Background:
Transvenous implantation of pacemakers (PM), implantable cardioverter-defibrillators (ICDs), and cardiac resynchronization therapy (CRT) comprises the positioning of up to three leads in the right ventricle (RV) and/or atrium (RA) as well as in the coronary sinus (CS) where applicable. Standard care and current guidelines do not recommend routine antithrombotic therapies after PM, ICD, or CRT unless due to other indications like atrial fibrillation or history of thromboembolic events. The prognostic impact of asymptomatic lead-associated intracardiac thrombi has not been investigated thoroughly and in relation to different clinical situations.

Methods:
We retrospectively analyzed a consecutive all-comers cohort of 634 patients undergoing implantation of PM, ICD or CRT. Patients were stratified into two groups by the presence of lead-associated intracardiac thrombi (n=81) in echocardiography. The primary combined endpoint (EP) was defined as all-cause death, the occurrence of thromboembolic events (stroke, myocardial infarction, pulmonary embolism, venous and arterial thrombosis), and endocarditis during a median follow-up (FU) of 7.3 years.

Results:
Baseline characteristics showed that patients with lead-associated thrombi were younger (p=0.02), suffered significantly less often from atrial fibrillation (p=0.001) and underwent transeptal puncture less frequently (p=0.011), while they were more often on NSAIDs (p=0.021) and presented less often with RV dysfunction, elevated pulmonary artery pressure and severe tricuspid regurgitation (p<0.05). During FU 238 patients reached the combined EP, while 80 patients reached the secondary EP all-cause death. Cox regression analysis of the total cohort revealed age and the use of NSAIDs as independent predictors of adverse outcome, while the presence of lead-associated intracardiac thrombi was not associated with the occurrence of the primary EP. Interestingly, only age remained an independent predictor of all-cause mortality in our patient cohort, although patients with lead-associated thrombi showed a higher mortality rate by trend (LogRank 15.05, p=0.058) and increased thromboembolic events, however not statistically significant. Subgroup analysis of patients undergoing transseptal puncture due to necessary cardiac interventions did also not show increased occurrence of EPs in patients with lead-associated intracardiac thrombi. Another subgroup analysis revealed that patients on antithrombotic therapy showed a significant increase of the occurrence of EP and all-cause death, which both were still independent from the presence of intracardiac thrombi.

Conclusion:
Our findings suggest that the presence of asymptomatic lead-associated intracardiac thrombi is not associated with adverse clinical outcome independently of clinical high-risk constellations like concomitant transseptal puncture or in relation to antithrombotic therapy strategies. Routine antithrombotic therapy of asymptomatic lead-associated intracardiac thrombi is not recommended unless there are other clinical indications for antithrombotic pharmacological therapy.