Cardiovascular Nursing Education Associates

Transcription

1 Carol Jacobson RN, MN Cardiovascular Nursing Education Associates Carol Jacobson RN, MN 1

2 Position I: Chamber Paced Position II: Chamber Sensed Position III: Response to Sensing O = None O = None O = None A = Atrium A = Atrium T = Triggered V = Ventricle V = Ventricle I = Inhibited D = Dual (A + V) D = Dual (A + V) D = Dual (T + I) Position IV: Rate Modulation O = None R = Rate Modulation Position V: Multisite Pacing O = None A = Atria V = Ventricles D = Dual (A & V) Carol Jacobson RN, MN 2

3 Is this pacemaker working right? Yes. It is a dual chamber pacemaker functioning in the atrial tracking state. Chamber Paced Chamber Sensed Response to Sensing DVI Atrium Ventricle Ventricle VDD Ventricle Atrium DDD Atrium Ventricle Ventricle Atrium Ventricle Inhibits Triggers Inhibits Triggers Inhibits Carol Jacobson RN, MN 3

4 D D D Paces: Atria and Ventricle Senses: Atria and Ventricle Response to Sensing: Atrial sensing = inhibits atrial output, triggers ventricular output Ventricular sensing = inhibits all output AVI - AV interval or AV delay ARP - atrial refractory period PVARP - post ventricular atrial refractory period AEI - atrial escape interval VRP - ventricular refractory period MTI - maximum tracking interval Carol Jacobson RN, MN 4

5 Pacing Interval AV Interval Atrial Escape Interval (V-A interval) Interval from a sensed or paced ventricular event to the next atrial output spike Amount of time the pacemaker will wait for an intrinsic P wave before it paces the atrium Not programmable Carol Jacobson RN, MN 5

6 Pacing Interval AV Interval Atrial Escape Interval (V-A interval) Period of time when atrial channel cannot respond to atrial activity Begins with paced or sensed atrial activity AVI AVI PVARP Carol Jacobson RN, MN 6

7 PVARP hides really early P waves from the atrial channel and prevents inappropriate atrial tracking Retrograde P Very short ventricular refractory period ( blink ) that occurs with every atrial pacemaker spike (to prevent crosstalk) Carol Jacobson RN, MN 7

8 Begins with sensed or paced ventricular beat Ventricular channel unable to respond to sensed events so it doesn t respond to T wave potentials or other local potentials in ventricle Maximum rate at which the ventricular channel will track the atrial rate Determines the upper rate limit (URL) of the pacemaker keeps ventricular paced rate <URL PAC Carol Jacobson RN, MN 8

9 AVI ARP AEI VRP MTI Possible underlying rhythm: sinus brady and AV block Carol Jacobson RN, MN 9

10 AVI ARP AEI VRP MTI Possible underlying rhythm: sinus brady but intact AV conduction AVI ARP AEI VRP MTI Possible underlying rhythm: sinus rhythm with 3 rd degree AV block Carol Jacobson RN, MN 10

11 AVI ARP AEI VRP MTI AVI ARP AEI VRP MTI Carol Jacobson RN, MN 11

12 Minimum rate Upper rate limit AV interval PVARP Ventricular refractory period Special programmed parameters Carol Jacobson RN, MN 12

13 Atrial Capture Atrial Sensing Ventricular Capture Ventricular Sensing Atrial spike immediately followed by obvious P wave Atrial spike followed by normal QRS Carol Jacobson RN, MN 13

14 Normal P wave followed by a paced QRS within the programmed AV delay In DDD mode there is no such thing as straight ventricular pacing. There is always either an atrial sensed beat or an atrial paced beat before a ventricular paced beat. Ventricular spike followed immediately by wide QRS Carol Jacobson RN, MN 14

15 Atrial spike followed by normal QRS Resetting of atrial escape interval by a PVC AEI AEI reset by sensed PVC What state of pacing is this? AV sequential Atrial capture? Good Atrial sensing? Can t evaluate Ventricular capture? Good Ventricular sensing? Can t evaluate Carol Jacobson RN, MN 15

16 Practice #2 What state of pacing is this? Atrial tracking (A sense, V pace) Atrial capture? Can t evaluate Atrial sensing? Good Ventricular capture? Good Ventricular sensing? Can t evaluate What state(s) of pacing? Atrial capture? Ventricular capture? Ventricular sensing? AV sequential, Atrial pacing, Atrial tracking Atrial sensing? Good Good (beat 6) Good Good (beats 2, 4, 9) Carol Jacobson RN, MN 16

