Reduction of mechanical heart valve thrombosis through a clinical audit

Patients with mechanical heart valves implanted at four cardiothoracic centers were followed up in a hospital in Eastern India. Despite successful surgery and regular hospital visits, long-term survival was compromised by anticoagulation-related complications.

Systematic analysis revealed under-anticoagulation in most patients. Thrombosis risk in 80 patients on regular follow up from 1989 to 1997 was 8.68 per 100 patient years (pt-yr). The incidence of both thrombotic and bleeding complications was reported as less than two per 100 pt-yr, when prothrombin time was consistently in the range of INR 2.5 to 3.9. In targeting this low event rate, impediments to optimum anticoagulation in the local set-up were identified. International Normalized Ratio (INR) was introduced to report prothrombin time (PT). Patients and doctors were educated about drug and diet interactions with oral anticoagulants (OAC) and the early features of valve thrombosis. Treatment protocols were evolved. The impact of the remedial measures was studied in 81 patients (64 old, 17 new) over a total of 254 pt-yr of follow up, from 1998 to 2001.

Thrombosis risk was reduced from 8.68 to 5.12 per 100 pt-yr, while non-fatal bleeding events increased from 0.28 to 1.96 per 100 pt-yr. Due to early recognition of occlusive prosthetic valve thrombosis and institution of fibrinolytic therapy, fatal events were reduced from 3.8 per 100 pt-yr to none for four consecutive years (statistically significant at 99% CI).

The clinical audit proved to be a valuable tool for understanding the problems in health care delivery, and bringing about improvement.