Nonpharmacological Treatment of Arrhythmias

A New Method of Segmental Pulmonary Vein Antrum Isolation: Comparison of Efficiencies on Different Types of Atrial Fibrillation
Teiichi Yamane
Jikei University School of Medicine, Tokyo, Japan

Epicardial Hypothermia: A Novel Tool for the Nonpharmacological Treatment of Serious Arrhythmias
Kaoru Okishige
Yokohama-City Bay Red Cross Hospital, Yokohama, Japan

A New Method of Segmental Pulmonary Vein Antrum Isolation: Comparison of Efficiencies on Different Types of Atrial Fibrillation

Teiichi Yamane

Jikei University School of Medicine
Tokyo, Japan

Figure 1. The new method used by Yamane and colleagues to target the antrum or left atrial posterior wall, which uses a larger-size Lasso catheter at the antrum for the EP-guided, segmental isolation.
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Figure 2. A typical example of the EP-Guided PV antrum isolation.
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Figure 3. A voltage-map of the LA performed after the PV antrum isolation showed a scarred area without electrical activity in the PV and around their antrum. In the posterior wall, the scar area extended toward the LA midline from the contralateral ostium of the PVs.
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Isolation of both the pulmonary veins and their surrounding tissues from the left atrium (LA) is necessary for the effective treatment of atrial fibrillation (AF). Dr. Teiichi Yamane, Jikei University School of Medicine, presented results of a study comparing a new method of segmental pulmonary vein antrum isolation (PVAI) on different types of AF. The method used by Yamane and colleagues is shown in Figure 1.

Study patients underwent EP-guided segmental isolation of the PVAI with a large-size Lasso catheter (Figure 2). This method involved individual isolation of four pulmonary veins at the antrum. Segmental RF energy application was guided by a 20-pole, Lasso catheter of 25 or 30 mm diameter. Two Lasso catheters were positioned at the ipsilateral PV antrums. Ablation was performed with a deflectable catheter with an 8 mm tip. Power was applied at 30 to 35 watts with a temperature control of 50 to 55 degrees. The endpoint of ablation was bidirectional LA-PV conduction block at the antrum of each pulmonary vein.

A voltage map of the LA post-PVAI was performed to confirm the influence of ablation on the LA activation (Figure 3). A scarred area without electrical activity was observed not only in the PV itself but also around their antrum. In the posterior wall, the scar area extended toward the LA midline from the contralateral ostium of the PVs.

A total of 145 patients with AF were included in the study. Of these, 92 had paroxysmal AF, 29 had persistent AF, and 24 had chronic AF. All patients were followed for at least nine months after the procedure. After the first ablation procedure, 62% of patients with paroxysmal AF, 43% of patients with persistent AF, and 30% of patients with chronic AF were free of AF without taking drugs (Figure 4). A second procedure was performed in 25% of patients with paroxysmal AF, 45% of patients with persistent AF, and 42% of patients with chronic AF. A mean of 1.4 procedures were performed on each patient (Figure 5). After the final procedure, 89% of patients with paroxysmal AF, 81% of patients with persistent AF, and 66% of patients with chronic AF were free of AF, without taking drugs (Figure 6).

Figure 4. The results after the initial ablation.
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Figure 5. The results in the patients who underwent another ablation because of recurrent atrial fibrillation.
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Figure 6. The results after the final ablation.
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Yamane concluded that EP-guided segmental PVAI using a large-size Lasso catheter is feasible, safe, and effective for treating AF. Recurrence of AF after the first procedure was more frequently observed in patients with persistent or chronic AF than in those with paroxysmal AF. However, repeat PVAI procedures targeting the reconducted pulmonary vein were shown to be equally effective in patients with all three types of AF. In the future, development of procedures for minimizing pulmonary vein reconduction and the systemic elimination of AF substrates in atrial tissues will be the next step in overcoming these arrhythmias.

Epicardial Hypothermia: A Novel Tool for the Nonpharmacological Treatment of Serious Arrhythmias

Kaoru Okishige

Yokohama-City Bay Red Cross Hospital
Yokohama, Japan

Experimental and clinical studies have shown that epicardial hypothermia is cardioprotective in the setting of acute myocardial ischemia. Mild hypothermia reduces metabolic demand, preserves mitochondrial function, and spares ATP stores during reperfusion. Dr. Kaoru Okishige, Yokohama-City Bay Red Cross Hospital, and colleagues investigated whether epicardial hypothermia also has antiarrhythmic effects in the setting of acute ischemia.

The objective of the study was to evaluate the feasibility, safety, and efficacy of inducing mild epicardial hypothermia to produce antiarrhythmic effects in the setting of acute ischemia. A total of 11 pigs weighing an average 28 kg were included in the study. The pigs were intubated, mechanically ventilated, and anesthetized with pentobarbital. Three introducer sheaths were inserted into the pericardial space via a subxyphoidal puncture to deliver fluid to the heart. Fluid was circulated inside the epicardial space at different temperatures using an extracorporeal circulation device. Two thermo-couple catheters were inserted into the epicardial space and coronary sinus for continuous temperature measurement. An electrode catheter was inserted into the ventricle to measure the effective refractory period (ERP) by programmed pacing and to induce ventricular fibrillation (VF). VF was repeatedly induced with stimuli from the electrode catheter. If VF did not occur, 98% ethanol was injected into the coronary artery to create a small acute myocardial infarction. After inducing infarction, ERP and incidence of VP were measured again. Ventricular ERP was significantly prolonged in the hypothermic state (30°C) compared to the control state (37°C) (P <0.01) (Figure 1).

When VF was induced after myocardial infarction, D-C cardioversion was done to resume sinus rhythm. If cardioversion failed to restore sinus rhythm, mild pericardioperfusion was performed with room temperature saline and D-C cardioversion was repeated (Figure 2). When D-C cardioversion was unsuccessful, epicardial hypothermia was applied. Induction of VF was attempted during epicardial hypothermia.

Figure 1. Hypothermia significantly prolonged the ventricular effective refractory period.
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Figure 2. In the setting of refractory ventricular fibrillation, D-C cardioversion was repeated.
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Refractory VF was successfully terminated by D-C cardioversion during epicardial hypothermia in 39 of 43 (91%) trials after unsuccessful cardioversion in the control state (Figure 3). Epicardial hypothermia produced a significant antiarrhythmic effect at 30° to 34°C.

Figure 3. D-C cardioversion successfully terminated ventricular fibrillation during hypothermia.
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Okishige concluded that mild pericardial hypothermia can be safely performed. Significant antiarrhythmic effects were observed in terms of suppressing ventricular fibrillation in the setting of acute myocardial ischemia. Mild epicardial hypothermia might be an effective treatment for patients with febrile Brugada syndrome associated with lethal ventricular arrhythmias and in refractory VF cases such as those with an “electrical storm” that is resistant to conventional therapy.

Congress Report

the 70th Scientific Session

Symposia

Symposium 1