At a time when new evidence strongly suggests that roughly a fifth of patents with hypertension have primary aldosteronism as the cause, other recent findings suggest that many of these possibly tens of millions of patients with aldosterone-driven high blood pressure may as a consequence need an expensive and not-widely-available diagnostic test – adrenal vein sampling – to determine whether they are candidates for a definitive surgical cure to their aldosteronism.
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Some endocrinologists worry the worldwide infrastructure for running adrenal vein sampling (AVS) isn’t close to being in place to deliver on this looming need for patients with primary aldosteronism (PA), especially given the burgeoning numbers now being cited for PA prevalence.
“The system could be overwhelmed,” warned Robert M. Carey, MD, a cardiovascular endocrinologist and professor of medicine at the University of Virginia in Charlottesville. “Right now, adrenal vein sampling [AVS] is the gold standard,” for distinguishing unilateral and bilateral excess aldosterone secretion, “but not every radiologist can do AVS. Until we find a surrogate biomarker that can distinguish unilateral and bilateral PA” many patients will need AVS, Dr. Carey said in an interview.
“AVS is important for accurate lateralization of aldosterone excess in patients, but it may not be feasible for all patients with PA to undergo AVS. If the prevalence of PA truly is on the order of 15% [of all patients with hypertension] then health systems would be stretched to offer all of them AVS, which is technically challenging and requires dedicated training and is therefore limited to expert centers,” commented Jun Yang, MBBS, a cardiovascular endocrinologist at the Hudson Institute of Medical Research and a hypertension researcher at Monash University, both in Melbourne. “At Monash, our interventional radiologists have increased their [AVS] success rate from 40% to more than 90% during the past 10 years, and our waiting list for patients scheduled for AVS is now 3-4 months long,” Dr. Yang said in an interview.
Dr. Jun Yang
Finding a unilateral adrenal nodule as the cause of PA means that surgical removal is an option, a step that often fully resolves the PA and normalizes blood pressure. Patients with a bilateral source of the aldosterone are not candidates for surgical cure and must be managed with medical treatment, usually a mineralocorticoid receptor antagonist such as spironolactone that can neutralize or at least reduce the impact of hyperaldosteronism.
AVS finds unilateral adenomas when imaging can’t
The evidence that raised concerns about the reliability of imaging as an easier and noninvasive means to identify hypertensive patients with PA and a unilateral adrenal nodule that makes them candidates for surgical removal to resolve their PA and hypertension came out in May 2020 in a review of 174 PA patients who underwent AVS at a single center in Calgary, Alta., during 2006-2018.
The review included 366 patients with PA referred to the University of Calgary for assessment, of whom 179 had no adrenal nodule visible with either CT or MRI imaging, with 174 of these patients also undergoing successful AVS. The procedure revealed 70 patients (40%) had unilateral aldosterone secretion (Can J Cardiol. 2020 May 16. doi: 10.1016/j.cjca.2020.05.013).
In an editorial about this report that appeared a few weeks later, Ross D. Feldman, MD, a hypertension-management researcher and professor of medicine at the University of Manitoba in Winnipeg, Man., said the finding was “amazing,” and “confirms that lateralization of aldosterone secretion in a patient with PA but without an identifiable mass on that side is not a zebra,” but instead a presentation that “occurs in almost half of patients with PA and no discernible adenoma on the side that lateralizes.” (Can J. Cardiol. 2020 Jul 3. doi: 10.1016/j.cjca.2020.06.022).
Although this was just one center’s experience, the authors are not alone in making this finding, although prior reports seem to have been largely forgotten or ignored until now.
“The discordance between AVS and adrenal imaging has been documented by numerous groups, and in our own experience [in Melbourne] around 40% of patients with unilateral aldosterone excess do not have a distinct unilateral adenoma on CT,” said Dr. Yang.
“Here’s the problem,” summed up Dr. Feldman in an interview. “Nearly half of patients with hyperaldosteronism don’t localize based on a CT or MRI, so you have to do AVS, but AVS is not generally available; it’s only at tertiary centers; and you have to do a lot of them,” to do them well. “It’s a half-day procedure, and you have to hit the correct adrenal vein.”