Cardiology Flashcards
Heart arises from
Mesoderm
Heart formation complete by
8 weeks
Tube formation
First phase of heart formation
Day 15 to 21
Looping
Second phase of heart formation
Day 21-28
Determines left/right
Distinct chambers appear
Septation
Third phase of heart formation
Day 34–46
Atrial and ventricular septum appear
Fetal circulation
Oxygened DV blood enters RA and flows across FO (due to the velocity and angle) into the LA
This oxernnated blood goes to heart (coronary arteries), brain, upper body
Fetal shunts
Foramen ovale
Patent ductus arteriosus
Which ventricle provides most of the cardiac output in utero?
Right ventricle
= hypertrophied in utero and immediately after birth
What percentage of total blood volume is supplied by each ventricle in utero?
RV 70%
LV 30%
What % of total blood volume goes to fetal lungs in the 2nd trimester?
10%
3rd trimester - increases to 35%
Which side of the intrauterine heart has higher oxygen saturations?
Left side
= Higher oxygenated blood from the umbilical vein shunted across PFO to LA
SVC/IVC blood returns to RA and has low oxygen saturations
Fetal oxygenation in various vessels
Uterine artery 98%
Uterine vein 76%
Umbilical vein 68%
Umbilical artery 30%
Fetal compensation for hypoxemic environment
- Increased fetal EPO
- Fetal hemoglobin causes a left shift in oxyhemoglobin curve
- Decreased oxygen consumption
- maternal thermal regulation
- minimal respiratory effort
- minimal G.I. digestion/absorption
- decreased renal tubular reabsorption
In utero, pressures on both sides of the heart are ___?
Equal
Due to large communications between atria and great vessels
Fetal regulation of cardiac output
Adjustment in fetal HR is the primary mechanism of changing CO in utero
What needs to happen in order for the fetus to transition effectively?
- Increase in pulmonary blood flow
- Distinction between systemic and pulmonary circulations
- Switch in ventricular roles
- Separation from umbilical and placental circulations
Closure of the PDA after birth is due to:
Higher O2 concentration within ductal tissue
Lower amount of E type prostaglandins
- increased pulmonary blood flow = increased metabolism of PGE in lungs
- loss of PGE from placenta
Bradykinin from lungs at birth -> vasoconstriction of PDA

Why does umbilical vein constrict?
Due to lack of flow once umbilical cord is clamped
Why do umbilical arteries constrict?
Because of high oxygen, similar to PDA
When do most structural cardiac anomalies develop by?
Eight weeks gestation
What determines growth of the heart and blood vessels in utero?
Amount of flow through the vessel or chamber
Right sided obstructive lesion in utero
Systemic CO is the same
- more blood across PFO with growth of LV
- usually has VSD with R -> L shunting
Left sided obstructive lesion in utero
- Shift of blood volume from L to R at FO
- Left sided hypoplasia with growth of RV (now provides all of CO)
- Often with VSD, which increases L -> R shunting further
- Intracardiac mixing -> slightly decreased O2 to brain/coronary
Causes of hypoxemia in utero
Decreased O2 delivery to placenta
- maternal hypoxemia
- decreased uterine blood flow
Placental issue
- impaired O2 diffusion
- inadequate placental surface
Umbilical cord issue
- decreased blood flow
To compensate blood flow preferentially goes to heart, brain, and adrenal glands
Fetal compensation for hypoxemia
Fetus goes into hibernation mode
- suppressed respirations
- bradycardia
- decrease in CO
O2 uptake does not change significantly
Fetal O2 delivery can be reduced by 50% without significant effect on O2 uptake
What are three determinants of stroke volume?
