Heart rate (on ECG tracing)
60,000 / R-R distance in msec   (bpm)

Doppler equation
Blood flow velocity= (C x Doppler shift) / (2 x  transmission frequency x cos Q)

Statistics
Unpaired t-test
(Mean 1 - Mean 2) / V¯((((SD1² x (n1 - 1)) + (SD2² x (n2 - 1))) / (n1 + (n2 - 2)) x ((1 / n1) + (1 / n2)))

Hemodynamics
Systemic vascular resistance
SVR= 80 x [(MAP - RAP) / CO] dyne s cm^-5 
Normal value= 1170±180

Systemic vascular resistance index
90 x [(MAP - RAP) / cardiac index]

Pulmonary vascular resistance
PVR= 80 x (MPAP - LAP) / Q   dyne s cm^-5 
Normal value= 67±23

Pulmonary vascular resistance index
80 x (MPAP - PCWP) / cardiac index

Mean systolic ejection rate
MSER= Stroke index / LVET

Left ventricular transmural pressure
LV Diastolic pressure= transmural pressure + pericardial pressure,  mmHg

Left ventricular work index
Cardiac Index x 13.6 x (MAP - PCWP)

Left ventricular work index
0.0136 x (MAP - PCWP) x stroke volume index

Right ventricular work index
0.0136 x (MPAP - RAP) x stroke volume index

Coronary perfusion pressure
DAP - PCWP, mmHg

Double product
SAP x heart rate

C: constant, the velocity of sound in tissue (1.54 x 10⁵ cm/s)
Doppler shift: transmission frequency - return frequency
cos Q : cosine of incident angle
Mean 1: mean of variable 1
Mean 2: mean of variable 2
n1: number of cases of variable 1
n2: number of cases of variable 2
SD1: standard deviation of variable 1
SD2: standard deviation of variable 2

CO: cardiac output
DAP: diastolic arterial pressure
LAP: mean left atrial pressure
LVET: left ventricular ejection time. 
MAP: mean aortic pressure
MPAP: mean pulmonary artery pressure
PCWP: pulmonary capillary wedge pressure. 
Q: Pulmonary blood flow
RAP: mean right atrial pressure
SAP: systolic arterial pressure