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QT INTERVAL and TORSADES de POINTES:

QT INTERVAL and TORSADES de POINTES: THE FRENCH CONNECTION. OBJECTIVES:At the end of this presentation the viewer will be able to: Accurately measure QT interval Find QTc using QT to QTc Conversion ChartDiscuss the clinical significance of abnormally prolonged QTcDescribe appropriate nursing i

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QT INTERVAL and TORSADES de POINTES:

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    1. QT INTERVAL and TORSADES de POINTES: THE FRENCH CONNECTION

    2. QT INTERVAL and TORSADES de POINTES: THE FRENCH CONNECTION OBJECTIVES: At the end of this presentation the viewer will be able to: Accurately measure QT interval Find QTc using QT to QTc Conversion Chart Discuss the clinical significance of abnormally prolonged QTc Describe appropriate nursing interventions when abnormally prolonged QTc is identified.

    3. QT INTERVAL and TORSADES de POINTES: THE FRENCH CONNECTION Today’s patients receive the benefit from many advances in medical technology and research. Among those benefits are multiple new drug therapies.

    4. QT INTERVAL and TORSADES de POINTES: THE FRENCH CONNECTION However, along with these new drug therapies come inherent new risks.

    5. QT INTERVAL and TORSADES de POINTES: THE FRENCH CONNECTION With increasing frequency, patients are experiencing a potentially fatal form of polymorphic ventricular tachycardia called Torsades de Pointes

    6. QT INTERVAL and TORSADES de POINTES: THE FRENCH CONNECTION

    7. QT INTERVAL and TORSADES de POINTES: THE FRENCH CONNECTION “Polymorphic” means it assumes multiple shapes. The tachycardia varies in size and shape and gives the appearance of twisting around the isoelectric baseline.

    8. QT INTERVAL and TORSADES de POINTES: THE FRENCH CONNECTION The patient may have no pulse or blood pressure and may need to be defibrillated immediately. At times, the rhythm spontaneously converts before loss of pulse or blood pressure occurs.

    9. QT INTERVAL and TORSADES de POINTES: THE FRENCH CONNECTION These patients may simply present with complaint of fainting spells at home.

    10. QT INTERVAL and TORSADES de POINTES: THE FRENCH CONNECTION This life-threatening arrhythmia may be caused by factors that prolong the QT interval. Among these factors are heredity electrolyte disturbances myocardial ischemia bradycardia drug therapy

    11. QT INTERVAL and TORSADES de POINTES: THE FRENCH CONNECTION Drug Induced Antidepressants Phenothiazines Antiarrhythmics*** Pronestyl Amiodarone Corvert Electrolye Imbalance Low Magnesium*** Low Potassium Low Calcium Insecticides Eating disorders Bulimia Anorexia Hereditary 1/3 asymptomatic Suspect if hx. Fainting Triggers emotional excitement exercise being startled anger test-taking stressful situations

    12. QT INTERVAL and TORSADES de POINTES: THE FRENCH CONNECTION Since many new drugs of various classifications may cause prolongation of the QT interval, it is imperative that the health care team carefully monitor and trend the QT intervals of patients in our care.

    14. QT INTERVAL and TORSADES de POINTES: THE FRENCH CONNECTION “HOW do I monitor QT interval?”, you may ask.

    15. QT INTERVAL and TORSADES de POINTES: THE FRENCH CONNECTION First measure the QT interval Secondly, correct it for the heart rate, if heart rate is above 60. Determine if it is greater than 0.5 seconds (500 msec) in duration. Lastly, compare QTc to previous QTc’s to determine if it is lengthening (trends!)

    17. QT INTERVAL and TORSADES de POINTES: THE FRENCH CONNECTION The acceptable length of QT interval varies according to many factors. One of those factors is the heart rate. As the heart rate increases above 60 bpm, the QT interval must be “corrected” for that heart rate to know whether it is above normal limits.

    18. QT INTERVAL and TORSADES de POINTES: THE FRENCH CONNECTION If the QTc is greater than 0.50 seconds (500 msec), the patient is at risk for developing Torsades de Pointes. Trending QTc is, therefore, important and should be discussed with the appropriate physician when QTc is approaching or becomes greater than 0.5 seconds (500 msec).

    19. QT INTERVAL and TORSADES de POINTES: THE FRENCH CONNECTION Locate a laminated QT to QTc conversion chart in your nurses station. Find the patient’s heart rate along the left margin of the chart. ( the vertical axis) Find the QT interval that you measured at the top of the chart. (horizontal axis) Note that msec is converted to seconds by adding a decimal. Where the two intersect, you find the QTc.

    20. QT INTERVAL and TORSADES de POINTES: THE FRENCH CONNECTION

    21. QT INTERVAL and TORSADES de POINTES: THE FRENCH CONNECTION If heart rate is less than 60, no correction is needed. The QTc is the same as the measured QT interval.

    24. QT INTERVAL and TORSADES de POINTES: THE FRENCH CONNECTION SUMMARY Many drugs and other conditions may cause the QT interval to prolong. Torsades de Pointes may result, causing death. Measuring and trending QTc will help prevent this complication from occurring.

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