This review explains the QT interval on the ECG/EKG.
Before diving right into these parts of the ECG waveform, we must go back and review the basic anatomy and physiology of the heart’s electrical conduction system.
Electrical Conduction System of the Heart:
It all starts in the:
SA Node (sinoatrial node): this node is located in the upper part the right atrium and is known as the pacemaker of the heart, causing the heart to beat at 60-100 bpm. When this node fires, it sends electrical impulses to the atria causing atrial depolarization of the cells in the right and left atrium (remember depolarization causes the atria to contract). Then the electrical signals go to the:
AV node (atrioventricular node): this node is found in the lower part of the right atrium just above the tricuspid valve and is known as the “gatekeeper”.
The AV node is known for causing a delay in electrical signaling so the atria can fully empty their blood into the ventricles. If there wasn’t a delay, the atria would not fully empty its blood into the ventricles and this would cause problems.
Then it’s time for the ventricles to be depolarized (hence contract). So the electrical signal goes down to the Bundle of His, then the bundle branches (right and left) and lastly the Purkinje fibers, which causes the ventricles to depolarize. Shortly after this process, repolarization occurs and this process repeats itself over and over again.
ECG/EKG Study Guide and Workbook for Nursing Students
“ECG/EKG Interpretation Study Guide and Workbook by Nurse Sarah”. This book contain 100 pages of content featuring 26 ECG rhythm break downs, 51 ECG rhythm analysis practice problems, 100 comprehensive ECG practice questions, worksheets, chart summaries, and more.
You can get an eBook version here: “Nurse Sarah ECG Book” or a physical copy here: “ECG/EKG Interpretation Study Guide by Nurse Sarah“.
What’s the QT Interval?
QT interval: This is a part that is measured on the ECG. It starts at the beginning of the QRS complex and ends at the end of the t-wave. It demonstrates the time it takes for electrical signals to cause the ventricles to contract and then rest.
Measurement should be 0.35-0.44 seconds. Men have shorter intervals than women and the measurement varies on how fast or slow the heart rate is. For example, a fast heart rate has a shorten QT interval. A prolonged QT interval could increase risk of ventricular dysrhythmias like Torsade’s de Pointes.
A prolonged QT interval is commonly caused by medications like certain types of antibiotics (macrolides) or cardiac medications like Amiodarone or Procainamide etc.
You may be interested in more parts of the ECG Waveform.