Diagnostic Medical Sonography - PowerPoint Presentation

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Diagnostic Medical Sonography

SON 2121

Obstetrical Sonography I

Chapter 14- Ultrasound Evaluation of the fetal heart

HHHoldorf

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Outline

The fetal heart

Fetal echocardiography

Fetal Circulation

The 4 chamber view

Left ventricular outflow tract

Right ventricular outflow tract

Arterial Septal Defects

Ventricular Septal Defects

Hypoplastic Right Heart

Hypoplastic Left Heart

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Transportation of the Great Arteries

Truncus Arteriosus

Double Outlet Right Ventricle

Ectopia Cordis

Cardiac Tumors

Endocardial Cushion Defects

Tetrology of Fallot

Ebsteins’s Anomaly

Ventricular Hypertrophy

Cardiac Arrhythmias

Pericardial Effusion

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Normal Heart Diagram

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The fetal heart occupies approximately one third of the thoracic cavity.

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Fetal Echocardiography should be performed with the assessment of fetal arrhythmias. Whenever congenital heart disease or chromosomal abnormalities is suspected the examination should be considered. If any of these are present, the patient should be referred for fetal echocardiography at 18 to 24 weeks of gestation. Fetal Risk Factors: extra cardiac abnormality; chromosomal abnormality; fetal cardiac arrhythmia; non-immune Hydrops; question of cardiac anomaly on prior sonogram; intrauterine growth retardation. Maternal Risk Factors: family history of CHD; teratogenic exposure; maternal disorders; maternal infection; familial syndromes.

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How is fetal heart imaging useful in Obstetrics?

It can detect structural heart abnormalities such as:

Septal defects, disproportionate chambers

Transportation of the great vessels

Fetal arrhythmias

Coartation of the aorta

Cardiomegaly

Focal masses

Pericardial effusion

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Normal cardiac study checklist:

4 chamber view, right ventricle has moderator band, left atria: can visualize pulmonary veins, and between the atria you must see the space for the foramen ovale which closes after birth

RVOT – RV to pulmonary artery and the bifurcation. The ventricles must cross each other

LVOT – LV to the aorta, must show with and without valve

Aortic arch with the 3 branches (right brachio-cephalic, left CCA, and the left subclavian artery)

Septum – measurement should be s/b <4mm. the septum has 2 parts – PRIMA and SECONDUM, if the secondum is missing, the base at the atrium will look flat

Pulmonary artery (bifurcation)

Ductal arch (looks like golf club, whereas the aortic arch has more of a candy cane shape)

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Fetal circulation

Oxygenated blood enters the fetus through the umbilical vein

The ductus venosus partially bypasses the lever to send oxygen – rich blood to the right ventricle

The foramen ovale shunts some of the right atrial blood directly into the left atrium

The ductus arteriosus allows oxygen-rich blood from the pulmonary artery into the aortic arch to circulate throughout the fetus

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Ductus Venosus: In the fetus, the ductus venosus shunts approximately half of the blood flow of the umbilical vein directly to the inferior vena cava. Thus, it allows oxygenated blood from the placenta to bypass the liver. In conjunction with the other fetal shunts, the foramen ovale and ductus arteriosus, it plays a critical role in shunting oxygenated blood to the fetal brain

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Foramen Ovale: a shunt from the right atrium into the left atrium

 

Ductus Arteriosus: a shunt connecting the pulmonary artery to the aortic arch. It allows most of the blood from the right ventricle to bypass the fetus's fluid-filled lungs

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The fetal circulation, labeling the Foramen ovale, ductus arteriosus, and ductus venosus. 

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Blood flow through the heart is proportioned as follows:

60% of right atrial blood passes through the foramen ovale, into the left atrium, and into the systemic circulation.

40% of right atrial blood enters the right ventricle:

92% of main pulmonary artery volume bypasses the lungs via the ductus arteriosus and into the system circulation

8% of the ventricular blood reaches the lungs

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Fetal echocardiography

In addition to creating two-dimensional pictures of the cardiovascular system, a fetal echocardiogram can also produce accurate assessment of the velocity of blood and cardiac tissue at any arbitrary point using pulsed or continuous wave Doppler ultrasound. This allows assessment of cardiac valve areas and function, any abnormal communications between the left and right side of the heart, any leaking of blood through the valves (valvular regurgitation).