17 Differential AV Delay Shorter AV delay on sensed beats than on AV paced beats Rate Adaptive AV Delay AV delay shortens as pacing rate increases in response to activity Mode Switching Switches to VVI when atrial fib or flutter occurs Shorter AV delay on sensed beats than on AV paced beats Maintains more consistent atrial contraction to ventricular contraction timing between sensed and paced atrial beats Paced AV delay = 200 ms (.20 sec) Sensed AV delay = 160 ms (0.16 sec) Carol Jacobson RN, MN 17

18 AV interval shortens as pacing rate increases in response to activity Pacing rate = 68 AV delay with no activity: 160 ms Pacing rate = 94 AV delay with activity: 120 ms Device switches from tracking (DDD/R) to nontracking (DDI/R) mode when atrial arrhythmias occur Prevents pacer from trying to track rapid atrial rates symptom relief Atrial tracking Onset of atrial flutter MS Pacer tracks atrial rate for a few beats Switches to non-tracking mode paced rate slows Carol Jacobson RN, MN 18

19 One channel of the pacemaker senses something that is occurring in the other chamber o Ventricular channel senses atrial output spike or intrinsic P wave o Ventricular channel thinks the atrial pacing spike is a QRS and fails to pace the ventricle Causes atrial pacing at a rate equal to the atrial escape interval and can result in ventricular asystole if there is no intrinsic conduction to the ventricle Normal Operation Crosstalk Carol Jacobson RN, MN 19

20 Delivery of ventricular pacing stimulus at a short AV delay ( ms) if a signal is sensed early in the AV delay Short AV interval allows for a ventricular output but prevents it from falling on the T wave Used to prevent crosstalk inhibition of ventricular output PVC #1: Early enough to inhibit all pacing PVC #2: Inhibits ventricular pacing PVC #3: Occurs during blanking period and causes safety pace Carol Jacobson RN, MN 20

21 Occur when the intrinsic atrial rate exceeds the upper rate limit Goal is to limit the rate at which the ventricle will pace in response to rapid atrial rates Wenckebach response 2:1 block Maximum tracking interval will not allow ventricular pacing to occur before it times out Max track interval is determined by programmed upper rate of pacemaker In this example there is a sinus tachycardia at rate of about 136. Upper rate limit is 120 (green arrow at bottom). AV delay progressively increases (white part of arrow at top) because max track won t allow a V pace to occur until it times out. The increase in AV delay pushes PVARP (red arrow at top) closer to the next P wave until finally a P wave occurs in PVARP ( ) and is not sensed and therefore does not initiate a V pace, resulting in a pause which keeps the ventricular rate below upper rate limit. Carol Jacobson RN, MN 21

22 When the atrial rate is faster than the total atrial refractory period, every other P wave falls in PVARP and 2:1 block occurs Carol Jacobson RN, MN 22

23 Reentrant tachycardia that occurs only with dual chamber pacemakers Antegrade limb of circuit is the pacemaker Retrograde limb of circuit is retrograde conduction through the AV node or an accessory pathway Caused by anything that causes loss of AV synchrony PVC with retrograde conduction to atria PAC that prolongs AVI Loss of atrial capture Removal of a magnet after pacemaker testing Myopotential tracking Atrial sensing circuit Ventricular output circuit Carol Jacobson RN, MN 23

24 A PVC conducts retrograde to the atrium The atrial channel senses the retrograde P wave and triggers a V pace after a long AV delay (caused by the maximum tracking interval) The V pace results in retrograde conduction to the atrium which is sensed, another V pace is triggered, and PMT occurs Carol Jacobson RN, MN 24

25 PMT Prevention Algorithms + PVARP or ARE (atrial refractory extension) o Automatic extension of PVARP after a PVC to prevent sensing of a retrograde P wave by the atrial channel DVI on PVC o Switches to DVI mode when a PVC occurs (turns off atrial sensing circuit to prevent sensing of retrograde P) PMT Termination Algorithms Interrupts PMT after programmable number of beats by extending PVARP or switching to DVI Carol Jacobson RN, MN 25

