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Trial registered on ANZCTR


Registration number
ACTRN12617000983303
Ethics application status
Approved
Date submitted
30/06/2017
Date registered
10/07/2017
Date last updated
11/09/2018
Type of registration
Prospectively registered

Titles & IDs
Public title
The causes of bradycardia in athletes
Scientific title
The effects of ivabradine under autonomic blockade in endurance athletes.
Secondary ID [1] 292315 0
Nil known
Universal Trial Number (UTN)
U1111-1198-5373
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Bradycardia in athletes 303859 0
Condition category
Condition code
Cardiovascular 303217 303217 0 0
Other cardiovascular diseases

Intervention/exposure
Study type
Interventional
Description of intervention(s) / exposure
Intervention:
Autonomic blockade with single doses of intravenous metoprolol(0.2mg/kg) + intravenous atropine (0.04mg/kg) plus oral ivabradine 15mg
Exposure: endurance sport participation
A wash out period of at least 24 hours will occur before crossover to the control arm
Intervention code [1] 298488 0
Treatment: Drugs
Intervention code [2] 298489 0
Lifestyle
Comparator / control treatment
Control:
Autonomic blockade with single doses of intravenous metoprolol(0.2mg/kg) + intravenous atropine (0.04mg/kg) plus plus placebo (methylcellulose capsule)
Exposure control: non endurance sport athletes
A wash out period of at least 24 hours will occur before crossover to the
intervention arm
Control group
Placebo

Outcomes
Primary outcome [1] 302593 0
Heart rate at rest on ECG
Timepoint [1] 302593 0
30 minutes following administration of autonomic blockade + ivabradine or placebo
Primary outcome [2] 302594 0
Peak heart rate on ECG monitoring
Timepoint [2] 302594 0
During VO2 max test 30 minutes after administration of autonomic blockade + ivabradine or placebo (immediately after resting ECG)
Secondary outcome [1] 336463 0
Change in left ventricular end diastolic volume on echocardiography at rest
Timepoint [1] 336463 0
One hour following administration of autonomic blockade + ivabradine or placebo precrossover
Secondary outcome [2] 336464 0
Change in BNP on serum assay post exercise
Timepoint [2] 336464 0
Immediately following administration of autonomic blockade + ivabradine or placebo and VO2 max test
Secondary outcome [3] 336615 0
Change in right ventricular end diastolic volume on echocardiography at rest
Timepoint [3] 336615 0
One hour following administration of autonomic blockade + ivabradine or placebo pre crossover
Secondary outcome [4] 336616 0
Change in left ventricular end diastolic volume on MRI at rest
Timepoint [4] 336616 0
One hour following administration of autonomic blockade + ivabradine or placebo post cross over
Secondary outcome [5] 336617 0
Change in right ventricular end diastolic volume on MRI at rest
Timepoint [5] 336617 0
One hour following administration of autonomic blockade + ivabradine or placebo post cross over
Secondary outcome [6] 336618 0
Change in right ventricular end diastolic volume on exercise MRI at maximal exercise
Timepoint [6] 336618 0
One hour following administration of autonomic blockade + ivabradine or placebo post cross over (immediately post rest MRI)
Secondary outcome [7] 336619 0
Change in right ventricular end diastolic volume on exercise MRI at maximal exercise
Timepoint [7] 336619 0
One hour following administration of autonomic blockade + ivabradine or placebo post cross over (immediately post rest MRI)
Secondary outcome [8] 336620 0
Change in right ventricular end diastolic volume on exercise echocardiography at maximal exercise
Timepoint [8] 336620 0
One hour following administration of autonomic blockade + ivabradine or placebo pre crossover (immediately post rest echocardiogram)
Secondary outcome [9] 336622 0
Change in left ventricular end diastolic volume on exercise echocardiography at maximal exercise
Timepoint [9] 336622 0
One hour following administration of autonomic blockade + ivabradine or placebo pre crossover
(immediately post rest echocardiogram)
Secondary outcome [10] 336623 0
Change in maximal left atrial volume on exercise echocardiography at maximal exercise
Timepoint [10] 336623 0
One hour following administration of autonomic blockade + ivabradine or placebo pre crossover
(immediately post rest echocardiogram)
Secondary outcome [11] 336624 0
Change in maximal left atrial volume on exercise MRI at maximal exercise
Timepoint [11] 336624 0
One hour following administration of autonomic blockade + ivabradine or placebo post crossover
(immediately post rest MRI)
Secondary outcome [12] 336625 0
Change in PA pressure as measured by measuring tricupsid regurgitation velocity during maximal exercise on exercise echocardiography
Timepoint [12] 336625 0
One hour following administration of autonomic blockade + ivabradine or placebo pre crossover
(immediately post rest echocardiogram)

Eligibility
Key inclusion criteria
Group 1 (Endurance athletes): Competing in endurance sport
Group 2 (Healthy Volunteers): Less than three hours of exercise per week
Group 3 (Endurance athletes with bradycardia): Endurance athletes with a resting heart rate less than 40
Minimum age
18 Years
Maximum age
50 Years
Gender
Both males and females
Can healthy volunteers participate?
Yes
Key exclusion criteria
1. Allergy to one of the medications
2. Asthma
3. Glaucoma
4. Urinary Retention/Prostate enlargement
5. Past history of psychosis
6. Ulcerative Colitis
7. Gastrointestinal Obstruction
8. Myasthenia gravis
9. Hypotension(low blood pressure
10. Smoker
11. Preexisting cardiac or lung disease
12. Pregnant or breast feeding
13. Contraindication to MRI

