Keywords

FormalPara About Us

The authors are cardiologists working in the Pulmonary Hypertension and Heart Failure Clinic in the Department of Cardiology at the Erasme Hospital, the academic institution of the Université Libre de Bruxelles in Belgium. The center hosts a specialized unit of national and international reputation, which manages patients with all forms of pulmonary vascular disorders and end-stage heart failure. Their scientific interest encompasses research from bench to bedside in pulmonary circulation and right ventricular function, with a strong emphasis on hemodynamics, physiology, and pathophysiology. Professor Vachiery is coauthor of the European Society of Cardiology and European Respiratory Society guidelines on the diagnosis and management of pulmonary hypertension.

Introduction

  • Despite advances in imaging, right heart catheterization (RHC), also called pulmonary artery catheterization, is the gold standard for the assessment of the pulmonary circulation and the right ventricle in healthy and disease states. RHC is mandatory to establish the diagnosis of pulmonary hypertension (PH), to assess disease severity, and to determine prognosis and response to therapy [1, 2].

  • In addition, it remains a critical tool in the assessment of patients who are candidates for heart transplantation [3] and may be considered in various cardiac disorders.

  • Contrary to popular belief, the procedure is rather safe, even in advanced cases. A recent retrospective and prospective multicenter study reported a procedure-related mortality of 0.055% and morbidity of 1.1% in specialized centers of PH [4].

  • RHC is a technically demanding procedure that requires meticulous attention to detail and accuracy in interpretation to obtain clinically useful information. It must always be integrated in the general assessment of a patient’s condition, which includes the clinical context and imaging, in particular echocardiography.

  • To obtain high-quality results and minimize the risk of complication, physicians appropriately trained in handling and interpretation of the test should perform the procedure in expert centers.

Goals, Indications, and Contraindications of Right Heart Catheterization

  • RHC must be performed to establish the differential diagnosis of PH, as it provides a measurement of pulmonary pressures, right- and left-heart filling pressures, cardiac output, and staged oxygen saturation.

  • The procedure is mandatory before embarking on a treatment for the most severe form of PH such as pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH).

  • In heart failure (HF), RHC is necessary in the assessment of candidates for heart transplantation and implantation of left ventricular assist devices (LVAD).

  • In PH and HF, it is also commonly used to establish prognosis and monitor the efficacy of more invasive therapies.

  • In the intensive care unit (ICU) setting, RHC has been in a “love-hate” relationship with intensivists. Nevertheless, recent technical advances in monitoring and clinical trials have reestablished a role for RHC in the assessment of ICU patients, especially in shock condition and in patients with suspected cardiac diseases.

  • The indications of RHC are presented in Table 6.1. Although rare, there are some contraindications to the procedure (Table 6.2), both technical (center dependent) and clinical (patient dependent).

Table 6.1 Indications for right heart catheterization
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Table 6.2 Contraindications for right heart catheterization
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Procedure: Preparation and Insertion of Right Heart Catheter

  • RHC requires prior patient’s consent. In addition, it needs to be performed in an appropriate environment, which includes staff and technical facilities. In particular, blood pressure, heart rate (HR), and oxygen saturation must be monitored throughout the procedure.

  • All equipment to deliver cardiorespiratory resuscitation, oxygen, and vasopressors must be available in case of shock and cardiac arrest.

  • One physician can perform RHC but nursing staff (at least one) must be present throughout the procedure. The most common device used for RHC is a triple-lumen Swan-Ganz catheter . This flexible fluid-filled catheter has two pressure ports (one at the tip for pulmonary arterial pressure (PAP) measurements, and one 30 cm from the tip to allow for injection of saline and measurement of right atrial pressure (RAP)) and one closed lumen to inflate a balloon at the tip for the measurement of pulmonary artery wedge pressure (PAWP). A more rigid, non-floated, balloon-free catheter is sometimes used in the cath lab but it does not permit the measurement of cardiac output.

