Beyond Arrhythmias ST & QT Segment Monitoring

1. Kate Martin CNE April 2009 Beyond ArrhythmiasST & QT Segment Monitoring

2. Monitoring Practice International Guidelines • Chest pain that prompts a visit to the emergency department, • Post cardiac surgery • Patients at risk for postoperative cardiac complications after non-cardiac surgery.

3. Angina • Although chest pain is a real-time indicator of ischemia, up to 80% to 90% of ischemia is "silent" or "concealed”

4. Diagnostic Testing • 12-lead (ECG), measurement of serum markers of injury, and cardiac catheterization, provide only a static "snapshot" of the dynamic process of ongoing ischemia.

5. Diagnostic Relevance • Although the accuracy of continuous ST monitoring has improved with technology the diagnostic relevance of ST changes remains dependant on several factors • ST segment changes may be an indication for a 12 lead EKG

6. Establishing ST Monitoring • On Admission • Ensure skin is properly prepped • Ensure leads are in proper position • Record a baseline ST strip

7. Choosing Your Leads • Just like with a 12 lead EKG, lead placement should be accurate. • The Phillips monitor can monitor ST segments on up to six leads on a telemetry unit and all 12 leads on a hardwire monitor • Choose the leads which monitor the area of the heart most at risk

8. 12 Lead Limb Lead Placement

9. 12 Lead Precordial Lead Placement

10. 12 Lead View

11. 12 Lead EKG

12. Standard Monitor Lead Placement

13. EASI Lead Placement

14. EASI View

15. Continuous ST Monitoring

16. ST Segment Map

17. The Coronary Arteries

18. Anterior Leads Leads I & V1-4 • LAD • LM

19. Lateral Leads • Leads avR, avL, & V5-6 • Circumflex

20. Inferior Leads Leads II, III, & avF • RCA • Circumflex

21. Posterior Leads Leads I & V1-4 • Mirror Image • Posterior Artery

22. The J Point The ST segment begins at the point where the QRS ends (J-point). Diagnostic criteria of ST segment changes have been defined to be measured at 60 ms after the J-point (1.5 small squares/.06sec)

23. Metabolic Abnormalities Producing ST Changes Hypokalemia • ST depression Hyperkalemia • Peaked T waves Hypermagnesemia • ST depression Hyperthyroidism • ST elevation with T wave inversion in inferior leads

24. Medications Producing ST Changes • Digitalis • ST depression • Shortened QT interval • Amiodarone • Lengthened QT interval

25. Other Factors Producing ST Changes • Pericarditis • ST elevation • Hypothermia • ST depression • Pulmonary Infarction • Depressed ST segments and inverted T waves in V 1 – 3

26. Effect of Arrhythmias • Bundle Branch Blocks • ST segment shifts • Paced Rhythm • ST segments non diagnostic

27. Response to change in ST Segment • Is patient experiencing angina symptoms? • Follow ACS protocol • Is patient hemodynamically unstable • Stabilize

28. United Hospital’s Nassett Heart Center, St Paul, Minnesota

29. The QT Interval

30. Pharmacology and the QT Interval A number of drugs are known to prolong the QT interval and include all of the antiarrhythmics

31. Importance of QT monitoring • QT prolongation can indicate a risk of severe arrhythmias, torsades de pointes, and sudden cardiac death.

32. What is a QTc? • The QT has an inverse relationship to HR. • QT = QTc at a HR of 60 bpm only • Heart rate corrected QT interval is abbreviated as QTc • Normal QTc is < 460 ms

33. QT Monitoring

34. Setting Alarms

35. QT Measurement Limitations “Cannot Analyze QT” INOP message: Flat T, Atrial Fib/Flutter Prominent U Waves Highly variable QRS-T waveforms over 10 minutes duration Clinical Verification: Widened QRS (Paced rhythm, bigeminal rhythm) High heart rates > 150 due to P waves being too close to T waves.

36. Sources Leeper, B. Continuous ST-segment monitoring. AACN Clinical Issues 2003. 14(2): 145-154. American Association Of Critical Care Nurses St Segment Monitoring Practice Alert Critical Care Nurse. 2005; Clinical Usefulness of the EASI 12-Lead Continuous Electrocardiographic Monitoring System; Mary Jahrsdoerfer, RN, MHA.,Karen Giuliano, RN, PhD., Dean Stephens, RN, MS