Right Heart Cardiac Catheterization

Anatomy and Physiology

Right heart catheterization is commonly performed by accessing the leg's common femoral vein, the neck's internal jugular vein, or the arm's antecubital veins. In the leg, the femoral vein becomes the external iliac vein and drains into the inferior vena cava, draining into the right atrium.[4] The cephalic vein in the arm drains into the subclavian vein, which then drains into the right atrium.[5] In the neck, the internal jugular vein joins the subclavian vein and forms the brachiocephalic vein. The brachiocephalic veins from both sides drain into the superior vena cava, which drains into the right atrium.[6] Antecubital venous access has been associated with shorter procedure time and lower chances of significant hematomas.[7]

Indications

The following are indications for right heart catheterization:

• Suspected cardiogenic shock
• Evaluation of a patient with dyspnea to diagnose or exclude pulmonary hypertension, constrictive pericardial disease, restrictive cardiomyopathy, and heart failure with a preserved ejection fraction
• Determine the response to vasodilator therapy in pulmonary hypertension
• Cardiac tamponade
• Intracardiac left-to-right shunt quantification
• Guiding fluid management and hemodynamic monitoring of patients after surgery or complicated myocardial infarction, heart failure, shock [8]
• Adult congenital heart disease
• Evaluation for cardiac transplantation
• Surveillance status postcardiac transplant
• Postcardiac transplant with new or worsening symptoms suggestive of graft rejection
• Preimplantation assessment of left ventricular assist devices
• Postimplantation optimization after left ventricular assist device placement
• In valve disease, when there are discrepancies between clinical presentation and noninvasive diagnostic testing [9][10][11][12][13]

Contraindications

Absolute contraindications include right-sided endocarditis, right-sided tumor, or thrombus. Relative contraindications include severe coagulopathy or bleeding diathesis. Appropriate caution should be exercised in the setting of arrhythmias, left bundle branch block, to avoid provoking dysrhythmias.[14]

Equipment

Several types of pulmonary artery catheters are commercially available. Some can be used to perform the thermodilution assessment of cardiac output in addition to pressure measurements. Catheters with a dedicated thermistor can be used to perform thermodilution cardiac output assessment. The pulmonary artery catheter is 110 cm in length, and catheter sizes vary, with French sizes ranging from 5F to 8F depending on the manufacturer. All catheters have a distal yellow port and a proximal blue port. The presence of a thermistor adds a third port to the catheter.[11]

Personnel

When the procedure is performed in the cardiac catheterization lab, there is a performing clinician, a nurse who can administer medications, and a monitoring technologist to record the data obtained. A cardiovascular technologist usually assists the performing clinician.[15]

Preparation

After obtaining informed consent, the patient is brought to the cardiac catheterization lab. The patient is placed in the supine position on the table, and the access sites are cleaned and draped in a sterile fashion. For providing a sterile access site, chlorhexidine is used. The operating physician and the assistant will require sterile gowns, gloves, head caps, and facial protection. The needles, access sheaths, and catheters are flushed to prevent the introduction of air into the systemic circulation.[14]

Technique or Treatment

A local anesthetic is administered subcutaneously at the site of access. Venous access is obtained with or without ultrasound guidance. In the femoral and jugular sites, access can be obtained using a standard 18-gauge needle or a smaller 21-gauge needle. In the case of the antecubital vein, using the 21-gauge needle may reduce the chances of injury to nearby arterial structures. Ultrasound guidance requires a sterile ultrasound probe sleeve to prevent contaminating the rest of the sterile field.

Once venous access is obtained, an appropriately sized sheath is secured in the vein. The pulmonary artery catheter is advanced through the sheath into the vein. The balloon is inflated after the catheter is advanced to roughly 15 cm to avoid inflating it within the access sheath. Balloon inflation will make advancing the catheter to the right atrium much easier. If the catheter advances easily, wire cannulation is not necessary. The catheter will reach the right atrium from the internal jugular vein when it is advanced to roughly 20 cm. From the femoral venous access site, the catheter will reach the right atrium when advanced to approximately 45 cm in length. Nonetheless, the catheter movement can also be observed using fluoroscopy. 

A pulsatile right atrial waveform will be observed when the catheter reaches the right atrium. Before recording pressures, the system is zeroed to establish a reference; zeroing involves opening the air-fluid transducer to air to equilibrate with atmospheric pressure. When this is being performed, the air-fluid transducer must be at the level of the heart. Roughly, this is performed by holding the air-fluid transducer at the level of the fourth intercostal space, at an imaginary plane between the anterior and the posterior chest walls. Observed pressures may be falsely elevated if the transducer is positioned below heart level and falsely decreased if the transducer is above heart level.

