An embolus in the right atrium caught in the Chiari network and resistant to thrombolysis.

Case report is presented, which describes a patient with thromboemboli trapped in the Chiari network within the right 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 organization and surrounded by a fibrous capsule. 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. In this presented case, the Chiari network displayed a protective function, but the expansion and organization of the thromboembolus caught there made it resistant to lytic therapy. Another important factor which could have influenced the resistance to thrombolysis was the high level of PAI-1. PAI-1 is the primary physiologic inhibitor of plasminogen activation in blood. Elevated pre-treatment levels of PAI-1 may reduce the efficacy of thrombolytic therapy by preventing or retarding clot dissolution. The patient's DNA was tested for a common single-base-pair polymorphism (four or five 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).