Functional magnetic stimulation: A new modality for enhancing systemic fibrinolysis

Abstract

Objective: To investigate whether functional magnetic stimulation (FMS) of the leg muscles could enhance systemic fibrinolysis. Design: A within-subject analysis of systemic fibrinolysis before and after 60 minutes of FMS. Setting: The Functional Magnetic Stimulation and Special Coagulation Laboratories in the Spinal Cord Injury Service at a Veterans Administration health care facility. Participants: Twenty healthy volunteers were recruited. The exclusion criteria were: (1) personal or family history of venous or arterial thrombosis, (2) personal or family history of cardiac arrythmias, (3) current use of medication, and (4) the presence of a cardiac pacemaker or other metallic implants. Main Outcome Measures: Whole blood clot lysis time (WBCLT) and tissue plasminogen activator (t-PA) antigen determined at baseline and 10 and 60 minutes after FMS. Results: A significant decrease was observed in the mean WBCLT after FMS. The WBCLT decreased from 17 ± 1.3h before FMS to 12 ± 1.0h and 11 ± 0.8h at 10 and 60 minutes post-FMS, respectively. The mean t-PA antigen levels did not show a significant change ( p = .6701) from pre-FMS (6.7 ± 0.91ng/mL) to 10min post-FMS (6.8 ± 0.91ng/mL) and 60min post-FMS (7.0 ± 1.02ng/mL). Several patterns of fibrinolytic response to FMS were observed. They differed in relation to the degree of enhancement, the period at which maximum enhancement occurred, and the corresponding t-PA antigen levels observed. Conclusions: The FMS-induced contractions of the leg muscles enhanced systemic fibrinolysis ex vivo. The improvement in fibrinolysis occurred immediately after FMS and was also observed at 60 minutes post-FMS. FMS appears to produce a sustained enhancement of systemic fibrinolysis that may prove useful in deep-vein thrombosis prophylaxis.