Cardiac Cycle Lecture Notes PDF

CARDIAC CYCLE Dr. Gowri G.K Faculty of Medicine, Nursing & Health Science  LECTURE CONTENT INTRODUCTION PHASES OF CARDIAC CYCLE HEART SOUND LISTENING TO THE HEART SOUNDS  INTRODUCTION Cardiac cycle= cardiac events that occur from...

CARDIAC CYCLE Dr. Gowri G.K Faculty of Medicine, Nursing & Health Science  LECTURE CONTENT INTRODUCTION PHASES OF CARDIAC CYCLE HEART SOUND LISTENING TO THE HEART SOUNDS  INTRODUCTION Cardiac cycle= cardiac events that occur from the beginning of one heart beat to the beginning of next Involves both sides of the heart Duration of 1 cycle= 0.8 seconds, Heart rate= of 72 beats per minute Electrocardiogram (ECG) is used as event marker Opening and closing of valves causes physiological heart sounds Diastole= The phase of the cardiac cycle when the heart muscle relaxes to allow the chambers to fill with blood  Atrial Diastole oRelaxation of Atria oAtria fills with blood from large veins Ventricular Diastole oRelaxation of Ventricle oVentricle fills with blood from the atria Systole= The phase of the cardiac cycle when the heart muscle contracts to pump blood from chambers into arteries Atrial Systole o Contraction of Atria o Expulsion of blood from Atria into Ventricle Ventricular Systole o Contraction of Ventricle o Expulsion of blood from Ventricle to large artery Isovolumetric= unchanging volume Allows time for atria to contract and complete filling of ventricle  Phases of Cardiac Cycle There are 7 phases of Cardiac Cycle 1. Atrial Systole 2. Isovolumetric Ventricular Contraction 3. Rapid Ventricular Ejection 4. Reduced Ventricular Ejection 5. Isovolumetric Ventricular Relaxation 6. Rapid Ventricular Filling 7. Reduced Ventricular Filling 1. Atrial Systole:  Atrial contraction  Filling of left ventricle via mitral valve  Coincides with P wave on ECG  Coincides with fourth heart sound (S4) but not audible in normal state 2. Isovolumetric ventricular contraction  Left ventricular contraction  Closure of mitral valve  Volume remains the same  Coincides with QRS complex on ECG  Coincides with first heart sound (S1) (mitral valve closure) 3. Rapid Ventricular Ejection  Rapid blood ejection from left ventricle into aorta  Opening of aortic valve  End of phase coincides with end of ST segment on ECG 4. Reduced Ventricular Ejection  Reduced rate of blood ejection from ventricle to aorta  Coincides with beginning of T wave on ECG 5. Isovolumetric Ventricular Relaxation  Relaxation of ventricles  Aortic valve closure  Coincides with end of T wave on ECG  Coincides with 2nd heart sound (S2) (aortic valve closure) 6. Rapid Ventricular Filling  Rapid filling of blood from atrium to left ventricle  Opening of mitral valve  Coincides with third heart sound (S3)- audible in children, inaudible in adults 7. Reduced Ventricular Filling (Diastasis)  Slower rate of ventricular filling  Longest phase of the cardiac cycle  HEART SOUNDS Heart Sounds are caused by blood flowing through heart chambers as the valves open and close Vibration of the valves cause audible sounds The sound waves travel all the way to the surface of the skin and can be auscultated with a stethoscope  First Heart Sound Produced during the isovolumetric contraction phase It resembles the spoken word “lub” of “lub-dub” Consist of M1 & T1 S1 corresponds to palpation of carotid pulse It is normally a single sound Causes: Sudden closure of AV valves (mitral & tricuspid valves) Second Heart Sound Produced during isovolumetric ventricular relaxation phase It resembles the spoken word “dub” of “lub-dub” This "dub" sound is typically heard as a sharp snap because the semilunar valves tend to close much more rapidly than the AV valves (shorter and snappier then S1) S2 has a higher pitch and loudness compared to S1 S2 is generally louder than S1 in most areas. Consists of A2 and P2 Causes: Sudden closure of Semilunar valves (aortic & pulmonary valves) Splitting of Second Heart Sound In younger patients, you should be able to detect physiologic splitting of S2 This means that S2 is made up of 2 components, aortic (A2) and pulmonary (P2) valve closure Variations during inspiration and expiration: On inspiration, venous return to the heart is augmented and pulmonary valve closure is delayed, allowing you to hear first A2 and then P2 On expiration, the two sounds occur closer together and are detected as a single S2  Ask the patient to take a deep breath and hold it, giving you a bit more time to identify this phenomenon. The two components of S1 (mitral and tricuspid valve closure) occur so close together that splitting is not appreciated  LISTENING TO THE HEART SOUNDS Listening to heart sounds is one of the important components of cardiovascular examination A CVS examination should consist of: General examination Inspection Palpation Auscultation The Stethoscope Bell auscultation of low frequency sounds (S3 & S4) place on chest lightly – just firmly enough to block out room noise. Diaphragm auscultation of high frequency sounds (S1 & S2);and high pitched murmurs. dampens out low frequency sounds and unmasks the high  General Principles Need quiet environment Warm stethoscope Choose a sequence and stick with it Listen first for rate and rhythm Listen only to one sound at a time Listen to S1 at each auscultatory location, then S2 Listen for normal heart sounds first, then abnormal Typically sounds coming from the left side of the heart are louder then the right Valves on the left side of the heart normally close just before those on the right Where to Listen to Heart Sounds THANK YOU FOR YOUR ATTENTION 