Types 1-2: Cardiac Primary

[!sidenote] Type 1 occurs in 25-33% of acute decompensated heart failure admissions.

Type 1 (Acute Cardiorenal): Acute worsening of cardiac function leads to AKI. Examples include cardiogenic shock, acute decompensated heart failure, and post-cardiac surgery.

Type 2 (Chronic Cardiorenal): Chronic cardiac dysfunction causes progressive CKD. The classic HFrEF patient with gradually declining eGFR.

Types 3-4: Renal Primary

[!cornell-cue] Renal causing cardiac?

Type 3 (Acute Renocardiac): AKI precipitates acute cardiac dysfunction—hyperkalemia causing arrhythmias, volume overload causing pulmonary edema, uremic pericarditis.

[!marginnote] CKD patients have 10-20x higher CV mortality than age-matched controls.

Type 4 (Chronic Renocardiac): CKD contributes to chronic cardiac disease through LVH, accelerated atherosclerosis, vascular calcification, and chronic volume/pressure overload.

Type 5: Secondary

[!cornell-cue] Systemic causes?

Type 5 (Secondary): Systemic conditions affecting both organs simultaneously—sepsis, diabetes, amyloidosis, sarcoidosis, lupus.

Congestion, perfusion pressure, and forward flow

Cardiorenal kidney dysfunction cannot be reduced to “low blood pressure” or “too much diuretic.” Three hemodynamic domains must be distinguished:

• Venous back-pressure: RAP/CVP approximates the pressure opposing renal venous drainage and helps define the congestion burden.
• Arterial/perfusion pressure: MAP is the upstream pressure; a useful teaching approximation for the renal perfusion gradient is MAP − RAP/CVP.
• Forward flow: cardiac index describes flow normalized to body surface area and may be low despite a normal ejection fraction.

In a nationwide invasive-hemodynamic cohort of advanced HF, higher RAP had the strongest relationship with impaired measured GFR, followed by lower MAP and lower CI; high RAP plus low MAP was particularly unfavorable, and MAP−RAP related more closely to GFR than CI alone (PMID 35611889). This supports the teaching line: venous pressure guides decongestion; perfusion determines tolerance. It does not establish a universal safe BP threshold.

Decongestive versus maintenance phase

The inpatient plan should explicitly name the current phase:

1. Decongestive: residual congestion remains; treatment is judged by symptoms, examination, weight, urine output/natriuresis, perfusion, and kidney trajectory.
2. Transitional: the target state is near or reached; convert route/dose and prove stability.
3. Maintenance: preserve the target weight and avoid both recurrent congestion and continued inpatient-intensity diuresis.

A small-to-moderate filtration decline during aggressive decongestion is not automatically structural tubular injury (PMID 29352071), and its prognostic meaning depends on whether decongestion is actually occurring (PMID 32535124). Persistent congestion with worsening kidney function, however, is not reassurance; reassess dose/route, perfusion, venous pressure, alternative AKI causes, and the diagnosis.

Selected escalation to right-heart catheterization

When the patient remains dyspneic, kidney function worsens, and successful decongestion is uncertain, selected RHC can distinguish residual congestion, low output, and mixed physiology. RHC is especially useful when restrictive/infiltrative, constrictive, pulmonary vascular, or other occult hemodynamic disease is suspected. EF is a ratio; a small stiff ventricle can preserve EF while stroke volume and CI are critically low. RHC defines physiology, not the etiology of amyloidosis.

Inpatient–outpatient continuity packet

At discharge, carry forward the phase, target weight, loop agent/route/dose, potassium and kidney-function plan, GDMT intent, sick-day/restart plan, and the named clinician responsible for reviewing labs and adjusting therapy. This is the proposed mechanism behind the readmission project; it has not yet been measured as a mediator in the cohort.

SGLT2 Inhibitors

[!sidenote] DAPA-CKD: 39% reduction in kidney disease progression. EMPA-KIDNEY confirmed benefits across eGFR spectrum.

First-line for cardiorenal protection. Benefits independent of diabetes status. Mechanism includes natriuresis, reduced glomerular hyperfiltration, and metabolic effects.Initial eGFR dip of 3-5 mL/min is expected and not a reason to discontinue.

RAAS Inhibition

[!cornell-cue] ACEi/ARB tolerance?

ACEi, ARB, or ARNI should generally be preserved when possible because long-term cardiorenal benefit often outweighs a modest early eGFR decline. Do not use a single creatinine or potassium threshold without context; assess the magnitude and trajectory of change, perfusion/volume state, indication, interacting drugs, and the product/guideline monitoring plan.

MRAs

Spironolactone or eplerenone. Mortality benefit in HFrEF. Monitor potassium closely, especially with eGFR <45. Finerenone (non-steroidal MRA) shows kidney-specific benefits in DKD.

2025–2026 update: Finerenone’s role now spans the cardio-kidney-metabolic spectrum. It is FDA-approved for heart failure with LVEF ≥40% (FINEARTS-HF: primary composite RR 0.84, 95% CI 0.74–0.95; Solomon et al., N Engl J Med 2024;391:1475-1485, PMID 39225278); the FINE-HEART pooled analysis (18,991 patients) showed a 19% reduction in sudden death (HR 0.81, 0.67–0.98; Foà et al., J Am Coll Cardiol 2026, PMID 42233928); and CONFIDENCE prospectively supports combining finerenone with an SGLT2 inhibitor (Agarwal et al., N Engl J Med 2025;393:533-543). Steroidal MRAs, by contrast, remain unproven in HFpEF/HFmrEF — both TOPCAT and the 2026 SPIRIT-HF RCT (NCT04727073) were neutral.

Beta-Blockers

[!marginnote] Carvedilol may have slight renal advantage over metoprolol due to alpha-blockade.

Generally renal-neutral. Titrate slowly. Evidence strongest for carvedilol, metoprolol succinate, and bisoprolol.