Abnormal Cardiac Axis

Anne Kennedy, MD

DIFFERENTIAL DIAGNOSIS

Common

Chest Mass
- Congenital Diaphragmatic Hernia
- Cystic Adenomatoid Malformation
- Bronchopulmonary Sequestration
- Pleural Effusion
- Teratoma
Cardiac
- Chamber Asymmetry
- Conotruncal Malformation
- Heterotaxy, Cardiosplenic Syndromes

Less Common

Pulmonary Agenesis

Rare but Important

Ectopia Cordis

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Important to have systematic approach
In all OB scans check fetal orientation
- Which is the fetal anatomic left and right?
Check position of stomach
Check position of cardiac apex
Stomach and cardiac apex should both be on the left
- If both on right, likely complete situs inversus with good prognosis
- If opposite sides, likely heterotaxy syndrome
  - Strong association with complex congenital heart disease
Normal four chamber view is seen on an axial image of the chest
- Ribs should be symmetric and C-shaped
Normal cardiac axis is 35° to 45°
- Draw a line from spine to sternum
- Draw a line along axis of intraventricular septum
If axis is abnormal
- Does the heart appear displaced within the thorax?
  - May be “pushed” to one side by a mass
  - May be “pulled” to one side if lung small or absent
- Ectopia cordis implies heart situated outside thorax
  - Intra-abdominal
  - Extrathoracic
- Is the internal cardiac structure normal?
  - Normal right and left atria
  - Normal right and left ventricles
  - Normal outflow tracts crossing as they exit the heart
  - Atrioventricular concordance
  - Ventriculoarterial concordance

Helpful Clues for Common Diagnoses

Congenital Diaphragmatic Hernia
- Stomach/intestine ± liver in chest
- Heart displaced away from side of hernia
  - In bilateral hernias, there may be minimal cardiac shift
- Look for peristalsis within chest
- Look for “bucket handle” motion of diaphragm on coronal view
- Strong association with aneuploidy
Cystic Adenomatoid Malformation
- Chest mass with perfusion from pulmonary artery branches
- May be uniformly echogenic to multicystic depending on type
- Heart displaced away from mass
Bronchopulmonary Sequestration
- Echogenic mass with perfusion from aorta
- Usually on left, with cardiac shift to the right side
Pleural Effusion
- Large solitary effusion may displace heart
- Look for floating lung
- Differentiate from pericardial effusion
  - Surrounds heart, displaces lung posteriorly
Teratoma
- Complex cystic/solid mass ± calcifications
Chamber Asymmetry
- Which chamber is abnormal? Or is it a single ventricle heart?
- Right heart enlargement
  - Shunt lesions with increased venous return
  - Incipient hydrops
  - Severe placental insufficiency
  - Left heart outflow obstruction
- Small right ventricle (RV)
  - Pulmonary atresia/stenosis (RV can also be normal)
  - Left dominant unbalanced atrioventricular septal defect (AVSD)
- Small left ventricle (LV)
  - Hypoplastic left heart syndrome (may have poorly functioning echogenic LV in aortic stenosis with endocardial fibroelastosis)
  - Right dominant unbalanced AVSD
- Large right atrium
  - Ebstein anomaly/tricuspid dysplasia
  - Pulmonary stenosis/atresia
Conotruncal Malformation
- Four chamber view often shows normal chambers
- Look at outflow tracts in every case
  - Single outflow: Truncus most likely if normal sized ventricles and VSD present
  - Parallel outflow tracts: Transposition of the great arteries or double outlet right ventricle
  - Large aorta overriding VSD with separate, small PA: Tetralogy of Fallot
Heterotaxy, Cardiosplenic Syndromes
- Check situs in every OB scan: Cardiac apex and stomach should be on the left
- Look for interrupted inferior vena cava with azygous continuation to the superior vena cava
  - Vessel located posterior to the aorta at the level of the diaphragm
- Look for transverse, midline liver
- Complex congenital heart disease
  - Often AV septal defect
  - Often single ventricle
  - Often abnormal outflow tracts
  - Systemic and pulmonary venous abnormalities

Helpful Clues for Less Common Diagnoses

Pulmonary Agenesis
- Heart displaced to chest wall on side of missing lung
- Diaphragm elevated but present on side of missing lung
- No evidence of diaphragmatic hernia/lung mass “pushing” heart
- Look for associated vertebral anomalies or congenital heart disease
- Look for other features of VACTERL association

Helpful Clues for Rare Diagnoses

Ectopia Cordis
- Heart in abnormal location
- Look for amniotic bands if exterior to thorax
- Pentalogy of Cantrell
  - Anterior diaphragmatic hernia
  - Midline abdominal wall defect
  - Cardiac anomalies
  - Defect of diaphragmatic pericardium
  - Low sternal defect

Other Essential Information

Prognosis in heterotaxy syndromes depends on complexity of cardiac disease
- Association with complete heart block almost uniformly fatal
Prognosis in diaphragmatic hernia depends on liver position and presence of cardiac defects
- “Liver up” or complex cardiac anomaly confers worse prognosis

Image Gallery

Axial ultrasound shows the stomach

behind the heart

, which is displaced to the right. Posterior displacement of the stomach suggests “liver up” CDH, which confers poor prognosis.

Axial T2WI MR shows bowel

and compressed lung

(which could be mistaken for liver) in the left chest with rightward heart

displacement. Coronal views proved that the liver was not in the chest.

(Left) Gross pathology shows both small bowel

and liver

in the chest. The heart

is displaced to the right. (Right) Axial ultrasound shows a large, echogenic mass with small, scattered cysts consistent with a congenital cystic adenomatoid malformation. There is marked displacement of the heart