MR-tomographische Evaluation der Inzidenz zerebraler Embolien bei Patienten mit Vorhofflimmern und linksatrialen Thromben

Zusammenfassung

Ziel: Prospektive Evaluierung 1) der Prävalenz zerebraler Embolien mittels MRT- und Diffusionsbildgebung (DWI) bei Patienten (Pat.) mit neu diagnostiziertem Vorhofflimmern (AF) und gleichzeitigem Nachweis eines linksatrialen (LA-) Thrombus, 2) der Größenänderung der LA-Thromben innerhalb eines Jahres unter Antikoagulation mittels transösophagealer Echokardiographie (TEE) sowie 3) der Inzidenz neuer zerebraler Embolien unter 12-monatiger kontinuierlicher Antikoagulation. Methode: Untersucht wurden a) 32 Pat. mit neu diagnostiziertem AF, echokardiographischem Nachweis eines LA-Thrombus und Beginn einer antikoagulativen Therapie sowie b) eine Kontrollgruppe von 19 Pat. mit neu diagnostiziertem AF ohne LA-Thrombennachweis und äquivalenter Antikoagulationstherapie. Prospektiv und seriell wurden in beiden Gruppen durchgeführt: a) eine MRT-/DWI des Hirns zur Detektion zerebraler Embolien (Wochen 0, 4, 8, 12, 20, 28, 36, 44, and 52), b) eine TEE zur Größenbestimmung der LA-Thromben (Wochen 0 und 52) und c) eine neurologische Statuserhebung (Wochen 0, 20 und 52). Ergebnisse: In der Studiengruppe (AF mit LA-Thrombus) zeigten 11 von 32 Pat. (34 %) akute (n = 8) oder ältere (n = 3) zerebrale Embolien in der initialen MRT. Im einjährigen Verlauf unter Antikoagulation wurden bei 4/32 Pat. (13 %, davon n = 2/4 Pat. neurologisch symptomatisch) mittels MRT-/DWI neue zerebrale Embolien (n = 12) nachgewiesen. In der Kontrollgruppe (AF ohne LA-Thrombus) wurden sowohl in der initialen MRT (n = 1/19, 5 %) als auch im 12-Monats-Verlauf (n = 0/19, 0 %) signifikant (p < 0,01) weniger zerebrale Embolien detektiert. Nach einem Jahr waren noch 37 % der LA-Thromben echokardiographisch nachweisbar. Schlussfolgerung: 1) Die Inzidenz klinisch asymptomatischer zerebraler Embolien bei neu diagnostiziertem AF mit gleichzeitigem linksatrialem Thrombennachweis ist wesentlich höher als die Inzidenz klinisch manifester Embolien. 2) Neue zerebrale Embolien traten trotz therapeutischer Antikoagulation bei 13 % der Pat. im Verlauf auf. 3) Nur 63 % der Vorhofthromben lösten sich unter 12-monatiger Antikoagulation vollständig auf.

Abstract

Purpose: Patients (pts.) with atrial fibrillation (AF) and atrial thrombi are known to have an increased risk for cerebral embolism. However, little is known about the clinical course of atrial thrombi and the incidence of cerebral embolism in those patients during anticoagulation therapy. The high sensitivity of MR imaging (MRI) including diffusion-weighted imaging (DWI) suggests that this technique could provide an improved estimate of cerebral embolism associated with the presence of left atrial thrombi. The aims of this prospective study were to evaluate 1) the prevalence of clinically silent and apparent cerebral embolism in pts. with newly diagnosed AF and atrial thrombi using MRI/DWI, 2) the long-term fate of atrial thrombi under continues anticoagulation therapy and 3) the incidence of cerebral embolism during a follow-up period of 12 months with continuous anticoagulation therapy. Materials and Methods: The study group consisted of 32 pts. with 1) newly diagnosed AF and evidence of left atrial (LA) thrombi detected by TEE and 2) a new start of anticoagulation therapy [International Normalized Ratio (INR) 2.0 - 3.0]. 19 pts. with 1) newly diagnosed AF and no evidence of atrial thrombi and 2) an equivalent anticoagulation regimen served as the control group. In both groups a) MRI/DWI studies of the brain (weeks 0, 4, 8, 12, 20, 28, 36, 44, and 52), b) transesophageal echocardiographic studies (TEE) for assessment of LA-Thrombi (weeks 0 and 52) and c) clinical neurological assessments (weeks 0, 20 and 52) were performed. Results: In the study group (AF and LA-Thrombi) 11 out of 32 pts. (34 %) displayed signs of acute (n = 8) or chronic (n = 3) cerebral embolism in the initial MRI studies. In 4 out of 32 pts. (13 %), MRI/DWI depicted new or additional cerebral emboli (n = 12) during the follow-up period despite continuous anticoagulation therapy. 2 (n = 2/4; 50 %) of these patients had clinically apparent neurological deficits. In the control group 1 out of 19 pts. (5 %) showed evidence of chronic cerebral embolism as assessed by MRI/DWI at the beginning of the study (week 0). No embolic cerebral lesions were detected during the 12-month follow-up. Within 12 months only 63 % (n = 20/32) of LA thrombi in the study group resolved completely under anticoagulation. Conclusion: 1. The incidence of clinically inapparent cerebral emboli in pts. with newly diagnosed AF and atrial thrombi is much higher than the incidence of clinically apparent emboli and has been underestimated in the past. 2. New cerebral embolism may occur even with continued effective anticoagulation therapy in 13 % of pts. 3. Only 63 % of atrial thrombi resolve completely within 12 months under anticoagulation therapy.

Key words

MR imaging - atrial fibrillation - atrial thrombi - cerebral embolism - cerebral infarction - diffusion-weighted imaging

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