Recommendations for new directions in MI prevention
Latest developments in drug therapies
Several new recommendations for therapy and surgical regimens based on drug studies and clinical assessment for the prevention and treatment of myocardial infarction have been completed in recent month.
Doctors at Mount Sinai Hospital in New York City halted a 14-month trial involving 8,800 MI patients on a combination of aspirin and warfarin, after concluding that the combination therapy did not achieve any clinical benefits. The team of investigators, led by Dr. Valentin Fuster, concluded that aspirin monotherapy appears to be equally effective in terms of reducing cardiovascular morbidity and mortality as that of a low-dose aspirin and warfarin combo.
3 protocols to the trial
The trial set up three therapy protocols, with patients receiving either 160 mg of aspirin alone, 80 mg of aspirin with 1 mg of warfarin, or 80 mg of aspirin with 3 mg of warfarin. The trial was stopped after no significant difference in the rates of reinfarction, stroke, or death in the patients was determined. And while the aspirin-warfarin combination did reduce the levels of factor VIIa, the study’s investigators also question whether that suppression itself is a worthwhile therapeutic goal, as no clinical benefits were derived from VIIa suppression. More information on the study can be found in the August 9, 1997, issue of The Lancet.
Backing aspirin as prevention
The American Society of Health-System Pharmacists has published a position paper supporting aspirin as a prevention tool for MI and is calling on pharmacists to begin educating the health care industry about its benefits and the appropriate patient screening required to accompany aspirin prophylaxis.
The organization is recommending dosages of 75 mg to 325 mg a day for long-term use, with an initial dosage of 160 mg to 325 mg in acute settings. The position paper goes on to state, "Patients with acute MI should receive non enteric-coated aspirin 160 to 325 mg (two to four children’s tablets or one adult tablet) to chew and swallow as soon as possible after the clinical impression of evolving acute MI is formed and whether or not thrombolytic therapy is to be given."
The paper also supports aspirin as a secondary prophylaxis to help prevent a recurrence of MI. It also provides benefits for patients with stable or unstable angina. Specifically, the paper calls for primary prophylaxis in men over the age of 50 with coronary artery disease risk factors including hypercholesterolemia, smoking, diabetes mellitus, hypertension, or a family history of early coronary artery disease. The organization decries the lack of quality clinical trials involving female patients and calls for such trials to begin.
The paper’s authors stress that candidates for primary aspirin prophylaxis should not have any known risk factors involving gastrointestinal or cerebral hemorrhage such as peptic ulcer or uncontrolled hypertension, for example, or any other known adverse reactions to aspirin. The dosage recommendations being made are associated with a low risk of GI effects, based on clinical trials.
The authors noted that patients with chronic stable angina reduced their risk of acute myocardial infarction by 87% based on a 60-month follow-up study when taking 325 mg of aspirin every other day, and that for patients with stable angina, the risk of MI was reduced by 48% for patients on long-term aspirin therapy. The complete position paper and its references can be found in the Sept. 1, 1997, issue of the American Journal of Health-System Pharmacy.
Aggressive surgery promoted
A Danish study of 1,000 MI patients conducted at 43 locations is recommending angioplasty or bypass surgery for patients who have had thrombolytic therapy following myocardial infarction where inducible ischemia is present.
The study separated patients into two categories, those receiving surgery or those receiving therapy after MI, and found significantly lower rates of acute MI or unstable angina in patients receiving surgery, although mortality rates between the two groups were ot significantly different throughout a two-year follow-up.
Occurrences of death, reinfarction, or hospital admission for unstable angina compiled together as a one-year follow-up criteria affected 15.4% of patients receiving surgery compared with 29.5% receiving therapy. At a two-year follow-up, those numbers were 23.5% and 36.6% respectively, and then 31.7% and 44% at three years.
Aggressive strategy pays
For the study, postinfarction ischemia was defined as either spontaneous angina more than 36 hours after admission or ST segment changes during exercise tests, with or without angina. The study report can be found in the August 5, 1997, issue of Circulation. It is accompanied by comments from doctors at Cleveland Clinic who support the study’s findings, and write, "The aggressive strategy was associated with a halving of reinfarction, a 40% reduction in unstable angina, and a highly significant reduction in the composite endpoint at a median of 2.4 years. . . . Even mortality was tracking in the right direction. . . . These results validate for the first time that percutaneous transluminal coronary angioplasty of the infarct vessel in selected patients who have received thrombolytic therapy leads to fewer recurrent ischemia events."
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