the purpose of this document is to provide a basic understanding , to internal medicine physicians and hospitalists , as to how the functionality of cardiovascular implantable electronic devices ( cieds ) may be affected during noncardiovascular surgery . in the united states , every year
, there are more than 100  000 implantable cardioverter defibrillators ( icds ) and 300  000 pacemakers implanted . due to this growing number , it is not uncommon that these patients will also undergo other types of surgeries during their lifetime . a good understanding on how these devices work will lead to safer noncardiac surgeries and diminish risk of adverse effects .
this review article is mostly based on expert consensus statement that was adapted by heart rhythm society and american society of anesthesiologists , but complex concepts were simplified or broken down .
this concise literature review provides internists and hospitalists with quick reference as to how to approach patients with cieds .
although it may seem to be overwhelming , during residency training there is little attention paid to this topic .
nevertheless , it is more common that patients with cied are being managed by general practitioners , including evaluating them prior to noncardiac surgery . knowing potential interactions between cied and electrosurgery and how to manage them will improve patients safety during surgeries .
it is important to understand basic functions and differences between pacemakers , icds , and cardiac resynchronization ( crt ) devices .
there is one more , relatively recent , group of icds  subcutaneous icd  that has no ability to pace the heart and only manage ventricular arrhythmias .
pacemakers can have either 2 ( atrial and ventricular ) or 1 ( mostly ventricular , but in europe atrial lead only may be implanted for patients with sick sinus syndrome ) lead . if a patient is in permanent atrial fibrillation , then only a ventricular lead is implanted .
the main function of pacemaker is to prevent the heart rate ( hr ) from falling below a certain limit ( mostly below 60  beats per minute [ bpm ] , but sometimes slower hr may be set ) .
however , icds are implanted for primary or secondary prevention of cardiac arrest , and their main function is to pace out ventricular arrhythmia or deliver icd shock .
all icds have the ability to pace the heart similar to pacemakers . however , unless the patient is pacemaker dependent , a lower rate of pacing for icds is set at or below 40  bpm .
for example , the absence of pacing spikes on an electrocardiogram ( ecg ) , at baseline hr of 50  bpm , does not necessarily mean an abnormal pacing function of icd .
there is one more group of cardiac devices called crt or sometimes referred to as biventricular device
. the crt device can be just a pacemaker ( crt - p ) or more commonly icd ( crt - d ) .
the purpose of this device , in addition to a pacemaker or icd , is also to synchronize contraction of the left ventricle to improve symptoms of congestive heart failure ( chf ) .
it is expected that these devices provide constant pacing of the heart as appears on ecg , despite the fact that these patients , most of the time , are not pacemaker dependent .
pacemaker dependence can be functional or absolute . if absolute pacemaker dependence is present , then without proper functioning of the device hr will not be stable enough to afford hemodynamic stability .
as mentioned above , crt devices are forced to pace to synchronize the ventricle , but if pacing function is inhibited , there is usually an underlying rhythm that is stable enough to avoid hemodynamic instability . but
another example of functional dependence is when without pacing , the hr will be less than set by lower rate pacing but will not lead to hemodynamic instability .
an example of this may be a patient with sinus node dysfunction who needs acceleration of hr in the atrium to satisfy metabolic demands during exertion . without proper pacemaker function , hr may be slow , but not slow enough to cause hemodynamic instability . during most surgeries ,
electrical current flows from stylus that is being used to cut or coagulate , through patient body , to a dispersion patch on the skin .
this electrical current , when interferes with cieds , will lead to different outcomes depending on the type of device implanted .
when emi affects pacemaker sensing circuits , it may lead to the inhibition of pacing function as pacemakers will not be able to differentiate emi from intrinsic heart activity . in absolute pacemaker - dependent patients
the icds react differently to emi as sensing circuits also have different functions to detect and treat ventricular arrhythmia .
in addition to inhibiting pacing function in patients who are pacemaker dependent , emi can also lead to inappropriate icd therapy ( deliver icd shock or antitachycardia pacing ) as the device may erroneously interpret emi as ventricular tachycardia ( vt ) or ventricular fibrillation ( vf ) ( figure 1 ) . for the crt devices ,
there are other potential issues that may occur to cieds , but they are very rare , ie , device reset , pulse generator damage , or lead tissue interference ( eg , increasing pacing threshold )
. if the electrosurgery current is at least 6  in away from cied , this risk can further decrease .
example of electromagnetic interference ( emi ) on cardiac resynchronization ( crt - d ) , with inappropriate implantable cardioverter defibrillator ( icd ) therapy .
high - frequency artifact is noted on atrial lead ( a ) as well as right ventricular lead ( rv ) in patient with crt - d device .
