Wigger’s Diagram: Overview
Diastole: Systole:
Diastole:
Sinoatrial node
generates an
electrical
stimulus
Atrial myocytes
depolarize &
contract
(atrial systole)
Atrial myocytes
repolarize and relax
Septum
depolarizes
Ventricular myocytes
depolarize and contract
(isovolumetric
contraction)
Ventricular myocytes
repolarize and relax
(isovolumetric relaxation)
↓ Left atrial
pressure
Left atrium squeezes blood
into left ventricle through
the open mitral valve
ECG: P-wave**
Left atria fills
with blood from
ECG: Q-wave ECG: R-wave ECG: T-wave
↑ Left
pulmonary
ventricular
circulation
pressure
Atrial pressure:
‘x’ descent
↓ Left ventricular
pressure
↑ Left atrial
pressure
↑ Left atrial
pressure
↑ Left ventricular
volume
Left ventricular pressure >
left atrial pressure
Mitral valve
bulges into
left atrium
Left ventricular
pressure >
aortic pressure
Atrial pressure:
‘v’ wave
Atrial
pressure:
‘a’ wave
↑ Left ventricular
pressure
Mitral valve closes
Atrial pressure:
‘c’ wave
Aortic valve opens
First heart sound (S1)
Left ventricle squeezes
blood into aorta (ejection)
↑ Aortic pressure Legend: Pathophysiology Mechanism
Left atrial pressure >
left ventricular pressure
Mitral valve opens
Rapid inflow of blood
into left ventricle from
left atria
↓ Left ventricular
volume
↑ Left
ventricular
volume
↓ Left atrial
pressure
↓ Left ventricular
pressure
Atrial pressure:
‘y’ descent
Aortic pressure >
left ventricular pressure
Aortic valve closes
Second heart sound (S2)
**See slide on PHYSIOLOGY OF THE NORMAL ECG WAVEFORM (LEAD II)
Author:
Nathan Archibald
Reviewers:
Stephanie Happ
Emily Kuervers
Sergio F. Sharif
Angela Kealey*
* MD at time of publication
Sign/Symptom/Lab Finding Complications
Published May 19, 2025 on www.thecalgaryguide.com