The following describes the step-by-step procedure to provide keys to an uneventful procedure:

  • Preparation

    • Review of indications and contraindications

    • Patient’s information and collection of informed consent

    • Decision on insertion site (jugular versus femoral, antecubital, or subclavian approach), based on patient’s anatomy and physician’s expertise

    • Verification of the setting, including preparation of the catheter table that should include insertion sheath, anesthetic, and pulmonary arterial catheter

  • Installation

    • Ensure a quiet environment.

    • Place the patient in supine position, and monitor electrocardiogram (ECG), noninvasive blood pressure, and oxygen saturation.

    • Insert a peripheral catheter in case of anxiety/agitation to deliver myorelaxant (midazolam).

    • Deliver supplemental oxygen, if required, to aim for an arterial oxygen saturation (Sa02) >90%.

  • Vascular approach—internal jugular vein

    • Most common and easiest approach, preferable in the ICU setting

    • Low rate of complications (0.3% in PH evaluation [4]).

    • Prefer the right side for a more straightforward approach.

    • Ensure sufficient filling by slightly tilting the patient at −20°, or use ultrasonography to guide insertion.

    • Local anesthesia at the level of the clavicle part of the sternocleidomastoid muscle.

    • Puncture of the internal jugular vein, approximately three fingers above the clavicle.

    • Insertion of a guide wire, followed by a 7-F size sheath introducer.

    • Consider antecubital or subclavian approach only if the jugular vein is not accessible.

    • Femoral approach preferred in the cath lab, especially in associated left-heart procedures: However, the increasing use of the radial approach for the latter makes this less necessary.

  • Positioning of the catheter (Fig. 6.1)

    • Either under fluoroscopic guidance or by following the pressure traces on the monitoring.

    • Inflation of the balloon in the right atrium (roughly when the catheter is inserted by 20–30 cm) with evidence of RAP tracing.

    • Further progression through the tricuspid valve in the right ventricle (a rise in systolic pressure is observed), the right ventricular outflow tract, and the main trunk of the pulmonary artery (a rise in diastolic pressure is observed).

    • Pressure decay observed in the wedge position, requiring deflation of the balloon.

    • Caveats: Inflate balloon when respiratory pressure swings; a.lways deflate balloon when pulling back; avoid repeated deflations and inflations of the balloon in the end pulmonary arteries because of the risk of rupture of the pulmonary arteries

Fig. 6.1
figure 1

Pressure traces collected during routine RHC. The pulmonary artery catheter is progressively advanced in the heart chambers, with the corresponding pressures. (1) Right atrial pressure (RAP); (2) right ventricular pressure (RVP); (3) pulmonary artery pressure (PAP); 4: pulmonary artery wedge pressure (PAWP)

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Data Acquisition and Analysis, Measurements, and Derived Calculations

During RHC, pressures are measured with fluid-filled catheters such as a pressure difference between hydrostatic pressures at a chosen zero level and pressures in the chamber or vessel where the catheter lumen is open.

The following protocol should be followed for an optimal pressure measurement:

  • Zeroing and respiratory cycle

    • Zero leveling of the external pressure transducer: mid-chest (half distance between the anterior sternum and the bed surface, corresponding to the left atrial level) or 5 cm below angle of Louis in a supine patient.

    • Pressure measurements at normal end expiration—or average over several respiratory cycles if marked respiratory pressure swings (in obese patients and patients with lung disease): Mean of three measurements of each pressure at end expiration.

  • Data acquisition

    • Pressures

      The following pressures must be recorded: central venous pressure (CVP), RAP equal to right ventricular end-diastolic pressure, right ventricular pressure (RVP) (systolic, diastolic, mean), pulmonary artery pressure (PAP) (systolic, diastolic, mean), PAWP—a surrogate of left atrial pressure.

