Loop diuretic therapy with or without heart failure: impact on prognosis

Many patients are prescribed loop diuretics without a diagnostic record of heart failure. Little is known about their characteristics and prognosis.

Glasgow regional health records (2009-16) were obtained for adults with cardiovascular disease or taking loop diuretics. Outcomes were investigated using Cox models with hazard ratios adjusted for age, sex, socioeconomic deprivation, and comorbid disease (adjHR).

Of 198 898 patients (median age 65 years; 55% women), 161 935 (81%) neither took loop diuretics nor had a diagnostic record of heart failure (reference group), 23 963 (12%) were taking loop diuretics but had no heart failure recorded, 7844 (4%) had heart failure recorded and took loop diuretics, and 5156 (3%) had heart failure recorded but were not receiving loop diuretics. Compared to the reference group, five-year mortality was only slightly higher for heart failure in the absence of loop diuretics [22%; adjHR 1.2 (95% CI 1.1-1.3)], substantially higher for those taking loop diuretics with no record of heart failure [40%; adjHR 1.8 (95% CI 1.7-1.8)], and highest for heart failure treated with loop diuretics [52%; adjHR 2.2 (95% CI 2.0-2.2)].

For patients with cardiovascular disease, many are prescribed loop diuretics without a recorded diagnosis of heart failure. Mortality is more strongly associated with loop diuretic use than with a record of heart failure. The diagnosis of heart failure may be often missed, or loop diuretic use is associated with other conditions with a prognosis similar to heart failure, or inappropriate loop diuretic use increases mortality; all might be true.