Summary A fast heart rate or an irregular ventricular rhythm can produce various degrees of functional impairment and structural remodeling of the ventricle referred to as tachycardia-related cardiomyopathy or tachycardiomyopathy. This form of myocardial dysfunction can be caused by supraventricular or ventricular tachyarrhythmias that are incessant and associated with ventricular rates higher than 120 bpm. It can be reversed with pharmacological or nonpharmacological rate control or arrhythmia reversion. The prevalence of ventricular and supraventricular tachyarrhythmias is high among patients with heart failure. Consequently, in clinical settings, it may be difficult to determine whether a patient with severe ventricular dysfunction and supraventricular tachyarrhythmia associated with a rapid ventricular response is suffering from tachycardiomyopathy or from heart failure complicated by the subsequent development of a supraventricular tachyarrhythmia (e.g. atrial fibrillation). This typical “chicken-or-the-egg” dilemma can be resolved by treating the arrhythmia (pharmacological or nonpharmacological rate and/or rhythm control) and closely monitoring the evolution of the left ventricular dysfunction. Proper management of tachycardiomyopathy requires appropriate decision making, use of both pharmacological and nonpharmacological treatment approaches, and close follow-up. The purpose of this review article is to examine currently available data (experimental and clinical) on this complex clinical entity and on rate-control therapy.