Case Report: Post-operative mitral valve replacement complicating with a large cardiac mass and role of TEE in decision making

Investigations

A standard 12-lead ECG was performed which showed sinus arrhythmia with a notched P wave in the inferior leads and a prominent biphasic P wave in lead V1, suggestive of biatrial enlargement (Figure 1). Chest radiography revealed cardiomegaly with a double-density shadow and LV enlargement. These findings suggested a left heart aetiology (Figure 2).

Figure 1. Standard 12-lead ECG demonstrating findings of sinus arrhythmia and biatrial enlargement.

Figure 2. Chest radiograph demonstrating cardiomegaly, straightening of the left heart border and double density shadow.

2D transthoracic echocardiography was performed one day before the planned procedure. The findings showed mitral valve prolapse (bileaflet) with eccentric MR jet (EROA 0.43 cm², regurgitant volume = 91 ml), dilated LA, and borderline dilated LV with preserved LV function. The RV function was preserved with mild TR. Absence of pericardial effusion/thrombus was documented during the preoperative echocardiography. 2D echocardiography confirmed severe mitral regurgitation requiring surgery as per the current ACC/AHA class I recommendation and was referred to a cardiothoracic surgeon for further management, wherein she was advised to undergo mitral valve replacement. To rule out coronary artery disease, a diagnostic coronary angiography was performed which revealed normal epicardial arteries (Figure 3).

Figure 3. Diagnostic coronary angiogram showing normal epicardial coronary arteries.

Preoperative investigations included routine blood tests, thyroid function tests, serology, cardiac enzymes, urine analysis, and serum electrolytes. The procedure was planned following all the above-mentioned investigated parameters being within their reference limits. All the investigated parameters were within the reference limits, and the procedure was planned accordingly. The procedure was executed with aseptic precautions and general anesthesia. A median sternotomy was performed, where the pericardium was opened and cradled. The patient was adequately heparinized and constantly monitored for the coagulation parameters. Routine aortic and bicaval cannulation of the SVC, IVC, LA was carried out and antegrade cardioplegic cannula was carried out besides initiating CPB. Aorta was cross-clamped and root cardioplegia was administered to arrest the heart. The left atrium was opened, followed by excision and replacement of mitral valve with a 31 M TTK Chitra Heart Valve using a 2/0 pledgetted suture. The valve was checked for its functionality using transoesophageal echocardiography. The left atrium was closed in two layers with 3/0 prolene. Routine deaeration and cross-clamping were performed, and the bypass was smoothly weened off. Protamine was administered and routine decannulation was performed followed by placement of RV pacing wire along with mediastinal drain tubes. On achieving hemostasis, the sternum was closed with steel wires, and the chest was closed in layers.

The patient was transferred to the intensive care unit for postoperative care. The vital signs were stable, and the patient received inotropic support. Postoperative echocardiography could not be performed because of an insufficient acoustic window soon after the patient was received. However, TTE was performed within 24 hours to assess prosthetic valve function. Valve functioning appeared optimal, with a trivial transvalvular leak. The forward flow gradients were acceptable (5/3 mmHg) with adequate biventricular function. Postoperative echo remarkably showed a large mass measuring 5.6 cm*4.6 cm extensively occupying the RA cavity when examined from the apical 4-chamber (Video 1) and subcostal 4-chamber views (Video 2). The subcostal IVC long axis showed an IVC within normal limits and adequate collapsibility (Video 3). No flow obstruction was noted across the tricuspid valve or SVC (Figure 4) (Video 4).

Figure 4. Transthoracic echocardiography demonstrating a large mass occupying the RA cavity after MVR.

Although the patient was adequately anticoagulated post procedure, transoesophageal echocardiography confirmed the presence and extension of a mass (Video 5) which intruded the RA cavity. An organized echogenic mass, homogenous in appearance, was observed along the lateral wall of the RA with regular borders (Figure 5) (Video 6).

Figure 5. Postoperative TEE performed to identify the extent and location of the mass in RA.

Differential diagnosis

Mitral valve replacement was performed using the traditional approach of a vertical left atriotomy. Susceptibility to thrombus formation can be anticipated due to the presence of a prosthetic valve or sluggish flow in the setting of CHF or cardiomyopathy, which was not observed. The likelihood of thrombus formation within the right atrium was considered the to be least likely based on the echocardiographic diagnosis, since the patient had no provoking factors, as listed above. Intraoperative echocardiography was performed to assess cardiac function before proceeding with surgery, which revealed the absence of clots within the right atrium and major venous channels. Although the atria were dilated, no spontaneous contrast was observed within the chambers, which could be a precursor to thrombus formation.

