Short answer (plain English)
Retatrutide is investigational and in phase 2 obesity data it caused dose-dependent increases in heart rate that peaked around week 24 and declined thereafter (PMID: 37366315). Dehydration from GI side effects can amplify tachycardia; monitoring and a hydration plan matter.
References
- Retatrutide phase 2 obesity trial (PubMed): https://pubmed.ncbi.nlm.nih.gov/37366315/