PB1193 - Acute myocardial infarction thrombi show fibrin film that increases with ischaemia duration

Background: We have shown that fibrin forms a film on the surface of blood clots. Fibrin films have also been reported on thrombi extracted from patients with acute myocardial infarction and ischaemic stroke, although these observations were retrospective and descriptive. Clinical and biochemical factors affecting fibrin film formation within the vasculature are unknown.

Aims: The aims of this study were to quantify the presence of fibrin films on thrombi from patients with acute myocardial infarction (MI), and to determine which clinical and laboratory parameters influence film coverage.

Methods: Patients (n=52) with acute ST-elevation MI were recruited after admission to Leeds Teaching Hospitals NHS Trust. Thrombi were obtained through aspiration thrombectomy, immediately washed in saline, fixed in 2% glutaraldehyde, dehydrated and subjected to critical point drying, prior to imaging by scanning electron microscopy. Peripheral plasma samples were taken from the antecubital vein and used for turbidimetric analysis of clotting and lysis, analysis of clot fibre density by confocal microscopy, and determination of clot pore size by permeation. Data were expressed as median (range) and correlation was assessed by Spearman rank analysis.

Results: The majority (84.6%) of patients were male. Median age was 61 (31-88) and BMI was 27.1 (21-49). Film coverage ranged from 0.6-60.8% on all thrombi, with a median of 5.5%. Correlation of clinical data and film coverage showed a significant positive correlation of film coverage with ischaemia duration (between call for help and thrombus extraction) (r=0.282 p=0.045). For the laboratory data, film coverage significantly correlated with lag-phase (r=0.489 p=0.005), time to 25% (r=0.430 p=0.014), 50% (r=0.555 p=0.001), 75% (r=0.508 p=0.003), 100% (r=0.404 p=0.022) MaxOD, and with time to reach Vmax (r=0.544, p=0.001).

Conclusion(s): These data show the presence of variable coverage with fibrin film on all acute MI thrombi. Film coverage increased with ischaemia duration and slower ex-vivo clotting.