Normal anatomical variants include prominent thymus glands situated in the superior and anterior mediastinum. It intervenes between the sternum in the front and the pericardium located between the right atria. The thymus progressively increases in size during puberty and undergoes involution at a later age. From the surgeon’s point of view, the thymus was unnoticeable during the examination and was likely to be mistaken for a mass on echocardiography. No history of radiation and chemotherapy or hypercoagulable state/DVT/PE was documented.

Postoperative radiography revealed the absence of mediastinal widening with a well-functioning prosthesis and acceptable transvalvular gradients. TEE exhibited good prosthetic function in the absence of a thrombus. The above-listed conditions were not observed and thus omitted before concluding the possible causes of complications. Various studies have identified common immediate postoperative complications, including active bleeding, PVT, wound infection, valve dehiscence causing paravalvular leak, and mediastinal haemorrhage that required reoperation. Other complications include apical extra pleural hematomas, which were identified on chest radiographs as mediastinal widening with increased mediastinal tube drainage.² Therefore, we believe that a possible complication favouring intracardiac or extracardiac mass requires reexploration under the guidance of TEE.

Transoesophageal echocardiography

On TEE, prosthetic valve function was good (Video 7), with trivial transvalvular leakage and a non-thrombosed valve with a large mass occupying the RA cavity (Figure 6). This led surgeons to decide whether to re-explore the heart or chest only. TEE was performed on a table to assist the surgeon in deciding on a strategic approach for mass excision.

Figure 6. Intraoperative reexploration under TEE guidance showing multiple clots.

Treatment

The diagnosis required immediate management and surgical excision under TEE imaging, with or without exploration of the right atrium. Reexploration was planned under TEE guidance and CPB as a standby if the location was intracardiac. The procedure was performed under general anaesthesia. The sternal wires were then opened and retracted. Multiple organized clots were noted in excess, over the right atrium compressing it externally, consequently placing them intrapericardially (extracardiac) (Figure 6). The clots were excised and had no signs of active bleeding. Post reexploration, TEE did not disclose any intracardiac mass (Video 8), and the RA was decompressed; hence, the patient did not undergo cardiopulmonary bypass (Figure 7) (Video 9). Prosthetic valve function was good after excision of the clot (Video 10). Postoperative ECG showed 1^st-degree AV block and frequent VPCs (Figure 8).

Figure 7. TEE demonstrating a decompressed RA cavity after clot excision with a mitral prosthesis in situ.

Figure 8. Postoperative 12-lead ECG showing 1^st degree AV block and frequent VPC’s.

Chest radiography was performed after re-exploration that showed intact sternal rings, with well seated mitral prosthesis (Figure 9). The patient was stable and transferred to the intensive care unit. Repeat blood investigations were performed, and the output was monitored. The serum creatine and electrolyte levels were within the reference limits. She was advised to undergo physiotherapy rehabilitation as supportive care and was discharged a week later.

Figure 9. Postoperative chest X-ray showing a mitral prosthesis in situ with intact sternal rings.

Outcome and follow-up

The patient was stable on discharge and was asked to monitor the INR and revisit the physician after noticing any signs of bleeding or worsening symptoms. Postoperative echocardiography showed a well-functioning prosthesis and resolution of the clot on the RA side. The patient was symptomatically better (NYHA class I) during the first follow-up at 15 days post-discharge. Chest radiography showed prosthesis in situ with no signs of pericardial or pleural effusion. Currently, she is under regular follow-up and is being screened for prosthetic valve function and symptoms.

Patient perspective

“Her initial diagnosis of the disease was made at a tertiary care hospital. We explained the disease severity and prognosis, if not treated. Her symptoms worsened, limiting her daily activities. Initially, we were concerned about the major surgery, but post counseling, we decided to move ahead. We were explained about the procedural complications by the surgeon. Postsurgical nursing care was helpful in her early recovery. The initial days after discharge were difficult, but with constant family support, she was able to adjust to the environment and perform routine activities independently. We are very thankful to the hospitality and care provided by the health care staffs throughout her stay”.

Details provided by patient’s son.