Pacemakers and Automatic Implantable Cardioverter-Defibrillator Devices

From the California Society of Anesthesiologists’ Annual Meeting and Clinical Anesthesia Update

Richard L. Applegate II, MD, Professor of Anesthesiology, Loma Linda University School of Medicine,Loma Linda, CA

Educational Objectives

The goal of this program is to improve anesthesia management of patients with pacemakers and implantable cardioverter-defi­brillator devices (ICDs). After hearing and assimilating this program, the clinician will be better able to:

1.   Identify the indications for ICDs.

2.   Explain the significance of pacemaker codes.

3.   Recognize and discuss the mechanisms that cause pacemaker syndrome.

4.   List the benefits of cardiac resynchronization therapy.

5.   Plan appropriate perioperative management of patients with ICDs.

Faculty Disclosure

In adherence to ACCME Standards for Commercial Support, Audio-Digest requires all faculty and members of the plan­ning committee to disclose relevant financial relationships within the past 12 months that might create any personal con­flicts of interest. Any identified conflicts were resolved to ensure that this educational activity promotes quality in health care and not a proprietary business or commercial interest. For this program, the faculty and planning committee reported nothing to disclose.

Acknowledgments

Dr. Applegate spoke at Annual Meeting and Clinical Anesthesia Update, held May 15-17, 2009, in Monterey, CA, and sponsored by the California Society of Anesthesiologists. The Audio-Digest Foundation thanks Dr. Applegate and the Cali­fornia Society of Anesthesiologists for their cooperation in the production of this program.

Introduction: wide range of devices available; have become complex (simple right ventricular single-chamber pace­makers now uncommon); 70,000 to 75,000 implantable cardioverter-defibrillators (ICDs) and 175,000 to 180,000 pacemakers implanted annually; use growing as indications broadening; »750,000 Americans die of heart disease annually (two-thirds from sudden cardiac death; 80% to 90% estimated to be associated with ventricular fibrillation [VF]); congestive heart failure (CHF) major cause of hospitalization and health care expenditures

Classes of evidence established by United States Preventive Services Task Force: class I  —  evidence from >1 pro­spective randomized controlled clinical trials; suggests benefits of procedure greatly outweigh risks; class II-A: at least fair evidence suggests benefits outweigh risks; class II-B: worth consideration; class III: comes from opinions of respected authorities, based on clinical experience (no randomized controlled trials available)

Indications for pacemaker: symptomatic sinus node dysfunction (based on class I, level A evidence; if seen in patient without pacemaker who presents for elective procedure, consider delaying surgery); known sinus dys-function, including periodic loss of consciousness, but ambulatory electrocardiography (ECG) not yet obtained; acquired atrioventricular (AV) block, especially with CHF; acute myocardial infarction (MI) with bundle branch block (may lead to life-threatening rhythms); hypersensitive carotid sinus syndrome; significant bradycardia

Cardiac resynchronization therapy (CRT): guidelines evolving; devices provide secondary prevention for patients with history of cardiac arrest due to VF, or destabilizing ventricular tachycardia; indicated for patients with CHF and ejection fraction <35% with history of cardiac arrest

New York Heart Association functional classification of heart failure: class I  —  patient has cardiac disease but no functional limitations; no objective evidence of serious heart disease; prognosis still poor; class II  —  symptoms such as dyspnea with ordinary exertion; objective evidence of disease still absent, except with exercise; class III  —dyspnea even with minimal activity; objective evidence of disease present; class IV  —  symptomatic at rest; transplantation recommended; terminal disease; CRT devices indicated for classes III and IV

Five-year survival without ICD: 50% for patients with class III or IV disease; 5-yr mortality 25% to 30% with ICD, but perioperative mortality still high

Managing CHF: CRT indications from American College of Cardiology Foundation/American Heart Association 2009 guidelines include primary prevention of sudden cardiac death (patient should be >40 days post-MI); low ejection fraction; class II or III symptoms while on optimal therapy; life expectancy >1 yr; class III or IV symp­toms with long QRS interval; implications for anesthesiologists  —  many surgical patients have CRT devices im­planted, then return for other procedures; to ensure optimal perioperative management, need to know why patient has device and issue it addresses

Cardiac pacemaker codes: chamber paced and chamber sensed  —  A (atrium), V (ventricle), or D (dual [both]); re­sponse to sensing  —  0 (none), T (triggered), I (inhibited), or D (dual [triggered and inhibited]); rate modulation  —0 (none) or R (rate responsiveness); often used in younger patients who develop symptoms when ex­ercising; multisite pacing  —  can pace one or both atria, one or both ventricles, or all 4; coded 0, A, V, or D

Simplified defibrillator codes: S (shock capability only), B (bradycardia pacing and shock capabilities), or T (tachycardia and bradycardia pacing and shock capabilities)

