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MEDiscuss • Cardiovascular diseases • Cardiac cycle - concept, origin of heart sounds, murmurs and other sounds


  1. #41
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    Cardiac Cycle, Heart Sounds and Murmurs

    [FONT=Times New Roman]The cardiac cycle has four phases [/FONT]
    [FONT=Times New Roman][/FONT]
    [FONT=Times New Roman] I Ventricular filling[/FONT]
    [FONT=Times New Roman] II Isometric contraction[/FONT]
    [FONT=Times New Roman] III Ejection[/FONT]
    [FONT=Times New Roman] IV Isovolumetric relaxation[/FONT]
    [FONT=Times New Roman][/FONT]
    [FONT=Times New Roman][/FONT]
    • [FONT=Times New Roman]Ventricular filling[/FONT]
    [FONT=Times New Roman][/FONT]
    [FONT=Times New Roman]Ventricular diastole lasts for nearly two thirds of the cycle at rest. There is an initial phase of rapid filling lasting aprrox. 0.15 sec. As ventricular volume increase with blood the ventricular pressure is actually decreasing due to the elastic recoil of the heart. As the ventricle reaches its natural volume the rate of filling decreases and further filling requires further distension of the ventricles. In the final third of the filling phase, the atria contract and force some blood into the ventricles. The volume of blood in the ventricles at the end of diastole is the approx. 120 ml and is called end diastolic pressure.[/FONT]
    [FONT=Times New Roman][/FONT]
    [FONT=Times New Roman][/FONT]
    [FONT=Times New Roman][/FONT]
    • [FONT=Times New Roman]Isovolumetric Contracture[/FONT]
    [FONT=Times New Roman][/FONT]
    [FONT=Times New Roman]Ventricular systole lasts 0.35s and is divided into a brief isovolumetric phase and a longer ejection phase. As soon as the ventricular pressure rises above the atrial pressure, the atrioventricular valves are forced shut. The ventricle is now a closed chamber.[/FONT]
    [FONT=Times New Roman][/FONT]
    • [FONT=Times New Roman]Ejection[/FONT]
    [FONT=Times New Roman][/FONT]
    [FONT=Times New Roman]When ventricular pressure rises above that of the arterial circulation the outflow valves are opened and ejection begins. Three quarters of the stroke volume is ejected in the first half of the ejection phase. As systole weakens and the rate of ejection slows down, the rate at which blood flows away through the arterial system begins to exceed the ejection rate, so pressure begins to fall. Valve closure creates a brief pressure rise in arterial pressure trace called the dicrotic wave. The ventricles do not empty completely but only about by two thirds. [/FONT]
    [FONT=Times New Roman][/FONT]
    • [FONT=Times New Roman]Isovolumetric relaxation[/FONT]
    [FONT=Times New Roman][/FONT]
    [FONT=Times New Roman][/FONT]
    [FONT=Times New Roman]With closure of the aortic and pulmonary valves, each ventricle once again becomes a closed chamber. Ventricular pressure falls very rapidly owing to the mechanical recoil of collagen fibres within the myocardium. When ventricular pressure has fallen just below atrial pressure, the atrioventricular valves open and blood flows in from the atria, which have been refilling during ventricular systole.[/FONT]
    [FONT=Times New Roman][/FONT]
    [FONT=Times New Roman][/FONT]
    [FONT=Times New Roman][/FONT]
    [FONT=Times New Roman]THIRD HEART SOUND[/FONT]
    [FONT=Times New Roman][/FONT]
    [FONT=Times New Roman] Common in young people and is caused by the rush of blood into the relaxing ventricles during early diastole.[/FONT]
    [FONT=Times New Roman][/FONT]
    [FONT=Times New Roman][/FONT]
    [FONT=Times New Roman]FOURTH HEART SOUND[/FONT]
    [FONT=Times New Roman][/FONT]
    [FONT=Times New Roman] Occurs just before the first and is caused by atrial systole[/FONT]
    [FONT=Times New Roman][/FONT]
    [FONT=Times New Roman][/FONT]
    [FONT=Times New Roman][/FONT]
    [FONT=Times New Roman] MURMURS[/FONT]

