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This case report describes a patient with thromboemboli trapped in the Chiari network within the right side of the heart and resistant to thrombolysis. The right atrial masses were completely removed under cardiopulmonary bypass. Histological evaluation confirmed a mixed thromboemboli, with thrombus structures showing signs of organisation and surrounded by a fibrous capsule. The plasma level of the plasminogen activator inhibitor type-1 (PAI-1) was 50% higher than the normal upper limit. In this presented case, the Chiari network displayed a protective function but the expansion and organisation of the thromboembolus found there made it resistant to lytic treatment. Another important factor that could have influenced the resistance to thrombolysis was the high level of PAI-1.
The ECG presence of right heart thromboemboli during a pulmonary embolism is described in the literature as occurring in about 4% of patients, with a high related rate of massive pulmonary embolism and short-term mortality.1 2 Unfortunately, there is no consensus regarding the treatment strategy for such patients. However, favourable results have been reported with thrombolysis.3
Here, a well-documented case report is presented, which describes a patient with thromboemboli trapped in the Chiari network within the right side of the heart and resistant to thrombolysis.
A 43-year-old woman presented in hospital with pain and asymmetric swelling of her left leg, which had been accompanied by shortness of breath during physical activity over the previous 2 weeks. At presentation, she was a smoker, had a long history of taking contraceptive medication and she was on substitution treatment for hypothyreosis. Her history also included two spontaneous abortions. The previous year, she had been admitted to hospital for pyelonephritis complicated by septic shock; during this hospital stay the patient underwent transthoracic ECG where a Chiari network in the right atrium was found. The patient's mother had suffered from a postoperative pulmonary embolism at the age of 50 years.
On physical examination, the patient was stable with a blood pressure of 140/80 mm Hg, heart rate 80 bpm; her height was 165 cm and weight was 68 kg. Except for the left leg oedema, with positive Homan's sign, there were no other pathological findings. No signs of right heart failure were present. A laboratory blood examination found d-dimers, mild leucocytosis and above normal levels of C reactive protein. A ventilation-perfusion lung scan confirmed a bilateral pulmonary embolism. The source of the embolus was established by Doppler ultrasonography, which documented a femoral-popliteal venous thrombosis in the left leg.
The patient was haemodynamically stable, so treatment with a full-anticoagulation dose of unfractioned heparin (UFH) was started. A transthoracic ECG was performed, which showed two large stationary masses within the right atrium. Their structure and density were suggestive of emboli (figure 1, video 1). One mass was protruding from the right atrium through the tricuspid valve into the right ventricle, but without causing a gradient; systolic functions of both ventricles were normal and there were no signs of right heart overload. Transoesophageal ECG described the hypoechogenic masses as well-circumscribed (23 × 15 mm and 14 × 20 mm) with homogenous structure. The masses appeared to stem from the posterior wall of the right atrium and were caught in the Chiari network (video 2).
Both structures were assessed as thromboemboli lodged in the right atrium. Thrombolytic treatment with an intravenous infusion of 100 mg recombinant tissue-type plasminogen activator (rt-PA), over a period of 2 h, with continuous ECG monitoring was performed. Following rt-PA treatment, full dose UFH was restarted. In subsequent control ECGs, the two masses found to persist without any change in their shape or size. MRI further confirmed the thromboembolic aetiology of these right atrial masses (figure 2). With respect to the high risk of a fatal pulmonary embolism and the inefficacy of the most potent lytic strategy, surgical embolectomy was indicated. Preoperatively, a control Doppler ultrasonography documented the persistence of thrombotic materials in the veins of the left leg. Therefore, a temporary inferior vena cava filter was implanted prior to surgery.
The right atrial masses were completely removed under cardiopulmonary bypass (figure 3). Histological evaluation confirmed a mixed thromboemboli, with thrombus structures showing signs of organisation and surrounded by a fibrous capsule (figure 4).
The patient, with a positive family history of pulmonary embolism, had further known risk factors for venous thromboembolism—that is, cigarette smoking and use of oral contraceptive. Because of the high suspicion of thrombophilia, the patient was tested for thrombophilic disorders. A heterozygous methylenetetrahydrofolate reductase gene polymorphism was found and the plasma level of the plasminogen activator inhibitor type-1 (PAI-1) was 50% higher than the normal upper limit.
The patient was discharged home in good condition. She was placed on standard warfarin anticoagulation treatment. The patient also stopped cigarette smoking and discontinued with her contraception. One month after discharge, a control angiography of the vena cava showed persistence of thrombotic masses so the preoperatively implanted temporary vena cava filter was replaced by a permanent one.
Chiari anomalies in the human right atrium have been detected in 10.5% of autopsied hearts.4 The Chiari network is a web-like structure with a variable number of thread-like components. It is an embryological remnant, resulting from the incomplete resorption of the right sinus venosus valve and persistence of a filamentous tissue network.5 These filaments are attached to the wall of the right atrium in close proximity to the entrance of the inferior vena cava.4
Chiari malformation is not pathological and is rarely of clinical importance.5 6 The spider-web-like structure predisposes it to act as a filter for the inferior vena cava.7 However, the Chiari network can serve as a site of thrombus formation and also as a site where an embolus from the inferior vena cava can become lodged. Endocarditis that develops solely within a Chiari network has been described as well.8
In this presented case, the Chiari network displayed a protective function but the expansion and organisation of the thromboembolus caught there made it resistant to lytic treatment. Another important factor that could have influenced the resistance to thrombolysis was the high level of PAI-1. PAI-1 is the primary physiological inhibitor of plasminogen activation in blood. When PAI-1 plasma levels are elevated, the action of tissue plasminogen activator is depressed9 resulting in thromboembolic disorders.10 In addition, elevated pretreatment levels of PAI-1 may reduce the efficacy of thrombolytic treatment by preventing or retarding clot dissolution.11
The influence of impaired glucose metabolism or lipid disorders on PAI-1 plasma concentration was excluded in this patient. PAI-1 plasma levels partly depend on gene regulation.9 12 However, at present, genetic and environmental determinants of PAI-1 expression are incompletely understood.13 The human PAI-1 gene is located on chromosome 7 and contains nine exons and eight introns,12 and several polymorphisms have been described within the gene. The patient's DNA was tested for a common single-base-pair polymorphism (4 or 5 guanine bases) in the promoter region of the gene (4G/5G), but the presence of this variant allele was not confirmed: the patient was homozygous for the 5G allele (5G/5G genotype).
Unsuccessful results with thrombolysis have been described in 8% of patients with an acute massive pulmonary embolism.14 In these patients, emergency surgical embolectomies have led to better in-hospital outcomes when compared to repeated thrombolysis attempts.14 In cases where a patient, after surgical embolectomy, is at increased risk for recurrent pulmonary embolism, the insertion of a vena cava filter is of potential benefit.15
Competing interests None.
Patient consent Obtained.