Have you considered that whatever you're taking the Zithromax for could be the reason for your recent arrhythmia? Have you had a prior adverse reaction to mycins? I'd report this to the physician that presribed the Z-pak and let him make the call.
I was taking it for Chlamydia trachomatis infection...
Both are associated with cardiac arrhythimas, but is uncommon with Azithromax. Definitely talk to the doc.
I was also just taking a 5 day dose pack of azithromycin for a sinus infection. I started having heart palpatations as well. I have tachycardia anyways so I didn't really associate it with the medicine. It really started worrying me when my left arm started feeling weak and tingling. This usually also happens when I have an SVT attack but it goes away quickly. This tingling lasted all day. My heart palpatations were more frequent as well. I did some researching about azithromycin and found it can cause heart palpatations. I didn't take my last dose because I was scared too and the heart palpatations stopped. My arm feels normal now too. However I'm still feeling dizzy. I'm going to see my doctor today about it to see what he thinks. You should as well.