Background:
Primary hyperaldosteronism is the most common cause of secondary hypertension. However very few cases are diagnosed during pregnancy due to physiological changes in the renin–angiotensin–aldosterone axis, leading to false negative results on screening, resulting in delayed appropriate treatment and high foetal and maternal morbidity and mortality.
Case discussion:
38 year old female with normal previous pregnancy, was noted to be hypertensive since first trimester and started on methydopa. Her blood pressure gradually worsened from 21 weeks of gestation despite up titrating antihypertensives (methydopa,labetalol and nifedipine LA) requiring admission for closer monitoring. She had persistent hypokalaemia with hypomagnesaemia and developed Severe Preeclampsia with proteinuria (2.5gm/day)anemia, hemolysis, thrombocytopenia and intrauterine growth retardation resulting in urgent caesarean section at 24 weeks gestation(Birth Weight:730gm).
Investigations for Secondary Hypertension showed normal renal artery doppler, marginally raised urinary catecholamines due to methydopa use, high serum aldosterone:1466.9 pmol/L (97.3 - 834.0) (< 4 times upper limit of normal for pregnancy) and plasma renin activity: 0.75ng/ml/hr (0.66 - 3.08).
Postpartum she had persistent hypokalaemia and hypertension. Serum aldosterone was 874pmol/L with plasma renin activity <0.13ng/ml/hr with confirmatory saline suppression test. The CT Scan of Adrenals was normal and patient declined Adrenal vein sampling.She is on medical therapy with spironolactone and potassium replacement.
Discussion:
Secondary causes of hypertension are estimated to complicate approximately 0.24% of pregnancies. Screening for secondary causes of hypertension should be considered in patients with early new onset or resistant hypertension keeping in mind the physiological changes and effect of medications. Persistent hypokalaemia and a plasma renin level of <4ng/ml/hr is an important clue to the diagnosis of primary hyperaldosteronism in pregnancy. Case reports of treatment with amiloride or eplerenone in patients with resistant hypertension during the second and third trimesters followed by spironolactone postpartum is considered a safe approach in pregnancy.