# Right Heart Catheterization: A Comprehensive Guide to Hemodynamic Interpretation and Diagnosis

[RHC Comprehensive Guide](https://urinenephrology.org/mastery/rhc/index.html) [Restrictive vs Constrictive](https://urinenephrology.org/mastery/rhc/restrictive-vs-constrictive.html) [ATTR Cardiac Amyloidosis](https://urinenephrology.org/mastery/rhc/cardiac-amyloidosis.html)

## Quick Navigation

[1. Executive Summary](https://urinenephrology.org/mastery/rhc/index.html#executive-summary) [2. Introduction](https://urinenephrology.org/mastery/rhc/index.html#introduction) [3. Normal Values](https://urinenephrology.org/mastery/rhc/index.html#normal-values) [4. Systematic Approach](https://urinenephrology.org/mastery/rhc/index.html#systematic-approach) [5. Pulmonary Hypertension](https://urinenephrology.org/mastery/rhc/index.html#pulmonary-hypertension) [6. Heart Failure Profiles](https://urinenephrology.org/mastery/rhc/index.html#heart-failure) [7. Cardiogenic Shock](https://urinenephrology.org/mastery/rhc/index.html#cardiogenic-shock) [8. Valvular Disease](https://urinenephrology.org/mastery/rhc/index.html#valvular) [9. Restrictive vs Constrictive](https://urinenephrology.org/mastery/rhc/index.html#restrictive-vs-constrictive) [10. Intracardiac Shunts](https://urinenephrology.org/mastery/rhc/index.html#shunts) [11. Waveform Analysis](https://urinenephrology.org/mastery/rhc/index.html#waveforms) [12. Provocative Testing](https://urinenephrology.org/mastery/rhc/index.html#provocative) [13. Nephrology Considerations](https://urinenephrology.org/mastery/rhc/index.html#nephrology) [14. Illustrative Case](https://urinenephrology.org/mastery/rhc/index.html#illustrative-case) [15. References](https://urinenephrology.org/mastery/rhc/index.html#references)

## Executive Summary

**Key Points**

- Right heart catheterization (RHC) is the gold standard for invasive hemodynamic assessment and is required for definitive diagnosis and classification of pulmonary hypertension, hemodynamic characterization of heart failure, differentiation of restrictive cardiomyopathy from constrictive pericarditis, evaluation of valvular heart disease, detection of intracardiac shunts, and assessment of cardiogenic vs. distributive shock (1,2,3)
- The 2022 ESC/ERS guidelines redefined pulmonary hypertension as mPAP \> 20 mmHg (lowered from ≥ 25 mmHg) and pre-capillary PH as PVR \> 2 Wood units (lowered from ≥ 3 WU), capturing patients earlier in the disease course (3,4)
- Systematic interpretation requires sequential assessment: filling pressures → cardiac output → mixed venous saturation → pulmonary hypertension classification → derived parameters → waveform analysis → provocative testing when indicated (1,2)
- The pulmonary capillary wedge pressure (PCWP) is the single most consequential measurement in RHC interpretation; its accuracy determines whether PH is classified as pre-capillary (Group 1/3/4/5) or post-capillary (Group 2), which dictates fundamentally different treatment strategies (2,3,4)
- Preserved ejection fraction on echocardiography can mask critically reduced cardiac output in infiltrative cardiomyopathies; literature documents a median 13-month diagnostic delay, 44% misdiagnosis rate, and 3- to 5-fold mortality increase in cardiac amyloidosis driven by this cognitive trap (5,6,7,8)
- For the nephrologist, RHC data provide the physiologic explanation for diuretic resistance (elevated RA pressure → renal venous congestion; low CI → impaired renal perfusion) and guide the decision between escalating diuretics, adding inotropes, or pursuing mechanical support (9)

## 1. Introduction: The Indispensable Role of Right Heart Catheterization

Right heart catheterization provides direct measurement of intracardiac pressures, cardiac output, and vascular resistances that cannot be reliably obtained by any noninvasive modality. While echocardiography, cardiac MRI, and CT provide invaluable structural and functional information, they estimate hemodynamics through indirect calculations and assumptions that may fail in precisely the patients who need hemodynamic data most — those with discordant clinical and imaging findings (1,2).

The procedure involves percutaneous insertion of a balloon-tipped, flow-directed catheter (Swan-Ganz catheter) through a central vein, advanced sequentially through the right atrium, right ventricle, and pulmonary artery, with final balloon inflation to obtain the pulmonary capillary wedge pressure. The entire hemodynamic circuit from venous return to left atrial pressure surrogate is assessed in a single procedure that carries remarkably low morbidity (1.1%) and mortality (0.055%) (2).

RHC is required — not optional — for the definitive diagnosis of pulmonary hypertension, the hemodynamic classification that determines treatment strategy, the assessment of transplant candidacy, and the differentiation of restrictive from constrictive physiology when noninvasive testing is inconclusive (1,2,3).

