The challenges posed by the treatment of cardiorenal syndrome are complex, and are examined and discussed in this article by Ikhwan Marion, Consultant Geriatrician and GIM, Beacon Hospital, Vladimir Stoyanov, Consultant Nephrologist and GIM, Beacon Hospital, and David Barton, Consultant Cardiologist, Beacon Hospital

Abstract
The coexistence of heart failure (HF) and chronic kidney disease (CKD) in older adults represents a complex and increasingly prevalent clinical challenge. This intersection, commonly conceptualised as the cardiorenal syndrome, is characterised by intertwined haemodynamic, neurohormonal, inflammatory, and metabolic mechanisms that are further shaped by ageing physiology, frailty, sarcopenia, and multimorbidity. Conventional guideline-directed therapy, largely derived from younger and less complex populations, often proves difficult to apply in geriatric practice.

Older adults experience a narrow therapeutic margin, heightened susceptibility to adverse drug reactions, recurrent hospitalisation, and progressive functional decline. This review examines the epidemiology and pathophysiological interplay between HF and CKD in older adults and proposes a pragmatic and clinically grounded approach to management. Particular emphasis is placed on congestion assessment, rational pharmacotherapy, deprescribing, and balancing prognostic benefit against treatment burden while prioritising patient-centred outcomes.

Introduction
Heart failure and chronic kidney disease are strongly age-associated conditions whose coexistence has become a defining feature of contemporary geriatric medicine. Rather than functioning as parallel disease processes, the heart and kidneys exist within a tightly integrated physiological axis in which dysfunction of one organ frequently precipitates deterioration in the other. The resulting cardiorenal syndrome produces a clinical phenotype distinct from either condition alone, characterised by recurrent decompensation, reduced physiological reserve, heightened vulnerability to stressors, and substantial therapeutic complexity.

Older adults experience a narrow therapeutic margin, heightened susceptibility to adverse drug reactions, recurrent hospitalisation, and progressive functional decline

The burden of combined HF and CKD rises sharply with advancing age due to the cumulative effects of hypertension, diabetes mellitus, atherosclerosis, and vascular ageing. In older adults, this overlap frequently coexists with frailty, cognitive impairment, sarcopenia, and polypharmacy, rendering management particularly challenging. Conventional disease-specific guidelines are often poorly suited to this population because frail older adults remain substantially underrepresented in major cardiovascular and nephrology trials. Consequently, clinicians are frequently required to balance evidence-based medicine with clinical pragmatism and individualised care.

Epidemiology and Clinical Burden
The epidemiological overlap between HF and CKD is considerable. Approximately one-third of adults over the age of 70 demonstrate evidence of CKD, while HF prevalence approaches 20 per cent in individuals older than 80 years. Among patients hospitalised with HF, moderate CKD is present in up to 50 per cent of cases and is associated with significantly increased mortality, hospital readmission, and healthcare utilisation.

Importantly, the burden of cardiorenal disease extends beyond conventional cardiovascular and renal outcomes. Older adults commonly experience progressive loss of mobility, recurrent falls, worsening frailty, and cognitive decline. Repeated hospitalisations often accelerate functional deterioration, with many patients failing to regain their pre-admission baseline. Quality of life may deteriorate substantially because of dyspnoea, fatigue, fluid restriction, dietary limitations, and treatment burden.

From a healthcare systems perspective, cardiorenal disease contributes disproportionately to emergency admissions and prolonged inpatient stays. However, the human cost at the individual level—manifested through dependency, social isolation, and caregiver burden—is often underestimated.

Pathophysiological Interdependence
The pathophysiology of cardiorenal interactions is multifactorial and incompletely understood. Historically, reduced cardiac output was considered the principal mechanism underlying renal dysfunction in HF. While impaired forward flow remains important in advanced systolic dysfunction, contemporary evidence suggests that venous congestion may represent the dominant mechanism in many older patients, particularly those with HF with preserved ejection fraction (HFpEF). Elevated central venous pressure is transmitted retrogradely to the renal veins, increasing renal interstitial pressure and impairing glomerular filtration despite relatively preserved arterial perfusion.

Superimposed upon these haemodynamic abnormalities is sustained activation of neurohormonal systems, particularly the renin–angiotensin–aldosterone system (RAAS) and sympathetic nervous system. Although initially compensatory, chronic activation becomes maladaptive, promoting sodium retention, vasoconstriction, oxidative stress, inflammation, myocardial fibrosis, and progressive nephron injury. Endothelial dysfunction and chronic low-grade inflammation further contribute to vascular stiffness and impaired organ perfusion.

Ageing significantly modifies these processes. Structural renal senescence reduces nephron number and renal reserve, increasing susceptibility to haemodynamic perturbation. Concurrently, arterial stiffening and left ventricular hypertrophy favour the development of HFpEF, now the predominant HF phenotype in older adults. Sarcopenia further complicates clinical assessment because reduced creatinine production may mask the severity of renal impairment. Consequently, traditional biochemical markers often underestimate disease burden in frail elderly patients.

