Perioperative Management of the Patient with an Implantable Cardioverter Defibrillator

1st letter

2nd letter

3rd letter

4th letter

Shock chamber

Antitachycardia

pacing chamber

Tachycardia detection

Antibradycardia acing pacing chamber

O: none

A: atrium

V: ventricle

D: dual (A + V)

O: none

A: atrium

V: ventricle

D: dual (A + V)

E: electrocardiogram

H: hemodynamic

O: none

A: atrium

V: ventricle

D: dual (A + V)

When venous access is difficult, subcutaneous defibrillator may be helpful [2]. An electrode system is placed entirely subcutaneously, outside the thoracic cavity. A distal electrode on the defibrillator lead is associated to a proximal electrode located 8 cm from the tip of the lead. A coil is located between the tip and proximal electrode for defibrillation. The distal part of the lead is located at the left parasternal edge, and the device is placed over the fifth intercostal space between the left anterior and mid-axillary line. The device is capable of defibrillating with an output of 80 J [2]. Limits of this device are patients who require bradycardia pacing >30 s, antitachycardia pacing, or patients needing cardiac resynchronization therapy [2].

6.2 Intraoperative Dysfunction

The most frequent source of ICD dysfunction in the intraoperative period is electromagnetic interference (EMI) stemming from electric devices such as monopolar electrocautery or electric shaving occurring in proximity to the ICD generator. Radiofrequency waves between 0 and 10⁹ Hz can generate EMI and thus cause ICD or pacemaker malfunction. Figure 6.1 summarizes the most frequent sources of EMI encountered during the intraoperative period. In contrast, X-rays, infrared, or ultraviolet does not interfere with ICD..; In the specific case of radiotherapy, repeated exposures can damage the electric circuits in the generator but do not produce EMI of itself [5]. Thus, despite progress for enhancing protection against EMI risk, ICD remains still highly sensitive to interference in the intraoperative period. The manufacturers now incorporate filters and circuit shields that insulate the internal components. Moreover, for pacemakers, a shift toward bipolar leads (since 2000), which minimize the physical distance of the circuit with the anode and cathode incorporated in the lead tip, reduces the potential for EMI.

Fig. 6.1

ICD associated with a dual-chamber pacemaker

In contrast, the EMI risk is still high in ICD as the anode (lead tip) and cathode (generator) remain inevitably separated. During the intraoperative period, EMI can lead to the activation of the anti-tachyarrhythmia function and/or to delivery of an inappropriate electric shock. Total or partial inhibition of the pacemaker may occur, leading to cardiac arrest if the patient is pacemaker dependent (Table 6.2).

Table 6.2

Most frequent sources of EMI with ICD during the intraoperative period

Sources of EMI with ICD during intraoperative period
• Electrocautery (monopolar > > bipolar)
• Nerve stimulators
• Evoked potential monitors
• Fasciculations (succinylcholine)
• Electric shaving
• High tidal volumes
• Radiofrequency ablation
• Magnetic resonance imaging
• External defibrillation
• Lithotripsy
• Electroconvulsive therapy

6.3 Indications and Benefits of ICD

The ICD has proven its efficiency in preventing sudden death: both in primary prevention, as in the case of sudden death post-myocardial infarction or consecutive to a nonischemic dilated cardiomyopathy, and in secondary prevention, for patients having already presented episodes of malignant arrhythmias [2–5].

6.3.1 Primary Prevention of Sudden Cardiac Death

In 2006 [4], update in 2015 [2], guidelines for the indications of ICD implantation were update from 2006, in the light of the publication of two large studies MADITII [9] and DINAMIT [10] in addition to one meta-analysis [11] considering all the ten studies published in the domain: MADIT I [12], CABG-Patch, MUSTT [13], MADIT II [9], CAT [14], AMIOVIRT [15], COMPANION [16], DEFINITE [17], SCD-HeFT [18], and DINAMIT [10].

A complete analysis of these data has allowed to define the indications for these devices [2–5]. Thus the patients who reaped the biggest benefit from the ICD in primary prevention are those who present a chronic left ventricular dysfunction at distance from an acute myocardial infarction or those within the context of a nonischemic dilated cardiomyopathy. Only four studies did not demonstrate the beneficial character of the ICD. The aforementioned studies, however [10, 14, 15], were carried out on a limited number of patients (CAT [14] and AMIOVIRT [15]) or in a context of recent myocardial infarction (between the 6th and the 40th day for DINAMIT [10]) or concerned implantations following coronary bypass surgery (CABG-Patch), a treatment which decreases considerably the relative risk of sudden death in the control groups.

