It is estimated that over 25% of the world's population had hypertension in the year 2000 and that this proportion will reach 30% in the year 2025. With the introduction of the 2017 Guideline for High Blood Pressure in Adults from the American College of Cardiology and the American Heart Association Task Force on Clinical Practice Guidelines, the definition of hypertension became broader and as a result the prevalence is expected to further increase. On the other hand, it is estimated that around 10% of the world's population is affected by chronic kidney disease (CKD) with hypertension being both cause and complication of CKD.

It is obvious that hypertension and CKD are interconnected and are both major risk factors for cardiovascular disease (CVD). Hypertension results in increased CVD risk both directly, as an independent factor, and indirectly via its negative impact on renal function. In fact, the deterioration of the renal function is proportional to the degree of hypertension. On the other hand, the more advanced the CKD is, the more challenging the management of hypertension becomes, as patients with CKD present altered patterns of blood pressure (BP) during the day and, additionally, the prevalence of white coat and masked hypertension is significantly higher in this group of patients.

To date, hypertensive patients are treated according to the BP recordings that are obtained in the office (OBP) during routine patient visits, which leads to inaccurate estimates of the true burden of hypertension and also affects the efficacy of the therapeutic intervention. It has been suggested that self measured BP (HBP) is a more accurate estimate of the patients' daytime BP compared to the conventional office BP measurements. This has been already confirmed in studies regarding the general population and it has been suggested that the same applies to the patients with CKD. This study aims to check the validity of this hypothesis by comparing the effect of the HBP - guided management versus the conventional OBP - guided management on the 24 hour ambulatory BP monitoring of patients with uncontrolled hypertension and CKD stage 3 and 4.

Hypertension among people with chronic kidney disease (CKD) is very common, difficult to diagnose and often poorly controlled. The identification and management of hypertension among patients with CKD is challenging, owing to the markedly altered patterns and rhythms of blood pressure (BP) during the 24-hour period (i.e., non-dipping status and nocturnal hypertension) and the high prevalence of white coat and masked hypertension in these individuals. Conventional BP recordings obtained in the office are reported to provide inaccurate estimates of the true BP burden assessed using out-of-office BP monitoring techniques. Self-measured BP by the patients themselves at home provides a more accurate estimate of the patient's daytime BP. Similarly to the general hypertensive population, clinical studies support the notion that among people with CKD, home BP monitoring offers several advantages over the conventional office BP recordings in diagnosing hypertension and estimating the associated cardiovascular and renal risk. Compared with office BP, home BP recordings exhibit closer association with indices of target-organ damage, such as left ventricular mass index and aortic pulse wave velocity (PWV). Moreover, compared with office BP, home BP recordings are stronger predictors of the rate of renal function decline over time and incident end-stage-renal-disease (ESRD) requiring dialysis. Importantly, home BP recordings were shown to carry stronger value relative to office BP in predicting the risk of all-cause and cardiovascular mortality.

The feasibility of performing repeated home BP monitoring over several days, weeks or months offers the ability to accurately assess alterations in BP levels and responses to antihypertensive therapy in the long-term. Consequently, several randomized controlled studies conducted in the general hypertensive population have provided evidence that home BP monitoring is a simple approach to guide the management of hypertension on a monthly basis. In a meta-analysis of 37 randomized controlled trials (incorporating data from 9,446 hypertensive patients), it was shown that compared with clinic BP-based hypertension management, home BP monitoring was associated with a significantly higher reduction in systolic BP [weighted mean difference (WMD): -2.63 mmHg; 95% Confidence Interval (CI): -4.24, -1.02] and in diastolic BP (WMD: -1.68 mmHg; 95% CI: -2.58, -0.79). Implementation of home BP monitoring as a tool to guide the management of hypertension was associated with more frequent reductions in the number of prescribed antihypertensive medications [relative risk (RR): 2.02; 95% CI: 1.32-3.11] and reduced the risk of therapeutic inertia, defined as unchanged antihypertensive regimen despite the presence of uncontrolled hypertension (RR: 0.82; 95% CI: 0.68-0.99).

In contrast to the accumulated evidence supporting the use of home BP (HBP)-guided management of hypertension in non-CKD populations, the only study to investigate the role of home BP monitoring as a tool to achieve BP targets in patients with CKD was a previous, small, randomized study enrolling 65 ESRD patients on maintenance hemodialysis. In this study the use of home BP monitoring for 6 months produced a significantly higher reduction in interdialytic ambulatory BP compared to conventional managements of hypertension based on routine pre-dialysis BP recordings (mean 24-hour BP at study-end: 135/76 versus 147/79 mmHg, p<0.05). Despite the fact that the use of home BP monitoring among people with hypertension and CKD is anticipated to overcome the barriers of white coat and masked hypertension effects and improve therapeutic inertia, there is still no solid evidence on the value of using this technique as a simple approach to improve BP control and maximize the associated benefits on regression of target-organ damage.

Inclusion Criteria:

• Age 18 years old or higher
• Stable CKD stage 3-4 (CKD-EPI estimated GFR: 15-60 ml/min/1.73m2)
• Treated or untreated uncontrolled hypertension, defined as office BP >140/90 mmHg for patients with diabetic or non-diabetic CKD and protein excretion <0.3 gr/day or office BP >130/80 mmHg for patients with diabetic or non-diabetic CKD and protein excretion ≥0.3 gr/day.22-24
• Patients must provide informed written consent

Exclusion Criteria:

• End-stage renal disease under hemodialysis or peritoneal dialysis
• Known secondary cause of hypertension (i.e., pheochromocytoma, primary aldosteronism, renovascular hypertension)
• Chronic atrial fibrillation
• Hospitalization for acute myocardial infarction, unstable angina or acute ischemic stroke within the 3 previous months
• Severe congestive heart failure stage III-IV according to New York Heart Association (NYHA) classification
• Body mass index (BMI) of >40 kg/m2
• History of malignancy or any other clinical condition associated with very poor prognosis