Background: Many patients with peripheral artery disease are unable to achieve healthy lifestyle after revascularization. There is evidence that rehabilitation program could result in decreased re-admission, reduced cardiometabolic risk factors and improved quality of life.

Aim: This first randomized controlled trial to examine the effectiveness of mobile phone text message-based rehabilitation on low density lipoprotein (LDL), Ankle Brachial Index (ABI), healthy lifestyle behaviors and quality of life for patients after revascularization. Methods: This is a 6 months randomized controlled trial. It is hypothesized that message-based rehabilitation program will be effective in improving the low density lipoprotein (LDL), Ankle Brachial Index (ABI), healthy lifestyle behaviors and quality of life for patients with peripheral artery disease after surgical revascularization. A total of 160 participants will be recruited for the study. The participants will be randomly divided into intervention and control groups. Both intervention and control groups will receive face-to-face lifestyle adherence counseling and booklet at baseline. The intervention group will receive 4 mobile phone messages per week for 24 weeks.

All participants will be asked to fill in the questionnaires at the baseline, 6-week and 6-month follow-up in Surgical Out Patient Department (SOPD). Participants' blood results of low density lipoprotein (LDL) at the baseline and at 6-month follow-up will be retrieved from Computer Management System in SOPD The primary outcomes are the fasting LDL levels at 6 months. Secondary outcome are Ankle-Brachial Index (ABI), BMI, Fasting glucose level, HDL level, Total cholesterol level, self-reported adherence to healthy lifestyle behaviours, quality of life and smoking status.

Participants: The target participants of this study are peripheral artery disease patients who have received revascularization in the Surgical Department of a regional hospital in Hong Kong. The eligible participants are Chinese, aged 50 years or above, and with medical record of peripheral artery disease with revascularization done in the past 6 months. The participants should be able to receive and read Chinese texts from their own mobile phones and are available to come back for a 6-month follow-up for lifestyle counselling. The potential participants will be excluded if they refuse to provide an informed-consent form or if they have medical records stating their lack of capacity to provide informed consent. The recruitment procedure will take place in Department of Surgery in a regional hospital.

Study setting: The study will be conducted in the Surgical Department of a regional hospital in Hong Kong.

Background Peripheral artery disease (PAD) is a circulatory disease which associated with narrowing of arteries in the lower limbs. It is also a common atherosclerotic vascular disease affecting 3-12% of the global population [1]. With aging of the global population and increasing industrialization, PAD is expected to increase further in the next few decades. Worse of all, PAD increases risk of coronary, cerebrovascular complication including death [2]. So secondary prevention is essential for patients with PAD especially after revascularization.

There is robust evidence that the secondary prevention of peripheral artery disease can be achieved by lifestyle modification [3-4]. The American Heart Association (AHA) recommended that smoking cessation, glycemic control and structured exercise are import elements of care for patient with PAD [5]. Despite the need of secondary prevention and the evidence-based guidelines from AHA, there is no structured rehabilitation program for PAD patients in Hong Kong. Recent studies reported secondary prevention of PAD mainly focus on exercise and medication therapy. However, a single lifestyle behavioral change could not address the needs of the patients who have multiple lifestyle risk factors. Since many PAD patients have more than one lifestyle risk factor, the rehabilitation program targeting multiple lifestyle behavioral changes will be more benefit to the at risk patients.

Mobile-rehabilitation is a new concept to deliver the rehabilitation program. Center-based rehabilitation is well evidenced to reduce mortality, unplanned hospital admissions and improve quality of life and psychological well-being of the patients [6]. However, its benefits is limited by low referral rate and inaccessibility of program site [7]. Mobile phone messaging can be used to motivate and reinforce the lifestyle behavioral changes. It can also prevent patients from relapsing to the previous unhealthy lifestyle behavioral stage. Current studies show a positive result of using texting to promote healthy lifestyle behaviors among adults with cardiovascular disease [8-9]. Considering that the mobile-phone penetration rate in Hong Kong is about 96.1% [10], the use of texting can be an innovative and cost-effective tool to promote a healthy lifestyle and improve quality of life of PAD patients.

To the best of the author's knowledge, there have been no Randomized Controlled Trial (RCT) of a stand-alone mobile phone message-based rehabilitation program designed to help peripheral artery disease patients. This is the first randomized controlled trial to examine the effectiveness of message-based rehabilitation on cardiometabolic risk factors for PAD patients who have received surgical revascularization. The transtheorectical model (TTM) [11] will be used as a framework for conceptualizing the process of behavior change. This model is well-suited to this messaging-based intervention as it allows understanding of participants' processes and dynamics of behavioral changes.

2. Aim This single-blinded randomized controlled trial aimed to evaluate the effectiveness of the message-based rehabilitation on fasting low density lipoprotein (LDL) level, Ankle-Brachial Index (ABI), healthy lifestyle behaviours, quality of life and smoking status for PAD patients who have received revascularization.

3. Research hypothesis The research hypothesis is that the message-based rehabilitation program improve the LDL, ABI and the cardiometabolic risk factors of peripheral artery disease (PAD) patients who have received revascularization.

