Final answer:
Premature ventricular contractions, detected through an ECG, are early, abnormal heartbeats originating from the ventricles. Understanding the ECG's P waves, QRS complexes, and T waves is key to interpreting these and other arrhythmias. PVCs, atrial fibrillation, and ventricular tachycardia have distinct manifestations on an ECG.
Step-by-step explanation:
An electrocardiogram (ECG or EKG) traces the electrical activity of the heart and is crucial for diagnosing various cardiac conditions. Premature ventricular contractions (PVCs) are a type of arrhythmia revealed on an ECG as abnormal, early QRS complexes. They are caused by ectopic impulses originating from the ventricles rather than the normal sinoatrial (SA) node.
Understanding the ECG components is important for interpreting these patterns. The small P wave indicates atrial depolarization, the large QRS complex signifies ventricular depolarization, and the T wave represents ventricular repolarization. The tracing may also show PR, QT, QRS intervals and segments relevant to the timing of electrical events in the heart.
Conditions such as atrial fibrillation display irregularities before the QRS complex and an increased frequency between QRS complexes, while ventricular arrhythmias like ventricular tachycardia and ventricular fibrillation show abnormal QRS shapes or the absence of recognizable ECG components, respectively. AV blocks vary in degree and affect the relationship between atrial and ventricular activities, with some blocks causing the atrial P wave to lack a subsequent QRS complex.