Question

Provided below are the pressures in the left atrium, left ventricle, and aorta at a given point during the cardiac cycle of two different NORMAL patients. Based on the three pressures, what phase of the cardiac cycle are each of the two patients in?

Patient 1

Atrial pressure: 10 mmHg

Ventricular pressure: 75 mmHg

Aortic pressure: 85 mmHg

Patient 2

Atrial pressure: 15 mmHg

Ventricular pressure: 10 mmHg

Aortic pressure: 90 mmHg

A) Patient 1: Isovolumetric Contraction

Patient 2: Filling

B) Patient 1: Isovolumetric contraction

Patient 2: Ejection

C) Patient 1: Isovolumetric Relaxation

Patient 2: Ejection

D) Patient 1: Filling

Patient 2: Isovolumetric Contraction

E) Patient 1: Filling

Patient 2: Isovolumetric Relaxation

Answer 1

Ans E

Patient 1: Filling

Patient 2: Isovolumetric Relaxation

Patient 1

Atrial pressure: 10 mmHg

Ventricular pressure: 75 mmHg

Aortic pressure: 85 mmHg

From it we can say that aortic pressure more than ventricular ,that means semilunar valves closed.But still there is 75 mmHg pressure which suggest it has enough blood and little drop in atrial pressure too, suggesting ventricular filling phase.

We can't consider isovolumetric contraction as ventricular pressure is less than that of aortic in an order to open the semilunar valves in the ejection phase, immediately after isovolumetric contraction phase.

Also isovolumetric relaxation phase has very less blood pressure (around 10 mmHg), hence it also not possible.

Patient 2

Atrial pressure: 15 mmHg

Ventricular pressure: 10 mmHg

Aortic pressure: 90 mmHg

Isovolumetric relaxation is a phase in which ventricle completely relax as a close chamber with all valves closed.This happens because to decrease the pressure than that of atrium in an order to maintain the gradient between atrium and ventricle, immediately after the isovolumetric relaxation phase in filling phase.

The pressure gradient opens the A-V valves ,and ventricle filling starts.

So it is isovolumetric relaxation phase as it has least ventricular pressure (also less than that of atrium) and also aorta(keeping semilunar valves closed)