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The purpose of cardiovascular electrophysiologic mapping is to define the anatomic sequence of myocardial activation, both at baseline and/or with arrhythmia. There have been tremendous technologic advances in this area1 that have created fertile ground for the integration of multiple imaging modalities. High-level integration begins with preprocedural assessment of electrophysiologic properties revealed by the 12-lead surface electrocardiogram (ECG) viewed in the context of patient demographics and history.2,3 Further information is added during invasive electrophysiologic mapping with assessment of intracardiac electrograms viewed in the context of cardiac anatomy.4,5 The fusion of functional electrophysiologic data with anatomic data in the electrophysiology laboratory facilitates catheter navigation, data annotation, and direct visualization of target sites for therapy. Following an invasive electrophysiologic mapping procedure, there are likewise multiple imaging modalities useful for assessing response to therapy, excluding complications, and directing future diagnostic and therapeutic decisions.6
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Baseline 12-Lead ECG and Patient History
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The efficiency and effectiveness of an invasive electrophysiologic mapping procedure are dependent on the preprocedure evaluation. Patient demographics, history, and 12-lead surface ECG both at baseline and with arrhythmia help determine what diagnoses are possible and, among the possible, which are most likely. The 12-lead ECG is among the oldest and most useful imaging modalities for localizing arrhythmia origin and characterizing arrhythmia mechanism. The 12-lead ECG provides imaging by display of vectorial information contained in the body surface voltage pattern viewed from different leads, each viewing the heart from a different perspective or "angle." Tachycardia occurring in a female in her forties with a superior P wave axis, short RP interval, with a narrow QRS complex is most likely atrioventricular nodal re-entrant tachycardia.7 A younger male with tachypalpitations originally presenting in adolescence may have an ECG that looks similar; however, based on demographics, atrioventricular re-entrant tachycardia via an accessory pathway may be more likely8 (Fig. 8–1). A patient with a history of right atriotomy might have findings of typical right atrial flutter (ie, negative "sawtooth-shaped" flutter waves in the inferior leads and positive flutter waves in the anterior precordial leads) on the 12-lead ECG; however, the patient might also have right lateral wall atrial flutter encircling the atriotomy scar. These arrhythmias may present simultaneously or sequentially (Fig. 8–2). The probability of directing one's attention to the appropriate substrate is favored by a thoughtful preprocedure analysis.
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