Thread by @husam247

Today @JAMACardio published our study on potential risk/benefit of anticoagulation for #AFib pts aged 65-74 yrs w/out other CHADS2Vasc risk factors. This is one of the greatest areas of divergence of @SCC_CCS guidelines from @ACCinTouch @escardio
jamanetwork.com/journals/jamac…

This study was prompted by a patient with #afib who challenged me to justify my recommendation to anticoagulate her on her 65th birthday for rest of her life. She asked what her risk of stroke is if she chose not to anticoagulate & if it outweighs bleeding risk.

When stroke risk exceeds 0.9% per year, people with #atrialfib likely benefit from newer and safer bloodthinners (DOACs) but are unlikely to benefit from the older cheaper bloodthinner known as warfarin unless their stroke risk exceeds 1.7% per year.
ahajournals.org/doi/10.1161/CI…

An underappreciated fact - stroke risk in #atrialfibrillation has been steadily going down since CHADSVasc was developed, even for people who are not anticoagulated, likely related to detection of lower burden disease and better treatment of risk factors.
ahajournals.org/doi/10.1161/JA…

Lo and behold, I realized there were no data directly applicable to her. Most research treats all CHASVASc factors as identical WRT stroke risk. Importantly, there has been little distinction between the risk of stroke of someone who is 65 and someone who's 74 years of age.

So we used @icesontario data to address this gap. Our question was simple (despite the complicated methods - see editorial). It was what my patient asked: what is my risk of stroke without a bloodthinner? Does being a woman matter?
jamanetwork.com/journals/jamac…

tl;dr - the overall stroke risk was NOT high enough to warrant bloodthinners for all. For patients close to 65 years, risk was < 0.9% / yr, meaning they are less likely to benefit from bloodthinners, even if offered DOACs.

As patients got older, their risk of stroke rose steadily – in fact it more than doubled as they went from 66 to 74 years of age. However, stroke risk was not high enough to justify the risk and inconvenience of warfarin.

There was no difference by sex in this lower-risk group, consistent with emerging understanding of how sex interacts with other risk factors for stroke in AF.
ahajournals.org/doi/10.1161/CI…

Caveats galore - see limitations. This should not cause wholesale practice change. Observational study, needs replication in other jurisdictions. Take home message: need more nuance when discussing this decision w/ pts before putting them on blood thinner.

Thankful to @denniskomd for supervision along with phenomenal co-authors @Stats_research @HeartRPh A Pang, P Dorian, K Tu, S Singh. Couldn't have happened without funds from @HSF_science to me and @CIHR_IRSC to @denniskomd @WCHospital @PMunkCardiacCtr @UofT_DoM @UofTCardio