Tuesday, November 13, 2007

Primary Aldosteronism Common in Patients With Type 2 DM and Resistant Htn

Primary Aldosteronism Common in Patients With Type 2 DM and Resistant Htn

Study Highlights:

Included were 100 consecutive patients aged 18 to 75 years with type 2 diabetes for more than 3 months and treated for hypertension with at least 3 antihypertensive medications.

Resistant hypertension was defined as blood pressure greater than 140/90 mm Hg despite the use of 3 or more antihypertensive agents.

Excluded were those treated with spironolactone or eplerenone; those with glycated hemoglobin value greater than 9%, severe uncontrolled hypertension (blood pressure > 180/110 mm Hg), a history of heart failure, angina, a serum creatinine level greater than 1.8 mg/dL, hepatic disease, Cushing's disease, hyperthyroidism, or pheochromocytoma; and those who were pregnant or lactating.

Patients were screened for primary aldosteronism while taking their usual medications, because stopping blood pressure medications was considered unethical.

Blood samples were drawn in the morning after 30 minutes of rest in the sitting position.

Patients with serum potassium levels of less than 3.5 mmol/L received KCl (40 mEq) daily for 1 week and were rescreened once the potassium level was at least 3.5 mmol/L.

Screening studies included measurement of PAC and PRA and the calculation of the PAC/PRA ratio.

Patients with hypertension and a PAC/PRA ratio greater than 30 ng/mL/hour underwent further studies to confirm a diagnosis of primary aldosteronism.

Salt loading was used to confirm the diagnosis.

Urinary aldosterone was measured 3 days after a salt load or PAC was measured after an intravenous salt load of 2 L of 0.9% saline infused for 4 hours at 500 mL/hour.

Primary aldosteronism was diagnosed if the 24-hour urinary aldosterone concentration was 12 µg or greater during the third day of salt load or if PAC was 5.0 ng/dL or greater after the intravenous load.
93 patients were black, 5 were white, 1 was Hispanic, and 1 was Native American.

Mean age was 59 years, mean duration of diabetes was 8.9 years, mean duration of hypertension was 16 years, and mean body mass index was 34.4 kg/m2 with 75% having a body mass index greater than 30 kg/m2.

The mean number of antihypertensive agents taken was 3.7.

98% were taking an angiotensin-converting enzyme inhibitor or angiotensin receptor blocker, 92% were taking a diuretic agent, 73% were taking a β-blocker, 62% were talking a calcium channel blocker, and 31% were taking an α-blocker.

Mean potassium level was 4.0 mmol/L with 15 subjects having levels below 3.5 mmol/L.

34% had an increased PAC/PRA ratio and received additional testing.

Primary aldosteronism was diagnosed in 14% of patients.

There were no differences in age, years of hypertension, years of diabetes, body mass index, blood pressure, glycated hemoglobin level, or numbers or types of antihypertensive agents used between those with and without primary aldosteronism.

Mean systolic and diastolic blood pressures were 157 and 93 mm Hg in those with primary aldosteronism and 158 and 89 mm Hg, respectively, in those without.

Those with primary aldosteronism had a lower potassium level (3.7 vs 4.0 mmol/L), lower serum creatinine level (0.9 vs 1.0 mg/dL), a higher PAC, a lower PRA, and higher PAC/PRA ratio vs those without primary aldosteronism.

Of those with resistant hypertension, 55% had suppressed PRA or salt-sensitive hypertension.

The authors concluded that patients with diabetes and poorly controlled hypertension should be screened for primary aldosteronism using the PAC/PRA ratio followed by salt-suppression testing in those with a positive ratio.

Pearls for Practice:

Resistant hypertension in patients with type 2 diabetes is defined as a persistent blood pressure of 140/90 mm Hg or higher despite treatment with at least 3 antihypertensive agents.

The prevalence of primary aldosteronism among patients with type 2 diabetes with resistant hypertension is 14%.

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