On the other hand, the MADIT I [12] study carried out on a group of 196 patients in a context of ischemic heart disease and prior infarct with a left ventricular ejection fraction ≤35% highlighted a reduction in the annual mortality of 54% compared to the control group [12]. Coming from the same team, the MADIT II study concerning a larger sample size of 1232 patients, in a context of ischemic heart disorder with left ventricular ejection fraction ≤30% estimated at least 1 month after an infarct, reinforced these results with a reduction in annual mortality of 31% compared to the control group [9]. The MUSTT study, regarding a group of 704 patients, showed a reduction in mortality of 51% in the patients implanted in comparison to the control group which consisted of coronary patients for whom a ventricular hyper excitability could be medically treated without resort to a ICD [13]. The study COMPANION, concerning 1520 patients with ejection fraction ≤35%, 59% of whom were coronary, confirmed the advantage of the ICD with a reduction of 36% in the annual mortality when it was associated with a biventricular pacemaker compared to the patients treated medically or by a biventricular resynchronization only [17]. Regarding the group with nonischemic dilated cardiomyopathy and a left ventricular ejection fraction ≤35%, the DEFINITE study concluded a decrease in the annual mortality of 35% [17]. The largest sample size came from the SCD-HeFT study with 2521 cases with cardiac insufficiency and a left ventricular ejection fraction ≤35% of ischemic etiology for 52% of the cases [18]. In this study, the reduction in the annual mortality with regard to the control group was 23%.

Finally, a meta-analysis which ensues from the analysis of these ten randomized studies concluded a relative reduction of 25% and an absolute reduction of 7.9% in the global mortality on a 2- to 4-year follow-up of the patients with a ICD [11].

In consequence, the recommendations concerning the implantation of ICD in primary prevention of sudden cardiac death put forward are: [2–5]

The coronary patient with or without symptoms of cardiac insufficiency (NYHA II or III) with a left ventricular ejection fraction ≤30% estimated at least 40 days after an IDM and 3 months after surgical revascularization or angioplasty
The coronary patient with left ventricular dysfunction (LVEF ≤35%) estimated at least 40 days after an infarct and 3 months after surgical revascularization or angioplasty presenting a triggerable ventricular arrhythmia (VT or VF)
The patient presenting a seemingly primitive dilated heart disorder with left ventricular dysfunction (LVEF ≤30%) and symptomatic (NYHA II or III)
The patients with documented ventricular fibrillation or hemodynamically not tolerated ventricular tachycardia in the absence of reversible causes or within 48 h after myocardial infarction who are receiving chronic optimal medical therapy and have a reasonable expectation of survival with a good functional status >1 year
The patient with hypertrophic cardiomyopathy with an estimated 5-year risk of sudden death ≥6% and a life expectancy >1 year following detailed clinical assessment that takes into account the lifelong risk of complications and the impact of an ICD on lifestyle, socioeconomic status, and psychological health
Cardiac amyloidosis, restrictive cardiomyopathy, and genetic disease at high risk of sudden death by ventricular fibrillation without any other known effective treatment

In patients with cardiac failure who remains symptomatic (NYHA III or IV) under optimal medical treatment, with left ventricular dysfunction (LVEF ≤35%) and duration of the QRS >120 ms, a biventricular pacemaker is recommended in association with the ICD for cardiac resynchronization.

6.3.2 Secondary Prevention of Sudden Cardiac Death

Secondary prevention by the ICD allowed a 27% reduction in the global mortality of the patients concerned [19]. Moreover, in the AVID study relating to 1016 patients having presented a cardiac arrest during a ventricular tachycardia or fibrillation, the ICD resulted in a decrease in mortality, respectively, of 39, 27, and 31% at 12, 24, and 36 months, in comparison to the control group treated by amiodarone alone [20]. In the CIDS study, including 658 cardiac arrest survivors due to a ventricular tachycardia or fibrillation, the ICD tended to decrease, in a not significant way, the relative risk of mortality of 33% after 5 years in comparison to the control group benefiting from an anti-arrhythmic treatment by amiodarone alone [21]. The CASH study including also a limited group of 288 patients and realized according to the same protocol as the two previous studies concluded to a nonsignificant decrease in the mortality of 23% at 9 years in comparison to the groups treated medically by amiodarone or metoprolol alone [19]. Due to the restrained sample size, these two studies were not significant. A meta-analysis merging these three studies allowed to conclude significantly in a reduction of 27% in the global mortality of the ICD group and more particularly when left ventricular ejection fraction is ≤35%. The recommendations concerning the indications ICD implantation in secondary prevention of sudden death are as follows: [ 2–5]