Indications

• Titration of inotropes and vasopressors during cardiogenic shock.
• Patients receiving advanced mechanical circulatory support.
• Hemodynamic assessment and/or monitoring in specific cardiac conditions: valvular disease,  tamponade, constrictive pericarditis, restrictive cardiomyopathy, intracardiac shunts, pulmonary hypertension, congenital cardiac diseases, pre-cardiac transplant.

Contraindications

• Absolute:
  • Mechanical right heart valve.
  • Right-sided endocarditis, thrombus or mass (risk of embolization to pulmonary artery).
• Relative:
  • Coagulopathy (often can still be completed after holding anticoagulation or transfusing platelets/FFP prior to procedure).
  • Caution in recent pacemaker or ICD placement though usually safe to perform.
  • LBBB (risk of inducing complete heart block).
  • Infection overlying the site.
  • Inability to lay flat.
  • Pregnancy (always check women of child-bearing age, pregnant patients can be double shielded during fluoroscopy).

PAC hardware

An air-filled syringe (A) is used to inflate the balloon at the catheter tip (inset). An accessory infusion port (B) is present in most catheters and connects to a lumen 30 cm from the catheter tip (arrow). The distal port (C) connects to a lumen at the catheter tip and is used to measure all pressures during catheter insertion. The proximal port (D) connects to an additional lumen 30 cm from the catheter tip and is used to monitor right atrial pressures once the catheter tip is in the pulmonary artery. A thermistor wire extends from the catheter tip to an electronic connector (E) and is used to measure cardiac output by means of thermodilution.

Note: number and color of ports listed may vary by manufacturer.

Placement

• Preference is to place under fluoroscopy in cardiac catheterization lab unless the patient is too unstable, in which case the PAC can be placed at bedside.
  • Cath lab: safest location is brachial vein but if the PAC is retained then the catheter must be placed through a central vein with preference of internal jugular (IJ) > femoral > subclavian.
  • Bedside: prefer right IJ > left subclavian. Placement from the femoral approach should not be attempted at the bedside.
• Obtain post-placement CXR if PA catheter is placed via the IJ or subclavian route (r/o PTX 1-3%, verify position in the PA).
• Always have balloon up when advancing and deflated when withdrawing.

Complications

• Atrial arrhythmia (PAC, NSVT) or ventricular arrhythmia (rare).
• RBBB (usually transient) and complete heart block in patients with preexisting LBBB.
• Catheter knotting.
• Air embolism if ports are not properly flushed.
  • Presents with dyspnea, chest pain, obstructive shock with high right-sided pressures.
  • Management: place patient in Trendelenberg to trap air in RV apex and prevent it from obstructing RVOT.
• PA perforation (rarely occurs <1% though carries 50% mortality).
  • Risk factors: prolonged balloon inflation, pulmonary hypertension, systemic anticoagulation.
  • Occurs when advancing with balloon down into pulmonary artery then inflating.
  • Presents with sudden hemoptysis, hypoxemia and shock.
  • Place patient in lateral decubitus with bleeding lung down, intubate with dual lumen ET tube. Emergently contact interventional cardiology and CT surgery.
• Pulmonary infarction with prolonged balloon inflation.
• Catheter-related infection and thrombosis.

Measurements and Normal Value

Regardless of the mode of ventilation all measurements should be made at end-expiration when the intra-thoracic pressure is closest to zero.

• Measured values:

*PCWP reflects the LA pressure and can estimate LVEDP (LV preload) but does not directly measure this and should be interpreted with caution in multiple conditions including mitral valve disease, pulmonary embolus or pulmonary veno-occlusive disease, LV diastolic dysfunction and aortic regurgitation.

• Calculated values:

• Thermodilution: a known volume of indicator fluid is injected into the proximal port in the right atrium and the change in blood temperature at the distal port in the pulmonary artery is measured. The area under the temperature-time curve is inversely proportional to the flow rate in the pulmonary artery, which is determined by the CO of the left ventricle. This flow rate is considered an estimate CO, assuming that there is no intracardiac shunt.
  • Measurements are inaccurate in moderate to severe tricuspid regurgitation, intracardiac shunts and hypothermic patients (e.g. during TTM).
• Fick equation: CO is calculated from the difference in oxygen saturation between the arterial and venous blood (AVO2 difference) as well as the rate of oxygen consumption at the time the arterial and venous blood samples are drawn. Oxygen consumption can be calculated directly but is most often estimated by validated equations.

Online calculator: https://www.mdcalc.com/cardiac-output-ficks-formula#evidence

CO: cardiac output (L/min)
Oxygen consumption (mL/min)
SaO2: arterial oxygen saturation
SvO2: mixed venous oxygen saturation, measured in the pulmonary artery and includes blood returning to the heart from the SVC, IVC and coronary sinus

Note: cardiac index is the cardiac output normalized by body surface area (CO/BSA).

• Systemic vascular resistance (SVR in dyn-sec/cm^-5) and pulmonary vascular resistance (PVR in WU):

MAP: mean arterial pressure (mmHg)
Mean RAP: mean right atrial pressure (mmHg)
CO: cardiac output (L/min)
Mean PAP: mean pulmonary artery pressure (mmHg)
PCWP: pulmonary capillary wedge pressure (mmHg)

Interpretation of Waveforms

• RA waveform (see section Jugular Venous Pulsations): 

Findings in Specific Disorders

• Mitral regurgitation: large v waves transmitted to PCWP position.
• Tricuspid regurgitation: accentuated RA v wave with steep y descent and elevated mean RA pressure.
• Cardiac tamponade: elevation and equalization of RA, PA diastolic, and PCWP, dominant x descent, attenuated y descent, decreased or unchanged RA pressure with inspiration.
• Constrictive pericarditis: increased RAP, RV and PA pressures with prominent x descent and prominent y descent; inspiration causes unchanged or increased RA pressure and increased RV systolic pressure.
• Cardiogenic shock: low CO, high SVR, high PCWP.
• Distributive shock: normal/high CO, low SVR, normal/low PCWP.
• Hypovolemic shock: Normal CO, high SVR, low PCWP.

Fleitman, J. Pulmonary artery catheterization: Interpretation of hemodynamic values and waveforms in adults. UpToDate, https://www.uptodate.com/contents/pulmonary-artery-catheterization-interpretation-of-hemodynamic-values-and-waveforms-in-adults#H10

Kelly CR, Rabbani LE. Pulmonary-Artery Catheterization N Engl J Med 2013.