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Kate Martin CNE April 2009. Beyond Arrhythmias ST & QT Segment Monitoring. 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.

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Kate martin cne april 2009

Kate Martin CNE

April 2009

Beyond ArrhythmiasST & QT Segment Monitoring

Monitoring practice international guidelines
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.


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

Diagnostic testing
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.

Diagnostic relevance
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

Establishing st monitoring
Establishing ST Monitoring

  • On Admission

  • Ensure skin is properly prepped

  • Ensure leads are in proper position

  • Record a baseline ST strip

Choosing your leads
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

Anterior leads
Anterior Leads

Leads I & V1-4

  • LAD

  • LM

Lateral leads
Lateral Leads

  • Leads avR, avL, & V5-6

    • Circumflex

Inferior leads
Inferior Leads

Leads II, III, & avF

  • RCA

  • Circumflex

Posterior leads
Posterior Leads

Leads I & V1-4

  • Mirror Image

  • Posterior Artery

The j point
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)

Metabolic abnormalities producing st changes
Metabolic Abnormalities Producing ST Changes


  • ST depression


  • Peaked T waves


  • ST depression


  • ST elevation with T wave inversion in inferior leads

Medications producing st changes
Medications Producing ST Changes

  • Digitalis

    • ST depression

    • Shortened QT interval

  • Amiodarone

    • Lengthened QT interval

Other factors producing st changes
Other Factors Producing ST Changes

  • Pericarditis

    • ST elevation

  • Hypothermia

    • ST depression

  • Pulmonary Infarction

    • Depressed ST segments and inverted T waves in V 1 – 3

Effect of arrhythmias
Effect of Arrhythmias

  • Bundle Branch Blocks

    • ST segment shifts

  • Paced Rhythm

    • ST segments non diagnostic

Response to change in st segment
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
United Hospital’s Nassett Heart Center, St Paul, Minnesota

Pharmacology and the qt interval
Pharmacology and the QT Interval

A number of drugs are known to prolong the QT interval and include all of the antiarrhythmics

Importance of qt monitoring
Importance of QT monitoring

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

What is a qtc
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

Qt measurement limitations
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.


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