    [FONT=Times New Roman]There are two fundamental classes of valvular abnormality, incompetence and stenos is. Incompetence is failure of the valves to close tightly, thus allowing a regurgitation of blood. Stenosis is the narrowing of the valve. A high pressure gradient is required to force blood through a stenosed valve. In aortic stenosis ventricular systole pressure is raised, increasing the work of the ventricle, while at the same time aortic pressure is reduced. [/FONT]
    [FONT=Times New Roman] With either abnormality, blood passes through the valve in a turbulent jet, setting a high frequency vibration which is heard as a murmur. There are eight basic murmurs of valvular origin. For example, in mitral valve incompetence there is regurgitation into the left atrium, producing a murmur throughout systole(pansystolic) that sounds the loudest over the mitral auscultation area. The heart sound may then be represented as ‘lu-shshshsh-tupp’. [/FONT]
    [FONT=Times New Roman][/FONT]

  2. #42
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    im a last minute person~~


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    Concept, Origin of Heart Sounds, Murmurs and Other sounds.

    [FONT=&quot]Name: Semantha Chia Peck Sin[/FONT]
    [FONT=&quot]Roll No.: 041303015[/FONT]
    [FONT=&quot]Batch 15 (Group B2)[/FONT]

    [FONT=&quot]Heart Sounds[/FONT]
    [FONT=&quot]First Heart Sound (S1)[/FONT]
    [FONT=Wingdings]Ø[/FONT][FONT=&quot]Produced by the closure of mitral and tricuspid valve simultaneously, so heard as a single sound.[/FONT]
    [FONT=Wingdings]Ø[/FONT][FONT=&quot]Indicates the onset of ventricular systole.[/FONT]

    [FONT=&quot]Second Heart Sound (S2)[/FONT]
    [FONT=Wingdings]v[/FONT][FONT=&quot]Produced by the closure of aortic valve and pulmonary valves.[/FONT]
    [FONT=Wingdings]v[/FONT][FONT=&quot]Pulmonary valve closes later and the aortic valve closes earlier due to early rise of Left ventricular pressure and early activation of the left ventricle.[/FONT]
    [FONT=Wingdings]v[/FONT][FONT=&quot]As a result, S2 is heard as 2 components, aortic and pulmonary components.[/FONT]

    [FONT=&quot]Third Heart Sound (S3)[/FONT]
    [FONT=Symbol]·[/FONT][FONT=&quot]Produced due to the rapid filling of the ventricle during early diastole leading to sudden limitation of expansion of the ventricle causing vibrations. [/FONT]
    [FONT=Symbol]·[/FONT][FONT=&quot]Characteristics: Low frequency sound, heard better with the bell of the stethoscope.[/FONT]
    [FONT=Symbol]·[/FONT][FONT=&quot]Rarely, there may be a third heart sound S3. [/FONT]
    [FONT=Symbol]·[/FONT][FONT=&quot]Also called as “Protodiastolic sound” . It is not of valvular origin, as it occurs at the beginning of diastole just after S2. [/FONT]
    [FONT=Symbol]·[/FONT][FONT=&quot]This sound occurs when the left ventricle is not very compliant, and at the beginning of diastole the rush of blood into the left ventricle causes vibration of the valve leaflets and the chordae tendinae.[/FONT]
    [FONT=Symbol]·[/FONT][FONT=&quot]The third heart sound is normal in children and young adults, but disappears before middle age. Abnormal reemergence of this sound late in life indicates a pathological state, often a sign of a failing left ventricle as in dilated congestive heart failure (CHF). This sound is called a “Protodiastolic Gallop”, a type of gallop rhythm.[/FONT]

