Kate Martin CNE Beyond Arrhythmias ST QT Segment
Kate Martin CNE Beyond Arrhythmias ST & QT Segment Monitoring Kate Martin CNE April 2009
Monitoring Practice International Guidelines Kate Martin CNE Chest pain that prompts a visit to the emergency department, Post cardiac surgery Patients at risk for postoperative cardiac complications after non-cardiac surgery.
Kate Martin CNE Angina Although chest pain is a real-time indicator of ischemia, up to 80% to 90% of ischemia is "silent" or "concealed”
Kate Martin CNE 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.
Kate Martin CNE 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
Kate Martin CNE Establishing ST Monitoring On Admission Ensure skin is properly prepped Ensure leads are in proper position Record a baseline ST strip
Kate Martin CNE 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
Kate Martin CNE 12 Lead Limb Lead Placement
Kate Martin CNE 12 Lead Precordial Lead Placement
Kate Martin CNE 12 Lead View
Kate Martin CNE 12 Lead EKG
Kate Martin CNE Standard Monitor Lead Placement
Kate Martin CNE EASI Lead Placement
Kate Martin CNE EASI View
Kate Martin CNE Continuous ST Monitoring
Kate Martin CNE ST Segment Map
Kate Martin CNE The Coronary Arteries
Kate Martin CNE Anterior Leads I & V 1 -4 LAD LM
Kate Martin CNE Lateral Leads av. R, av. L, & V 5 -6 Circumflex
Kate Martin CNE Inferior Leads II, III, & av. F RCA Circumflex
Kate Martin CNE Posterior Leads I & V 1 -4 Mirror Image Posterior Artery
Kate Martin CNE 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/. 06 sec)
Metabolic Abnormalities Producing ST Changes Kate Martin CNE Hypokalemia Hyperthyroidism ST depression ST elevation with T Hyperkalemia Peaked T waves Hypermagnesemia ST depression wave inversion in inferior leads
Medications Producing ST Changes Digitalis ST depression Shortened QT interval Amiodarone Lengthened QT interval Kate Martin CNE
Other Factors Producing ST Changes Kate Martin CNE Pericarditis ST elevation Hypothermia ST depression Pulmonary Infarction Depressed ST segments and inverted T waves in V 1– 3
Kate Martin CNE Effect of Arrhythmias Bundle Branch Blocks ST segment shifts Paced Rhythm ST segments non diagnostic
Kate Martin CNE Response to change in ST Segment Is patient experiencing angina symptoms? Follow ACS protocol Is patient hemodynamically unstable Stabilize
United Hospital’s Nassett Heart Center, St Paul, Minnesota Practice Standard For all patients receiving cardiac monitoring, the default for continuous ST segment monitoring is ‘on’ with alarm set for 2 mm change (depression or elevation_ from baseline. Nurse turns ‘off’ for patients with the following • Intraventricular conduction defect (either left or right bundle branch block) • Pacemakers (where pacing is the dominant rhythm) • Confirmed Pericarditis or myocardial contusion • ST segment ‘sagging’ due to Digoxin Kate Martin CNE Protocol Assessment by RN after ST alarms will include first verifying: • Patient is supine (<45 o backrest elevation) • Leads are correctly placed on clean dry skin If the patient has a 2 -mm ST change sustained for 15 minutes (with or without symptoms) • Nurse will obtain a 12 -lead electrocardiogram to confirm the ST segment changes (standing order) and call a physician
Kate Martin CNE The QT Interval
Kate Martin CNE Pharmacology and the QT Interval A number of drugs are known to prolong the QT interval and include all of the antiarrhythmics
Kate Martin CNE Importance of QT monitoring QT prolongation can indicate a risk of severe arrhythmias, torsades de pointes, and sudden cardiac death.
Kate Martin CNE 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
Kate Martin CNE QT Monitoring
Kate Martin CNE Setting Alarms
Kate Martin CNE 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.
Kate Martin CNE 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, Ph. D. , Dean Stephens, RN, MS
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