[Music] welcome to this presentation on electrophysiology Foundation session three we'll begin this presentation by discussing the beginning steps of basic egm interpretation we are most familiar with the 12 lead ECG which represents a summation of all electrical vectors recorded from the surface skin remember the various criteria for a surface ECG paper speed of 25 mm/ second calibration 10 mm per 1 molt heart rate identified by beats per minute and a standard 3x4 grid plus a rhythm strip the egm represents a record in of electrical vectors from within the heart chambers in a localized area in comparison to the ECG this has a very different look intracardiac signals are typically less than 10 molts therefore requiring amplification and filtering for optimal viewing in addition we adjust the paper speed known as The Sweep speed in the EP lab to to a more rapid speed to stretch out the complexes let's discuss the criteria for proper egm display due to the rapid conduction system rates we increase the sweep speed to record at a range between 100 to 200 mm/s this will help stretch out the complexes and allow for visualization of the various components within a smaller section of the conduction p pathway signals are Amplified and filtered to avoid extraneous signals or noise three types of filters are generally used to help avoid unwanted noise the high pass filter allows signal higher than preset frequency to pass through in other words filters out low frequency signals such as wandering Baseline the low pass filter allows signals less than a preset frequency to pass through in other words filter out high frequency signals a notch filter is a specialized filter that will eliminate signals at a specific frequency such as 60 hertz which is found in most electrical equipment in North America in the EP lab the typical filter settings used include a high pass filter of 30 HZ and a low pass filter of 500 HZ allowing signals between 30 HZ and 500 HZ to be recorded if you apply the notch filter then any signals at 60 HZ will not be recorded one important note about the notch filter is that we do not apply this to the his channel as it will filter out the H signal this is a much different in comparison with surface ECG settings of 0.5 Herz to 100 Herz we are quite used to expressing cycle lengths in terms of beats per minute but in the EP lab all cycle lengths are expressed in millisecs all protocols and measurements are indicated with this unit the cycle length is a simple calculation of 60,000 divided by the heart rate remember this calculation from our pacemaker studies an easy pattern to remember is that shorter cycle Lings will have faster heart rates some examples are 60 beats per minute equal 1,000 milliseconds 100 beats per minute equal 60 milliseconds and 200 beats per minute equals 300 milliseconds let's take a moment now to discuss the main intervals that are measured on an egm during normal sinus rhythm we are basically breaking down the PR interval into smaller intervals and a wve on an egm represents atrial depolarization which also correlates with the p wve on the ECG the PA interval represents intraatrial conduction time or the time it takes the signal to go from the SA node to the AV node the PA interval is measured from the earliest recorded atrial activity which will either be the p-wave on the surface ECG Channel or the earliest a wve on any channel to the a wve recorded on the his channel the normal values for the PA interval are between 20 to 60 milliseconds an H wve represents that the signal has arrived at the bundle of hiss the ah interval is identified by two waveforms the a-wave and the H wve which represents the conduction time through the AV node the ah interval is measured from the a wve to the h-wave on the his Channel with normal values between 50 to 130 milliseconds a v wve represents ventricular depolarization the hvv interval is identified by two waveforms the h-wave and the v-wave which represent conduction time through the bundle of hiss bundle branches and to the ventricular Moc cardium the h V interval is measured from the h wave on the his channel to the first V wve seam the first v-wave often is shown as a QRS complex on the surface ECG the normal values for the h v interval are between 35 to 55 milliseconds just a reminder that cycle lengths are expressed in milliseconds the basic cycle length will be the distance between success a waves on the H catheter during normal sinus rhythm which measurement represents the time a signal spends traveling through the AV node the answer is the ah interval when EP studies are done to evaluate Brady arhythmia the focus of the study is on the ESS node as sa nodal dysfunction is suspected the snrt or SNT is sinus node recovery time and this measurement is done to assess the sinus node automaticity and identify if any sinus node dysfunction is present the snrt is measured by a particular protocol that is also known as overdrive suppression that will assess the signus knowns ability to recover after a period of inactivity and then spontaneously generate an Impulse the h a catheter will Pace the heart and overdrive theosone at a rate that is slightly faster than the underlying resting heart rate for a period of 30 to 60 seconds after after the 30 to 60c period the catheter will terminate pacing and the recovery time from the last paced hob be to First intrinsic a signal or intrinsic sinus beat is measured as a snrt the upper limit of a normal snrt is 1,500 milliseconds the upper limit values may alter from different EP lab sites due to the fact that there are a number of factors that it affect the snrt such as high levels of Paras sympathic tone and beta blocker treatment these two factors will adjust underlying resting heart rate or cycle length which will affect the snrt and not indicate sinus node dysfunction in order to compensate for these variances we use the corrected sinus node recovery time or csnrt this phenomenon is very similar to adjustments in QT interval and the need to use the corrected QT formula the formula for corrected snrt is the snrt minus the BCL or basic cycle length and the upper limit of normal will then be 525 milliseconds these two images show the various intervals measured measured during an EP study it is important to train your eyes to move in an upward and downward motion to relate the egm intervals to the surface ECG intervals once again we are relating the concept of ECG components to egm components the image on the left shows normal ECG conduction Pathways and the image on the right shows the components identified by the egm note that the p-wave correlates with the atrial signal that is identified by an a-wave and can be seen on the H and his channels the h-wave identifies that the signal has arrived at the door of the his bundle