The SNAP-HT Trial: self-management of antihypertensive medication postpartum - can women do it better?

Conference: 
SAPC ASM 2017 - Warwick
Talk Code: 
4C.1
Presenter: 
Richard McManus
Co-authors: 
A.E. Cairns1, K.L. Tucker1, P. Leeson2, L. Mackillop3, C. Crawford1, N. Baker4, J. Tebbutt5, R.J. McManus1
Author institutions: 
1. Nuffield Department of Primary Care Health Sciences, University of Oxford; 2. Cardiovascular Clinical Research Facility, University of Oxford; 3. Nuffield Department of Obstetrics and Gynaecology, University of Oxford; 4. Royal Berkshire Hospital NHS Foundation Trust, Reading; 5. Buckinghamshire Healthcare NHS Trust, Aylesbury.

Problem

New onset hypertension affects one in ten women during pregnancy. Women may require large doses of antihypertensive medication postpartum, but the majority will be treatment-free by three to six months. Rapidly changing BP during this time poses a challenge in terms of appropriate antihypertensive dose adjustment postpartum and may be related to future cardiovascular risk. In essential hypertension, self-management significantly improved blood pressure (BP). We developed a novel postpartum self-management intervention, and performed an initial evaluation in a feasibility study.

Approach

Postnatal women, with gestational hypertension or pre-eclampsia requiring antihypertensive treatment, were randomised to self-management or usual care. Self-management involved daily home BP monitoring, using a validated device, and submission of readings via a mobile phone-based telemonitoring system, which provided automatic feedback and included an individualised medication reduction schedule. Women attended five follow-up visits over six months; at each visit BP was measured, using a validated, automated monitor. The primary outcome was feasibility. For analysis of differences in BP at follow-up, a repeated measures mixed-effects regression model was used.

Findings

91/188 (48%) women approached were randomised (45 intervention, 46 control). There were 9/91 (10%) withdrawals. Amongst the 82 complete cases, 403/410 (98%) follow-up visits were completed.

The groups had similar baseline characteristics. Their mean age was 32y (SD 5), mean body mass index 29kg/m2 (SD 8), and mean baseline BP (day 1-6 postpartum) 133/86mmHg (SD 14/10 respectively).

In the intervention group, 1075/1513 (71%) expected daily readings (on treatment) were submitted. BP measures at follow-up tended to be lower in the intervention group (table). This was most marked at 6 weeks [adjusted mean differences, self-management lower: systolic BP: -5.2 (-9.3 - -1.2); diastolic BP -5.8 mmHg (-9.1 - -2.5)] and the difference in diastolic readings persisted to six months [-4.5 mmHg (-8.1 - -0.8)].

Consequences

The SNAP-HT study provides the first randomised controlled evaluation of BP self-management postpartum. Recruitment and retention rates suggest expanding the study would be practicable.The secondary outcome measures indicate that self-management might result in better postnatal BP control, and support evaluation in a large-scale multi-centre randomised controlled trial.

Submitted by: 
Richard McManus
Funding acknowledgement: 
This research was funded by the National Institute for Health Research (NIHR) Collaboration for Leadership in Applied Health Research and Care Oxford at Oxford Health NHS Foundation Trust and via a Research Professorship awarded to RMcM (NIHR-RP-02-12-015). The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR or the Department of Health.