Preload
Afterload
Contractility
Preload
Degree of cardiac myocyte stretch at the end of diastole
= Volume in the ventricle at the end of filling = end diastolic volume (EDV)
Afterload
Tension/stress that develops in the LV wall during ejection (to push blood out)
Ventricular wall stress = (ventricular P x ventricular radius) / Wall thickness
Contractility
Force and velocity of a contraction
Frank Starling principle
Increased LV diastolic filling (Inc preload) -> increased stroke volume (pumping ability of the heart)
Qp/Qs < 1
Right to left intracardiac shunt (i.e. tricuspid atresia)
- Lower amount of pulmonary blood flow
- Qp/Qs < 1
- Qp/Qs < 0.7 suggests a large shunt

Hypotension vs shock
Hypotension: when blood pressure is less than the expected reference range
- tissue perfusion may still be adequate
Shock: when there is decreased tissue perfusion
- usually BP is low but not always
Contributors to shock
Low cardiac output
Abnormal vasomotor tone
Low tissue oxygenation
Causes of low cardiac output
Low HR
Low SV
High HR can also cause -> decreased ventricular filling time -> decreased preload
Causes of abnormal vasomotor tone
Tissue factors
Vascular factors
Neurohormonal factors
Causes of low tissue oxygenation
Low O2 delivery to alveoli
Poor lung perfusion
Low O2 caring capacity (low Hb)
Poor O2 release from Hb (left shift in oxyhemoglobin curve)
Hypovolemic shock
Most common type of neonatal shock
Occurs when intravascular BV is below a critical level -> poor ventricular filling
Decreased preload -> decreased SV -> decreased CO -> decreased BP -> inadequate tissue perfusion
Cardiogenic shock
Myocardial dysfunction leads to
- Poor ventricular emptying
- Poor cardiac filling
Decreased contractility -> decreased SV -> decreased CO -> decreased BP -> Inadequate tissue perfusion
Distributive shock
Severe vasodilation -> relative decrease in intervascular volume
Decreased SVR -> decreased BP -> inadequate tissue perfusion
Flow restrictive shock
Obstruction to cardiac output
Etiologies:
Tension pneumothorax
Cardiac tamponade
Left sided obstructive cardiac defect
Dissociative shock
Inadequate oxygen releasing capacity
Etiologies:
Profound anemia
Methemoglobinemia
Excessive carbon monoxide
Compensated neonatal shock
Blood flow distributed to brain, heart, adrenal glands expense of non-vital organ perfusion
Uncompensated reversible neonatal shock
Bloodflow decreases to all organs
Uncompensated irreversible neonatal shock
Irreversible cell damage
How does a neonate compensate for shock via increased blood volume?
Renin–angiotensin system increases water reabsorption and decreases urine volume

Autotransfusion = reabsorption of interstitial fluid into vasculature
Stages of uncompensated shock
Anaerobic metabolism = major source of energy
Release of chemical mediators (histamine, cytokines) -> decreased tissue perfusion
Capillary endothelium integrity disrupted -> loss of oncotic pressure
Sluggish blood flow -> activation of coagulation cascade -> bleeding
Alpha-2 adrenergic receptors
Decreased SVR
Inhibit adenylyl cyclase

Dopamine
Endogenous, precursor to epinephrine and norepinephrine
Beta-1 (medium dose) and alpha-1 receptors (high-dose)
Increased HR at medium dose
Increased contractility at medium dose
Increased SVR at high-dose
Increases BP via increased CO and SVR
Dobutamine
Synthetic Beta-1 and some beta-2  Mild increase in HR Increases contractility Decreases SVR Increases BP by increased CO (increased SV)
Epinephrine - extra effects
Increases lactate due to increased glycogenolysis
High Dose epi leads to increased SVR during diastole and improvement in coronary artery perfusion
Norepinephrine
Beta-1 and Alpha-1, some beta-2
Similar to high dose epi
Decreases HR (inc vagal tone on SA and AV nodes)
Increases contractility
Increases SVR
Increases BP because of increased SVR
Milrinone
Phosphodiesterase type 3 inhibitor -> increased cAMP similar to Beta stimulation
Decreases SVR more than dobutamine
Increase in contractility
Principles of cardiopulmonary circulation
Pulmonary and systemic circulations are separate, balanced, flow in series, and each has its own ventricle