Diagnostic Challenges and Polypharmacy
Accurate assessment of volume status and renal function remains central yet challenging in older adults. Serum creatinine and estimated glomerular filtration rate (eGFR) should be interpreted cautiously because age-related reductions in muscle mass limit their reliability. Greater emphasis should therefore be placed on longitudinal trends rather than isolated laboratory values.

Clinical assessment of congestion may also be difficult. Peripheral oedema is frequently absent despite substantial fluid overload, particularly in frail individuals with reduced mobility. Careful evaluation of jugular venous pressure, weight trajectories, orthopnoea, and functional decline remains essential. Point-of-care ultrasound may provide additional value through assessment of pulmonary B-lines and inferior vena cava dynamics.

Polypharmacy represents one of the most significant therapeutic challenges in cardiorenal medicine.

Older adults frequently receive multiple medications targeting HF, CKD, diabetes, hypertension, and associated comorbidities. Although many of these therapies improve survival, their combined use substantially increases the risk of hypotension, electrolyte imbalance, falls, acute kidney injury, and drug–drug interactions.

A common clinical error is the premature discontinuation of prognostically beneficial therapies because of modest creatinine rises or concerns regarding renal function. This “renal fear” may paradoxically worsen congestion and accelerate both cardiac and renal decline. Conversely, failure to deprescribe non-beneficial medications perpetuates unnecessary treatment burden. Medication review should therefore be dynamic and individualised, with careful consideration of frailty, renal clearance, and life expectancy.

A Pragmatic Approach to Management
Management begins with identification of the patient’s clinical phenotype, including HF subtype, CKD stage, frailty severity, and functional status. In practice, the immediate priority is often the management of congestion, which remains the principal driver of symptoms and hospitalisation.

Loop diuretics continue to represent the cornerstone of therapy. However, advanced CKD frequently necessitates higher doses because of impaired tubular drug delivery. In cases of diuretic resistance, sequential nephron blockade using thiazide-type diuretics may be required. Careful monitoring of electrolytes and renal function is essential, although modest rises in creatinine are often acceptable if accompanied by symptomatic improvement and successful decongestion.

Cardiorenal disease in older adults represents a complex clinical syndrome requiring integration of cardiovascular, renal, and geriatric principles

Once euvolaemia has been achieved, attention should shift toward disease-modifying therapies. RAAS inhibitors remain fundamental in patients with HF with reduced ejection fraction and should not be withheld solely because of moderate renal impairment. A creatinine increase of up to 30 per cent following initiation is generally considered acceptable and reflects altered intraglomerular haemodynamics rather than structural injury.

Sodium–glucose cotransporter-2 (SGLT2) inhibitors have transformed the management of both HF and CKD. These agents provide significant cardiovascular and renal protection independent of diabetic status and demonstrate favourable safety profiles even in older adults. Their mechanisms—including reduction of intraglomerular pressure, osmotic diuresis, and improved metabolic efficiency—align closely with the pathophysiology of cardiorenal disease. Increasingly, SGLT2 inhibitors are regarded as foundational therapy across the spectrum of HF and CKD.

Beta-blockers and mineralocorticoid receptor antagonists retain important prognostic roles but require cautious titration in frail patients because of risks of bradycardia, hypotension, and hyperkalaemia.

Treatment decisions should prioritise tolerability and preservation of functional status rather than aggressive target-dose escalation.

Deprescribing is equally important. Non-steroidal anti-inflammatory drugs should generally be avoided, while redundant antihypertensive agents and non-essential medications should be rationalised where possible. Simplification of medication regimens may substantially improve adherence, safety, and quality of life.

Special Considerations and Future Directions
Electrolyte disturbances are common in cardiorenal disease. Hyponatraemia frequently reflects maladaptive antidiuretic hormone activation and is associated with poorer prognosis. Hyperkalaemia similarly complicates RAAS inhibitor use and requires careful individualised management.

The role of renal replacement therapy in frail older adults requires nuanced discussion. Although acute dialysis may be lifesaving in refractory pulmonary oedema or severe hyperkalaemia, long-term dialysis may offer limited survival benefit in advanced frailty while significantly impairing quality of life. Shared decision-making and realistic goal setting are therefore essential.

Despite major therapeutic advances, evidence guiding management in frail older adults remains limited. Future research should prioritise inclusion of elderly patients with multimorbidity and frailty while exploring biomarker-guided therapy, remote monitoring, and personalised treatment strategies.

Conclusion
Cardiorenal disease in older adults represents a complex clinical syndrome requiring integration of cardiovascular, renal, and geriatric principles. Successful management demands a shift away from rigid protocol-driven care toward a flexible, patient-centred approach that balances prognostic benefit against treatment burden. Relief of congestion, judicious use of disease-modifying therapies, active management of polypharmacy, and preservation of functional independence remain the central therapeutic priorities. Ultimately, the goal is not merely optimisation of organ-specific parameters, but maintenance of quality of life, autonomy, and dignity in an increasingly vulnerable population.

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