January 25, 2023
3 min read
A novel CT scan helped physicians identify hormone-producing nodules that cause hypertension, curing some patients of the condition with their removal, according to the results of a prospective, within-patient trial.
Morris J. Brown, MD, FRCP, FMedSci, a professor of endocrine hypertension at the Queen Mary University of London, and colleagues wrote that primary aldosteronism (PA) as a result of a unilateral aldosterone-producing adenoma is a common cause of hypertension. In their study, Brown and colleagues found that a benign nodule in one of the adrenal glands caused two-thirds of cases among patients with elevated aldosterone secretion.
The researchers compared the accuracy of a non-invasive test — [C]metomidate positron emission tomography computed tomography scanning — with adrenal vein sampling (AVS) — a catheter study — in predicting PA biochemical remission and the possibility of surgically curing hypertension.
The traditional method of using a catheter study has previously been able to determine whether production is unilateral or bilateral, but unable to tell which patients could be cured of their high BP with surgery, according to a press release about the study.
The new scan, which uses a very short-acting dose of a radioactive dye that sticks to the aldosterone-producing nodule only — metomidate — was as accurate as AVS, but was much easier and less painful, according to the release.
Brown spoke with Healio about the CT scan, how it differs from traditional detection methods, the clinical implications of the study findings and more.
Healio: The new type of CT scan lights up nodules in a hormone gland. Can you describe why detecting these nodules is important?
Brown: Ten percent of hypertension is due to excess aldosterone production (primary aldosteronism, or PA), and at least half of these patients are potentially curable because only one of the two adrenal glands is responsible. The traditional method for differentiating unilateral from bilateral types of PA is a difficult, invasive technique called AVS. This is not widely available and often fails. Consequently, few patients come forward for diagnosis.
Healio: What are the challenges with catheter studies, and how will the CT scan address those challenges?
Brown: The adrenal veins are only 1 mm in diameter, and very difficult to cannulate, especially on the right-hand side. The PET CT is noninvasive. While there can be technical issues with the manufacture of the isotope, or with the scanner, once the patient has their injection, there is always a result. Many of the nodules are smaller than was appreciated from routine CT. This means that in many patients with apparently normal CT scans (as reported by radiologists unfamiliar with the PET CT pictures), a curable cause of the hypertension is missed.
Healio: What are the clinical and public health implications of your findings?
Brown: We need to work on scaling up the production, but potentially large. Currently less than 1% of patients with PA are diagnosed, and this is partly because of the lack of incentive to make the diagnosis, if it’s not then possible to find the approximately 50% who can be cured. Once the PET CT is available in every specialist center, the simple blood tests for diagnosing PA itself (measurement of the hormones renin and aldosterone in a blood sample) can be recommended as a routine test in all patients with uncontrolled hypertension.
Healio: How long do you think it would be before this CT scan is implemented into clinical practice?
Brown: We have now validated an analogue with a 2-hour instead of 20-minute half-life. The findings need to be peer-reviewed and then we can work out how to make the test generally available. The impact should be quick — maybe a five-fold increase in diagnoses in 2 years, and a 10-20-fold increase in 5 or more years.
Healio: Is there anything else you’d like to add?
Brown: Alongside evaluating the much simpler diagnostic procedure, we have been evaluating a simpler alternative to surgical removal of the whole adrenal gland as the cure. The alternative is to “ablate,” by radiofrequency waves, just the nodule, leaving the rest of the adrenal gland behind. We will be submitting our results, from the first 30 patients, for peer review in the next few months. They are sufficiently promising that we have funding from the British Heart Foundation for a trial, ‘WAVE’ in which 110 patients are randomized to either surgery or radiofrequency ablation (RFA). The trial started last month and is greatly helped by the scan. Not only does it help us to detect suitable patients, but it helps the person doing the ablation to target the right nodule, and to estimate the completeness of ablation with a follow-up scan after 6 months.