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Fetal Echocardiography is used to diagnose fetal cardiovascular diseases. It can provide a wealth of helpful information, including the size and shape of the heart, its pumping capacity and the location and extent of any damage to its tissues.

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Heart

A 4 chamber view should be visualized

Includes the RA, LA, RV, and LV

The rt. & lt. pulmonary vein, descending aorta, and lungs may also be visualized

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Four chamber view

The 4cv is the single most important image of the fetal heart.

Normal features are:

Apex of heart points 45 degrees to left anterior chest wall

Ventricles approx. the same size (right can be larger than left in pregnancy)

Flap of foramen of ovale opens into left atrium

Prominent moderator bands present in apex of right ventricle

Valves separate both atria from ventricles

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The normal 4-chamber view

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Normal orientation of the 4 chamber heart view within the fetal chest: the heart should take up 1/3 of the chest cavity with the apex pointing to the left chest wall.

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LVOT

Left ventricular outflow tract view (LVOT)

ID origin of aorta from the left ventricle

Sagittal section shows aortic arch and its branches

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LVOT diagram

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LVOT

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LVOT

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Right ventricular outflow tract view (RVOT)

ID the origin of pulmonary trunk from the right ventricle

Correct orientation of pulmonary trunk is draping anterior to the aorta when seen in cross section.

Diameter of the pulmonary artery is 9% larger than that of the aorta

 

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RVOT diagram

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RVOT

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Structural Cardiac Anomalies 

Atrial Septal Defect (ASD)

Any abnormal opening between the atria is referred to as an atrial septal defect. ASDs are associated with a variety of cardiac and chromosomal abnormalities. Diagnosis is difficult because of the normal patent foramen ovale.

Sonographic findings:

Relies on demonstration of echo dropout at the level of atrial septum

Since foramen ovale is normally open, prenatal diagnosis is unlikely.

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Because of the high pressure in the left ventricle (needed to pump the blood around the body), blood is forced through the holes in the septum (central heart wall) when the ventricle contracts, thus increasing the pressure in the right ventricle. This increased pressure (pulmonary hypertension) results in excess blood flow to the lungs.

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ASD- Atrial septal defect

Any abnormal opening between the atria is an ASD.

Hard to diagnosis because of the normal patent foramen ovale.

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ASD diagram

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ASD ultrasound- False Positive

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Ventricular Septal Defect (VSD)

Ranks first in frequency of all cardiac anomalies. Caused by incomplete closure of interventricular IIV) foramen and failure of the membranous part of IV septum. VSDs are the most teratogen-associated fetal defect, and are associated with other cardiac anomalies 50% of the time.

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Sonographic findings:

Demonstration of an opening between the ventricles on 4 chamber view

Bidirectional flow demonstrated with color Doppler

Larger defects are easier to diagnosis.

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A

ventricular septal defect

(

VSD

) is a defect in the ventricular septum, the wall dividing the left and right ventricles of the heart.

Congenital VSDs are collectively the most common congenital heart defects.

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Ventricular septal defect (VSD)

Ranks first in frequency of all cardiac anomalies

Opening between the two ventricles

Commonly caused by a teratogen-associated fetal defect.

Associated with other cardiac anomalies 50% of the time.

Seen by demonstrating an opening between the ventricles on a 4 chamber view

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VSD

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VSD

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Hypoplastic Right Heart Syndrome

Generally occurs secondary to pulmonary atresia, with an intact interventricular septum.

Sonographic findings:

Absent or markedly small right ventricle on 4 chamber view

Absent or small pulmonary artery

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Hypoplastic right heart syndrome

Absent or markedly small right ventricle on 4 chamber view

Absent or small pulmonary trunk

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Hypoplastic Right Heart

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Hypoplastic Right Heart Ultrasound

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Hypoplastic Left Heart Syndrome

A small left ventricle results from decreased blood flow into or out of the left ventricle. The primary abnormalities include aortic atresia, aortic stenosis (coartation of the aorta is present in 80% of cases), and mitral valve atresia.

Sonographic findings:

Absent or markedly small left ventricle on 4 chamber view

Hypoplastic or aortic mitral valve and aorta.

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Hypoplastic left heart syndrome (also known as HLHS

), is a rare congenital heart defect in which the left side of the heart is severely underdeveloped.