Once the right atrial pressure waveform is obtained, the catheter is manipulated to direct it towards the right ventricle, and right ventricular pressure is recorded. Following this, the catheter is usually advanced to a wedge position to measure the pulmonary capillary wedge pressure. Once this is completed, the balloon can be deflated and brought back a few cms into the pulmonary artery, where pulmonary artery pressure can be recorded.

Importantly, all pressures should be measured ideally at end-expiration. The pulmonary artery blood sample is withdrawn using the distal yellow port, and mixed venous oxygen saturation is obtained. Arterial saturation must be obtained separately to determine cardiac output using the Fick method. Thermodilution can be performed by injecting cold saline into the proximal blue port into the right atrium, where it mixes with blood, and a thermistor detects the temperature difference. Thermodilution has been repeated a minimum of 3 times to obtain an average cardiac output and index. The pulmonary artery catheter can be manipulated and placed in the superior or inferior vena cava to withdraw blood samples and estimate oxygen saturations. The same can be done in the right ventricle or the right atrium.[11][12]

Complications

Possible complications include ventricular arrhythmias and right bundle branch block, which are usually transient and resolve once the catheter is removed or the catheter tip position is adjusted. Very rarely, a complete heart block in the setting of a prior left bundle branch block can occur, which may require temporary pacemaker placement. Air embolism can occur if there is air in the catheters or the fluid-filled pressure transducers. The patient can manifest with the sudden onset of chest pain, dyspnea, hypotension, and tachycardia. If this is suspected, the patient should be placed in the Trendelenburg position, and high-flow oxygen must be administered; this helps reduce the nitrogen in the blood and promotes the reabsorption of the injected air. In some situations, hyperbaric oxygen therapy is required.

The rate of pulmonary artery perforation is 0.03%, which can occur in the setting of prolonged balloon inflation and distal placement of the catheter into the pulmonary arteries for wedge pressure measurement, particularly in patients with prior pulmonary hypertension and systemic anticoagulation. This can manifest as sudden dyspnea and cardiogenic shock. Fluoroscopy can help identify if the tip of the catheter is very distal in the pulmonary artery branches. If this occurs, the catheter should be left in place with the balloon inflated to minimize pulmonary hemorrhage. The patient should be emergently intubated with a double-lumen endotracheal tube and placed in the lateral decubitus position with the affected side down to protect the unaffected side from the ongoing hemorrhage. Emergent surgery or embolization should be considered. The potential complications for indwelling pulmonary artery catheters include access site infection, pulmonary infarction, right-sided chamber or pulmonary artery perforation, arrhythmias, and thrombosis of the accessed vein.[14]

Clinical Significance

Various pressure measurements and hemodynamic parameters can be obtained during a right heart catheterization. The common parameters evaluated, along with the hemodynamic profiles of commonly encountered scenarios, are described in the following sections. The normal mean right atrial pressure ranges from 1 to 5 mm Hg. Normal right ventricular systolic and diastolic pressures are 15 to 30 mm Hg and 1 to 7 mm Hg, respectively. Normal pulmonary artery systolic and diastolic pressures are 15 to 30 mm Hg and 4 to 12 mm Hg, respectively. The mean pulmonary artery pressure is typically around 15 mm Hg. Normal pulmonary capillary wedge pressure is 4 to 12 mm Hg.[14] The measured pressures can be used to calculate cardiac output, cardiac index, pulmonary vascular resistance, systemic vascular resistance, stroke work index, right ventricular stroke work, pulmonary artery pulsatility index, the Gorlin equation to calculate mitral and aortic valve areas, and the Hakki equation to calculate aortic valve area.[12][16]

Right Atrial or Pulmonary Capillary Wedge Pressure Waveforms

The right atrial pressure waveform consists of 3 positive upstrokes and 2 descents. The first positive upstroke is the “a” wave that correlates with atrial systole. This is followed by the “x” descent that signifies atrial relaxation. The next wave is the “c” wave, which indicates tricuspid valve closure. The next wave is a positive upstroke “v” wave representing passive atrial filling during right ventricular contraction. The “v” wave is followed by the ‘y” descent, representing atrial emptying after the tricuspid valve opens in ventricular diastole. The pulmonary capillary wedge waveform is similar to the right atrial pressure waveform and consists of 3 positive upstrokes and 2 downstrokes.[14]

