Is Spirulina Safe?

Personally I've been taking spirulina for years and have never had an issue with it, until a few nights ago. I took several tablets of a popular brand of organic spirulina and, to make a long story short, spent the night in the emergency room. I experienced shortness of breath, rapid heart rate, in and out of awareness, weakness and shaking. It was absolutely horrific.

It's been a few days since then. I've been feeling significantly better since then and haven't touched spirulina, until a few hours ago. I decided to try just one tablet, and have been feeling the exact same symptoms, albeit to a far lesser extent (since my dose was far lower). Needless to say I've thrown out all of my spirulina on hand and canceled my order for more. I've decided that my spirulina days are OVER, and I'm moving on to chlorella.

My guess is that this was simply a bad batch of spirulina, since I've had great luck preciously with spirulina, and have been taking it for years with zero problems. Yet, I'm not willing to risk a bad batch sending me to the emergency room - or worse - again.