the V signal is the ventricular activation that correlates with the Qs on the ECG measuring conduction time through the atrium to the ventricles on the ECG is known as the PR interval but we can further break that interval down the PA interval is the approximate p-wave length and refers to intraatrial conduction time the ah interval represents time to travel through the AV node and HV interval represents the time taken to travel from the bundle hiss to bifurcation of the ventricular branches these two signals combined relate closely to the pr segment combine all of these intervals together to create the pi interval Pi interval equals PA plus ah plus hvv let's take a look at a typical egm display monitor the top three channels will always be chosen surface ECG lead s and I've pointed out the P and R way for easy reference following downward we see two RVA channels proximal and distal channels identifying a waves the next two channels are the proximal and distal his channels which can identify a h and V waves on the distal Channel they are very small deflections the a wave is noted with a wider star and the H wve is noted with a taller star remember that the RVA and his leads are generally quadripolar leads the next five channels show the Cs or cor sinus leads and can show us a and v waves remember that CS leads are generally decapolar so we can create five channels from the pairs of electrodes the last two channels are the RVA leads and can identify Fe waves let's discuss the signal sequence during normal sinus rhythm now that we have gained some understanding of the different signals identified and measured the First Signal will be the first Ave or onset of the surface p-wave as the impulse exit out of the sinus node the second signal will be the hiss a wve as the Imp pulse has now arrived at the AV node the third signal will be the a signal on the most proximal CS channels and we can then follow the a waves from the proximal to the far distal recordings along the Cs channels the fourth signal will be the H signal on the his channels as the impulses traveled through the AV node to arrive at the hiss bundle the fifth signal will be either the RVA V signal or the surface curus whichever is seen first which will indicate the impulse has begun to depolarize the ventricular Moc cardium the six signal is the V on the his channel and also the CSV which will indicate the impulse has reached the base of the ventricles as you follow this pattern try to visualize the location of the leads within the heart and gain understanding of the signal pathway and how it will be picked up by each Channel remember to pay close attention to the distal and proximal ends of each leads and this will help you understand which channel will pick up the signals first let's relate the intracardiac signals to something we're a bit more familiar with the surface ECG whereas the p-wave and QRS on the ECG represent a summation of all the vectors that occur during atrial and ventricular depolarization signals on the electrogram represent very localized activity as depolarization passes through the tissue near the recording electrodes on specific catheters The highride Atrium catheter will record an a-wave correlating with the beginning of a p-wave once the signal exits the sinus node indicating that the signal has begun to spread throughout the right atrium the his catheter will record an a-wave as the signal reaches the AV node which is about the midpoint of a sinus P wve the Cs catheter will record a waves as the signal spreads across the left atrium representing approximately the last half of the p-wave the proximal electrode pair on the Cs catheter sits close to the atrial septum and the distal electrode pair of the Cs catheter sits close to the left atrium free wall therefore we see a sinus origin signal spread from the proximal electrodes to the distal electrodes on the Cs catheter as the signal spreads from atrial septum to La free wall the pr segment is seen as an isoelectric period on the ECG however with the his catheter sitting next to the AV node and the hiss bundle we can record a small signal called the H or the hiss bundle electrogram as the electricity exits the AV node and depolarizes a small amount of local myocardium low in the r Atrium before traveling through the hiss bundle that signal continues through the distal conduction system and first exits into ventricular my cardium at the distal ends of the bundle branches this is why we first see a v signal representing ventricular depolarization on the right ventricular Apex catheter as the QRS continues the signal spreads upward toward the his catheter near the base of the right ventricle which is where we see the sixth and final signal of the electrogram the his V also at the end of the QRS timing with the his V we may see V signals on the Cs catheter to depending how much contact the Cs catheter has with the base of the left ventricle we've discussed how the individual intracardiac electrograms correlate with the ECG specifically the a-waves time with the p-wave the h-wave times with the pr segment and the v-waves time with the QRS utilize this slide and the previous slide to begin your assignment be sure to take in the weekly meeting before finalizing and submitting your assignment as more information will be given on how to identify the PA ah and HV intervals that make up the PR interval in normal conduction the a signal will be seen in which sequence on the Cs catheter proximal 910 to distal two or distal one two to proximal 910 the answer is proximal 910 to distal two here is a visual of the normal sinus rhythm signal sequence and activation look upwards and downwards to connect the surface ECG components to the egm components atrial activation in normal sinus rhythm will first be seen as an a-wave on the H Channel or p-wave on surf surface ECG we can then follow atrial activation down the channels a waves are seen on the Cs channels following in downward diagonal from proximal to distal as the atrial depolarization moves from right to left atrium remind yourself that the sweep speed has been increased to 100 to 200 mm/s to stretch out the components notice also the h wve on the his channels more evident on the distal Channel with a tiny reflection on the proximal Channel ventricular activation is seen first on the RVA Channel which lines up with the surface QRS complex and we see the activation in a much more linear line moving through the his and CS channels activation through the Cs channels is again proximal to distal as left rric activation will be picked up on the distal channels remember the location of the distal CS channels would be in the left side of the heart along the AV Groove that takes us to the end of this presentation on electrophysiology Foundation session three [Music]