Complications of pacemaker therapy: short-term  —  arterial puncture; hemothorax; pneumothorax; infection; hem­orrhage; cardiac tamponade; death; long-term  —  device failure; perforations; infections; lead fracture

Indications: hemodynamic instability; prolonged ventricular tachycardia (watch for during preoperative evalua­tion); resynchronization

Importance of synchrony: according to 2006 meta-analysis, ICD improves survival, but patients not necessarily functionally improved due to dyssynchronous heartbeats associated with pacing; timing in ventricles with pacing not consistent; normal AV interval allows for maximum filling and optimal preload and stroke volume, resulting in improved cardiac output; pacemaker syndrome  —  low stroke volume resulting from atrial contraction against closed AV valve (when mitral and tricuspid valves open, blood flows backwards, with no preload to fill ventricle on next beat); suboptimal AV synchrony may result in syncope

Dilated cardiomyopathy: in response to dyssynchrony, heart may adopt circular shape, which results in incomplete emptying and uncoordinated contraction; if ventricle contracts with mitral valve open, blood may flow back into atrium, leading to diastolic mitral valve regurgitation; may occur even during electrical diastole; over time, heart stretches; left ventricular muscle mass thickens and enlarges, and geometry becomes increasingly unfavorable; if right ventricular pacer triggers, wave of electricity travels across septum and over lateral wall (with some por­tions of heart contracting against insufficient pressure, others against tight wall); cardiac dynamics shift to higher left ventricular volume and end-diastolic pressure, and maximum force becomes lower than normal due to in­creased residual volume

Mechanism of benefit: leads placed in right and left ventricles (3 leads total); allows coordination of timing of con­tractions; when measuring pressure curve with each beat using high-fidelity pressure transducer, more abrupt up­stroke (improved force of contraction) and larger area under curve (improved ejection fraction) observed; dP/dt curve improves (ie, shift to better Starling curve); results in better stroke volume and fewer CHF symptoms; resyn­chronization improves ejection without volume overload

Indications: low ejection fraction, prolonged QRS interval, and class III or IV symptoms despite medical therapy; patients with low ejection fraction, prolonged QRS interval and class I or II symptoms who receive ICD may also benefit from resynchronization at time of implantation; benefits include fewer symptoms, improved survival, possi­ble left ventricular remodeling, and fewer hospitalizations for CHF symptoms

Study data: meta-analysis  —  looked at frequency of major events; fewer hospitalizations for CHF after resynchroni­zation; clear benefit in mortality rates; European study  —545 patients followed for 3.5 yr after receiving CRT; many exhibited morphologic response; 41% remained stable; 20% did not respond; 111 of 545 patients listed for transplant (»50 before and 60 after CRT); 35 patients removed from list (20 before and 15 after CRT); left ven­tricular and end-diastolic diameter improved in patients who responded to CRT; functional improvement greater in early responders than in nonresponders; responders had significantly fewer major cardiac events; speaker rec­ommends consideration of CRT for patients awaiting transplantation (may allow removal from list); CRT vs med­ical therapy  —  CRT associated with greater functional improvement and survival in recent study of 400 patients; conclusions  —  CRT improves function, quality of life, and survival; reasonable option for patients with low ejec­tion fraction, dyssynchronous contractions, and significant class III and IV heart failure; 20% to 30% of patients do not respond; echocardiography may identify responders (currently under investigation); benefits persist (even increase) over time

Impact on perioperative risk: hypothetical case  —  patient has dilated cardiomyopathy; no history of myocardial infarction; had sustained ventricular tachycardia with no loss of consciousness; had class IV heart failure be­fore therapy; with medical therapy and CRT, now down to class II or III; probably falls into PS 3 or PS 4 cate­gory in American Society of Anesthesiologists (ASA) physical classification system; age, emergent status, and ASA physical classification best predictors of 30-day mortality

Perioperative Management of Cardiac Rhythm Devices

General principles: approach patients as though they have compensated CHF; anesthesia and surgery have potential to cause device to fail, become damaged, or malfunction

Electromagnetic interference (EMI): devices designed to detect changes in electric current; have long wires; func­tion as antennae; function may be disrupted by procedures such as electrocautery, shock wave lithotripsy, electro­convulsive therapy, or radiofrequency ablation; problems less likely if device has bipolar leads; magnetic current (eg, magnetic resonance imaging [MRI])  —  may interfere with electric current or put device in standby mode; physiologic effects include hypotension, pacemaker syndrome (patient may experience decreased cardiac output due to induced asynchrony), and dysrhythmias

Preventing perioperative problems: often occur due to lack of familiarity with device; ASA practice advisory  —recommends preoperative determination of type of device, potential impact of procedure on device, how to limit risk, and intraoperative and postoperative remedies for problems