While many authorities believe the cause of HLHS is unknown, recent research indicates that HLHS may be due to genetic factors.

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In babies with HLHS, the aorta and left ventricle are very small, and the aortic and mitral valves are either too small to allow sufficient blood flow or are closed altogether. As blood returns from the lungs to the left atrium, it must pass through an atrial septal defect to the right side of the heart.

In a healthy human, the left side of the heart receives oxygen-rich blood from the lungs and pumps it out to the rest of the body; with these structures underdeveloped, they cannot circulate blood to other organs, and the right ventricle must pump blood to both the lungs, as it would normally, and to the rest of the body, a situation which cannot be sustained for long.

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In cases of HLHS, the right side of the heart often must pump blood to the body through a patent ductus arteriosus. As the ductus arteriosus usually closes within eleven days after birth, blood flow is severely restricted and eventually cut off, leading to dangerously low circulation and eventually to shock.

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Hypoplastic left heart syndrome

Absent or markedly small left ventricle on a 4 chamber view.

Hypoplastic mitral valve and aorta

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Hypoplastic Left Heart

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Hypoplastic Left Heart Ultrasound

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Large VSD

Homework: Submit an image of a Large VSD

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Large ASD

Homework: Submit an image of a True positive large ASD

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Hypoplastic Right Heart

Homework: Submit an image of a Hypoplastic Right heart

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Hypoplastic Left Heart

Homework: Submit an image of a Hypoplastic Left Heart.

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Transposition of the Great Arteries

TGA

The origin of the great vessels are transposed so that the aorta arises from the right ventricle and the pulmonary trunk arises from the left ventricle. A variety of other cardiac anomalies are associated with TGA.

 

Sonographic findings

Correct right-left orientation is a MUST

Images of outflow tracts demonstrate anomalous origin of great arteries

Difficult sonographic diagnosis

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TGA diagram

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TGA Ultrasound The ascending aorta  and the pulmonary artery  are parallel to each other.

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Transportation of the Great Arteries (TGA)

Once again,

The origin of the great vessels are transposed so that the aorta arises from the right ventricle (instead of the left ventricle) and the pulmonary trunk arises from the left ventricle ( instead of the right ventricle)

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Truncus Arteriosus

A single large vessel arises from the base of the heart. A VSD is usually present, and 48% of fetuses have other noncardiac anomalies.

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Truncus Arteriosus diagram

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Double Outlet Right Ventricle

Both the pulmonary artery and the aorta arise from the right ventricle. This defect is associated with other cardiac defects, maternal diabetes, and maternal alcohol consumption.

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Double Outlet Right Ventricle

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Ectopia Cordis

In ectopia cordis, all or part of heart is located outside of chest cavity. It is frequently associated with intra-cardiac anomalies and omphalocele in Pentalogy of Cantrell.

Sonographic Findings:

Small thorax

Extension of soft tissue outside thoracic cavity in which cardiac activity is noted.

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Ectopia Cordis (full)

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Ectopia Cordis (partial)

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Cardiac Tumors

Cardiac tumors are rare, and include rhabdomyomas, cardiac fibromas, myxomas and teratomas. 30-78% of patients with cardiac rhabdomyomas have tuberous sclerosis. Prognosis depends on the size, number and location of the tumor(s), as well as associated arrhythmias and anomalies.

 

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Fetal Cardiac Tumor

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Other Cardiac Anomalies

Some other conditions that can be diagnosed using ultrasound:

Endocardial Cushion Defects

Atrial and ventricular septal defects resulting from failure of the common AV orifice to separate into mitral and tricuspid valves. Associated with an increased risk of Trisomy 21.

Tetralogy of Fallot

Consists of four anatomic abnormalities: Large VSD, overriding aorta, pulmonary infundibular stenosis, right ventricular hypertrophy.

Ebstein’s Anomaly

Downward displacement of the septal and posterior leaflets of the tricuspid valve

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Endocardial cushion defect is also called atrioventricular septal defect (AVSD). AVSD involves problems with the structure of the heart. The heart normally has 2 upper chambers (atria) and 2 lower chambers (ventricles). A normal heart also has 2 heart valves (the tricuspid and mitral valves) that separate the upper and lower chambers.

