This tracing illustrates the value of a discrimination based on the morphological analysis that is now available on the latest Biotronik^TM ICD platforms. This patient had episodes of atrial tachycardia (sudden onset + stable rhythm) that would have been poorly discriminated with the older devices.

The operation of this new discrimination parameter can be divided into several key points:

1. the analysis of the morphology of the QRS complexes is performed during a calculation window of 250 ms; the right ventricular bipolar sensing channel triggers the analysis since the window begins 100 ms prior to the sensing of a spontaneous QRS complex and ends 150 ms thereafter;
2. while the bipolar channel serves as a trigger for the analysis, the morphology calculation is subsequently exclusively performed from the far-field channel (RV coil – pulse generator) with measurement of the following 3 morphological characteristics:

– maximum amplitude

3. a reference signal, which will be subsequently compared to the tachycardia signals, is determined from the signals classified as VS with a rate under 100 beats/minute; at least 32 QRS complexes are needed; this reference signal is reset to zero every night and after each delivered therapy; the variance of the average QRS complex is also calculated from all the spontaneous complexes of lower frequency than the lowest VT zone;
4. the analysis of the morphology is performed in the VT zone but not in the VF zone; it should be noted that this analysis cannot be performed on complexes classified as VT with a rate higher than 230 beats/minute (if the VF zone is programmed very high), the 250 ms analysis window limiting the analysis capacity for very fast rhythms; the comparison with the reference signal is based on the sum of the differences between the three morphological characteristics:
5. according to the analysis of the morphology, the up and down counter of the VT zone is more or less incremented;
6. when the VT counter is full, the device uses its VT morphology counter to make a decision:
7. the morphology (MorphMatch) parameter is available on all new devices (single-, dual- or triple-chamber) and can be programmed to ON, OFF or Monitoring; it should be noted that for the dual- or triple-chamber ICDs, it is necessary to chose between the analysis by the SMART algorithm or by MorphMatch (SMART OFF).