T-Wave Discrimination

Question 1

Is T-Wave oversensing applied at initial detection, re-detection or both?

Answer 1

both, initial and re-detection

Question 2

Which algorithm uses signal-frequency content and pattern analysis to distinguish R-T pattern?

Answer 2

T-Wave Oversensing (TWO)

Question 3

What is the purpose of the T-Wave discrimination algorithm?

Answer 3

to prevent/reduce the chance of inappropriate shocks without compromising VT/VF detection sensitivity

Question 4

What information does the T-Wave discrimination algorithm use to differentiate R and T patterns from VT/VF?

Answer 4

analyzes differences in amplitude, rate, and pattern

Question 5

How do R and T wave frequencies differ and how does the T-wave discrimination algorithm tell the difference?

Answer 5

• R-waves usually have a higher frequency then T-wave
• device uses a differential frequency filter that allows the device to make the R-waves larger which enables pattern recognition

Question 6

How many VS events does the TWO algorithm evaluate?

Answer 6

• sets of 6 VS events

Question 7

How does the T-Wave Oversensing algorithm create the R-wave threshold used to differentiate R- from T-waves?

Answer 7

• looks at sets of 6 consecutive VS events
• takes the avg of the 3 largest sensed R-wave amplitudes
• amplitudes equal to or larger are R-waves, if less then are T-waves

Question 8

The TWO algorithm will analyze VS events in which zone(s)?

Answer 8

TWO will only analyze VS events that are above the VT (TS) or VF (FS) programmed detection zones

Question 9

What does a TW in the marker channel signify?

Answer 9

that TWO algorithm withheld detection and therapy d/t TWOS

Question 10

When will TWO withhold detection and therapy?

Answer 10

• if 4/20 sets of 6 intervals meet T-wave criteria

Question 11

Why does the TWO algorithm evaluate the signal pattern as well as the signal frequency content?

Answer 11

to ensure device can still sense and detect VF

Question 12

Which signal source does the TWO algorithm use?

Answer 12

• near field signals
• RVtip to ring
  or
• RVtip to RV coil

Question 13

Describe the proces used by the TWO algorithm to determine if TWOS is occuring?

Answer 13

1) 6 consecutive VS event sensing signals are differentially filtered
2) avg of the 3 largest signals is used as the threshold for discrimination
3) tentative labeling:
T-wave < threshold < R-wave
4) applies discrimination criteria to both R- and T-waves

Question 14

What are the final 5 discrimination criteria use by the TWO algorithm to finalize the labeling of R- and T-waves?

Answer 14

• R-waves are similar in amplitude
• T-waves are similar in amplitude
• R-R intervals are similar in length
• R/T ratio on filtered and non-filtered EGMs need to be similar (R- higher than T)
• R to T pattern must be present

Question 15

Where will you find the TWOS episodes?

Answer 15

under the Ventricular Oversensing Episodes (VOS) list/section