Cardiac Cycle

Question 1

What is the normal sinus rhythm?

Answer 1

between 60-200BPM

Question 2

Cardiac Cycle…

Answer 2

• direct mechanical consequence of electrical activity

Question 3

Late Diastole

Answer 3

• AV valves open, blood flows in to the atria and ventricles passively
• 0.6-0.8 seconds into cycle

Question 4

Atrial Systole

Answer 4

• Atrial contraction primes the main pump.. 70% of ventricular filling is passive
• contraction of muscle around great veins minimises backflow along with inertia of blood
• wave of atrial pressure and JVP trace
• 0-0.1 seconds into cycle

Question 5

Ventricular Systole

Answer 5

• isovolumetric contraction - ventricles contract against closed valves until the pressure in the ventricles is greater than the pressure in the atria
• aortic and pulmonary valves burst open, giving the ventricular ejection phase
• C wave of atrial and JV pressures
• 0.1-0.4 seconds into cycle

Question 6

Early diastole

Answer 6

• protodiastole, ventricules stop contracting, blood still flows out through the momentum imparted by ventricular contraction
• aortic and pulmonary valves close and we get isovolumetric relaxation until pressure falls to below atrial pressure
• V wave on JVP and atrial pressure trace from blood flowing into atria
• then AV valves open
• 0.4-0.6 seconds into cycle