Here is the design of a clinical trial:

Official Title: Efficacy and Safety of Transcutaneous Auricular Vagus Nerve Stimulation for Frequent Premature Ventricular Complexes: A Randomized Controlled Trial

Included conditions:
- Premature Ventricular Complexes

Study Armgroups:
- {'label': 'TAVNS plus usual care', 'type': 'EXPERIMENTAL', 'description': 'TAVNS on Erzhong and Xin (Auricular Acupuncture Point with Vagus nerve distribution); Usual Care: usual medicine treatment for PVCs.', 'interventionNames': ['Device: Transcutaneous Auricular Vagus Nerve Stimulation (TAVNS)']}
- {'label': 'Sham-TAVNS plus usual care', 'type': 'PLACEBO_COMPARATOR', 'description': 'Sham-TAVNS on Erzhong and Xin (Auricular Acupuncture Point); the same acupoints as the treatment group without any current.\n\nUsual Care: usual medicine treatment for PVCs.', 'interventionNames': ['Device: Sham Transcutaneous Auricular Vagus Nerve Stimulation (Sham-TAVNS)']}

Interventions:
- {'type': 'DEVICE', 'name': 'Transcutaneous Auricular Vagus Nerve Stimulation (TAVNS)', 'description': 'Patients in TAVNS group will receive TAVNS and usual care. TAVNS will be performed on Erzhong and Xin (Auricular Acupuncture Point with vagus nerve distribution) for 6 weeks by using the Huato type SDZ-V stimulator; Usual Care: usual medicine treatment for PVCs.', 'armGroupLabels': ['TAVNS plus usual care']}
- {'type': 'DEVICE', 'name': 'Sham Transcutaneous Auricular Vagus Nerve Stimulation (Sham-TAVNS)', 'description': 'Patients in sham-TAVNS group will receive sham-TAVNS and usual care. Sham-TAVNS will be also performed on Erzhong and Xin (Auricular Acupuncture Point with vegas nerve stimulation) for 6 weeks by using a special Huato type SDZ-V stimulator. We cut the inner electric wire of the stimulator; therefore, there is no current output. Usual Care: usual medicine treatment for PVCs.', 'armGroupLabels': ['Sham-TAVNS plus usual care']}

Primary Outcomes:
- {'measure': 'the proportion of participants with a 50% decrease of PVCs from baseline', 'description': 'The PVCs will be assessed by a 24-hour Holter monitoring. The investigators will calculate the decrease of PVCs between baseline and week 6 (at the end of the treatment), then we will obtain the proportion of patients with a 50% decrease.', 'timeFrame': 'week 6'}

Please estimate the sample size based on the assumption: 
Two-tailed test with 90% power, 5% significance level, and 15% loss to follow-up rate.
Sample size calculation
        The null hypothesis is that there would be no difference between the two groups in the proportion of participants with aââ¥â50% reduction of PVCs from baseline after 6 weeks of treatment, and the alternative hypothesis is that there would be a significant difference between the two groups. In our pilot study, the proportion in taVNS and sham-taVNS groups were 58.3% and 21.1%, separately. Ninety participants are required (45 in each group) with a two-tailed test setting power as 90% and alpha as 5%, and considering the rate of loss to follow-up as 15%. To balance the three sites with two groups, 30 participants need to be enrolled in each site (15 per group in one site).