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In AVSD, there may be a large hole in the center of the heart where the wall (septum) joins the upper and lower chambers of the heart. The tricuspid and mitral valves may not be separate. Instead, there can be one large valve between the upper and lower chambers of the heart (common atrioventricular valve). The large opening in the center of the heart allows the oxygen-rich (red) and the oxygen-poor (blue) blood to mix. The heart pumps blood in a way that is not efficient and becomes enlarged.

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An AVSD is the most common congenital heart defect found in children with Down's Syndrome, accounting for 50% of the total.

In its complete form there is a hole in the wall between the top chambers (atria) and a hole in the wall between the bottom chambers (ventricles), and one common valve between the two atria and the two ventricles. In the partial forms there may not be a hole between the bottom chambers (ventricles) or the mitral and tricuspid valves may not be joined together, but either or both may leak, known as valve incompetence.

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Endocardial Cushion Defects

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Tetralogy of Fallot

The

tetralogy of Fallot

(TOF) is a congenital heart defect which classically has four anatomical components. It is the most common cyanotic heart defect and the most common cause of blue baby syndrome.

It was described in 1672 by Niels Stensen and in 1888 by the French physician Etienne Fallot, for whom it is named.

As classically described, tetralogy of Fallot involves four heart malformations which present together:

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1.A

ventricular septal defect (VSD)

: a hole between the two bottom chambers (ventricles) of the heart. The defect is centered around the 'outlet septum', the most superior aspect of the septum, and in the majority of cases is single and large. In some cases septal hypertrophy can narrow the margins of the defect

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2.Pulmonic stenosis

: Right ventricular outflow tract obstruction, a narrowing at (valvular stenosis) or just below (infundibular stenosis) the pulmonary valve. The stenosis is the major cause of the malformations, with the other associated malformations acting as compensatory mechanisms to the pulmonic stenosis. The degree of stenosis varies between individuals with TOF, and is the primary determinant of symptoms and severity. This malformation is infrequently described as

sub-pulmonary stenosis

or

subpulmonary obstruction

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3.Overriding aorta

: An aortic valve with biventricular connection, that is, it is connected to the right ventricle as well as the left ventricle. The degree to which the aorta is attached to the right ventricle is called "override." The aortic root can be displaced anteriorly or it can override the septal defect, but it is still to the right of the root of the pulmonary artery. The degree of override is quite variable, with 5-95% of the valve being connected to the right ventricle.

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4.Right ventricular hypertrophy

: The right ventricle is more muscular than normal, causing a characteristic boot-shaped appearance as seen by chest X-ray. Due to the misarrangement of the external ventricular septum, the right ventricular wall increases in size to deal with the increased obstruction to the right outflow tract. This feature is now generally agreed to be a secondary anomaly, as the level of hypertrophy generally increases with age.

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There is anatomic variation between the hearts of individuals with tetralogy of Fallot. The degree of right ventricular outflow tract obstruction varies between patients and generally determines clinical symptoms and disease progression.

Tetralogy of Fallot occurs in approximately 3 to 6 per 10,000 births and represents 5-7% of congenital heart defects. Its cause is thought to be due to environmental or genetic factors or a combination. It is associated with chromosome 22 It occurs slightly more often in males than in females.

Tetralogy of Fallot results in low oxygenation of blood due to mixing of oxygenated and deoxygenated blood in the left ventricle through the VSD and preferential flow of both oxygenated and deoxygenated blood from the ventricles through the aorta because of obstruction to flow through the pulmonary valve. This is known as a right-to-left shunt.

 

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Tetralogy of Fallot

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Tetralogy of Fallot

4 anatomic abnormalities

Large VSD

Overriding aorta

Pulmonary stenosis

Right ventricular hypertrophy

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Ebstein's anomaly

 

Ebstein's anomaly

is a congenital heart defect in which the opening of the tricuspid valve is displaced towards the apex of the right ventricle of the heart.

This causes the right atrium to be large and the anatomic right ventricle to be small in size.

There may be an increased risk of this abnormality in infants of women taking lithium during the first trimester of pregnancy

While Ebstein's anomaly is defined as the congenital displacement of the tricuspid valve towards the apex of the right ventricle, it is often associated with other abnormalities

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Ventricular hypertrophy

In utero - hypertrophy is most commonly associated with cardiac outlet obstruction but may be associated with maternal diabetes.