26 Dual Chamber Atrial Ventricular Bi-ventricular Right ventricular apex Left ventricle via left cardiac vein Patients with all of the following should receive CRT with or without ICD unless contraindicated: EF < 35% Sinus rhythm LBBB with QRS > 150ms NYHA class II, III or ambulatory class IV despite optimal medical therapy Carol Jacobson RN, MN 26

27 CRT can be useful for the following patients with EF < 35% LBBB with a QRS duration 120 to 149 ms (IIa) Non-LBBB pattern with a QRS duration >150 ms and NYHA class III/ambulatory class IV symptoms (IIa) Atrial fibrillation if near 100% pacing expected (IIa) Non-LBBB pattern with QRS duration 120 to 149 ms, and NYHA class III/ambulatory class IV (IIb) Non-LBBB pattern with a QRS duration >150 ms and NYHA class II symptoms (IIb) LVEF < 30%, ischemic etiology of heart failure, sinus rhythm, LBBB with a QRS duration of >150 ms, and NYHA class I symptoms (IIb) Abnormal ventricular conduction resulting in abnormal mechanical function Poor systolic function Impaired diastolic function Interventricular dyssynchrony - time delay between contraction of right and left ventricles Intraventricular dyssynchrony - abnormal segmental contraction within the LV Carol Jacobson RN, MN 27

28 Both ventricles depolarize at same time Septum moves leftwards and functions as part of LV Mitral valve closes and blood is ejected into aorta Abnormal ventricular depolarization due to LBBB: RV depolarizes normally Septum depolarizes from right side instead of from left side LV depolarizes late and abnormally slowly due to muscle cell-to-cell conduction Carol Jacobson RN, MN 28

29 Abnormal Mechanical Function Septum depolarizes before LV When LV contracts, septum is already relaxed and bulges into RV (paradoxical septal wall motion) LV papillary muscles contract late, allowing mitral valve to evert into LA Reduced forwards flow through aortic valve due to mitral regurgitation LV contraction is delayed, causing LV to contract at same time as LA, reducing LV filling LV relaxes late, causing reduced LV filling during diastole Pacing of RV and LV together Coordinates ventricular contraction Forces septum to contract with LV Reduces both inter and intraventricular dyssynchrony Papillary muscles contract with LV Reduces amount of mitral regurgitation Dual chamber pacing Improves AV timing to optimize ventricular filling Carol Jacobson RN, MN 29

30 Improved systolic and diastolic function Increased stroke volume and improved LVEF Reduced LV volume & dimension (reverse LV remodeling noted with 3 months of CRT) Decreased mitral regurgitation Improved exercise capacity Improved functional class Improved quality of life Decreased hospitalization for HF Reduced mortality (especially when combined with ICD) 36% reduction of all-cause mortality in CARE-HF study From this: To this: Carol Jacobson RN, MN 30

31 Not as easy as your regular RV pacing!! Loss of capture in one ventricle can change the QRS axis and/or QRS shape in multiple leads V 1 Bi ventricular capture Loss of RV capture Intrinsic LBBB conduction (no pacing) 4 ECGs recommended Baseline intrinsic conduction (showing LBBB) RV pacing only LV pacing only Bi-V pacing Use of marker channels on programmers makes it easier to evaluate pacemaker function during follow-up visits Carol Jacobson RN, MN 31

32 Intrinsic conduction V1 II RV Pacing LV Pacing V1 II Bi-V Pacing With biventricular pacing the idea is to FORCE ventricular pacing so that both ventricles contract together AV delays programmed on the short side to force ventricular pacing rather than allowing intrinsic conduction to occur Carol Jacobson RN, MN 32

33 So what s the problem with right ventricular pacing? Ventricular pacing from the RV apex creates the same inter and intraventricular conduction delay as LBBB and causes similar mechanical malfunctions The goal then is to PREVENT ventricular pacing whenever possible Carol Jacobson RN, MN 33

34 Left ventricular electrical and mechanical dyssynchrony (iatrogenic LBBB) LV remodeling LV systolic and diastolic dysfunction Regional wall motion abnormalities Mitral regurgitation Increased risk of atrial fibrillation Increased risk of developing heart failure (even with normal heart function prior to pacemaker insertion) Increased incidence of hospitalization due to HF Left atrial enlargement Promotion of ventricular arrhythmias SNS activation Reduced exercise capacity Sweeney MO, Hellkamp AS, Ellenbogen KA, et al. Adverse effect of ventricular pacing on heart failure and atrial fibrillation among patients with normal baseline QRS duration in a clinical trial of pacemaker therapy for sinus node dysfunction. Circulation. 2003;107:2932 Sweeney, M. O., & Prinzen, F. W. (2006). A new paradigm for physiologic ventricular pacing. J Am Coll Cardiol 47(2), Carol Jacobson RN, MN 34

