Cardiopulmonary effects of internal cardioverter/defibrillator implantation

[History of the implantable cardioverter-defibrillator in Germany]

The implantable cardioverter-defibrillator (ICD) was a breakthrough in the prevention of sudden cardiac death. After years of technical development in the USA, Michel Mirowski succeeded in proving reliable automatic defibrillation of ventricular tachyarrhythmias through initial human implantations in 1980, despite many obstacles. Nearly 4 years later, the first patients received ICDs at multiple centers in Germany. Subsequently, outside the USA, Germany became the country with highest implantation rates. The absolute number of implantations remained small as long as implantations required epicardial defibrillation electrodes and therefore thoracotomy by cardiac surgeons. Pacemaker-like implantation using a transvenous defibrillation electrode with a pectoral ICD became feasible in the early 1990s pushing implantation rates to the next level. Technical advancements were accompanied by clinical research in Germany, and often, the first-in-human studies were conducted in Germany. In 1991, the first guidelines for indications were established in the USA and Germany. Several randomized studies on indications were published between 1996 and 2009, mostly led by American teams with German participation, but also under German leadership (CASH, CAT, DINAMIT, IRIS). The DANISH study in 2016 questioned the results of these long-standing studies. Instead of providing ICDs to patients using a broad indication, future efforts aim to identify patients who, despite optimal medical therapy, cardiac resynchronization therapy (CRT), and/or catheter ablation, need protection against sudden cardiac death. Risk scores incorporating myocardial scars in magnetic resonance imaging (MRI) and genetic information are expected to contribute to more individualized and effective indications.

Pseudo-ginsengenin DQ ameliorated aconitine-induced arrhythmias by influencing Ca2+ and K+ currents in ventricular myocytes

Pseudo-ginsengenin DQ (PDQ) is the product of the oxidative cyclization of protopanaxadiol. PDQ exhibits various bioactivities, including reversal of multidrug resistance in cancer, renal protective effects against acute nephrotoxicity and attenuating myocardial ischemia injury induced by isoproterenol or ligation of coronary arterials, but its effect on arrhythmias has not been clear until now. Because of the complicated effects of ginseng on the cardiovascular system, it is necessary to investigate whether PDQ affects arrhythmias, which are always concomitant with other cardiac diseases. Aconitine was used to induce arrhythmia in vivo. To understand its electrophysiological fundamental, whole-cell patch-clamp was used to record the L-type calcium current (I_Ca,L) and potassium currents (I_K and I_K1) in the ventricular myocytes in rats. Oral administration of PDQ exerted obvious antiarrhythmic effects, as indicated by the decreased incidence rate, lower number of occurrences, and shorter duration time of ventricular tachycardia and ventricular tachycardia, decreased mortality rate and increased survival time. I_Ca,L and I_K were inhibited by PDQ treatment while I_K1 was not affected. To conclude, PDQ may have an anti-arrhythmia effect through inhibiting I_Ca,L and I_K.

Pseudo-ginsengenin DQ (PDQ) is the product of the oxidative cyclization of protopanaxadiol. PDQ could ameliorate aconitine-induced arrhythmias by influencing Ca²⁺ and K⁺ currents in ventricular myocytes.

The Expression of B-Type Natriuretic Peptide After CaCl2-Induced Arrhythmias in Rats

To investigate the patterns of B-type natriuretic peptide (BNP) expression after arrhythmia, BNP was assessed at different time points (0 minute, 10 minutes, 30 minutes, 1 hour, 3 hours, and 6 hours) in CaCl2-induced arrhythmia in rats through various methods such as immunohistochemistry, Western blotting, quantitative real-time polymerase chain reaction, and enzyme-linked immunosorbent assay. Immunohistochemistry results showed that the expression of BNP in the endocardium was higher than that in the epicardium in rats undergoing sustained arrhythmias. The BNP-to-GAPDH (glyceraldehyde-3-phosphate dehydrogenase) ratios determined by Western blotting analysis revealed no change at 0 minute but increased at 10 minutes and reached the first peak (0.48 [0.03]) at 30 minutes. After a brief decline, the second peak was observed at 6 hours (0.54 [0.03]). Similar patterns of BNP messenger RNA expression were also observed by quantitative real-time polymerase chain reaction. The plasma BNP concentrations did not change after initial bouts of cardiac arrhythmias but significantly increased 30 minutes after CaCl2 injections. The results demonstrate that arrhythmia causes an elevation of BNP in the myocardium and blood, and BNP messenger RNA increases in initial arrhythmia while its protein in myocardium and plasma does not; however, both of them were elevated after sustained arrhythmia. Such an elevated BNP expression, which is directly related to the severity and duration of the arrhythmias, may suggest the existence of fatal arrhythmia in sudden cardiac death.

