6.1 Right Heart Waveforms & Pressures

6.1 Right Heart Waveforms & Pressures

Quick Answer: Right heart catheterization generates a sequential pressure map from the right atrium through the pulmonary artery and, when wedged, the pulmonary capillary wedge position. The RCIS must recognize normal numeric ranges, identify characteristic waveform components (a, c, and v waves), and immediately distinguish true hemodynamics from dampening or whip artifacts before the operator records values or makes clinical decisions.

Right heart catheterization (RHC) is the foundation of invasive hemodynamic assessment in the cath lab. As an RCIS, you do not interpret hemodynamics independently — but you monitor tracings in real time, confirm that waveforms look physiologic before values are recorded, reposition catheters when artifacts appear, and anticipate when abnormal patterns warrant additional measurements. CCI's Diagnostic Procedures domain weights hemodynamics heavily; waveform recognition is tested repeatedly.

Why Waveform Quality Matters First

A pressure number is only as reliable as the tracing behind it. Operators and RCIS staff routinely see two artifact patterns that produce falsely normal or falsely abnormal readings:

• Dampening (overdamping): amplitude is reduced, the waveform looks "flat" or sluggish, and systolic peaks may be underestimated while diastolic values may appear falsely elevated or indistinct.
• Whip (underdamping / motion artifact): sharp, narrow spikes appear that do not correlate with the cardiac cycle — often from catheter flopping in a large chamber or vessel, from patient movement, or from excessive system resonance.

Before accepting any chamber pressure, confirm: clear systolic upstroke, appropriate dicrotic notch where expected (PA), visible a and v waves (RA and wedge), and stable baseline without erratic spikes.

Normal Chamber Pressures

These ranges assume supine position, normal mitral/tricuspid competence, and no significant lung disease. Always document patient position because pressures shift with posture and ventilation.

PCWP interpretation: When the balloon is properly inflated and wedged, PCWP approximates left atrial pressure and left ventricular end-diastolic pressure (LVEDP) in patients with a normal mitral valve. If mitral regurgitation is severe, the wedge tracing may show a giant v wave (see below) and PCWP may not reflect true LVEDP.

Right Atrial Waveform Morphology

The RA tracing is the most complex right-heart waveform because it reflects atrial events directly:

Exam trap: Students confuse a wave (atrial contraction) with v wave (passive filling). Remember: a = active atrial kick; v = venous return volume.

RV, PA, and PCWP Tracings

Right ventricle: A rapid systolic upstroke to 15–30 mmHg, then a sharp drop to near-zero diastolic pressure. RV diastolic pressure should approximate RA mean in normal hearts. A diastolic gradient between RA and RV suggests tricuspid stenosis.

Pulmonary artery: Systolic peak (15–30), diastolic trough (4–12), and a dicrotic notch from pulmonic valve closure. PA pressure rises with pulmonary vascular disease, left-heart failure (back-pressure), and significant left-to-right shunts.

PCWP (wedge): Resembles RA morphology but is delayed and filtered through the pulmonary capillary bed. Look for a and v waves. In severe mitral regurgitation, the v wave becomes prominent — often more than twice the mean wedge — because regurgitant flow raises left atrial pressure during systole.

Dampening: Recognition and Troubleshooting

Dampening occurs when the pressure transmission system loses fidelity. Common causes:

1. Air in the line — most frequent; flush and aspirate carefully
2. Clot or fibrin at catheter tip — waveform dampens progressively; may need wire flush or catheter exchange
3. Kinked tubing or stopcock misalignment — check entire circuit from catheter to transducer
4. Catheter tip against wall — withdraw slightly and re-advance under fluoroscopy
5. Small-gauge or damaged catheter lumen — consider replacement

RCIS response checklist:

• Stop recording abnormal values until the tracing is corrected
• Notify the operator immediately if dampening persists after flush
• Document whether values were obtained from a dampened tracing (many labs require re-measurement)
• Verify transducer zeroed at phlebostatic axis (mid-axillary line, fourth intercostal space)

Whip Artifacts

Whip produces tall, narrow spikes unrelated to cardiac timing. Causes include catheter slack in RA or RV, patient coughing or movement, and underdamped systems with excessive resonance.

Differentiating whip from true pressure: Whip spikes are erratic, not reproducible beat-to-beat, and often disappear when the catheter is repositioned or the patient is still. True ventricular or arterial pressures follow consistent systolic-diastolic timing.

RCIS action: Hold the catheter shaft gently to reduce motion (without pulling it back), ask the patient to breathe quietly, and confirm the operator reviews the tracing before locking in a number.

Worked Scenario: Is This PCWP Valid?

A wedge tracing shows mean 18 mmHg but the waveform is flat with no visible a or v waves and a sluggish upstroke. Do not record 18 mmHg as PCWP. The morphology suggests dampening. Flush the line, confirm balloon inflation volume (typically 1.0–1.5 mL for standard 7F PA catheters — follow institutional protocol), and re-wedge. After correction, a valid tracing shows distinct a and v waves; if mean remains 18 mmHg with good morphology, that value supports elevated left-sided filling pressure.

Hemodynamic Sequencing During RHC

Standard pull-back order for pressure recording:

1. PA (confirm PA waveform — not wedged)
2. PCWP (balloon inflated briefly)
3. Pull back to RV
4. Pull back to RA
5. Record simultaneous pressures when indicated (e.g., RV and PCWP for PVR calculation)

Always deflate the balloon immediately after wedge measurement to avoid pulmonary artery rupture.

RCIS Scope Reminder

Your role is to support accurate data acquisition: zero transducers, verify waveform quality, communicate artifact concerns, and maintain sterile technique during catheter manipulation. Clinical interpretation belongs to the physician — but CCI expects you to recognize normal ranges and artifact patterns cold.