What is exercise-induced pulmonary hypertension?

Definition of Exercise-Induced Pulmonary Hypertension

Exercise-induced pulmonary hypertension (EIPH) is no longer recognized as a formal clinical entity due to lack of reliable data defining which exercise-induced changes in mean pulmonary arterial pressure or pulmonary vascular resistance have prognostic implications. 1

Current Consensus on Pulmonary Hypertension Definitions

The 2015 ESC/ERS guidelines clearly state that pulmonary hypertension (PH) is defined as:

• An increase in mean pulmonary arterial pressure (mPAP) ≥25 mmHg at rest as assessed by right heart catheterization 1
• The normal mPAP at rest is 14 ± 3 mmHg with an upper limit of normal of approximately 20 mmHg 1

Historical Context

Previously, exercise-induced PH was defined as:

• A mean pulmonary artery pressure >30 mmHg during exercise in the absence of pulmonary venous hypertension 1
• This definition was included in earlier guidelines but has since been abandoned 1

Why EIPH Is No Longer a Recognized Clinical Entity

The 2015 ESC/ERS guidelines explicitly state that "due to the lack of reliable data that define which levels of exercise-induced changes in mPAP or PVR have prognostic implications, a disease entity 'PH on exercise' cannot be defined and should not be used." 1

Key reasons for abandoning this concept include:

• Lack of standardized exercise protocols
• Absence of validated normal reference values
• Insufficient evidence linking exercise-induced hemodynamic changes to clinical outcomes
• Difficulty distinguishing pathological from physiological responses

Recent Research Perspectives

Despite the official guidelines, research interest in EIPH continues:

• Some researchers propose defining EIPH using a combination of parameters:

  • Mean PAP >30 mmHg at a cardiac output <10 L/min
  • Total pulmonary vascular resistance >3 Wood units at maximum exercise 2

• Others suggest using the mPAP/cardiac output slope (>3 mmHg/L/min) as a more reliable indicator than absolute pressure measurements 3

• Studies have shown that EIPH may represent an early, mild phase of the PAH spectrum, physiologically intermediate between normal and resting PAH 4

Clinical Implications

For patients with suspected early pulmonary vascular disease:

• Careful follow-up is recommended for patients with mPAP between 21-24 mmHg at rest, especially those at risk for developing PAH 1
• This includes patients with connective tissue disease and family members of patients with heritable PAH

Diagnostic Approach

Current diagnostic algorithms focus on resting hemodynamics:

1. Right heart catheterization remains the gold standard for PH diagnosis
2. PH is classified based on hemodynamic criteria:
   • Pre-capillary PH: mPAP ≥25 mmHg, PAWP ≤15 mmHg, PVR >3 Wood units
   • Post-capillary PH: mPAP ≥25 mmHg, PAWP >15 mmHg 1, 5

Conclusion

While exercise testing may provide valuable physiological insights, the concept of exercise-induced pulmonary hypertension as a distinct clinical entity has been removed from current guidelines due to insufficient evidence supporting its diagnostic criteria and prognostic significance.