    [FONT=&quot]Fourth Heart Sound (S4)[/FONT]
    [FONT=Wingdings]§[/FONT][FONT=&quot]Characteristics: Low frequeny sound, heard in the later part of diastole in patients with sinus rhythm. Better felt than auscultated. Disappears in patients with atrial fibrillation.[/FONT]
    [FONT=Wingdings]§[/FONT][FONT=&quot]The rare fourth heart sound (S4) is sometimes audible in healthy children, but when audible in an adult is called a “Presystolic Gallop”. [/FONT]
    [FONT=Wingdings]§[/FONT][FONT=&quot]This gallop is a sign of a pathologic state, usually a failing left ventricle.[/FONT]
    [FONT=Wingdings]§[/FONT][FONT=&quot]This sound occurs just after atrial contraction ("atrial kick") and is the sound of blood being forced into a stiff or hypertrophic left ventricle. [/FONT]
    [FONT=Wingdings]§[/FONT][FONT=&quot]The combined presence of S3 and S4 is a quadruple gallop. At rapid heart rates, S3 and S4 may merge to produce a summation gallop.[/FONT]

    [FONT=&quot]Murmurs[/FONT]
    [FONT=&quot]Genesis of Murmurs[/FONT]
    [FONT=Wingdings]v[/FONT][FONT=&quot]Murmurs are due to the vibrations produced by the turbulent flow at:-[/FONT]
    [FONT=&quot]1)[/FONT][FONT=&quot]The region of the valve[/FONT]
    [FONT=&quot]2)[/FONT][FONT=&quot]Near the valve[/FONT]
    [FONT=&quot]3)[/FONT][FONT=&quot]Abnormal communication within the heart.[/FONT]
    [FONT=Wingdings]v[/FONT][FONT=&quot]Murmurs which are produced on the right side of the heart are more prominent on inspiration.[/FONT]

    [FONT=&quot]Grades of Murmurs[/FONT]
    [FONT=&quot]Grade[/FONT]
    [FONT=&quot]Description[/FONT]
    [FONT=&quot]1[/FONT]
    [FONT=&quot]Very faint, heard only after listener has "tuned in"; may not be heard in all positions[/FONT]
    [FONT=&quot]2[/FONT]
    [FONT=&quot]Quiet, but heard immediately after placing the stethoscope on the chest.[/FONT]
    [FONT=&quot]3[/FONT]
    [FONT=&quot]Moderately loud.[/FONT]
    [FONT=&quot]4[/FONT]
    [FONT=&quot]Loud, with palpable thrill.[/FONT]
    [FONT=&quot]5[/FONT]
    [FONT=&quot]Very loud, with thrill. May be heard when stethoscope is partly off the chest.[/FONT]
    [FONT=&quot]6[/FONT]
    [FONT=&quot]Very loud, with thrill. May be heard with stethoscope entirely off the chest.[/FONT]

    [FONT=&quot]Types of Murmurs[/FONT]
    [FONT=&quot]Systolic Murmurs[/FONT]
    [FONT=Wingdings]§[/FONT][FONT=&quot]Early Systolic Murmur[/FONT]
    [FONT=Wingdings]§[/FONT][FONT=&quot]Begins with S1 and diminishes in intensity and stops well before S2.[/FONT]
    [FONT=Wingdings]§[/FONT][FONT=&quot]Eg: Acute mitral regurgitation, acute tricuspid regurgitation, ventricular septal defect.[/FONT]

    [FONT=&quot]Ejection (Mid-Systolic) Murmur[/FONT]
    [FONT=Wingdings]Ø[/FONT][FONT=&quot]Characteristics:-[/FONT]
    [FONT=&quot]o[/FONT][FONT=&quot]Commences after S1, peaks in mid-systole.[/FONT]
    [FONT=&quot]o[/FONT][FONT=&quot]Stops before S2.[/FONT]
    [FONT=&quot]o[/FONT][FONT=&quot]There will be a definite gap in between the murmur and S1 and S2.[/FONT]
    [FONT=Wingdings]Ø[/FONT][FONT=&quot]Phonocardiogram records the murmur as diamond-shaped.[/FONT]

    [FONT=&quot]Late Systolic Murmur[/FONT]
    [FONT=Wingdings]ü[/FONT][FONT=&quot]Begins well after S1 and continues up to S2.[/FONT]
    [FONT=Wingdings]ü[/FONT][FONT=&quot]Eg: Mitral valve prolapsed, papillary muscle dysfunction.[/FONT]

