Patient - EN
This 66-year-old man received an Ellipse™ VR Saint Jude Medical ICD for the management of ischemic cardiomyopathy with depressed left ventricular ejection fraction. A remote monitoring message was transmitted for episodes of VT and SVT.
Graph and trace
Tracing 4A
- sinus tachycardia;
- sudden onset of regular tachycardia; its morphology is visibly different from the sinus rhythm complexes despite a >90% similarity;
- after 30 T classified cycles, the VT counter is full; diagnosis of SVT; while the sudden onset and stability criteria are in favor of VT, they did not contribute to the diagnosis since they were programmed on “passive”; the morphology criterion is in favor of SVT (the programmed threshold of similarity was >90%) and was the only criterion programmed ON;
- the discrimination analysis is repeated every 6 T cycles; morphology consistent with SVT;
- VT diagnosed when the similarity of morphology fell below 90%; a burst was delivered;
- subtle acceleration of the rate followed by termination of tachycardia and diagnosis of return to sinus rhythm;
Tracing 4B
- similar episode;
- diagnosis of SVT;
- diagnosis of SVT confirmed every 6 T classified cycles;
- spontaneous termination after >23 minutes of poorly classified VT.
NID old - EN
2912
These tracings illustrate the limitations of a discrimination based solely on morphology. This patient presented with episodes of septal VT with a QRS morphology during tachycardia resembling sinus rhythm, which confused the morphology criterion and caused the erroneous diagnosis of SVT. The use of the sudden onset and stability criteria, on the other hand, would have allowed an accurate diagnosis of VT, had they not been programmed on “passive”. This example illustrates the challenge represented by an optimal programming for all. This case might have been solved by one of two choices: 1) the nominal programming of the 3 criteria ON and a 2/3 setting, i.e. 2 criteria satisfied for a diagnosis of VT, or 2) increase of the percentage defining a similarity between reference and VT complexes from 90 to 95%. This percentage was below 95% in the clear majority of QRS complexes during VT and >95% of the complexes during sinus rhythm, thus offering a better sensitivity/specificity ratio.