NOACs preferred over VKAs for AF, stroke management in Asians
Nonvitamin K antagonist (non-VKA) oral anticoagulants (NOACs) offer better outcomes than VKAs in Asian patients for the prevention of atrial fibrillation (AF)-associated stroke, according to data presented at the Asian Pacific Society of Cardiology Congress (APSC) 2017 held in Singapore.
“[The decreased] haemorrhage associated with NOAC vs warfarin [reflects the] strength of NOAC … among Asians,” said Dr Lau Chu-Pak from The University of Hong Kong in Hong Kong.
The efficacy of NOACs in reducing AF risk was shown in the landmark meta-analysis of the RE-LY*, ROCKET AF**, ARISTOTLE***, and ENGAGE AF TIMI 48**** trials comprising 8,928 Asians (5,250 on NOACs and 3,678 on VKAs) and 64,033 non-Asians (37,800 on NOACs and 26,233 and VKAs). [Stroke 2015;46:2555-2561]
Compared with non-Asians, Asians had a lower risk of stroke or systemic embolism (odds ratios [ORs], 0.65 vs 0.85; pinteraction=0.045), major bleeding (ORs, 0.57 vs 0.89; pinteraction=0.004), haemorrhagic stroke (ORs, 0.32 vs 0.56; pinteraction=0.046), and intracranial haemorrhage (ORs, 0.33 vs 0.52; pinteraction=0.059) with standard-dose NOACs vs VKAs.
These findings were supported by another study showing a significantly reduced incidence of intracranial haemorrhage with the NOAC dabigatran vs the VKA warfarin in Asians (0.32 percent vs 0.74 percent [4th quartile]). [Stroke 2015;46:23-30]
“Even [in] the best quartile of warfarin treatment … dabigatran [had] a better outcome in terms of cerebral haemorrhage than in non-Asians,” said Lau.
However, these results are in contrast with previous findings of diminished effectiveness of standard-dose NOACs in reducing bleeding events. [Int J Cardiol 2013;167:1237-1241; Lancet 2014;383:955-962].
In another study involving nonanticoagulated Chinese patients aged 50–64 years, despite a CHA2DS2-VASc# score of 0–1 which equates to a 0.6 percent annual thromboembolic threshold, the annual stroke risk was 1.78 percent. [J Am Coll Cardiol 2015;66:1339-1347] “[The] dramatic jump [in] the risk of having stroke or thromboembolism … [was] way beyond the threshold for oral anticoagulant use,” said Lau.
Nonetheless, the 2016 European Society of Cardiology Guidelines for AF management favour the use of NOACs over VKAs “when oral anticoagulation is initiated in a patient with AF who is eligible for a NOAC”.
Lau also underscored ethnicity as a probable contributing factor in the decreased incidence of AF in Asians, citing a substudy of the ASSERT***** trial revealing a low AF incidence in Black Africans, Chinese, and Japanese participants compared with Europeans. [J Cardiovasc Electrophysiol 2013;24:381-387]
However, Lau pointed out that the AF risk profile may not be entirely attributed to ethnic differences. Other risk factors such as undiagnosed or undertreated hypertension, thyroid dysfunction, and intracerebral atherosclerosis warrant further consideration, he added.