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Ventricular hypertrophy

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Left Ventricular Hypertrophy

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Cardiac Arrhythmias

In the first trimester, cardiac rates vary with gestational age. Prior to six weeks the rates is relatively slow, typically between 100-115 BPM. After six weeks, cardiac rate increases rapidly, and by eight weeks is between 144-159 BPM. After nine weeks the rate plateaus at 137-144 BPM.

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Premature atrial and ventricular contractions

Premature contractions are entirely benign arrhythmias in most cases. Most disappear in utero or in early neonatal period.

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Tachycardia

Fetal tachycardia is a heart rate greater than 180 BPM. Most have a good prognosis, and are treated in utero with various pharmacological agents.

 

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Tachycardia

refers to rapid beating of the heart. By convention it defined as a heart rate greater than 100 beats per minute in adults. Tachycardia may be normal, such as in exercise and stress, or abnormal, such as in cardiac arrhythmias. However, depending on the mechanism of the tachycardia and the health status of the person, tachycardia may be harmful and require medical treatment. In extreme cases, tachycardia can be life threatening

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Tachycardia can be harmful in three ways. First, if the heart is pumping too fast for an extended period of time it will change the balance of oxygen and carbon dioxide in the hemoglobin in the blood; this is normal during exercise but when resting this is quite dangerous. Second, when the heart beats too rapidly, it may pump blood less efficiently as there is less time for the myocardium to relax between contractions. Third, the faster the heart beats, the more oxygen and nutrients the heart requires. This may leave patients feeling out of breath or cause angina in those suffering from ischemic heart disease

 

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Bradycardia

Fetal bradycardia is a prolonged heart rate of less than or equal to 100 BPM. Transient bradycardia can be related to an increase in intrauterine pressure. Below 80 BPM, bradycardia may be associated with fetal asphyxia. Persistent bradycardia may warrant early delivery.

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Bradycardia

, as applied to adult medicine, is defined as a resting heart rate of under 60 beats per minute, though it is seldom symptomatic until the rate drops below 50 beat/min.

The term

relative bradycardia

is used to explain a heart rate that, while not technically below 60 beats per minute, is considered too slow for the individual's current medical condition.

.

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Pericardial effusion

“Fluid around the heart" is an abnormal accumulation of fluid in the pericardial cavity. Because of the limited amount of space in the pericardial cavity, fluid accumulation will lead to an increased intrapericardial pressure and this can negatively affect heart function. When there is a pericardial effusion with enough pressure to adversely affect heart function, this is called cardiac tamponade. Pericardial effusion usually results from a disturbed equilibrium between the production and re-absorption of pericardial fluid, or from a structural abnormality that allows fluid to enter the pericardial cavity.

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Pericardial Effusion-Subtle

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Pericardial Effusion-Severe

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Homework

What are the indications for a fetal echocardiogram? Include the abnormal findings and the risk factors.

What are the normal findings associated with a four-chamber view?

List the normal orientation of the four-chamber view within the fetal chest.

Draw a normal four-chamber view.

List the checklist of a normal fetal cardiac study.

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Define Aortopulmonary transportation.

Define pulmonary atresia

What is the corrected transposition of the great vessels?

Regarding Fetal cardiac arrhythmias: give the rates for normal, slow, and fast.

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1. A four chamber view of the fetal hart demonstrates some important anatomic features. Name as may as you can.

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2. What is the purpose of the left ventricular outflow tract view?

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3. What is the purpose of the right ventricular outflow tract view?

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4. True or False. The ductus venosus bypasses some of the oxygenated fetal blood from the liver to the inferior vena cava

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5. True or False. A normal opening between the right and left atria shunts fetal blood from the right to left heart, in order to bypass the lungs and direct it to the systemic circulation.

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6. True or false. The opening between the two atria of the hart is called the ductus arteriosus.

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7. True of false. The foramen ovale cannot be seen sonographically on a four chamber view of the heart.

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8. Why is an atrial septal defect difficult to diagnosis sonographically?

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9. Which cardiac defect is the most teratogen-associated fetal defect?

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10. What is hypoplastic right heart syndrome? How does it appear sonographically?

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11. What is hypoplastic left heart syndrome? How does it appear sonographically?

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12. True or False. Transposition of the great arteries (TGA) can be diagnosed with a good four chamber view of the heart.

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13. Define transposition of the great arteries (TGA)

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14. What is ectopia Cordis?

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15. With what is ectopia cordis associated?