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EKG Analysis: Detecting the Prolonged QT Interval Observed in Long QT Syndrome Carriers___In analyzing a suspected patient's EKG there are two key elements to look for. The first, and most important, is the duration of their corrected QT interval (QTc). The second dimension of analysis involves checking for any abnormalities in the shape of their T wave.  ___Measuring a patient's QTc is generally a simple procedure, however it is critical that it is performed carefully. To measure a patient's QTc, it is first necessary to determine the length of the QT interval. This is generally done on lead II or another limb lead with a well defined isoelectric point. The QT interval is the time in milliseconds (ms) between the start of the QRS complex and the end of the T wave where it intersects the isoelectric point. Having measured the QT interval, the RR interval is established by measuring the time interval between the QRS peaks of two adjacent heartbeats. Computerized measurements should not be used as they are often prone to errors and not accurate enough to meet the needs of diagnosing long QT syndrome. ___The QTc can be calculated using the equation shown in the figure to the right. The QTc intervals taken from at least three different T waves should be calculated. The QTc values obtained can then be used to establish the probability that a patient has long QT syndrome based on the data in table 1.
___Aside from measuring a patient's QTc, it is also important to pay attention to the shapes of the T waves present on a patient's EKG. Remember that the T wave represents ventricular repolarization during a heartbeat and that long QT syndrome is characterized by an abnormality of this part of the heart's recharging system. With that in mind, any abnormally shaped T waves should be noted. In particular, slowly generated, notched, low amplitude, delayed, and sinusoidal T waves should be looked for. ___If a patient suspected of having long QT syndrome is found to have either a QTc above 420ms or an abnormally shaped T wave, they must be immediately referred to an experienced cardiologist for further evaluation. It becomes the cardiologist's job to further evaluate the patient and start treatment. If an immediate appointment can not be setup for a patient to see a cardiologist, the physician should send the patient's EKGs, medical records, and interview notes to the cardiologist for prompt review. The cardiologist should review the data and recommend treatment options that the physician can start the patient on prior to further evaluation. For more information about current treatments for long QT syndrome, please see the treatment section of our website by clicking here.  ___ The contents of the Long-QT-Syndrome.com Site, such as text, graphics, images and all other material contained on Long-QT-Syndrome.com are for informational purposes only. The contents were not written by a practicing medical doctor/physician and may not be correct. The content within Long-QT-Syndrome.com is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of a physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on the Long-QT-Syndrome.com Site! |
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