Intradialytic Atrial Fibrillation With Rapid Ventricular Response From Catheter-related Right Atrial Thrombus

Abstract

Right atrial thrombus is a rare complication of hemodialysis catheter with an incidence of <6 %. New-onset atrial fibrillation can be the first symptom of catheter-related right atrial thrombus (CRAT) in a patient with long-term dialysis catheter. Therefore, evaluation for CRAT is justified in such scenario. We highlight a case report where a new-onset atrial fibrillation led to the discovery of a right atrial thrombus in a patient with long-term dialysis catheter.

1. Introduction

The incidence of right atrial thrombus is underrecognized. Clinically, right atrial thrombi is present only in a minority of patients, while its incidence in patients undergoing autopsy is about 3 %.1 Causes of right atrial thrombus are varied and include hypercoagulable states such as systemic lupus erythematosus (SLE) and Behcet’s disease, mechanical heart valves, right-sided pacemaker, and ventricular or atrial septal closure. Of these causes, right atrial thrombus as a complication of hemodialysis catheter is an uncommon phenomenon. 2–4 Here, we highlight a case of right atrial thrombus arising as a complication of long-term hemodialysis catheter placement leading to atrial fibrillation during a routine hemodialysis session.

2. Case presentation

A 68-year-old female with end-stage renal disease (ESRD) on maintenance hemodialysis (HD) via a right internal jugular (IJ) HD catheter developed sudden onset palpitations associated with generalized weakness and scotoma during her regular dialysis session. Her heart rate was elevated at 130 beats/minute. The patient was then brought to our emergency department. On presentation, she was found to have atrial fibrillation with a rapid ventricular response. She received metoprolol 25 mg via. oral route which converted her to normal sinus rhythm. In addition, she was started on oral apixaban 5 mg twice a day for anticoagulation, and oral amiodarone 200 mg once a day (after a loading) for maintenance of sinus rhythm. A trans-thoracic echocardiogram (TTE) was performed to evaluate the cause of atrial fibrillation, which revealed a large echodensity in the right atrium (Fig. 1). A transesophageal echocardiogram (TEE) was subsequently performed which revealed a pedunculated right atrial mass measuring about 2.7 × 3 cm with irregular borders, likely attached to the lateral aspect of the right atrial wall, causing mechanical obstruction of tricuspid valve coaptation during systole, with suspicion for involvement of the dialysis catheter tip (Fig. 1). Differential diagnoses for this mass at this juncture included CRAT secondary to chronic right IJ HD catheter, cardiac tumor and, less likely, vegetation. A cardiac structural computed tomography (CT) scan with contrast was performed for further evaluation of the right atrial mass. It revealed a large right atrial hypodensity, likely a thrombus, just proximal to the tricuspid valve with possible extension into the inferior vena cava (IVC) and involving the HD catheter. The finding of a right atrial thrombus with possible extension into the IVC led us to perform a CT scan of abdomen and pelvis with contrast to ruled out intra-abdominal malignancy like renal cell carcinoma. The CT scan results were negative for malignancy and IVC involvement (Fig. 2). Interventional radiology and vascular surgery were consulted, and a decision of deferring surgery was made based on the thrombus size (<6 cm), location (in the right atrium, near tricuspid valve) and the risk of pulmonary embolism. The patient was hence continued on anticoagulation with apixaban, and her HD catheter was removed. She was started on a 10 mg loading dose of oral apixaban twice a day for 7 days followed by 5 mg twice a day maintenance. As for her hemodialysis, she continued to receive her hemodialysis via. a fistula in the right upper arm.

Fig. 1.

TTE (left) showing a right atrial mass (Apical view; blue arrow) and TEE (right) showing a large pedunculated right atrial mass of 2.7 × 3.0 cm with irregular border attached to lateral right atrial wall.

Fig. 2.

CT scan demonstrating a large right atrial hypodensity likely a thrombus (blue arrow) in the catheter tip (red arrow) located just proximal to the tricuspid valve, attached to the right atrial free wall [on the left]; without extension to the inferior vena cava (green arrow) [on the right].

