Continuing Education Activity
Pulmonary capillary wedge pressure (PCWP) is frequently used to assess left ventricular filling, represent left atrial pressure, and assess mitral valve function. Right heart catheterization remains a vital tool in the diagnosis, prognostic evaluation, and management of patients with suspected pulmonary hypertension (PH) and selected heart failure patients. This activity outlines and reviews the role of the interprofessional team in evaluating and treating patients who undergo right heart catheterization for assessment of pulmonary capillary wedge pressure.
Objectives:
Review the pathophysiology of pulmonary capillary wedge pressure.
Identify the indications for checking pulmonary capillary wedge pressure.
Outline the most common adverse events associated with right heart catheterization.
Explain the importance of collaboration and communication among the interprofessional team to ensure the appropriate selection of candidates to measure pulmonary capillary wedge pressure and to improve outcomes of patients undergoing this procedure.
Access free multiple choice questions on this topic.
Introduction
Pulmonary capillary wedge pressure (PCWP) is frequently used to assess left ventricular filling, represent left atrial pressure, and assess mitral valve function. It is measured by inserting a balloon-tipped, multi-lumen catheter (Swan-Ganz catheter) into a central vein and advancing it into a pulmonary artery branch. The balloon is then inflated, occluding the branch of the pulmonary artery and providing a pressure reading equivalent to the left atrial pressure.
Right heart catheterization (RHC) is an invasive procedure that requires expertise and close monitoring. This was first described in the eighteenth century, and since then, the procedure and its applications have grown significantly.[1] Although widely used in the past, the failure of multiple studies to demonstrate any benefit of RHC in patients with advanced heart failure or cardiogenic shock has reduced its utility in everyday practice.[2][3] Nonetheless, RHC remains a vital tool in the diagnosis, prognostic evaluation, and management of patients with suspected pulmonary hypertension (PH) and selected heart failure patients.
Anatomy and Physiology
To measure the PCWP, a catheter is inserted through a central vein (either femoral, subclavian, or internal jugular) and advanced into the superior or inferior vena cava to reach the right atrium. The internal jugular vein is the preferred access.[4] From the right atrium, the catheter is advanced through the tricuspid valve into the right ventricle. Once in the right ventricle, the catheter is advanced to the right ventricular outflow tract, then to the pulmonary artery after crossing the pulmonic valve. The tip of the catheter lies in the main pulmonary artery, where the balloon can be inflated to measure the pulmonary capillary wedge pressure. In most cases, the PCWP is also an estimate of left ventricular end-diastolic pressure (LVEDP). The normal pulmonary capillary wedge pressure is between 4 and 12 mmHg. Elevated levels of PCWP might indicate severe left ventricular failure or severe mitral stenosis.
The location of the catheter can be determined by the waveform on the monitor or by measuring systolic and diastolic pressures at the catheter tip. In the right atrium, both the diastolic and the systolic pressure are usually less than 5 mmHg (with mild variations). While in the right ventricle, the systolic pressure is about 25 mmHg, and the diastolic pressure remains similar to right atrial diastolic pressure (<5 mmHg). In contrast, the pulmonary artery systolic pressure is similar to the right ventricular systolic pressure in the absence of pulmonic stenosis, but the diastolic pressure increases to about 10 mmHg.
Indications
Measurement of the PCWP
Contraindications
Absolute Contraindications
Relative Contraindications
Equipment
The pulmonary artery catheter or Swan-Ganz catheter is usually between 60 and 110 cm in length and around 4 to 8Fr in caliber. It was named after its inventors, Jeremy Swan and William Ganz.[11]
Most pulmonary artery catheters have 4 separate lumens, each serving a specific function.
The proximal lumen, or blue port, is located in the right atrium and measures right atrial pressure. It can also be used to administer medications. Some pulmonary artery catheters may have a separate lumen for drug infusion.
The distal lumen, or yellow port, is located at the distal end of the catheter and is in the pulmonary artery. It is used to monitor pulmonary artery pressures and to obtain a mixed venous sample. Medications and infusions should not be inserted through this port.
The red port is for balloon inflation and deflation. The balloon sits approximately 2 cm from the distal end of the catheter. Each pulmonary artery catheter is accompanied by a 1.5 ml syringe used to inflate or deflate the balloon. The inflated balloon helps to guide the catheter from the right atrium into the pulmonary artery by following intracardiac blood flow. The inflated balloon also helps to measure the PCWP.
A temperature or a thermistor is used to measure core temperature in the pulmonary artery. This helps to measure the cardiac output via the thermodilution method.
