Outcomes in patients treated with loop diuretics without a diagnosis of heart failure: a retrospective cohort study

Background Loop diuretics are commonly prescribed in the community, not always to patients with a recorded diagnosis of heart failure (HF). The rate of HF events in patients prescribed loop diuretics without a diagnosis of HF is unknown. Methods This was a propensity-matched cohort study using data from the Clinical Practice Research Datalink, Hospital Episode Statistics and Office of National Statistics in the UK. Patients prescribed a loop diuretic without a diagnosis of HF (loop diuretic group) between 1 January 2010 and 31 December 2015 were compared with patients with HF (HF group)-analysis A, and patients with risk factors for HF (either ischaemic heart disease, or diabetes and hypertension-at-risk group)-analysis B. The primary endpoint was an HF event (a composite of presentation with HF symptoms, HF hospitalisation, HF diagnosis (analysis B only) and all-cause mortality). Results From a total population of 180 384 patients (78 968 in the loop diuretic group, 28 177 in the HF group and 73 239 in the at-risk group), there were 59 694 patients, 22 352 patients and 57 219 patients in the loop diuretic, HF and at-risk groups, respectively, after exclusion criteria were applied. After propensity matching for age, sex and comorbidities, patients in the loop diuretic group had a similar rate of HF events as those in the HF group (71.9% vs 72.1%; HR=0.92 (95% CI 0.90 to 0.94); p<0.001), and twice as those in the at-risk group (59.2% vs 35.7%; HR=2.04 (95% CI 2.00 to 2.08); p<0.001). Conclusions Patients prescribed a loop diuretic without a recorded diagnosis of HF experience HF events at a rate comparable with that of patients with a recorded diagnosis of HF; many of these patients may have undiagnosed HF.