What is monomorphic and polymorphic tachycardia?

Monomorphic tachycardia refers to a sustained heart rate acceleration in which all the QRS complexes are of the same morphology (shape). This means that the electrical impulses responsible for the heartbeats are originating from a single source and spreading in a consistent pattern throughout the heart. Monomorphic tachycardia can have several underlying causes, including abnormal automaticity, triggered activity, or reentry circuits in the heart's electrical conduction system.

In contrast, polymorphic tachycardia refers to a sustained heart rate acceleration in which the morphology of the QRS complexes varies over time. This means that the electrical impulses are originating from different sources or following inconsistent pathways within the heart during the arrhythmia. Polymorphic tachycardia is typically associated with more serious underlying conditions, such as ventricular fibrillation, which can lead to sudden cardiac arrest.

Summary:

Monomorphic Tachycardia: Same QRS morphology, consistent pattern, single source.

Polymorphic Tachycardia: Varying QRS morphology, inconsistent pattern, multiple sources.