Respiration driven excessive sinus tachycardia treated with clonidine

Area of Science:

• Cardiology
• Autonomic Nervous System Disorders

Background:

• A 26-year-old man with a history of Mobitz type II block and permanent pacemaker presented with debilitating daily palpitations, shortness of breath, presyncope, and syncope.
• Symptoms began 4 years after a severe viral respiratory illness and were reproducible on maneuvers like deep inspiration and coughing.

Observation:

• Standard investigations including transthoracic echocardiography, electrophysiological study, and urine metanephrines were unremarkable.
• Electrocardiogram (ECG) showed rapid heart rate increases without morphological changes during symptomatic episodes.

Findings:

• The patient's symptoms were refractory to multiple treatments, including fludrocortisone, flecainide, beta-blockers, and ivabradine.
• Combination therapy with clonidine and ivabradine led to rapid and complete symptom resolution.

Implications:

• Excessive respiratory sinus arrhythmia is a potential cause of refractory palpitations and syncope.
• Centrally acting sympatholytic agents like clonidine may be effective in managing such autonomic dysfunction when peripheral treatments fail.