## 2. Normal Hemodynamic Values and Measured Parameters

Before interpreting abnormal hemodynamics, the clinician must have a firm command of normal values. The following reference ranges represent resting hemodynamics in the supine position (1):

| Parameter                                        | Normal Range | Unit       |
|--------------------------------------------------|--------------|------------|
| Right atrial pressure (mean RA)                  | 0–8          | mmHg       |
| Right ventricular systolic pressure (RVSP)       | 15–30        | mmHg       |
| Right ventricular end-diastolic pressure (RVEDP) | 0–8          | mmHg       |
| Pulmonary artery systolic pressure (PASP)        | 15–30        | mmHg       |
| Pulmonary artery diastolic pressure (PADP)       | 4–12         | mmHg       |
| Mean pulmonary artery pressure (mPAP)            | 10–20        | mmHg       |
| Pulmonary capillary wedge pressure (PCWP)        | 4–12         | mmHg       |
| Cardiac output (CO)                              | 4.0–8.0      | L/min      |
| Cardiac index (CI)                               | 2.5–4.0      | L/min/m²   |
| Pulmonary vascular resistance (PVR)              | 0.25–1.6     | Wood units |
| Systemic vascular resistance (SVR)               | 10–20        | Wood units |
| Mixed venous oxygen saturation (SvO₂)            | 65–75        | %          |
| Pulmonary arterial compliance (PAC)              | \> 2.3       | mL/mmHg    |

### 2.1 Key Derived Parameters

**Mean pulmonary artery pressure (mPAP):** Calculated as (systolic + 2 × diastolic) / 3. This is the defining measurement for pulmonary hypertension. The 2022 ESC/ERS threshold is \> 20 mmHg (lowered from the prior ≥ 25 mmHg) (3,4).

**Transpulmonary gradient (TPG):** mPAP − PCWP. Normal \< 12 mmHg. Reflects the total pressure drop across the pulmonary vascular bed. An elevated TPG in the setting of elevated PCWP suggests a pre-capillary component superimposed on left heart disease.

**Diastolic pulmonary gradient (DPG):** PA diastolic − PCWP. Normal \< 7 mmHg. The DPG is a more specific marker of pulmonary vascular remodeling than the TPG because it is less affected by cardiac output and flow. An elevated DPG (≥ 7 mmHg) in the setting of elevated PCWP defines combined pre- and post-capillary pulmonary hypertension (Cpc-PH) (3,4).

**Pulmonary vascular resistance (PVR):** (mPAP − PCWP) / CO, expressed in Wood units (WU). Pre-capillary PH is now defined as PVR \> 2 WU (previously ≥ 3 WU) (3,4).

**Pulmonary arterial compliance (PAC):** Stroke volume / (PASP − PADP). Reduced PAC (\< 2.3 mL/mmHg) is an independent predictor of mortality in PH (3).

**Fick cardiac output:** CO = VO₂ / (CaO₂ − CvO₂) × 10. When thermodilution is unreliable (severe tricuspid regurgitation, low-output states, intracardiac shunts), the Fick method is preferred (1,2).

**RVEDP/RVSP ratio:** Used in differentiating constriction from restriction. A ratio \> 1/3 (0.33) has traditionally been cited as favoring constriction, though significant overlap exists (10,11).

## 3. Systematic Approach to RHC Interpretation

A structured interpretation proceeds through the following steps for every catheterization:

**Step 1: Record and verify all measured pressures.** Ensure the transducer is zeroed at the phlebostatic axis (mid-axillary line, fourth intercostal space). Read all pressures at end-expiration to minimize respiratory artifact (1,2).

**Step 2: Assess right-sided filling pressures.** RA \> 8 mmHg and/or RVEDP \> 8 mmHg indicate right heart congestion — from RV failure, volume overload, pericardial constraint, or tricuspid valve disease.

**Step 3: Assess left-sided filling pressures.** PCWP \> 15 mmHg (2022 threshold) indicates elevated left atrial pressure from LV diastolic dysfunction, mitral valve disease, or volume overload. This single measurement determines the pre-capillary vs. post-capillary PH classification (3,4).

**Step 4: Evaluate cardiac output and cardiac index.** CI 2.2–4.0 L/min/m² is normal. CI \< 2.2 indicates hemodynamic compromise. CI \< 1.8 is consistent with cardiogenic shock. CI \< 1.5 is critical and associated with end-organ hypoperfusion (1).

**Step 5: Assess the mixed venous oxygen saturation (SvO₂).** Measured in the pulmonary artery. SvO₂ \< 65% indicates increased systemic extraction compensating for reduced delivery. SvO₂ \< 60% is associated with tissue-level oxygen debt. SvO₂ \< 50% is critical. A notable exception: elevated SvO₂ with a step-up from RA to PA suggests a left-to-right intracardiac shunt (1).

