Table 1

List of study aims and objectives with respective timepoint (s) for the measurement of each objective

	Objectives	Outcome measures	Timepoint(s)
Primary	To compare postpartum diastolic BP in the intervention arm vs the control arm.	24-hour average diastolic BP measured by SPACELAB 90217 24 hours ABPM	Visit 4 (6–9 months post partum)
Secondary	To compare the effect of the intervention on cardiovascular, cerebrovascular and vascular phenotypes	BP based 24-hour average systolic blood pressure assessed by SPACELAB 90217 24-hour ABPM Mean diurnal diastolic blood pressure assessed by SPACELAB 90217 ABPM Mean diurnal systolic blood pressure assessed by SPACELAB 90217 ABPM Mean nocturnal diastolic blood pressure assessed by SPACELAB 90217 24-hour ABPM Mean nocturnal systolic blood pressure assessed by SPACELAB 90217 24-hour ABPM Mean bedside diastolic blood pressure measured during study visit (mean of 2+3) Mean bedside systolic blood pressure measured during study visit (mean of 2+3)	6-9 months for the 24-hour ABPM measures
			Baseline, week 1, week 6 and 6–9 months for the bedside BP measures
		Cardiac MRI Left ventricular (LV) mass indexed to end-diastolic volume and body surface area (BSA) LV EDV indexed to BSA LV wall thickness LA volume indexed to BSA Right ventricular (RV) mass indexed to end-diastolic volume and body surface area RV EDV indexed to BSA RA volume indexed to BSA LV ejection fraction (EF) and RVEF LV and RV stroke volumes indexed to BSA Myocardial fibrosis ECV (extracellular volume)	For cardiac MRI at 6–12 months post partum
		Echo LV Diastolic function:E/E’ average, E/A ratio, E deceleration time Global longitudinal strain (GLS) LV systolic function (EF by Biplane Simpson’s) LA volume by Biplanar assessment	At baseline and at 6–12 months post partum for echo outcome measures
		Vascular Pulse wave velocity Augmentation index and Aortic BP Aortic distensibility (MRI)	PWV, Aortic BP and AI at baseline and at 6–12 months (aortic stiffness); aortic compliance (on MRI) at 6–12 months
		Cerebrovascular Total white matter hyperintensity volume Cerebral blood flow Mean vessel thickness of the middle and posterior cerebral arteries and internal carotid artery	6–12 months post partum for all Brain MRI measures.
		Retinal The corrected central retinal arteriolar equivalent The corrected central retinal venular equivalent Corrected central retinal arteriolar equivalent/corrected central retinal venular equivalent ratio.	6–12 months post partum for all retinal measures
Tertiary		Exercise echo Exercise ejection fraction (echo) and exercise LA volume at 50% of peak workload during a bicycle cardiopulmonary exercise test (CPET)	6–12 months post partum
		CPET VO2 at VT1	6–12 month post partum
	To explore in vitro vascular function in a substudy of 20 women	Assessment of endothelial cell function and circulating biomarker levels associated with vascular angiogenesis and inflammation in normotensive and hypertensive women to determine if BP improvement can affect vascular function	From baseline to 6–12 months post partum
		T1 mapping of the kidneys to look at cortico-medullary differentiation	6–12 months post partum
	To explore presence/absence of kidney injury and fibro-inflammatory status	EQ-5D-5L health questionnaire results	Baseline, week 1, week 6 and 6–12 months post partum
	Quality of life assessment	Qualitative semistructured interviews in a subset of individuals as well as assessment of acceptability and feasibility within the intervention arm	6–12 months post partum
	Participant experience: assessment of individual experience following intervention	Readmission number in each arm	0–12 months post partum
	No of readmissions in intervention versus control arm	Number and frequency of side effects reported (intervention via the app and control during follow up calls	0–12 months post partum
	Side effect impact
Intervention(s)	The intervention will consist of physician-optimised self-management of post-partum BP. Women will follow a ‘smartphone’ app-based algorithm for medication titration, which will provide individualised dose titration advice. This is overseen and any change is approved by physicians who review the uploaded readings and respond to telemonitored abnormal readings in a timely fashion.
Comparator	The control arm will be managed as per usual NHS-led care with assessment by their own healthcare professionals and adjustment of medications as required. The BP of this group will be monitored and recorded at the same time-points and in the same manner as the intervention arm as with all other secondary outcome measures.

ABPM, Ambulatory Blood Pressure Monitoring ; AI, Augmentation Index; BP, blood pressure; EDV, End Diastolic Volume; EQ-5D-5L, The descriptive system comprises five dimensions: mobility, self-care, usual activities, pain/discomfort and anxiety/depression to assess quality of life; NHS, National Health Service; RA, Right atrial; RWT, Relative Wall thickness.