    [FONT=&quot]Pan (Holosystolic Murmurs)[/FONT]
    [FONT=Symbol]·[/FONT][FONT=&quot]Murmur begins with S1 ends with S2 or its components.[/FONT]
    [FONT=Symbol]·[/FONT][FONT=&quot]S1 is usually muffled, intensity of murmur is uniform thoughout the sytole.[/FONT]
    [FONT=Symbol]·[/FONT][FONT=&quot]Eg: Mitral or tricuspid regurgitation and ventricular septal defect.[/FONT]

    [FONT=&quot]Diastolic Murmurs[/FONT]
    [FONT=&quot]Early Diastolic Murmur[/FONT]
    [FONT=Wingdings]v[/FONT][FONT=&quot]Starts just after S2 and gradually decreases in intensity.[/FONT]
    [FONT=Wingdings]v[/FONT][FONT=&quot]Eg: Aortic Regurgitation, pulmonary regurgitation.[/FONT]

    [FONT=&quot]Mid-Diastolic Murmur[/FONT]
    [FONT=&quot]o[/FONT][FONT=&quot]Begins well after S2 and may persist up to the next S1.[/FONT]
    [FONT=&quot]o[/FONT][FONT=&quot]Eg: Mitral stenosis, tricuspid stenosis, Austin Flint murmur, Carey-Coombs’ murmur.[/FONT]

    [FONT=&quot]Other Murmurs[/FONT]
    [FONT=&quot]Innocent Murmurs[/FONT]
    [FONT=Wingdings]§[/FONT][FONT=&quot]Systolic murmur.[/FONT]
    [FONT=Wingdings]§[/FONT][FONT=&quot]Present in persons with normal CVS and normal carotid, brachial and femoral arteries.[/FONT]
    [FONT=Wingdings]§[/FONT][FONT=&quot]Eg: Young children (3-8 years old) – Still’s murmur, adult (more than 50 years old) – Ejection systolic murmur.[/FONT]

    [FONT=&quot]Continuous Murmurs [/FONT]
    [FONT=Wingdings]ü[/FONT][FONT=&quot]Diastolic murmur. [/FONT]
    [FONT=Wingdings]ü[/FONT][FONT=&quot]Murmur begins in the systole and continues without interruption through S2 into all or part of the diastole.[/FONT]
    [FONT=Wingdings]ü[/FONT][FONT=&quot]Eg: Patent ductus arteriosus – Gibson’s murmur, arterivenous fistula, Coronary AV fistula.[/FONT]

  4. #44
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    The Cardiac Cycle

    [FONT=&quot]Name: Semantha Chia Peck Sin[/FONT]
    [FONT=&quot]Roll No.: 041303015[/FONT]
    [FONT=&quot]Batch 15 (Group B2)[/FONT]

    [FONT=&quot]The Cardiac Cycle[/FONT]
    [FONT=&quot]Definition: The cyclical events that take place in the heart during each heart beat.[/FONT]
    [FONT=Wingdings]n[/FONT][FONT=&quot]Consists of precisely timed rhythmic electrical and mechanical events that propel blood into the systemic and pulmonary circulations.[/FONT]

    [FONT=&quot]Events:-[/FONT]
    [FONT=&quot][IMG]file:///C:/DOCUME%7E1/YULITA%7E1/LOCALS%7E1/Temp/msohtmlclip1/01/clip_image002.gif[/IMG][/FONT]

    [FONT=&quot]Phases of Cardiac Cycle[/FONT]
    [FONT=&quot]Phase 1:-[/FONT]
    [FONT=Wingdings]ü[/FONT][FONT=&quot]Atrial systole (0.1 second)[/FONT]
    [FONT=Wingdings]ü[/FONT][FONT=&quot]Atria contract (systole), ventricles are relaxed (diastole).[/FONT]
    [FONT=Wingdings]ü[/FONT][FONT=&quot]The atrioventricular (AV) valves are open; the semilunar valves are closed.[/FONT]
    [FONT=Wingdings]ü[/FONT][FONT=&quot]Blood enters to the ventricles through the AV valves.[/FONT]
    [FONT=&quot]Phase 2:-[/FONT]
    [FONT=Wingdings]ü[/FONT][FONT=&quot]Atria relax (diastole), ventricles contract (systole).[/FONT]
    [FONT=Wingdings]ü[/FONT][FONT=&quot]The AV valves close (“Lubb-Dubb”); the semilunar valves open.[/FONT]
    [FONT=Wingdings]ü[/FONT][FONT=&quot]Blood moves from the right ventricle to the pulmonary trunk through the pulmonary semilunar valve.[/FONT]
    [FONT=Wingdings]ü[/FONT][FONT=&quot]Blood moves from the left ventricle to the aorta through the airtic semilunar valve.[/FONT]

