The Use of Ambulatory Blood Pressure Monitors to Assess Angiotensin Converting Enzyme Inhibitors

Resistant hypertension is defined as blood pressure > 140/90 mm Hg while adherent to three
or more antihypertensive medications or < 140/90 mm Hg treated with four or more
antihypertensives. Patients with resistant hypertension may be at risk for elevated
nighttime blood pressure >120/70 mm Hg and "non-dipping" (night/day blood pressure > 0.9). A
higher rate of cardiovascular events occur during the "morning surge" partially attributed
elevated nighttime blood pressure due to increased renin angiotensin aldosterone system
(RAAS) activity. Angiotensin converting enzyme inhibitors (ACEIs) suppress RAAS activity

This prospective randomized parallel-group pilot study will occur at Memorial Family
Medicine. Eligible patients will undergo three study visits over a 5-8 week span. After
providing written informed consent, patients will complete an initial screening visit
assessing 25 hour blood pressure using ambulatory blood pressure monitors. Patients will
continue the study if they are found to have a nighttime blood pressure >120/70 mm Hg.
Patients continuing the study will be randomly assigned to equivalent dose lisinopril or
enalapril treatment arms and their administration time will be changed to "bedtime." At the
final visit, patients will complete a final ambulatory blood pressure analysis to reassess
nighttime blood pressure and dipping status.

It's expected that patients with enalapril treatment will have superior nighttime blood
pressure reduction compared to the lisinopril treatment group. If the expected outcome
occurs, more patients in the enalapril group will meet their nighttime blood pressure goal
(<120/70 mm Hg) and exhibit a "dipping pattern." Current evidence suggests that patients
with normal nighttime blood pressure and dipping pattern are at a lower risk for
cardiovascular morbidity and mortality.

Inclusion Criteria:

- Patients with clinic blood pressure > 140/90 mm Hg on 3 antihypertensives or clinic
blood pressure < 140/90 mm Hg on 4 antihypertensives

- Currently treated with an angiotensin converting enzyme inhibitor

Exclusion Criteria:

- Chronic kidney disease (CKD) stage 4 or worse

- Pheochromocytoma

- Unstable cardiovascular disease Stroke, Transient Ischemic Attack, Unstable Angina,
or Myocardial infarction in the last 30 days

- Hyperaldosteronism

- Current pregnancy

- Shift worker at night

- Presenting blood pressure > 180/110 mm Hg