for people ages 18 years and up (full criteria)
Healthy Volunteers
healthy people welcome
at San Francisco, California
study started
estimated completion
Principal Investigator
by Gregory M Marcus, MD, MASDavid Rosenthal, MD
Photo of Gregory M Marcus
Gregory M Marcus



Atrial fibrillation (AF) and heart failure (HF) are morbid, costly, and incompletely understood diseases that have reached epidemic proportions worldwide. A dose-dependent relationship exists between premature atrial and ventricular contractions (PACs and PVCs) and development of AF and HF, respectively. Identifying and understanding the mechanisms of additional modifiable risk factors for ectopy has the potential to markedly reduce the healthcare burden of these diseases. In considering how to modify the prevalence of these ectopic beats, the investigators believe common exposures in daily life are prime candidates. Current guidelines suggest that caffeine may be an important trigger for frequent ectopy, although large population-based studies have not demonstrated an association between caffeine consumption and development of clinically significant arrhythmias. No study has employed an actual randomization intervention to assess the effects of caffeine on cardiac ectopy. Utilizing the Eureka platform, the investigators plan to utilize the N-of-1 strategy to rigorously investigate the real-time effect of caffeine intake on ectopy.


For two weeks, participants will be asked to wear a continuously recording heart monitor and utilize the Eureka mobile application. On the Eureka app, participants will be able to track caffeine consumption and answer questions about mood and sleep. Participants will also receive their randomization assignment through Eureka. Participants will be asked to modify caffeine intake habits in two-day blocks; these assignments are either a) to consume caffeine for one day, then avoid caffeine the next day, or b) to avoid caffeine for one day, then consume caffeine the next day. Participants will also be given a wrist-worn fitness device (Fitbit), to track sleep, step counts, and heart rate data.


Premature Atrial Contractions Premature Ventricular Contractions Caffeine Coffee Arrhythmias Palpitations Cardiac ectopy PACs PVCs Premature Birth Ventricular Premature Complexes Atrial Premature Complexes Start: On Caffeine Start: Off Caffeine


You can join if…

Open to people ages 18 years and up

  • Able to read and write in English
  • Has a smartphone
  • Is willing to receive message reminders from study
  • Drinks caffeinated coffee or espresso drinks
  • Is willing to abstain from caffeinated products when instructed
  • Is willing to provide saliva sample for analysis of genetic variants related to caffeine metabolism

You CAN'T join if...

  • Is taking an anti-arrhythmic, beta-blocker, or calcium channel blocker
  • Has a pacemaker or ICD


  • University of California, San Francisco
    San Francisco California 94143 United States

Lead Scientists at UCSF

  • Gregory M Marcus, MD, MAS
    CLINICAL Dr. Gregory Marcus is a specialist in the treatment of arrhythmias, including mapping and catheter ablation for atrial fibrillation, supraventricular tachycardias and ventricular arrhythmias. He is also an expert in pacemaker, biventricular device and defibrillator implantation. RESEARCH Dr. Marcus is Associate Chief of Cardiology for Research at UCSF Health.
  • David Rosenthal, MD
    Clinical Fellow, Medicine. Authored (or co-authored) 17 research publications.


in progress, not accepting new patients
Start Date
Completion Date
University of California, San Francisco
Ventricular Premature Complexes Treatment & Management Ventricular Premature Beats
Study Type
Last Updated