Right Heart Catheterization - Pulmonary Artery Pressures and Calculations
PULMONARY VASCULAR RESISTANCE = (meanPAP-PCWP) / CO
 • PVR is the recommended parameter for differentiating subtypes of PH (preferred over Trans-Pulmonary Gradient, TPG, and Diastolic Pulmonary Gradient, DPG).
 • PH (mean PAP>20) subtypes are identified based on PVR & PCWP
PULMONARY ARTERY PULSATILITY INDEX (PAPI) = (SPAP - dPAP) / RAP
 • PAPi ≤ 0.9 predicts RV failure and in-hospital mortality in inferior MI
 • PAPi < 1.85 predicts RV failure in patients with LVADs.
RAP/PCWP RATIO
 • A ↑ RA/PCWP correlates with RV dysfunction. e.g., RA/PCWP > 0.8 indicates RV dysfunction in patients with cardiogenic shock.
 • RA/PCWP>0.54 (EUROMACS)/ >0.63 predicted RV dysfunction in patients with LVADs.
SYSTEMIC VASCULAR RESISTANCE = [(MAP - RAP) / CO] x 80
 • In cardiogenic or hypovolemic shock, SVR T as a compensatory response.
 • Advanced cardiogenic shock may have a low or normal SVR.
CARDIAC POWER OUTPUT (CPO) = (MAP x CO)/451
 • Reflects hydraulic energy delivered by the LV.
 • CPO of <0.6 was the strongest independent hemodynamic correlate in the SHOCK trial registry for in-hospital mortality in patients with cardiogenic shock.
LV TRANSMURAL FILLING PRESSURE = PCWP - RAP
 • Reflects the pressure difference between the LV and its external forces, and influences LV filling.
 • Increases in RAP or pericardial pressure can reduce LV filling, stroke volume, and forward flow. e.g., PE, right heart failure.
THERMODILUTION (TD)
 • TD is EASY to perform (compared to Direct Fick) but technique-dependent
 • Less accurate in patients with irregular rhythms.
 • Was previously thought to be less accurate in severe TR and extremes of CO. However, studies have shown good correlation between TD and Direct Fick in severe TR and extremes of CO.
FICK:
 • Direct Fick is the GOLD STANDARD for measuring CO.
 • Direct Fick requires specialized equipment to measure oxygen consumption, which is generally not available in most catheterization laboratories.
 • Indirect Fick (using nomogram-based estimates of oxygen consumption) can lead to large errors, as much as 40% in cardiac output estimates, compared with the Direct Fick.

Ahmed Ghoneem, MD MSc @a_h_ghoneem

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