The Cardiac Cycle
Chapter 3
Ara G. Tilkian, MD, FACC
Instructor
Patricia L. Thomas, MBA, RCIS
The Cardiac Cycle
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Atrial and Ventricular Diastole and Systole
The sounds of the Heart
The valves and papillary Muscles
Valvular Pathophysiology
Atrial & Ventricular Diastole
• Phase of Cardiac Cycle (see 3.1 A)
• Atrial Diastole
– Venous blood enters RA via SVC & IVC
– Pulmonary Blood enters the LA via the 4 PV
Atrial and Ventricular Diastole
Atrial & Ventricular Diastole
• Ventricle Diastole-two phases
– #1 Early passive filling (both atria/ventricles
are
relaxed
– #2 Late active filling (atrial systole or AKick)(see 3.1 B)
– 3rd and 4th heart sounds (S3 & S4)
– 3rd HS the initial rapid filling phase early in
diastole
– 4th HS the final filling phase at the end of
diastole
Atrial Systole, Late Active Filling Phase
Atrial and Ventricular Systole
• Atrial Systole
– Occurs in response to depolarization
– Contraction occurs toward the end of
ventricular diastole (atrial-kick) before the
ventricles contract
– Electrical impulse traveling to the ventricles is
normally delayed momentarily in the AV node
premitting the atrial contraction to augment
ventricular filling.
Atrial and Ventricular Systole
• Ventricular Systole
– Occurs in response to the depolarization wave within
the ventricles the QRS wave
– Venous blood is propelled from the RV the the PA for
oxygenation
– Oxygenated blood is propelled from the LV through
the AO to systemic circulation
– Onset of ventricular systole the AV and PV are still
closed. (isovolumic ventricular contraction) (see 3-1
C)
– When the aortic and pulmonic valves open (rapid
ejection)
Isovolumic Ventricular Contraction,
Beginning of Ventricular Systole
Ventricular Systolic Ejection
The Sound of the Heart
• S1 closure of the Mitral & Tricuspid valves
• S2 closure of the Aortic & Pulmonic
• S3 passive ventricular filling sound
(early diastole)
• S4 active ventricular filling sound
(late diastole)
The First Heart /Ejection Sounds
• Mitral valve closure closely followed by tricuspid
valve closure
• Closure occurs when the onset of ventricular
systole abruptly raises the ventricular pressure
above that of the atria
• The aortic valve opens (AO) followed by the
opening of the pulmonic valve (PO)
• The opening of the two semilunar valves is
normally not heart
• A diseased aortic/pulmonic valve may produce an
ejection sound
The Second Heart Sound
• Aortic valve closure (AC) closely followed by
pulmonic valve closure (PC)
• The two valves close when the systolic ejection into the
aorta/pulmonary artery declines and rising pressure in
these great vessels exceeds the pressures in the
respective ventricles, reversing the flow and causing
the closure of their valves.
• Isovolumic relaxation is after the closure of the AV/PV
but before opening of the MV/TV results in a rapid fall
in ventricular pressure
• Ventricular = Atrial pressure MV/TV opens silently
• If valves are abnormal/stenosed an opening snap (OS)
or click may be heard
The Third Heart Sound
• Rapid filling of the left ventricle
following the opening of the mitral
valve
• Physiological in young people
• Pathological in people with
congestive heart failure or ventricular
dilatation
The Fourth Heart Sound
• Blood being forced into a stiff or
noncompliant LV by the atrial contraction
• Late diastolic event that should be silent
• Atrial diastolic gallop when heard
• Stiff ventricles may be caused by
hypertension, ischemia, outlet obstruction,
or hypertrophic or infiltrative myopathies
The Valves and Papillary Muscles
The Atrioventricular Valves
• Competence of the AV valves depends on
the chordae tendineae (CT)
• CT are attached to the free edges and
ventricular surfaces of the valve cusps
• CT are attached to fingerlike projections of
muscle tissue from the endocardium called
the papillary muscles
The Semilunar Valves
• Aortic and Pulmonic valves are
called semilunar because of their
half-moon shape, a structure that
prevents the backflow of blood form
the aorta and pulmonary artery into
the ventricles.
Valvular Pathophysiology
• Mitral/Tricuspid stenosis-when these values
are unable to open completely or have a
congenitally small opening there is an
obstruction to the free flow of blood
• Competent- a properly functioning valve
• Regurgitant/Insufficient-leaky or stenosed
valve
THE END
OF
CHAPTER 3
Tilkian, Ara MD Understanding Heart Sounds and Murmurs,
Fourth Edition, W.B. Sunders Company. 2002, pp. 26-33.