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Evaluation of the infant, child, or young adult with cardiovascular symptoms may require the application of a variety of cardiac tests. Each of these tests has specific indications that provide unique information for characterization of a particular problem, but these tests also have limitations. Adding various tests allows for the layering of information until a rich composite model of the cardiovascular structure and function is built. This allows for optimal understanding of the condition and the implementation of the most appropriate and efficient care.
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In this chapter, we review 4 fundamental types of noninvasive cardiac testing: electrocardiography, exercise/cardiopulmonary stress testing, echocardiography, and cardiac magnetic resonance imaging.
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The Pediatric Electrocardiogram
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Introduction to the Pediatric Electrocardiogram
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Electrocardiography has always been one of the fundamental procedures used in the diagnosis and treatment of cardiac disease ever since Einthoven first recorded the heart's electrical activity in 1901 using a string galvanometer. Information gained from the electrocardiogram (ECG) can be used to help determine the cardiac anatomy, the cardiac rhythm and electrical conduction, and the effect of therapeutic interventions on cardiac electrical activity. Since the advent of echocardiography, a pediatric cardiologist rarely depends on the ECG to accurately predict the cardiac anatomy. However, the ECG is indispensable in the evaluation of a child with a suspected cardiac rhythm abnormality. It is now well recognized that some medications may significantly alter the heart's electrical properties to the point that it places the patient at increased risk for sudden cardiac death, usually from a form of polymorphic ventricular tachycardia known as torsade de pointes. As such, screening and serial ECGs are indicated. Although still an area of controversy in the United States, there are proponents who say that an ECG should be included in the preparticipation sports evaluation and before the initiation of stimulant medication for attention-deficit hyperactivity disorder.1-4 Although today's ECG machines are smaller, portable, and readily available, the waveforms they produce are not different than those seen by Einthoven over a century ago.
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Basic Concepts and the Approach to the Pediatric ECG
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For a complete description of the ECG, the reader is referred to the many textbooks devoted exclusively to ECG interpretation. The basic 12-lead ECG includes the limb leads I, II, III, aVR, aVL, and aVF plus the precordial leads V1 to V6. Because most pediatric cardiologists see children with anatomically abnormal hearts, the typical pediatric ECG records 15 leads, the additional 3 being lead V3R, V4R, and V7 (Figure 2-1). The different leads that are used in the ECG provide unique perspectives for the evaluation of the electrical system of the heart as a whole. This concept is represented by the hexaxial reference system and the horizontal reference system (Figure 2-2). In the hexaxial system, the limb leads represent different degrees of orientation ...