**Step 6: Classify pulmonary hypertension** if mPAP \> 20 mmHg (see Section 4).

**Step 7: Calculate derived parameters** (TPG, DPG, PVR, PAC) and integrate with the clinical context.

**Step 8: Analyze waveforms** for specific diagnoses (see Section 10).

**Step 9: Pursue provocative testing** if resting hemodynamics are borderline or non-diagnostic (see Section 11).

## 4. Pulmonary Hypertension: Hemodynamic Classification and Diagnosis

### 4.1 Updated Hemodynamic Definitions (2022 ESC/ERS)

| Classification | mPAP | PCWP | PVR | Clinical Implication |
|----|----|----|----|----|
| No PH | ≤ 20 mmHg | — | — | Normal pulmonary pressures |
| Pre-capillary PH | \> 20 mmHg | ≤ 15 mmHg | \> 2 WU | Pulmonary vascular disease (Group 1, 3, 4, 5) |
| Isolated post-capillary PH (IpcPH) | \> 20 mmHg | \> 15 mmHg | ≤ 2 WU | Passive congestion from left heart disease (Group 2) |
| Combined pre/post-capillary PH (CpcPH) | \> 20 mmHg | \> 15 mmHg | \> 2 WU | Left heart disease PLUS pulmonary vascular remodeling (Group 2) |
| Exercise PH | — | — | — | mPAP/CO slope \> 3 mmHg/L/min from rest to exercise |

**Warning:** The 2022 definitions lowered the mPAP threshold from ≥ 25 to \> 20 mmHg and the PVR threshold from ≥ 3 to \> 2 WU. While these changes capture patients earlier, no evidence-based treatments currently exist for patients with mPAP 21–24 mmHg or PVR 2–3 WU. The clinical significance of this "borderline" population remains under investigation (3,4).

### 4.2 The Five WHO Clinical Groups of Pulmonary Hypertension

**Group 1 — Pulmonary Arterial Hypertension (PAH):** Pre-capillary PH with no identifiable left heart, lung, or thromboembolic cause. Includes idiopathic, heritable, drug-induced, and associated forms (connective tissue disease, HIV, portal hypertension, congenital heart disease). Vasoreactivity testing with inhaled nitric oxide is performed to identify the ~10% who respond to calcium channel blockers. A positive response: fall in mPAP ≥ 10 mmHg to an absolute value ≤ 40 mmHg with stable or increased cardiac output (3).

**Group 2 — PH Due to Left Heart Disease:** Post-capillary PH (PCWP \> 15 mmHg). The most common cause of PH overall. Subclassified into IpcPH (PVR ≤ 2 WU) and CpcPH (PVR \> 2 WU). PAH-specific vasodilator therapy is NOT indicated in Group 2 PH (3,4).

**Group 3 — PH Due to Lung Disease or Hypoxia:** Pre-capillary PH in COPD, ILD, sleep-disordered breathing, or chronic high-altitude exposure. Severe PH (mPAP ≥ 35 mmHg or mPAP ≥ 25 with CI \< 2.0) in mild-moderate lung disease suggests coexisting pulmonary vascular disease (3).

**Group 4 — Chronic Thromboembolic PH (CTEPH):** Potentially curable with pulmonary endarterectomy (PEA). All patients with unexplained pre-capillary PH should be evaluated with V/Q scanning (3).

**Group 5 — PH with Unclear or Multifactorial Mechanisms:** Includes hematologic, systemic, metabolic disorders, chronic renal failure, and fibrosing mediastinitis (3).

**Clinical Pearl:** The most consequential diagnostic error in PH management is misclassifying Group 2 PH (left heart disease) as Group 1 PAH and initiating PAH-specific vasodilator therapy. When clinical suspicion for left heart disease is high but resting PCWP is ≤ 15 mmHg, provocative testing with saline challenge (500 mL rapid infusion) or exercise hemodynamics should be performed before concluding that PH is pre-capillary (2,3,4).

### 4.3 Vasoreactivity Testing

Performed during RHC in patients with suspected PAH (Group 1). The standard agent is inhaled nitric oxide (10–20 ppm for 5 minutes). **Positive response:** Fall in mPAP ≥ 10 mmHg to an absolute mPAP ≤ 40 mmHg, with maintained or increased cardiac output. Only ~10% of idiopathic PAH patients are vasoreactive (3).

## 5. Heart Failure: Hemodynamic Profiles and Treatment Implications

### 5.1 The Forrester Classification (Hemodynamic Subsets)

| Profile | PCWP | CI | Clinical State | Treatment Priority |
|----|----|----|----|----|
| **Profile A** ("Warm and Dry") | ≤ 18 | ≥ 2.2 | Compensated | Optimize oral therapy |
| **Profile B** ("Warm and Wet") | \> 18 | ≥ 2.2 | Congested, adequate perfusion | Diuretics (IV loop ± thiazide) |
| **Profile C** ("Cold and Wet") | \> 18 | \< 2.2 | Congested AND hypoperfused | Diuretics + inotropes; consider MCS |
| **Profile L** ("Cold and Dry") | ≤ 18 | \< 2.2 | Hypoperfused, not congested | Cautious volume challenge; inotropes if no response |

**Clinical Pearl:** Profile C ("cold and wet") carries the worst prognosis and requires simultaneous decongestion and hemodynamic support. The choice between inotropes (dobutamine, milrinone) and mechanical circulatory support (Impella, ECMO) depends on severity of shock, end-organ function, and candidacy for recovery, transplant, or destination therapy (1).

