To investigate the incidence and clinical characteristics of femoral vein thrombus after leadless pacemaker implantation.

The patients received leadless pacemaker implantation in Zhongshan Hospital, Fudan University from April 2020 to January 2021 were consecutively included. All of the patients suffered from bradycardia were indicated for a single chamber pacemaker implantation and received femoral vein ultrasound at the first day post-procedure. The incidence and the clinical characteristics were described and the correlation factors were analyzed.

One hundred and forty-six patients were enrolled. The incidence of femoral vein thrombus was 2.74% (4/146). The average age of these 4 cases was (75.75±19.14) years old with 3 males,and all the patients were asymptomatic. During follow-up, there were no adverse outcomes happened, including thromboembolism with the thrombus. The femoral vein thrombus of 3 cases disappeared at 1 month's follow-up, and 1 case disappeared at 2 months post-procedure. In thrombus group, elevation of D-dimmer (>0.5 mg/L) were documented in 1 case (25.00%) pre-procedure, and 3 cases (75.00%) post-procedure while the median level of D-dimmer pre-procedure were not significantly different as compared to post-procedure [0.33(0.26,0.94) mg/L vs.1.49(0.67,2.17) mg/L,P=0.057)].The occurrence of femoral vein thrombus after leadless pacemaker implantation was significantly associated with D-dimmer elevation post-procedure by Spearman correlation analysis (r=0.239,P=0.037). While it was not significantly correlated to the other factors including age, gender, body weight, comorbidities (atrial fibrillation, hypertension and diabetes), baseline echocardiographic parameters, D-dimmer elevation pre-procedure, fluoroscopic time and closure methods (all P>0.05).

The incidence of femoral vein thrombus was rather low. Monitoring D-dimmer and performing puncture site ultrasound post-procedure are helpful to detect femoral vein thrombus and start anticoagulation in time.