Background

An 82-year-old man is brought to the emergency department (ED) by a rescue ambulance. The patient experienced a sudden loss of consciousness at his home while he was walking to the bathroom. The patient’s wife heard a thump from another room in their home and came to find her husband lying on the floor. She reported that his upper extremities twitched a couple of times and his eyes rolled back, but within a minute, he was awake and alert and asking what had happened. He remained stable during transport; the main finding that the ambulance personnel reported was that his pulse seemed irregular and sometimes slow.


{mosimage}On arrival in the ED, the patient is alert and awake, with an apparent baseline normal mental status; he does not seem groggy or confused. Given the lack of premonitory symptoms and the abnormal pulse rhythm, the emergency care physician is concerned that the patient has had cardiac syncope. The cardiac monitor shows an intermittent irregular rhythm and a heart rate of 62 bpm. The patient’s blood pressure is 150/82 mm Hg, and his oxygen saturation is 99% while he is breathing room air. A 12-lead electrocardiogram (ECG) is ordered.

What is the diagnosis?

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Hint

Note the underlying atrial rhythm and the ratio of atrial-to-ventricular depolarizations.
Authors:
Thomas J. Hemingway, MD, Attending Physician, Department of Emergency Medicine, Wilcox Memorial Hospital, Lihue, HI.

Rick G. Kulkarni, MD, FACEP, Assistant Professor, Yale School of Medicine, Section of Emergency Medicine, Department of Surgery, Attending Physician, Medical Director, Department of Emergency Services, Yale-New Haven Hospital, CT

Marshall T. Morgan, MD, Chairman, Department of Emergency Medicine, UCLA Medical Center, Professor of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA

eMedicine Editors:
John Vozenilek, MD, FACEP, Clinical Assistant Professor of Emergency Medicine, Assistant Professor of Medical Education, Feinberg School of Medicine, Northwestern University

Rick G. Kulkarni, MD, FACEP, Assistant Professor, Yale School of Medicine, Section of Emergency Medicine, Department of Surgery, Attending Physician, Medical Director, Department of Emergency Services, Yale-New Haven Hospital, CT

Edward J. Miller, MD, Section of Cardiovascular Medicine, Yale University School of Medicine, New Haven, CT
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Answer

Atrial flutter with variable block: Sawtooth f waves can be seen in the inferior leads (II, III, aVF) and in V1; these leads are usually where flutter waves are most easily recognized. Also of note is the variability in the timing of the QRS complexes that follow. In atrial flutter, the atrial rate is generally 250-350 bpm; in this case, the atrial rate is approximately 300 bpm. Patients with atrial flutter typically present with a regular ventricular response of about 150 bpm as a result of 2:1 atrioventricular nodal (AVN) conduction. Slower rates may occur with a diseased conduction system, as in this case, or with the use of rate-slowing agents, such as beta-blockers, calcium channel blockers, or digoxin.

Patients with digoxin toxicity classically present with atrial tachycardia or atrial flutter with variable block. The differential diagnosis for a patient with an irregular rhythm on ECG (aside from respiratory variation and premature atrial or ventricular beats) is atrial fibrillation, atrial flutter, and multifocal atrial tachycardia; atrial fibrillation is the most common differential diagnosis.

Atrial flutter is a rhythm that has a high incidence in the elderly (about 50-90 cases per 1000 people aged 65-90). Patients may present with variable block (as in this case), especially those with a diseased conduction system. Although it is relatively rare for patients in atrial flutter to experience syncope from slow AVN conduction in the absence of drug effects or toxicity, syncope can occur when the atrial flutter rate is “slow” (<200 bpm), allowing 1:1 AVN conduction and fast ventricular response rates. In patients with underlying sinus node dysfunction, syncope can also occur when atrial flutter terminates and the sinus node fails to recover rapidly. This is also known as the so-called “sick sinus” or “tachy-brady” syndrome.

In elderly patients, sinus node and AVN dysfunction commonly occur simultaneously. Evaluation and treatment of patients with newly diagnosed atrial flutter should focus on determining whether symptoms may be occurring from either fast or slow ventricular responses, as well as managing the rate of conduction through the AV node. In typical patients with fast ventricular response rates, AVN blocking agents (beta-blockers, calcium channel blockers, and digoxin) are effective. In patients with slow ventricular response rates and symptoms, a search for reversible causes for impaired AVN conduction should be undertaken, and the patient should be monitored on telemetry. If there is an absence of reversible factors, or if evidence of sinus node dysfunction occurs, the patient should be considered for pacemaker implantation. Cardioversion should be utilized acutely if hemodynamically unstable rapid AVN conduction is present.

In this case, evidence of impaired AVN conduction (ie, slow ventricular response) and significant distal conduction system disease (right bundle branch block and left anterior fascicular block) suggests that pacemaker implantation may be warranted. The need for cardiac medications to treat tachyarrhythmias (which may be intermittent) is also an indication for pacemaker implantation, as these therapeutic agents alone may worsen an existing heart block. Therefore, pacing to treat bradycardia and drug therapy to treat tachycardia may be required for those with tachycardia-bradycardia syndrome.

References:

Adán V, Crown LA. Diagnosis and treatment of sick sinus syndrome. Am Fam Physician 2003 Apr 15;67(8):1725-32. Review. [MEDLINE: 12725451]
Goodacre S, Irons R. ABC of clinical electrocardiography: atrial arrhythmias. BMJ 2002 Mar 9;324(7337):594-7. Review. No abstract available. Erratum in: BMJ 2002 Apr 27;324(7344):1002. [MEDLINE: 11884328]
Tintinalli JE, Kelen DG, Stapczynski JS. Emergency Medicine: A Comprehensive Study Guide. 6th ed. New York, NY: McGraw-Hill; 2004.
Zipes DP, Libby P, Bonow R, Braunwald E. Braunwald’s Heart Disease: A Textbook of Cardiovascular Medicine. 7th ed. Philadelphia, PA: W.B. Saunders; 2004.