|CURRENT Diagnosis & Treatment: Pediatrics|
Chapter 19. Cardiovascular Diseases
Disorders of Atrioventricular ConductionShelley D. Miyamoto, MD, Henry M. Sondheimer, MD, Thomas E. Fagan, MD, Kathryn K. Collins, MD
Sections: Syncope (Fainting).
Excerpt:"The atrioventricular node is the electrical connection between the atrium and the venticles. Atrioventricular blocks involve a slowing or disruption of this connection and are described according to the degree of this slowing or disruption.The primary finding in infants and children with complete atrioventricular block is a significantly low heart rate for age. The diagnosis is often made prenatally when fetal bradycardia is documented. An ultrasound is then conducted as well as a fetal echocardiogram of the heart. With the fetal echocardiogram, atrial and ventricular contractions can be distinguished and the atrial rate is documented as being higher than the ventricular rate with no relationship to each other. If the heart rates are sufficiently low, then there will be low cardiac output, decreased cardiac function, and the development of hydrops fetalis. Postnatal adaptation largely depends on the heart rate; infants with heart rates less than 55 beats/min are at significantly greater risk for low cardiac output, HF, and death. Wide QRS complexes and a rapid atrial rate are also poor prognostic signs. Most patients have an innocent flow murmur from increased stroke volume. In symptomatic patients, the heart can be quite enlarged, and pulmonary edema may be present...."
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