An ECG records the heart's electrical signals, which are essential for assessing the heart's rhythm and function. It does not measure blood pressure, respiratory rate, or general muscle activity.

The P wave reflects the electrical activity associated with atrial depolarization. This is a fundamental aspect of ECG interpretation.

The QRS complex represents ventricular depolarization, initiating the contraction of the ventricles. It is larger and more complex than the P wave, making it a key component in ECG analysis.

Normal sinus rhythm means the heart's electrical impulses originate from the sinoatrial node in a regular pattern. This is indicative of proper conduction and normal heart function.

The T wave represents ventricular repolarization, which is the process of recovery following ventricular contraction. Recognizing this wave is important for evaluating cardiac recovery and rhythm.

A normal QRS complex duration is less than 0.12 seconds. A prolonged duration may indicate a conduction delay or block within the heart.

A prolonged QT interval is associated with delays in ventricular repolarization and can predispose the patient to life-threatening arrhythmias such as torsades de pointes. It requires careful evaluation and management.

Lead I provides a view of the lateral wall of the left ventricle. Along with other lateral leads (aVL, V5, and V6), it is essential for evaluating lateral myocardial infarctions and other abnormalities.

The normal PR interval ranges between 0.12 and 0.20 seconds. This interval reflects the conduction time from the atria to the ventricles through the AV node.

A notched R wave in lead V1 may indicate an incomplete right bundle branch block, suggesting a mild delay in right ventricular conduction. This finding warrants further clinical evaluation to rule out underlying pathology.

ST-segment elevation is a critical marker for acute myocardial infarction, indicating transmural ischemia. It is an emergency finding that requires immediate attention.

The PR interval reflects the conduction time from the atria through the AV node to the ventricles. Assessing this interval is essential for diagnosing atrioventricular conduction delays.

Incorrect electrode placement can lead to misrepresentation of wave amplitudes and axes. This can result in misdiagnosis, which is why proper electrode placement is critical for accurate ECG interpretation.

The initial Q wave is due to septal depolarization, where the electrical impulse passes through the interventricular septum. Recognizing normal Q waves is important to differentiate them from pathological Q waves seen in infarctions.

T wave inversions are often a sign of myocardial ischemia, indicating abnormal repolarization of the ventricles. This finding is significant in diagnosing ischemic heart conditions.

Hyperkalemia leads to characteristic peaked T waves due to its effect on myocardial membrane potentials. Recognizing these changes quickly is important for prompt management of the condition.

Left bundle branch block is characterized by a widened QRS complex with a typical pattern of broad, notched R waves in the lateral leads and deep S waves in V1. These findings help differentiate LBBB from other conduction abnormalities.

An ectopic atrial rhythm is identified by differences in the P wave morphology and axis compared to normal sinus rhythm. This deviation helps clinicians pinpoint the source of the rhythm outside of the sinoatrial node.

In severe hyperkalemia, as potassium levels rise further, the QRS complex begins to widen due to impaired myocardial conduction. This is a critical warning sign that can precede life-threatening arrhythmias.

The QT interval represents the total time for ventricular depolarization and repolarization, making it vital for assessing the timing of ventricular electrical activity. Abnormalities in this interval can increase the risk of arrhythmias.