Cardiac Effects of Mineralocorticoid Receptor Antagonism After Preeclampsia

The goal of this clinical trial is to determine if the medication eplerenone yields greater improvements in coronary microvascular function than chlorthalidone in women who experienced preeclampsia during pregnancy and subsequently developed chronic hypertension. The main Aims are: * To test the hypothesis that, in women with prior preeclampsia, current chronic hypertension, and concentric LV remodeling, eplerenone improves coronary microvascular function vs. chlorthalidone. * To test the hypothesis that, in women with prior preeclampsia, current chronic hypertension, and concentric LV remodeling, eplerenone improves cardiac structure and function vs. chlorthalidone. Participants will: * First receive pre-treatment with Amlodipine for 12 weeks prior to beginning the study medication. * Start study treatment which involves daily self-administration of two oral capsules (eplerenone + potassium placebo or chlorthalidone + potassium), each taken once a day, for a total of 336 doses over 48 weeks. * Attend study visits at weeks 2, 12, 24, 36, and 48. These visits will involve collecting information, measuring blood pressure, and gathering blood and urine samples. Echocardiography (cardiac ultrasound), eye exam, and cardiac PET/CT scan will be performed during the baseline and week 48 visits.

Inclusion Criteria: * Female with a history of preeclampsia (defined by ACOG criteria) in a singleton pregnancy without pre-gestational chronic hypertension. * Current chronic hypertension (stage 1 or greater). * Evidence of concentric left ventricular (LV) remodeling, defined as relative LV wall thickness \>0.42, with or without LV hypertrophy. * Age 18-65 years at time of randomization. Exclusion Criteria: * Use of a mineralocorticoid receptor antagonist (MRA) or amiloride within the past 3 months or more than 30 days within the previous 12 months. * Planned pregnancy, current pregnancy, or lactation. * Systolic BP \>150 mmHg and/or diastolic BP \>95 mmHg while on antihypertensives, or systolic BP \>160 mmHg and/or diastolic BP \>100 mmHg if untreated. * BMI \>45 kg/m². * Clinical atherosclerotic cardiovascular disease, including coronary, cerebrovascular, or peripheral artery disease. * Diabetes mellitus. * LV ejection fraction \