Impact of diuretic treatment on cardiac rehabilitation outcomes - insights from the RECOVER-R registry

Background Diuretics are commonly used to reduce fluid overload. Despite their widespread use, there is no clear evidence that diuretics improve major clinical outcomes. Moreover, few studies have investigated their effects on quality of life and exercise capacity, and these have mainly focused on patients with heart failure. Purpose The aim of this analysis was to compare the effects of loop diuretics versus thiazide diuretics on functional capacity and health-related quality of life during exercise-based cardiac rehabilitation (EBCR), assessed by the 6-minute walk test (6-MWT) and the MacNew Heart questionnaire (MNH). Methods We retrospectively analysed patients who attended inpatient EBCR between 2022 and 2024 at a specialized rehabilitation centre in Switzerland for various cardiac conditions. Most patients (32%) had undergone coronary artery bypass grafting. The median EBCR stay was 20 days (IQR 20–27). Patients were categorised based on loop or thiazide diuretic use at admission, and therapy modifications were recorded as escalation or de-escalation (dose adjustment or addition/discontinuation of diuretics). Treatment outcomes were assessed using 6-MWT results and the MNH at admission and discharge. Results A total of 865 patients were included, of whom 22% were female, with a mean age of 64 years (SD ±11). At admission, 274 (32%) were treated with loop diuretics, 43 (5%) with thiazides, and 13 (2%) with both. During rehabilitation, therapy modification occurred in 81% of the patients receiving loop diuretics, 35% in the thiazide group, and 92% in the combination group with de-escalation being the most common change. Renal function at baseline was generally mildly reduced, but lowest in the combination therapy group (mean [SD] eGFR in ml/min: overall 74 [21], loop diuretics 67 [24], thiazide diuretics 72 [17], loop and thiazide diuretics 55 [23]). No significant differences were found between loop and thiazide diuretic therapies regarding changes in 6-MWT performance, MNH scores, or change in body weight during EBCR. However, when comparing patients with therapy de-escalation to those with unchanged or escalated therapy, the de-escalation group showed a significant improvement of 33 median metres in the 6-MWT (95% CI: −54 to −12; p < 0.01; figure 1). Weight changes remained non-significant (-0.25kg [95% CI: -0.93 to 0.43]; p = 0.27), as well as the global MNH score (-0.11 points [95% CI: -0.30 to 0.08]; p = 0.18). Among loop diuretic users only, therapy de-escalation was associated with a significant median improvement of 0.27 points (95% CI: −0.51 to −0.03; p = 0.05; figure 2) in the MNH emotional function domain. Conclusion In patients undergoing cardiac rehabilitation, de-escalation in diuretic therapy, particularly loop diuretics, was associated with an improvement in functional capacity and emotional well-being, while no significant changes were observed between different diuretic types.