this leads to erroneous interpretation of emi in atrial lead as atrial fibrillation ( af ) and ventricular fibrillation ( vf ) in the right ventricular lead .
eventually , it leads to inappropriate icd shock ( 31  j  shk ) .
a magnet is one of the tools that can be used to eliminate emi for cieds if placed over it .
if one places a magnet over a pacemaker , it will make it pace asynchronously and the pacemaker will ignore any intrinsic sensing and emi .
it will prevent a pacemaker - dependent patient from becoming hemodynamically unstable as hr will be at a manufacturer - determined magnet rate ( table 1 ) .
placing a magnet over the icd will lead to inhibition of all of its therapies for vt or vf , but most importantly , the pacing function will not be affected .
for instance , if a patient with icd is also pacemaker dependent , placing a magnet over it will prevent inappropriate icd therapy due to emi , but the patient may become bradycardic and hemodynamically unstable , as the device will not pace asynchronously .
prior to most surgeries , patients are being referred to physicians for preoperative risk assessment . during this time
if the patient has cied , further questioning and investigation are needed to assure safety of the patient during surgery .
it is extremely important to determine what type of device the patient has : pacemaker , icd , crt - p , or crt - d .
this seemingly simple task can be sometimes challenging , especially if the patient can not provide or does not know this information ; for example , the patient is unconscious prior to surgery ( figure 2 ) .
all patients , after the initial implantation of cied , will be given an identification card with the description of their device .
if this card is not available , reviewing patient s chest x - ray ( cxr ) will help in differentiating the type of device and manufacturer , as well .
knowing the manufacturer can be useful as companies have different magnet response rates of pacing ( table 1 ) . if cxr does not yield conclusive information
, one may call the manufacturer , which will provide all necessary information and is available 24  hours , 7  days a week ( medtronic , 18005515544 ; boston scientific , 18002273422 ; st .
once the presence of the device and its type are established , it is also important to know the last time it was interrogated .
if the device was checked within 6  months of the planned procedure , and it was functioning normally , recommendation regarding management of cied can be given most of the time without reinterrogating it .
difference between pacemaker and implantable cardioverter defibrillator ( icd ) on chest x - ray : ( a ) dual - chamber pacemaker with leads in the atrium and right ventricle and ( b ) single - chamber icd with radiodense coil ( arrow ) in the right ventricle . to provide accurate recommendations regarding management of cieds during surgery
will electrosurgery be used during surgery , and what type ? if bipolar electrosurgery is used or no electrosurgery is used , then no adjustments to cieds are needed , assuming that the device functions properly based on routine device checks .
if the surgery is below the umbilicus , it is highly unlikely that emi will affect device function .
the position of the patient during surgery is important because if a magnet can not be safely secured over the cied , then reprogramming of device will be necessary .
there are pluses and minuses for both using a magnet and reprogramming periprocedurally ( table 2 ) .
the 12-lead ecg can reveal underlying rhythm and also give suggestion if a patient may be pacemaker dependent .
if one sees that every beat in the ventricle is being paced , it should be assumed that the patient is pacemaker dependent , especially in emergent cases .
abbreviations : cieds , cardiovascular implantable electronic devices ; icd , implantable cardioverter defibrillator ; vf , ventricular fibrillation .
obviously , in an emergent situation , there may be no time for the arrhythmia team ( most of the time led by electrophysiologist and supported by nurse practitioner or physician assistant ) to evaluate the patient , and therefore , the emergency protocol is followed , as seen in figure 3 .
for all emergent and nonemergent cases , it is important that the patient be monitored by electrocardiography and plethysmography or oximetry .
all patients should have defibrillator pads placed on them in an anterior - posterior fashion with the ability to pace transcutaneously , if needed .
the code cart must be readily available , as well as a magnet , in case it needs to be used . for all elective cases
communication between physicians caring for the patient plays a vital part in assuring an uneventful surgery .
utilization of manufacturer representative should not be considered as an option to provide recommendations prior to surgery , as these representatives are not clinicians and their knowledge is limited .
once the surgical and anesthesia teams receive the necessary recommendations , they will need to provide appropriate monitoring during surgery and be aware of possible changes in the device behavior .
every patient should be connected to an electrocardiography monitor and pulse plethysmography or oximetry . during surgery ,
when electrosurgery is being used , it may affect not only the cied but also the electrocardiography monitor .
having more than one lead to monitor ecg may help to distinguish artifact from real arrhythmia .
a magnet should be readily available in those cases , when it was not recommended prior to procedure , for the pacemaker patient because one had stable underlying , nonpaced , rhythm .
