Fundamentals of Cardiac Rhythm Management Devices Ayman M. Kamaly, MD Professor of Anesthesiology email@example.com
Anesthesiologists Do it … while you sleep !!
Overview: 1958: 1st Battery operated pacing devices. 1980: Implantable Cardioverter- defibrillator (ICDs). Today: > 2000 pacemaker models, produced by 26 companies.
Epidemiology: • No reliable Egyptian data. • USA data: > 250,000 adults & children are undergoing Cardiac Rhythm Management Device (CRMD) implantation annually. • Aging, advances in CRMD technology & expanding indications for pacing, will lead to growing numbers of patients with CRMD.
This will increase the chances to be confronted with patients having CRMD (notuncommon). • Those patients often have significant comorbid diseases and need procedures of varying complexities. • “Our ability to care for these patients requires attention to their primary medical problems, as well as understanding these devices”.
Permanent Pacemaker Indications: • Symptomatic Sinus Bradycardia. • S A Node Disease. • Symptomatic A V Node Disease. • Hypertrophic Obstructive Cardiomyopathy (HOCM). • Dilated Cardiomyopathy (DCM). • Long Q T Syndrome. Bryce et al, Ann Intern Med. 2001; 134:1130-41.
Cardiac Rhythm Management Devices (CRMD) basic components • Impulse generator (1/2 life 5-10 yrs) • Lead: • Unipolar, • Bipolar, • Multiplolar.
How CRMD Works?! • Basic: Track the native electrical rhythm. When doesn't sense a heart beat within a ‘normal beat-to-beat time’, it stimulates the ventricle. • More complex: Sense &/or stimulate both; atrium and ventricle. • Much More Complex: “Rate Modulation”
Generic Pacemaker Code (NASPE/ BPEG, Revised 2002) • * = When 2 atria or 2 ventricles are paced. • NASPE:North American Society of Pacing & Electrophysiology, • BPEG:British Pacing & Electrophysiology Group.
Examples and Types of Pacing Modes: Asynchronous: (AOO, VOO, & DOO) • Fixed (preset rate) rate pacemaker. • Discharges irrespective of the native heart rate. • Hazard: Competes with the native intrinsic rhythm → arrhythmias induction.
Single Chamber Atrial Pacing (AAI, AAT) • Atrium is paced and the impulse passes down the conducting pathways, thus maintaining A-V synchrony. • A single lead in the Rt. Atr., which senses the intrinsic P wave and causes inhibition or triggering of the pacemaker. • Useful in sinus arrest & sinus bradycardia (adequate AV-conduction) • Inappropriate for chronic AF & long ventricular pauses.
Single Chamber Ventricular Pacing (VVI, VVT) • VVI: The most widely used pacing mode. • ventricle is sensed & paced. • It senses the intrinsic ‘R’ wave and thus inhibits the pacemaker function. • Indications: Complete HB with chronic AF, Af, & long ventricular pauses.
Dual Chamber AV Sequential Pacing (DDD, DVI, DDI, and VDD) • Using 2 leads (Rt. Atr. & Rt. vent.) • 1st: atrium is stimulated to contract, • After an adjustable PR interval, ventricle is stimulated (preserve normal AV contraction sequence), • indications: AV block, SA node disease. • In DDD system, both the atrium and ventricle can be sensed and paced. • Advantages: mimic SR, so beneficial when atrial contraction is important for ventricular filling (e.g. A.S.)
Factors Influencing CRMD Pacing Threshold * Possibly Atlee, 1999
Effect of the Magnet Application on Pacemaker Function. • Magnet-activated switches were incorporated into pacemakers to produce pacing behavior that demonstrates remaining battery life. • Never intended to treat pacemaker emergencies or prevent EMI effects
Thus, magnets can be used to protect the pacemaker-dependent patient during EMI, (diathermy/cautery). • Magnet application results in a non-sensing asynchronous mode with a fixed pacing rate (magnet rate). • Use of magnet during surgery is not without risk. Asynchronous pacing may trigger malignant rhythm.
Not All Pacemakers Switches to a Continuous Asynchronous Mode When a Magnet is Applied. • In programmable pacemakers, in the presence of EMI, generator may unpredictably reprogrammed with a new ‘surprise programme’. • Most current devices should be considered programmable unless known otherwise.
Anesthesiologists You Sleep .. We Care !!
