Mortality
0.055% (pulmonary artery rupture, diffuse intrapulmonary haemorrhage)
Serious adverse events
1.1%
Related to venous access site
0.4%
Related to right heart catheterization
0.3%
– Supraventricular tachycardia
0.1
– Hypertensive crisis
0.03
– Haemoptysis
0.01
– New bundle branch block
0.01
Blood samples for oxygen content, and pressure measurements are taken in all cardiac compartments (Fig. 13.1). Since the left atrium is not easily reached, as a representative of the left atrial pressure the pulmonary capillary wedge pressure (PCWP) is used. Figure 13.2 describes the principle of the PCWP measurement and how to measure it.
Fig. 13.1
Cardiac compartments. IVC inferior vena cava, SVC superior vena cava, RA right atrium, RV right ventricle, AP pulmonary artery, PCWP pulmonary capillary wedge pressure, Ao aorta, LA left atrium, LV left ventricle
Fig. 13.2
Pulmonary capillary wedge pressure. Because the pulmonary veins that enter the left atrium form a continuous system with the pulmonary arteries through the pulmonary capillaries, the pressure that is registered when a distal artery is occluded by the balloon inflation at the tip of the Swan Ganz is the same as in the left atrium. (a) Represents the situation when the Swan-Ganz catheter is situated in a small pulmonary artery branch before balloon inflation. (b) Represents the situation with ballon inflation. Note that the pressure at the tip of the catheter behind the inflated balloon becomes the same as in the left atrium. AP pulmonary artery, P A pulmonary arterial pressure, P B pressure with ballon inflation. Adapted with permission from Cardiale diagnostiek van pulmonale hypertensie, op zoek naar het cor pulmonale (in Dutch), Vliegen editor, Fig. 4.4, p13, publisher TTMA BV, Oegstgeest, The Netherlands
The order in which the various compartments are studied is left to the discretion of the operator. The only prerequisite is that every compartment is properly measured. The measurement of the pressures and registration of the wave-forms can best be obtained at end-expiration with open mouth.
Based on these measurements, calculation of various valvular, vascular function and cardiac output can be done using specific formula. Also, it allows for differentiation between various causes of pulmonary hypertension . Figure 13.3 explains the RA and PCWP wave forms. In Fig. 13.3b the typical wave forms of all right sided compartments are shown.
Fig. 13.3
(a) Specific pressure wave-forms of the RA and PCWP. Note that the atrial cycle is asynchronous with the ventricle, thus the atrial systole is the ventricular diastole and vice versa. A, C and V-are positive waves, X and Y are negative. And the ventricular systole is between C and Y. The a-wave is the atrial systole (the contraction of the atrium); the c-wave is formed by the rapid filling of the ventricle just before the AV-valve closes; The X descent is the atrial diastole (relaxation of the atrium); the V-wave is caused by filling of the atrium when the AV-valve is closed (the venous return towards the atrium). The height of the V-wave reflects the filling pressure of the ventricle. When the V-wave is high this may be a sign of heart failure. However, when the AV-valve is insufficient the regurgitation jet causes the filling of the atrium to increase and thus the V-wave to be more prominent. But when the AV-valve is insufficient the V-wave occurs early and is followed by a steep Y-descent. The Y-descent is the opening of the AV-valve and the rapid ventricular filling. As mentioned before the slope of the Y-descent points towards AV-valve insufficiency. But may also reflect pericardial constriction. Adapted with permission from Cardiale diagnostiek van pulmonale hypertensie, op zoek naar het cor pulmonale (in Dutch), Vliegen editor, Fig. 4.3, p12, publisher TTMA BV, Oegstgeest, The Netherlands. (b) Pressure wave forms in the various compartments of the right side of the heart. Every compartment has a characteristic pressure wave-form. The atrial (and AP-wedge) pressure wave forms have typical waves and descents that represent various parts of the cardiac cycle. ECG electrocardiogram, RA right atrium, AP pulmonary artery, AP-wedge pulmonary capillary wedge pressure, RV right ventricle
Tips and Tricks
Sometimes reaching the pulmonary artery can be a challenge. When there is tricuspid regurgitation the back-flow from the right ventricle into the right atrium may hamper advancing the catheter from the right atrium towards the right ventricle and the pulmonary artery.
There are several possible solutions. The first is to make a loop (Fig. 13.5c) in the right atrium and try to advance the catheter without inflated balloon tip. The backward pushing force is less with the deflated balloon and the loop in the right atrium increases the resistance of the catheter to overcome the backward pushing force of the regurgitant blood through the tricuspid valve.
If this is not sufficient one can insert a thin wire in the Swan Ganz catheter to stiffen the catheter and thus increase the pushability and stearability. When this is also not enough, then filling the balloon with saline in stead of air is the final easy resort. Usually any one of these tricks will help positioning the catheter at the site of interest.
When a tricuspid annuloplasty was performed any of the aforementioned tricks can be of help to finish the RHC successfully.
Hemodynamic Information from a RHC
As mentioned before, with a properly carried out RHC a multitude of hemodynamic information becomes available. As we will demonstrate this necessitates properly registered and measured wave-forms, saturations and pressures. Table 13.2 demonstrates the normal values of a RHC.
Table 13.2
Normal pressure values
Sat | Pressure (mean mm Hg) | Pressure (S/D mm Hg) | |
|---|---|---|---|
IVC | 80 | 0–5 | |
SVC | 70 | 0–5 | |
RA | 75 | 0–5 | |
RV | 30/4 | ||
PA | 70–75 | <24 | 30/15 |
PCWP | 4–10 | ||
Ao | 95–98 | ||
LVEDP | 95–98 | <12 |
Calculation of Cardiac Output
For the calculation of Cardiac Output ( CO) it is essential to obtain oxygen saturation measurements at various sites. Based on these values, CO can be calculated using Fick’s equation. As well, this allows for the interpretation of possible intra-cardiac shunts. The basics of these calculations is that the circulation is a closed circuit.
The formula for this calculation is called after the inventor of the calculation, Adolf Eugen Fick (1829–1901). The value of this parameter is important for both prognosis and also in cases of hemodynamic instability where inotropic therapy is instigated, for assessment of the effects of therapy. To calculate the cardiac output first the amount of consumption of oxygen from the air is measured (or calculated).
When we then know the amount of oxygen that enters the longs and the amount that exits the lungs, the amount of blood that has passed through to allow for this uptake can be calculated.
![$$ \mathrm{Cardiac}\\mathrm{Output}=\frac{{\mathrm{O}}_2\ \mathrm{consumption}}{1.36\times 1.6\times Hb\ \left(\mathrm{mmol}/\mathrm{L}\right)\times \left[\left( Sat\ \mathrm{Aorta}\right)-\left( Sat\ \mathrm{mixed}\\mathrm{venous}\right)/100\right]\times 10} $$](https://i0.wp.com/thoracickey.com/wp-content/uploads/2017/12/A978-3-319-58229-0_13_Chapter_TeX2GIF_Equa.gif?w=960)
The best way to get the O2 consumption is by means of real measurement. Since the O2 consumption can vary a lot in time, it is best to measure this as close to the time of RHC as possible. This is especially true for patients with pulmonary pathology.
If measurement is not possible or not available. An educated guess can be obtained by calculating the O2 consumption. For this calculation the following equation comes closest to the actual measured values [6].
O2 consumption = (157.3 × BSA + 10 × constant (male = 1; female = 0)–10.5 × ln (Age) + 4.8) mL/min [6]. This calculation is rather difficult to calculate.
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