### 5.2 HFrEF vs. HFpEF Hemodynamic Profiles

| Parameter | HFrEF (EF \< 40%) | HFpEF (EF ≥ 50%) | Key Distinction |
|----|----|----|----|
| PCWP | Elevated (\> 15) | Elevated (\> 15) | Similar |
| CI | Reduced (often \< 2.0) | Mildly reduced to low-normal | HFpEF CI typically 2.0–2.5 |
| EF–CO relationship | Low EF, low CO → concordant | Preserved EF, may have low CO → discordant | The discordance in HFpEF is the diagnostic trap |
| RA pressure | Elevated in decompensation | May be profoundly elevated | Especially in infiltrative causes |

### 5.3 The Preserved EF Trap: Literature-Validated Diagnostic Failure

The echocardiographic ejection fraction is fundamentally unreliable as a measure of cardiac performance in infiltrative cardiomyopathies. The 2020 AHA Scientific Statement on cardiac amyloidosis (Kittleson et al.) explicitly identifies the attribution of signs and symptoms to generic "HFpEF" as a primary driver of diagnostic failure in ATTR-CM (5).

Preserved ejection fraction does not exclude cardiac amyloidosis. In a 50-patient ATTRwt cohort, Ladefoged et al. found a median diagnostic delay of 13 months; that estimate is specific to the cohort. Use clinical red flags and a structured evaluation rather than a generic HFpEF label. [Diagnostic-delay study](https://pubmed.ncbi.nlm.nih.gov/32033783/); [ACC consensus](https://pubmed.ncbi.nlm.nih.gov/36697326/)

**Warning: The Preserved EF Trap.** In any patient with HFpEF — particularly elderly males over 65 with unexplained LV hypertrophy, disproportionate symptoms, or diuretic resistance — the EF must not be used to exclude significant cardiac disease. The question is not "what is the EF?" but "what is the cardiac output, and why is the patient this sick?" Global longitudinal strain (GLS) with apical sparing is a more sensitive echocardiographic marker of amyloid infiltration than EF. When the clinical picture is worse than the echo suggests, pursue invasive hemodynamic assessment (5,6,7,8).

## 6. Cardiogenic Shock: Hemodynamic Diagnosis and Phenotyping

Cardiogenic shock is hemodynamically defined by a CI \< 1.8 L/min/m² (or \< 2.2 with vasopressor support), a PCWP \> 15 mmHg, and evidence of end-organ hypoperfusion (1).

### 6.1 Hemodynamic Profiles in Shock

| Parameter | Cardiogenic | Distributive (Septic) | Hypovolemic | Obstructive |
|----|----|----|----|----|
| RA | Elevated (\> 15) | Low-normal (\< 8) | Low (\< 5) | Elevated (\> 15) |
| PCWP | Elevated (\> 18) | Low-normal (\< 12) | Low (\< 8) | Variable |
| CI | Severely reduced (\< 1.8) | Elevated (\> 4.0) | Reduced | Reduced |
| SVR | Elevated (\> 20 WU) | Low (\< 10 WU) | Elevated | Elevated |
| SvO₂ | Low (\< 60%) | High (\> 75%) | Low (\< 60%) | Low (\< 60%) |

**Clinical Pearl:** Mixed shock (cardiogenic + distributive) is common. The RHC reveals elevated filling pressures (cardiogenic component) with inappropriately low SVR (distributive component), requiring simultaneous inotropic support and vasopressor therapy (1).

### 6.2 RV Failure vs. LV Failure in Shock

| Feature | LV-Predominant | RV-Predominant | Biventricular |
|----|----|----|----|
| RA | Moderately elevated | Severely elevated (often \> 18) | Severely elevated |
| PCWP | Severely elevated (\> 22) | Normal to mildly elevated | Elevated |
| RA/PCWP ratio | \< 0.6 | \> 0.8 | ~ 0.7–1.0 |
| Treatment focus | LV unloading (Impella, IABP) | RV support; avoid excessive preload reduction | Biventricular support (BiVAD, ECMO) |

## 7. Valvular Heart Disease: Hemodynamic Assessment

### 7.1 Mitral Stenosis

Hallmark: elevated transmitral gradient between PCWP (LA surrogate) and LVEDP. Prominent "a" waves and slow "y" descent on PCWP tracing. Mitral valve area can be calculated using the Gorlin formula (1).

