Background: The benefit of thrombolysis in patients with acute myocardial infarction (AMI) strongly depends on the time from onset of symptoms to the initiation of treatment. For AMI patients treated with PTCA this time seems to be important only to a certain time level. The aim of this study was to assess the influence of time to treatment of AMI with coronary angioplasty on short term and long term prognosis.
Methods: We followed 339 consecutive AMI patients treated with coronary angioplasty from 1995 to 1999 in a cardiac care unit. Patients were divided to five groups according to time to treatment.
Results: Time to treatment < 90 min. was achieved in 35 (10.5%); 91-210 min. in 105 (31%); 211-330 min. in 72 (21%); 331-690 min. in 74; > 691 min. in 53 (15.5%) patients. Ischemic time (time from symptom onset to reperfusion) in the groups was < 2 h.; 2-4 h.; 4-6 h; 6-12 h; > 12 h. respectively. The ejection fraction of left ventricle 3-5 days after AMI was 50%, 51%, 45%, 40%, 46% and the 30 day mortality was 5.7%, 2.9%, 11.1%, 10.8%, 11.3% in the groups respectively, showing no significant differences between the groups. However the higher rate of TIMI 3 flow was achieved in patients with time to treatment shorter than 3.5 h. compared to patients treated later (93.6% vs. 83.9%, p = 0.007). The lower 30 day mortality (3.6% vs. 11.1%, p = 0.012), lower 3 year mortality (8.6% vs. 19.1%, p = 0.003), lover frequency of heart failure during hospitalisation (11.4% vs. 28.1%, p < 0.001) as well as lower maximal level of released kreatinkinase (32 +/- 29 vs. 44 +/- 39 mukat/l, p = 0.005) was observed in patients treated within 3.5 h. from symptoms onset compared to patients treated later.
Conclusion: The success rate of primary PTCA to achieve normal flow in infarct related artery is high, but decreases when treatment is started later than 3.5 h. from AMI onset. The short term and long term mortality as well as incidence of heart failure during acute phase is lowest when the intervention was started within 3.5 h. from symptoms onset. Initiation of intervention after 3.5 h. resulted in significant mortality increase, but further delay of treatment had minimal impact on patients prognosis. Great effort needs to be paid to start the primary PTCA within 3.5 h. from AMI onset in as many patients as possible. From our data we can indirectly conclude: patients without a chance for reperfusion with thrombolytic therapy within 4 h. from symptoms onset should be considered candidates for PTCA regardless the time of transportation. In patients with chance to reperfuse infarct related artery within 4 h. from symptoms onset with thrombolytic treatment (thrombolysis needs to be started before 2.5-3rd h.) while having low probability to start PTCA within 3.5 h., the thrombolysis should be given first and PTCA performed later if needed.