Technique or Treatment
Before performing any procedure, it is important to perform a time-out. During the time out, the healthcare team performing the procedure should 1) verify the patient's details, 2) confirm the procedure and site, 3) ensure patient consent, 4) ensure normal labs, 5) review patient medications, and 6) ensure appropriate personnel and equipment are at the bedside. The most commonly accessed vein for the RHC is the internal jugular vein. Usually, an ultrasound is used to locate the vein and guide the needle. The ultrasound also helps assess the location of the nearby artery, confirm the vessel's patency, and ensure there is no thrombus within the vessel lumen. Although it can be performed without ultrasound, imaging guidance has been shown to reduce complications.[12][13][14]
The first step of the procedure is to clean the area with an antiseptic solution, and the patient is draped to make a sterile working field. Using a vascular probe, the vessel's position is confirmed again. Following this, local anesthesia is provided at the site of insertion. The central vein is then punctured with the needle provided, and a guidewire is introduced into the vein by the Seldinger technique. Ultrasound can be used to confirm the guidewire's position within the vein. After the guidewire is confirmed to be in place, the needle is removed. A scalpel blade is then used to make a 3 to 4 mm incision adjacent to the guidewire to ensure easy passage of the dilator. Care should be taken not to cut the guidewire. An 8.5 Fr dilator with an introducer sheath is inserted over the wire into the vein. The wire and dilator assembly should then be removed together as a unit, leaving the introducer sheath in place. Once the introducer sheath is in position, the pulmonary artery catheter is inserted through it and advanced up to 20 cm. This should place its distal tip within the right atrium, which can be confirmed on the monitor with a right atrial pressure waveform. Once the position inside the right atrium is confirmed, the balloon is then inflated with air using the 1.5 mm syringe. The catheter is then advanced into the right ventricle and then into the pulmonary artery. The advancements are confirmed by checking the appropriate waveforms and pressures on the monitor. Once the catheter is advanced into the pulmonary artery until the waveform changes to a wedge shape, the balloon should be deflated. The catheter then shows the pulmonary artery pressures. After obtaining the appropriate pulmonary artery pressures, a PCWP/pulmonary artery occlusion pressure can now be measured. This is done by slowly inflating the balloon while monitoring the monitor. The balloon is inflated only until the pulmonary artery pressure waveform changes into a wedged waveform. When the balloon is inflated, it creates a static column of blood between the artery distal to the catheter and the pulmonary vein. This post-capillary pressure, known as the PCWP, is an indirect estimate of the pressure in the left atrium. Once the procedure is complete, a chest X-ray should be ordered to confirm the catheter's position and check for any complications. The tip of the pulmonary artery catheter should not extend beyond 2 cm of the hilum and is usually within the mediastinal shadow.[15]
The utility of RHC depends on the accuracy and completeness of the data obtained. Essential measurements during the procedure include:
Oxygen saturation (superior vena cava, inferior vena cava, pulmonary artery, sinoatrial)
Right atrial pressure
Right ventricular pressure
Pulmonary artery pressure
Left heart filling pressure (wedge pressure, left atrial pressure, or LVEDP)
Cardiac output/cardiac index
Pulmonary vascular resistance
Systemic blood pressure
Heart rate
Response to acute vasodilators
Misinterpretation of the wedge pressure is a common pitfall in the invasive diagnosis of pulmonary hypertension. The wedge pressure should be measured at end-expiration and in several different segments of the pulmonary vasculature. LVEDP should be obtained if there is any doubt about the accuracy of the wedge pressure tracing or if the results are unexpected in a given patient. A fluid challenge may be necessary to elicit diastolic dysfunction. Of note, operators should proceed early with trans-septal LA catheterization for patients with mitral valve disease or prior mitral valve replacement.
Complications
Pulmonary artery catheterization is an invasive procedure that carries innate risks. Several complications have been described following the procedure, with studies noting that the occurrence of complications is between 5% and 10%.[16] The most common complications that can occur as a result of this procedure include: arrhythmias, thromboembolism, pulmonary ischemia, hemoptysis, pulmonary hemorrhage, perforation of the pulmonary artery, catheter knotting, arterial puncture, hematoma, and local infection, which can occur during or after the procedure.[17][18]
Clinical Significance
As mentioned before, PCWP is a reasonable surrogate marker of left atrial pressure and LVEDP. It is helpful to measure PCWP to diagnose the severity of left ventricular failure and quantify the degree of mitral valve stenosis. By measuring PCWP, the clinician can titrate the doses of diuretics and other drugs used to reduce pulmonary venous and capillary pressures, thereby reducing pulmonary edema. Therefore, it can also guide therapeutic efficacy.
It is also used to evaluate and diagnose pulmonary arterial hypertension (PAH), as patients with group 1 PAH have PCWP ≤15 mmHg.[19] Furthermore, it is used to calculate pulmonary blood flow, along with pulmonary artery pressure. PCWP is also useful for differentiating cardiogenic shock (PCWP >15 mmHg) from non-cardiogenic shock (PCWP ≤15 mmHg). It is also used to evaluate blood volume status and guide fluid administration during hypotensive shock, with a PCWP goal of 12-14 mmHg.
Enhancing Healthcare Team Outcomes
Pulmonary capillary wedge pressure is an integrated measurement of the compliance of the left side of the heart and the pulmonary circulation. The measurement of PCWP can be useful in several diagnostic settings. However, since it involves an invasive procedure, a thorough understanding of the equipment, its indications, and contraindications is vital for all healthcare professionals involved. Several published guidelines help identify the role of pulmonary artery catheterization in a particular setting.[20] A basic understanding of the technique can also help the ancillary staff provide appropriate support to the operator performing the procedure and ensure all necessary precautions are taken. Such a team approach can help minimize complications and improve patient outcomes.
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Disclosure: Raunak Nair declares no relevant financial relationships with ineligible companies.
Disclosure: Nader Lamaa declares no relevant financial relationships with ineligible companies.
