Interpreting t wave alternans tests
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Interpreting T Wave Alternans Tests. Daniel M. Bloomfield, MD Herbert Irving Assistant Professor of Medicine Director, Syncope Center Columbia Presbyterian Medical Center Columbia University College of Physicians & Surgeons. Positive and Negative Tests. Positive Tests:

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Interpreting T Wave Alternans Tests

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Interpreting t wave alternans tests

Interpreting T Wave Alternans Tests

Daniel M. Bloomfield, MD

Herbert Irving Assistant Professor of Medicine

Director, Syncope Center

Columbia Presbyterian Medical Center

Columbia University College of Physicians & Surgeons


Positive and negative tests

Positive and Negative Tests

  • Positive Tests:

    • Alternans present below a heart rate of 110 bpm

  • Negative Tests:

    • Alternans not present below a heart rate of 110 bpm and

    • You are confident that there are no artifacts obscuring alternans


Fundamental questions for the interpretation of twa

Fundamental Questions for the Interpretation of TWA

  • Is sustained alternans present?

    • If yes: is it real or artifactual?

    • What is the threshold (onset heart rate)?

  • If alternans is not present, are there artifact present which could be masking true alternans?


Definition of significant alternans

Definition of Significant Alternans

  • Valt 1.9 V

  • K score  3

  • Leads

    • single orthogonal leads

    • two adjacent precordial leads

  • Duration

    •  10 seconds


What is sustained alternans

What is sustained alternans?

  • Duration of alternans

    •  1 minute

  • Relationship of alternans to heart rate

    • alternans must persist above a patient specific heart rate threshold

  • “Heart rate centric” view of alternans


Significant vs sustained alternans

Significant vs. Sustained Alternans

  • Both require

    • Valt  1.9 V

    • K  3

  • Sustained is  1 minute and consistently present above threshold heart rate

  • Significant alternans must only be 10 seconds in duration and need not be present above a threshold heart rate (non-sustained)


What is onset heart rate

What is onset heart rate?

  • Heart rate threshold above which significant alternans is consistently present

  • Can read onset heart rate during increase in heart rate in exercise (preferable) or during decrease in heart rate in recovery

  • In precordial leads: read onset heart rate when 2 adjacent leads have significant alternans


What is a positive tracing

What is a positive tracing?

  • Sustained alternans

    •  1.9V

    • K  3,

    • for  1 minute in duration

  • Threshold heart rate

    • Onset HR must be below predetermined threshold heart rate (currently 110 bpm)

  • Artifact free interval

    • documented as dark black bar


Rest alternans

Rest Alternans

  • Sustained alternans is present at lowest smoothed heart rate

    • regardless of whether this lowest smoothed heart rate occurs at the beginning of the tracing

  • Rest alternans is classified as positive regardless of the OnsetHR

  • “rest” does not refer to a stage of the exercise test

  • MaxNegHR = 0


Interpreting t wave alternans tests

Is Sustained Alternans present?

yes

no

MaxNeg HR?

Present at Rest?

 105

yes

< 105

no

OnsetHR?

Indeterminate

Tracing

Negative Tracing

Rest Positive

 110

> 110

Positive Tracing

MaxNegHR?

 105

< 105

Indeterminate

Tracing

Negative Tracing


Interpreting twa in the presence of artifacts

Interpreting TWA in the Presence of Artifacts

  • Artifacts which can cause alternans (false alternans)

  • Artifacts which can obscure (or mask) true alternans


Artifacts causing alternans

Artifacts Causing Alternans

  • RR interval alternans

  • Ectopic beats

  • Rapid changes in heart rate

  • Excessive noise

  • Motion artifact

  • Respiration


Interpreting alternans during periods of potential artifacts

Interpreting Alternans During Periods of Potential Artifacts

  • Wary of considering alternans “real” if only present during periods of potential artifacts

  • Characteristics of alternans may be helpful

    • relationship to heart rate

    • alternans during artifact free intervals


What is a negative tracing

What is a negative tracing?

  • Tracing without sustained alternans

    • or with sustained alternans with an OnsetHR > 110 bpm

  • MaxNegHR  105 bpm

    • Clean interval with interval heart rate  105


Maximum negative heart rate

Maximum Negative Heart Rate

  • Highest interval heart rate at which sustained alternans is definitively not present


Clean interval

“Clean interval”

 1 minute

  • without significant alternans

  • without artifacts that could potentially obscure alternans

    • < 10 % ectopic or bad beats

    • noise levels < 1.8 V


Maximum negative hr without gap positive tracing

Maximum Negative HR Without Gap:Positive Tracing

Onset HR

Max HR

1 min

Max Neg. HR

Sustained Alternans

Clean Interval


Maximum negative hr with gap positive tracing onset gap

Maximum Negative HR with Gap: Positive Tracing (Onset Gap)

Onset HR

Max HR

Clean Interval

1 min

Max Neg. HR

Sustained Alternans

Ex 2.13


Factors that may obscure alternans

Factors That May Obscure Alternans

  • Noise

    • loss of K score

    • reduce alternans voltage (complete loss of alternans uncommon)

  • Ectopic beats

    • high levels of alternans may rapidly disappear and reappear centered on an ectopic

  • Rapid changes in heart rate

    • especially immediately after exercise

    • look carefully at the instantaneous heart rate

Ex 2.5, 2.6, 2.9


Interpreting t wave alternans tests

Is Sustained Alternans present?

yes

no

MaxNeg HR?

Present at Rest?

 105

yes

< 105

no

OnsetHR?

Indeterminate

Tracing

Negative Tracing

Rest Positive

 110

> 110

Positive Tracing

MaxNegHR?

 105

< 105

Indeterminate

Tracing

Negative Tracing


Effect of factors that may obscure alternans

Effect of Factors That May Obscure Alternans

  • Interpreting gaps in sustained alternans

  • Interpreting maximum negative heart rate in the presence of factors that may obscure alternans


Gaps in sustained alternans

Gaps in Sustained Alternans

  • Duration of the gap relative to duration of sustained alternans

  • Explicable vs. inexplicable gaps

  • Characteristics of alternans

    • relationship to heart rate

    • alternans during artifact free intervals

    • confirmation in other leads


Maximum negative heart rate in the presence of factors that obscure alternans

Maximum negative heart rate in the presence of factors that obscure alternans

  • Heart rate above which you are confident that alternans is not present

  • Confidence is affected by these factors that may obscure alternans

  • Maximum negative heart rate is the highest interval heart rate of all “clean” intervals”


Maximum negative hr with gap negative tracing

Maximum Negative HR with Gap:Negative Tracing

Max HR

1 min

Max Neg. HR

Non-sustained

Alternans

Clean Interval


Maximum negative hr without gap negative tracing

Maximum Negative HR Without Gap:Negative Tracing

Max HR

1 min

Max Neg. HR

Clean Interval


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