    [FONT=&quot]Phase 3:-[/FONT]
    [FONT=Wingdings]ü[/FONT][FONT=&quot]Atrial and ventricular diastole (0.4 second).[/FONT]
    [FONT=Wingdings]ü[/FONT][FONT=&quot]The AV opens, the semilunar valves closed.[/FONT]
    [FONT=Wingdings]ü[/FONT][FONT=&quot]Blood enters the right atrium through the vena cavae, and the left atrium through the pulmonary veins.[/FONT]








  5. #45
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    Cardiac Cycle

    [FONT=Times New Roman]Cardiac Cycle[/FONT]
    [FONT=Times New Roman]Definition[/FONT]
    [FONT=Times New Roman]The cyclical events that take place in the heart during each heart beat.[/FONT]
    [FONT=Times New Roman]Heart rate = Cycle operation = 75 beats/min[/FONT]

    [FONT=Times New Roman]Duration[/FONT]
    [FONT=Times New Roman]75 beats in 60sec, 1 beat = 60/75 = 0.8sec/cycle[/FONT]
    [FONT=Times New Roman]Out of 0.8sec, 0.3sec is the duration for systole while 0.5sec is for diastole[/FONT]
    [FONT=Times New Roman]If heart rate increases, cardiac cycle duration decreases (Diastole duration reduces more than systole)[/FONT]

    [FONT=Times New Roman]Ventricular Systole[/FONT]
    [FONT=Times New Roman]i. [/FONT][FONT=Times New Roman]Isovolumetric Contraction Phase[/FONT]
    [FONT=Times New Roman]Duration – 0.05sec[/FONT]
    [FONT=Times New Roman]Aortic & pulmonary valves are closed previously[/FONT]
    [FONT=Times New Roman]AV (Atrio-ventricular) valves close, producing 1st heart sound[/FONT]
    [FONT=Times New Roman]Left ventricular pressure increases till it exceeds aortic pressure (80mmHg), then aortic valve opens[/FONT]
    [FONT=Times New Roman]Right ventricular pressure increases till it exceeds pulmonary pressure (10mmHg), then pulmonary valve opens[/FONT]
    [FONT=Times New Roman]Tricuspid valve bulge into atria, producing c wave in Jugular Vein[/FONT]

    • [FONT=Times New Roman]Rapid Ejection Phase[/FONT]
    [FONT=Times New Roman]Duration – 0.10sec[/FONT]
    [FONT=Times New Roman]Initial blood flow from Left ventricular to aorta is rapid[/FONT]

    • [FONT=Times New Roman]Slow Ejection Phase[/FONT]
    [FONT=Times New Roman]Duration – 0.15sec[/FONT]
    [FONT=Times New Roman]Ejection of blood from Left Ventricle to aorta slows down[/FONT]
    [FONT=Times New Roman]Left ventricular pressure increases till 120mmHg before it decreases[/FONT]
    [FONT=Times New Roman]Right ventricular pressure increases till 25mmHg before it decreases[/FONT]
    [FONT=Times New Roman]Momentum keeps blood flowing[/FONT]
    [FONT=Times New Roman]AV valves are pulled down by ventricular muscle contraction[/FONT]
    [FONT=Times New Roman]Blood ejected per stroke at rest is 70–90mL[/FONT]
    [FONT=Times New Roman]End-diastolic ventricular volume = 130mL[/FONT]
    [FONT=Times New Roman]End-systolic ventricular volume = 50mL[/FONT]
    [FONT=Times New Roman]Ejection fraction = 65% (Index of ventricular function)[/FONT]