In the setting of atrial fibrillation, there is a loss of the “a” wave due to the loss of the atrial contribution to the waveform. Tall “a” waves can occur due to an increase in atrial pressure that can occur in tricuspid or mitral stenosis. Cannon “a” waves are very large “a” waves that are caused by any condition that can cause atrioventricular dissociation, such as complete heart block, ventricular tachycardia, and atrioventricular nodal reentrant tachycardia. Large “v” waves occur due to increased ventricular volume during right ventricular contraction, like tricuspid or mitral regurgitation, right or left ventricular failure, severe noncompliance of the right or left ventricle, or a ventricular septal defect.

Also, mitral stenosis, postoperative or rheumatic atrium changes, can produce large atrial “v” waves.[17] A very rapid “y” descent is due to rapid diastolic filling of the ventricle that can occur in constrictive pericarditis. Similarly, a rapid “x” descent occurs in constrictive pericarditis.[18] The “y” descent is absent in cardiac tamponade as there is an equalization of diastolic pressures, and the ventricular diastolic pressure does not fall enough to allow for complete diastolic filling.[12]

Right Ventricle Systolic and Diastolic Pressures

Right ventricular and pulmonary artery systolic pressures are elevated in pulmonary embolism and pulmonary hypertension.[19][20] Constrictive pericarditis, restrictive cardiomyopathy, and cardiac tamponade cause increased and equalized end-diastolic pressures, as well as elevated pulmonary capillary wedge pressures. However, in constrictive pericarditis, ventricular interdependence is best identified by simultaneous right and left heart catheterization. Interdependence results in discordance between right and left ventricular pressures, as evidenced by a reduction in the right ventricular systolic pressure tracing when left ventricular pressure increases, and vice versa, with respiration.

In restrictive cardiomyopathy, there is no interdependence; therefore, there is a concordance of right and left ventricular pressures on simultaneous measurement. Concordance is evidenced by concordant right ventricle and left ventricle systolic pressure tracings with respiration. This is mathematically calculated as the systolic area index, which is defined as the ratio of the right ventricle to the left ventricle area in inspiration versus expiration. A systolic area index greater than 1.1 has a greater than 95% sensitivity in identifying constrictive pericarditis. Even though various parameters have been developed to distinguish between constrictive pericarditis and restrictive cardiomyopathy, the systolic area index appears to have the best predictive accuracy. While the clinical presentation of constrictive pericarditis and restrictive cardiomyopathy is mostly chronic, cardiac tamponade physiology is frequently acute.[18][21] 

Cardiac Output

As measured by right heart catheterization, cardiac output is typically calculated using the indirect Fick principle and the thermodilution technique. Adolf Fick developed the Fick principle in 1870, observing that the blood volume required to transport that amount of oxygen could be calculated by measuring the amount of oxygen carried in the systemic and pulmonary circulation. This method requires the following parameters: hemoglobin levels, central arterial and venous oxygen saturation, and maximum oxygen consumption values. The maximum oxygen consumption is assumed to be 250 mL/minute, or 125 mL/min/method involves directly measuring oxygen consumption using exhaled air. This is cumbersome and requires specialized equipment. Therefore, the indirect Fick method, which uses the assumed maximum oxygen consumption value, is widely used. However, it has been shown that cardiac output derived by the indirect Fick method varies from that derived by the direct Fick method by roughly 25% in up to 25% of individuals. These differences appear more pronounced in individuals with a body mass index greater than 40 kg/m².[22][23][24] 

For thermodilution, 10 cc of saline is injected using the proximal blue port of the pulmonary artery catheter. This mixes with the right atrial blood and causes a slight drop in temperature, which is then detected by the thermistor at the tip of the catheter. However, there are pitfalls to the thermodilution technique. The thermodilution technique is unreliable when cardiac output is low, as the reduced area under the curve may cause an underestimation of output. Severe tricuspid or pulmonic valve regurgitation leads to blood recirculation, resulting in falsely low cardiac output measurements. Conversely, intracardiac shunts can cause overestimation by altering indicator dilution. Clinicians should interpret thermodilution data cautiously in these conditions and consider alternative assessment methods when necessary. Clinicians must also be aware of the pitfalls associated with these measurements, as Fick and thermodilution techniques can yield variable results for the same patient.[12][24]