Stepwise Approach Patient with a CRMD: • Routine preoperative evaluation: • CAD (50%) HTN (20%) & DM (10%), Assess: (1) severity, (2) current functional, status (3) medication. • CXR, (continuity of leads) • ECG, (Spike) • Bioch (s. K+) • Preoperative Evaluation:
Preoperative Evaluation (Cont.): • Confirm whether a patient has a CRMD: • Focused history: interview, medical records, CXR, ECG. • Inquire about the initial indication for the pacemaker & pre-implantation symptoms (dizziness, fainting). • Focused physical examination (check for scars, palpate for device).
Preoperative Evaluation (Cont.): • Define the type of CRMD. • Obtain manufacturer’s ‘ID card’ from patient. • If no other data is available: CXR (X-Ray code). • Determine patient dependency on CRMD pacing. • No spontaneous ventricular activity when programmed to VVI mode at the lowest programmable rate.
Preoperative Evaluation (Cont.): • Evaluation of CRMD function. • Get the device INTERROGATED(by Cardiologist) & get a copy !!
Preoperative Evaluation (Cont.): • Evaluation of CRMD function (Cont.) • Ensure that the electrical pacing impulse creates a mechanical systole (preph. pulse) !! • If VVI mode: if intrinsic HR is > set rate, slow down HR (carotid massage or Valsalva manoeuvre), while ECG is monitored.
Preoperative Preparation • If Intraop. EMI is likely to occur : • Reprogram to Asynchronous mode. • Deactivate all ‘Rate Responsive’ !! • ‘Activity’ rate responsive: shivering and fasciculations • ‘Minute ventilation’ rate responsive: (RR & Vt) should be kept controlled • ‘Temperature’ rate responsive Temp kept constant. • Disable Antitachyarrhythmia functions if present (if CRMD is ICD). • Temporary pacing and defibrillation equipment should be immediately available (all CRMD).
Preoperative Preparation (Cont.) • Evaluate the possible effects of anesthetic techniques on CRMD function. • CXR to document the position of the Coronary Sinus lead, if CVL placement is planned, (CS lead displacement).
Intraoperative Management • Monitor CRMD operation. • ECG: • Ability to detect pacemaker discharge (disable “artifact filter”). • Preferably with Respiratory Rate monitoring. • Monitor peripheral pulse: • Manual palpation, • Waveform Display: pulse oximeter, A. line).
Intraoperative Management (Cont.) • Anesthetic Technique: • Should be dictated by patient’s underlying physiology &/or procedure. • Agents suppresses AV or SA node (potent opiates or dexmedetomidine) may render patient ‘truly pacemaker dependant’. • Myoclonic movements, can inhibit or trigger stimulation, (according to programmed pacing modes): • Succ. Ch.: fasciculation, • Etomidate & ketamine: myoclonic movements. • Nitrous Oxide ??!
Intraoperative Management (Cont.) • EMI–Induced CRMD Potential Dysfunction • Electrocautery: AvoidUnipolar (χχ). UseBipolarorultrasonic(harmonic) (√√) • If unipolar used: • Grounding plate: as far as possible from the pacemaker site, • Assure that the current does notpass through or near the CRMD • Distance:Not within 15 cm of pacemaker. • Frequency: 1-second every 10 seconds (to prevent repeated asystolic periods). • Pure “cut” is better than “Coag”. • Asynchronous Mode (magnet or programmer). • Emergency Tools: Temporary pacing (transvenous, trans -cutaneous), Atropine, Isupril should be ready.
Intraoperative Management (Cont.) • EMI–Induced CRMD Potential Dysfunction (Cont.) • Nature of Procedure: • Lithotripsy (ESWL): • Avoid beam focusing near the generator. • If triggers on the ‘R-wave’, disable atrial pacing. • Radiology: • Plain X-ray & CT: Do Not affectpacemaker function • MRI: ContraindicatedGenerally
Intraoperative Management (Cont.) • EMI–Induced CRMD Potential Dysfunction (Cont.) • Nature of Procedure (Cont.): • Radio-therapy: • Safe (Surgically relocate CRMD outside radiation field • ECT: • ECT itself safe (little current flows within the heart) • Succinylcholine and seizure (!!!) • Reprogram to asynchronous mode. • External pacemaker should be available.
Emergency Defibrillation or Cardioversion. • Follow existing ACLS guidelines (energy level & paddle placement). • Minimize the current flow through the generator & lead system by positioning the paddles : • As far as possible from the pulse generator, • Perpendicular to the major axis of the generator and leads to the extent possible by placing them in an ‘anterior–posterior’ location.
PostoperativeManagement • ICU Setup (Continuous ECG monitor, backup pacing & defibrillation). • Assure that all CRMD settings are restored: • Interrogate CRMD; (cardiologist/manufacturer)
Thanks for your Attention !! Oh .. Thank God … He’s Done