Tet spells
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Tetralogy of fallot Microchapters |
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Treatment |
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Tet spells On the Web |
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American Roentgen Ray Society Images of Tet spells |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Children with Tetralogy of Fallot may develop acute severe cyanosis or hypoxic "tet spells". The spells are unpredictable and are associated with profound cyanosis and can be fatal.
Pathophysiology
The mechanism underlying these episodes is not entirely clear, but may be due to spasm of the infundibular septum and the right ventricular outflow tract. Whatever the mechanism, there is an increase in resistance to blood flow to the lungs with increased preferential flow of desaturated blood to the systemic circulation. The child will often squat during a Tet Spell to improve venous return to the right side of the heart. Squating increases the systemic vascular resistance and thereby shunts flow to pulmonary circuit.
Prognosis
These spells can be fatal, and can occur in patients who are not cyanotic.
Emergency Medical Management of Tet Spells
'Tet spells' cause acute hypoxia and may be treated with:
- Beta-blockers such as propranololor esmolol. The beta-blockers causes relaxation of the right ventricular outflow tract and increases blood flow into the pulmonary vessels
- Morphine to reduce ventilatory drive
- Phenylephrine to increase systemic afterload that in turn increases the flow across right ventricle and the pulmonary artery and decreases right to left shunting
- Procedures such as the knee-chest position which increases aortic wave reflection, increasing pressure on the left side of the heart, decreasing the right to left shunt thus decreasing the amount of deoxygenated blood entering the systemic circulation.[1]
- Oxygen is ineffective in treating hypoxic spells as the underlying problem is lack of blood flow through the pulmonary circuit and not alveolar oxygenation.
- In case all these measures fail, an emergency Blalock-Taussig shunt might be needed.