1Prof. Dr. Muhammad Abdul Azeem, UMDC

Prof. Dr. Muhammad Abdul Azeem,United Medical & Dental College, Karachi, Pakistan

Definition of Cardiac Cycle

Events from the beginning of oneheart beat to the beginning of the nextbeat is called cardiac cycle.

2Prof. Dr. Muhammad Abdul Azeem, UMDC

• Before the detailed study of Cardiac Cycle. It isbetter to understand the relation betweenelectrical and mechanical activity that occursduring cardiac cycle.

• Electrical activity: Represents generation andpropagation of electrical current from pacemakertowards all parts of heart.

• Mechanical activity: Represents activation ofcardiac muscle fibers by electrical activity togenerate force for pumping of blood intocirculation.

3Prof. Dr. Muhammad Abdul Azeem, UMDC

Relation of Cardiac Muscle Contraction with Its Action Potential

• Cardiac muscle begins to contract a few mS after the action potential begins.

• They continues to contract until a few mSafter the action potential ends.

• Therefore, duration of their contraction is a function of duration of their action potential, 0.2 second in atrial muscle and 0.3 second in ventricular muscle.

4Prof. Dr. Muhammad Abdul Azeem, UMDC

Cardiac Cycle

5Prof. Dr. Muhammad Abdul Azeem, UMDC

CardiacCycle

6Prof. Dr. Muhammad Abdul Azeem, UMDC

Atrial Pressure Curve

• a wave = atrial contraction as primer pump.– Right atrial pressure = 4 to 6 mm Hg .– Left atrial pressure = 7 to 8 mm Hg.

• c wave = ventricles begin to contract; – bulging of the A-V valves backward toward the atria.

• v wave = end of ventricular contraction; – slow flow of blood into the atria from the veins.

• v wave disappear when blood flow rapidly into the ventricles.

7Prof. Dr. Muhammad Abdul Azeem, UMDC

Ventricular Pressure Curve in Cardiac Cycle

8Prof. Dr. Muhammad Abdul Azeem, UMDC

Aortic Pressure Curve • Isovolumetric Contraction of left ventricle.

• Increase in ventricular pressure

• Opening of Aortic Valve.

• Contraction of Ventricle.

• Entry of blood in aorta, pressure 120mmHg.

• Aortic valve closes. Appearance of Dicortic notch.

• Incisura appears due to Backward flow

Aortic ValveOpen

Ejection waveSystolic Phase

Reflected waveDiastolic Phase

Incisura

Dicortic NotchAortic Valve Closes

9Prof. Dr. Muhammad Abdul Azeem, UMDC

Systolic intervals (0.27 Sec)

Isometric Contraction (Isovolumic; IVC) 0.05 (Sec)

Ejection Period 0.22 (Sec)

Diastolic intervals (0.53 Sec)

Proto-diastole (Reduced Ejection) 0.04 Sec

Isometric Relaxation (Isovolumic; IVR) 0.08 Sec

Rapid Filling 0.11 Sec

Slow Filling 0.19 Sec

Atrial Systole 0.11 Sec

http://www.slideshare.net/gopikrishnarayidi/cardiac-cycle-ppt-2 Dr. Gopi Krishna

TOTAL TIME OF CARDIAC CYCLE INCLUDING SEVEN INTERVALS (0.8 Seconds)

10Prof. Dr. Muhammad Abdul Azeem, UMDC

End-Diastolic Volume, End-Systolic Volume, and Stroke Volume Output

• During diastole, blood volume increases in each ventricle to about 110 to 120 ml. This volume is called end-diastolic volume.

• Ventricular emptying during systole decreases 70 ml from this volume. It is called stroke volume output.

• The remaining volume in each ventricle is 40 to 50 ml (end-systolic volume).

11Prof. Dr. Muhammad Abdul Azeem, UMDC

VENTRICULAR VOLUME CURVE

12Prof. Dr. Muhammad Abdul Azeem, UMDC

Ejection Fraction & Ventricular Volume

• The fraction of the end-diastolic volume that is ejected is called the ejection fraction (about 60 percent of the total blood).

