The flow-directed balloon-tipped pulmonary artery catheter reads RA, RV, PA, and wedge pressures and measures cardiac output. ESCAPE found no benefit from routine PAC-guided care in its advanced-HF population. This does not settle its role in shock. Place it for a consequential question and act on the answer. Zero to atmosphere and level at the mid-thoracic reference. Record respiratory conditions and the measurement convention.
▤
Catheter advancement: RA → RV → PA → wedge
watch the waveform change
RA → RV → PA → PAWP. Original uncalibrated teaching traces. The highlight guides the reading order, not a physiologic timescale. Confirm position from the complete tracing.
The transitions tell you where you are RV adds a tall systolic spike with near-zero diastole; PA keeps that systolic but the diastole rises and a dicrotic notch appears; wedging abolishes the systolic wave → damped a/v. PADP, mean PAWP and LVEDP are different measurements. Pulmonary vascular disease, mitral disease, atrial waves and timing can separate them.
A
Normal values & wave components
know the numbers
RA/CVP2–6 · RV15–30 / 2–8
PA15–30 / 8–15 (mean 10–20) · PCWP6–12
CO / CI4–8 L/min / 2.5–4.0 · SvO₂60–75%
a wave atrial contraction · c tricuspid closure · v atrial filling.
x descent atrial relaxation · y descent early ventricular filling.
Report the mean for RA & wedge; systolic/diastolic for RV & PA.
B
Read it right — pitfalls
avoid the artifacts
End-expiration read without breath-holding. Obesity, COPD, PEEP and exercise may keep intrathoracic pressure positive. With large swings, average ≥3–4 cycles and state the method.
Confirm wedge credible a/v tracing, occlusion position and O₂ saturation approaching arterial. PAWP need not be below PADP when V waves are large.
Over-wedge rising tracing → deflate, pull back; never inflate against resistance (PA rupture).
Different pressures mean PAWP reflects LA burden. LVEDP is one LV instant. Compare timing and loading conditions.
Damping keep the line flushed — an over- or under-damped trace mis-reads systolic/diastolic.
C
Insertion, position & complications
float it · don't hurt
Step
Detail
Access
Select access with ultrasound and patient-specific anatomy. Follow the catheter IFU. Deflate the balloon before withdrawal.
Depths (from RIJ)
RA ~20–25 · RV ~30–35 · PA ~40–45 · wedge ~45–55 cm.
On passage
Transient RV ectopy / RBBB — with pre-existing LBBB can cause complete block → have pacing ready.
PA rupture
Over-wedging / distal tip / pulmonary HTN → hemoptysis; never inflate against resistance.
Confirm on CXR
Confirm a safe proximal PA position and a PA waveform after deflation. Avoid distal migration. Never exceed the model-specific balloon limit.
Place it for undifferentiated or refractory shock, suspected RV / biventricular failure, severe HF not responding to therapy, pre-MCS / transplant evaluation, and sorting pulmonary-arterial vs post-capillary pulmonary hypertension.
The catheter's value is in what you compute from it — flow, resistances, and the power/pulsatility indices that grade shock severity and RV failure — and in the waveform signatures that name the lesion at the bedside.
A
The formulas that matter
flow · resistance · power
Index
Formula
Normal / threshold
Fick CO
VO₂ / [(SaO₂−SvO₂) × Hb × 13.4]. Saturations as fractions. VO₂ in mL/min, Hb in g/dL. Name measured vs estimated VO₂
4–8 L/min
Thermodilution CO
Cold-saline bolus, area under temp curve (average ≥3 consistent curves)
Preferred when measured-VO₂ Fick is unavailable; invalid with shunt
SVR
(MAP − RAP) / CO × 80
800–1200 dyn·s·cm⁻⁵
PVR
(mPAP − mean PAWP) / Qp
WU. Multiply by 80 for dyn·s·cm⁻⁵. PVR >2 WU enters current pre-capillary PH criteria
CPO
(MAP × CO) / 451
<0.6 W → ↑ mortality in shock
PAPi
(PASP − PADP) / RAP
low → severe RV dysfunction
B
Waveform signatures — name the lesion
cross-ref the cards
Finding
Means
See card
Giant v wave (PCWP)
Consider MR or reduced LA compliance. A large RA v wave supports TR. Neither alone grades valve severity
MI-MECH · SHOCK
O₂ step-up RA→RV
Suspect ventricular-level left-to-right shunting. Verify sampling and anatomy
MI-MECH
Equalized diastolics, blunted y
Supports tamponade in context
PERICARD
Dip-plateau, prominent y, Kussmaul
Consider constriction or restriction. Respiratory ventricular interaction helps distinguish them
PERICARD
Cannon a waves
AV dissociation (CHB, VT); large a = stiff RV / TS
ARRHYTH
↑ RA, low PCWP, low PAPi
RV infarct / RV failure
SHOCK
C
The 2×2 — profile the patient
CI × filling pressure
WARM & DRY CI >2.2 · PAWP <18 — often compensated. Reconcile symptoms and perfusion.
