The following are key points to remember about this review of tricuspid valve dysfunction following pacemaker (PPM) or implantable cardioverter-defibrillator (ICD) placement:

1. Endocardial leads are associated with a number of adverse consequences to tricuspid valve (TV) structure and function. Damage to TV leaflets or subvalvular structures may occur during lead implantation, and it may not be apparent with routine follow-up imaging studies. Avulsion may occur during lead extraction. Chronic interaction between endocardial leads and leaflet and/or chordal structures can result in a foreign body inflammatory and fibrotic response leading to the entrapment of the lead.
2. The prospective incidence of TV damage during lead placement is not known. Retrospective case reports are limited by lack of baseline tricuspid regurgitation (TR) assessment. Most studies suggest that there is a higher incidence of worsening TR in defibrillator leads as opposed to pacing leads, and if there are more than one right ventricular lead.
3. In a series of 41 patients undergoing TV surgery for severe TR believed to be caused by a lead, leaflet impingement was found in 16, leaflet adherence in 14, leaflet perforation in 7, and leaflet entanglement in 4 cases. It appears that the posterior and the septal leaflets may be more vulnerable to injury than the anterior leaflet.
4. A multicenter prospective study currently underway has enrolled 300 patients undergoing cardiac implantable electronic device (CIED) implantation to investigate whether significant TR is caused by the presence of these endocardial leads, with transthoracic echocardiograms obtained within 30 days before and 12 months after implantation.
5. Intravascular hardware and damage to the TV predisposes the patient to endocarditis and thrombosis, either of which can lead to TV dysfunction causing regurgitation or stenosis.
6. Dyssynchronous left ventricular electromechanical activation induced by left bundle branch block or right ventricular pacing is a well-recognized cause of mitral regurgitation. Whether a similar mechanism operates for TR is controversial. Most studies suggest that the physical presence of the lead itself plays the primary, if not the entire role in TV dysfunction, as the percentage of paced beats does not correlate with worsening TR.
7. CIED leads cause echocardiographic imaging artifacts and signal attenuation, due to their high acoustic impedance and reflectivity, resulting in underestimation of TR by color-flow Doppler mapping especially during transthoracic echo, and somewhat less so during transesophageal echo. The regurgitant jet tends to assume an eccentric, rather than a central trajectory, resulting in loss of color-flow Doppler signal, and hence underestimation of regurgitation. In patients eventually found to have severe TR due to CIED leads, only 63% were correctly diagnosed by transthoracic echo during the preoperative study, whereas all were found to have severe TR by preoperative or intraoperative transesophageal echo. Sensitivity of transthoracic echo to detect severe TR can be increased by incorporating hepatic vein assessment (color flow and spectral Doppler).
8. Three-dimensional echocardiography offers improved spatial definition of the interaction between lead and valve and/or subvalvular apparatus, and it is the imaging modality of choice for assessment of CIED lead–TV interaction.
9. There are no prospective data to support TR in the absence of device or endovascular infection as an indication for transvenous lead extraction, hence its absence from the Heart Rhythm Society guideline statement of 2009. However, excess mortality associated with severe TR has been estimated to be 40-75% in patients with CIEDs. When operative risk is low, patients with lead-related severe TR would be expected to benefit from an intervention. If the right ventricle and tricuspid valve annulus are dilated or TV leaflets are damaged, tricuspid valve repair or replacement plus lead removal, relocation, or replacement should be considered. If the right ventricle, tricuspid annulus, TV leaflet appear intact, transvenous lead extraction alone should be considered first.
10. The future of CIEDs in which endocardial leads are absent (leadless pacing) or nontransvalvular (as in His bundle pacing) is likely to be associated with a reduction in lead-related cardiac dysfunction.

Keywords: Arrhythmias, Cardiac, Artifacts, Bundle-Branch Block, Cardiac Surgical Procedures, Constriction, Pathologic, Defibrillators, Implantable, Echocardiography, Three-Dimensional, Electric Impedance, Endocarditis, Endocardium, Heart Valve Diseases, Mitral Valve Insufficiency, Pacemaker, Artificial, Thrombosis, Tricuspid Valve Insufficiency

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