Cardiac Cycle Flashcards
T/F electrical events initiate the mechanical events
T
Types of contraction inc radial muscle
. Isometric: contraction where force is generated in absence of change in fiber length (isovolumetric in heart)
. Isotonic: contraction where a dec. in fiber length occurs in absence of change in force (change in volume in absence of change in pressure)
Type of contraction with valve in opening
. Begins as isometric contraction then becomes an isotonic contraction
. Change in volume begins when pressure inside exceeds outflow pressure and then valve opens which allows volume displacement to begin
. When valves close, the ventricles are contracting isometrically
. When valves open the outflow valves open and outflow begins so contractions are nearly isotonic
Afterload
. Resistance against which the chamber is contracting or pumping
. With a large afterload (excessively high diastolic aortic pressure) the afterload Ed contraction would eventually become a purely isometric contraction
. With no afterload, the contraction would be purely isotonic
Phases of ventricular contraction
. Systole Isovolumetric ventricular contraction (AV valves and aortic and pulmonary valves closed)
. Systole Ventricular ejection: blood flows out of ventricle (AV valves closed, aortic and pulmonic valves open)
. Diastole isovolumetric ventricular relaxation (All valves closed)
. Diastole ventricular filling w/ atria relaxed, then ventricular filling w/ atria contraction (AV valves open, others closed)
Isovolumetric contraction phase
. Ventricle contract following depolarization
. Begins shortly after QRS complex
. Bother valves are closed to pressure inc. but volume doesn’t change
Ventricular ejection phase
. Pressure in ventricles then exceeds diastolic pressure in aorta (LV) Or pulmonary a. (RV) and outflow valves open and blood ejected
. Has initial rapid ejection followed by reduced ejectionphase
. Initially ventricular pressure continues to rise
. Pressure in LV and aorta is identical in ejection (true for right side too)
Isovolumetric relaxation phase
. At end of ejection phase the initial fall in ventricular pressure occurs due to loss of significant volume of blood in ventricles
. Outflow valves close as pressure gradient reverses approx. coinciding w/ onset of ventricular relaxation
. Closure of outflow valves is onset of diastole
. During isovolumetric relaxation both set of valves are closed
. Ventricular pressure declines rapidly w/o a change in volume
Ventricular filling phase
. Rapid filling phase: during rapid filling, ventricular pressure in than than atrial pressure so process is passive, it is rapid bc the pressure gradient favors rapid movement
. Reduced filing phase: as ventricles fill, intraventricular pressure inc. that leads to slowing of filling, process still passive
. Atrial contraction (atrial systole): active, follows atrial depolarization, accounts for 20-30% of ventricular filling volume, may inc. during exercise
Similarities in cardiac cycle of R and L ventricles
. Same phases
. Sequence of valves opening and closing
Difference between cardiac cycle of L and R ventricles
. Pressure in pulmonary circulation lower than systemic so afterload for RV is lower than for LV
. Systole of LV beings slightly before contraction of RV begins
. Pulmonic valve opens before aortic valve due to difference in afterload
. Pulmonic valve closes after aortic valve closes bc of difference in afterload too
S1 heart sound
. Produced by closing of AV valves at onset of systole
. Closure of mistral precedes tricuspid by 0.01 sec
. Results from vibration of valves immediately after closure from ventricular pressure exceeding atrial pressure
. Intensity enhanced w/ shorter PR interval, mild mitral stenosis, high CO
. Intensity diminished w/ long PR interval, and mitral regurgitation
S2 heart sound
. Occurs during diastole
. Assoc. w/ closure of semilunar valves when pressure in ventricles fal below pressure in corresponding great a.
. Sounds from recoil of blood from closed valves back into aa. Causing reverberation
. Aortic valve closes before pulmonic so it has aortic and pulmonic component sounds
Physiological split
. 2nd heart sound in S2 from A2 and P2
. Interval btw A2 and P2 varies w/ respiration
. Inc. w/ pulmonary stenosis
Physiological split during inhalation
. Chest expands, intrathoracic pressure becomes more neg., blood flow inc. returning to right side of heart
. Inc. filling enhances RV EDV and stroke volume
. Causes inc. in ventricular emptying time during ejection phase, delaying closure of pulmonic valve
. Neg. intrathoracic pressure enhances capacity of pulmonary vv. Reducing venous return to LV
. Causes shorter LV ejection and early closure of aortic valve
Physiological split during expiration
. Intrathoracic pressure becomes less neg.
. Pulmonic and aortic valve closing occurs at approx. same time and split narrows or disappears
Paradoxical split
A2 follows P2
. Occurs w/ left bundle branch block or severe aortic stenosis
Extra systolic heart sounds
. Usually heard as clicks
. Ejection click: early is systole shortly after S1, indicate pulmonic stenosis or dilation or aorta or pulmonary a.
. Click in mid-late systole due to bulging of prolapsed mitral or tricuspids into corresponding atrium
Extra diastolic heart sounds
. Opening snap: after S2 w/ mitral or tricuspid stenosis
. S3: during rapid filling phase, sound from excessive oscillation of blood back and forth btw ventricular walls as blood rushes in from atria hitting leaflets, mark of CHF or mitral/tricuspid regurgitation
. S4: late diastole, sound from atrial contraction into stiff ventricle from hypertrophy or ischemia
Most murmurs are due to ____
Valvular lesions
. Can be caused by septal defects or patent ductus arteriosis
Systolic murmurs
. Aortic/pulmonic stenosis
. Mitral/tricuspid insufficiency
. Interventricular septal defects
Aortic or pulmonic valve stenosis
. Narrowing of valve leading to turbulent flow
. Blood flow in normal directions hrough small opening
. Intensity varies w/ rate of blood flow
. Exhibits crescendo-decresendo intensity
. Pressure gradient across stenosis valve
Mitral/tricuspid insufficiency
. Regurgitation of blood through incompetent valves leading to turbulent flow
. Valves won’t completely close so blood is forced back into atrium from high pressure in ventricle
Interventricular septal defects
. Patent (unsealed) openings btw ventricles
. Less common
. Blood flows from LV to RV through opening due to high LV pressure
Diastolic murmurs
. Mitral stenosis: narrowing of AV valve on left side causes turbulent flow
. Aortic insufficiency: regurgitation go blood through incompletely closed aortic valve causing turbulent flow
Continuous murmurs
. Occurs throughout all of systole and diastole
. Most common cause is patent ductus arteriosus
. Blood flow occurs from aorta to pulmonary a. Throughout cardiac cycle since aortic pressure is always higher than pulmonary a.
To and fro murmurs
. Occurs during parts of systole and diastole
. An outflow valve is both stenosis and insufficient
Murmur grading scale
1: barely audible only w/ stethoscope w/ cardiologist
2: faint but immediately audible w/ stethoscope
3: moderately loud w/ no thrill
4: loud w/ thrill
5: thrill and loud enough to be heard w/ slight touch of stethoscope’s rim on chest
6: thrill and so loud can be heard w/o stethoscope
