Session 2 Flashcards
How is the muscle in the ventricular walls arranged?
Into figure of eight bands that squeeze the ventricular chamber forcefully in a way most effective for ejection through the outflow valve. The apex of the heart contracts first and relaxes last to prevent back flow.
Outline the typical pressures in the vessels/chambers of the heart (mmHg)
RA - 0 to 4
RV - 4dias/25sys
Pulmonary artery - 10dias/25sys
LA - 8 to 10
LV - 10dias/120sys
Aorta - 80dias/120sys
What are the 7 main phases in the cardiac cycle?
Atrial contraction Isovolumetric contraction Rapid ejection Reduced ejection Isovolumetric relaxation Rapid filling Reduced filling
What changes are occurring during atrial contraction?
Atrial pressure rises due to atrial systole, this is the A wave.
Atrial contraction accounts for the final 10% of ventricular filling
P wave on ECG signifies onset of atrial depolarisation.
At the end of this phase, the end diastolic volume is reached (~120ml)
What changes are occurring during isovolumetric contraction?
Mitral valve closes as interventricular pressure exceeds atrial pressure. This causes the C wave in atrial pressure and the first heart sound (S1).
Rapid rise in ventricular pressure as ventricle contracts.
Isovolumetric since all valves are closed.
QRS complex in ECG signifies onset of ventricular depolarisation.
What changes are occurring during rapid ejection?
Ejection begins when the ventricular pressure exceeds aortic pressure, causing the aortic valve to open.
Atrial pressure initially decreases as the atrial base is pulled downward as the ventricle contracts. This is called the X descent.
Rapid decrease in ventricle volume.
Blood continues to flow into the atria.
What changes are occurring during reduced ejection?
Repolarisation of ventricle leads to decline in tension and the rate of ejection begins to fall.
Atrial pressure gradually rises due to continuous venous return - this is the V wave.
T wave of ECG shows ventricular repolarisation.
What changes are occurring during isovolumetric relaxation?
Aortic valve closes as the ventricular pressure drops below aortic pressure.
“Dicrotic notch” in aortic pressure curve caused by valve closure. Results in second heart sound (S2).
Volume remains constant since all valves are closed.
Rapid decline in ventricular pressure.
End diastolic volume is reached (~50ml)
What changes are occurring during rapid filling?
Fall in atrial pressure occurs after opening of the mitral valve, called the Y descent.
Normally silent but a third sound (S3) is sometime heard - normal in children, pathological in adults.
What changes are occurring during reduced filling?
Rate of filling slows down. Ventricles are 90% full.
What are the 7 main phases in the cardiac cycle?
Atrial contraction Isovolumetric contraction Rapid ejection Reduced ejection Isovolumetric relaxation Rapid filling Reduced filling
What changes are occurring during atrial contraction?
Atrial pressure rises due to atrial systole, this is the A wave.
Atrial contraction accounts for the final 10% of ventricular filling
P wave on ECG signifies onset of atrial depolarisation.
At the end of this phase, the end diastolic volume is reached (~120ml)
What changes are occurring during isovolumetric contraction?
Mitral valve closes as interventricular pressure exceeds atrial pressure. This causes the C wave in atrial pressure and the first heart sound (S1).
Rapid rise in ventricular pressure as ventricle contracts.
Isovolumetric since all valves are closed.
QRS complex in ECG signifies onset of ventricular depolarisation.
What changes are occurring during rapid ejection?
Ejection begins when the ventricular pressure exceeds aortic pressure, causing the aortic valve to open.
Atrial pressure initially decreases as the atrial base is pulled downward as the ventricle contracts. This is called the X descent.
Rapid decrease in ventricle volume.
Blood continues to flow into the atria.
What changes are occurring during reduced ejection?
Repolarisation of ventricle leads to decline in tension and the rate of ejection begins to fall.
Atrial pressure gradually rises due to continuous venous return - this is the V wave.
T wave of ECG shows ventricular repolarisation.
