Right heart catheterization

For monitoring of pressuresina. pulmonalis we use a special floating balloon Swan-Ganz catheter. It is introduced through the right heart into the lungs and wedged in one of its branches by an inflated balloon. Modern catheters are able to measure more parameters and by gradual introduction it is possible to measure central venous pressure, pressure in right atrium, right ventricle and in the lungs. Indications have been limited recently due to the possibility of detecting many cardiovascular parameters, especially by ultrasonography. The main thing is to measure the wedge pressure, because it is not detectable in any other way. Right-sided cardiac catheterization can also be used for differential diagnosis and definitive confirmation of the diagnosis of pulmonary hypertension. Parameters directly measurable: 


 * pressure in the pulmonary artery, central venous pressure,
 * wedge pressure,
 * cardiac output,
 * saturation of mixed venous blood,
 * central body temperature.

Other circulation parameters can be calculated from the measured parameters:


 * systemic and pulmonary vascular resistance,
 * heart rate volume,
 * oxygen consumption and supply,
 * left and right ventricular labor index.

Pulmonary hypertension
Catheterization makes it possible to measure the level of pressure in the lungs and compare it with the pressure in the wedge, which will make it possible to distinguish between precapillary and postcapillary causes of pulmonary hypertension. By definition, pulmonary hypertension is considered to be a mean pulmonary artery pressure> 25 mm Hg.

Wedge pressure
Wedge Pressure (PCWP,  Pulmonary Capillary Wedge Pressure ) is the pressure in the final branch of the lung after sealing with a balloon. After stopping the inflow from the pulmonary artery, the pressures equalize and its pressure should be equal to the pressure in the left atrium, showing some of the functions of the left heart. The standard is 2-12 mmHg[1]. The pressure fluctuates depending on the heart cycle, similar to phlebogram. The pressure level is usually used to assess filling (preload) and hydrostatic pressure in the pulmonary capillaries.

Elevated PCWP is associated with conditions that increase left ventricular end-diastolic pressure - left-sided systolic and diastolic heart failure, mitral and aortic valve defects, hypertrophic, constrictive and restrictive cardiomyopathy, hypervolemia, right-to-left shunts or cardiac tamponade.

Decreased PCWP is present in hypovolemia, pulmonary veno-occlusive disease or massive pulmonary embolism.

Other measured parameters
Today, these measured parameters can usually be replaced by ultrasonography or other non-invasive methods.

Measurement of minute cardiac output (CO)

 * Volume of blood expelled by the heart in 1 minute,
 * norm:  4–8 l/min,
 * cardiac index: 2.5–4.5 l/min m2 of body surface area,
 * can be measured in several ways:

Thermodilution

 * With a floating Swan-Ganz catheter inserted, at the end of which is thermistor,
 * A 10 ml physiologist is injected through the proximal hole in the catheter. room temperature solution (approximately 18-22 °C),
 * the distal thermistor shows a curve that is the result of a change in the temperature of the surrounding blood over time,
 * smaller minute volume → applied solution flows more slowly around the thermistor → smaller temperature difference + larger area under the curve.

Dilution method with dye indicator

 * Determination of fluid volume according to the concentration of the "indicator" (usually in the peripheral artery), a known amount of which has been dissolved in the fluid.

Fick's principle

 * The volume of blood that flows lungs to me per minute =  'minute cardiac output' ,
 *  value given by: (patient's oxygen consumption/min) / (oxygen content in arterial blood - oxygen content in mixed venous blood)

Measurement of vascular resistance
Vascular resistance is based on  Ohm's law:  pressure gradient + flow ratio ($$R = \frac{P}{Q}$$).

Pulmonary vascular resistance (PVR)

 * Norm: 20–130 dyn/s/cm-5,
 * $$PVR = \frac{TPG}{MSV} = \frac{PAP - PLS}{MSV} $$,


 * (TPG: transpulmonary gradient; MSV: minute cardiac output; PAP: mean pulmonary pressure; PLS: mean pressure in the left atrium, resp. wedge pressure) ,


 * determined mainly before cardiac surgery ( short circuit defects, heart transplants).

Peripheral (systemic) vascular resistance (SVR)

 * Norm: 700–1600 dyn/s/cm-5,
 * $$SVR = \frac{PAO - PPS}{MSV} $$,


 * (PAO: aortic pressure; PPS: atrial pressure; MSV: cardiac output per minute) ,


 * significance in heart failure (reduction may lead to improvement).

Related Articles

 * Left cardiac catheterization
 * Central venous pressure
 * Pulmonary hypertension
 * Phlebogram

Used literature

 * DÍTĚ, P., et al. Vnitřní lékařství. 2. vydání. Praha : Galén, 2007.  ISBN 978-80-7262-496-6.
 * SILVESTRY, Frank E. Pulmonary artery catheterization: Interpretation of hemodynamic values and waveforms in adults [online]. UpToDate, Poslední revize 2020-01-14, [cit. 2020-05-13]. .