### 7.2 Mitral Regurgitation

Acute severe MR produces large "v" waves on the PCWP tracing (may exceed 40–50 mmHg). Chronic MR with a dilated, compliant LA may have attenuated "v" waves. Thermodilution measures forward + regurgitant flow; the effective forward CO is reduced (1).

**Clinical Pearl:** Not all large "v" waves indicate mitral regurgitation. A stiff, noncompliant left atrium (as in restrictive cardiomyopathy or post-ablation atrial scarring) can produce prominent "v" waves from normal atrial filling into a noncompliant chamber. Correlate with echocardiographic assessment (1).

### 7.3 Aortic Stenosis

Elevated PCWP (from LV diastolic dysfunction). In low-flow, low-gradient AS, dobutamine stress differentiates true severe AS from pseudo-severe AS. Up to 16% of elderly patients with degenerative AS have coexisting ATTR amyloidosis (5).

### 7.4 Tricuspid Regurgitation

Severe TR renders thermodilution CO unreliable — use Fick method. RA waveform shows prominent "cv" wave with rapid "y" descent (1).

## 8. Restrictive Cardiomyopathy vs. Constrictive Pericarditis

For a detailed discussion, see the dedicated [Restrictive vs. Constrictive Review](https://urinenephrology.org/mastery/rhc/restrictive-vs-constrictive.html).

### 8.1 The Fundamental Pathophysiologic Distinction

**In constrictive pericarditis:** The rigid pericardium creates **exaggerated ventricular interdependence** and **dissociation between intrathoracic and intracardiac pressures**. Both ventricles are equally constrained, so filling pressures tend to equalize (10,11,12).

**In restrictive cardiomyopathy:** The myocardium itself is stiff from infiltration. Each ventricle is independently stiff. Ventricular interdependence is *normal*. Left-sided filling pressures typically exceed right-sided pressures (10,11,12).

### 8.2 Hemodynamic Criteria for Differentiation

| Criterion | Favors Constriction | Favors Restriction |
|----|----|----|
| LVEDP − RVEDP | ≤ 5 mmHg (equalized) | \> 5 mmHg (LVEDP exceeds RVEDP) |
| RVEDP/RVSP ratio | \> 1/3 (\> 0.33) | \< 1/3 (\< 0.33)\* |
| RV systolic pressure | ≤ 50 mmHg (usually ≤ 40) | \> 50 mmHg |
| Dip-and-plateau ("square root sign") | Present | Present (NOT discriminating) |
| Respirophasic ventricular interdependence | **Discordant** (RV↑, LV↓ with inspiration) | **Concordant** (RV and LV move together) |
| Kussmaul sign | Often present | May be present (less specific) |

\*In advanced biventricular restrictive disease, RVEDP may rise such that the ratio exceeds 1/3 despite clearly restrictive physiology.

**Warning: Common Misconception.** Pressure equalization (RVEDP ≈ LVEDP within 5 mmHg) is a feature of *constrictive pericarditis*, not restrictive cardiomyopathy. In restriction, filling pressures are typically *unequal*, with LVEDP exceeding RVEDP. However, in advanced biventricular infiltrative disease (severe ATTR amyloidosis), the gradient may narrow (10,11,12).

### 8.5 Comprehensive Hemodynamic Comparison

| Parameter | Restrictive CM | Constrictive Pericarditis | Severe HFpEF | Cardiac Tamponade |
|----|----|----|----|----|
| RA pressure | Elevated (15–25+) | Elevated (15–25+) | Mildly elevated (10–18) | Elevated, equals PCWP |
| PCWP | Elevated (\> RVEDP) | Elevated (≈ RVEDP) | Elevated | Elevated (≈ RA) |
| Cardiac output | Reduced to severely reduced | Reduced | Mildly-mod reduced | Reduced |
| EF | Preserved (50–65%) | Preserved | Preserved (≥ 50%) | Reduced in severe |
| Ventricular interdependence | Concordant | Discordant | Not significant | Enhanced |
| Key feature | EF–CO dissociation; thick walls | Pericardial thickening; septal bounce | HTN, DM, age | Large effusion; pulsus paradoxus |

## 9. Intracardiac Shunts: Oximetric Diagnosis

### 9.1 The Oximetric Run

Measures oxygen saturation at sequential locations through the right heart. A "step-up" at a specific level indicates left-to-right shunting at that location (1).

| Step-Up Location | Shunt Location | Common Causes |
|----|----|----|
| SVC to RA (\> 7% step-up) | Atrial level | ASD, anomalous pulmonary venous return |
| RA to RV (\> 5% step-up) | Ventricular level | VSD |
| RV to PA (\> 5% step-up) | Great vessel level | PDA, aortopulmonary window |

### 9.2 Shunt Quantification (Qp/Qs Ratio)

**Qp/Qs = (SaO₂ − SvO₂) / (PvO₂ − PaO₂)**

A Qp/Qs \> 1.5 indicates a hemodynamically significant left-to-right shunt. Qp/Qs \> 2.0 represents a large shunt. In Eisenmenger physiology (right-to-left shunting with cyanosis), the Qp/Qs is \< 1.0 (1).