WARM & WET CI >2.2 · PAWP >18 — congestion. Individualize decongestion and afterload treatment.
COLD & DRY CI <2.2 · PAWP <18 — verify flow and perfusion. Fluid only when underfilling is plausible.
COLD & WET CI <2.2 · PAWP >18 — assess hypoperfusion. Low CI alone does not mandate an inotrope or MCS.
Tie it together CPO and PAPi are load- and context-dependent risk markers. Combine them with perfusion, echo, trends and the cause of shock. They do not select a device on their own.
D
Oxygen & the mixed-venous sample
supply vs demand
SvO₂ (PA) normal 60–75%; low = ↓ delivery (low CO / anemia / hypoxemia) or ↑ extraction.
Shunt (Qp:Qs) a reproducible ventricular-level O₂ step-up suggests a shunt. Confirm a full saturation run and anatomy.
Pair with lactate follow lactate, SvO₂, mentation, urine output and organ function. No single normal value excludes hypoperfusion.
E
Numbers → device choice
LV · RV · BiV
Pattern
Problem
Direction
↓ CPO, ↑ PCWP, normal RA
LV failure
Assess LV function, cause, perfusion and response to treatment
↑ RA relative to PAWP, ↓ PAPi
RV failure
Assess preload, afterload, RV ischemia and support needs
Both ↓ CPO & ↓ PAPi
BiV failure
Assess both ventricles and oxygenation with the shock team
Normal CPO & PAPi, ↑ PCWP
Congestion, not flow
Treat congestion and reassess perfusion. No automatic device rule
Two ways to measure cardiac output — direct Fick with measured VO₂ (reference method) and thermodilution (cold-saline indicator). When measured VO₂ is unavailable, prefer thermodilution over assumed Fick. Shunt → direct Fick + sat run; TR alone does not invalidate thermodilution; reconcile discordant methods.
A
Fick — the deep dive
O₂ in = O₂ out
Principle at steady state, pulmonary O₂ uptake = tissue O₂ consumption → CO = VO₂ / (CaO₂ − CvO₂).
Working equationCO = VO₂ / [(SaO₂ − SvO₂) × Hb × 1.34 × 10] (1.34 mL O₂/g Hb · ×10 = dL→L). Use saturation fractions.
VO₂ — measured vs assumedmeasured (metabolic cart) = direct Fick; assumed = 125 mL/min/m² × BSA (or LaFarge) — only an estimate.
Assumed-Fick error the VO₂ estimate may be inaccurate. In VA CART, estimated-Fick and thermodilution CI differed by >20% in 38.1%. Reconcile consequential disagreement rather than averaging methods.
▤
Thermodilution curves — read the shape
AUC ∝ 1/CO
B
Thermodilution troubleshooting
when the number lies
Pitfall
Effect → fix
Tricuspid regurgitation
May distort the curve, but thermodilution often retains reasonable clinical accuracy → repeat consistent injections and reconcile with measured-VO₂ direct Fick if discordant.
Very low output
Delayed washout can increase variance → repeat ≥3 consistent curves; if clinically discordant, use measured-VO₂ direct Fick.
Intracardiac shunt
Thermodilution invalid — early recirculation; quantify with measured-VO₂ direct Fick + sat run.
Injectate problems
Warm / insufficient volume / slow or uneven push → error → 10 mL, brisk, consistent; iced if needed.
Catheter position
Tip against wall / partial wedge → damped curve → reposition; average 3 within 10%.
Shivering / agitation
Changing VO₂ and blood temperature undermine steady state. Treat the cause, document conditions and repeat once stable.
Shunt run / Qp:Qs estimated mixed venous saturation may use (3×SVC + IVC)/4, but streaming and anatomy matter. Qp:Qs = (CaO₂ − CmvO₂)/(CpvO₂ − CpaO₂). Use oxygen content, especially with high FiO₂. The ratio alone does not determine closure. → signatures on P.2
C
Pick the method · worked Fick
when each wins
Use measured-VO₂ direct Fick when
Any intracardiac shunt (thermodilution invalid) or a method discrepancy must be adjudicated.
A true measured VO₂ is available (metabolic cart); do not substitute assumed VO₂ when precision matters.
Use thermodilution when
Measured VO₂ is unavailable and there is no intracardiac shunt — including low output or TR when curves are reproducible.
Trending serial CO (titrating inotrope / weaning).
Worked Fick Hb 12, SaO₂ 98%, SvO₂ 60%, assumed VO₂ 250 mL/min → CO = 250 / [(0.98 − 0.60) × 12 × 1.34 × 10] = 250 / 61.1 ≈ 4.1 L/min. A wrong VO₂ guess scales the answer directly — measure it when the number must be right.
Index it CI = CO/BSA · SVI = SV/BSA · use indexed flow for PVRi/SVRi.
Anemia at fixed VO₂ and CO, the O₂ content difference is unchanged. Lower Hb requires a wider saturation difference.