sometimes , during surgery , due to sedation , the hr may become slow and placing a magnet over the device will initiate an asynchronous pacing and prevent bradycardia . when a patient has an icd and
either magnet or reprogramming was used to deactivate its therapy , it is important to keep the patient on constant ecg monitor and have an external defibrillator readily available to deliver therapy , if needed .
defibrillator pads may need to be placed on the patient prior to procedure , as placing them during an emergency may compromise the sterile field ( anterior - posterior placement of pads is preferred , as well as a distance of at least 8  cm from cied ) .
alternatively , if vt or vf was detected on the monitor and a magnet was used to deactivate therapy , just removing it from icd would make it fully functional and defibrillation will be delivered , if needed .
for example , if the surgical site is on the left arm , the patch should be placed on the same arm , as opposed to placing it on the right arm and directing current , via tissue , that has cied .
furthermore , limiting the duration of a single application to less than 5  seconds , with a few second pauses in between deliveries , would significantly decrease adverse interferences .
for example , if the patient is pacemaker dependent , even if short electrosurgery applications would lead to oversensing by pacemaker and inhibit its output , it would unlikely cause hemodynamic compromise . in view of recently published expert
consensus statement for programming icds , to avoid unnecessary therapy , there is a delay between detection of tachycardia and therapy .
hence , if electrosurgery application will be limited to less than 5  seconds at a time , it will unlikely lead to icd therapy , as the device will declare this event as nonsustained . once the surgery is complete , the patient is usually transported to a holding or recovery area .
patients should remain in an electrocardiography monitor at least until the magnet is removed from the cied or reprogramming of the cied is performed and the original , preprocedure , settings are programmed .
once this is accomplished , the length of further monitoring is decided on by the primary team .
if reprogramming of the device was not done prior to procedure , most of the time it would be sufficient for the patient to be followed in the device clinic within a month . exceptions to this would be if abnormalities were noted on the monitor , it would suggest abnormal pacing or icd function , hemodynamic compromise during surgery , cardiac arrest , emergent surgery , or an appointment can not be arranged for the patient to visit device clinic within 1  month .
prior to most surgeries , patients are being referred to physicians for preoperative risk assessment . during this time
if the patient has cied , further questioning and investigation are needed to assure safety of the patient during surgery .
it is extremely important to determine what type of device the patient has : pacemaker , icd , crt - p , or crt - d .
this seemingly simple task can be sometimes challenging , especially if the patient can not provide or does not know this information ; for example , the patient is unconscious prior to surgery ( figure 2 ) .
all patients , after the initial implantation of cied , will be given an identification card with the description of their device .
if this card is not available , reviewing patient s chest x - ray ( cxr ) will help in differentiating the type of device and manufacturer , as well .
knowing the manufacturer can be useful as companies have different magnet response rates of pacing ( table 1 ) . if cxr does not yield conclusive information
, one may call the manufacturer , which will provide all necessary information and is available 24  hours , 7  days a week ( medtronic , 18005515544 ; boston scientific , 18002273422 ; st .
once the presence of the device and its type are established , it is also important to know the last time it was interrogated .
if the device was checked within 6  months of the planned procedure , and it was functioning normally , recommendation regarding management of cied can be given most of the time without reinterrogating it .
difference between pacemaker and implantable cardioverter defibrillator ( icd ) on chest x - ray : ( a ) dual - chamber pacemaker with leads in the atrium and right ventricle and ( b ) single - chamber icd with radiodense coil ( arrow ) in the right ventricle . to provide accurate recommendations regarding management of cieds during surgery
will electrosurgery be used during surgery , and what type ? if bipolar electrosurgery is used or no electrosurgery is used , then no adjustments to cieds are needed , assuming that the device functions properly based on routine device checks .
if the surgery is below the umbilicus , it is highly unlikely that emi will affect device function .
the position of the patient during surgery is important because if a magnet can not be safely secured over the cied , then reprogramming of device will be necessary .
there are pluses and minuses for both using a magnet and reprogramming periprocedurally ( table 2 ) .
the 12-lead ecg can reveal underlying rhythm and also give suggestion if a patient may be pacemaker dependent .
if one sees that every beat in the ventricle is being paced , it should be assumed that the patient is pacemaker dependent , especially in emergent cases .
abbreviations : cieds , cardiovascular implantable electronic devices ; icd , implantable cardioverter defibrillator ; vf , ventricular fibrillation .
obviously , in an emergent situation , there may be no time for the arrhythmia team ( most of the time led by electrophysiologist and supported by nurse practitioner or physician assistant ) to evaluate the patient , and therefore , the emergency protocol is followed , as seen in figure 3 .
for all emergent and nonemergent cases , it is important that the patient be monitored by electrocardiography and plethysmography or oximetry .
