Cardiac Cycle PDF

Cardiac cycle Dr. Ghada Elgarawany Assistant professor of Medical Physiology www.gmu.ac.ae 1. Define the cardiac cycle and describe its phases. 2. Describe the ventricular pressure changes during cardiac cycle 3. Describe the aortic pressure changes during cardiac cycle COLLEGE OF MEDICINE Cardiac c...

Cardiac cycle Dr. Ghada Elgarawany Assistant professor of Medical Physiology www.gmu.ac.ae 1. Define the cardiac cycle and describe its phases. 2. Describe the ventricular pressure changes during cardiac cycle 3. Describe the aortic pressure changes during cardiac cycle COLLEGE OF MEDICINE Cardiac cycle Definition: cardiac events that occur during heartbeat (systole & diastole) Systole = contraction * Diastole = relaxation Duration : 0.8 sec (when HR=75) ( Atrial systole = 0.1 & Atrial diastole = 0.7) (Ventricular systole = 0.3 & ventricular diastole = 0.5) Whole heart systole is absent Whole heart diastole is 0.4 sec. Phases of Cardiac cycle Atrial systole 1. Atrial systolic phase Ventricular diastole 2. Isometric contraction phase 3. Rapid (Maximal) ejection phase Atrial diastole 4. Slow (Reduced) ejection phase 5. Isometric relaxation phase 6. Rapid (Maximal) filling phase 7. Slow (Reduced) filling phase We monitor during cardiac cycle 1. Atrial pressure 2. Ventricular pressure 3. Aortic & pulmonary pressure 4. Ventricular volume 5. Heart sounds 6. ECG Ventricular systole Ventricular diastole 1- Atrial systolic phase Duration: 0.1 sec Atrial.Pressure: increase then decrease Ventricular. Pressure: increase then decrease Ventricular. Volume: increase then decrease Valves : AV valves open & semilunar closed Aortic.Pressure : decrease gradually Heart sound: 4th sound ECG: P wave , Q & R wave 2. Isometric (isovolumic) contraction phase Duration: 0.05 sec (ventricles contract) Ventricular. Pressure: rapid increase to 80mmHg Atrial.Pressure: slightly, sharp increase Ventricular. Volume: NO change Valves : AV valves suddenly closes & semilunar closed Aortic.Pressure : decrease gradually Heart sound: 1st sound ECG: S wave Isometric (isovolumic) contraction phase 3. Rapid ( Maximal) ejection phase Duration: 0.15 sec (ventricles eject blood) Ventricular. Pressure: Markedly increase > Aortic P Atrial.Pressure: sharp decrease Ventricular. Volume: decrease rapidly Valves : semilunar open & AV valve still closed Aortic.Pressure : Markedly increase Heart sound: 1st sound continues ECG: S-T segment 4. Slow ( Reduced) ejection phase Duration: 0.1 sec (ventricles continue to eject blood) Ventricular Pressure: slightly decrease Atrial Pressure: gradually increase Ventricular Volume: decrease Valves : semilunar still open & AV valve still closed Aortic Pressure : slightly decrease Heart sound: no sound ECG: T wave Ejection phase 5. Isometric (isovolumic) relaxation phase Duration: 0.06 sec, ventricular relaxation (diastole) Ventricular Pressure: Rapidly decrease (0 mmHg) Atrial Pressure: gradual increase Ventricular Volume: NO change Valves : semilunar close & AV valve closed Aortic Pressure : sharp decrease then increase (Diacrotic notch) Heart sound: 2nd sound ECG: end of T wave Isometric (isovolumic) relaxation phase 6. Rapid (Maximal) filling phase Duration: 0.1 sec, ventricular diastole after opening of AV valve Atrial Pressure: more than Ventricular pressure. Ventricular Pressure: around (0 mmHg) Ventricular Volume: marked increase Valves : AV valve open & semilunar still close Aortic Pressure : gradual decrease Heart sound: end of 2nd sound & 3rd sound ECG: U wave may be present 7. Slow (Reduced) filling phase Duration: 0.2 sec, ventricular diastole Atrial Pressure: around (0 mmHg) Ventricular Pressure: around (0 mmHg) Ventricular Volume: gradual or slow increase Valves : AV valve open & semilunar still close Aortic Pressure : gradual decrease Heart sound: no sound ECG: start of P wave Filling phase Ventricular pressure changes during cardiac cycle Aortic pressure changes during cardiac cycle State of valves during cardiac cycle A- V valves : open in atrial systole and rapid and slow filling phases. Semilunar valves : open in rapid and slow ejection. All valves are closed in: isometric contraction and relaxation phases AV & semilunar valves open together (True or false)????? Review Questions Aortic stenosis is a condition in which the aortic valve becomes calcified and stiff. The left ventricle has to generate more pressure to open the stiffer valve. When the valve opens, the increased ventricular pressure causes a jet of blood that radiates to the carotid arteries, which can be heard on auscultation. During which phase of the cardiac cycle are you most likely to hear the carotid radiation? A. Atrial systole B. Isovolumetric contraction C. Rapid ejection D. Rapid ventricular filling E. Reduced ejection https://exchange.scholarrx.com/brick/cardiac-cycle Summary 1. Define the cardiac cycle and list its phases. 2. Describe the ventricular pressure changes during cardiac cycle 3. Describe the aortic pressure changes during cardiac cycle