Some studies have shown that excessive Vit D levels can be linked to AF, some have not. Regardless - the efforts that some people make to try and get their Vit D levels above even the fairly high level that OMS recommends are just being silly - more is not necessarily better. Note that the Coimbra Protocol which uses massive doses of Vit D is done under very strict medical supervision to avoid the complications that can result from excessively high Vit D levels. Inadequate Vit D levels are also identified as a risk factor for CVD.
Go and do some research on the other substances which need to be a part of high Vit D supplementation, especially magnesium and Vit K2. Magnesium is critical in maintaining heart rhythms and many people don't get enough magnesium. Vit D supplementation can also contribute to higher than normal blood calcium levels, and this is where a holistic approach to Vit D supplementation is necessary to ensure that calcium is "sent" to where it's needed and does not remain circulating in the blood stream where it can contribute to an increased risk for CVD. There are some OMSers who brush aside the research in this area and stay wedded to the mantra of "I get all I need from my WFPB diet", but that is a very one-eyed and uninformed perspective - not everybody can be as perfect as they believe they are.
I looked into all of this quite extensively when I first started supplementing with Vit D after my MS diagnosis but had problems which meant I had to stop the extra Vit D - and I wasn't taking vast quantities of it - only about 2,000 units a day and my blood levels were around 80 nmol/L. When I introduced magnesium and Vit K2 everything settled down and I had no further problems with taking Vit D of up to around 30,000 IU a week, split into daily doses. I now take 450mg Mag Ctirate and 2,000 IU of Vit D daily, plus 3 times a week I take 180mcg of Vit K2, and my Vit D levels are nicely stable with no "side-effects".