Cardiovascular Review

Question 1

Septal Development of the Heart

Answer 1

Heart begins to develop during 4th week of gestation and is completed during the 8th week
Atrial septum develops at week 4
Ventricular septum is weeks 4-8
Anytime you have a failure of this to develop you are going to end up with a defect
Atrial septal defect or ventricular septal defect

Question 2

Fetal Circulation

Answer 2

What happens when baby is born
Blood comes in through the umbilical vein where it travels to liver and divides. Some goes into hepatic system and the rest goes to inferior vena cava via the ductus venosus.
Pressure in right side of heart is higher than the left
Because of this, the blood is directed across the foramen ovale to the left atrium
Blood from upper extremities and head entering RA most will go into the RV which will go up through pulmonary artery
Quite a bit of blood is shunted across the ductus arteriosus. Lungs are collapsed, don’t need air flow, so the pressure in the lungs is very high. Vasoconstriction in pulmonary vasculature
Very difficult to send blood into the lungs. Most gets shunted across ductus arteriosus
High PVR (pulmonary vascular resistance)
At birth: large volume of circulating blood that shifts away form placenta and into the pulmonary system.
PVR goes way down. So there is vasodilation in pulmonary vascular bed. Lower pressure on right side of heart. Change in blood flow causes rise in pressure in left side of heart which forces the foramen ovale to close. Pressure on left side of heart gets much higher
Shunting across ductus arteriosus also stops (by about 72 hours) because of increased oxygen and decreased prostaglandins
Thickness of muscle at birth is equal left and right

Question 3

Systole

Answer 3

contraction of the heart

Question 4

Diastole

Answer 4

relaxation of the heart

Question 5

Cardiac output

Answer 5

the volume of blood ejected by heart in 1 min
heart rate x stroke volume (HR is the primary thing that infants will do because they don’t have a very good ability to increase stroke volume)

Question 6

Stroke volume

Answer 6

volume of blood ejected by ventricles per beat (in mls)
Affected be:
- preload
- afterload
- contractility (measured by perfusion & urinary output)

Question 7

Heart rate

Answer 7

Influenced by autonomic nervous system (when child with perfusion problems the child can increase HR to improve their CO to a point. if it increases too much it doesn’t allow enough time for filling and the diastolic filling time is not efficient so there isnt enough blood coming into the heart)
- neonates do not have the ability to increase stroke volume -> depends on HR to increase CO

Question 8

Tissue perfusion depends on

Answer 8

HR, circulating blood volume, pump function, systemic & vascular resistances, capillary permeability & tissue utilization of oxygen

Question 9

Heart Failure - Sympathetic Nervous System

Answer 9

1. Stimulation of cholinergic fibers when the heart is stretching or being overworked - sweating, especially on scalp
2. Increase rate and force of contraction -> tachycardia
3. increased vascular tone -> peripheral vasoconstriction which helps increase BP and circulate blood better -> increase venous return, increased pulmonary vascular resistance, increased systemic vascular resistance, increased afterload, decreased blood flow to limbs

Question 10

Increased Vasoconstriction and Kidneys

Answer 10

decreased blood flow to kidneys -> production of renin, aldosterone, and ADH, Na and H2O retention, increase blood volume and increases preload, systemic and pulmonary engorgement

Question 11

Compensatory Mechanisms: Sympathetic Nervous system

Answer 11

release of catecholamines -> increase force & rate of contraction, peripheral vasoconstriction
- Sympathetic cholinergic fibers -> sweating

Question 12

Compensatory Mechanisms: renal system and heart muscle

Answer 12

Renin-angiotensin-aldosterone mechanism
Hypertrophy & dilation of cardiac muscle

Question 13

Clinical Manifestations
- subtle & may not be recognized at first
- as ability to compensate fails, child will exhibit signs of HF
IMPAIRED MYOCARDIAL FUNCTION

Answer 13

• Tachycardia > 160 (one of the earliest signs), gallop rhythm. Direct response of sympathetic response
• Infant tires early, esp. during feeding
• Diaphoresis, irritability
• Weight loss or poor weight gain (developmental delays)
• Frequent infections
• Poor perfusion (cold extremities, weak pulses, slow cap refill, low BP, mottled skin; extreme pallor or cyanosis)

Question 14

Pulmonary congestion: Left Sided Heart Failure

Answer 14

Tachypnea, nasal flaring, grunting, retractions, cough, crackles, wheezing, hoarseness
Cyanosis (late sign)
Orthopnea - relieved by sitting up
Can cause pulmonary edema

Question 15

Systemic Venous Congestion (Right sided HF)

Answer 15

Hepatomegaly
Cardiomegaly
Increased pressure and pooling of blood in right side and backs up into systemic vasculature
Edema (weight gain, perioribital, facial, sacrum, scrotal)
Ascites, pleural effusions
Distended neck & peripheral veins, usually only noted in older children

Question 16

L-sided HF backs up

Answer 16

into the lungs (signs of pulmonary congestion)

Question 17

Right sided HF backs up

Answer 17

back up into periphery (JVD, edema, hepatomegaly)
- right and left are distinc, however, you will rarely see one side without the other.