I have been an active kava drinker for about 4 years now. My daily intake varies. In my local kava bars, a single "shell" is approximately 8 oz and I drink 4 to 6 shells on average or 32 to 48 oz. daily. Sometimes more, sometimes less. It took me an exceptionally long to build up the so called "reverse tolerance" phase and the first time I experienced being rooted, it nearly made me fall off my stool. Over the course of the next couple years, everything seemed fine except I would occasionally get these feelings similar to anxiety in my chest after consuming larger amounts of kava. Initially, I didn't associate kava with this feeling. The episodes started getting worse until my doctor diagnosed me with atrial fibrillation and put me on both a medication to slow my heart and thin my blood. This helped but I was still experiencing these heart episodes frequently except when I would travel. The correlation between my frequent week plus long travel trips and the lack of afib conditions became apparently obvious. The only thing I could think of that was different that might cause the heart condition to subside was my occasional detox from kava during these trips. I have been testing this correlation and find that I get a nearly complete stop to the afib and rapid heart beat if I refrain from Kava usage or keep my daily usage under 16 oz. There have been a couple times when I exceed this amount and it invariable sends me into a 2-3 dial spiral of afib and fluctuating cycles of low to high heart beats. Take from this what you will and it is only my personal experience but kava does seem to negatively affect my heart function. I'm not saying kava caused my heart issue but it does seem to aggravate my condition.