I would say that Cat's Claw is psychoactive, at least in my experience. It makes me feel more flowy, less second-guessy. Maybe it's because I need it, because my system is out of balance from years of Lyme disease. I feel a definite energy boost from Cat's Claw.

I recently found out that it is an MAOI-B inhibitor.

Might this have any potentiation effect on other psychedelics?

What about mescaline-containing cacti? Might it make it riskier for the heart? I'm asking because my heart tissue has seen way above normal inflammation/damage from the Lyme, and I'm a little worried about it. I get strange cardiac pains, often.

I believe there are different strains of cat's claw, and some contrain a mild NMDA-antagonist as well, that is not present in other strains.

I have often used cat's claw myself as an admixture in ayahuasca brews. Never felt any side effects from it.

A bit off-topic, but...

While it is of course essential to consult a medical professional, and due caution should be exercised if you are using any other medications, combined tincture of hawthorn (Crataegus spp.) berries and flowers is a tried-and-tested, traditional herbal remedy of known efficacy for supporting the heart and circulation. Maybe it would be suitable for you - talk to a herbalist if you can. Hawthorn is a pretty safe remedy.

I used a local unidentified Cretaegus spp. for lyme carditis with success.
Had a soothing effect, and does seem to build over time. Used a normal strength (1/3 whole dried berry to vodka, volume wise), homemade tincture 3x daily.

The heart pains were very intense for something like 6 months and I was really afraid. Went to the emergency room once without insurance, and they didn't find anything after a heart x-ray. While there my grandmother though it could be lyme and suggested testing for it, as I had it as a child. They did not get back to me, but I requested the info and had my cousin who's a lab technician interpret the results (an antibody test Igg? I think?) which looked positive, so confirming my suspicions.
So I tried many herbs and changed my diet to less sugar, and the pain went away for the most part. Still some weirdness occasionally, but these days it's more maintenance than a raw struggle for life.

I've had good success with baikal skullcap for the nervous system disorders as well. It has a definite grounding and anti-anxiety effect immediately, and is rumored to also help in other systemic ways. Felt good to me.

Thank you! That's two votes for Hawthorn for Lyme heart troubles. I'll definitely look into it.

Cat's Claw contains a variety of active components, so the region where it's grown can have a significant effect in it's activity.

Some of these components are indole alkaloids, of the Corynanthine type. These are known to have adrenergic and serotogenic activity. (Also similar to mitragynine and reserpine)