Nearly everything published about these drugs points the same way. This does not, and it concerns a drug most sellers on this roster stock. It is also much weaker evidence than a headline would make it sound, and both of those facts have to survive to the end of the page.
What was pooled
Ten randomized controlled trials of tirzepatide in adults with overweight or obesity, 6,515 people in total, of whom 4,491 — 68.9% — were randomized to the drug. [1] The analysis was Bayesian, so its uncertainty ranges are credible intervals rather than confidence intervals, and it looked at three nested categories of heart rhythm problem.
For atrial fibrillation the pooled odds ratio was 2.20, with a 95% credible interval from 0.81 to 6.75. For atrial arrhythmia more broadly, 2.16, credible interval 0.90 to 5.87. For any arrhythmia at all, 1.84, credible interval 1.04 to 3.90.
How to read intervals that wide
A range from 0.81 to 6.75 is not a measurement of anything. It is consistent with the drug very slightly reducing atrial fibrillation and with it raising the odds nearly sevenfold, and it cannot distinguish between those. Intervals get that wide when there are very few events, which is what you would expect from arrhythmia in weight-loss trials that were not designed to look for it.
So the two narrower categories found nothing that can be called a finding. The broadest one did — barely, with a lower bound of 1.04. Anything that close to the line is a result whose significance could be undone by one more trial in either direction, and what an interval includes decides more here than the point estimate does.
What would make this more than a signal
A trial with arrhythmia as a prespecified endpoint, monitoring designed to catch it, and enough events to produce an interval narrower than a factor of eight. None of that exists. What exists is adverse-event reporting pooled after the fact from trials built to measure weight.
There is also a plausible confounder that runs in an awkward direction. Rapid weight loss, electrolyte shifts and a rising heart rate are all associated with these drugs, and all have some relationship to rhythm. Whether any of that is doing the work is not something a pooled adverse-event count can answer, any more than a trial population answers questions about a clinic population.
What to do with it
Not stop taking a prescribed drug on the strength of it. Three wide intervals from pooled adverse events are not a reason to change treatment, and that decision belongs to a prescriber who knows your heart history.
What it is worth is a question. If you have had atrial fibrillation, palpitations, or any rhythm diagnosis, that belongs on an intake form and in front of a clinician before starting — and it is precisely the kind of history a telehealth questionnaire may not ask about, which the census of what sellers leave unasked counts from the other side.