Speaker’s recommendations: patients should carry card (leave card with significant other during surgery) that shows manufacturer; x-rays may shed light on nature of device (pacemaker or defibrillator); ask about indica­tions for device (eg, dyssynchrony, drop attacks), and whether patient has had AV node ablation; determine that device works; if necessary, delay surgery until interrogation of device conducted; procedures with low risk for EMI  —possibly best to “do nothing”; procedures with high risk for EMI  —  in patient with pacemaker, reprogram to asynchrony; monitor closely for pacemaker syndrome; in patient with ICD, disable shocking capability (make both adjustments in pacemaker-dependent patient); intraoperative measures  —  watch for discordant electrocardi­ography and pulse monitor readings (may signal problem)

Electrocautery: minimize damage by placing grounding pads across wound and away from leads (eg, place at hips or buttocks instead of under shoulder during knee surgery to minimize current reaching device); short bursts of cautery preferred (pacemaker pauses rather than shutting off); if procedure extensive, suggest bipolar cautery or ultrasonic scalpel

Other procedures of concern: use of radiofrequency catheters  —  avoid contacting leads; lithotripsy  —  focus away from device; newer technology has lower risk for pacing interactions; radiation therapy  —  effect on pacing de­vices unclear due to practice of limiting their exposure; damage to electronics and leads anticipated with expo­sure over time; MRI  —  recent study reported no significant adverse effects with exposure to 3-tesla magnetic field; still considered contraindicated in patients with implanted device at speaker’s institution; electroconvulsive therapy  —  impact on device remains unclear; monitor patients carefully; make sure device interrogated and re­programmed before discharging patient

Emergency defibrillation: if magnet has been placed to deactivate defibrillation, remove magnet (device should sense that shocking required); if device deactivated via programming with “magic black box”, need to reprogram or use external pads; precautionary placement of pacing pads on chest (in anteroposterior orientation, if possible) recommended in such cases; postoperative care  —  monitor patient until device reprogrammed

Reprogramming: magnet applied over pacemaker causes reversion to preprogrammed mode (best option when no other available; unlikely to harm patient); in most dual pacers, magnet changes settings to D-0-0 (ie, dual-paced, not sensing, not inhibited; AV synchrony preserved); in most cardioversion devices, magnet disables tachyar­rhythmic (shock) but not pacing function; should revert to preprogrammed rhythm when magnet removed (some exceptions); may be advisable to have device reprogrammed with black box

Conclusions: ideally, all patients should undergo preoperative evaluation by specialist; device should be interrogated and function and programming checked; inadvisable to wait until surgery to determine whether device functional; in emergencies, apply magnet to deactivate; in procedures with low risk for EMI, may be safe to proceed without using magnet (have available in case need arises); reprogram postoperatively

Suggested Reading

American Society of Anesthesiologists Task Force on Perioperative Management of Patients with Cardiac Rhythm Management Devices: Practice advisory for the preoperative management of patients with cardiac rhythm management de­vices: pacemakers and implantable cardioverter-defibrillators: a report by the American Society of Anesthesiologists Task Force on Perioperative Management of Patients with Cardiac Rhythm Management Devices. Anesthesiology 103:186, 2005; Cleland JG et al: The effect of cardiac resynchronization on morbidity and mortality in heart faiure. N Engl J Med 352:1539, 2005; Goldberger Z, Lampert R: Implantable cardioverter-defibrillators: expanding indications and technolo­gies. JAMA 295:809, 2006; Hansky B et al: Cardiac resynchronization therapy: long-term alternative to cardiac transplan­tation? Ann Thorac Surg 87:432, 2009; Jessup M et al: 2009 Focused Update: ACC/AHA Guidelines for the Diagnosis and Management of Heart Failure in Adults: A Report of the American College of Cardiology Foundation/American Heart As­sociation Task Force on Practice Guidelines: Developed in Collaboration With the International Society for Heart and Lung Transplantation. Circulation 119:1977, 2009; Lindner O et al: Effect of cardiac resynchronization therapy on global and regional oxygen consumption and myocardial blood flow in patients with non-ischaemic and ischaemic cardiomyopathy. Eur Heart J 26:70, 2005; Rozner MA: Preoperative evaluations: the very last chance to identify a problem with a pace­maker or implanted cardioverter-defibrillator. J Cardiothorac Vasc Anesth 22:341, 2008; Rozner MA: The patient with a cardiac pacemaker or implanted defibrillator and management during anaesthesia. Curr Opin Anaesthesiol 20:261, 2007; Stone ME, Apinis A: Current perioperative management of the patient with a cardiac rhythm management device. Semin Cardiothorac Vasc Anesth 13:31, 2009; Zipes DP et al: ACC/AHA/ESC 2006 guidelines for management of patient with ventricular arrhythmias and the prevention of sudden cardiac death: a report of the American College of Cardiology/Ameri­can Heart Association Task Force and the European Society of Cardiology Committee for Practice Guidelines (Writing Committee to Develop Guidelines for Management of Patients with Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death). J Am Coll Cardiol 48:e247, 2006.