Chart — Critical Care · Cardiac

Arterial Waveform Interpretation Chart

Normal waveform components (systolic peak, dicrotic notch as aortic valve closure, diastolic runoff), dampened vs over-amplified waveform patterns, troubleshooting steps, fast-flush square wave test, pulse pressure analysis, and pulsus paradoxus.

Educational use only. NEVER inject medications into an arterial line. Clearly label all arterial line tubing. Waveform interpretation must be correlated with direct patient assessment and non-invasive BP as needed. This material supports nursing education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional policy, or medical direction. Always follow facility protocols and current provider orders.

Waveform Components

Waveform Component	Meaning
Systolic Upstroke	Steep ascending limb = LV ejects blood against SVR. The slope reflects contractility.
Anacrotic Notch	Small notch on ascending limb (sometimes visible). Aortic valve opening. More prominent in severe aortic stenosis. Often not visible on peripheral lines.
Systolic Peak	Highest point = systolic blood pressure (SBP).
Systolic Decline	Downstroke = passive LV relaxation. Rate reflects SVR and arterial compliance.
Dicrotic Notch ⭐ KEY	LANDMARK notch in downstroke = aortic valve closure. Separates systole from diastole. Loss of dicrotic notch = dampened waveform. Position (high vs low) reflects SVR.
Diastolic Runoff	Gradual post-notch decline = diastolic pressure sustained by aortic recoil and elastic recoil. Maintained DBP = adequate diastolic filling time.
Diastolic Trough	Lowest point before next systole = diastolic blood pressure (DBP).

Key Landmark: Dicrotic Notch = Aortic Valve Closure. Loss of dicrotic notch = dampened waveform (air, clot, kink). Unusually low dicrotic notch = decreased SVR or hypovolemia. High dicrotic notch = increased SVR.

Waveform Types — Normal vs Abnormal

Normal Waveform

Sharp systolic upstroke → systolic peak → downstroke → dicrotic notch → diastolic runoff

Key features	Steep ascending limb (systolic upstroke) = LV ejection against SVR Systolic peak = SBP Dicrotic notch visible in downstroke = aortic valve closure landmark Gradual diastolic runoff = arterial elastic recoil Diastolic trough = DBP Waveform crisp and well-defined
BP effect	Displays accurate SBP, DBP, MAP
Fast-flush test	Fast-flush test: sharp square wave with 1–2 oscillations before returning to waveform (optimal dynamic response)
Nursing Action	No action needed — continue routine monitoring every 1–4 hours. Re-level and re-zero with position changes.

Dampened Waveform

Blunted, rounded waveform with low amplitude. Dicrotic notch absent or barely visible.

Key features	Slowed, blunted systolic upstroke Decreased peak height Loss of dicrotic notch (absent or very difficult to see) Rounded appearance — loss of sharp distinct features Falsely LOW systolic BP reading Mean arterial pressure often less affected than SBP
BP effect	FALSELY LOW SBP displayed. MAP less affected. Correlate with non-invasive BP if concerned.
Fast-flush test	Fast-flush test: rounded square wave, slowly returns to baseline (over-damped = too much resistance in system)
Nursing Action	Troubleshoot: (1) Check for catheter kinking → straighten. (2) Tighten all connections (loose Luer-lock). (3) Perform fast-flush. (4) Inspect for air bubbles → remove. (5) Check flush bag pressure (300 mmHg). (6) Aspirate gently if clot suspected, then flush. (7) Notify provider if persistent — line may need repositioning or replacement.

Over-Amplified (Resonant) Waveform

Exaggerated, tall spiky waveform with falsely elevated systolic peaks. Dicrotic notch may not be visible.

Key features	Exaggerated systolic upstroke and peak height Falsely HIGH systolic BP reading Tall sharp spikes Diastolic may appear normal or low Can look like a very high-pressure system Resonance = system vibrating at natural frequency → signal amplification
BP effect	FALSELY HIGH SBP displayed. Risk: treating hypertension that does not exist, withholding vasopressors when MAP actually low.
Fast-flush test	Fast-flush test: multiple oscillations (ringing) before returning to waveform (under-damped = resonance problem)
Nursing Action	Correct resonance: (1) Shorten tubing (> 48 inches = resonance risk). (2) Remove all air bubbles from system (paradoxically, small air bubbles can cause resonance). (3) Use stiff non-compliant pressure tubing (avoid soft IV tubing for arterial lines). (4) Add inline damping device if available. (5) Correlate with non-invasive BP.

