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PROCEDURES

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RADIOFREQUENCY ABLATION

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Michael Schinlever

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Indications

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Cardiac radiofrequency (RF) ablation is the use of energy to damage specific cardiac tissue in an effort to inhibit pathologic conduction sources or tracts. Numerous arrhythmias can be treated with RF ablation. The success and complication rates of these ablations are highly dependent on the etiology of the arrhythmia and the targeted anatomic location. Arrhythmias that have a specific and localizable ectopic focus or conduction tract respond to RF ablation therapy with the highest rates of success. These include Wolf–Parkinson–White (WPW) syndrome, paroxysmal supraventricular tachycardias (AVNRT, unifocal atrial tachycardia, and accessory pathway–mediated tachycardia), type I atrial flutter, idiopathic ventricular tachycardia (VT; in structurally normal heart), and bundle branch reentrant tachycardia. On average, these carry success rates of 80% to 95% and have low rates of recurrence (<10%).

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Ablation may be indicated for patients in whom pharmacologic management has failed, significant symptoms develop, or definitive treatment is desired. Cardiac RF ablation can be employed for atypical atrial flutter, inappropriate sinus tachycardia, and junctional tachycardia. However, RF ablation has a lower success rate in treating these rhythms; therefore, it is often reserved for cases that are refractory to drug therapy. Although controversial, asymptomatic patients who have an underlying arrhythmia prone to dangerous paroxysmal changes may benefit from ablation.

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Technique

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When cardiac ablation was first developed, direct current (DC) was used. With time, techniques using different forms of energy (RF, cryotherapy, laser, and acoustic) have been developed, which provide higher success rates with fewer complications. The most common energy form used for cardiac ablation is RF. RF is a low-voltage, high-frequency energy that causes resistive heating at the catheter tip and damages focused areas of cardiac tissue. The width and depth of these resultant lesions are typically 3 to 9 mm. With different approaches (eg, femoral vein, femoral artery, internal jugular vein, or subxiphoid), a variety of target sites can be reached for ablation.

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FIGURE 9.1

This preablation ECG shows a short PR interval (82 milliseconds) and delta waves consistent with the preexcitation findings of the WPW syndrome.

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FIGURE 9.2

This postablation ECG of the same patient now shows a first-degree heart block while the preexcitation findings seen earlier are absent.

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FIGURE 9.3

This fluoroscopic image (left anterior oblique orientation) was obtained during cardiac RF ablation with multiple catheters at different sites; A is a coronary sinus electrode, B is an endocardial ablation catheter, lead C is situated at the bundle of His, and lead D is located in the right atrium.

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The detailed mapping of cardiac conduction ...

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