Final answer:
Based on an ECG showing an abnormal electrical pattern before QRS complexes with increased frequency, the most likely diagnosis is atrial fibrillation, which presents with an irregular rhythm due to quivering atria, absence of distinct P waves, and irregular QRS complexes.
Step-by-step explanation:
To determine the most likely diagnosis based on an ECG, it is essential to look for key features within the tracing. Normal Sinus Rhythm (NSR) is characterized by a consistent heart rate with a regular rhythm and a P wave preceding each QRS complex, indicating that the atria are contracting smoothly and the impulses are traveling normally from the sinoatrial (SA) node to the atrioventricular node.
Atrial fibrillation is distinguished by an irregular heart rate and an absence of distinct P waves before the QRS complexes; the atria quiver instead of contracting effectively. Atrial flutter typically shows a 'sawtooth' pattern of atrial activity but with a more regular ventricular rate than atrial fibrillation. Supraventricular Tachycardia (SVT) would present with a very fast heartbeat but may still show organized atrial activity.
Given a description of an abnormal electrical pattern prior to the QRS complexes with an increased frequency between the QRS complexes, this suggests an irregular and possibly rapid rhythm which is common in atrial fibrillation. If there is a chaotic, irregular baseline without discrete P waves and with irregular QRS complexes, atrial fibrillation is the most likely diagnosis.