What happens to the ECG when your heart speeds up?
When your heart speeds up, several changes occur on an electrocardiogram (ECG). Here's what to expect:
1. Increased Heart Rate: The most apparent change is an increase in the heart rate, which is reflected as a shorter distance between consecutive R waves on the ECG tracing.
2. Shortened PR Interval: The PR interval represents the time it takes for the electrical impulse to travel from the atria (upper chambers) to the ventricles (lower chambers). As the heart rate increases, the PR interval may shorten slightly due to more efficient conduction of electrical signals.
3. Narrowed QRS Complex: The QRS complex represents the electrical activation of the ventricles. With a faster heart rate, the ventricular depolarization occurs more rapidly, resulting in a narrower QRS complex.
4. Taller P Waves: The P waves, which represent atrial activation, may become taller and more distinct due to increased atrial muscle activity associated with the faster heart rate.
5. Changes in ST Segment: The ST segment, which lies between the QRS complex and the T wave, may become elevated or depressed during a rapid heart rate. This is often transient and may not necessarily indicate an underlying cardiac condition.
6. Altered T Waves: The T waves, which represent ventricular repolarization, may change in shape or polarity with an increase in heart rate. These changes are often subtle and difficult to interpret in isolation.
7. Arrhythmias: A fast heart rate can lead to the development of arrhythmias, such as atrial fibrillation or atrial flutter. These conditions are characterized by disorganized electrical activity, resulting in irregular and rapid heart rhythms on the ECG.
It's important to note that the interpretation of ECG changes during a fast heart rate should be done in the context of the individual's overall health, symptoms, and other clinical findings. A healthcare professional will evaluate the ECG in combination with other diagnostic tests and medical history to determine the cause and significance of the observed changes.