**Clinical Pearl:** When evaluating a patient with unexplained pulmonary hypertension and an unexpected step-up on the oximetric run, consider undiagnosed ASD or partial anomalous pulmonary venous return. These are surgically or percutaneously correctable causes of PAH (1,3).

## 10. Waveform Analysis: Pattern Recognition for Specific Diagnoses

### 10.1 RA Waveform Components

**"a" wave:** Atrial contraction. Absent in atrial fibrillation. Giant "a" waves occur when the atrium contracts against a closed or stenotic tricuspid valve.

**"c" wave:** Tricuspid valve closure. Small, often not visible.

**"x" descent:** Atrial relaxation during ventricular systole. Attenuated or absent in severe TR.

**"v" wave:** Passive atrial filling during ventricular systole. Giant "v" waves occur in severe TR.

**"y" descent:** Rapid atrial emptying after tricuspid valve opens. Diagnostically important.

### 10.2 Diagnostic Waveform Patterns

| Waveform Pattern | Diagnosis | Mechanism |
|----|----|----|
| Giant "a" waves | TS, CHB, PH | Atrial contraction against increased resistance |
| Absent "a" waves | Atrial fibrillation | No organized atrial contraction |
| Cannon "a" waves | AV dissociation (CHB, VT) | Atrium contracts against closed tricuspid valve |
| Giant "cv" waves | Severe TR | Regurgitant flow into RA during systole |
| Prominent "x" descent | Tamponade, CP | Pericardial descent during systole |
| Prominent "y" descent | Constrictive pericarditis | Rapid early diastolic filling |
| Blunted "y" descent | Tamponade, TS | Impaired rapid filling |
| Kussmaul sign | CP, RV infarction, RCM | Inability to accommodate increased venous return |

### 10.3 The "Square Root Sign" (Dip-and-Plateau)

Rapid early diastolic pressure drop followed by an abrupt plateau. Occurs in **both** constriction and restriction, as well as RV infarction, severe HF, and bradycardia. It is therefore **NOT discriminating** between CP and RCM (10,11,12).

### 10.4 PCWP Waveform Patterns

| Pattern | Diagnosis | Key Feature |
|----|----|----|
| Giant "v" waves (\> 2× mean PCWP) | Acute severe MR | Regurgitant jet into noncompliant LA |
| Giant "a" waves | Mitral stenosis, decreased LV compliance | Atrial contraction against increased resistance |
| Elevated mean with slow "y" descent | Mitral stenosis | Impaired LA emptying |
| Elevated mean with rapid "y" descent | Restrictive cardiomyopathy | Rapid early filling, then abrupt stop |

## 11. Provocative Testing: Unmasking Occult Disease

### 11.1 Fluid Challenge (Saline Loading)

Rapid infusion of 500 mL normal saline over 5–10 minutes. A rise in PCWP to \> 18 mmHg after challenge suggests occult diastolic dysfunction and reclassifies the patient from pre-capillary to post-capillary PH (2,3).

### 11.2 Exercise Hemodynamics

Supine bicycle exercise during RHC. Exercise PH is defined by mPAP/CO slope \> 3 mmHg/L/min. Particularly useful in exertional dyspnea out of proportion to resting hemodynamics (3,4).

### 11.3 Vasoreactivity Testing

Inhaled nitric oxide challenge in suspected PAH to identify the ~10% who are vasoreactive and may respond to calcium channel blockers (3).

### 11.4 Dobutamine Stress Hemodynamics

Used in low-flow, low-gradient aortic stenosis. Differentiates true severe AS (valve area remains \< 1.0 cm²) from pseudo-severe AS (valve area increases) (1).

## 12. Special Considerations for Nephrology

### 12.1 Hemodynamics and Renal Perfusion

The transrenal perfusion gradient — the difference between mean arterial pressure and renal venous pressure (approximated by RA pressure or CVP) — determines effective renal blood flow and GFR. When both sides are compromised (reduced MAP from low CO + elevated renal venous pressure from right heart congestion), the kidney is squeezed from both directions, producing cardiorenal syndrome (9).

### 12.2 RA Pressure as a Predictor of Diuretic Resistance

An elevated RA pressure (\> 15 mmHg) provides a quantitative explanation for diuretic resistance: impaired oral absorption from gut edema, reduced tubular secretion of diuretics, and neurohormonal activation that overwhelms the diuretic effect. RHC data provide the rationale for transitioning to IV diuretics, adding sequential nephron blockade, and accepting the need for mechanical fluid removal (9).

