Kate Martin CNE

Beyond ArrhythmiasST & QT Segment Monitoring

Kate Martin CNEApril 2009

Kate Martin CNE

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.

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 factorsST segment changes may be an indication for a 12 lead EKG

Kate Martin CNE

Establishing ST Monitoring

On Admission Ensure skin is properly preppedEnsure leads are in proper positionRecord 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 monitorChoose the leads which monitor the area of the heart most at risk

Kate Martin CNE

12 Lead Limb Lead Placement

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12 Lead Precordial Lead Placement

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12 Lead View

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12 Lead EKG

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Standard Monitor Lead Placement

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EASI Lead Placement

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EASI View

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Continuous ST Monitoring

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ST Segment Map

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The Coronary Arteries

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Anterior Leads

Leads I & V1-4

LAD LM

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Lateral Leads

Leads avR, avL, & V5-6 Circumflex

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Inferior Leads

Leads II, III, & avF RCA Circumflex

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Posterior Leads

Leads I & V1-4

Mirror Image Posterior Artery

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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)

Kate Martin CNE

Metabolic Abnormalities Producing ST Changes

Hypokalemia ST depression

Hyperkalemia Peaked T wavesHypermagnesemia

ST depressionHyperthyroidism ST elevation with

T wave inversion in inferior leads

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Medications Producing ST Changes

Digitalis ST depression Shortened QT interval

Amiodarone Lengthened QT interval

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Other Factors Producing ST Changes

Pericarditis ST elevation

Hypothermia ST depression

Pulmonary Infarction Depressed ST segments and inverted T

waves in V 1 – 3

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Effect of Arrhythmias

Bundle Branch Blocks ST segment shifts

Paced Rhythm ST segments non diagnostic

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Response to change in ST Segment

Is patient experiencing angina symptoms?

Follow ACS protocolIs patient hemodynamically unstable

Stabilize

Kate Martin CNE

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

Practice Standard ProtocolFor all patients receiving cardiac monitoring, the default for continuous ST segment monitoring is ‘on’ with alarm set for 2mm 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

Assessment by RN after ST alarms will include first verifying:• Patient is supine (<45o backrest

elevation)• Leads are correctly placed on

clean dry skinIf 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

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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 monitoringQT prolongation can indicate a risk of

severe arrhythmias, torsades de pointes, and sudden cardiac death.

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What is a QTc?

The QT has an inverse relationship to HR.

QT = QTc at a HR of 60 bpm onlyHeart rate corrected QT interval is

abbreviated as QTcNormal QTc is < 460 ms

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QT Monitoring

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Setting Alarms

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QT Measurement Limitations

“Cannot Analyze QT” INOP message:Flat T, Atrial Fib/FlutterProminent U WavesHighly 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 AlertCritical 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