There have been some studies trying to link TNF inhibitors to a lower risk of CVD (cardiovascular disease), heart attacks, and strokes. Most of the studies I've read involved rheumatoid arthritis patients. I think results are mixed in those. There was a study released in 2015 noting a lower CVD risk in psoriasis patients. As for the sort of unique heart problems that spondylitis patients can develop, e.g. aortitis, aortic regurgitation/aortic valve inflammation, conduction abnormalities, I'm not aware of any large studies or trials looking at that. I've had this conversation with my cardiologist and what he told me was that cardiologists do not prescribe TNF inhibitors (or other biologics) precisely because there have been no good studies confirming their effectiveness for heart patients and conditions. Note that there are some case studies and very small studies addressing the effect of TNF inhibitors on a couple of types of vasculitis, Takayasu's Arteritis (TAK) and Giant Cell Arteritis. Those studies are mixed on the effectiveness of the TNF inhibitors in maintaining remission in TAK patients. If I recall correctly, the TNF drugs were not helpful to Giant Cell patients. But I'm not sure any of those studies are terribly valuable given their size. And I'm not sure they say anything at all about spondylitis-related inflammation's effect on the heart and vascular system, particularly the aorta. All these diseases do their damage via different mechanisms.
We're still waiting on the big clinical trial on TNF-a drugs and heart disease. I imagine Big Pharma would love to be able to market biologics as heart disease drugs (then everybody in the world will be on them); so hopefully we'll get some data soon.
Note that just because there's no conclusive data saying TNF-a drugs prevent heart damage doesn't mean TNF-a drugs don't prevent heart damage.