Fundamentals of Cardiac Rhythm Management Devices Ayman M. Kamaly, MD Professor of Anesthesiology kamaly3@hotmail.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. Few areas in clinical medicine have been more affected by advances in engineering technology than cardiac pacing 1958 :(just 4 years after the invention of the transistor). There has been a significant change not only in pulse generators and leads but also in the indications for pacing, pacing modalities, implantation techniques and follow-up of patients with implanted pacing devices.

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. Unfortunately, there are no reliable epidemiological data available about Egyptian population as regard CRMD implantation. However, USA data reveals that more than 250,000 adults & children are undergoing CRMD implantation each year. Aging of population, along with continued advances in CRMD technology, which lead to expanding indications for pacing and implantation, will lead to growing numbers of patients with CRMD.

This will increase the chances to be confronted with patients having CRMD (not uncommon). 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”. All of this places an ever-growing burden upon the anesthesiologist to properly manage these technologies during the perioperative period, a period that still involves pacemaker-related morbidity and mortality

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. Recently, dual and three –chamber pacing (right atrium, both ventricles) has been used to treat: (HOCM), (DCM), and long Q-T syndrome. These relatively new indications require careful attention to pacer programming, since effective pacing in these patients requires a greater rate than native sinus rate and shorter AV delay than the native P-R interval so that the ventricle is paced 100% of the time. Pacemaker inhibition, loss of pacing (i.e., from native conduction, atrial arrhythmia, or electromagnetic interference) can leads to deteriorating hemodynamics in these patients.

Cardiac Rhythm Management Devices (CRMD) basic components Impulse generator (1/2 life 5-10 yrs) Lead: Unipolar, Bipolar, Multiplolar. Mercury–Zinc batteries were used in the past had a short useful life (2-3 yrs). Currently Lithium-iodine batteries are being used (5-10 yrs) and high energy density. The body is about 4 Cm long, the electrode between 50 -60 Cm . Unipolar: generator case serves as an electrode. larger “spike” on ECG & more sensitive to EMI. Bipolar: “pacing/sensing configuration”, as pacing requires less energy and sensing is more resistant to EMI. Mulipolar: connection to multiple chambers

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” change the paced rate in proportion to the metabolic demand and physical activity

Rate Modulation Sensors Available Under Investigation Body activity (vibration) QT interval Respiratory rate Mixed venous oxygen saturation Minute ventilation Atrial rate Right ventricular stroke volume Blood PH Right atrial pressure Evoked pressure Systolic time intervals Paced depolarization integral Blood temperature ALL of which can be affected by the anesthesiologist management Currently, the sensors of motion or minute ventilation (MV) are the most widely used. if rate modulation CRMD using MV  may induce tachycardia if pt hyperventilated (e.g., in neurosurgery)

Generic Pacemaker Code (NASPE/ BPEG, Revised 2002) Position I: Paced Chamber(s) Position II: Sensed Chamber(s) Position III: Response(s) to Sensing Position IV: Programm-ability Position V: Multisite Pacing * O = None A = Atrium I = Inhibited R = Rate Modulation V = Ventricle T = Triggered D = Dual (A + V) (T + I) 1970: 3 letter ID Code 1980: extended to 5 letter ID Code 1987: NASPE & BPEG adopted a new 5 letter ID Code * = When 2 atria or 2 ventricles are paced. NASPE: North American Society of Pacing & Electrophysiology, BPEG: British Pacing & Electrophysiology Group.

Asynchronous: (AOO, VOO, & DOO) 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 Effect Drugs Other Factors Increase Threshold Flecainide, Propafenone, Encainide, Sotalol, -Blockers*, Lidocaine*, Verapamile*, Quinidine*, Procainamide*. Myocardial ischemia/infarction Hyperkalaemia Severe Acidosis or Alkalosis Hypothyrodism* Hyperglycemia* Possibly Decrease Threshold Atropine, Catecholamines, Glucocorticoids. Pheochromocytoma Hyperthyroid Hypermetabolic states No Proven Effect Amiodarone, Anesthetic drugs (both; inhalational & intravenous) * 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 The response varies with the model and the manufacturer and may be in the form of no change in rate or rhythm, brief asynchronous pacing, continuous or transient loss of pacing. The indirect sources of EMI include radar, orthopaedic saw, telemetric devices, mechanical ventilators, lithotriptors, cellular telephones, and whole body vibrations Fatal arrhythmias and deaths have been reported with the use of electrocautery leading to pacemaker failure.

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 !!

How to Deal with a Patient with CRMD

Stepwise Approach Patient with a CRMD: Preoperative Evaluation: 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+) these patients suffers from CAD (50%), HtN (20%) & DM (10%), one should know: (1) severity, (2) current functional status, (3) medication. ECG CXR (for visualization of continuity of leads) serum electrolytes (especially K+).

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). Q: How you know if A, V, or sequential pacing?! A: spike: A  before P wave (+ normal QRS), V  spike immediately followed by widened QRS, AV Sequential  2 spikes before P & QRS

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 !! Get the device interrogated (consultation with a cardiologist or manufacturer agent) and obtain a copy of this interrogation. Ensure that the pacing impulses create a paced beat (i.e., produce a mechanical systole with a pacemaker impulse).

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). Consider replacing any device near its elective replacement period in a patient undergoing elective major surgery.

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). ECG (preferably with respiratory rate monitoring)

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 ??! Choice of agents should be dictated by patient’s underlying physiology and procedure. However, the use of agents that suppress the AV or SA node (as potent opiates or dexmedetomidine) can abolish any underlying rhythm and render patient truly pacemaker dependant. Succinylcholine fasciculation, myoclonic movements, or direct muscle stimulation can inappropriately inhibit or trigger stimulation, (according to programmed pacing modes). Etomidate and ketamine should be avoided as these cause myoclonic movements. N2O: Expansion of the gas in the pocket  loss of contact (specially in newly implanted CRMD; still air)

Intraoperative Management (Cont.) EMI–Induced CRMD Potential Dysfunction Electrocautery: Avoid Unipolar (χ χ). Use Bipolar or ultrasonic (harmonic) (√√) If unipolar used: Grounding plate: as far as possible from the pacemaker site, Assure that the current does not pass 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. Distance: not < 15 cm, not only because of interference with battery circuit, but also because if cautery came in contact with a break in the insulation of the electrode, it may cauterize the myocardium at the electrode tip.

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 affect pacemaker function MRI: Contraindicated Generally If MRI must be performed, consult with the ordering physician, the patient’s cardiologist, the diagnostic radiologist, and manufacturer. When MRI is absolutely essential (reprogram to OOO mode) provided that pt has underlying rhythm !!! + external pacemaker ready. MRI may be safe( at least with some models) as long as generator & leads are outside the magnet bore

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. A clinically appropriate energy output should always be used regardless of the presence of a CRMD, and the paddles should be positioned as best as can be done in an emergency.

Postoperative Management 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 Thanks for your Attention !!