Condition category
Circulatory System
Date applied
Date assigned
Last edited
Retrospectively registered
Overall trial status
Recruitment status
No longer recruiting
Publication status

Plain English Summary

Background and study aims
Atrial fibrillation is a heart rhythm problem (arrhythmia) which causes the heart to beat irregularly and often at an abnormally fast pace. In these cases, the heart is often unable to supply enough blood to the body (a condition called ‘heart failure’). In about half of all heart failure patients the heart contracts reasonably well, but it does not relax properly because it is very stiff and so does not fill with sufficient blood between heart beats. These patients have a poor quality of life and a high risk of death, just as those heart failure patients who have hearts that contract poorly. There is a clear need to find beneficial therapies for such patients. The reason why patients with atrial fibrillation tend to have stiff hearts that fill poorly and develop heart failure is not known, but high levels of aldosterone have been suggested to play an important role. Aldosterone is normally produced by the kidney, travels in the blood, and has a wide range of affects throughout the body. We think that raised aldosterone levels may explain the stiffening of the heart and its poor filling in patients with atrial fibrillation and heart failure. The effects of aldosterone can be blunted with the drug spironolactone, and with this clinical trial we want to find out if giving spironolactone to patients with atrial fibrillation improves the way their hearts relax and so increases their ability to perform exercise and improving their quality of life.

Who can participate?
Adults aged 50 or over, with permanent atrial fibrillation and normal levels of the hormone called brain natriuretic peptide.

What does the study involve?
Participants are randomly allocated to one of two groups. Those in group 1 are treated with spironolactone for two years. Those in group 2 are treated with a placebo for two years. We then measure each participants tolerance to exercise, assess their health-related quality of life, assess the ability of the heart to relax (diastolic function measured by echocardiography) and also look at rates of hospitalisations (regardless of cause) during the trial. Participants are blinded to their group allocation.

What are the possible benefits and risks of participating?
The study treatment aims to improve exercise performance of quality of life of the participants. The study drug benefits from a very well established safety profile with possible side effects (such as increase in blood potassium) being usually mild and disappearing on stopping the drug.

Where is the study run from?
University of Birmingham (UK)

When is the study starting and how long is it expected to run for?
January 2015 to October 2017

Who is funding the study?
National Institute for Health Research (UK)

Who is the main contact?
Dr Eduard Shantsila

Trial website

Contact information



Primary contact

Dr Eduard Shantsila


Contact details

University of Birmingham
Department of Cardiovascular Medicine
Medical School
B15 2TT
United Kingdom

Additional identifiers

EudraCT number

2014-003702-33 number


Protocol/serial number


Study information

Scientific title

IMPRESS-AF: IMproved exercise tolerance in heart failure with PReserved Ejection fraction by Spironolactone on myocardial fibrosiS in Atrial Fibrillation - an open randomised double-blind parallel-group trial



Study hypothesis

It is hypothesised that in symptomatic patients with permanent AF with normal BNP levels treatment with spironolactone will improve exercise tolerance as a surrogate for cardiovascular mortality/morbidity (primary outcome), and will improve quality of life and diastolic function, as well as reduce the rate of all-cause hospital admissions, and increase rate of spontaneous cardioversion to sinus rhythm (secondary outcomes).

Ethics approval

Coventry and Warwickshire Research Ethics Committee, 07/01/2015, ref: 14/WM/1211

Study design

Two-year open randomised double-blind parallel-group single-site

Primary study design


Secondary study design

Randomised controlled trial

Trial setting


Trial type


Patient information sheet

Not available in web format, please use contact details to request a patient information sheet


Treatment of symptomatic patients with atrial fibrillation with preserved ejection fraction


The study patients will be randomised to receive spironolactone or placebo (i.e., two-arm study). Study patients and researchers will be blinded to treatment allocation. Placebo and spironolactone will be identical in appearance and packaging and manufactured as 25-mg tablets in accordance with national and international standards. Patients will be instructed to take the study drug at one capsule once daily after randomisation. There is no up-titration planned.

