Preventing Secondary Myocardial Infarction

Karen Gao, PharmD Candidate, and David Q. Pham, PharmD, BCPS
Published Online: Saturday, December 1, 2007

Ms. Gao is from the Arnold & Marie Schwartz College of Pharmacy and Health Sciences, Long Island University, Brooklyn, NY. Dr. Pham is assistant professor of pharmacy practice at Western University of Health Sciences, College of Pharmacy, Pomona, Calif.


Myocardial infarction (MI) occurs in approximately 1.5 million Americans each year, with more than 60% of cases occurring in patients aged 65 and older.1 Approximately 30% of patients die from an MI, and half of these patients die within 1 hour of the onset of symptoms.2 Pharmacists must understand the prevalence and severity of MIs in order to educate patients about the importance of self-management of their disease state to prevent future occurrences.

Understanding Pharmacotherapy

Before counseling patients, a thorough understanding of the basic pharmacotherapy behind MIs is required, including a review of the normal hospital course for patients presenting with MI.

First, it is extremely important to inform patients that they must act fast in getting help, as immediate action is critical in reducing mortality. Once a patient arrives at the hospital, oxygen is usually administered at 2 to 4 L/min right away via nasal prongs, with the level of oxygen saturation >90%. The patient immediately should chew on a non?enteric-coated aspirin 162 to 325 mg, if he or she has not already taken one at home. If the patient is allergic to aspirin, administer clopidogrel 300 mg or ticlopidine 250 mg.

Nitroglycerin also should be administered; the patient should receive 1 tablet sublingually every 5 minutes for a total of 3 doses. After 3 doses, if the patient is still experiencing chest pain, intravenous (IV) nitroglycerin is considered. Nitroglycerin should not be used in patients with a systolic blood pressure of <90 mm Hg or a decrease of >30 mm Hg from baseline. It also is contraindicated in patients who have taken a phosphodiesterase inhibitor within the last 24 to 48 hours and if right ventricular infarction is suspected.

Beta-blockers are administered if there are no contraindications such as cardiogenic shock, second- or thirddegree heart block, bradycardia, or overt cardiac failure. Both atenolol and metoprolol may be used. For adults, IV atenolol 2.5 to 5 mg should be administered over 2 to 5 minutes and repeated every 10 minutes, if tolerated, up to 10 mg over 10 to 15 minutes. Oral administration can be started 15 minutes after the last IV dose. Initial dose is 50 mg; 12 hours later, another 50 mg should be administered. The dose can be titrated up to 100 mg per day for 6 to 9 days, unless the patient experiences bradycardia or hypotension. If metoprolol is used, the initial dose is 2.5 to 5 mg IV at 2- to 5-minute intervals for 3 doses. The oral initial dose is 25 to 50 mg every 6 hours for 2 days, starting 15 minutes after the last IV dose. The maintenance dose is 25 to 100 mg every 12 hours.

Thrombolytic therapy (low-molecularweight heparin or unfractionated heparin) should be administered to patients if no contraindication exists. Thrombolytic therapy is for patients who had onset of symptoms >3 hours ago but <12 hours. Dalteparin dose with concurrent use of aspirin is 120 IU/kg every 12 hours by subcutaneous injection, with a maximum dose of 10,000 IU in 12 hours. This treatment is continued for 5 to 8 days. If IV heparin is used, it is dosed at 60 IU/kg/dose, followed by 12 IU/kg/hr with a maximum dose of 4000 IU/dose or 1000 IU/hr.2,3

In addition to the therapies mentioned above, it is important to monitor the patient's blood pressure and heart rate at all times. An electrocardiogram should be performed, and continuous cardiac monitoring is recommended. It also is important to monitor side effects and tolerability of the medications.

Treatment Adherence Essential

Treatment adherence after an MI is necessary to ensure that another MI does not occur. Beta-blockers, angiotensin- converting enzyme inhibitors (ACEIs), statins, calcium channel blockers, and aspirin are especially beneficial in post-MI patients. Beta-blockers should be used as long-term therapy, unless there are absolute contraindications. ACEIs have shown benefits in reducing mortality in post-MI patients in combination with aspirin and beta-blockers. Statins also are efficacious in this group of patients. Clinical trials have demonstrated that statins improve lipid profile and increase flow-mediated endothelialdependent vasodilation in post-MI patients.2 Studies have demonstrated that statins reduce cardiovascular death and recurrence of myocardial ischemia.

Aspirin with a dose of 75 to 325 mg/ day can be used for post-MI patients. Warfarin in combination with aspirin can be beneficial. Combining aspirin 75 to 81 mg with warfarin to maintain an international normalized ratio of 2 to 2.5 has been found to add benefits to patients4; however, it should be used in patients who are at high risk for thromboembolic events. Eplerenone also has demonstrated benefits by reducing morbidity and mortality in patients after an acute MI with left ventricular dysfunction and congestive heart failure. Eplerenone needs to be used with caution in patients with hyperkalemia.

Post-MI Counseling Tips

Post-MI treatment is important in preventing a future MI. If needed, smoking cessation counseling should be suggested. 5 Exercise and activity recommendations should be based on the severity of the MI. Patients should be counseled to develop a recovery plan and time frame to return to physical activity with their physician. Within 1 or 2 days of an MI, the physician will usually ask that the patient begin to move around, possibly by stretching and walking in the hospital room or hallway. Before leaving the hospital, the doctor may recommend that the patient have an exercise stress test to see how much exercise the heart can tolerate. In general, patients may resume their normal activities after 6 to 12 weeks of the MI. Before that time, all exercise should be supervised.

Patients should be advised to limit saturated fats, cholesterol, and sodium and be reminded to follow their dietitian's recommendations on making appropriate food choices. Fish is part of a hearthealthy diet. It contains omega-3 fatty acids, which can help improve blood cholesterol levels and prevent another MI. Patients also should be instructed to consume lots of fruits and vegetables that contain antioxidants that may be beneficial to the coronary arteries.

Recognizing the Signs

Recognizing the symptoms of an MI is also important. Initial treatment is vital to the outcome for survival. The patient should be informed about how to react if he or she experiences another MI, as acting fast to receive proper treatment can increase the survival rate and produce positive effects. If signs of an MI occur, patients who have yet to take their daily aspirin should take it immediately. Nitroglycerin should be placed under the tongue. A call should be made to 911 if the angina symptoms do not subside or if the patient believes he or she is experiencing a heart attack.

Effective patient counseling from pharmacists should improve outcomes by delaying the progression of MI. Overall, the goal is to prepare and enable patients to resume daily life without forgetting the importance of the rehabilitation process.

References

  1. Rich MW. Epidemiology, clinical features, and prognosis of acute myocardial infarction in the elderly. Am J Geriatr Cardiol. 2006;15:7?11.
  2. MD Consult Web site. Available at: www.mdconsult.com. Accessed: June 2007.
  3. McEvoy G, Snow E, Kester L. AHFS Drug Information. 2005 edition. Bethesda, Md: American Society of Health-System Pharmacists; 24:20, 20:12:16.
  4. Jeddy A, Gleason B. Aspirin and warfarin versus aspirin monotherapy after myocardial infarction. Ann Pharmacother. 2003;37:1502-1505.
  5. Hanssen TA, Nordrehaug JE, Eide GE, Hanestad BR. Improving outcomes after myocardial infarction: a randomized controlled trial evaluating effects of a telephone follow-up intervention. Eur J Cardiovasc Prev Rehabil. 2007;14:429-437.


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