Congenital Heart Disease

Ductal-dependent lesions
-Most important to recognize in early neonatal period (ductus closes within 3 weeks of life)
-Subdivide into cyanotic and noncyanotic lesions based on presentation
Cyanotic lesions = obstruction of right heart flow to lungs – patent ductus needed to get blood to lungs
Noncyanotic lesions = obstruction of left heart flow to body – patent ductus needed to get blood to body

Note: if pt has known PDA, find out if isolated or along with other lesions

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Diagnosis:
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Exam: cool shock presentation + crackles and hepatomegaly

Pulse Delay or Absence: Decreased or absent femoral pulses may suggest coarctation of the aorta

Brachial-femoral pulse differential: pulses should arrive at the brachial and femoral pulse simultaneously, if there is a brachial-femoral delay there may be an issue

Blood pressure differential: Difference between preductal (i.e. right arm) blood pressure and lower extremity blood pressure of > 10 mmHg, think of an obstructive process to the lower extremities.

O2 saturation differential: Difference in O2 saturation > 3% between right upper and right lower extremity, <94% in lower extremities, or < 90% in any extremity are considered clinically significant

Labs:

  • Blood glucose (ABC Don’t Ever Forget Glucose)
  • Electrolytes (to assess for adrenal insufficiency)
  • Septic work-up
  • Methemoglobin if cyanosis without respiratory distress
  • Ammonia (metabolic diseases)
  • TSH
  • BNP: ongoing debate about usefulness of this test, particularly in the ED setting.
    • BNP < 100pg/mL to identify significant congenital heart disease had a sensitivity of 100% and specificity of 98%
    • BNP > 132.5pg/mL to detect hemodynamically significant left-to-right shunts had a 93% sensitivity and 100% specificity
    • BNP > 40pg/mL to differentiate cardiac from pulmonary causes of respiratory distress had an accuracy of 84%

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-compare PaO2 of ABG drawn from right radial artery (preductal) before and after 10m of supplemental O2
-CHD pts do not have significant increase (post hyperoxia PaO2 unlikely over 150mmHg), whereas pts with pulmonary disease will  have some improvement of V/Q mismatch

*The hyperoxia test: A simpler method involves using a pulse oximeter before and after the patient receives 100% oxygen (or as close to a 100% FIO2 as possible) for 5-10 minutes and noting whether or not the oxygen saturation improves. If the oxygen saturation improves then the underlying cause of the oxygen desaturation favours a respiratory etiology, whereas if the oxgygen saturation does not improve, a cardiac cause is favoured.

Caution! 100% oxygen is a pulmonary vasodilator and could worsen respiratory distress in a patient with ductal-dependent lesions, by decreasing PVR and increasing pulmonary blood flow, leading to pulmonary over-circulation

With bedside ECHO, ask yourself 3 simple questions:

  1. Is the global cardiac function poor?
  2. Are there four chambers of the heart?
  3. Is the septum intact?

Management of Blue Babies:
-if clinically suspect ductal-dependent lesion, give prostaglandin E1 immediately at 0.05-0.1 mcg/kg/min to maintain patent ductus arteriosus
-be prepared to intubate (apnea common) and support hemodynamics as a result of administration and in preparation for transport to hospital with peds cardiac surgery
-use etomidate or fentanyl for induction (do NOT use ketamine – the increase in afterload may cause decompensation!). Use low PEEP settings.
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Any neonate in distress should be presumed to be septic until proven otherwise. Early empiric antibiotics should be started as soon as possible.

Be judicious with fluids. Use 5-10 cc/kg NS boluses to improve preload, and encourage further opening of the PDA and pulmonary blood flow through the duct. Give Oxygen. Aim for an oxygen saturation of 85% (depending on diagnosis and lesion). The use of sodium bicarbonate is controversial. It may be given empirically based on the blood gas, as acidosis aggravates hypoxic pulmonary vasoconstriction. Inotropes/vasopressors may be necessary to maintain adequate systemic perfusion and encourage pulmonary perfusion in consultation with a pediatric intensivist.

*The tachypneic infant who appears to be struggling to breath (i.e. increased work of breathing) usually has an underlying respiratory cause vs. the infant who is displaying ‘silent tachypnea’, without increased work of breathing is usually secondary to metabolic acidosis from a cardiac or metabolic cause.

The big 4 Causes of Neonatal Cyanosis

  1. Congenital Heart Disease
  2. Sepsis
  3. Respiratory disorders (i.e., pneumonia, ARDS)
  4. Hemaglobinopathy (i.e., polycythemia, methemoglobinemia)

To distinguish central cyanosis from peripheral cyanosis, look for bluish discoloration inside the mouth – tongue, mucous membranes and lips.

 

Pink Perfused Babies (1-6mo/o):
-consider CHF for wheezing baby!

The most sensitive and specific clinical findings for acute CHF in infants

  • < 3 ounces of formula per feed or > 40 minutes per breast feed
  • Respiratory rate > 60 breaths per minute or irregular breathing
  • Hepatomegaly – Start palpation at the iliac crest and slowly move superiorly, and feel for the liver edge. Normally, the liver edge should be < 2 cm below the costal margin. Also percuss for the size of the liver – normally, the liver should be < 8 cm wide.
  • Other clues: poor weight gain & ventricular hypertrophy on ECG

Common causes of CHF in the pediatric patient include structural causes such as VSD, ASD, Aortic Stenosis and PDA as well as other causes such as SVT, AV block, cardiomyopathy and myocarditis.

Management:
-oxygen is a potent pulmonary vasodilator and could worsen hypoxemia in some congenital heart defects. Infants are able to tolerate oxygen saturations lower than adults and so aim for an oxygen saturation of >85% (as opposed to >93% in adults)
-lasix for pulmonary edema
-inotropes or vasodilators (i.e., milrinone, dobutamine) may be indicated in severe CHF in consultation with the pediatric intensivist

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