Right heart thrombi (RHT) result either from migrating blood clots from deep venous thrombosis, or they may form in situ predominately due to atrial fibrillation.
While in-hospital mortality rates for patients presenting with acute pulmonary emboli reported to be about 2.5%, patients with RHT have an estimated mortality rate of about 28% and reaching to 80–100% in untreated cases [3]. As regards clinical presentation, patients with RHT were reported to have a rapid, risky, and even lethal outcome.
Trans-thoracic echocardiography (TTE) is the usual initial diagnostic tool for RHT. In 1989, the European Working Group on Echocardiography proposed a morphological classification and described three patterns of right heart thrombi [4, 5]. Type A thrombi, reported as the most common, are serpiginous worm-like in appearance, freely mobile within the heart chambers, and usually associated with deep vein thrombosis and pulmonary embolism. Type B thrombi are non-mobile, ovoid in shape, firmly attached to the chamber wall, and are believed to form in situ in association with underlying cardiac abnormalities. Finally, type C thrombi are rare, share a similar appearance to atrial myxoma, and are highly mobile. Trans-esophageal echocardiography (TEE) offers a better evaluation of the thrombus and should be considered when TTE is inconclusive; it can determine precisely its location especially in sites as the pulmonary artery or patent foramen ovale.
This lady was clearly diagnosed as having flaring of nephrotic syndrome manifested by hypoalbuminemia and prothrombotic tendency with the formation of right atrial thrombi. Nephrotic syndrome (NS) is defined by the presence of a nephrotic range of proteinuria, peripheral edema, hypoalbuminemia, hyperlipidemia, and increased risk of venous thromboembolic event (VTE) complications. Reduced serum albumin is an independent risk factor for thrombotic events in patients with NS. The increased propensity of thromboembolism in nephrotic patients is postulated to be a result of increased excretion of antithrombotic factors by the affected kidneys and increased production of pro-thrombotic factors by the liver. Most cases of VTE associated with NS reported in the literature have a preceding diagnosis of NS [6].
Immune thrombocytopenia (ITP) comprises a heterogeneous group of disorders characterized by autoimmune-mediated platelet destruction and impairment of platelet production [7]. Despite thrombocytopenia, previous studies suggested an increased risk of VTE in ITP as compared with the general population. Thromboembolic events have been reported in up to 8% of patients with ITP, suggesting that thromboembolism requires special precaution in this patient group. Thromboembolism can be caused by a disease (i.e., pro-thrombotic disease state) after the introduction of ITP therapies such as corticosteroids or can occur in association with other diseases [7]. On the other hand, venous thromboembolism (VTE) is an important and potentially life-threatening complication in focal segmental glomerulosclerosis (FSGS) [8]. The prevalence of venous thromboembolism is approximately 10% in FSGS patients with nephrotic syndrome. Hemoconcentration and relapse of the nephrotic syndrome were risk factors for the development of VTE in FSGS [8].
The impaired RV contractility in this case may be explained by previous repeated embolic showers to the pulmonary circulation and consequently elevated pulmonary artery systolic pressure. Moreover, the RV filling could be affected by the huge thrombus. Surgical embolectomy, mechanical unloading of the RV, and optimum post-operative anticoagulation contributed to the improvement of RV contractility postoperatively.
Treatment options for RHT include anticoagulation therapy, systemic thrombolysis, and surgical embolectomy. The optimal therapeutic approach is still a subject of debate. In the European Cooperative Study, the mortality rate was reported to be 60% for anticoagulated patients, 40% for those treated with thrombolytics, and 27% for those submitted to surgical procedures, which suggests the surgical approach to the most effective [5]. The largest meta-analysis to date was presented by Athappan et al. in 2015. It included 328 patients of whom 70 patients received anticoagulation, 122 patients received thrombolysis, and 120 patients had surgical embolectomy. The highest mortality rates (90.9%) were reported for patients who were left untreated. The mortality associated with anticoagulation alone was significantly higher than surgical embolectomy or thrombolysis (37.1% vs 18.3% vs 13.7%, respectively). In hemodynamically unstable patients, survival probability was higher in patients receiving thrombolysis (81.5%) than in patients treated with surgical embolectomy (70.45%), and both were far higher than anticoagulation alone (47.7%) [9]. Data on catheter-based interventions are few.
As regards surgical embolectomy, it has been specifically recommended in patients with right heart thrombi straddling the interatrial septum through a patent foramen ovale [10]. The limitations of this approach include the lack of availability of surgical expertise, an inherent delay while preparing for surgery, depressant effects of anesthetic drugs and cardioplegia, and the inability to remove co-existing peripheral pulmonary thrombi.
In the recent era, the widespread availability of multislice CT scanning facilitated rapid noninvasive detection of central pulmonary embolism amenable to embolectomy in many of patients [11], thus avoiding potential complications of conventional contrast pulmonary angiography. Rapid transport to the operating room is also a cornerstone of the management strategy. In critically ill patients with massive pulmonary emboli or floating right heart thrombi, a pulmonary embolism response team (PERT) approach [12], should always be considered where a multidisciplinary team involving a cardiologist, radiologist, cardio-thoracic surgeon, and radiologist shall determine the management strategy. In some instances, extracorporeal membrane oxygenation (ECMO) and/or surgical pulmonary embolectomy may be life-saving interventions.
On the other hand, thrombolytic therapy is a simple, rapid, readily available therapy, which can dissolve the thrombus at different locations (cardiac, pulmonary, and peripheral). Besides the risk of major bleeding, thrombolytic therapy may be associated with a postulated risk of clot fragmentation and migration, complete pulmonary embolization, or recurrent PE following the partial dissolution of the venous thrombus.
According to the European Society of Cardiology ESC 2019 guidelines of acute pulmonary embolism, our patient was considered to be at intermediate high risk (sPESI ≥ 1, plus impaired RV, and positive troponin). A higher risk was estimated due to the huge RA thrombus and the presence of PFO. Moreover, the patient sustained cardiac arrest and acute myocardial infarction due to paradoxical embolism. The arrest was initially suspected to be due to massive pulmonary embolism, but this was specifically excluded by multislice CT. So, the most probable explanation of the cardiac arrest is obstruction of the right ventricular inflow by the huge oscillating right atrial mass. Though our patient presented during the weekend, a time notorious for increased in-hospital mortality from many diseases including PE [13], and the availability of a well-trained multidisciplinary team was crucial for successful management. The care of hemodialysis and fluid balance was taken over by a nephrologist. Finally, the use of ECMO in this particular case was also a great aid in unloading both the stunned right and left ventricles in the early post-operative period.