Cardiac Index

The cardiac index is calculated by indexing the cardiac output for body surface area. Normal cardiac output can be variable based on body mass and size. However, a normal cardiac index is greater than 2.5 L/min/m². Cardiogenic shock is an index of less than 2.2 L/min/m² with a pulmonary capillary wedge pressure greater than 15 mm Hg.[25][26] 

Cardiac Power Index

Cardiac power output is calculated in Watts and is obtained by dividing the product of mean arterial pressure and cardiac output in liters per minute by 451. The cardiac power index is the cardiac power output indexed to the body's surface area. Cardiac power output of less than 0.6 W strongly correlates with in-hospital mortality in patients with shock. In cardiogenic shock, cardiac power output correlates more with adverse outcomes than cardiac index, ejection fraction, pulmonary artery systolic pressure, and mean arterial pressure.[27]

Systemic and Pulmonary Vascular Resistance

The following equation calculates systemic vascular resistance:

• (Mean arterial pressure – right atrial pressure) x 80 / cardiac output

Systemic vascular resistance is measured in Wood units (WU) or dynes/second/cm². The normal range is 700 to 1600 dynes/second/cm or 10 to 20 WU.

Similarly, pulmonary vascular resistance is calculated by the equation:

• (Mean pulmonary artery pressure – pulmonary capillary wedge pressure) x 80/ cardiac output

Pulmonary vascular resistance is measured in WU or dynes per second per cm². The normal range is 20 to 120 dynes/second/cm or less than 2 WU.[12]

Pulmonary Artery Pulsatility Index

The pulmonary artery pulsatility index is the ratio of pulmonary artery pressure to right atrial pressure and is calculated by the following equation:

• (Systolic pulmonary artery pressure – diastolic pulmonary artery pressure)/right atrial pressure 

A pulmonary artery pulsatility index of less than 0.9 has very high sensitivity and specificity in predicting right ventricular failure and in-hospital mortality in acute inferior wall myocardial infarction.[16] A pulmonary artery pulsatility index of less than 1.85 is also used to predict if patients will experience right ventricular failure and thereby require right ventricular hemodynamic device support after placement of left ventricular assist devices.[28][29] This measurement is also used to predict adverse outcomes in patients with chronic right heart failure.[30]

Enhancing Healthcare Team Outcomes

Right heart cardiac catheterization is a vital diagnostic procedure used to evaluate hemodynamics in patients with suspected or known pulmonary hypertension, heart failure, valvular disease, or congenital heart anomalies. Physicians and advanced practitioners performing the procedure must have technical proficiency in catheter manipulation, waveform interpretation, and pressure measurement across cardiac chambers and the pulmonary artery. Accurate data collection is crucial for informing treatment decisions, such as initiating or adjusting pulmonary vasodilator therapy or assessing transplant candidacy. A systematic strategy includes proper patient selection, adherence to sterile technique, real-time monitoring, and the ability to recognize and manage potential complications, such as arrhythmias or vascular injury.

Effective interprofessional communication and care coordination significantly improve patient safety and outcomes during right heart catheterization. Nurses are crucial in preprocedure education, intravenous access, patient monitoring, and post-procedure observation for potential complications. Pharmacists support using sedatives, anticoagulants, and pulmonary vasodilators safely and effectively during vasoreactivity testing. Respiratory therapists may assist in monitoring oxygenation and ventilatory support, particularly in those who are critically ill. Clear communication among team members ensures timely documentation, patient handoffs, and adherence to clinical protocols. This collaborative approach fosters a patient-centered experience, minimizes procedural risks, and enhances diagnostic accuracy and therapeutic outcomes.

Nursing, Allied Health, and Interprofessional Team Monitoring

Right heart catheterization appears to be generally performed in patients with cardiac and pulmonary disorders. These patients receive multidisciplinary care from their primary care physicians, pulmonologists, and cardiologists. Conditions that could be appropriately diagnosed or excluded by right heart catheterization must be recognized.

Additionally, the optimal performance of these procedures relies on the entire team, including the nurse and cardiovascular technologists, to ensure safety against potential risks and complications of the procedure. Identifying potential issues with the fluid-filled transducer system and recognizing abnormal waveforms due to technical problems is crucial for right heart catheterization. The Society for Cardiovascular Angiography and Interventions has developed best practice guidelines for cardiac catheterization procedures, which help adhere to national and international standards.