      Ideally, pressure should be read on paper traces at a speed of 12.5–25 mm/s for quality control. Scale must be adapted to position the pressure traces in the upper 1/3rd of the paper. Readings can also be made from screenshots if the system allows for a cursor placement in a proper position. Direct display of measures should be avoided as they may be influenced by the respiratory cycle and arrhythmias.

    • Cardiac output

      Several methods have been used to measure cardiac output (CO). The Fick method is considered the gold standard, by using the following: CO = VO2/CaO2 ‑CvO2, where VO2 = oxygen consumption, CaO2 = oxygen concentration of arterial blood, and CvO2 = oxygen concentration of mixed venous blood. To be accurate, VO2 should be measured directly. The estimated value can lead to considerable errors.

      The method of choice is therefore the thermodilution technique, where cardiac output is assessed after injecting 10 mL cold or room-temperature saline. CO should be determined in triplicate with less than 10% variation.

    • Blood gas analysis

      In all patients, analysis of arterial (by direct arterial puncture) and mixed venous blood (by sampling blood from the tip lumen of the RHC) gases must be performed. Stepwise assessment of oxygen saturation by blood samples taken from the superior and inferior vena cava, right atrium, and pulmonary artery is needed in every patient with a pulmonary arterial oxygen saturation (mixed venous blood saturation, SvO2) >75% and in case of suspicion of a left-to-right shunt.

    • Other data acquisition

      Because patients are continuously monitored, the following must be recorded: systemic arterial pressure (SAP) estimated by noninvasive blood pressure if left-heart cath is not performed at the same time, HR, and pulse oxygen saturation (SpO2).

    • Pitfalls

      As for any technique, RHC should be meticulously performed to avoid mistakes (Table 6.3 and Fig. 6.2).

  • Calculations and RHC report (Fig. 6.3)

Table 6.3 Pitfalls and errors in RHC (adapted from references [1, 2, 15, 16])
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Fig. 6.2
figure 2

Effect of inappropriate balloon inflation and respiratory swings on pulmonary artery wedge pressure (PAWP) reading. The pressure traces displayed in this figure were recorded in the same patient during a single RHC. The dotted line represents the placement of the cursor for meticulous measurement of PAWP. Panel A: The balloon is underinflated, leading to insufficient damping of the pressure and partial occlusion; PAWP is inappropriately measured at 18 mmHg. Panel B: The balloon is fully inflated, with a good pressure decay allowing for a correct measurement of PAWP at 7 mmHg. Panel C: The balloon is correctly inflated, but excessive respiratory swings are present, leading to an incorrect end-expiratory PAWP measurement >40 mmHg

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Fig. 6.3
figure 3

Comprehensive RHC hemodynamic report

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Once data are acquired, a full hemodynamic report must be generated. It must contain the following values and an interpretation of the findings:

  • Pulmonary vascular resistance (PVR) = (mPAP ‑ PAWP)/CO.

  • Transpulmonary pressure gradient (TPG) = mPAP – PAWP.

  • Diastolic transpulmonary gradient (DPG) = dPAP ‑ PAWP (less affected by flow and filling pressures [5] but may not be of prognostic value [6]).

  • SVR = (SAP-RAP)/CO.

  • CI = CO/BSA, cardiac index (CI) corresponding to cardiac output (CO) adjusted for body surface area (BSA).

  • RVSW = (mPAP-RAP) × SV (stroke volume), right ventricular stroke work.

  • Other calculations may be provided (such as pulmonary arterial compliance), but their clinical relevance remains unknown.

  • PAWP or LVEDP ?

    LV end-diastolic pressure (LVEDP) measurement is needed when PAWP is unexpectedly elevated and/or inaccurate (absence of risk factors for heart failure with preserved ejection fraction (HFpEF), normal left atrial size, and absence of echocardiographic markers of elevated left ventricular filling pressures) [2].

  • Normal values for hemodynamic measurements and calculations are displayed in Table 6.4.