• During strong contraction of heart, the end-systolic volume is reduced to only 10 to 20 ml.

• Conversely, when large amounts of blood flow into the ventricles during diastole, the ventricular end-diastolic volumes can become as great as 150 to 180 ml in the healthy heart.

13Prof. Dr. Muhammad Abdul Azeem, UMDC

Left Ventricular Rotation During Systole In Cardiac Cycle:

• Beneficial Effects of LV Rotation

–Maximizes intra-cavity pressures.

–Increases stroke volume.

–Minimizes myocardial oxygen demand.

14Prof. Dr. Muhammad Abdul Azeem, UMDC

Relation of ECG with Cardiac Cycle

• P wave appears before atrial systole.

• QRS complex appear before Isovolumetric contraction of ventricle.

• T wave appears before iso-volumetric relaxation and ends before actual relaxation of ventricles.

15Prof. Dr. Muhammad Abdul Azeem, UMDC

Recent Research (2013)Detection of Heart Blocks by Cardiac Cycle Extraction

using Time- Scale Analysishttp://ijetsp.info/article/IJETSPV1I302.pdf

OVERLAPS OF SINGULAR CC IN NORMAL HEART (Regular Rhythm)

OVERLAPS OF SINGULAR CC INARHYTHMIC HEART WITH BLOCK

(Irregular Rhythm)

All the cardiac cycles taken individually from ECG recordings are overlapped to detect abnormalities in the heart. PR interval of a normal ECG has a maximum duration of 0.2 seconds, a PR interval of 0.3 second is considered as worst case value. Similarly, a QT interval value of 0.44 seconds is considered.

16Prof. Dr. Muhammad Abdul Azeem, UMDC

Heart Sounds & Cardiac CyclePhonocardiogram

• Opening of valve does not produce any sound because it is a slow process.

• During closure of valves, their vanes and the surrounding fluids vibrate under the influence of sudden pressure changes, giving off sound that travels in all directions in the chest.

17Prof. Dr. Muhammad Abdul Azeem, UMDC

VALVES

POSITION ASPER

INTERCOSTAL SPACE

POSITION AS PER STERNAL

BORDER

Aortic valve (to aorta)

right second intercostal space

upper right sternal border

Pulmonary valve (to pulmonary trunk)

left second intercostal space

upper left sternal border

Erb's pointLeft third intercostal space

left sternal border

Tricuspid valve (to right ventricle)

left fourth, fifth intercostal spaces

lower left sternal border

Mitral valve (to left ventricle)

left fifth intercostal space

left midclavicularline

19Prof. Dr. Muhammad Abdul Azeem, UMDC

SOUNDS FOUND IN

COMPONENTS EVENT OF CARDIAC CYCLE

CONDITIONS

First heart sound (S1 )

Normal Persons

two component sound, M1, T1.

ventricles contract with closure of A-V valves

The vibration is low in pitch and relatively long-lasting.

Second heart sound (S2 )

Normal Persons

2 components, A2 and P2. When semilunar valves close rapidly at the end of systole.

a rapid snap heard.

Third heart Sound (S3)

Children & young adults Early diastolic filling of Ventricles

Rare extra heart sound occurs soon after normal S1 and S2.

Fourth heart Sound (S4)

Normal Adults Late diastolic filling of Ventricle

S3 & S4 Diseased States; heart failure & cardiac diseases

Gallop Sound

S4 prior to S1, where atrial contraction does not precede ventricular contraction

Pathological Condition Forceful atrial contraction

Absent in Fibrillation (rapid & irregular beating),

However, in left bundle branch block (LBBB) allow the P2 sound to be heard before the A2 sound duringexpiration. With LBBB, inhalation brings A2 and P2 closer together where they cannot be audiblydistinguished.

Referred from

• Text book of physiology by Guyton

• Physiology by Berne & Leve

• Clinical Physiology by Ashish Banerjee

• Internet Resources

• Updated 2015