Cardiac cycle and wave forms

JVP

JVP reflects relation between

1.Venous tone2.Volume of blood in venous space3.Rt. Heart haemodynamics.

Diastole : JVP directly reflects rt. Ventricular filling pressure

Systole : JVP reflects Rt. Atrial pressure

Cardiac cycle Systole1. Isovolumetric contraction2. Ventricular ejection

Diastole 1. Protodiastole2. Isovolumetric relaxation3. Ventricular filling phase 4. Atrial systole.

Cardiac cycle

Isovolumetric contraction

At the start of ventricular systole, the mitral and tricuspid valve close.

Ventricular muscle initially shorten little but intra ventricular pressure rises sharply as myocardium presses on blood on ventricles.

Lasts for .05 secUntil pressure in lt.and rt. Ventricle exceeds

pressure in aorta(80mm hg)

Pulmonary artery (10mm hg)and aortic and pulmonary valve open.

During iso volumetric contraction the AV valve bulges into atria causing a small but sharp rise in atrial pressure

Ventricular ejection

When aortic and pulm valves open,phase of ventricular ejection begins.

Ejection is rapid at first and slows down as systole progresses.

Intra ventricular pressure rises to a maximum and then declines somewhat before ventricular systole ends.

Peak lt. ventricular pressure is about 120mm hg and peak rt. Ventricular pressure is 25mm

Ventricular EDV = 130 ml.

Ventricular ESV = 50ml.

Stroke Volume (SV) = 80ml.

Ejection fraction = SV/ EDV = 65%

DIASTOLE

Protodiastole:Once the ventricular muscle is fully

contracted , already falling ventricular pressure drops more rapidly.

Lasts about .04 sec. It ends when momentum of ejected blood is

overcome and aortic and pulm valve close.

Ventricular filling phase

During this phase blood flows from atria to ventricle along with the pressure gradient.

Ventricular pressure remains low.

Atrial systole

Contraction of atria propels some additional blood in to ventricle.

Accounts for about 30% of ventricular end diastolic volume.

CARDIAC CYCLE

SYSTOLEClosure of mitral and tricuspid valve-

(1st heart sound) Isovolumetric contraction C waveOpening of aortic and pulm valveVentricular ejection

Diastole

ProtodiastoleClosure of pulmonary and aortic valve (2nd

heart sound). Isovolumetric relaxationOpening of tricuspid and mitral valveVentricular filling phaseAtrial systole (a wave)

JVP

Wave forms

2 visible peaks/waves2 visible descents/troughs

A wave followed by x descentV wave followed by y descentC wave is associated with a waveLate H wave /plateau wave terminates y

descent

a wave

Due to atrial systole.Some blood regurgitates in to great vein,

atria contracts .Even though orifice of great veins are

constricted In addition venous inflow stops and

resultant rise in venous pressure contributes to a wave.

a wave

A wave follows p waves of ECGPrecedes upstroke of carotid pulse.Synchronises with S1.

X descent

Early portion result from RA relaxation during atrial diastole.

Later portion is fall n Rt. Atrial pressure during early rt. Ventricular systole , as tricuspid ring is pulled caudally by contracting RV.

Begins during systole and end before S2.

C wave

Controversy wave/ Confusion wave

2 causes : a) neck veins- cwave is an artifact caused

by transmitted carotid pulse.b) Rt. Atrium – c wave reflects upward

bulging motion of closed tricuspid valve during isovolumetric systole.

This is not commonly seen.

V wave

Continuous venous inflow to Rt. Atrium during ventricular systole when tricuspid valve is closed.

Begin late in systole and ends in early diastole.

Synchronous with carotid pulse and peaks after S2

Y descent

When tricuspid valve opens blood enters the rt. Ventricle rapidly.

There is consequently lowering of Rt. Atrial pressure.

Begins and ends in early diastole.

H wave

This results from passive filling of rt. Heart during diastole.

Seen rarely after y descent.

Some tips….. In a normal person,the a wave is larger

than v wave and x descent is more prominent than y descent

A wave occurs just before S1or carotid pulse and has a sharp rise and fall

V wave occurs just after arterial pulse and has a slow undulating pattern

X descent occurs between S1 and S2 and y descent well after S2

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