Measured parameters
eSVi = LVOT VTI * LVOT area/BSA
eCO = LVOT VTI * LVOT area * heart rate
eCI = (LVOT VTI * LVOT area/BSA) * heart rate
eWP (Nagueh) = 1.24 [E/eā] + 1.9
eWP (TR derived) = 4 * Vel(TR)2/2
sPAP = 4*(peak systolic TRV)2 + eRAP
dPAP = 4*(end-diastolic PRV)2 + eRAP
mPAP =
- Method 1: 4*(proto diastolic PRV)2 + eRAP
- Method 2: mean TR gradient + eRAP peak
Abbas Index (PVR) = Peak TR-Velocity / RV outflow tract VTI
eRAP =
- IVC diameter and collapse
- Hepatic venous flow pattern
- Tricuspid E/eā ratio
Derived parameters
CPO - Calculated Power OutputeCPO = eCO x MAP/451
eCPI = eCPO/BSA
Simplified eCPO = LVOT VTI x heart rate x MAP
APIeAPI = (SBP ā DBP)/eWP(Nagueh)
PAPi - PA Pulse Pressure indexePAPi = sPAP ā dPAP/eRAP. (Threshold of 1.85)
Simplified ePAPi = TR gradient/eRAP (Describes relationship between PASP and CVP)
RVCPI = TAPSE * peak TR gradient
Load Adaptation Index = TR VTI * RV end-diastolic length/RV end-diastolic area
Echo Correlation with PAC values
Echo Value | Corresponding PAC Value | R (%) | Sensitivity | Specificity |
eCO | CO (thermodilution) | 0.88 | 0.97 (at 2.2l) | 0.73 (at 2.2l) |
sPAP | sPAP | 0.92 | 0.87 (>35mmHg) | 0.63 (>35mmHg) |
RAP | CVP | 0.86 | 0.9 (>10mmHg) | 0.83 (>10mmHg) |
eCPO | CPO | 0.82 | 0.76 (CPO <0.6) | 0.85 (CPO <0.6) |
eWP | PCWP | 0.84 | 0.55 | |
Risk of overestimation of PCWP using echo-derived values. This can then result in misclassification of RV-dominant shock as biventricular shock (This happened in 50% of cases in one study)
Using E/eā ratio as a surrogate for PCWP appears unreliable (Nagueh method)
ePAPi shows good correlation with echo vs PAC measurements, especially at the lower end (which are more clinically useful in cardiogenic shock)