Marker channels

FIGURE 15.6 Record stored by an ICD of successful delivery of a defibrillation. An atrial EGM, (top tracing), ventricular electrogram (middle tracing), and ICD marker channel are shown. Markers include ventricular sense (VS), atrial sense (AS), ventricular pace (VP), atrial pace (AP), end of ICD capacitor charge (CE), and delivery of shock (CD). (Reproduced with permission of Medtronic, Inc.)... 

Fig. 3.10 Example of WI pacing from Fig. 3.2 with refractory periods added. The ventricular refractory period (VRP) has an initial absolute blanking period (solid black). During the absolute blanking period, no sensed events are noted in the marker channel. During the remaining portion of the VRP, the relative lefiactory period (gray), sensed events may be noted, but the LRL will not be reset.

Fig. 12.2 An example of atrial fibrillation (AF) organizing into atrial flutter. A. The upper strip in the top panel demonstrates the atrial electrogram (EGM) and the lower strip demonstrates the annotated markers indicating how the pacemaker classifies each atrial and ventricular event as well as the cycle length (in ms) between each interval. The atrial electrogram shows the rapid irregular atrial rhythm which subsequently transitions into an organized atrial tachycardia. B. Atrial antitachycardia pacing (ATP) therapy - a burst train followed by two premature extrastimuli is delivered restoring atrial paced rhythm. The marker channel notations indicate how the device classifies each beat. Inter-beat intervals are also shown (in ms). AP - atrial paced event VP - ventricular paced event AR - atrial event sensed in atrial refractory period FS - AF sensed event TD - tachycardia detected TS - tachycardia sensed event. Courtesy AM Gillis.

Fig. 204 Baseline electrograms from a patient are shown. The R waves on the bipolar electrode (EGM2) are approximately 8 mV. Notice that the T waves are approximately 2mV. The marker channels show that at baseline the ICD is appropriately counting the R waves (VS) but not the T waves. Chart speed 25.0mm/s.

Sensing Problems Sensing problems in the lead/lCD system, such as T-wave sensing, double counting of pacing stimuli, and lead/conductor failure, were reviewed earlier. Real-time measurements and marker channels are very useful in this setting. The chest radiograph will identify some types of lead problems (Chap. 18). In some cases, implantation of a new lead is required unfortunately. 

The initial VEGM shows VF. The initial shock does not convert this to sinus rhythm. The rhythm however then organizes after the first shock into a slow VT at a rate of 140 b.p.m. Each R wave during the VT is double counted (see marker channels) causing a redetection in the VF zone and subsequent successful conversion. 

The marker channel shows frequent T wave oversensing on the VEGM. 

After VF induction the asynchronous pacing spikes can be seen marching through the surface lead strip. The pacing spikes do not have any effect on the detection of VF as can be seen by noting the absence of undersensing on the marker channels. 

There are two predominant R wave morphologies seen on the VEGM. Along with the marker channels at the top are annotations designating whether each ventricular beat did (V mark) or did not (X mark) match the baseline R wave template. There appears an admixture of both marks, depending on which R wave morphology was seen. Thus, the ICD may not be able to confirm an SVT based on morphology discrimination. 

The single EGM is measured between the atrial and ventricular lead tips. This displays both an atrial and ventricular EGM component, and allows one to see an atrial tachycardia conducting 2 1 to the ventricles. The EGM recording ceases (normal device function per the manufacturer), but the marker channels show a single round of atrial burst overdrive pacing that fails to terminate the arrhythmia (in fact it temporarily speeds it up). 

Figure 13.1 Monitor (FID) (a) and analytical (ECD) (b) channel responses for PCB congeners in Aroclor 1254, showing selection of the six heart-cut events Frr-st columns, HT8 second columns, BPX5. Reprinted from Journal of High Resolution Chromatography, 19, R. M. Kinghorn et al., Multidimensional capillar-y gas chr omatography of polychlorinated biphenyl marker compounds , pp. 622-626, 1996, with per-mission from Wiley-VCH.

Preliminary biological tests showed the compatibility of Im Hb with blood and the theoretical possibility of intravenous injection and functioning in the organism. The use of microparticles of Im Hb with a covalently bonded marker permitted the determination of the time of microparticle circulation in the blood channel of rats. After 7 h. of observation, up to 30% of the introduced amount of Im Hb was retained in the blood of the animals. 

FIGURE 7.5 7,8-BPQ increases intracellular Ca2+ in murine spleen cells (A) and in both B and T cells (B). Single cell suspensions were prepared from murine spleens. Splenocytes were loaded with Fluo-3/AM dye for one hour and then treated with 7,8-BPQ, 1,6-BPQ, 3,6-BPQ, or DMSO (control). Surface-marker-defined T cells and B cells were treated with 7,8-BPQ or DMSO. Following treatment, the immediate intracellular Ca2+ response was continuously monitored for 15 minutes. Results are shown as the change in Mean Channel Fluorescence SEM. The numbers shown in this figure were the averages of triplicate determinants. Adapted from Gao et al., 2005. 

Camacho-Arroyo, I., Duenas-Gonzalez, A., Perez-Cardenas, E., Pardo, L.A., Morales, A., Taja-Chayeb, L., Escamilla, J., Sanchez-Pena, C. and Camacho, J. (2004) Ether a go-go potassium channels as human cervical cancer markers. Cancer Research, 64, 6996—7001. 

Figure 2.10 The Loc-I-Gut instrument allowing segmental intestinal perfusion in humans. The balloons are filled with air when the proximal balloon has passed the ligament of Treitz. The six-channel tube facilitates infusion of drug and marker, aspiration of perfusate and gastric drainage, and inflation of the two balloons [60].

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