35 Incidence of atrial fibrillation increases with increasing % of ventricular pacing in both VVI and DDD modes Why? RV pacing delays LV contraction and relaxation Left atrial pressures have to be higher to fill the not yet relaxed LV. Elevated LA pressure causes atrial enlargement which increases risk of AF Alternate pacing sites His Bundle RVOT RV septal sites Bifocal RV pacing (apex and RVOT) LV pacing alone Biventricular pacing Triventricular pacing (RV apex, RVOT, LV) Carol Jacobson RN, MN 35

36 Programming to reduce RV pacing Long AV delay to encourage intrinsic conduction AAI/R mode whenever possible VVI at rate of 40 instead of DDD as backup mode in ICD patients with no indications for pacing Special Pacemaker Functions MVP mode (Managed Ventricular Pacing) AV Search Hysteresis (AVSH) VIP (Ventricular Intrinsic Preference) Provides AAI/R pacing with dual chamber pacing support if transient or persistent AV block occurs Functions as AAI/R and allows intrinsic AV conduction to occur (long AV interval) Monitors ventricle each beat to verify intact conduction Carol Jacobson RN, MN 36

37 Provides ventricular backup pacing only as needed if transient AV block occurs A-A interval with no sensed ventricular event Transient loss of conduction Ventricular backup safety pace AAI/R pacing continues Switches to DDD/R for one minute if AV block is persistent 2 out of 4 A-A intervals without a ventricular event Persistent loss of conduction Switches to DDD/R Carol Jacobson RN, MN 37

38 When in DDD mode, performs AV conduction check every 1,2,4,8 min up to 16 hrs after switch to DDD/R) Inhibits one V pace to check for intrinsic conduction If conduction check fails, continues in DDD/R mode Failed conduction check Continues in DDD/R Next conduction check scheduled to occur at 2x the previous time interval (1, 2, 4, 8 min hrs) If conduction check passes, device switches to AAI/R mode and continues in that mode until conduction fails again Conduction test passes Switches to AAI/R Carol Jacobson RN, MN 38

39 Is this pacemaker working right? Is this pacemaker working right? Atrial pacing with very long AV delay conducting to ventricle normally Failed conduction Failed conduction Backup ventricular safety pace Backup safety pace Switches to DDD/R pacing Carol Jacobson RN, MN 39

40 Functions in DDD/R mode and automatically searches for intrinsic AV conduction Extends the AV delay by 10% - 100% (programmable value) every X cycles (programmable number from 32 to 1024 cycles) to look for intrinsic conduction Searches for 8 cycles Maximum AV delay is 400 ms If intrinsic conduction is present, AV delay remains long until conduction fails, then pacer returns to DDD/R mode Functions as DDD/R pacer Carol Jacobson RN, MN 40

41 Every 32 beats (or programmed number) it extends AV delay by a programmed value for 8 cycles or until intrinsic conduction occurs Search begins Intrinsic conduction occurs ms AV delay remains long until intrinsic conduction fails to occur within the programmed upper AV delay length DDD/R operation returns with conduction failure Long AV delay continues Conduction fails so V pace occurs 240 ms 240 ms 300 ms DDD/R pacing resumes at programmed parameters for another 32 beats, then search starts again Carol Jacobson RN, MN 41

42 V backup safety pace (probably due to loss of conduction on previous A pace) A pace with long PR, intrinsic conduction A pace, loss of conduction (2 nd one) A pace, V backup safety pace, probable junctional escape beat Switch to DDD (2 out of 4 atrial events not conducted) Normal MVP Pacemaker Function! Carol Jacobson RN, MN 42

43 No matter how weird it looks, its probably working right!!! As long as the patient is hemodynamically stable DON T WAKE THE DOC UP IN THE MIDDLE OF THE NIGHT TO REPORT PACEMAKER MALFUNCTION! The only real emergency is loss of ventricular capture resulting in asystole or symptomatic bradycardia Carol Jacobson RN, MN 43