended in the new guidelines, published jointly by the Dallas-based AHA and the Bethesda, MD-based American College of Cardiology (ACC):

Low molecular weight heparin (LMWH).

This is a major category of drugs added enthusiastically to the guidelines because of their effectiveness and convenience, Riegel says.

Heparin was used in the past, but studies have found that LMWHs have fewer side effects for patients, notes Julie Bracken, RN, MS, CEN, director of nursing education at Cook County Hospital in Chicago and representative to the Heart Attack Alert program for the Emergency Nurses Association.

LMWHs are given if there is no major contraindication, such as bleeding risk to patients believed to be having an MI without ST elevation who also have refractory ischemia and/or high-risk features (signs of shock, pulmonary congestion, heart rate over 100 beats per minute), says Dorothy M. Lanuza, PhD, RN, FAAN, a professor at Niehoff School of Nursing in Maywood, IL.

The LMWHs are a distinct class of drugs, but there is important variety within specific agents, cautions Riegel. "The trials have shown differing results when different LMWHs were used. This led us to realize that the class is the same, but the specific agents are not interchangeable."

Glycoprotein (GP) 11b/111a inhibitors.

These appear to reduce acute events and stabilize patients in the acute phase of MI, but without ST-segment elevation, reports Riegel. "This class of drugs generated quite a bit of enthusiasm among the guideline committee members."

GP IIb/IIIa inhibitors are geared toward stabilizing patients with non-Q-wave MIs (subendocardial infarction), which comprise about 65% of total MI patients, notes Bracken. "Those are the ones that are harder to diagnose," she says. "The Q-wave MIs are pretty easy since see you can see the elevation and changes on the EKG. It’s the patients who don’t have those changes who are more difficult to diagnose."

The GP IIb/IIIa inhibitors are new a category of drugs, notes Bracken. "They have only been around for about two years and were used in cardiology and inpatient care, but not in the ED. Now since many more patients are having angioplasty, the use is greater."

The greater use in the ED reflects a shift in therapy to the ED, says Bracken. "We’re seeing more use in the ED, because more patients are going to the cath lab for angioplasty than in the past."

New cardiac markers.

Rapid, sensitive cardiac markers, such as troponin, are improving diagnostic accuracy and the comfort of staff who have to discharge "suspect" patients home," says Riegel.

It’s the patient without ST elevation, but with classic symptoms, who is most worrisome, she says. "Is this an MI or is this unstable angina? Should this patient get a thrombolytic or not? With the new markers, we can tell what’s really going on without waiting for a confirmation that it’s too late to give a thrombolytic."

There is an excellent discussion of the new cardiac markers in the updated guidelines, Riegel recommends. "Nurses should read up on these new markers and know which one to use based on the time of chest pain onset."

For example, if the patient presents early, the cardiac marker CK-MB (isoenzyme of creatine kinase with muscle and brain subunits) has an improved sensitivity and specificity for diagnosis of acute MI within the first six hours, Riegel says. "If ED nurses don’t know when the various markers peak, they won’t know which test should be ordered based on the onset of chest pain."

Although the guidelines clearly state that patients with detectable levels of troponin benefit from the most from thrombolytics, cardiac markers are not routinely used in the ED, notes W. Douglas Weaver, MD, FACC, division head for the department of cardiovascular medicine at Henry Ford Hospital in Detroit and a member of the task force that developed the ACC/AHA guidelines. "With the advent of these new therapies for unstable angina and non-ST segment elevations, the guidelines now suggest the result of both these biomarkers be available to the treating physician within 30 to 60 minutes."

A thorough assessment and continuous monitoring of patients with suspected coronary syndromes, including a targeted history, detecting electrocardiogram abnormalities, and elevations in serum cardiac marker levels (such as myoglobin), are crucial to early detection and treatment of myocardial ischemia, injury, or infarction, says Dorothy M. Lanuza, PhD, RN, FAAN, a professor at Niehoff School of Nursing in Maywood, IL. "As bedside testing for serum cardiac markers becomes more prevalent, this will help to speed up the diagnostic work-up," she says, adding that bedside results should be confirmed by traditional lab results.

For more information about the guidelines, contact:

Julie Bracken, RN, MS, CEN, Director of Nursing Education, Cook County Hospital, 1835 W. Harrison St., Chicago, IL 60612. Telephone: (312) 633-7683. Fax: (312) 633-8539.

Dorothy Lanuza, PhD, RN, FAAN, Niehoff School of Nursing, McGuire Building, Room 2859, 2160 S. First Ave., Maywood, IL 60153. Telephone: (708) 216-8097. Fax: (708) 216-9555. E-mail:dlanuza@luc.edu.

Barbara Riegel, DNSc, RN, CS, FAAN, School of Nursing, San Diego State University, San Diego, CA 92182-4158. Telephone: (619) 594-6173. Fax: (858) 499-4665. E-mail: briegel @mail.sdsu.edu.

W. Douglas Weaver, MD, FACC, Henry Ford Hospital, 2799 W. Grand Boulevard, Detroit, MI 48202. Telephone: (313) 916-4420. Fax: (313) 916-1249. E-mail: wweaver1@hfhs.org.