### 12.3 CI and Renal Prognosis

A CI \< 2.0 L/min/m² is independently associated with worsening renal function in heart failure. The nephrologist who sees a rising creatinine in a heart failure patient should ask not just "are we giving too much diuretic?" but "what is the cardiac index, and is this kidney failing from congestion, hypoperfusion, or both?" (9).

### 12.4 PH Classification and Renal Implications

In CpcPH (PVR \> 2 WU), fixed pulmonary vascular remodeling means even aggressive decongestion will not normalize PA pressures. These patients may require chronic diuretic therapy at doses that further compromise renal function — the classic cardiorenal dilemma (3,9).

### 12.5 Monitoring Response to Disease-Modifying Therapy

In diseases like ATTR-CM where disease-modifying therapy exists (tafamidis, acoramidis, vutrisiran), serial RHC can document hemodynamic improvement: declining filling pressures, improving cardiac output, and reduced pulmonary pressures.

## 13. The Illustrative Case: RHC Interpretation Applied

### 13.1 Case Summary

Patient A: a 75-year-old male with suspected ATTR amyloid cardiomyopathy presenting with diuretic-refractory ascites (bumetanide 4 mg BID, dapagliflozin 10 mg, spironolactone 50 mg), EF 55%, and CT findings of "cirrhosis." RHC performed at a referring institution.

### 13.2 Hemodynamic Data

| Parameter      | Measured      | Normal  | Interpretation                        |
|----------------|---------------|---------|---------------------------------------|
| RA             | 23 mmHg       | 0–8     | Severely elevated (~3× upper limit)   |
| RVSP           | 43 mmHg       | 15–30   | Moderately elevated                   |
| RVEDP          | 25 mmHg       | 0–8     | Severely elevated                     |
| PASP           | 54 mmHg       | 15–30   | Moderately-severely elevated          |
| PADP           | 34 mmHg       | 4–12    | Severely elevated                     |
| PCWP           | 28 mmHg       | 4–12    | Severely elevated                     |
| CO             | 2.66 L/min    | 4.0–8.0 | Critically reduced                    |
| CI             | 1.15 L/min/m² | 2.5–4.0 | Cardiogenic shock range               |
| RA SaO₂        | 64%           | 65–75%  | Low (increased extraction)            |
| PA SaO₂ (SvO₂) | 65%           | 65–75%  | Low-normal (borderline hypoperfusion) |

### 13.3 Systematic Interpretation

**Filling pressures:** Both right-sided (RA 23, RVEDP 25) and left-sided (PCWP 28) filling pressures are severely elevated. This is Forrester Profile C — "cold and wet."

**PCWP − RVEDP gradient:** 28 − 25 = +3 mmHg. Left-sided pressures exceed right-sided (direction expected in restriction), but the gradient is narrow, reflecting advanced biventricular infiltrative disease rather than pericardial constraint.

**Cardiac output:** CI 1.15 L/min/m² is critically reduced. Combined with EF 55%, this demonstrates the classic EF–CO dissociation of restrictive physiology. Estimated stroke volume: ~25 mL (normal ~70 mL).

**Pulmonary hypertension:** mPAP ≈ 41 mmHg. TPG = 13 mmHg (elevated). DPG = 6 mmHg (borderline). PVR = 4.9 WU (elevated). This is combined pre- and post-capillary PH (CpcPH).

**RVEDP/RVSP ratio:** 25/43 = 0.58. Exceeds the 1/3 threshold but reflects severity of biventricular diastolic dysfunction, not pericardial constraint.

**SvO₂:** 65% — at the lower limit of normal, confirming increased systemic oxygen extraction.

**Renal implications:** RA 23 mmHg provides the complete explanation for diuretic-refractory ascites. Triple nephron blockade is failing because the hemodynamic driver overwhelms the pharmacologic effect.

### 13.4 Diagnosis Supported by Hemodynamics

**Conclusion:** The hemodynamic profile is consistent with restrictive cardiomyopathy from suspected ATTR amyloidosis with CpcPH, cardiogenic shock-range hemodynamic compromise, and cardiorenal syndrome type 1. The preserved EF of 55% completely conceals the hemodynamic devastation revealed by the RHC.

## 14. Summary and Key Teaching Points

**Key Points**

- RHC provides the definitive hemodynamic assessment that no noninvasive modality can replicate
- The 2022 ESC/ERS definitions lowered the PH threshold to mPAP \> 20 mmHg and pre-capillary PVR to \> 2 WU
- The PCWP is the single most consequential measurement: it determines pre-capillary vs. post-capillary PH classification
- When resting PCWP is borderline (12–15 mmHg), provocative testing should be performed before concluding PH is pre-capillary
- Pressure equalization favors constrictive pericarditis, not restrictive cardiomyopathy; the most discriminating criterion is respirophasic ventricular interdependence
- Preserved EF is the primary cognitive trap in cardiac amyloidosis diagnosis — literature documents a median 13-month diagnostic delay, 44% misdiagnosis rate, and 3- to 5-fold mortality increase
- Shock phenotyping requires RHC to distinguish cardiogenic from distributive and to identify mixed states
- For the nephrologist, RA pressure quantifies renal venous congestion driving diuretic resistance, CI quantifies forward failure compromising renal perfusion
- The "square root sign" is NOT discriminating between constriction and restriction
- Intracardiac shunts are diagnosed by systematic oximetric step-up analysis; Qp/Qs \> 1.5 indicates hemodynamic significance

