A diminished activated coagulation time response to an initial bolus of heparin is associated with major in-hospital complications after coronary angioplasty, although patients with complications did have a higher risk before the procedure. It remains to be determined whether there is an ideal "target" activated coagulation time for interventional procedures.

Background: The use of the prehospital electrocardiogram (ECG) to identify patients with ST-segment elevation myocardial infarction (STEMI), coupled with a centralised system to alert the cardiac catheterisation team in preparation for prompt intervention, has been shown to reduce door-to-balloon times (DBT) effectively. A confounding variable in prolonging the recommended 90 min DBT is the time of day or day of the week of patient presentation. We postulated that use of the prehospital ECG, coupled with an emergency department initiated ''Cath Alert'' system, could neutralise DBT delays related to time of day or day of week. Methods: A prospective study was conducted on 167 consecutive patients presenting to our emergency department with acute STEMI. All patients were treated with primary percutaneous coronary intervention. Patients were grouped according to time of presentation: during regular hours (Monday to Friday 08:00 to 17:00) vs off hours (after 17:00 on weekdays and all hours on weekends). Baseline recorded variables included mode of presentation, transmission of prehospital ECG, and activation of Cath Alert system. Results: Overall, the mean (SD) DBT was 69 (35) Conclusion: Variables such as time of day and mode of presentation have an impact on achieving currently recommended DBT in patients with STEMI. With the addition of each prehospital variable in succession-that is, arrival by emergency medical services, Cath Alert system, and the prehospital ECG-the DBT can be progressively shortened and the adverse ''off hour effect'' nullified.

The accurate assessment of coagulation status is an important part of interventional procedures performed in the cardiac catheterization laboratory. While the traditional clinical means of assessing heparin anticoagulation has been with the activated partial thromboplastin time (APTT), the activated coagulation time (ACT) has come into widespread use in the catheterization laboratory as an assay of whole blood clotting time which can be performed rapidly at the bedside. The purpose of the present study was to (1) assess the anticoagulant effect of a 10,000 U bolus of heparin in PTCA patients and (2) document the relationship between ACTs and APTTs in a subset of these patients. Baseline and postheparin ACTs were measured using a HemoTec coagulation timer in 545 unselected PTCA patients. The average baseline ACT was 120 +/- 22 sec. After a 10,000 U bolus of heparin the average ACT was 249 +/- 44 sec; 58% of patients had an ACT less than 250 sec, 17% had an ACT between 250 and 275 sec, 12% had an ACT between 275 and 300 sec, and 13% had an ACT greater than 300 sec. A total of 175 paired ACT and APTT measurements were obtained in a random subset of these patients at baseline, after heparinization, and at 4-6 hr intervals after the procedure. The APTT was limited by absolute upper and lower limits of 150 and 22 sec; there were no such limits on the ACT. When limiting values were excluded, there was a strong overall correlation between ACT and APTT measurements (r = 0.92, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)