Flatline / No Waveform

No visible waveform — zero amplitude. Different from severely dampened.

Key features	Complete absence of waveform No oscillations visible Monitor may display dashes or zero values
BP effect	No BP displayed. FIRST: assess patient immediately — is this patient hemodynamically compromised or is it equipment failure?
Fast-flush test	Fast-flush test: no response (stopclock may be closed, or complete obstruction)
Nursing Action	FIRST PRIORITY: Assess patient directly. THEN troubleshoot: (1) Check stopcock position (open to patient?). (2) Check flush bag pressure (300 mmHg — is the bag empty?). (3) Check all connections (disconnected tubing?). (4) Try flush device. (5) If equipment verified and patient hypotensive: initiate hemodynamic support while notifying provider urgently.

Pulse Pressure Analysis

Finding	Value	Clinical Implications
Normal pulse pressure	30–50 mmHg (SBP − DBP)	Normal SV, adequate MAP. Typical for normovolemic patient.
Narrow pulse pressure (< 25 mmHg)	SBP − DBP < 25 mmHg	Low SV (cardiogenic shock, hypovolemia), cardiac tamponade (Beck's triad), severe aortic stenosis. High SVR compresses the pulse pressure.
Wide pulse pressure (> 60–70 mmHg)	SBP − DBP > 60 mmHg	Aortic regurgitation (classic: wide pulse pressure + bounding pulses), severe vasodilation (septic shock early, fever), AV fistula/shunting, hyperthyroidism, high CO states.
Pulsus paradoxus (> 10 mmHg)	SBP drops > 10 mmHg with normal inspiration	Cardiac tamponade (Beck's triad: hypotension + JVD + muffled heart sounds), severe obstructive lung disease (asthma/COPD during exacerbation). Normal physiology: slight SBP drop with inspiration (< 10 mmHg).

Transducer Position Effects

Correct position	4th ICS, midaxillary line (phlebostatic axis). Level to right atrium. Mark on patient skin. Re-level with every position change.
Transducer TOO HIGH	Reads FALSELY LOW BP. Gravity creates a negative pressure effect on the fluid column. Risk: overtreating “hypotension” that is not real.
Transducer TOO LOW	Reads FALSELY HIGH BP. Hydrostatic pressure from elevated fluid column adds to reading. Risk: under-treating actual hypotension.
Magnitude of error	Every 2.5 cm (1 inch) transducer height change = approximately 2 mmHg error in reading.
Zeroing	Open stopcock to air → press “zero” on monitor → close stopcock. Zero at each shift, after position changes, and when readings seem inaccurate.

NCLEX Pearls

Dicrotic notch = aortic valve closure — the key landmark. Loss of dicrotic notch = dampened waveform.

Dampened waveform = falsely LOW SBP. Over-amplified = falsely HIGH SBP. Both require troubleshooting before acting on the displayed value.

Phlebostatic axis = 4th ICS, midaxillary line. Transducer too high → low reading. Too low → high reading.

Dampened waveform troubleshooting order: check kinking → tighten connections → fast-flush → remove air bubbles → notify provider.

NEVER inject medications into arterial line — causes severe ischemia and potential limb loss. Label “ARTERIAL — DO NOT INJECT.”

Pulsus paradoxus > 10 mmHg = cardiac tamponade or severe obstructive lung disease (asthma, COPD). SBP falls > 10 mmHg with normal inspiration.

Narrow pulse pressure (< 25 mmHg) = cardiac tamponade, severe AS, hypovolemia, cardiogenic shock. Wide pulse pressure (> 60 mmHg) = aortic regurgitation, early sepsis.

Allen's test before radial arterial line: flush in < 7 seconds after ulnar release = adequate collateral = safe to cannulate radial artery.

Related Resources

Arterial Line Nursing GuideFull guide: Allen's test, setup, blood sampling, neurovascular monitoring, complications

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Arterial Line ReferenceQuick-reference: transducer setup, waveform components, blood draw procedure

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Standards & sources

Fact-checked Jun 20, 2026

This page is written to align with Society of Critical Care Medicine (SCCM) · Surviving Sepsis Campaign · American Association of Critical-Care Nurses (AACN). It is an educational summary, not a citation of any single document — always verify specific doses, values, and protocols against current guidelines and your facility policy. How we source content →