In the case of an increase in potassium level to 5.1-5.5 mmol/L or in the presence of other non-life-threatening side effects (such as gynaecomastia) the trial drug will be down-titrated to 25 mg each second day. In such cases, the investigators are advised to re-up-titrate the trial medication if the reason for down-titration has resolved. Routine laboratory surveillance of serum potassium, sodium, full blood count with hematocrit, and renal function will be done by protocol at each visit and within 1 week of any dose adjustment.

Drug toxicity will be defined as an increase in potassium level to >5.5 mmol/L. In the case of toxicity or suspected toxicity, the trial medication will be stopped for the duration of the trial, but the patient will be requested to attend the remaining follow-up visits.

The trial treatment will be administered during 2 years with no further follow-up planned.

The protocol calls for current optimised management of AF and any background cardiac pathology as per current guidelines.

Intervention type



Drug names


Primary outcome measure

Exercise tolerance (peak VO2 on cardio-pulmonary exercise testing); Timepoint(s): 2 years of treatment

Secondary outcome measures

1. Diastolic function measured by echocardiography; Timepoint(s): After 2 years of treatment
2. Exercise tolerance measured by 6-minute walking test; Timepoint(s): 2 years of treatment
3. Health-related quality of life (assessed using the validated questionnaires); Timepoint(s): After 2 years of treatment
4. Rates of all-cause hospitalisations; Timepoint(s): After 2 years of treatment
5. Sinus rhythm; Timepoint(s): After 2 years of treatment

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

1. Age 50 years old or over
2. Permanent AF as defined by the European Society of Cardiology (ESC) criteria
3. Normal BNP levels (<100 pg/mL)
4. Ability to understand and complete questionnaires (with or without use of a
translator/translated materials)

Participant type


Age group




Target number of participants

Planned Sample Size: 250; UK Sample Size: 250

Total final enrolment


Participant exclusion criteria

1. Severe systemic illness with life expectancy of less than 2 years from screening
2. Left ventricular ejection fraction (LVEF) <50% (echocardiography)
3. Severe chronic obstructive pulmonary disease (COPD) (e.g., requiring home oxygen or chronic oral steroid therapy)
4. Severe mitral/aortal valve stenosis/regurgitation
5. Significant renal dysfunction (serum creatinine 220 µmol/L or above), anuria, active renal insufficiency, rapidly progressing or sever impairment of renal function, confirmed or suspected renal insufficiency in diabetic patients/ diabetic nephropathy
6. Increase in potassium level to > 5mmol/L)
7. Recent coronary artery bypass graft surgery (within 3 months)
8. Use of aldosterone antagonist within 14 days before randomisation
9. Use of or potassium sparing diuretic within 14 days before randomisation
10. Systolic blood pressure >160 mm Hg
11. Addison’s disease
12. Hypersensitivity to spironolactone or any of the ingredients in the product
13. Any participant characteristic that may interfere with adherence to the trial protocol

Recruitment start date


Recruitment end date



Countries of recruitment

United Kingdom

Trial participating centre

University of Birmingham
Department of Cardiovascular Medicine
B15 2TT
United Kingdom

Sponsor information


University of Birmingham

Sponsor details

Department of Cardiovascular Medicine
Medical School
B15 2TT
United Kingdom

Sponsor type

Hospital/treatment centre



Funder type


Funder name

National Institute for Health Research

Alternative name(s)


Funding Body Type

government organisation

Funding Body Subtype

National government


United Kingdom

Results and Publications

Publication and dissemination plan

Not provided at time of registration

Intention to publish date

Participant level data

Not provided at time of registration

Basic results (scientific)

Publication list

2020 results in (added 17/12/2020)

Publication citations

Additional files

Editorial Notes

17/12/2020: Publication reference, total final enrolment and number added.