Cardiorenal Syndrome

Ronco's Five Subtypes

Type 1 — ACUTE CARDIORENAL: acute heart failure → acute kidney injury (e.g. cardiogenic shock causing AKI)

Type 2 — CHRONIC CARDIORENAL: chronic heart failure → chronic CKD (low cardiac output + venous congestion over years)

Type 3 — ACUTE RENOCARDIAC: AKI → acute cardiac dysfunction (volume overload, uraemic pericarditis, hyperkalaemia arrhythmia)

Type 4 — CHRONIC RENOCARDIAC: CKD → chronic heart disease (LVH, vascular calcification, accelerated atherosclerosis)

Type 5 — SECONDARY: systemic disease damaging both (sepsis, lupus, diabetes, amyloid, sarcoid)

Pathophysiology

• Forward failure → low renal perfusion → activation of RAAS and SNS → fluid retention
• Backward failure → renal venous congestion (often more important than low CO) → reduced GFR
• Inflammation, oxidative stress, anaemia, CKD-MBD
• Drug accumulation, hyperkalaemia
• Cardiorenal-anaemia-iron deficiency triad

Assess Volume Carefully

• Daily weights, fluid balance
• JVP, peripheral oedema, lung crackles
• BNP / NT-proBNP
• Bedside ultrasound (B-lines, IVC size)
• Renal venous Doppler — emerging tool

Diuretic Ladder

1. IV furosemide bolus or infusion (PO often poorly absorbed in decompensated HF)

• Start with home dose ×2 IV
• Aim 3-5 L net negative/day until euvolaemic

2. Add THIAZIDE (metolazone 2.5-5 mg or bendroflumethiazide 5 mg PO) for sequential nephron blockade 3. Add ACETAZOLAMIDE 500 mg IV daily (ADVOR trial — improves decongestion) 4. Consider SGLT2 inhibitor if not already on one (osmotic diuresis + cardiac benefit) 5. Spironolactone 25-50 mg if K <4.5 and eGFR ≥30 6. TOLVAPTAN (V2 antagonist) if hyponatraemic 7. Ultrafiltration / CRRT if diuretic-resistant and end-organ damage

Monitor

• U&E daily during active diuresis
• Replace K and Mg actively
• Tolerate creatinine rise up to 30% if weight is falling
• If creatinine rises AND weight not falling → true AKI, reduce diuretic, reassess

FOUR PILLARS OF HFrEF (with renal context):

1. ACEi or ARB or ARNI (sacubitril/valsartan):

• ARNI preferred if EF <40%
• Up-titrate to target dose; accept up-to-30% creatinine rise
• Stop if hyperkalaemia >6 or AKI

2. BETA-BLOCKER (bisoprolol, carvedilol, nebivolol):

• Renally safe, prognostic in HFrEF
• Start low, go slow

3. MRA (spironolactone, eplerenone, finerenone):

• Use if eGFR ≥30, K <5.0
• Finerenone preferred if diabetes + CKD

4. SGLT2 INHIBITOR (dapagliflozin or empagliflozin):

• Use down to eGFR 20
• Benefits in HFrEF, HFpEF, HFmrEF — diabetes status irrelevant
• Continue after dialysis if tolerated

Adjuncts

• IV iron (ferric carboxymaltose) if iron deficient (AFFIRM-AHF)
• Treat anaemia (erythropoietin if appropriate)
• Statin (most patients)
• Anticoagulate if AF
• ICD or CRT-D as per cardiology

LIFESTYLE: salt <5 g, fluid 1.5-2 L (individualised), daily weights, cardiac rehab, smoking cessation, immunisations.

Common Mistakes

• Stopping diuretic at first creatinine rise — usually wrong; this delays decongestion and worsens outcome
• Stopping ACE/ARB at first K rise — first try diet, stop NSAIDs, consider K-binder (patiromer/SZC)
• Reflex avoidance of SGLT2i because of CKD — wrong; SGLT2i is renoprotective
• Diagnosing 'pre-renal AKI' when actually congestion (the kidneys need decongestion, NOT more fluid)

Working Across Specialties

• Combined cardio-renal clinics (joint nephrology + cardiology) reduce admissions
• Pharmacist-led titration improves uptake
• Heart failure nurse specialists help with home monitoring

Advanced Options

• Diuretic-resistant despite optimised therapy → consider:
• Outpatient IV furosemide
• Ultrafiltration
• Tolvaptan trial
• Peritoneal dialysis (sometimes used purely for fluid management)
• Advanced HF therapies (LVAD, transplant)
• Conservative care if frail end-stage