Cardiac Cycle PDF

Cardiac Click to edit cycle Master title style I Edit Master text styles Second level Third level Fourth level Fifth level Presented by: Dr. Ien...

Cardiac Click to edit cycle Master title style I Edit Master text styles Second level Third level Fourth level Fifth level Presented by: Dr. Ienass Mohamed Bahaa ByClick to edit the end of theMaster lecturetitle style be able to: you should 1- Edit Master Define cardiac text styles cycle. 2- Second level effect of tachycardia on the duration of the cardiac Describe cycle. Third level Fourth level 3- Enumerate different phases of the cardiac cycle. Fifth level 4- Enumerate different event changes in each phase of the cycle. 5- Describe event changes in every phase of the cycle.  Click to edit Cardiac cycle Master title style Edit Master text styles Second level Definition: Third level Fourth level The cardiac cycle is the mechanical Fifth level response of the heart in one beat. It is a certain sequence of events occurring as a result of electric activation.  The mechanical changes during each cardiac Click cycle to edit involve volumeMaster title changes and style pressure changes in different chambers of the heart, as well as, pressure Edit Master and flow changes in big text styles arteries and veins Second level connected to the heart. Third level Fourth level Fifth level  Also, Click to there edit are Master changes title in the positionstyle of the 4 valves being closed or open. These changes occur in parallel in both Edit Master text styles right and left sides of the heart. Second level Third level Fourth level Fifth level Cardiac Click cycle to edit Master title style In Edit Master each text styles cardiac cycle, a period of Second level contraction (systole) alternates with a Third level period of relaxation (diastole). Fourth level The Fifth level of proper function systole is ejection i.e. emptying of blood from each ventricle into the respective big artery. The proper function of diastole is filling of each ventricle from the respective atrium and big veins. Cardiac cycle Click to edit Master title style In each cycle, the ventricles act as compression-suction pumps, and belong to Edit Master text styles the high Second level pressure system during systole Third level Fourth level (actually the highest) and so, they can eject Fifth level blood into the high pressure arteries. Then switched to the low pressure system during diastole (actually the lowest) and so, they can be filled with blood from the low pressure atria. Remember Click to edit that:Master title style Edit Master text styles Second The atria are level not pressure pumps but are volume pumps. Third level Atrial systole represents Fourth level an aid to filling of ventricles during ventricular diastole. Fifth level Duration Click to of edit Cardiac Mastercycle: title style Edit Master text styles Second level Cardiac cycle duration is 0.8 sec at a heart rate of 75 bpm. Third level The diastole Fourth occupies level 2/3 of the cycle i.e 0.53 sec while the systole Fifth level occupies only 1/3 i.e. 0.27 sec. Click to edit Duration Master cycle: of Cardiac title style Edit Acceleration Master text of the heart will decease the duration of the whole cycle as styles well as thelevel Second duration of systole and diastole but more decrease in diastole than inThird the level systole. Example: atFourth level rate of 200 bpm the whole cycle duration is 0.3 sec of heart Fifth level which diastole occupies 0.15 sec i.e. 1/2 of the cardiac cycle duration and systole occupies 0.15 sec i.e.1/2 of the cardiac cycle duration.  Click to edit Master title Phases of cardiac cycle: style Edit Master text styles Cardiac cycle consists Second level of 8 phases: 1. Atrial systole. Third level 2. Isovolumetric contraction. Fourth level Fifth level 3. Rapid ejection. 4. Reduced ejection. 5. Protodiastole. 6. Isovolumetric relaxation. 7. Rapid filling. 8. Reduced filling.  Click to edit Cardiac cycle Master title style Edit Master text styles In each Second phase, levelthere are event changes in: Third level 1- Atrial pressure Fourth level 2- Ventricular volume Fifth level 3- Ventricular pressure 4- Aortic pressure 5- Heart valves 6- Heart sounds 7- ECG  Click to 1-Atrial edit Master title style systole Edit Master Duration: 0.1 sec text styles Atrial systole Secondoccurs level as the first phase of a new cardiac cycle, Third level while the ventricles are still in the last phase of diastole of the Fourth level previous cardiac cycle, and is completed before the ventricles Fifth level begin to contract. Atrial systole represents the third phase of ventricular filling, and is responsible for about 20-30% of ventricular filling. The role of atrial systole in ventricular filling becomes more important in case of increased heart rate.  Events during Atrial Systole Click to edit Master title style o Atrial pressure: is increased and is responsible for the "a" wave in atrial pressure curve and in the Jugular Edit Master text styles Venous Pulse (JVP). o Ventricular volume: Secondislevel increased and reaches its maximum, the end diastolic volume (EDV: ~130 ml). Third level o Ventricular pressure: is increased slightly. Fourth level o Aortic pressure: is decreased, as level Fifth semilunar valves are still closed with no blood ejection, while there is continuous escape of blood to the periphery. o Valves: A-V valves are still open and semilunar valves are closed. o Heart sounds: atrial systole is responsible for the 4th heart sound which is not audible normally. o ECG: P wave begins before atrial systole by 0.02 sec. Click to editSystole Ventricular Master title style Edit Master text styles Second During level ventricular systole there are 3 phases: Third level 1. Isovolumetric Fourth levelcontraction Fifth level 2. Rapid ejection 3. Reduced ejection Ventricular systole Click to edit Master title style 1-Isovolumetric (Isometric) Contraction Edit Master Phase: (Duration 0.04 sec) text styles Second level It represents the interval between closure of the A-V valves Third level and opening of the semilunar Fourth level valves. Fifth level During which both types of valves are closed. The skeleton of the heart is fixed with no change in the length of its fibers (= no change in ventricular volume). There is neither filling nor ejection and there is no external work.  