Table 6.4 Normal values of variables collected during RHC (after references [2, 8])
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Complications Related to the Use of Pulmonary Artery Catheter

Adverse events related to RHC are rare. A large multicenter registry reported the outcome of patients undergoing RHC for the assessment of PH over a 5-year retrospective and 6-month prospective evaluation [4]. Mortality and morbidity rates were found relatively low (respectively, 0.055% and 1.1%) [4]. In most cases, complications are mild to moderate in intensity and resolve either spontaneously or after appropriate intervention.

  • Major risk, associated with death, longer hospitalization, or requiring intervention:

    • Carotid artery puncture, arterial bleeding (with internal jugular vein approach)

    • Pneumothorax, hemothorax (subclavian or internal jugular vein approach)

    • Retroperitoneal hemorrhage (femoral approach)

    • Air emboli through introducers

    • Rupture of pulmonary artery

    • Tamponade

    • Lung infarction/hemoptysis

    • Arrhythmia, either atrial or ventricular

    • Transient right bundle branch block (5%), or complete heart block in patients with preexisting left bundle branch block

    • Tricuspid valve injury

  • Mild-to-moderate risk, with usually no intervention and full recovery

    • Hematoma at the site of puncture

    • Transient hypotension due to vasovagal reaction

    • Catheter knotting in intracardiac chambers

    • Misplacement due to looping of the catheter inside the right atrium of the right ventricle (fluoroscopy guidance in case of doubt)

    • Infections are exceptional when the catheter is left in place <24 h (for monitoring purposes)

Most of, if not all, these risks can easily be avoided by following some “golden” rules:

  • Use anatomical landmarks when inserting the introducer; if puncture is difficult, use Doppler-echo guidance.

  • Advance the catheter under pressure monitoring and fluoroscopic guidance.

  • Do not push the catheter too far (>50–55 cm from insertion, >15 cm from RVP to PAP).

  • Avoid pushing/withdrawing the catheter in case of resistance.

  • Always deflate the balloon prior to catheter withdrawal and never remove the catheter when the balloon is inflated.

  • Never remove the catheter in case of hemoptysis: reinflate or leave the catheter in place and perform an angiogram.

Interpretation of Results: Pulmonary Hypertension

  • Pulmonary hypertension is the most common indication for RHC. It is defined by a mean pulmonary arterial pressure (mPAP) ≥25 mmHg at rest, measured invasively [1, 2]. The clinical classification of PH identifies five groups, each sharing similar clinical, pathobiological, and outcome characteristics (Table 6.5). With roughly 80% of all causes of PH, left-heart diseases (group 2) and pulmonary disorders (group 3) represent the most common etiologies.

  • In normal individuals, the upper limit of mPAP is approximately 20 mmHg [1, 7, 8]. Although the relevance of an mPAP between 21 and 24 mmHg is unclear, it may require careful follow-up in patients at risk of PAH [7]. There is currently no approved hemodynamic definition for “PH on exercise.”

  • The hemodynamic definition of PH is based on the measurement of mPAP and PAWP and the calculation of PVR (Table 6.6).

    • Precapillary PH is defined by an mPAP ≥25 mmHg, a PAWP ≤15 mmHg, and a PVR >3 Wood units (WU).

    • Postcapillary PH is defined by an mPAP ≥25 mmHg and a PAWP >15 mmHg and may correspond to PH due to left-heart failure or with unclear and/or multifactorial mechanisms [1, 2].

    • Postcapillary PH is further subdivided according to the diastolic pressure gradient (DPG = dPAP-PAWP) to distinguish isolated postcapillary PH (IPC-PH), if the DPG <7 mmHg and/or PVR ≤3 WU, from combined postcapillary PH (CPC-PH), if the DPG ≥7 mmHg and/or PVR >3 WU.

  • Patient with PH due to HFpEF may present with normalized PAWP when treated aggressively with diuretics. In addition, patients with PAH tend to present with cardiovascular comorbidities that overlap with HFpEF. Therefore, the distinction between the two conditions has major implications as PAH therapies are not approved in group 2 PH. Unmasking diastolic dysfunction is therefore critical in the assessment of patients at risk of PH due to HFpEF. An adequate measurement of PAWP is thus critical and provocative tests performed during RHC may play a role in the differential diagnosis (see below).

