A patient in their 60s was referred for atrial flutter ablation following admission to their local hospital for heart failure exacerbation. The patient had developed worsening shortness of breath and new-onset New York Heart Association functional class IV symptoms and was known to have ischemic cardiomyopathy, with an ejection fraction of 25%, and had received a single-chamber primary prevention implantable cardioverter-defibrillator (ICD) in the past. Amiodarone treatment was started in the past in an attempt to achieve rhythm control of the atrial flutter. On assessment in the emergency department, the patient was found to have a heart rate of 106 beats/min and a blood pressure of 96/58 mm Hg. Clinical examination revealed substantial volume overload, with an elevated jugular venous pressure, bilateral lung crackles on auscultation, and a prominent S3 on cardiac auscultation. Pertinent laboratory results included markedly elevated N-terminal pro-brain natriuretic peptide and creatinine levels. An echocardiogram during the current admission demonstrated a drop in ejection fraction to 10%. A 12-lead electrocardiogram (ECG) was obtained (Figure, A).
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Atrial tachyarrhythmias, including atrial fibrillation (AF) and atrial flutter, are common among patients with structural heart disease, and by extension patients with device implants.3- 5 The incidence of dual tachycardia among this population, defined as ventricular tachycardia (VT) or ventricular fibrillation that initiated in the setting of an ongoing atrial tachycardia or AF episode, is approximately 8.6%.3 Recognizing atrial arrhythmias, especially AF, is of paramount importance, given that the detection of AF in patients with ICDs is an independent predictor of mortality and can be a trigger for ventricular arrhythmias.3- 5 In addition, AF itself can result higher shock rates among patients with ICD implants.5- 7 Recognition is simpler in dual-chamber devices given the luxury of 2 channels being available. However, in cases where only a single-chamber channel is available, this can be challenging. Therefore, the surface ECG becomes the primary bedside tool the clinician can use for reaching an accurate diagnosis. In this case, the patient was initially determined correctly to have atrial flutter. However, recognizing the underlying AIVR via the surface ECG requires intricate knowledge of QRS morphology and AV dissociation, 2 clues that allow the clinician to reach an accurate diagnosis. The variability of the PR interval is another important aspect that proves the presence of AV dissociation.
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CME Disclosure Statement: Unless noted, all individuals in control of content reported no relevant financial relationships. If applicable, all relevant financial relationships have been mitigated.
Corresponding Author: Ahmed T. Mokhtar, MBBS, University Hospital, 339 Windermere Rd, Room 3C-611B, London, ON N6A 5A5, Canada (firstname.lastname@example.org).
Published Online: August 22, 2022. doi:10.1001/jamainternmed.2022.3430
Conflict of Interest Disclosures: None reported.
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