Higher Mortality in Patients with Undiagnosed Hypertension: Is the Electronic Medical Record the Key to Their Identification?

Introduction: Patients with hypertension (HTN) may remain undiagnosed as the diagnosis requires systolic blood pressure (SBP) ≥ 140 mmHg or diastolic blood pressure (DBP) ≥ 90 mmHg on ≥ 2 different occasions. Hypothesis: We sought to evaluate outcomes of patients without diagnosed hypertension who have elevated BP meeting current thresholds for hypertension on 2 consecutive episodes. Methods: Together with retrospective billing and clinical data, electronic records of all outpatient visits in 2009 were used to identify 24,277 patients with 2 consecutive visits (2CHBP) with SBP ≥ 140mmHg or DBP ≥ 90 mmHg and were compared with a previously identified cohort of 53,998 known hypertension patients. Among the 2CHBP group, 6,071 (25%) were identified without a prior diagnosis of hypertension and were categorized as undiagnosed hypertension. They were compared with patients with known hypertension who had ≥ 1 visit in 2009. Cross-sectional analysis of cardiovascular comorbidities and proportional hazards for survival were done. Results: Of 5,978 undiagnosed HTN patients, 49% were female compared to 51% of 10,311 known HTN. In the undiagnosed HTN group, 19.5% were ≥ 80 years compared to 30.4% of known HTN patients. Cardiovascular comorbidities were generally lower in the undiagnosed HTN group compared to the known HTN group - heart failure (7% v 8%; OR 0.88, 95% CI: 0.77 - 0.99; p < 0.038), atrial fibrillation (11% v 12%, OR 0.88 95% CI 0.79 - 0.97) and coronary artery disease (17% v 26%, OR 0.57 95% CI 0.52 - 0.61). However after a four year followup, mortality was higher in the undiagnosed HTN group with unadjusted hazard ratio HR 1.4 (95% CI 1.29 - 1.60, p<0.0001) and HR 2.41 (2.16 -2.68, p<0.0001) when adjusted for age, sex, heart failure and diabetes. Conclusions: Over a quarter of patients meeting current thresholds on 2 consecutive visits did not carry a known diagnosis of hypertension. Although younger and with less cardiovascular comorbidities than those with diagnosed hypertension, mortality after 4 years was significantly higher in those with undiagnosed hypertension. Electronic records can be used to identify these high risk patients.