A 66-year-old man with a history of longstanding persistent atrial fibrillation (AF), s/p 3 left atrial (LA) catheter ablation procedures, was referred for persistent atrial tachycardia (AT) and worsening functional status. He also has a history of ischemic cardiomyopathy (left ventricular (LV) ejection fraction, 15%; LA diameter, 5.8 cm) and is s/p implantation of a dual chamber implantable cardioverter defibrillator (ICD). The original right ventricular high voltage lead was recalled, and another right ventricular lead was placed at the time of his generator change (he declined lead extraction). He has received multiple inappropriate and appropriate ICD discharges in the past. He was initiated on dofetilide (250 mcg twice daily; 500 mcg dose caused QT prolongation) therapy for recurrent AT following his last catheter ablation procedure three years ago. Along with atrial antitachycardia pacing, his arrhythmia burden was undetectable with improvement in his symptoms. However, over the last several months, he had noted persistently elevated heart rate at rest at 120 bpm. A 12-lead electrocardiogram showed an atrial tachycardia with 1:1 atrioventricular (AV) conduction (Figure 1). Atrial ATP could no longer be performed given that the rate of the AT approximated the programmed upper rate of 120 bpm. His symptoms include fatigue, effort intolerance, which have made it difficult for him to exercise.
Figure 1
Physical Examination: BP 90/60 mm Hg. Heart rate122 bpm. There was no jugular venous distension. Lungs were clear. Heart tones were tachycardic, with no murmurs or S3. Abdominal exam shows no ascites. There is trace bilateral lower extremity edema.
The correct answer is: C. Refer for catheter ablation of atrial tachycardia
The patient presents with worsening functional status in the setting of persistent AT and severe LV dysfunction. The simplest option to attempt to alleviate symptoms is to add another AV nodal drug, such as diltiazem. However, given their myocardial depressant effect, nondihydropyridines are best avoided in systolic heart failure. Increasing the dose of dofetilide is not good option either given that a prior attempt resulted in QT prolongation. Although the BNP level is elevated, in the absence of obvious congestion and relative hypotension, optimization of his heart failure regimen is unlikely to have the desired effect. AV junction ablation will definitely treat the resting tachycardia; however, it will also result in loss of AV synchrony, pacing dependence, and dyssynchrony. Whereas atrial ATP had been effective previously, the fact that the current tachycardia rate is close to the upper rate means that the arrhythmia cannot be diagnosed (and hence treated) as a tachycardia. Since the tachycardia recurred after manual overdrive pacing in the office setting, transthoracic cardioversion is unlikely to result in long-term freedom from the AT. The classic cut-and-sew maze surgery is effective in eliminating AF but probably has little to offer a patient with AT.
After discussing the pros and cons of these approaches, the patient elected to proceed with an ablation procedure. After left atrial access was obtained, a diagnosis of mitral isthmus dependent flutter was made. Radiofrequency energy was delivered at the atrial tissue between the lateral mitral annulus and the left pulmonary veins restored and restored sinus rhythm. The left pulmonary veins were re-isolated, and the patient was rendered noninducible. Two months after the ablation procedure, the patient notes a marked improvement in his symptoms and device interrogation fails to reveal recurrence. The plan is to discontinue dofetilide in a few weeks.
This case highlights several points. First, it confirms the importance of sinus rhythm in patients with AF and congestive heart failure. Large randomized trials have shown that a rhythm strategy using antiarrhythmic drugs (AAD) in such patients is not associated with improved survival.1 It then could be argued that a rate-control strategy should be recommended in this case. Although such a strategy is certainly reasonable and supported by the literature, it is unlikely to lead to improvement in symptoms in patients such as ours. Thus, results of even well done studies need not be applied broadly and instead, clinical management is best guided by the individualizing care.
Regarding the neutral outcome of rhythm-versus-rate trials, it should be noted that any benefit of sinus rhythm may have been neutralized by the adverse effects of AADs, such as proarrhythmia and end-organ toxicity.2 In trials using catheter ablation instead of AADs, patients note an improvement in their functional status concomitant with improvement in LV ejection fraction.3 These studies, however, are limited by the small sample size, and the complexity and multiplicity of ablation procedures required.
Indeed, patients with persistent AF and advanced structural heart disease may require multiple ablation procedures before sinus rhythm is restored. This reflects our incomplete understanding of the arrhythmia and suboptimal ablation tools. Despite these limitations, sinus rhythm may be restored in about 80% of patients with persistent AF without the need for antiarrhythmic mediations and with a low risk of complications.4
AV junction ablation and biventricular pacing is another option in this patient. However, it again would not restore AV synchrony and may not lead to symptom alleviation. Also, it involves placing another (4th) lead in the central venous system, with its attendant complications, and also renders the patient pacemaker dependent. Lastly, catheter ablation of AF was shown to outperform AV junction ablation/biventricular pacing in patients with CHF.5
In conclusion, catheter ablation of AF and related arrhythmias is a viable option for patients with drug- and device-refractory arrhythmias even in the setting of structural heart disease.
References
Roy D, Talajic M, Nattel S, et al. Rhythm control versus rate control for atrial fibrillation and heart failure. N Engl J Med 2008;358:2667-2677.
Corley SD, Epstein AE, DiMarco JP, et al. Relationships between sinus rhythm, treatment, and survival in the atrial fibrillation follow-up investigation of rhythm management (affirm) study. Circulation 2004;109:1509-1513.
Hunter RJ, Berriman TJ, Diab I, et al. A randomised controlled trial of catheter ablation versus medical treatment of atrial fibrillation in heart failure (the camtaf trial). Circ Arrhythm Electrophysiol 2014; 1;7:31-8.
Yokokawa M, Latchamsetty R, Ghanbari H, et al. Characteristics of atrial tachycardia due to small vs large reentrant circuits after ablation of persistent atrial fibrillation. Heart Rhythm 2013;10:469-476.
Khan MN, Jais P, Cummings J, et al. Pulmonary-vein isolation for atrial fibrillation in patients with heart failure. N Engl J Med 2008;359:1778-1785.
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