Left to right shunt
Oxygenated blood from the left side crosses to the right and returns to lungs
Flow to lungs > flow to body
Qp > Qs
Tachypnea, failure to thrive, congestive heart failure
Right to left shunt
Deoxygenated blood crosses to the left, bypasses the lungs, and joins the systemic circulation
Flow to the lungs < flow to the body
Qp < Qs
Cyanosis, acidosis, tachypnea
Factors that increase PVR
…And decrease Qp Pulmonary vasoconstriction - hypoxia - acidosis Increased interstitial pressure - atelectasis - pulmonary edema - pneumothorax/pleural effusion - mechanical ventilation - excess PEEP Lung hypoplasia Polycythemia
Factors that decrease PVR
Pulmonary vasodilation - alkalosis - oxygen - nitric oxide - sildenafil Alveolar expansion
Simple mixing cardiac lesions
PDA, ASD, VSD
Qp and Qs are not separate and can be unbalanced
There is mixing of pulmonary and systemic venous return with a net left to right shunt

Not ductal dependent
No differential between upper and lower saturations
Present with varying degrees of congestive heart failure
Pathophysiology of a neonatal PDA
Falling PVR Pulmonary overcirculation Pulmonary hypertension Diastolic runoff Increased cardiac work
Treatment of simple mixing cardiac lesions
Decrease workout breathing with diuretics
Support growth
Support cardiac function (+/- digoxin)
Judicious use of oxygen
Repair:
ASD at 3-5 years of age, earlier if worsening chronic lung disease or ventilator dependence
VSD after six months of age
Complex mixing cardiac lesions
Complete AV canal, truncus arteriosus, unobstructive TAPVR, single ventricles without outflow obstruction
No separation between Qp and Qs
Complete AV canal
Primum ASD
Small to large VSD
Lack of separation of the mitral and tricuspid valves
One of the most common cardiac lesions in T21
Repair at 3 to 6 months
Truncus arteriosus
Single outflow tract
Absence of a pulmonary valve (single S2)
Large truncal (aortic) valve
VSD
Pulmonary arteries arise from ascending aorta
A/W DiGeorge syndrome
Complete mixing of venous return
Can develop pulmonary hypertension
Repair at 1 to 2 weeks
Unobstructed TAPVR
Pulmonary venous return drains into the right atrium (L -> R shunt) (or another vessel, but not LA)
Some flow crosses the ASD (R -> L shunt)
Complete mixing leads to lower saturations
Right heart enlargement and pulmonary overcirculation occurs as PVR drops
Repair at 2 to 6 months
Treatment of complex mixing cardiac lesions
Decrease work of breathing with diuretics
Support growth
Support cardiac function (+/- digoxin)
Judicious use of O2 (sat goal 85%)
Surgical repair if CHF cannot be adequately treated and before pulmonary hypertension becomes irreversible
Right sided obstructive heart lesion examples
Tetralogy of Fallot Tricuspid stenosis/atresia Ebstein’s anomaly Branch pulmonary stenosis Supravalvar pulmonary stenosis Pulmonary stenosis/atresia
Tetralogy of Fallot
PROVe - pulmonary stenosis - RVH - overriding aorta - VSD
Repair at 3–4 months

What is a tet spell?
Infundibular spasm leading to severe obstruction in Qp
Symptoms are cyanosis, tachypnea, irritability, acidosis, cardiac arrest
How to treat a tet spell
Decrease PVR: O2, iNO, morphine
Increase SVR - knees to chest
R-sided obstructive heart lesion pathophysiology
Obstruction within the right heart leads to blue blood shunting to the left heart/systemic circulation -> cyanosis
Degree of obstruction determines the signs and symptoms
Severe obstruction requires the PDA to support pulmonary blood flow
- closure of PDA-> severe synosis and cardiogenic shock
Hallmark: R->L flow across PFO and mixing in the LV -> Pre-and post ductal hypoxemia
Treatment of right sided obstructive heart lesions
Maintain ductal patency with PGE
Decrease oxygen demand
Support cardiac function
Judicious use of oxygen - goal sats 75-85% so that Qp/Qs=1
Surgical repair
- provide a stable source of pulmonary blood flow and allow PDA to close
- or if obstruction cannot be relieved, provide an alternative to the PDA
Which right sided obstructive lesions require immediate catheter or surgical intervention after birth?