The patient was seen six months later in a follow-up. A TEE at this time revealed persistence of the previous right atrial mass. She also underwent cardiac magnetic resonance imaging (MRI) which confirmed the right atrial thrombus without much change in its dimension from the previous CT scan (Fig. 3). As she had not responded to apixaban therapy, she was readmitted to our facility in-order to undergo a heparin bridge to warfarin. The patient was then discharged on oral warfarin 1 mg daily with an INR goal between 2 and 3.

Fig. 3.

MRI scan showing persistence of right atrial thrombus despite apixaban therapy.

3. Discussion

Right atrial thrombus is common as a complication of venous catheter inserted for parenteral nutrition or chemotherapy, however, it is rare in patients with dialysis catheter, having an incidence of <6 %. This might even be underrepresented, with autopsy showing its incidence in up to 29 % of catheter dependent dialysis patient.1 The mechanism leading to thrombus formation is presumed to be repeated trauma caused by oscillation of the hemodialysis catheter in the right atrium.4

Evaluation by a transthoracic echocardiogram for a right atrial thrombus is insufficient to differentiate it from a mass. The differential diagnosis of right atrial thrombus includes other causes of right atrial mass and pseudo-mass including benign causes such as atrial myxoma, hydatid cyst, lipoma, and malignant causes such as angiosarcoma or rhabdomyosarcoma. In addition, artifacts might also lead to a false positive finding on TTE.5 In a study done by Schwartz Bard et al., TTE results were false-negative for right atrial thrombus in 60 % of the cases.6 Therefore, an esophageal echocardiogram is recommended.

In addition to a TEE, a cardiac MRI or a cardiac CT scan is helpful in evaluating the location and extent of intracardiac thrombi and differentiate it from other intracardiac masses. The advantage these studies offer over TEE is related to the detection of complications including pulmonary embolism and the presence of lymph nodes in cases of malignancy. However, TEE remains the second step in view of radiation hazard related to cardiac CT scan, and the time required along with expense related to a cardiac MRI.7,8 In this regard, we followed up the TTE with a TEE to confirm the diagnosis of right atrial thrombus. We followed up with a cardiac CT scan to help us delineate thrombus boundaries and establish its relationship with the central venous catheter.

Dialysis can be a trigger for atrial fibrillation. Causes are varied and include higher extracted volume and lower dialysate potassium concentration leading to electrolyte imbalance. Atrial fibrillation can also be caused by central venous catheter during its insertion, during reinsertion or at other times due to migration of central venous catheter.9 At other times, atrial fibrillation might be a sign of CRAT as exemplified in our case report.

Management strategies for right atrial thrombus include anticoagulation alone, anticoagulation in conjunction with thrombolytics, and surgical embolectomy. Stavroulopoulos et al. proposed a treatment strategy for catheter related atrial thrombus which included removal of the catheter and initiation of anticoagulation. He further added certain indications for surgery, which included thrombus ≥ 6 cm in size, presence of endocarditis or other cardiac anomalies which are indications for surgery by themselves. In their study, they reported complete dissolution of the thrombus within 3 months of catheter removal and initiation of anticoagulation. Therefore, a follow-up echocardiogram is recommended for evaluation of thrombus dissolution after anticoagulation commencement.10 In a recent meta-analysis by Chen et al., out of 63 patients treated with anticoagulation alone for CRAT, 15 patients had treatment failure.11 In case of unresponsiveness, an alternate anticoagulation can be tried including warfarin or a novel oral anticoagulant (NOAC) of a different class, if still deemed unfit for other surgical interventions. Theoretically, vascular calcification in end stage renal disease is antagonized by matrix G1a protein (MGP) which requires vitamin K for its action. Therefore, the use of vitamin K antagonist might accelerate vascular calcification. Hence, a NOAC might be a good choice for initial anticoagulation in such patients.12 Following the same principle, we started the patient on a NOAC as a first choice of anticoagulation and switched to warfarin after its unresponsiveness.

4. Conclusion

In conclusion, CRAT is an under-reported phenomenon as many patients are asymptomatic at initial presentation. New-onset atrial fibrillation in patients with long-standing catheter may be the only symptom of CRAT. Once CRAT identified, a follow-up imaging either via. A cardiac MRI or a cardiac CT scan is necessary to delineate the size and extension of the thrombus in order to define its treatment approach.