Almost one-third of hypertensive patients seen routinely by a cardiologist had suboptimal blood pressure (BP) control, and physician performance varied widely in a study published online May 1 in Circulation: Cardiovascular Quality and Outcomes.

As dismal as those results may seem, BP control by cardiologists in the study exceeded the threshold set in the Million Hearts initiative.

Several health campaigns have identified hypertension as a modifiable risk factor for cardiovascular disease, making improvements in the rate of BP control a challenging but achievable goal. Those efforts include performance measures for physicians of patients with coronary artery disease and hypertension to meet a target BP of less than 140/90 mm Hg, as advocated by the American College of Cardiology and the American Heart Association. BP control also is included among the clinical interventions in Million Hearts, a national program designed to prevent a million heart attacks and strokes by 2017.

Ann Marie Navar-Boggan, MD, of the Duke University Medical Center in Durham, N.C. and colleagues wrote that most studies evaluating BP control have focused on primary care settings and not cardiology clinics. “Although patients with cardiovascular disease are more likely to receive treatment for hypertension, there is only limited evidence to suggest that patients treated by cardiologists have improved overall BP control compared with patients not seen by a cardiologist,” they wrote.

To shed light on that issue, they designed a retrospective cohort study of patients with a history of hypertension who were routinely followed by a cardiologist at clinics at Duke University Medical Center in Durham, N.C., between June 1, 2009, and June 30, 2010. Patients who were diagnosed with hypertension before or within six months of the start of the study period were eligible. The physicians were not aware that patients’ BP readings were monitored for research or quality improvement purposes.

The study enrolled 5,979 patients and 47 physicians. Of those patients, 30.3 percent were found to have suboptimal BP control (greater than or equal to 140/90 mm Hg) and 7 percent had Stage II hypertension (systolic BP of greater than or equal to 160 or diastolic BP of greater than or equal to 100). The average patient age was 66 years old. In a multivariable analysis, increasing age, female sex and nonwhite ethnicity were associated with worse BP control. About half of the patients used a general cardiology clinic (51.6 percent) and about a quarter were followed in a heart failure or  transplant clinic (24.7 percent).

At the physician level, unadjusted rates for suboptimal BP control ranged from 16 to 44 percent, and patients’ odds of suboptimal BP control ranged from 0.53 among the highest performing physicians to 2.54 among the lowest. Adjusting for patient heterogeneity had little impact on the results. A review of charts showed that 35 percent of patients with elevated BP readings had a documented explanation, with 7 percent listed as noncompliant with medications. Cardiologists made changes in medications in less than half of the patient visits where BP was elevated.

“Given the important role of BP in modifying risk of cardiovascular disease, we believe that cardiologists should take on shared responsibility for BP management,” Navar-Boggan and colleagues wrote. “Although prior data have suggested that patients followed by cardiologists may have better BP control, our study is the first of this magnitude to assess the rate of hypertension control in a population of patients routinely followed by cardiologists in ambulatory care.”

They pointed out that an analysis of National Health and Nutrition Examination Survey (NHANES) data concluded that only 43 percent of hypertensive patients have controlled BP, making the cardiologists’ nearly 70 percent achievement better than the national average, as well as above the target BP control rate of 65 percent set in the Million Hearts initiative.

Nonetheless, the wide variability in performance across cardiologists suggests there is room for improvement, the authors argued. “Physician volume and subspecialist group were not associated with improved performance,” they noted. “In the future, practices of the highest- and lowest-performing physicians should be examined to identify what other variables may contribute to physician heterogeneity.” 

They pointed out that variables such as noncompliance may not be modifiable, and added among limitations the fact that the study relied on physician reporting of adherence, which may have led to an underestimation of nonadherence. Other limitations included the use of one academic medical center, which may not be generalizable to private practices or other settings. The use of a single center may also have led to underestimations in the rates of control and variability.

They concluded that their results show that BP control presents an opportunity to develop a quality improvement initiative.