Treatment of Heart Failure with Preserved Ejection Fraction (HFpEF) in Dogs and Cats (Part 2)
01. Overview
HFpEF is often associated with the comorbidities summarized in the previous article. The core treatment principle is to maintain the affected pet’s heart in an appropriate volume state. Scientific use of diuretics prevents acute cardiac insufficiency, while controlling comorbidities is crucial for delaying HFpEF progression. Echocardiographic monitoring during treatment is recommended using PT60 or BPU100 ultrasound for real-time assessment of cardiac function.
02. General Treatment
1.Correction of Fluid Retention
Veterinarians must monitor renal function when using diuretics to control volume overload symptoms (e.g., pulmonary congestion, peripheral edema), as heart failure (HF) and renal failure often coexist or complicate each other.
- Diuretic selection: Thiazide diuretics for mild-to-moderate HF; loop diuretics for severe HF.
- Administration principle: Low doses with intermittent use to avoid hypotension. Unlike HFrEF, HFpEF is primarily caused by diastolic dysfunction—significant volume changes can drastically alter left ventricular stroke volume, requiring distinct diuretic strategies.
2.Improvement of Ventricular Diastolic Function
1.ACEIs (e.g., benazepril) & ARBs (e.g., losartan)
These are commonly used for heart failure with reduced ejection fraction (HFrEF), but have not been shown to significantly reduce the composite endpoint of cardiovascular events in HFpEF.
2.β-blockers
As negative inotropic agents, they prolong ventricular diastole and improve myocardial relaxation function in HFpEF. Notably, the administration strategy for HFpEF is opposite to that for HFrEF: for HFpEF, medium-to-high doses should be initiated promptly to control the pet’s heart rate within the normal range. Thus, β-blockers are suitable for pets with tachycardia.
3.Calcium channel blockers (CCBs)
These negative inotropic agents relax the myocardium, reduce heart rate, prolong diastole, improve ventricular compliance, relieve outflow tract obstruction, and enhance left ventricular filling.
4.Spironolactone
As an aldosterone receptor antagonist (aldosterone levels correlate with heart failure severity), it is effective for both HFrEF and HFpEF (aldosterone is a component of the RAAS system, which will be detailed in subsequent articles).
5.Digoxin
This positive inotropic agent is not recommended for HFpEF, but may be considered for rate control when atrial fibrillation is present.
6.Pimobendan
While this positive inotropic agent is highly effective for HFrEF, it does not improve oxygen consumption or exercise tolerance in HFpEF. However, it can be used flexibly based on clinical status when dogs/cats with HFpEF develop concurrent pulmonary congestion.
03. Treatment of Comorbidities
1.Hypertension and HFpEF
- Clinical features: Feline hypertensive heart disease is less common than canine; canine hypertensive heart disease often presents with diastolic dysfunction. Differentiate from dilated cardiomyopathy and hypertrophic cardiomyopathy (all cause myocardial hypertrophy and diastolic dysfunction).
- Treatment goals: Lower blood pressure, relieve symptoms, and reverse left ventricular hypertrophy.
- Recommended drugs: ACEIs, ARBs; β-blockers for tachycardia; CCBs. Combination therapy (e.g., ACEI + CCB) is advised for concurrent systolic and diastolic dysfunction.
- Target: Systolic blood pressure <150 mmHg to reduce mortality.
- Imaging monitoring: Use BPU60C ultrasound to assess left ventricular hypertrophy regression.
2.Diabetes Mellitus and HFpEF
- Association: Diabetes increases HF risk; impaired glucose tolerance and insulin resistance elevate risk even without overt diabetes. Each 1% increase in HbA1c raises HF risk by 8%; both hyperglycemia and hypoglycemia adversely affect HF.
- Diagnostic criteria: Canine fasting blood glucose ≥8.4 mmol/L or postprandial ≥11.2 mmol/L; feline blood glucose 4.11–8.84 mmol/L (normal range). 80% of cases are type 2 diabetes, which is more prone to diastolic dysfunction.
- Treatment principles: Control blood glucose (insulin therapy), lifestyle intervention (low-carb diet, muscle mass enhancement for obese/underweight pets).
3. Atrial Fibrillation and HFpEF
- Clinical impact: Atrial fibrillation (350–600 bpm atrial rate) impairs late ventricular diastolic filling, reduces stroke volume, and exacerbates HFpEF due to loss of atrial contractility, tachycardia, and irregular cardiac cycles. Feline incidence is higher (linked to hypertrophic cardiomyopathy and increased cat ownership).
- Treatment: β-blockers as first-line therapy for rate control; add diltiazem if ineffective. Digoxin may be considered in pets with normal renal function. Monitor for bradycardic atrial fibrillation during treatment.
- Echocardiographic assessment: Use [PT50] ultrasound to evaluate ventricular response to rate control.
4.Hypertrophic Cardiomyopathy and HFpEF
- Pathophysiology: Canine hypertrophic cardiomyopathy is often eccentric; feline is concentric. Both cause left ventricular hypertrophy, impaired filling, and reduced diastolic compliance.
- Treatment goals: Improve diastolic function, relieve outflow tract obstruction, alleviate symptoms, and prevent sudden death.
- Recommended drugs: β-blockers, non-dihydropyridine CCBs (use cautiously in severe outflow tract obstruction: mild = peak pressure gradient <50 mmHg; moderate = 50–75 mmHg; severe ≥75 mmHg)
5.Chronic Kidney Disease (CKD) and HFpEF
- Interaction: CKD may be independent or a HF complication. Diuretics (excreted via kidneys) can induce renal hypoperfusion if overused, leading to electrolyte/acid-base imbalances.
- CKD staging (based on serum creatinine):
- Compensatory stage: <140 μmol/L (asymptomatic, normal or slightly elevated renal function tests).
- Renal insufficiency stage: 141–220 μmol/L (glomerular damage, azotemia, anemia).
- Renal failure stage: 221–439 μmol/L (75%–90% renal impairment, overt anemia, polyuria, edema, acidosis).
- End-stage renal disease: 440–880 μmol/L (>95% glomerular damage, vomiting, oliguria, severe anemia, pruritus).
- Diuretic use: Tailor to CKD stage—diuretics are not contraindicated and may be therapeutic for CKD.
6.Anemia and HFpEF
- Clinical significance: Iron deficiency reduces exercise tolerance and quality of life; low hemoglobin is an independent predictor of chronic HF. ACEIs/ARBs may decrease erythropoietin (EPO) levels, contributing to anemia.
- Treatment: Blood transfusion for severe anemia (emergency only; monitor volume overload and diurese if needed). Canine recombinant EPO is not recommended for mild-to-moderate anemia with HF (elevates hypertension/thrombosis risk).