all patients should have defibrillator pads placed on them in an anterior - posterior fashion with the ability to pace transcutaneously , if needed .
the code cart must be readily available , as well as a magnet , in case it needs to be used .
for all elective cases , it is preferred that the arrhythmia team evaluate the patient and provide recommendations .
communication between physicians caring for the patient plays a vital part in assuring an uneventful surgery .
utilization of manufacturer representative should not be considered as an option to provide recommendations prior to surgery , as these representatives are not clinicians and their knowledge is limited .
once the surgical and anesthesia teams receive the necessary recommendations , they will need to provide appropriate monitoring during surgery and be aware of possible changes in the device behavior .
every patient should be connected to an electrocardiography monitor and pulse plethysmography or oximetry . during surgery ,
when electrosurgery is being used , it may affect not only the cied but also the electrocardiography monitor .
having more than one lead to monitor ecg may help to distinguish artifact from real arrhythmia . a magnet should be readily available in those cases , when it was not recommended prior to procedure , for the pacemaker patient because one had stable underlying , nonpaced , rhythm .
sometimes , during surgery , due to sedation , the hr may become slow and placing a magnet over the device will initiate an asynchronous pacing and prevent bradycardia . when a patient has an icd and
either magnet or reprogramming was used to deactivate its therapy , it is important to keep the patient on constant ecg monitor and have an external defibrillator readily available to deliver therapy , if needed .
defibrillator pads may need to be placed on the patient prior to procedure , as placing them during an emergency may compromise the sterile field ( anterior - posterior placement of pads is preferred , as well as a distance of at least 8  cm from cied ) .
alternatively , if vt or vf was detected on the monitor and a magnet was used to deactivate therapy , just removing it from icd would make it fully functional and defibrillation will be delivered , if needed .
for example , if the surgical site is on the left arm , the patch should be placed on the same arm , as opposed to placing it on the right arm and directing current , via tissue , that has cied .
furthermore , limiting the duration of a single application to less than 5  seconds , with a few second pauses in between deliveries , would significantly decrease adverse interferences .
for example , if the patient is pacemaker dependent , even if short electrosurgery applications would lead to oversensing by pacemaker and inhibit its output , it would unlikely cause hemodynamic compromise . in view of recently published expert consensus statement for programming icds , to avoid unnecessary therapy
hence , if electrosurgery application will be limited to less than 5  seconds at a time , it will unlikely lead to icd therapy , as the device will declare this event as nonsustained .
once the surgery is complete , the patient is usually transported to a holding or recovery area .
patients should remain in an electrocardiography monitor at least until the magnet is removed from the cied or reprogramming of the cied is performed and the original , preprocedure , settings are programmed .
once this is accomplished , the length of further monitoring is decided on by the primary team .
if reprogramming of the device was not done prior to procedure , most of the time it would be sufficient for the patient to be followed in the device clinic within a month . exceptions to this would be if abnormalities were noted on the monitor , it would suggest abnormal pacing or icd function , hemodynamic compromise during surgery , cardiac arrest , emergent surgery , or an appointment can not be arranged for the patient to visit device clinic within 1  month .
in conclusion , managing patients with cieds can be challenging , especially in emergent situations .
when time is of essence , following protocol from figure 3 may guide one during emergency noncardiac surgeries .
if surgical cases are nonemergent and medical facility has electrophysiology team , it makes more sense to involve them .
however , understanding concepts as described above affords better teamwork and collaboration . dividing evaluation into preprocedure , intraprocedure , and postprocedure steps
most of the evidence , as to interaction between cieds and electrosurgery , is based on case reports and information provided by engineers from device companies .
although it is not optimal or as strong as it used to be in other cardiology fields , it is the best available at this time .
nevertheless , extensive personal experiences in electrophysiology community lead to creating common sense recommendations that prepared patients with cieds to go safely through surgeries . as future technologies are knocking on our doors , we have to be ready to welcome them without compromising patient s safety .
as new technology develops and new devices are coming to the market ( eg , leadless pacemakers ) , more prospective and randomized studies are necessary to assure patients safety .
 in this article , the reader will get some insights into managing patient with implantable cardiac devices while undergoing noncardiac surgery . we will review basic concepts regarding normal function of pacemakers and implantable cardioverter defibrillators , understanding how their function will be influenced during noncardiac surgeries . 
 you will be guided through management steps from preoperative , intraoperative , and postoperative aspects . in an ever - changing world of medicine 
 , it is important to keep up with progress as more and more patients get implantable cardiac devices . 
Introduction
Basic Concepts
Preoperative evaluation
Intraoperative management
Postoperative management
Conclusions