Single-chamber discrimination and optimization of the criterion based on morphology
Patient
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Man implanted with a single-chamber Ellipse VR defibrillator as part of primary prevention for dilated cardiomyopathy
Trace
- sinus rhythm (VS)
- onset of regular, monomorphic tachycardia with complexes of visually different morphology compared to complexes in sinus rhythm
- Relatively high correlation percentages (between 84 and 92%) but consistently below the programmed threshold value (95%)
- VT2 counter completed; VT and burst diagnosis delivered
- Effective burst and sinusoidal return diagnosis
Comments
VT diagnostic criteria: morphology and stability during exercise, sudden onset at rest The three programmed discrimination parameters are consistent with V
Points to remember
- In this example of appropriate therapy for septal VT, the morphological difference between ventricular complexes in sinus rhythm and ventricular complexes in tachycardia is not very obvious; the correlation percentages are relatively high, with values exceeding 90%.
- in this patient, the nominal threshold value had been modified (95%, the maximum programmable value), which made it possible to maintain 100% sensitivity for the diagnosis of VT
- A recent study has shown that for nominal values (90%, minimum of 3 out of 10 correlated), sensitivity and specificity values are high; therefore, probably no point in changing these values as a first step; however, in certain specific cases, it may be necessary to adjust the correlation percentage to make the device more sensitive (increase the percentage) or, conversely, more specific (decrease the percentage)
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