  • RHC also plays an important role in the treatment decision for PAH, currently based on a risk-oriented strategy, which includes an invasive component. A worse prognosis is associated with a RAP >12 mmHg, a SvO2 <60%, and a CI <2 L/min/m2.

Table 6.5 Clinical classification of pulmonary hypertension [2]
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Table 6.6 Hemodynamic definition of pulmonary hypertension [1]
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Provocative Pulmonary Vasoreactivity/Dynamic Testing During Right Heart Catheterization

The role of provocative testing of the pulmonary circulation has been extensively reported. However, most procedures lack standardization, definition of normal response, and validation through multicenter studies. In addition, the impact of these tests on a decision-making process and patient’s outcome is frequently unclear. Despite these limitations, the following tests are/can be used in clinical practice.

  • Pulmonary vasoreactivity testing

    RHC is part of the assessment for heart transplantation and LVAD implantation. In this setting, PH is associated with a dismal outcome, although it is not clear whether it is due to PH alone or right ventricular dysfunction found in end-stage HF. Although various vasodilators have been used (mostly in single-center studies), nitroprusside, milrinone, and enoximone are the most appropriate compounds as they act primarily by decreasing left-side filling pressures (nitroprusside) and/or by increasing CO (milrinone, enoximone). Epoprostenol and nitric oxide should be avoided as they may further increase PAWP. Finally, there is limited evidence for the use of PDE-5 inhibitors in this context. It is generally accepted that a decrease in PVR <4–5 WU, and/or a TPG <15 mmHg with a maintained systemic pressure, would qualify a patient for surgery.

    In PAH, the purpose of vasoreactivity testing is to identify calcium-channel blocker (CCB) “responders” in patients with idiopathic PAH. An acute response is defined as a decrease in mPAP below 40 mmHg and by >10 mmHg, with no change or increase in CO. Only responders can benefit from CCB therapy. Inhaled nitric oxide (10–20 parts per million) is the agent of choice as it has a short half-life and no systemic effects. Alternatively, intravenous (IV) epoprostenol (2–12 ng/kg/min) may be considered but is associated with systemic side effects (flushing, headache, nausea, hypotension). The use of other vasodilators such as nitrates, PDE-5 inhibitors, IV CCB, or iloprost should be discouraged.

  • Fluid loading test for unmasking left ventricular diastolic dysfunction

    PAWP may be reduced to <15 mmHg with diuretics in many patients with left-heart disease. In this context, the effect of an acute fluid challenge on left-heart filling pressures evaluated during RHC may help to differentiate the diagnosis between pre- and postcapillary PH [7, 9, 10]. Limited data suggest that a fluid bolus of 500 mL saline in 5–10 min is safe and may discriminate patients with precapillary PH from those with occult left ventricular diastolic dysfunction [5]. Recent studies suggest that a PAWP above 18 mmHg may be considered as an abnormal response to fluid challenge [9, 11].

  • Exercise testing to unmask left ventricular diastolic dysfunction

    Compared with fluid loading, hemodynamic measurements during exercise offer a more physiological approach to uncover left ventricular diastolic dysfunction [12,13,14]. The test is commonly performed in the supine position with a pedaling system attached to the catheterization table. Ideally, PAP and CO should be measured repeatedly at several levels of exercise to generate multipoint mPAP/CO relationship [8]. This approach avoids the wide individual variation of pressure and flow at a given level of workload. In healthy controls, the slope of this relationship (i.e., dynamic PVR) is between 1 and 2 WU. However, wide swings in airway and pleural pressures with exercise are associated with potential technical errors, even at low level of exercise.

    Therefore, both invasive exercise testing and fluid loading require standardization and further evaluation before being recommended in routine clinical practice.