CARDIOVASCUAR CHANGES DURING PREGNANCY

• During pregnancy the uterus enlarged due to development of the fetus.
• Enlarged uterus pushed heart to upwards The heart moves slightly outward
• The heart also rotates little to the left
• This causes slightly changes occur in position of heart
• Some times due to changes in position  of  heart may cause palpitation.
• The Apex beat of the heart is felt in 4th intercostal space.
• Normal apex beat of heart in non pregnant state in 5th intercostal space mid-clavicular line .
• Apex beat of heart  in pregnancy about 2.5 cm outside the mid clavicular line  and in 4th intercostal space .
• Due to Increase blood flow through  the internal mammary vessels in of breast soft continuohissing murmur  sound may be audible in the left second and third intercostal space which is called mammary murmur .
• Doppler echo cardiography test of the heart shows ( increase in the left ventricles of heart at the time of diastole when it is filled with blood .
• Right atrium receives blood from venacava and left atrium receives blood from the lungs,these both chamber bigger than normal . which is seen in Doppler echo cardiography.
• Third heart sound (S3):It is an extra heart sound heard after the normal “lub-dub”.It happens during diastole (when the heart relaxes and fills with blood).Cause: rapid filling of blood into the ventricle.In pregnancy, it can be normal due to increased blood volume.
• Fourth heart sound (S4): is another extra heart sound, heard just before the normal “lub-dub”.It happens when the atria push blood forcefully into the ventricle.It is rarely heard in pregnancy.
• ECG is normal, but may show a slight left axis deviation to the changed position of the heart in pregnancy.

      CARDIAC OUTPUT

• The cardiac output starts to increase from 5th week of pregnancy.It reaches its peak at about 30 to 34 weeks .( Increase 40 to 50 %)There after cardiac output remain stable till term .
• Cardiac output varies with body position.
  It is lowest in sitting or supine position.
  It is highest in lateral or knee-chest position.During labour, cardiac output increases by about 50%.
• HiImmediately after delivery, cardiac output and MAP rise further.This is due to blood from uterus entering maternal circulation.
• Cardiac output returns to pre-labour level within 1 hour.
• It returns to normal pregnancy level within 4 weeks.
• Increase in cardiac output is due to increased blood volume, stroke volume, and heart rate.

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       During pregnancy, systemic vascular resistance                  (SVR) decreases.(. SVR  means how much the blood            vessels resist blood flow in the body.)

• This decrease is due to hormones like progesterone, nitric oxide (NO)( Nitric oxide lowers blood pressure by relaxing and widening blood vessels.),
• prostaglandins, and ANP.(ANP is a heart hormone that lowers blood pressure by removing extra fluid and relaxing vessels.(ANP means Atrial Natriuretic Peptide (a hormone from the heart).These substances cause relaxation of smooth muscles in blood vessels.So, blood vessels become wide (vasodilation)Because vessels are wide, resistance to blood flow decreases.
• At the same time, cardiac output (CO) increases.
• But BP = CO × SVR, so decrease in SVR lowers BP.
• Therefore, maternal blood pressure decreases slightly.
• Especially diastolic BP and MAP fall by about 5–10 mmHg, following the decrease in SVR
• In pregnancy, venous pressure changes in the body.
• Antecubital venous pressure (in arm) remains normal.
• Femoral venous pressure (in leg) increases during pregnancy.
• It becomes higher especially in the later months.
• This happens due to pressure of the pregnant uterus on veins.
• The pressure is more on the right side due to uterine rotation.
• Femoral venous pressure rises from about 8–10 cm H₂O to 25 cm H₂O (lying).
• It becomes even higher in standing position.
• This increased pressure leads to swelling (edema), varicose veins, and piles.
• These symptoms improve with rest because venous pressure decreases.

        CENTRAL HAEMODYNAMICS

• During pregnancy, there is increased blood volume.
• But central pressures like CVP, MAP, and PCWP do not change much.
• CVP means pressure in large veins near the heart.
• MAP means average blood pressure in the arteries.
• PCWP means pressure in the lungs’ blood vessels.
• These pressures stay stable because the body adapts to changes.
• There is a decrease in systemic vascular resistance (SVR).
• There is also a decrease in pulmonary vascular resistance.
• Colloid osmotic pressure (protein pressure in blood) decreases slightly.
• These changes help maintain balance and prevent major changes in central hemodynamics.

        SUPINE HYPOTENSION SYNDROME

• In late pregnancy, the large uterus presses on the inferior vena cava (IVC).
• The IVC is a vein that returns blood from the lower body to the heart.
• When a woman lies in supine (on the back) position, this pressure increases.
• Due to this, blood return to the heart decreases.
• This can cause low blood pressure (hypotension).
• It may also cause fast heartbeat (tachycardia) and fainting (syncope).
• The body sometimes tries to compensate by using collateral veins.
• These include paravertebral and azygos veins.
  If collateral circulation does not work well, symptoms become severe.
• Symptoms quickly improve when the patient is turned to the left lateral positio
•   REGIONAL  DISTRIBUTION OF BLOOD FLOW

 

• During pregnancy, blood flow is redistributed in the body.
• Uterine blood flow increases from about 50 ml/min to 750 ml/min near term.
• This increase helps in fetal growth and development.
• It is due to uteroplacental and fetoplacental vasodilation.
• Vasodilation is caused by hormones like progesterone, estrogen, nitric oxide, prostaglandins, and ANP.
• Blood vessels become less responsive to constricting hormones like angiotensin II.
  Pulmonary (lung) blood flow also increases.
  Renal (kidney) blood flow increases to about 400 ml/min.
• Blood flow to skin and mucous membranes increases up to about 500 ml/min.
  This increased blood flow causes warmth, sweating, and heat sensation in pregnant women.