What is defined as a heart rate greater than 120 beats per minute with wide QRS complexes?

A heart rate greater than 120 beats per minute accompanied by wide QRS complexes is indicative of ventricular tachycardia. This condition occurs when the lower chambers of the heart (the ventricles) start beating rapidly and independently from the upper chambers (the atria), resulting in a decreased ability of the heart to pump effectively and maintain adequate blood flow to the body.

Wide QRS complexes signify that the electrical impulses are originating from the ventricles rather than the higher areas of the heart. This is a critical distinction as it points towards a more serious arrhythmia that can lead to decreased cardiac output and may cause symptoms such as dizziness, chest pain, or syncope.

In contrast, the other conditions listed do not typically present in this manner; for instance, atrial fibrillation usually displays a rapid heart rate but with a variable and narrow QRS complex due to the conduction through the atrioventricular node. Supraventricular tachycardia typically involves a narrow QRS complex because it originates above the ventricles, while ventricular fibrillation is a chaotic rhythm that results in ineffective heart contractions, often leading to cardiac arrest. Therefore, recognizing the characteristics of ventricular tachycardia is crucial for appropriate diagnosis and intervention.