Steady state Fick assumes it — invalid during rapidly changing hemodynamics / unstable FiO₂.
Beyond cardiac output, the RHC answers specific diagnostic questions — classify pulmonary hypertension, test vasoreactivity, run a shunt, separate constriction from restriction, and unmask occult HFpEF with exercise or fluid challenge.
▤
Pulmonary hypertension — pre- vs post-capillary
PCWP & PVR split it
A
Diagnostic protocols
what RHC answers
Question
Protocol
PH classification
mPAP, PCWP, PVR → pre- vs post- vs combined (above).
Vasoreactivity
At a PH center for idiopathic, heritable or drug-associated PAH. Inhaled NO or iloprost are preferred. Positive: mPAP falls ≥10 to ≤40 mmHg with unchanged/increased CO. IV adenosine is no longer recommended.
Constriction vs restriction
Respiratory RV/LV systolic discordance supports constriction. Equalization or dip-plateau alone is nonspecific. → PERICARD
Low-flow low-gradient AS
Dobutamine challenge — true-severe vs pseudo-severe.
B
Exercise & provocative RHC
unmask occult HFpEF
Exercise (supine cycle)
Supine end-expiratory PAWP ≥25 mmHg or PAWP/CO slope >2 supports abnormal filling-pressure reserve. Match posture and respiratory method to the validated protocol.
Exercise PH if mPAP/CO slope > 3.
Provocative
Saline challenge: ~500 mL over 5–10 min with PAWP ≥18 mmHg suggests occult HFpEF. Use selected monitored testing.
Passive leg raise is a different maneuver. Do not assign it the saline threshold. Interpret with phenotype and loading conditions.
Safety limits do not cross a mechanical TV/PV. Review thrombus/mass, bleeding risk and the safest approach.
Don't cath if it won't change management — answer a question, then act.
The same RH access enables endomyocardial biopsy (EMB) — high-yield for rejection surveillance and select myopathies, low-yield (and risky) when fired blindly. Know the indications, the route, and the kit.
A
Endomyocardial biopsy
indication-driven
Indicationstransplant rejection surveillance (scheduled); new/unexplained HF with suspected giant-cell myocarditis, infiltrative disease, or arrhythmia — when the result changes management.
Technique Target the RV septum or selected LV site under imaging. Prearrange specimen handling: ≥3 samples for histology/immunohistology and separate samples for indicated molecular studies. Special fixation may be needed for EM.
Before consent · review coags/platelets · access-site US · NPO if sedation · confirm the question the RHC will answer.
After hemostasis, access and perfusion checks. Assess pneumothorax risk after thoracic access and obtain imaging when indicated. Watch for tamponade after EMB.
D
Do the study · pick the access
steps & site
Step-by-step
Zero/level transducers at the phlebostatic axis; access & place sheath.
Float the PA catheter (balloon up) → record RA → RV → PA → wedge; CO (Fick & thermo); sat run if shunt.
Add provocation as needed (exercise, fluid, vasoreactivity); EMB last.
Access choice
RIJ is a common route. EMB may use femoral or selected LV access with appropriate expertise.
Femoral if IJ/SC contraindicated; antecubital/basilic for ambulatory / serial studies.
Avoid SC if coagulopathic (non-compressible).
E
What the biopsy reports
rejection & myocarditis
Acute cellular rejection (ISHLT)
0R none · 1R mild · 2R moderate · 3R severe. Urgent transplant-team assessment for symptomatic rejection. Treatment depends on grade, timing and graft function.
pAMR uses histology and immunopathology: 0, 1(H+), 1(I+), 2 or 3. DSA and graft function inform clinical interpretation but do not define the pathologic grade.
Myocarditis (Dallas + stains)
Integrate histology, immunostaining and clinical phenotype. Giant cells need expert distinction from granulomatous disease.
Special: Congo red (amyloid), iron, viral PCR. → Myocarditis card
F
Quick reference — normals & formulas
the whole card on one line each
Value
Normal
Formula
RA · PCWP
2–6 · 6–12 mmHg
mean (end-expiration)
PA
15–30 / 8–15 (mean 10–20)
—
CI · SVR · PVR
2.5–4.0 · 800–1200 · <2 WU
SVR: (MAP−RAP)/Qs·80 · PVR: (mPAP−PAWP)/Qp
CPO · PAPi
>0.6 W · context
MAP·CO/451 · (PASP−PADP)/RAP
One-liner: place the RHC to answer a question — read at end-expiration (P.1), compute & recognize the signatures (P.2), use measured-VO₂ direct Fick as reference and thermodilution when measured VO₂ is unavailable; a shunt needs direct Fick + sat run, and TR/low output require curve quality plus discordance review (P.3). Use vasoreactivity / exercise / fluid challenge to classify PH and unmask HFpEF (P.4). EMB is indication-driven; have a pericardiocentesis tray ready. → counterpulsation now lives on the IABP card.