July 15, 2010

Q&A: X-ray Diagnosis of Congenital Heart Disease

Congenital heart disease (CHD) is the most common congenital disorder in newborns. Critical CHD, defined as requiring surgery or catheter-based intervention in the first year of life, occurs in approximately 25 percent of those with CHD. Although many newborns with critical CHD are symptomatic and identified soon after birth, others are not diagnosed until after discharge from the birth hospitalization. In infants with critical cardiac lesions, the risk of morbidity and mortality increases when there is a delay in diagnosis and timely referral to a tertiary center with expertise in treating these patients.

This article is for Medical Students & Professionals
This is a Question & Answer revision article designed for medical students and professionals preparing for the PLAB, MRCP or USMLE examinations. They are based on actual questions from these examinations. You may find the Cardiovascular Disease article more useful, or one of our many articles on Diseases & Conditions, Medical Syndromes, Health & Wellness or Home Remedies.
In this article:
Congenital heart disease
MCQ exam: clinical scenario
MCQ exam: answer
MCQ exam: explanation

Congenital heart disease

Congenital heart disease (CHD) can be characterized as:
  • Cyanotic CHD − Cyanotic CHD includes lesions that allow circulation of deoxygenated blood in the systemic circulation via intracardiac or extracardiac shunting. For example, transposition of the great arteries (TGA), tetralogy of Fallot (TOF), truncus arteriosus, total anomalous pulmonary venous connection (TAPVC), and tricuspid valve abnormalities;
  • Ductal-dependent CHD − Ductal-dependent congenital heart lesions are dependent upon a patent ductus arteriosus (PDA) to supply pulmonary or systemic blood flow or to allow adequate mixing between parallel circulations. In critical right heart obstructive lesions, the PDA is necessary to supply blood flow to the lungs; in critical left heart lesions, the PDA supplies systemic circulation; and in parallel circulations (eg, transposition of the great arteries), bidirectional flow in the PDA allows mixing between oxygenated and deoxygenated circuits. Many, but not all, cyanotic congenital heart defects are ductal-dependent.
  • Critical CHD − Critical CHD refers to lesions requiring surgery or catheter-based intervention in the first year of life. This category includes ductal-dependent and cyanotic lesions as well as forms of CHD that may not require surgery in the neonatal period but still require intervention in the first year of life, such as a large VSD or an atrioventricular (AV) canal defect (or AV septal defect) or a critical coarctation of the aorta (COA). Critical CHD accounts for approximately 25 percent of all CHD.

MCQ exam: clinical scenario

Study the slide below carefully, and answer the question beneath:

MCQ question on medicalnotes.info

What is the most likely diagnosis?

a) Ventricular septal defect
b) Patent ductus arteriosus
c) Coarctation of aorta
d) Supravalvular aortic stenosis
e) Pulmonary valve stenosis

MCQ questions & answers on medicalnotes.info

MCQ exam: answer

The correct answer is C.
Slide is a chest x-ray showing classic features of aortic coarctation.
The PA chest radiograph shows bilateral rib notching (rib 5-8) with figure-3 sign and significant post-stenotic dilation of the descending aorta.

MCQ exam: explanation

Coarctation in the adult is characterized by a short segment abrupt obstruction in the postductal region secondary to localized thickening of the aortic media. This typically occurs just distal to the ductus or ligamentum arteriosum. Infantile coarctation or preductal coarctation is characterized by a diffuse narrowing or hypoplasia of the aorta also in the presence of a discrete area of constriction in the aorta just beyond the origin of the left subclavian artery but proximal to the ductus arteriosus, hence distal blood supply is fulfilled via the ductus. Typical coarctation are those cases in which there is diffuse hypoplasia of the transverse arch in association with a discrete isthmic narrowing.

Coarctation accounts for between 5-8% of all congenital heart defects. The male:female ratio is between 2-3:1 with an increased predisposition in girls with Turner’s syndrome (15-20%).

Coarctation of the aorta has the following associations: (1) Bicuspid aortic valve occurs in up to 85% of cases. (2) Ventricular septal defect (all types). (3) Mitral valve lesions including hypoplastic mitral valve, parachute mitral valve, and abnormal papillary muscles. (4) Shone’s syndrome (multiple left sided obstructions; supravalvular mitral ring, mitral valve stenosis, subaortic membrane/stenosis, aortic valve stenosis, coarctation). (5) Cyanotic congenital lesions including truncus arteriosus and transposition of the great arteries, especially with a subpulmonic VSD and overriding pulmonary artery (Taussig-Bing).

Physical findings: In later life characteristic features are upper limb hypertension with reduced or absent femoral impulses. Hypertension may not directly reflect the severity of the obstruction. If there is a higher left upper limb blood pressure relative to right, one should consider the possibility of an abberant right subclavian artery. The upper torso may be well developed relative to the lower torso. In infants there is less tendency to severe hypertension and the development of collaterals. There may be a thrill in the suprasternal notch. An ejection systolic murmur may be heard in the left upper sternal region, with an ejection click if there is an associated bicuspid aortic valve. The back should be palpated for the presence of collaterals and ausculted for continuous murmurs. Fundoscopic exam in older patients may yield evidence of hypertensive changes.

ECG: Often normal in early stages progressing to left ventricular hypertrophy. 50% of older patients may develop RBBB.

CXR: Characteristic features include post-stenotic dilation of the descending aorta, "figure 3" sign, and the development of rib notching secondary to dilated intercostal collateral vessels. This is reported in 70% patients between 6-41 years. It is extremely rare in infancy. Unilateral notching should alert one to the presence of ipsilateral anomalous subclavian artery arising below the coarctation (low pressure system, hence no collaterals).

Reference(s)
1). UptoDate: Identifying newborns with critical congenital heart disease. Available online: https://www.uptodate.com/contents/identifying-newborns-with-critical-congenital-heart-disease
2). UptoDate: Cardiac causes of cyanosis in the newborn. Available online: https://www.uptodate.com/contents/cardiac-causes-of-cyanosis-in-the-newborn
3). Baylor College of Medicine (Texas Children's Hospital): Plain radiographic diagnosis of congenital heart disease. Available online: https://www.bcm.edu/radiology/cases/pediatric/start.htm

No comments:

Post a comment

Got something to say? We appreciate your comments: