Detection and treatment of a VF episode - Resonate CRTD

• this first trace illustrates the primary function of an implantable defibrillator: detection and treatment of ventricular fibrillation (an arrhythmia that is initially extremely rapid, polymorphic and disorganized) with a shock.
• at the top of the first page of the PDF transmitted to the LATITUDE telemonitoring site you will find various pieces of information: patient’s surname, first name, date of birth , implantation center, remote monitoring center, device model and serial number, date of last face-to-face interrogation and date of last telemedicine transmission; the tracings in this book have all been anonymized; the ventricular tachy mode is set to «monitoring + treatment», which means that the full range of detection and treatment options is activated.
• each recorded trace is numbered in chronological order (this is episode 42) along with the date and time of occurrence and information pertaining to the atrial and ventricular rate
• the detail tab summarizes the main diagnostic and treatment steps undertaken for this episode; VF Event Onset: ventricular rate (321 beats/minute) and atrial rate (64 beats/minute) are calculated from the average of the 4 ventricular and atrial cycles preceding the V-Epsd marker; during V-Detect : atrial rate (65 beats/minute) and ventricular rate (297 beats/minute) are calculated by averaging the 4 cycles preceding the V-Detect marker; the episode is always detected in the VF zone; in this zone, no discrimination other than rate is used; on the other hand, various parameters are still recorded (stability, V>A frequency, Fib A, correlated Rhythm ID) even if they do not influence the decision to treat the episode; information on the various timers (SRD, ATP Time-ou t) is also displayed; Attempt 1, 41 J V Shock: the first therapy programmed in the VF zone is a 41 Joule shock; the duration of the charge was 9.8 seconds (expected for a maximum-output shock) with a lead impedance of 76 Ohms (expected for a single-coil lead); the shock waveform is biphasic and the nominal initial polarity corresponds to a cathodic shock (for a single-coil lead, the right ventricular coil is the cathode and the defibrillator can is the anode for the first phase, with polarities reversed for the second phase).
• when a trace is analyzed from the programmer, it is possible to modify the scrolling speed (25 mm/s in the first instance); this can be useful for confirming the diagnosis of oversensing of a 50 Hz signal (scroll speed of 100 mm/s reveals a sinusoidal pattern with 20 ms between signals); calibration is adapted automatically by the device, but can also be modified from the programmer to facilitate manual measurement of the amplitude of the various signals
• for each trace recorded on a dual- or triple-chamber defibrillator, 3 channels are nominally available: the bipolar atrial sensing channel (A), the bipolar ventricular sensing channel (V) and the shock channel (shock) between the distal coil and the can; the signal on the shock channel is similar to an electrocardiographic lead; ; markers and intervals are also available; compared with other manufacturers, Boston Scientific have chosen to provide a great deal of information on the trace, with numerous markers (for this example, atrial, right and left ventricular markers, PVARP prolongation , correlated cycles , etc.).)
• to start recording an arrhythmia, 3 consecutive beats must occur in one of the tachycardia zones; the device then uses a sliding window during which it looks for the occurrence of 8 out of 10 consecutive rapid cycles; the first 3 cycles are included in this window; when this criterion is met, the V-Epsd marker appears on the trace; the duration starts from this marker; for Boston Scientific devices, a specified number of rapid cycles is not programmed for initial detection, but a duration during which the arrhythmia is sustained; an episode is considered sustained if a minimum proportion of 6 rapid cycles out of 10 is maintained throughout the duration; if, until the end of the duration, the 6/10 criterion is met, the device classifies the episode as VT, SVT or VF; when the duration ends, the last ventricular interval is analyzed to understand the dynamics of the arrhythmia: stable arrhythmia, slowing down or accelerating; if the last interval corresponds to the zone whose duration has just ended, therapies can be delivered; the end of an episode is declared after a duration during which the 8/10 redetection criterion is not met (10 seconds after untreated events, ATP treated events or after an aborted shock; 30 seconds after a delivered shock)
• there are three programmable durations: initial duration (independently programmable in VF and VT zones), post-detection duration (when a charge has been diverted or after an ATP sequence; programmable in the VT zone, fixed at 1 second in the VF zone) and post-shock duration (after a shock has been delivered; programmable in VT zone, fixed at 1 second in VF zone)
• the interval plot provides an overall view of the episode, with a number of characteristic aspects to be aware of (railroad track appearance cases of P wave oversensing , T wave oversensing or double counting of the R wave, cloud of points with very short cycles in the case of lead dysfunction, undersensing with long cycles in the case of a VF episode, etc.).); interval plot analysis is therefore an integral part of reading the various tracings, and should probably be the first step before detailed analysis of the EGM.

This figure shows the 3 available channels with a good-quality color EGM plot and a multitude of markers (lots of information, the plot is sometimes a little busy).