Dr. QURBA KIRAN

DPT

Physiology

PRESENTATION

Cardaic cycle

Cardaic cycleCARDAIC CYCLE

Cardiac Cycle

• The cardiac events that occur from beginning of one heart beat to the beginning of the next are called the cardiac cycle.

• Initiated by spontaneous generation of AP in SA node.

• Atria act as PRIMER PUMPS for ventricles & ventricles provide major source of power for moving the blood through the vascular system.

Cardiac Cycle

• Cardiac cycle refers to all events associated with blood flow through the heart– Systole – contraction of heart muscle– Diastole – relaxation of heart muscle

ATRIAL SYSTOLE

the end of diastole

Atrial Systole Blood normally flows continually

from great veins into arteria 75% flows directly the atria into ventricle before the arteria contracts. 25% of filling of ventricles – arterial

contraction Arterial contraction is complete

before the ventricle begins to contract.

ISOVOLUMETRIC CONTRACTIONPressures & Volumes

• The AV valves close when the pressure in the ventricles (red) exceeds the pressure in the atria (yellow).

• As the ventricles contract isovolumetrically -- their volume does not change (white) -- the pressure inside increases, approaching the pressure in the aorta and pulmonary arteries (green).

Atrial SystoleECG

• p wave – atrial depolarization• impulse from SA node results in depolarization &

contraction of atria ( Rt before Lt )• PR segment – isoelectric line as depolarization

proceeds to AV node.• This brief pause before contraction allows the

ventricles to fill completely with blood.

Atrial SystoleHeart Sounds

• S4 - end of arterial emptying after arterial contraction. • rapid emptying of atrium into non compliant ventricle• physiological : children , young adults • pathological : angina, MI,

Beginning of Ven.SystoleIsovolumetric Contraction

• The atrioventricular (AV) valves close at the beginning of this phase

• Mechanically, ventricular systole is defined as the interval between the closing of the AV valves and the opening of the semilunar valves (aortic and pulmonary valves).

• Electrically, ventricular systole is defined as the interval between the QRS complex and the end of the T wave (the Q-T interval).

Isovolumetric ContractionPressure & Volume Changes

• The AV valves close when the pressure in the ventricles (red) exceeds the pressure in the atria (yellow).

• As the ventricles contract isovolumetrically -- their volume does not change (white) -- the pressure inside increases, approaching the pressure in the aorta and pulmonary arteries (green).

Isovolumetric ContractionECG

• The QRS complex is due to ventricular depolarization, and it marks the beginning of ventricular systole.

Isovolumetric ContractionHeart Sounds

• S1 is d/t closure of AV Valves .

Ejection

• The Semilunar valves ( aortic , pulmonary ) open at the beginning of this phase.

• This at first 1/3 rapid ejection (70%) & remaining 2/3 slow ejection.(30%)

ECG & Heart Sounds• In rapid ejection part of the

ejection phase there no specific ecg changes / heartsounds heard.

Slow Ejection

• At the end of ejection, the semilunar valves close.

ECG & Heart Sounds

• T wave – slightly before the end of ventricular contraction

• it is d/t ventricular repolarization

• heart sounds : none

Rapid Inflow ( Rapid Ven. Filling)

• Once AV valves are open the blood that has accumulated in atria flows into the ventricle

Volume changes

• Ventricular volume increases rapidly as blood flows from the atria into the ventricles.

Rapid Inflow ( Rapid Ven. Filling)ECG & Heart Sounds

• ECG : no deflections• Heart sounds : S3 is heard –

Initial passive filling of ventricles

• physiological : children, atheletes, pregnancy

• pathological : High output states, ASD,VSD

REDUCED VENTRICULAR FILLING (Diastasis)

Diastasis

• remaining blood which has accumulated in atria slowly flows into the ventricle.

DiastasisVolume changes

• Ventricular volume increases more slowly now. The ventricles continue to fill with blood until they are nearly full.

ECG & Heart Sounds

• ECG : no deflections• Heart Sounds : none

COMPLETE PICTURE OF CARDAIC CYCLE

Phases of the Cardiac Cycle

Figure 18.20