Lecture 12: Cardiac Cycle Flashcards
Cardiac cycle 2 phases
Process of atrioventricular contraction + relaxation
1. Systole (vent. contract., blood ejection)
2. Diastole (vent. relax., blood filling)
Systole phases
- Isovolumetric ventricular contraction
- Rapid ventricular ejection
- Reduced ejection
Isovolumetric ventricular contraction
Ventricles develop tension with closed valves; no ejection occurs, ventricular P rises
Ventricular ejection
Vent. P > aorta P, pulm. trunk P opens semilunar valves. Stroke volume = volume of blood ejected in systole
Diastole phases
- Isovolumetric ventricular relaxation
- Rapid ventricular filling
- Reduced filling
- Atrial systole
Isovolumetric ventricular relaxation
Ventricles relax with all valves closed; no change in blood volume. Vent. P decreases
Ventricular filling
Vent. P < atrial P. AV valves open and passive blood filling from atria occurs. 80% filling occurs before atrial contraction right at the end.
Heart sounds
Lub = AV valve closure, softer; systole start
Dub = pulmonary/aortic valves closure, louder; diastole start
Heart murmurs
Sounds caused by turbulent flow due to heart defects
Stenosis
Abnormally narrow valve
Insufficiency
Backflow through leaky valve
Septal defect
Hole in wall separating the 2 atria or the 2 ventricles
Dicrotic notch
Slight bump in aortic pressure when aortic valve closes at end of systole; caused by rebounding of aortic P against the valve.
Wiggers diagram
Describes cardiac cycle events for L side of heart; R side flow must match bc 2 pumps in series
Stroke volume
SV = EDV - ESV
Ejection fraction
EF = SV / EDV (amnt ejected versus filled)
Sinus tachycardia
Increase in HR, often in stressful situations
Paroxysmal tachycardia
Rapid, abrupt start and stop increased HR
Arrythmias
- Supraventricular rhythms
- Ventricular rhythms
- AV blocks
Supraventricular rhythms
Brady, tachy, premature atrial contract., atrial flutter, atrial fibrillation. Sinoatrial, atrial, and AV sourced rhythms.
Atrial flutter
Very fast but regular atrial contraction
Atrial fibrillation
Very fast and irregular atrial contraction; stroke predisposition due to blood pooling in atria.
AV blocks
1st: delay in impulse transmission to vent. (P-R > 0.2s)
2nd: Failure of some but not all atrial contractions to be transmitted (occasional missing QRS)
3rd: complete dissociation of AV electrical activity (A/V out of sync)
Ventricular rhythms
Ventricular automaticity e.g. wide QRS complex (>0.1s)
AV blocks
Diagnosed by P/QRS relation