    [FONT=Times New Roman]Ventricular Diastole[/FONT]
    [FONT=Times New Roman]iv. [/FONT][FONT=Times New Roman]Proto Diastole[/FONT]
    [FONT=Times New Roman]Duration – 0.04sec[/FONT]
    [FONT=Times New Roman]Once ventricular muscle is fully contracted, IVP (intra-ventricular pressure) decreases further[/FONT]
    [FONT=Times New Roman]When aortic pressure exceeds that of IVP, semilunar valves close[/FONT]

    • [FONT=Times New Roman]Isovolumetric Relaxation Phase[/FONT]
    [FONT=Times New Roman]Duration – 0.10sec[/FONT]
    [FONT=Times New Roman]All valves are closed, IVP continue to decrease[/FONT]

    • [FONT=Times New Roman]Rapid Filling Phase[/FONT]
    [FONT=Times New Roman]Duration – 0.10sec[/FONT]
    [FONT=Times New Roman]70% of ventricular filling occurs in this phase[/FONT]

    • [FONT=Times New Roman]Slow Filling Phase[/FONT]
    [FONT=Times New Roman]Also known as ‘Diastasis’[/FONT]
    [FONT=Times New Roman]Duration – 0.20sec[/FONT]
    [FONT=Times New Roman]IVP decreases further[/FONT]

    [FONT=Times New Roman]viii. Filling due to atrial systole[/FONT]
    [FONT=Times New Roman]Duration – 0.10sec[/FONT]

  6. #46
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    3rd & 4th Heart Sounds

    [FONT=Times New Roman]Heart Sounds[/FONT]
    [FONT=Times New Roman]3rd Heart Sound[/FONT]
    [FONT=Times New Roman]- low pitched sound, heard best with bell of stethoscope[/FONT]
    [FONT=Times New Roman]- may be normal in younger people, but almost always pathologic if it occurs in people older than 40.[/FONT]
    [FONT=Times New Roman]- S3 occurs in early diastole, about 0.12-0.20sec after S2[/FONT]
    [FONT=Times New Roman]- S3 is sometimes referred to as a protodiastolic gallop[/FONT]
    [FONT=Times New Roman]- When originating from LV, S3 is best heard at the apex[/FONT]
    [FONT=Times New Roman]- Turning the patient into the left lateral position may augment S3 detection[/FONT]
    [FONT=Times New Roman]- When originating from RV, S3 is heard at the 4th left intercostals space adjacent to the sternum[/FONT]
    [FONT=Times New Roman]- S3 occurs at the end of early ventricular fillinf when the ventricle reaches its elasctic limit[/FONT]
    [FONT=Times New Roman]- S3 occurs when the ventricle reaches its elastic limit during early diastolic filling. S3 may be produced when normal or subnormal amounts of flow enter an already over-filled ventricle (congestive heart failure), or when very rapid filling occurs in a more normal ventricle (valvular regurgitation & high output states)[/FONT]
    [FONT=Times New Roman]- Maneuvers that increase venous return (leg elevation) tend to increase the intensity of S3 & move it closer to S2, while things that decrease cardiac filling cause the S3 to decrease in intensity & move farther away from S2 [/FONT]

    [FONT=Times New Roman]4th Heart Sound[/FONT]
    [FONT=Times New Roman]- low pitched sound, heard best with the bell of stethoscope[/FONT]
    [FONT=Times New Roman]- S4 occurs in late diastole approximately 0.04-0.12sec prior to S1.[/FONT]
    [FONT=Times New Roman]- Hence, S4 is sometimes referred to as a presystolic gallop[/FONT]
    [FONT=Times New Roman]- When originating from left heart, S4 is best heard at apex[/FONT]
    [FONT=Times New Roman]- Turning the patient to left lateral position may augment detection of a left sided S4[/FONT]
    [FONT=Times New Roman]- When originating from the right heart, S4 is best heard at the 4th left intercostal space adjacent to the sternum, or at the xiphoid[/FONT]
    [FONT=Times New Roman]- Apparently normal men over age 50 may have audible s4 gallops[/FONT]
    [FONT=Times New Roman]- An S4, when pathologic, is produced by atrial contraction against a stiff, non-compliant ventricle. Stiff ventricles are characteristic of ventricular hypertrophy, & as such are commonly seen in pulmonary or systemic hypertension. Pulmonic or aortic stenosis, & scarring secondary yo previous myocardial infarction[/FONT]
    [FONT=Times New Roman]- S4 increases in intensity & moves farther away from S1 with maneuvers that increase venous return or with increased sympathetic stimulation[/FONT]
    [FONT=Times New Roman]- S4 often decreases to the point of inaudibility with standing[/FONT]
    [FONT=Times New Roman]- S4 is dependent on atrialcontraction & is always absent in patient with atrial fibrillation[/FONT]
    [FONT=Times New Roman]- A left sided S4 can be distinguished from a split S1 by location (S1 is loudest at the LSB, while S4 is loudest at the apex) & the fact that the S4 should disappear with firm pressure on the diaphragm [/FONT]

