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Triggering It is necessary to establish a reliable trigger signal before balloon pumping can begin. The computer in the IAB console needs a stimulus to cycle the pneumatic system, which inflates and deflates the balloon. The trigger signal tells the computer that another cardiac cycle has begun. In most cases it is preferable to use the R wave of the ECG as the trigger signal. However, there are other trigger options for instances when the R wave cannot be used or is not appropriate. Triggering on the R Wave Since triggering on the R wave of the ECG is preferred, it is very important to give the IABP a good quality ECG signal and lead. Care should be taken when choosing the site of electrode placement and in applying the electrodes to the skin so that artifact is minimized on the ECG. When selecting the ECG Lead that the pump is looking at, it is recommended to pick a lead with unidirectional QRS complexes and whose R waves are taller than the P or T waves to avoid missed triggers or double triggering. It is also recommended to pick a lead with minimal artifact. In addition, avoid leads with minimal QRS voltage. The pump may not be able to gain up the ECG enough in this situation to see the R wave. When bringing the ECG to the pump via the skin leads, the clinician selects an appropriate lead via the pump controls. When bring in the ECG from a bedside monitor, the lead choice is made at the bedside monitor. Good Leads Poor Choices
ECG Gain In addition to selecting a lead with a QRS morphology that provides consistent, appropriate triggering, it is important to ensure the QRS complex has adequate amplitude. The computer has a minimum height requirement to recognize the initial deflection as an R wave, whether upright or negative in configuration.
It is recommended to use the Skin Lead as the ECG source when it is necessary to trigger on the pacer spike. "Slaving" the ECG from the bedside monitor can present problems in this instance. The monitor must be in a specific mode to place pacer flags on the ECG output. (Consult your brand of monitor to find what the mode must be). Even when the correct mode is selected, the amplitude of the pacer flag can vary somewhat potentially causing some missed trigger events.
Intermittent pacing with V Pace trigger Pacer triggers should only be considered if the patient is 100% paced. When a pacer trigger is selected, the pump will only initiate an inflate/deflate cycle when the pacer spike is seen. No pumping will occur on beats without pacer spikes. Instead, choose a trigger that looks at the R wave or the arterial pressure trace since those are always present.
Pacer spikes with tails Pacer spikes that have "tails" can create problems with triggering. The mA was set to 20mA on the strip above. Note the slope to the backside of the atrial pacer spike. Because this tail has slope and height, it is interpreted as an R wave by the computer. In many instances, turning the mA down to just high enough to maintain capture will solve the problem. If this cannot be accomplished, consider using the arterial pressure trigger. Pacer problem If the pacer is not sensing or capturing appropriately a trigger could be missed or occur not in relation to the cardiac cycle. Note on the above strip that the pacer spike occurs within the fifth complex. The computer could not see it buried in the QRS and missed a trigger.
Triggering on the Arterial Pressure Waveform Arterial pressure provides another signal to the IABP to determine where the cardiac cycle begins and ends. It is used when the ECG has too much interference from patient movement, poor lead connection, or noise caused by electrocautery in the OR. There are limitations to triggering on the arterial pressure curve. Irregular Heart Rates and irregular pulse pressures can cause the pump to not see a trigger where it expects to find one. If this happens, pumping will be temporarily interrupted as the computer relearns the parameters. Late deflation will also caused missed triggers and an interruption in pumping. Therefore AP trigger should be considered a backup trigger and not the one used as the primary trigger. Arterial Pressure trigger is the choice during CPR. Once chest compressions are started an arterial pressure waveform will be generated. Triggering on the AP will produce pumping in synchrony to chest compression and has been shown to assist with coronary and carotid perfusion.
Trigger Loss The console MUST see a trigger to initiate an inflate/deflate cycle. If no trigger is seen when the clinician attempts to start pumping, no pumping will occur and an alarm will be sounded. If the trigger is lost after pumping starts, no further pumping will occur until a trigger is re-established. The pump will go to STANDBY and an alarm will be sounded. If the current trigger is lost the clinician can choose an alternate, available trigger to resume pumping. For example, if the ECG lead becomes disconnected the Arterial Pressure trigger may be selected until the ECG is re-established.
Indicators of a valid trigger are:
If the timing appears to be wandering it is generally a trigger problem. When a trigger is recognized it starts the clock on when the inflation/deflation cycle is going to begin.
With the Heart Rate remaining the same, if the trigger is recognized earlier in the cardiac cycle than it previously had been, it will cause inflation/deflation to be that much earlier. With the Heart Rate remaining the same, if the trigger is recognized later in the cardiac cycle than it previously had been, it will cause inflation/deflation to be that much later. This can be avoided by appropriate ECG lead selection and alternate trigger selection. Select pump you wish to review the triggers on.
Caution: U.S. Federal Law limits these devices to sale by or on order of a physician. Contents of unopened, undamaged package are sterile. Disposable. Refer to package insert for current warnings, indications, contraindications, precautions, and instructions for use.
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Note: changing QRS morphology may cause wandering timing
Note: tall T waves may cause double triggering or may alter previously set timing points
Note: wandering baseline may cause skipped trigger
Note: artifact may cause inappropriate triggering