None, unless the PDA closes
Left-sided obstructive heart lesion examples
HLHS Shones syndrome Supravalvar aortic stenosis Aortic stenosis/atresia Mitral stenosis/atresia Obstructed TAPVR Coarctation of the aorta Interrupted aortic arch
HLHS
Mitral stenosis/atresia Hypoplastic L ventricle Aortic stenosis/atresia Hypo plastic aortic arch ASD/PDA
Only way for blood to get to coronary arteries is via PDA and retrograde aortic flow
Pathophysiology of left sided obstructive lesions
Obstruction within the left heart leads to:
- oxygenated blood to the right heart and pulmonary circulation -> congestive heart failure
- insufficient systemic flow leading to acidosis and cardiogenic shock
Severe obstructions require ductal support (PDA)
R->L flow across the PDA -> lower post-ductal saturations
Left sided obstructive lesions that require immediate intervention after birth
HLHS with intact atrial septum and PDA
Obstructed TAPVR and PDA
Treatment of left sided obstructive heart lesions
Maintain PDA
Support cardiac function
Decrease oxygen demand
Judicious use of oxygen, goal sats 75–85%
Surgical repair aims to
- relieve the obstruction and get rid of the PDA
- provide an alternative to the PDA
Examples of single ventricles without outflow obstruction
Unbalanced AV Canal
Double Inlet left ventricle
Hypoplasia of one of the ventricles
No obstruction to flow to lungs or body
Double inlet LV
Systemic and pulmonary venous return enter a single ventricle
Complete mixing of blood leads to lower saturations
As PVR drops pulmonary overcirculation develops
Similar physiology to complex mixing lesions
Examples of single ventricle lesions with outflow instruction
HLHS
Pulmonary atresia
d-TGA
Parallel circulations
Lack of intracardiac shunt and loss of PDA leads to severe cyanosis, acidosis, shock
Higher post-ductal sats of PDA present = reverse differential
L-TGA
Congenitally corrected TGA
Increased risk of heart block
Cardiac anomalies with Williams
Supravalvar AS
Branch PA stenosis

Sinus rhythm on EKG
P-wave before every QRS
QRS after every P-wave
P-waves upright in leads I and aVF
All P-waves look the same
Premature atrial contractions
Atrial myocyte initiates a beat between impulses coming from the sinus node
Early P-wave can be buried in T-wave
QRS also arrives early
Premature ventricular contractions
Early QRS, usually wide or unusual
No P-wave
T wave axis is directly opposite the QRS axis
Compensatory pause afterwards
Reassuring if single morphology, isolated beats, suppresses with sinus tachycardia
2nd degree heart block
Some atrial activity gets through to the ventricles
Atrial rate is normal
Ventricular rate/rhythm depends on how often the AV conduction occurs
Complete heart block
No relationship between P and QRS waves
Ventricular rate remains regular and slow
Atrial rate is faster than ventricular rate but still normal
Atrial flutter
Very fast atrial rhythm with slow ventricle rhythm
Sawtooth waves
Giving adenosine is diagnostic but not therapeutic
Electrical cardioversion or rapid atrial pacing will break the circuit
Recurrent a flutter - digoxin or propranolol
Torsades
Polymorphic VT with oscillating pattern of the QRS axis
Treatment with IV magnesium sulfate
Causes of prolonged QTc
Hypocalcemia Hypokalemia Hypomagnesemia CNS abnormalities Myocarditis
Channelopathy
- >75% of LQTS caused by mutations in three genes (KCNQ1, KCNH2, SCN5A)
Management of complete heart block
Require emergent pacing - neonate with CHF
Require pacemaker:
- Mobitz II or third degree with symptoms, ventricular dysfunction, low CO
- CHB with ventricular rate <55
- CHB + CHD with ventricular rate <70
- CHB with QRS escape or V dysfunction
Most common type of tachyarrhythmia in a newborn
Atrio-ventricular re-entry tachycardia (AVRT)
A.k.a. WPW
Wolfe-Parkinson-White
Accessory pathway permitting conduction across the AV valve
Delta wave present when the atrial impulse enters the ventricles via an accessory pathway
Which structural defect is most commonly associated with an accessory pathway?
Ebstein’s anomaly
EKG findings in Ebstein’s anomaly
Very tall P waves
What causes increased preload?
- increased circulating blood volume
- increased venous tone (more BV back to heart)
- increased ventricular compliance
- increased atrial contractility
- decreased intrathoracic pressure (increased venous return)
Effect on afterload with ventricular dilation
If ventricle is dilated -> increased ventricular wall stress with greater tension on the myocytes -> increased afterload
Effect on afterload with ventricular hypertrophy
If ventricle is hypertrophied (wall thickened) -> distributed across many cells -> decrease in afterload
Qp/Qs > 1
Left to right intracardiac shunt (i.e. VSD)
