Clinical Briefs
March 15, 2015 3 minutes read
Ambulatory BP Monitoring
SOURCE: Turner JR, et al. Am J Medicine 2015; 128:14-20
The benefits of hypertension treatment (HTN), often cited as a 25% reduction in myocardial infarction, 40% reduction in stroke, and 50% reduction in heart failure, have generally been demonstrated in clinical trials based on an office blood pressure measurement. Since a substantial minority of patients enrolled in HTN trials — approximately one-third according to numerous estimates — ultimately turn out to have white coat HTN (wc-HTN), we may be underestimating the actual benefits of HTN treatment. Patients with wc-HTN do not suffer the same increased risk of cardiovascular events as HTN patients; hence, their inclusion in HTN trials “dilutes” treatment effects.
Since 2011, the United Kingdom regulatory agency NICE (National Institute for Health and Care Excellence) has asked that primary care clinicians obtain ambulatory BP monitoring (ABPM) on all patients suspected of HTN prior to initiation of treatment. Why? Because no treatment is indicated in the one-third of patients who typically turn out to have wc-HTN. United Kingdom calculations indicate that routine application of ABPM in primary care will save tens of millions of dollars.
ABPM is the most accurate tool for identifying wc-HTN. Additionally, it can help ascertain whether symptoms such as dizziness are potentially related to hypotensive episodes. It can also demonstrate whether treatment is truly providing 24-hour control of BP, which is usually not discernible in typical office practice where patients are evaluated during daytime hours.
ABPM is a much better predictor of cardiovascular risk than office blood pressure readings. At the current time in the United States Medicare only pays for ABPM when the diagnosis of wc-HTN is utilized. Private insurance coverage for ABPM varies. More routine inclusion of ABPM would likely help to clarify important HTN-related issues.
A New Oral Treatment for Hyperkalemia: Patiromer
SOURCE: Weir MR, et al. N Engl J Med 2015; 372:211-221.
Patiromer (PAT) is an oral non-absorbable polymer that works by binding potassium (K+) in exchange for calcium in the distal colon. Currently available oral treatments for hyperkalemia are burdened by GI adverse effects as well as limited efficacy. Hyperkalemia is particularly problematic in chronic kidney disease (CKD), which may be compounded by the need to administer ACE inhibitors or angiotensin II receptor blockers (ARB).
Weir et al performed a clinical trial of PAT in hyperkalemic patients with CKD stage 3 or 4 (eGFR = 15-59) who had been on a stable dose of ACE inhibitors or ARB for at least 4 weeks. Mild hyperkalemia (K+ = 5.1-5.4 mmol/L) was treated with PAT 4.2 g BID, and moderate-severe hyperkalemia (K+ = 5.5-6.4 mmol/L) with PAT 8.4 g BID.
At the end of 4 weeks, 76% of hyperkalemic patients treated with PAT had reached their target K+ of 3.8-5.0 mmol/L. Re-randomization to placebo or PAT for an additional 8 weeks showed that 85% of PAT-treated patients remained normokalemic, whereas 60% of placebo recipients drifted back into hyperkalemia. PAT was well tolerated: 11% of PAT patients experienced mild-moderate constipation.
PAT shows great promise as a new treatment for hyperkalemia.
Obesity Leads to Overdiagnosis of Airflow Obstruction
SOURCE: Collins BF, et al. Chest 2014;146: 1513-1520
Some commonplace disorders can readily misdirect clinicians about the presence of other important diagnoses. For instance, in patients with chronic obstructive pulmonary disease (COPD), deterioration of cardiac function, leading to congestive, can easily be misinterpreted as worsening COPD since fatigue, exercise, intolerance, and dyspnea are common to both. Could obesity misdirect clinicians in their diagnostic process for COPD? This report from the Veterans Administration system suggests that it can.
Collins et al reviewed data of obese veterans diagnosed with COPD who had undergone spirometry. Approximately half of COPD patients did not demonstrate airflow obstruction (necessary for the diagnosis of COPD) upon spirometry. After spirometry was performed, obese persons were less likely than normal weight individuals to have inhaler medications decreased or discontinued. The data found that as the degree of obesity increased in these COPD patients, the likelihood that airflow obstruction would be found on spirometry decreased.
Although clinicians may be tempted to diagnose COPD based simply on symptoms alone, these data indicate that obese patients are particularly likely to be misdiagnosed with COPD, incurring potentially inappropriate medications and distracting clinicians from attaining a correct diagnosis to explain patients’ symptoms. Clinicians would be wise to follow clinical guidelines that indicate spirometry as the gold standard for COPD diagnosis.
Ambulatory BP Monitoring, A New Oral Treatment for Hyperkalemia: Patiromer, Obesity Leads to Overdiagnosis of Airflow Obstruction
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