What is the recommended dosing of sildenafil (phosphodiesterase inhibitor) in patients with congestive heart failure (CHF)?

Sildenafil Should Not Be Routinely Used in Congestive Heart Failure

Sildenafil is not recommended for routine use in patients with heart failure, as major clinical trials have failed to demonstrate improvement in exercise capacity, quality of life, or clinical outcomes. 1

Guideline Recommendations

Heart Failure with Preserved Ejection Fraction (HFpEF)

• The 2017 ACC/AHA/HFSA guidelines explicitly state that routine use of phosphodiesterase-5 inhibitors to increase activity or quality of life in patients with HFpEF is ineffective (Class III: No Benefit, Level of Evidence B-R). 1
• This recommendation is based on the RELAX trial, which randomized 216 patients with EF ≥50% to sildenafil versus placebo and showed no improvement in oxygen consumption or exercise tolerance. 1

Heart Failure with Reduced Ejection Fraction (HFrEF)

• No major guidelines recommend sildenafil for treatment of HFrEF as a therapeutic intervention for heart failure itself. 1
• The 2008 ESC guidelines specifically state that PDE5 inhibitors are not currently recommended for patients with advanced heart failure. 1

Important Contraindications and Safety Concerns

Absolute Contraindication

• Sildenafil should never be used in combination with nitrate preparations due to risk of severe hypotension. 1
• This is particularly critical as many heart failure patients are on nitrate therapy for symptomatic relief or concomitant coronary artery disease. 1

Limited Acceptable Use: Erectile Dysfunction Management

When Sildenafil May Be Considered

Sildenafil may be used cautiously in stable heart failure patients (NYHA class II-III) specifically for treatment of erectile dysfunction, not for heart failure management itself. 2, 3

Dosing for Erectile Dysfunction in CHF Patients

• Start with 50 mg taken as needed for sexual activity (not the 20 mg TID dosing used for pulmonary arterial hypertension). 2, 3
• The FDA-approved dosing for pulmonary arterial hypertension is 20 mg three times daily, administered 4-6 hours apart. 4
• However, this PAH dosing has not been validated for heart failure treatment and should not be extrapolated. 1

Prerequisites Before Prescribing

Before considering sildenafil for erectile dysfunction in CHF patients, ensure: 2

• Patient is in NYHA class II or III (stable disease)
• No current nitrate use
• Absence of active ischemia (documented by negative stress test or nuclear perfusion scan)
• Tolerability established by monitoring blood pressure for 4 hours after initial 50 mg dose

Expected Effects in CHF Patients

Small studies showed sildenafil in CHF patients caused: 3, 5

• Modest asymptomatic blood pressure reduction (mean 6 mmHg systolic)
• Reduction in heart rate during exercise
• Improvement in erectile function scores
• Potential improvement in depression symptoms and quality of life related to ED treatment

Evidence Showing Lack of Benefit for Heart Failure Treatment

Most Recent High-Quality Evidence

The 2022 SilHF trial (the most recent randomized controlled trial) definitively showed that sildenafil up to 40 mg three times daily did not improve symptoms, quality of life, pulmonary artery systolic pressure, or 6-minute walk distance in HFrEF patients with pulmonary hypertension. 6

• This trial included 69 patients with HFrEF and PASP ≥40 mmHg
• Sildenafil was generally well tolerated but showed numerically more serious adverse events (33% vs 21%)
• This represents the most recent evidence and should guide current practice

Conflicting Older Evidence

While some older, smaller studies (2004-2007) suggested potential benefits in exercise capacity and endothelial function 3, 5, 7, these findings were not confirmed in larger, more rigorous trials. The RELAX trial and SilHF trial represent higher quality evidence that supersedes these earlier observations. 1, 6

Clinical Pitfalls to Avoid

• Do not prescribe sildenafil as heart failure therapy - it has no proven benefit for mortality, morbidity, or quality of life related to heart failure itself 1, 6
• Do not use sildenafil in patients on nitrates - absolute contraindication due to severe hypotension risk 1
• Do not use in NYHA class IV patients - safety not established in advanced heart failure 1
• Do not confuse pulmonary arterial hypertension dosing with heart failure management - the 20 mg TID dosing is FDA-approved only for PAH, not CHF 4

Summary Algorithm

For CHF patients asking about sildenafil:

1. If requesting for heart failure symptom management → Do not prescribe (no proven benefit) 1, 6
2. If requesting for erectile dysfunction AND patient meets criteria (NYHA II-III, no nitrates, no active ischemia) → May consider 50 mg as needed with careful monitoring 2, 3
3. If patient on nitrates → Absolute contraindication 1
4. If NYHA class IV → Refer to specialist, do not initiate 1