What cardiac risks are associated with hyperbaric oxygen therapy (HBOT) and which cardiac conditions contraindicate its use?

Cardiac Risks Associated with Hyperbaric Oxygen Therapy

HBOT carries specific cardiac risks including acute heart failure exacerbation, increased afterload from vasoconstriction, and decreased cardiac output, but these complications are rare and most patients—including those with reduced ejection fraction—tolerate treatment well when properly optimized beforehand.

Hemodynamic Effects and Mechanisms

HBOT produces predictable cardiovascular changes that can stress compromised hearts:

• Increased afterload occurs due to systemic vasoconstriction during hyperbaric exposure 1
• Decreased cardiac output and bradycardia are typical physiologic responses to hyperoxia 1, 2
• These hemodynamic shifts are generally well-tolerated in patients without preexisting cardiac disease 2

Documented Cardiac Complications

Acute Heart Failure Exacerbation

The most clinically significant cardiac risk is pulmonary edema:

• In patients with reduced ejection fraction (HFrEF): A retrospective study of 23 heart failure patients undergoing elective HBOT found 2 cases (8.7%) of symptomatic pulmonary edema 1

  • One patient with LVEF 24% developed dyspnea after the 4th treatment, attributed to voluntarily holding diuretics; managed with increased oral diuretics and completed 33 sessions 1
  • Another study of patients with LVEF ≤40% reported 2 cases of acute decompensated heart failure possibly linked to HBOT among 23 patients 3

• In patients with preserved ejection fraction (HFpEF): One patient with LVEF 64% developed dyspnea and desaturation after 6 sessions, requiring hospitalization for pulmonary edema confirmed by elevated BNP 1

Rare Serious Events

• Pulmonary edema during emergency treatment has been reported in case series, though remains uncommon 1
• No reports of inappropriate ICD therapies, arrhythmias, or device dysfunction in ex vivo testing of 22 explanted ICDs exposed to hyperbaric conditions up to 4000 hPa 4

Cardiac Conditions Requiring Caution (Not Absolute Contraindications)

Heart Failure with Reduced Ejection Fraction

HBOT is NOT absolutely contraindicated in HFrEF, but requires optimization:

• Patients with LVEF as low as 24-35% have successfully completed HBOT courses (average 39 sessions) 1, 3
• Critical prerequisite: Optimization of heart failure therapy and strict fluid restriction before initiating HBOT 1
• Ongoing surveillance is mandatory during treatment to detect early decompensation 1
• Patients should be instructed to maintain their diuretic regimen and not hold medications 1

Heart Failure with Preserved Ejection Fraction

• Previously considered lower risk, but documented cases of pulmonary edema demonstrate HFpEF patients also warrant careful monitoring 1
• Same optimization principles apply: fluid management and diuretic therapy must be optimized 1

Severe Cardiac Comorbidities

Patients with marked frailty or severe comorbidities face higher risk:

• Uncontrolled diabetes combined with cardiovascular disease increases adverse event risk 5
• Severe right ventricular dysfunction, moderate-to-severe tricuspid regurgitation, or pulmonary hypertension were present in some patients who tolerated HBOT, but these conditions warrant heightened vigilance 1

Coronary Artery Disease Considerations

Patients with coronary disease represent a "vulnerable state" requiring tailored approach:

• The 2025 Polish Medical Society guidelines specifically identify coronary disease as requiring "tailored oxygen durations and a lower threshold for HBOT" in the context of carbon monoxide poisoning 6
• Physical activity restriction is mandated in conscious patients before HBOT to reduce cardiac demand 6
• Transport risks must be weighed against HBOT benefits, particularly in unstable coronary patients 6

Pre-HBOT Cardiac Screening Approach

A comprehensive history and physical examination tailored to identify high-risk features is more practical than routine cardiac testing:

• Routine ECG and echocardiography have limited ability to detect risk-modifying states relevant to HBOT and lack cost-effectiveness as universal screening tools 2
• Target screening to high-risk populations: dialysis patients, those with implanted cardiac devices, and patients with known severe cardiac dysfunction 2
• Clinical parameters should guide decisions about whether additional cardiac investigation is warranted 2

Key Clinical Features to Assess

• History of heart failure with documented ejection fraction 1, 3
• Current fluid balance status and adequacy of diuretic therapy 1
• Coronary artery disease with recent ischemic symptoms 6
• Severe comorbidities including uncontrolled diabetes, advanced kidney disease 5
• Functional capacity and frailty assessment 5

Absolute Contraindications

Untreated pneumothorax is the primary absolute contraindication to HBOT from a cardiopulmonary standpoint 7

Severe COPD with CO₂ retention represents a contraindication due to respiratory rather than purely cardiac concerns 7

Special Cardiac Populations

Implantable Cardioverter-Defibrillators (ICDs)

• Ex vivo testing of 22 ICDs showed no mechanical distortion, inappropriate therapies, or dysfunction after single or 30 iterative exposures at 4000 hPa 4
• This suggests the traditional absolute contraindication for ICD recipients may need reconsideration, particularly for emergency HBOT 4
• Real-life clinical studies are needed before changing practice 4

Pregnancy with Cardiac Disease

• Pregnancy is a vulnerable state requiring lower threshold for HBOT in carbon monoxide poisoning 6
• HBOT is always indicated in pregnant women with CO poisoning regardless of COHb level or symptoms 6

Clinical Decision Algorithm for Cardiac Risk Assessment

1. Identify known cardiac disease:

   • Document ejection fraction if heart failure history exists 1, 3
   • Assess coronary disease stability and recent ischemic symptoms 6

2. Optimize cardiac status BEFORE initiating HBOT:

   • Ensure adequate diuretic therapy and euvolemic state 1
   • Confirm patient understanding of medication adherence during treatment 1
   • Restrict physical activity in conscious patients 6

3. Assess treatment urgency and transport risk:

   • For time-critical indications (e.g., CO poisoning with cardiac symptoms), HBOT benefits likely outweigh cardiac risks even in vulnerable patients 6
   • Transport risks must be factored into decision-making 6

4. Implement enhanced monitoring for high-risk patients:

   • Ongoing surveillance during and within 24 hours after each HBOT session 1, 3
   • Lower threshold to interrupt or modify treatment if symptoms develop 1

5. Manage complications promptly:

   • Acute decompensated heart failure responds to standard diuretic therapy 1, 3
   • Most patients can resume HBOT after stabilization 1

Common Pitfalls to Avoid

• Assuming HFpEF is low-risk: Patients with preserved ejection fraction can develop pulmonary edema during HBOT 1
• Allowing patients to self-adjust medications: Explicitly instruct patients to maintain diuretic regimens 1
• Overlooking fluid status: Even optimized heart failure patients require ongoing fluid management during multi-session HBOT courses 1
• Treating ICD as absolute contraindication in emergencies: Emerging evidence suggests reconsideration may be warranted 4