## References

1.  Ragosta M. Textbook of Clinical Hemodynamics. 2nd ed. Elsevier; 2017. [Publisher textbook](https://shop.elsevier.com/books/textbook-of-clinical-hemodynamics/ragosta/978-0-323-48042-0)
2.  Rosenkranz S, Preston IR. Right heart catheterisation: best practice and pitfalls in pulmonary hypertension. *Eur Respir Rev*. 2015;24(138):642-652. [PubMed](https://pubmed.ncbi.nlm.nih.gov/26621978/)
3.  Humbert M, Kovacs G, Hoeper MM, et al. 2022 ESC/ERS guidelines for the diagnosis and treatment of pulmonary hypertension. *Eur Heart J*. 2022;43(38):3618-3731. [PubMed](https://pubmed.ncbi.nlm.nih.gov/36017548/)
4.  Maron BA, Brittain EL, Choudhary G, et al. Redefining pulmonary hypertension. *Lancet Respir Med* 2018. [PubMed 29269004](https://pubmed.ncbi.nlm.nih.gov/29269004/).
5.  Kittleson MM, Maurer MS, Ambardekar AV, et al. Cardiac amyloidosis: evolving diagnosis and management. *Circulation*. 2020;142(1):e7-e22. [PubMed](https://pubmed.ncbi.nlm.nih.gov/32476490/)
6.  Ladefoged B, Dybro A, Povlsen JA, et al. Diagnostic delay in wild type transthyretin cardiac amyloidosis. *Int J Cardiol*. 2020;304:138-143. [PubMed](https://pubmed.ncbi.nlm.nih.gov/32033783/)
7.  Wechalekar AD, Fontana M, Quarta CC, et al. AL Amyloidosis for Cardiologists: Awareness, Diagnosis, and Future Prospects. *JACC CardioOncol*. 2022;4(4):427-441. [PubMed](https://pubmed.ncbi.nlm.nih.gov/36444232/)
8.  Shchendrygina A, Mewton N, Niederseer D, et al. Cardiac Amyloidosis Screening and Management in HFpEF: An International Survey. *Am J Cardiol*. 2024;236:42-48. [PubMed](https://pubmed.ncbi.nlm.nih.gov/39481586/)
9.  Rangaswami J, Bhalla V, Blair JEA, et al. Cardiorenal Syndrome: Classification, Pathophysiology, Diagnosis, and Treatment Strategies: A Scientific Statement From the AHA. *Circulation*. 2019;139(16):e840-e878. [PubMed](https://pubmed.ncbi.nlm.nih.gov/30852913/)
10. Welch TD, et al. Echocardiographic diagnosis of constrictive pericarditis: Mayo Clinic criteria. *Circ Cardiovasc Imaging*. 2014;7(3):526-534. [PubMed](https://pubmed.ncbi.nlm.nih.gov/24633783/)
11. Talreja DR, et al. Constrictive pericarditis in the modern era. *J Am Coll Cardiol*. 2008;51(3):315-319. [PubMed](https://pubmed.ncbi.nlm.nih.gov/18206742/)
12. Hurrell DG, et al. Value of dynamic respiratory changes in left and right ventricular pressures for the diagnosis of constrictive pericarditis. *Circulation*. 1996;93(11):2007-2013. [PubMed](https://pubmed.ncbi.nlm.nih.gov/8640975/)
13. Kittleson MM, et al. 2023 ACC expert consensus decision pathway on cardiac amyloidosis. *J Am Coll Cardiol*. 2023;81(11):1076-1126. [PubMed](https://pubmed.ncbi.nlm.nih.gov/36697326/)
14. Gillmore JD, et al. Nonbiopsy diagnosis of cardiac transthyretin amyloidosis. *Circulation*. 2016;133(24):2404-2412. [PubMed](https://pubmed.ncbi.nlm.nih.gov/27143678/)

[RHC Comprehensive Guide](https://urinenephrology.org/mastery/rhc/index.html) [Restrictive vs Constrictive](https://urinenephrology.org/mastery/rhc/restrictive-vs-constrictive.html) [ATTR Cardiac Amyloidosis](https://urinenephrology.org/mastery/rhc/cardiac-amyloidosis.html)

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This educational review was prepared by the Medical Associates Department of Nephrology in collaboration with the University of Illinois College of Medicine at Peoria, the University of Dubuque Physician Assistant Program, and the UDPA Butler School of Medicine.

© 2026 Medical Associates Department of Nephrology — Cardiorenal Education Series


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