4. Methodology 4.1 Study design This pilot randomised controlled trial aimed at examining the effectiveness of message-based lifestyle intervention. Peripheral artery disease patients who have received revascularization in the past 6 months, are randomized into 2 groups. The total sample size will be 160. Both intervention and control groups will receive face-to-face lifestyle adherence counseling and booklets at baseline. The intervention group will receive 4 mobile phone messages per week for 24 weeks. The messages are motivational advice to support lifestyle behavioral modification in various stages of behavioral changes. All participants will be follow up at 6-week and 6-month in Surgical Out Patient Department. Participants' ABI, lifestyle behaviors and quality of life will be assessed at baseline, 6- week and 6-month follow-up. Participants' fasting low density lipoprotein (LDL) level at baseline and at 6-month follow up will be retrieved from Computer Management System with approval of Dr. Leung Siu-kee, Chief Of Service Department of Surgery Tuen Mun Hospital. At least ten participants from intervention group will be purposively selected for individual face-to-face semi-structured interview to evaluate the mobile phone-based rehabilitation program at 6-month follow-up.

4.2 Study outcomes

Primary outcomes:

- Fasting blood low density lipoprotein (LDL) level

Secondary outcome:

• Smoking status
• Readiness for behavioural changes
• Health related Quality of life
• Self-reported walking physical exercise (session per week)
• Self-reported serving fruits and vegetables consumed per day
• BMI
• Fasting glucose level
• HDL level
• Total cholesterol level
• ABI

4.3 Study setting The study will be conducted in the Department of Surgery in Tuen Mun Hospital

4.4 Sampling method Probability sampling (simple random sampling) will be adopted for this study. Simple individual randomization method by sequentially numbered, opaque sealed envelopes (SNOSE) will be used to ensure the PI and participants will be concealed from the allocation sequence. The trained research assistant will prepare 160 identical, opaque, sealed, A5-sized envelops, with a unique 3-digit serial number on the cover of each envelope as an identifier. Half of them will each contain a card indicating "intervention" and the other half, " control". After consent, the trained research assistant will open an envelope according to the sequence of the serial number and assign participant to either "intervention" or "control" group. The envelop must be opened according to the serial number. All others will not know the group allocation before the envelope is opened. Frequent checks (at least weekly) of these numbers will be done to ensure no deviation.

4.5 Sample size Sample size will be determined according to power (1-β), type 1 error (α), and effect size. The mean effect size of lifestyle intervention from a previous study is 0.4, which is a medium effect size according to Cohen 1998 [12]. Thus, an effect size of 0.4 was used in the calculations. To achieve the conventional level of 80% power and α= 5%, the sample size will be 128. The attrition rate in previous studies ranged from 16%-20%. A total of 160 participants will ultimately be required; 80 participants will be randomized to either intervention or control group.

4.6 Study intervention The message-based lifestyle intervention consists of three parts. Both the intervention and control groups will receive Parts I and II. Only the intervention group will receive Part III, which is the mobile phone messaging.

Part I: Conduct an individualized healthy lifestyle education The first part is face-to-face individual health education with supportive brief counselling. It consists of the identification of lifestyle risk factors and modification strategies for secondary prevention of PAD. This counselling service will be provided by Site Supervisor, Mr. Ng Hoi Wa. A measurable and realistic lifestyle modification plan will be established together with the client and the site supervisor.

Part II: Develop a healthy lifestyle booklet The second part is a reinforcement tool for face-to-face education. The research team will develop a booklet includes misconceptions, maladaptive beliefs, facilitators and barriers of healthy lifestyle modification.

Part III: Perform mobile phone-based messaging The trained research assistant will deliver the messages to the participants of the intervention group for 24 weeks throughout the study. The messages will act as a reinforcement to increase self-awareness about health-promoting behaviour and develop the desire for competence in achieving a healthy lifestyle.

5. Data collection The quantitative data will be collected by using questionnaires. The trained research assistant will explain the nature and purpose of the research to the potential participants in interview room in Department of Surgery. The eligible participants are requested to sign the informed-consent forms and reminded that their participation is voluntary. The participants are also requested to fill in two questionnaires, Patient Activation Measure [13] & Short Form 12 version 2 (SF12v2) [14], at the baseline, 6-week and 6-month follow-up. The participants' blood result of fasting low density lipoprotein (LDL) level will be retrieved from computer management system in Department of Surgery. Face-to-face individual semi-structured interviews will be conducted to collect qualitative data.

6. Data analysis Quantitative data will be analysed using International Business Machines Corporation(IBM) Statistics is leading statistical software (SPSS) version 22.0 [15]. The descriptive measures of all participants will be summarised by percentage, mean, and 95% confidence interval (CI), as well as compared for between-group differences. The t-test will be conduct to compare the differences in continuous variables between the intervention and control groups.

The qualitative data will be audio-recorded and analysed by thematic analysis. Seven open-ended questions will be used in the semi-structured interviews.

1. How do you feel about the mobile phone text message-based rehabilitation?
2. What factors encouraged you to participate in Peripheral Artery Disease Rehabilitation program?
3. What factors discouraged you from participate in Peripheral Artery Disease Rehabilitation program?
4. How did the mobile phone text message-based rehabilitation facilitate your participation in lifestyle modification?
5. How easy did you find following the lifestyle advice from the mobile phone text message?
6. How difficult did you find following the lifestyle advice from mobile phone text message?
7. Any suggestions on how to improve and promote the rehabilitation for patients with peripheral artery disease?

Inclusion Criteria:

Aged above 50 Clinical diagnosis of peripheral artery disease Received revascularization in the past 6 months. Must be able to receive and read Chinese messages from their own mobile phones Must be able to come back for a 6-week and 6-month follow-up for lifestyle counselling and blood sample taking.

Exclusion Criteria:

Refuse to provide an informed-consent form. Clinical diagnosis of lack of capacity to provide informed consent.