Arterial pulse waveform

Normal components

Pressure
  ^
  |                 2. Systolic peak
  |                /\
  |               /  \
  | 1. Rapid      /    \ 3. Systolic decline
  |    upstroke  /      \__
  |             /          \_ 4. Dicrotic notch
  |____________/             \__
  |                            \___ 5. Diastolic runoff
  |____________________________________________> Time
                     6. End-diastolic pressure

1. Rapid systolic upstroke (anacrotic limb)
   • Starts when the left ventricle ejects blood after the aortic valve opens.
   • The steepness reflects the rate of ventricular ejection and arterial compliance.
2. Systolic peak
   • The maximum arterial pressure in that cardiac cycle: the systolic blood pressure.
   • It reflects stroke volume, speed of ejection, aortic compliance, and wave reflection from peripheral arteries.
3. Systolic decline
   • Begins as left-ventricular ejection slows late in systole.
4. Dicrotic notch (incisura)
   • A small notch on the descending limb caused mainly by aortic valve closure.
   • It marks the end of left-ventricular ejection and onset of diastole. A small brief retrograde movement of blood toward the valve, followed by elastic recoil of the aorta, contributes to it.
   • It is sharp in central aortic recordings and tends to be later and less distinct in peripheral arteries.
5. Diastolic runoff
   • During diastole, blood flows from the elastic arterial system into the peripheral circulation. Arterial pressure gradually falls.
   • The rate of fall depends mainly on peripheral vascular resistance and arterial compliance.
6. End-diastolic pressure
   • The lowest pressure just before the next systolic upstroke: the diastolic blood pressure.

Timing in relation to the cardiac cycle

• ECG R wave occurs first.
• After electromechanical delay and isovolumetric contraction, the aortic valve opens.
• The arterial upstroke then begins.
• The dicrotic notch corresponds approximately to aortic valve closure and the second heart sound, A2.

Central versus peripheral waveform

• Systolic upstroke becomes steeper.
• Systolic pressure usually increases.
• Diastolic pressure may decrease.
• Pulse pressure widens.
• The dicrotic notch becomes more delayed and may be less sharp.

Important determinants of waveform shape

Common abnormal patterns

• Pulsus parvus et tardus: small, slowly rising pulse, typical of severe aortic stenosis.
• Bounding or collapsing pulse: rapid rise and fall, often in aortic regurgitation or other high-output states.
• Bisferiens pulse: two systolic peaks, classically in severe aortic regurgitation with or without aortic stenosis, or hypertrophic obstructive cardiomyopathy.
• Dicrotic pulse: a second palpable peak in diastole, often in low-output states with high peripheral resistance.
• Pulsus alternans: alternating strong and weak beats, suggesting severe left-ventricular systolic dysfunction.
• Pulsus paradoxus: excessive inspiratory fall in systolic pressure, seen with cardiac tamponade, severe asthma, or severe COPD.

Tidal peak (tidal wave)

• It is produced mainly when the forward pressure wave meets resistance in the peripheral arterial tree and a portion is reflected back toward the heart.
• This reflected wave adds to the original forward wave, creating a late systolic hump or second peak.
• It is often more evident in peripheral arteries and becomes more prominent when arteries are stiff, such as with aging.

Dicrotic notch

• It occurs when left-ventricular ejection ends and the aortic valve closes.
• Just after closure, there is a brief tendency for blood to move backward toward the valve. Closure of the valve and elastic recoil of the aorta cause a small pressure oscillation, seen as the notch.
• It marks the transition from systole to diastole and occurs close to the aortic component of the second heart sound, A2.

Position in the waveform

                 systole                         diastole
                    |                               |
                    v                               v
              systolic peak
                   /\
                  /  \___ tidal peak
                 /        \__
________________/            \_ dicrotic notch
                               \__
                                  \_____ diastolic runoff

Key difference