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Right Heart Thrombi
Acknowledgment
The authors acknowledge the contributions of Dr. Vrinda Sardana, who was the author of this chapter in the previous edition.
Right heart thrombi (RHT) are relatively common but can often be missed on routine echocardiography without careful image acquisition and high suspicion. Because of increased use of right heart catheters, pacemakers, and other devices coupled with a growing population of adults with congenital heart diseases and end-stage heart failure, the incidence of RHT is expected to climb. Despite an association with symptomatic pulmonary embolism (PE), RHT often remain asymptomatic and are incidentally identified during contrast-enhanced echocardiography, cardiovascular magnetic resonance imaging (CMRI), or cardiac computed tomography (CT). Documented reports of detectable RHT in the general population likely underestimate the true frequency of occurrence based on conventional two-dimensional (2D) echocardiography. This chapter reviews risk factors, at-risk patient populations, and characteristics of RHT and offers suggestions on echocardiographic image acquisition, optimization, and interpretation. It concludes with a brief overview on both traditional and novel, innovative treatment approaches.
Incidence
The true incidence of RHT is difficult to determine because of inconsistent definitions, the clinically silent nature of many of these thrombi, and variations in diagnostic techniques employed. In a large, Swedish, population-based autopsy study that included both in- and out-of-hospital deaths, the reported incidence of RHT was 3.4%. PE was identified in 22.8% of all cases and in 43.4% of patients with RHT. In hemodynamically stable patients with PE assessed by echocardiography, 2% to 3% have RHT. Among unstable patients with acute massive PE, the incidence of RHT is as high as 18%. In the Italian PE registry, echocardiography within 48 hours of admission identified RHT in 4.5% of all patients. When risk stratified, incidences were 0.3%, 3.8%, and 16% in low-, intermediate-, and high-risk patients, respectively. Variable terminology, such as thrombi-in-transit, free-floating thrombi in the right heart (FFTRH), right-sided intracardiac thrombus, and RHT may be the largest contributor to ambiguity in incidence reporting. When associated with PE, RHT are thought to be residual thrombi in transit from the deep venous system to the pulmonary vasculature. However, it is likely that some thrombi form in situ within the right atrium (RA) or right ventricle (RV), as may be the case with catheter- and cardiomyopathy-associated intracardiac thromboses, respectively.
Risk Factors
A myriad of modifiable and nonmodifiable risk factors predispose patients to the development of RHT. Knowledge of these risk factors is important to ensure image acquisition and interpretation is performed with a higher degree of scrutiny, allowing for earlier detection of RHT in at-risk patients ( Table 128.1 ).
TABLE 128.1
Risk Factors for Right Heart Thrombi
| Patient Characteristics | Disease State | Catheter or Device | Drug or Substance Intake |
|---|---|---|---|
| Male Age (65 years or older) Hypercoagulable Obesity Immobility Pregnancy Trauma or surgery Protein C/S deficiency Thrombophilia APLS |
Malignancy COPD Chronic hemodialysis Congestive heart failure Atrial fibrillation or flutter Cardiomyopathy Cor pulmonale RV contusion RV infarct ARVD/C IBD Behçet disease |
CVC (size, type) Pacemaker (especially temporary) Multiple PICC size Internal jugular location Subclavian vein location Distal position Duration (>6 days) |
Amphotericin B Parenteral nutrition No prophylaxis Cigarettes Contraceptives |
APLS , Antiphospholipid syndrome; ARVC/D , arrhythmogenic right ventricular cardiomyopathy/dysplasia; COPD , chronic obstructive pulmonary disease; CVC , central venous catheter; IBD , inflammatory bowel disease; PICC , peripherally inserted central catheter; RV , right ventricular.
Central Venous Catheters
Central venous catheters (CVCs) are used in up to 8% of hospitalized patients and can lead to thrombotic complications in up to 66% of those individuals. CVC tip-associated thrombi at the cavoatrial junction or within the RA, RV, or pulmonary artery (PA) are often detected by echocardiography. Catheter-related RHT are identified on autopsy in up to 29% of cases when CVCs are present at the time of death; however, frequency varies among reports of live patient populations. Their presence is likely related to tip position, catheter type, concomitant infection, and patient comorbidities.
Catheter-related right atrial thrombi identified by transthoracic echocardiography (TTE) have been reported in up to 9% of children with malignancy and up to18% of patients with hemodialysis catheters. Yet no guidelines for management of these thrombi currently exist. Among several proposed treatment algorithms, catheter removal and 3 to 6 months of anticoagulation is the most commonly recommended strategy, likely derived from published guidelines on treatment of catheter-related upper extremity venous thrombosis and intracardiac thrombi.
Atrial Fibrillation and Flutter
The incidence of atrial fibrillation (AF) and flutter (AFL) is high, especially in older adults. It is well-appreciated that thrombi form in the left atrial appendage (LAA), increasing the likelihood for systemic embolization and stroke. Therefore, transesophageal echocardiography (TEE) before elective electrical cardioversion is standard clinical practice.
The RAA, despite having a wider mouth and less deep recesses, is also subject to low flow, spontaneous echocardiographic contrast (SEC), and thrombus development in AF and AFL ( Fig. 128.1 and 
). The incidence of RAA thrombi in AF varies from 0.4% to 7.5%. In the Assessment of Cardioversion Using Transesophageal Echocardiography (ACUTE) trial, 9 of 549 patients (1.6%) with AF had a right heart thrombus, without specifying the number of RAA thrombi. Similarly, in another large investigation of 983 patients with AF and AFL presenting to the emergency department, 0.73% had RAA thrombi. RAA peak emptying velocities were lower, similar to velocities in the LAA. Four of 7 patients with RAA thrombi had isolated right-sided clots, and all patients had decompensated congestive heart failure. As in the LAA, SEC in the RA is a marker for organized embolic potential. Compared with patients with nonvalvular AF without RA SEC, the incidence of pulmonary defects on pulmonary scintigraphy in patients with RA SEC was 40% versus 7% ( P = .006) despite similar D-dimer and fibrinogen serum thrombotic markers.
Video 128.1. An early multiplane transesophageal echocardiographic examination (circa 1994), 90-degree orientation, performed for atrial fibrillation. Leftward rotation revealed a large thrombus (arrow) in the right atrial appendage. A linear echodense line seen entering the superior vena cava is a pacemaker wire (arrow). (Also see Fig. 128.1 )
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