Perioperative Thrombozytenaggregationshemmung und Antikoagulation in der Herzchirurgie

Zusammenfassung

Die Bedeutung der Thrombozytenaggregationshemmung in der Therapie der koronaren Herzkrankheit ist unumstritten. Nach koronaren Ereignissen und Interventionen verbessert die Anwendung einer dualen Plättchenhemmung das Outcome von Patienten erheblich. Folgerichtig muss dieses Therapiekonzept in der Herzchirurgie fortgeführt werden. So wird die duale Therapie nach stattgehabtem Koronarsyndrom nur für die Operation selbst unterbrochen und daraufhin für 12 Monate nach dem Ereignis fortgesetzt. Gleiches gilt zur Prophylaxe einer In-Stent-Thrombose bei Patienten, die vor Operation bereits durch eine Intervention teilversorgt wurden, sofern die gestenteten Nativgefäße noch Teil der koronaren Blutversorgung sind. Schließlich verdichtet sich die Evidenzlage zur Gabe der dualen Therapie auch nach operativer Myokardrevaskularisation bei stabiler koronarer Herzkrankheit zur Verbesserung der Offenheitsrate der Bypassgefäße sowie zur Reduktion von thromboembolischen Ereignissen und kardiovaskulärem Tod. Besteht bei diesen Patienten überdies eine Indikation zur Antikoagulation, sollte nicht in allen Fällen eine Triple-Therapie, wie sie in den Leitlinien der großen Fachgesellschaften empfohlen wird, durchgeführt werden. Stattdessen ist ein vergleichbarer Schutz vor thromboembolischen Ereignissen bei gleichzeitig deutlich vermindertem Blutungsrisiko unter einer Doppeltherapie mit Clopidogrel und einem oralen Vitamin K-Antagonisten gegeben. Dennoch bleibt das primäre Ziel bestehen, eine Thrombusformation zu vermeiden. Um dieses Ziel zu erreichen, ist eine patientenindividuelle Entscheidung zum Umfang der Antikoagulation unabdingbar. Neuentwicklungen im Bereich mechanischer Klappen konnten zwar die Zielbereiche für die INR reduzieren, eine lebenslange Antikoagulation ist dennoch unbedingt erforderlich. Biologische Klappenprothesen und Anuloplastieringe sind insgesamt als wenig thrombogen einzustufen. Das größte Risiko besteht in den ersten 3 Monaten nach Operation und ist im Anschluss zu vernachlässigen. Bovine oder porzine Aortenklappenprothesen sind postoperativ durch niedrig dosiertes ASS adäquat therapiert. Werden die Atrioventrikularklappen rekonstruiert oder durch biologische Prothesen ersetzt, so bedarf es in den ersten 3 Monaten einer Antikoagulation durch Vitamin-K-Antagonisten. Im Anschluss kann jedoch auch hier auf ASS umgestellt werden. Studien über den Einsatz der neuen oral verfügbaren Thrombin- und Faktor-Xa-Antagonisten mussten abgebrochen werden. Bis auf weiteres werden sie daher keine Alternative zu Phenprocoumon darstellen.

Abstract

The impact of platelet inhibition in coronary artery disease is evident. Dual antiplatelet therapy (DAPT) after acute coronary events and percutaneous interventions significantly improved the results. Consistent with these findings the therapeutic concept of dual antiplatelet therapy has to be transferred into cardiac surgery. According to novel guidelines dual platelet inhibition is stopped only for surgery itself and continued for twelve months after acute coronary events. To avoid in-stent thrombosis patients postinterventionally should receive DAPT as long as the stented coronary vessel has not been surgically bypassed. Increasing evidence has become available that dual antiplatelet therapy reduces cardiovascular deaths, thromboembolic events and increases patency rates of bypass grafts when given after coronary bypass surgery performed in patients with stable coronary vascular disease. In case of concomitant indication for anticoagulation guidelines recommend triple-therapy. Nonetheless double-therapy (ADP-antagonists plus vitamin K-antagonist) has shown to be as effective as triple-therapy in prevention of thromboembolic events, while bleeding risks are reduced significantly. Avoiding thrombus formation is the primary objective. To reach this goal an individualized decision needs to be taken on the basis of the patientʼs medical history and comorbidities. New designs in mechanical heart valves limited thrombogenicity. However a strict anticoagulation is needed throughout life. The highest thrombogenic risks of bioprosthetic heart valves and annuloplasty rings can be seen during the first three months after surgery. Bovine or porcine aortic prostheses are anticoagulated adequately with low dose ASA. A three-month therapy with oral vitamin K-antagonists is necessary after bioprosthetic replacement or repair of the atrioventricular heart valves followed by low dose ASA. Ongoing studies investigating the use of new oral thrombin- or factor Xa-antagonists in patients after heart valve replacement surgery had to be terminated prematurely – hence they are not expected to become an alternative to warfarin after heart valve replacement surgery.

Schlüsselwörter

Antikoagulation - Thrombozytenaggregationshemmung - duale Thrombozytenaggregationshemmung - Triple-Therapie - Bypassoperation - Herzklappenoperation

Key words

anticoagulation - antiplatelet therapy - dual antiplatelet therapy - triple-therapy - coronary artery bypass grafting - heart valve surgery

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