  7. #47
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    Cardiac cycle&pathophys#rd &4th heart sound

    Cardiac cycle is the term referring to all or any of the events related to the flow of blood that occur from the beginning of one heartbeat to the beginning of the next.Every single 'beat' of the heart involves three major stages: atrial systole, ventricular systole and complete cardiac diastole.
    Atrial systole is the contraction of the heart muscle (myocardia) of the left and right atria. Normally, both atria contract at the same time. As the atria contract, the blood pressure in each atrium increases, forcing additional blood into the ventricles. The additional flow of blood is called atrial kick. Atrial kick is absent if there is loss of normal electrical conduction in the heart, such as during atrial fibrillation, atrial flutter, and complete heart block.
    Ventricular systole is the contraction of the muscles (myocardia) of the left and right ventricles.The closing of the mitral and tricuspid valves (known together as the atrioventricular valves) at the beginning of ventricular systole cause the first part of the "lub-dub" sound made by the heart as it beats. The second part of the "lub-dub" (the Second Heart Tone, or S2), is caused by the closure of the aortic and pulmonic valves at the end of ventricular systole. As the left ventricle empties, its pressure falls below the pressure in the aorta, and the aortic valve closes. Similarly, as the pressure in the right ventricle falls below the pressure in the pulmonary artery, the pulmonic valve closes.
    Cardiac Diastole is the period of time when the heart relaxes after contraction in preparation for refilling with circulating blood. Ventricular diastole is when the ventricles are relaxing, while atrial diastole is when the atria are relaxing. During ventricular diastole, the pressure in the (left and right) ventricles drops from the peak that it reaches in systole. When the pressure in the left ventricle drops to below the pressure in the left atrium, the mitral valve opens, and the left ventricle fills with blood that was accumulating in the left atrium.
    Pathogenesis of 3rd heart sound
    Sound is produced due to rapid filling of ventricle during early diastole leading to sudden limitation of expansion ventricle causing vibration.
    · Causes
    A.Physiology
    1.healthy young adult
    2.athleta
    3.pregnancy
    4.fever
    B.Pathology
    1.cardiac failure
    2.mital regurgitation
    3.dilated cardiomyopathy
    Pathophysiology 4th heard sound
    In condition wih decreased ventricular compliance,there will b increased atrial contraction producing ventricular distension causing sound during presystolic phase
    Causes: condition ass wf LVH n RVH

  8. #48
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    myocardial fibers hav resting membrane fibers and potencial 90mv.Individual separate membrane, but depolarization spreads radially through them as if they were syncytium because the presence of the difference between the interfaces. transmembrane cell cardiacmuscle potencial single action is characterized by a rapid depolarization, a plateau and then a slow repolarization. Initail depolarization is due to Na ions flowing just the opening of ion channels, Na. flow of Ca, Ca ionchannels slowly opening. Repolarization who left without pottasium through a series of ion channels.

  9. #49
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    This is really very important to know more about this. The position of the valves when the ventricles contract can have a big effect on the first heart sound. If the valves are wide open when the ventricule contracts, a loud S1 is heard. This can occur with anemia, fever or hyperthyroid.


    casino spel

  10. #50
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    Nice thread.
    I think the cardiac cycle is the sequence of events that occur when the heart beats.
    The cycle has two main phases: diastole, when the heart ventricles are relaxed,
    and systole, when the ventricles contract.

 

 
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