Previous studies of interventions in acute myocardial infarction (MI) have attempted to determine which intervention is better, thrombolytic agents or angioplasty. One possible alternative would be to use both interventions in patients with acute MI. Some small studies have raised the concern that thrombolytic use before angioplasty would significantly increase the risk of bleeding. Ross and colleagues studied the safety and effectiveness of using a short-acting thrombolytic agent followed by angioplasty in patients with acute MI.
Patients who met the criteria for acute MI were eligible for the study. All of these patients received aspirin and heparin therapy before the start of the study interventions. They were then randomized to receive a 50-mg bolus of recombinant tissue-type plasminogen activator (rt-PA) or placebo. The half-life of rt-PA is 4.5 minutes. All patients were then studied by coronary angiography followed immediately by angioplasty if it was indicated. Outcome measures were patency rates at the time of the initial angiography, technical results of angioplasty, complication rates, left ventricular function and time to restored patency following angiography.
The patency rate of coronary arteries at the time of initial angiography was 61 percent in patients who received rt-PA versus 34 percent in patients who received placebo. Restoration of closed artery rates was similar in the two groups. Left ventricular function was the same in the two groups during the start of the angiography, but the convalescent ejection fraction was better if patency of the affected artery was re-established within one hour of the diagnosis. There were no significant differences between the groups with regard to bleeding complications. An interesting point is that 88 percent of the patients had a delay of more than one hour between the establishment of the diagnosis of acute MI and the starting time of the angiography.
The authors conclude that treatment with the combination of a short-acting thrombolytic agent and angioplasty provided better patient outcomes than angioplasty alone, with no increased incidence of adverse events. This was particularly true if angioplasty was delayed for more than one hour.