Study design
Purpose of the study
Prevention
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Numbered containers
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?
The people receiving the treatment/s
The people administering the treatment/s
The people assessing the outcomes
Intervention assignment
Crossover
Other design features
Phase
Phase 4
Type of endpoint(s)
Efficacy
Statistical methods / analysis
The group sizes were calculated to be able to detect a change in heart rate of 10 beats per minute.
Baseline comparisons of continuous variables will be made between groups using independent samples t-tests. Categorical value comparisons will be made using chi square testing. Repeated measures will be analysed using repeated measures ANOVA.

Recruitment
Recruitment status
Recruiting
Date of first participant enrolment
Anticipated
Actual
Date of last participant enrolment
Anticipated
Actual
Date of last data collection
Anticipated
Actual
Sample size
Target
Accrual to date
Final
Recruitment in Australia
Recruitment state(s)
VIC
Recruitment hospital [1] 8459 0
Baker Heart and Diabetes Institute - Melbourne
Recruitment postcode(s) [1] 16541 0
3004 - Melbourne

Funding & Sponsors
Funding source category [1] 296858 0
Government body
Name [1] 296858 0
NHMRC
Address [1] 296858 0
GPO Box 1421
Canberra ACT 2601
Country [1] 296858 0
Australia
Primary sponsor type
Other
Name
Baker Heart and Diabetes Institute
Address
PO Box 6492, Melbourne Victoria 3004, Australia
Country
Australia
Secondary sponsor category [1] 295864 0
None
Name [1] 295864 0
Address [1] 295864 0
Country [1] 295864 0

Ethics approval
Ethics application status
Approved
Ethics committee name [1] 298085 0
Alfred Hospital Ethics Committee
Ethics committee address [1] 298085 0
Old Baker Building, Level 1,
55 Commercial Rd, Melbourne VIC 3004
Ethics committee country [1] 298085 0
Australia
Date submitted for ethics approval [1] 298085 0
29/03/2017
Approval date [1] 298085 0
10/05/2017
Ethics approval number [1] 298085 0
138/17

Summary
Brief summary
It is well known that athletes have lower heart rates (bradycardia) than non-athletes. This is generally considered a healthy adaptation. However, bradycardia has been associated with the subsequent development of atrial fibrillation (AF), an arrhythmia known to increase the risk of heart failure, stroke and even death. Consequently, bradycardia could conceivably be associated with significant problems later in life.

The reasons athletes have slow heart rates are not well understood. Traditionally changes in neural input (vagal tone) were thought to lead to bradycardia in athletes. However, several studies have demonstrated that even after blocking these inputs(autonomic blockade), athletes continue to have lower heart rates than non-athletes. The reasons for this are not known however recent research using athlete mice models suggests this is due to intrinsic changes within the heart by downregulation of the HCN4 gene. In the mouse model, the medication which blocks this gene, ivabradine, helped to equalize the heart rates in athlete and non-athlete mice.

Our aim in this study is to understand the reason for lower heart rates in endurance athletes. Participants will undergo repeat testing under experimental conditions to help determine the causes of low heart rates in athletes.

We hypothesize that ivabradine will be less effective in athletes, ie it will lower the heart rate of athletes less than nonathletes. This would suggest that bradycardia in athletes is associated with changes within the heart rather than reversible changes in neural inputs. This may provide some insights into the mechanism of atrial fibrillation in athletes.
Trial website
https://www.baker.edu.au/research/clinical-trials/endurance-athletes
Trial related presentations / publications
Public notes
Attachments [1] 3088 3088 0 0

Contacts
Principal investigator
Name 75946 0
A/Prof Andre La Gerche
Address 75946 0
Baker Heart and Diabetes Institute
Level 4, Alfred Centre
99 Commercial Road
Melbourne, VIC 3004
Country 75946 0
Australia
Phone 75946 0
+61 3 8532 1143
Fax 75946 0
Email 75946 0
andre.lagerche@baker.edu.au
Contact person for public queries
Name 75947 0
Dr Darragh Flannery
Address 75947 0
Baker Heart and Diabetes Institute
Level 4, Alfred Centre
99 Commercial Road
Melbourne, VIC 3004
Country 75947 0
Australia
Phone 75947 0
+61 3 8532 1214
Fax 75947 0
Email 75947 0
darragh.flannery@baker.edu.au
Contact person for scientific queries
Name 75948 0
A/Prof Andre La Gerche
Address 75948 0
Baker Heart and Diabetes Institute
Level 4, Alfred Centre
99 Commercial Road
Melbourne, VIC 3004
Country 75948 0
Australia
Phone 75948 0
+ 61 3 8532 1143
Fax 75948 0
Email 75948 0
andre.lagerche@baker.edu.au

No data has been provided for results reporting
Summary results
Not applicable