What is the most likely cause of the telemetry findings in a patient with severe Chronic Obstructive Pulmonary Disease (COPD) showing a heart rate between tachycardia and normal sinus rhythm?

Multifocal Atrial Tachycardia (MAT)

The most likely cause of the telemetry findings is multifocal atrial tachycardia (MAT), which is characteristically seen in elderly patients with severe COPD and presents with irregular narrow-complex tachycardia between 100-120 bpm that spontaneously converts to normal sinus rhythm. 1, 2

Why MAT is the Correct Diagnosis

The clinical presentation strongly points to MAT based on several key features:

• Patient population: MAT is most commonly encountered in elderly patients with severe pulmonary disease, exactly matching this clinical scenario 1, 3
• Heart rate pattern: The captured rhythm shows a rate between 102-120 bpm lasting approximately 2 hours, which fits the diagnostic criteria for MAT (atrial rate >100 bpm) 3
• Asymptomatic presentation: The patient reported no symptoms overnight and is currently feeling well, which is consistent with MAT where the arrhythmia itself rarely causes hemodynamic compromise 4
• Spontaneous conversion: The rhythm returned to normal sinus rhythm without intervention, a common behavior of MAT 3, 4
• Severe COPD with oxygen dependence: The patient requires 4L oxygen for severe COPD, and MAT is triggered by hypoxia, acidemia, and increased catecholamines—all characteristic of acute-on-chronic COPD exacerbations 4

Why Other Diagnoses Are Less Likely

Sinus tachycardia with PACs would not explain a sustained 2-hour episode, as sinus tachycardia accelerates and terminates gradually rather than having the paroxysmal pattern described here 1

Atrial flutter with RVR typically shows a more regular atrial rate around 300 bpm with 2:1 or variable block, and the physical exam documented "regular rate and rhythm," which argues against the irregularity expected with variable block 2

Atrioventricular reentrant tachycardia (AVRT) would present with sudden onset paroxysmal supraventricular tachycardia, typically in younger patients without the severe pulmonary disease context, and would be more likely to cause symptoms given the re-entrant mechanism 1

Clinical Significance and Prognosis

• Mortality implications: While mortality in MAT patients ranges from 38-62%, this high mortality is due to underlying disease processes (particularly severe COPD and respiratory failure) rather than the arrhythmia itself 2, 4
• Prognostic indicators: The need for intubation and mechanical ventilation portends particularly poor prognosis, though this patient currently maintains baseline oxygen saturation 4
• Syncope evaluation: The orthostatic syncope that prompted admission requires cardiac evaluation per ACC/AHA guidelines, as continuous ECG monitoring is useful for hospitalized patients with syncope of suspected cardiac etiology 2

Management Approach

Primary treatment should address the underlying precipitating factors rather than focusing on antiarrhythmic therapy:

• Correct hypoxia: Ensure adequate oxygenation and optimize COPD management, as hypoxia is a primary trigger for MAT 2, 3
• Address electrolyte abnormalities: Check and correct hypokalemia and hypomagnesemia, which contribute to triggered electrical activity 2, 4
• Treat acidemia: Evaluate for respiratory or metabolic acidosis and correct as needed 2
• Review medications: Assess for theophylline toxicity or excessive beta-agonist use, both of which can precipitate MAT 3

Pharmacologic therapy should be considered if rate control is needed after addressing precipitating factors:

• Intravenous metoprolol or verapamil have been shown to control heart rate in the majority of MAT patients and are generally well-tolerated 3
• Avoid digoxin, as it is known to be ineffective in MAT therapy and carries potential for toxicity in this predisposed population 4

Critical Pitfalls to Avoid

• Misdiagnosis as atrial fibrillation: MAT is commonly mistaken for AF since both present with narrow ventricular complexes and irregular rates, but the distinction is crucial because digoxin is ineffective for MAT 4
• Overemphasis on antiarrhythmic therapy: Patients commonly convert to sinus rhythm spontaneously after correction of precipitating causes, making aggressive antiarrhythmic therapy unnecessary 4
• Ignoring the underlying COPD exacerbation: The arrhythmia is a marker of severe underlying disease rather than the primary problem requiring treatment 2, 4

Monitoring Recommendations

Given the patient's severe COPD and recent syncope, continued telemetry monitoring is appropriate per AHA guidelines for hospitalized patients with syncope of suspected cardiac etiology until the precipitating factors are identified and corrected 1, 2