Resistant Hypertension with a Positive Aldosterone-Renin Ratio - and Heart Failure

Interpretation

• The ratio is suggestive but not clean. Hydrochlorothiazide raises aldosterone and lowers potassium, producing false positives; lisinopril suppresses aldosterone and raises renin, producing false negatives. The two interferences push in opposite directions, so a still-positive ratio on this combination is more impressive than it looks - but it is not diagnostic.
• Hypokalemia itself suppresses aldosterone secretion, so potassium 3.1 mmol/L can mask the true degree of autonomous production. Correct it before retesting.
• Aldosterone is only 19 ng/dL - modest. That is consistent with early disease and does not argue against it.

Before confirmatory testing

1. Replete potassium to 4.0–4.5 mmol/L with generous oral supplementation and liberalize dietary salt (sodium loading improves specificity).
2. Replace interfering agents with ones that do not distort the axis: verapamil (with or without hydralazine) for blood pressure plus doxazosin. That is a real transition - expect several weeks of titration and monitoring.
3. Exclude other causes of hypokalemia and hypertension: licorice or herbal products, diuretic abuse, renovascular disease, Cushing syndrome, and thyroid disease.
4. Repeat aldosterone and renin after correction, ideally in the morning with the patient upright for two hours.

• Be honest with her that one screening ratio is a starting point, not a diagnosis.

Avoid saline loading

• The saline infusion test (2 L over 4 hours) and oral sodium loading both impose a substantial sodium and volume load. In a patient with ejection fraction 40% and existing ankle edema, that risks decompensated heart failure. This is the key individualizing decision, and it is easy to get wrong by reflex.

Preferred: captopril challenge

• Give 25–50 mg captopril orally after sitting upright, measure aldosterone and renin at baseline and at 60–120 minutes. In normal physiology, aldosterone falls by roughly 30% or more; failure to suppress supports primary aldosteronism.
• Advantages: safe in heart failure, no volume load, quick. Limitations: modest sensitivity, fewer validation data than saline infusion, and interpretation is poorer in renal impairment (check creatinine first).
• Fludrocortisone suppression is effective but poorly tolerated and essentially unavailable in the United States.

Exceptions to confirmation

• Guidelines allow skipping confirmation in unequivocal cases - spontaneous hypokalemia, undetectable renin, and aldosterone clearly elevated. She is close but not there: her aldosterone is only 19 ng/dL, she is on a thiazide, and her potassium is confounded. Confirm.
• If confirmatory testing is logistically impossible, document the reasoning and proceed to imaging only if the result would change management.

Do not operate on the CT alone

• A 1.5-cm macronodule in a 54-year-old is not proof of a unilateral source. CT misclassifies roughly a quarter of cases: bilateral hyperplasia with a dominant nodule, and non-functioning incidentalomas sitting alongside a hyperplastic contralateral gland, both look exactly like this.
• Adrenal vein sampling is the standard before surgery whenever a surgical cure is contemplated, and it is essentially mandatory after age 35 or whenever CT findings are ambiguous - which this is.
• Adrenal vein sampling is technically demanding, requires an experienced operator, and cosyntropin stimulation improves success rates; schedule it, and confirm cortisol gradients to prove selectivity, and the aldosterone-to-cortisol lateralization ratio to prove lateralization.
• If she is not a surgical candidate, or declines, adrenal vein sampling is unnecessary - the result would not change therapy.

If adrenal vein sampling is genuinely unavailable

• Do not proceed to surgery on the CT appearance alone in a patient who is not otherwise a compelling unilateral case.
• Start a mineralocorticoid receptor antagonist: spironolactone 25 mg daily, titrated to 50–100 mg with potassium and creatinine checks at 1–2 weeks. She has HFpEF, so an MRA is doubly attractive from a cardiac standpoint; gynecomastia is less of a concern but monitor. Eplerenone is an alternative with less endocrine side effects.
• She "wants to avoid pills" - but a single targeted MRA that also treats hypokalemia and heart failure may replace the potassium chloride and reduce her antihypertensive burden, which is a persuasive framing. Interpret her improvement carefully: a good response to MRA supports the diagnosis but does not prove laterality.
• Also treat her sleep apnea; untreated OSA is a major driver of resistant hypertension and confounds every measurement.