«Δυσλειτουργία βηματοδότη. Πως μπορούμε να την εκτιμήσουμε στο ιατρείο.» Koσσυβάκης Χάρης Καρδιολογικό Τμήμα Γ.Ν.Α. «Γ. ΓΕΝΝΗΜΑΤΑΣ

Transcription

1 «Δυσλειτουργία βηματοδότη. Πως μπορούμε να την εκτιμήσουμε στο ιατρείο.» Koσσυβάκης Χάρης Καρδιολογικό Τμήμα Γ.Ν.Α. «Γ. ΓΕΝΝΗΜΑΤΑΣ

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3 Diagnostic tools History: symptoms, physical examination 12 leads ECG, ECG holter monitor

4 history Obtain as much information as possible regarding: the pulse generator, leads, programmed values indication for pacemaker implant, special programming features particular to that model or patient Ask : Use of electronic equipments oversensing of EMI Arm movements oversensing of myopotentials

5 Examination findings symptoms Physical examination Fatigue dyspnea chest pain syncope dizziness Pocket stimulation Diaphragmatic stimulation Bradycardia Tachycardia Hypotension palpitations extracardiac stimulation

6 Basics of pacing Five letter code Pacing modes

7 AV Intervals Initiated by a paced or non-refractory sensed atrial event Separately programmable AV intervals SAV /PAV Lower Rate Interval PAV 200 ms AP DDD 60 / 120 VP SAV 170 ms AS VP

8 Atrial Escape Interval (V-A Interval) The interval initiated by a paced or sensed ventricular event to the next atrial event Lower Rate Interval 200 ms AV Interval AP DDD 60 / 120 PAV 200 ms; V-A 800 ms VP 800 ms VA Interval AP VP

9 Refractory Periods VRP and PVARP are initiated by sensed or paced ventricular events The VRP is intended to prevent self-inhibition such as sensing of T-waves The PVARP is intended primarily to prevent sensing of retrograde P waves A-V Interval (Atrial Refractory) Ventricular Refractory Period (VRP) AP VP Post Ventricular Atrial Refractory Period (PVARP)

10 Blanking Periods First portion of the refractory period-sensing is disabled AP Atrial Blanking (Nonprogrammable) Post Atrial Ventricular Blanking AP VP Post Ventricular Atrial Blanking (PVAB) Ventricular Blanking (Nonprogrammable)

11 Control of atrial pacing efficacy Atrial pacing: relation pacing spike to p wave constant paced p wave frequently very flat

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13 Interpreting paced ECG Evaluation of capture Are spikes present? Do they capture?are properly timed? 1000 msec1000 msec 880 msec 1000 msec Evaluation of sensing Are native beats present?do they inhibit pacing?

14 Native rate higher? Magnet application

15 ECG Signs of Pacemaker Malfunction Failure to output Failure to capture Undersensing Inappropriate pacemaker rate

16 Failure to Output Etiology Oversensing: Unexpected sensing of an intracardiac or extracardiac signal. (myopotentials, electromagnetic interference,t waves, and P waves) Battery depletion Circuit failure (Lead fracture, disconnection of lead from the PM) Crosstalk (dual-chamber PM) monitor system failure

17 myopotentials Sensing of myopotentials led to symptomatic pauses No spikes present Record the surface ECG while the patient perform provocative maneuvres

18 electromagnetic interference electrical current leaks from electric motors, electronic surveillance systems,electrocautery equipment, MRI machines Sometimes necessary to record cardiac rhythm in the enviroment in which the reported symptoms occur( 24 ecg holter) Applying a magnet to the pacemaker can differentiate oversensing from other causes of the absence of spikes Pacing inhibition

19 Cross talk In a dual-chamber PM, the PM stimulus in one chamber is sensed in the other chamber PM stimulus For the PM-dependent patient, inhibition could result in ventricular asystole. Applying a magnet to the pacemaker asychronous pacing VOO

20 Bipolar pacing stimulus + isoelectric QRS

21 Failure to Capture Cause : Dislodgment of the PM lead from the endocardial surface (usually in the first few weeks) Break in the insulation of the PM catheter allows some of the current from the electrode to escape into the surrounding tissues. Impending battery depletion Poor lead position, exit block etc. Marked metabolic abnormalities, such as hyperkalemia, and some cardioactive drugs, such as flecainide. - Inappropriately low voltage-amplitude and pulse-duration settings A PM artifact occurring within the myocardial refractory period

22 Intermittent ventricular failure to capture in a patient with a dual-chamber pacemaker DDDR pacemaker. All but one ventricular pacing artifact fail to result in ventricular depolarization, that is, failure to capture

23 Functional non capture

24 QRS vector small or relatively isoelectric

25 Undersensing Failure to sense intermittent or total Etiology Inappropriately programmed sensitivity Lead dislodgment Lead failure: Insulation break, conductor fracture Lead maturation Change in the native signal Battery depletion

26 Intermittent undersensing of sinus beats in the atrium P-wave not sensed Atrial spike

27 undersensing of a ventricular extrasystole R-on-T phenomenon

28 Inappropriate Pacing Rates Tracking of atrial fibrillatory or flutter waves PMT Electromagnetic interference from the patient's environment may cause the generator to be reset to a rate different from that programmed. Many PMs operate at a slower rate when battery depletion is imminent.

29 Pacemaker mediated tachycardia 3 elements : A dual-chamber pacemaker Retrograde conduction Triggering event(pvc, loss of atrial capture) Magnet application: breaks the circuit The pacing rate is limited to the programmed upper rate limit

30 Specific Device Operation changing the rate Hysteresis Rate drop response Mode switching Rate responsive pacing

31 Hysteresis Extends the pacing interval looking for intrinsic cardiac activity Appropriate for patients whith an underlying rhythm similar of the programmed pacing lower rate Lower Rate 70 ppm Hysteresis Rate 50 ppm

32 Rate Drop Response Delivers pacing at high rate when episodic drop in rate occurs Pacing therapy indicated for patients with neurocardiogenic syncope

33 Mode Switching

34 Rate Responsive Pacing An accelerating or decelerating rate may be perceived as anomalous pacemaker behavior VVIR / 60 / 120

35 battery status evaluation the pacing rate on magnet application varies depending on the available battery life.

36 PPM ECG QRS Morphology

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38 RVOT Pacing Frontal plane axis: left inferior, it becomes right inferior as the site of stimulation moves superiorly towards the pulmonary valve

39 RBBB morphology in RV Pacing septal perforation septal sites activating the fibers of left bundle

40 ambulatory electrocardiography Indicated for the analysis of patients with pacemakers for the evaluation of frequent palpitations, syncope, or near syncope, to assess the device for myopotential inhibition and pacemaker mediated tachycardia to assist in the optimization of physiologic programming Journal of the American College of Cardiology, Vol. 38, No. 7, 2001

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42 conclusions ECG 12 leads remains the basic diagnostic tool regarding the pacemaker mulfunction for the general cardiologist Not always reveals signs of pacemaker dysfunction Patients with typical symptoms of pacemaker mulfunction should always have further investigation (device interrogation)