Can sympathetic activation and catecholamine surges trigger supraventricular tachyarrhythmias and palpitations?

The relationship between the sympathetic nervous system and cardiac rhythm disturbances is well-documented, particularly in how catecholamine surges act as potent triggers for supraventricular tachyarrhythmias (SVT) and the perception of palpitations.

Clinical and physiological evidence

Sympathetic activation serves as a primary driver for various forms of SVT. In clinical settings, the sudden influx of catecholamines—such as epinephrine and norepinephrine—significantly alters the heart's electrical stability.

• Heart Rate and Hemodynamics: Adrenergic surges lead to rapid increases in heart rate and blood pressure. In postmenopausal populations, these surges are frequently associated with hot flashes and sleep fragmentation, which create a state of sympathetic hyperexcitability.
• Symptomatic Manifestations: Palpitations are the hallmark symptom of these events. While often caused by the arrhythmia itself, palpitations can also result from the surge in catecholamines alone, which increases myocardial contractility and stroke volume, making the heartbeat more perceptible even without a sustained tachycardia.

Mechanistic explanations

The transition from sympathetic activation to arrhythmia occurs through specific cellular pathways, primarily via beta-adrenergic stimulation.

• Calcium Signaling: Catecholamines activate L-type calcium channels (such as Cav1.3), which increases intracellular calcium loading. This triggers the synchronized release of calcium from the sarcoplasmic reticulum.
• Triggered Activity: This calcium overload induces delayed afterdepolarizations (DADs) and early afterdepolarizations (EADs). These electrical abnormalities can bypass the heart's normal pacing, leading to rapid, repetitive action potentials in atrial tissue and Purkinje fibers.
• Automaticity: Adrenergic stimulation enhances the firing rate of the sinoatrial node (SAN) and can unmask latent pacemakers in the atria, directly initiating tachyarrhythmias.

Bottom line

Sympathetic activation and catecholamine surges are scientifically proven triggers for supraventricular tachyarrhythmias. They function by driving calcium-mediated triggered activity and enhancing cardiac automaticity, leading to the clinical experience of palpitations and rapid heart rhythms.