Click to editcontraction Isovolumetric Master title style Edit Master During text styles the isovolumetric contraction, the ventricles Second contract as level closed cavities (= isometric), and so the Third level ventricular wall tension is maximally increased, leading to Fourth level marked rise of the Fifth intraventricular level pressure. And so is responsible for switching of the ventricular pressure from the low pressure system to the high pressure system. Events during Isovolumetric Contraction: 1. Click to edit Master title style Atrial pressure: is slightly increased due to bulging of the A-V valves free surface into the atrial cavity causing "c" wave in atrial pressure curve and in JVP. 2. Ventricular volume: is essentially unchanged (= isovolumetric), and is the Edit Master text styles same volume at the end of atrial systole. i.e. no blood entering or leaving Second the ventricles (EDV: ~130 ml). level 3. Thirdis level Ventricular pressure: increased at a very high rate approaching the pressure in the aorta and pulmonary arteries. Fourth level 4. Aortic pressure: is still decreasing, as semilunar valves are still closed with Fifth level no blood ejection, while there is continuous escape of blood to the periphery. 5. Valves: both A-V valves and semilunar valves are closed. 6. Heart sounds: The first heart sound (S1) occurs during this phase as a result of closure of A-V valves (valvular component) as well as ventricular muscle contraction (ventricular component). 7. ECG: Q wave starts before the beginning of this Phase by 0.02 sec, and the rest of QRS complex occurs during it.  After isovolumetric contraction phase, rapid Click and to ejection reduced edit Master title style phases follows: 2-Rapid Ejection Phase: (Duration 0.16 sec) Edit Master Ejection text styles is the proper function of systole. Second level This phase begins by opening of both Third level semilunar valves, Fourth level Fifth level It represents the early part of ejection period during which most of the blood (~70%) is ejected into aorta and pulmonary artery. Events during Rapid Ejection Phase: Click to edit Master title style Atrial pressure: is decreased due to shortening of ventricular muscle, pulling downwards upon the A-V fibrous skeleton of the heart, increasing the space of atrial cavity. This is responsible for the negative wave in atrial pressure wave and in JVP (X descent). Edit Master text styles Ventricular volume: is markedly decreased (by ~70%), due to maximal Second level ejection of blood from the ventricular cavity into the big arteries. Third Ventricular pressure: level continue contracting, increasing the ventricles the intraventricular pressure to reach its maximum value which is equal Fourth level to the highest pressure in the aorta and pulmonary arteries (systolic blood pressure: SBP: ~ 120 mmHg inFifth level LV and 25mmHg in RV). Aortic pressure: is rapidly increasing in parallel to LV pressure, till it reaches its maximum value (SBP: ~ 120 mmHg). During this phase, the volume of blood leaving the ventricle and entering the first segment of aorta is much larger than the volume of blood escaping from the aorta to the periphery. Valves: A-V valves are closed and semilunar valves are open. Heart sounds: The first heart sound (S1) is still heard during this phase as a result of the vascular component of S1, due to rush of blood in aorta and pulmonary artery. ECG: S-T segment and beginning of the T wave. 3-Reduced Ejection Phase: (Duration Click to edit Master title style 0.1 sec) This phase represents continuation of the Edit Master text styles rapid ejection phase. Second level Third level Fourth level during which blood continues to leave Fifth level the ventricle to be ejected into the aorta and pulmonary arteries. Events during Reduced Ejection Phase: Click to edit Master title style Atrial pressure: is increasing slowly and progressively, due to return of the venous blood to the atria while the A-V valves are closed. Edit Master Ventricular volume: text styles by ~ 30 % due to is decreased slower ejection of blood through the open A-V Second valves into leveland pulmonary artery. At the the aorta end of this phase, Third the levelventricular volume reaches its minimal volume, the end systolic volume (ESV: ~ 50 ml). Fourth level Fifth level Ventricular pressure: starts to decrease, together with the aortic pressure till it becomes just less than aortic pressure at the end of this phase. Aortic pressure: starts to decrease because the blood volume escaping to the periphery is larger than the blood volume ejected by the ventricle into the aorta. Valves: A-V valves are closed and semilunar valves are still open. Heart sounds: during this phase, no heart sounds are heard. ECG: first half and top of T wave. Click to edit Master title style Edit Master text styles Second level Third level Fourth level Fifth level