- Greater pulmonary blood flow
- Qp/Qs > 1
- Qp/Qs > 2 suggests a large shunt
Etiologies of cardiogenic shock
Cardiomyopathy Heart failure Arrhythmias Perinatal depression (myocardial ischemia) Acidosis Sepsis
Etiologies of distributive shock
Sepsis
Vasodilators
Adrenal insufficiency
Anaphylactic or neurogenic (adults)
Alpha-1 adrenergic receptors
Increased SVR
Increased contractility
Activate phospholipase C
Beta-1 adrenergic receptors
Increased contractility
Increased HR
Induce cAMP production
Beta-2 adrenergic receptors
Decreased SVR
Bronchodilation
Induce cAMP production
Low dose epinephrine
Beta-1 and beta-2 (similar to dobutamine) Increases HR Increases contractility Decreases SVR Can either increase or decrease BP
High-dose epinephrine
Alpha-1 and beta-2 (similar to dopamine) Decreases HR (inc vagal tone on SA and AV nodes) Increases contractility Greatly increases SVR Increases BP due to increased SVR
TOF with severe pulmonary stenosis
R->L shunt
O2 sats <90%
Leads to cyanosis, may be ductal dependent for Qp, tet spells
TOF with mild pulmonary stenosis:
L->R shunt through VSD as PVR drops O2 sats >90% Leads to: - pulmonary overcirculation - congestive heart failure - failure to thrive
Cause of pre-ductal hypoxemia in left-sided obstructive heart lesions
Occurs when there is minimal flow across aortic valve -> retrograde flow in the arch from the PDA
Cardiac anomalies with Alagille
Branch PA stenosis
Pulmonic stenosis
TOF
Cardiac anomalies with DiGeorge
VSD
Truncus arteriosus
TOF
Interrupted aortic arch
Cardiac anomalies with Holt Oram
ASD
VSD
Cardiac anomalies with Marfans
Aortic root dilation
Aortic valve prolapse
Cardiac anomalies with Noonans
Pulmonary stenosis
TOF
Cardiac anomalies with T21
ASD
VSD
Common AV canal
Cardiac anomalies with Turners
Bicuspid aortic valve
Aortic stenosis
Coarctation
Interrupted aortic arch
Causes of PACs
Very common, usually benign Increased vagal tone Central line Electrolyte abnormalities Hypoxemia Thyroid problems Cardiomyopathy Drugs (digoxin, caffeine, beta-agonist)
Causes of PVCs
Immature myocardium Electrolyte problems Metabolic disease Cardiomyopathy Intracardiac tumors
2nd degree heart block - Wenckebach
Progressive PR prolongation -> dropped sinus beat -> short recovery PR
2nd degree heart block -  Mobitz II
Normal PRs with a dropped sinus beat
Pathologic, can cause symptoms
May progress to complete heart block
Eval for LQTS, Myocarditis
WPW and SVT
- impulse begins in the atria
- Circuit develops which involves the AV node and accessory pathway
- abrupt onset and termination
- fast (190-300) and regular
- always 1:1 conduction
Treatment of WPW
Vagal maneuvers or adenosine
If not effective cardioversion or rapid atrial pacing
Recurrent WPW SVT - Propranolol or digoxin
Examples of automatic SVTs
Sinus tachycardia
Ectopic atrial tachycardia (EAT)
Multifocal atrial tachycardia
Junctional ectopic tachycardia
Consider an automatic tachycardia if…
Heart rate increases and decreases gradually
Heart rate varies during the tachycardia
Rhythm doesn’t break with adenosine or cardioversion
Treatment of automatic SVT
Vagal man. or adenosine only briefly inhibit conduction to ventricle
Electrical cardioversion does not stop tachycardia
RX: flecainide, amiodarone, sotalol
Want to slow atrial activity or decrease ratio of conduction across AV node
Northwest left axis deviation on EKG
190 to -100
Negative QRS in leads I and aVF
Coarctation
Right axis deviation on EKG
100 - 190
Negative QRS in lead I, positive QRS in lead aVF
Normal newborn axis
Right ventricular hypertrophy (TOF, coarct)
Left axis deviation on EKG
-100 to 0 Positive QRS in lead I, negative QRS in lead aVF AV canal Primum ASD Tricuspid atresia
Also called superior axis deviation
Normal axis on EKG
0-100
Positive QRS in lead I and aVF
Which electrolyte abnormality causes Short QT?
Hypercalcemia
Which electrolyte abnormality causes prolonged QT?
Hypocalcemia
What electrolyte abnormality causes long PR, wide QRS, and peaked T waves?
Hyperkalemia
If worsens can have absent P-wave and sinusoidal asystole
What electrolyte abnormality causes depressed ST, biphasic T-wave, and prominent U wave?
Hypokalemia
How does a neonate compensate for shock via vasoconstriction?
- Decreased stimulation of baroreceptors in aortic arch and carotid sinus
- Chemoreceptors respond to cellular acidosis
- Catecholamine release
What cardiovascular structure develops from the 3rd pharyngeal arch?
Carotid arteries
What cardiovascular structure develops from the right 4th pharyngeal arch?
Subclavian artery
What cardiovascular structure develops from the left 4th pharyngeal arch?
Aortic arch
What cardiovascular structure develops from the left 6th pharyngeal arch?
PDA