[Implantation of cardioverter-defibrillators. How much anesthesia is necessary?]

Updated cardiologic guidelines constitute the background for an extended spectrum of indications for the implantation of automatic implantable cardioverter defibrillators (AICDs) and lead to an increasing number of operative implantations of AICDs. Moreover, during implantation of devices for cardiac resynchronization therapy the anesthesiologist is responsible for the most critically ill patients with the longest duration of surgery. As a result anesthesiologists face an increasing number of critically ill patients, whose management contributes to perioperative outcome. Automatic implantable cardioverter defibrillators can be implanted either during general anesthesia, local anesthesia or during a combination of local anesthesia combined with deep conscious sedation accomplished by an anesthesiologist. Besides economic aspects there is an increasing demand for anesthesia with the least cardiovascular side effects and rapid recovery in the often seriously ill patient with preexisting limitations of cardiac and pulmonary functions. Accordingly procedure and anesthesia-associated risks are reviewed and an algorithm for anesthesia management is suggested.

Target-controlled infusion or manually controlled infusion of propofol in high-risk patients with severely reduced left ventricular function

OBJECTIVE

To compare hemodynamics, time to extubation, and costs of target-controlled infusion (TCI) with manually controlled infusion (MCI) of propofol in high-risk cardiac surgery patients.

DESIGN

Prospective, randomized.

SETTING

Major community university-affiliated hospital.

PARTICIPANTS

Twenty patients undergoing first-time implantation of a cardioverter-defibrillator with severely reduced left ventricular function (left ventricular ejection fraction <30%).

INTERVENTIONS

Anesthesia was performed using remifentanil, 0.2 to 0.3 microg/kg/min, and propofol. Propofol was used as TCI (plasma target concentration, 2 to 3 microg x mL; n = 10) or MCI (2.5 to 3.5 mg/kg/hr; n = 10).

MEASUREMENTS AND MAIN RESULTS

Hemodynamics were measured at 6 data points: T1, before anesthesia; T2, after intubation; T3, after skin incision; T4, after first defibrillation; T5, after third defibrillation; and T6, after extubation. There were no significant hemodynamic differences between the 2 groups. Dobutamine was required to maintain cardiac index >2 L/min/m(2) in significantly more patients of the TCI group than of the MCI group. Mean dose of propofol was higher in the TCI patients (6.0 +/- 1.0 mg/kg/hr) than in the MCI patients (3.0 +/- 0.4 mg/kg/hr) (p < 0.05), whereas doses of remifentanil did not differ. Time to extubation was significantly shorter in the MCI (11.9 +/- 2.4 min) versus the TCI group (15.6 +/- 6.8 min). Costs were significantly lower in MCI patients (34.73 dollars) than in TCI patients (44.76 dollars).

CONCLUSIONS

In patients with severely reduced left ventricular function, TCI and MCI of propofol in combination with remifentanil showed similar hemodynamics. TCI patients needed inotropic support more often than MCI-treated patients. Although extubation time was longer in TCI patients and costs were higher, both anesthesia techniques can be recommended for early extubation after implantation of a cardioverter-defibrillator.

Cerebral blood flow velocity during repeatedly induced ventricular fibrillation

STUDY OBJECTIVE

To investigate the effect of induced ventricular fibrillation and defibrillation on cerebral blood flow (CBF) was investigated using a transcranial Doppler.

DESIGN

Prospective clinical study.

SETTING

University hospital.

PATIENTS

12 ASA physical status III and IV patients who underwent implantable cardioverter defibrillator placement during general anesthesia.

INTERVENTIONS

Cerebral blood flow velocity was measured repeatedly during induced ventricular fibrillation and subsequent defibrillation.

MEASUREMENTS AND MAIN RESULTS

The mean flow velocity in the middle cerebral artery was measured using a transcranial Doppler. The mean flow velocities decreased significantly immediately after ventricular fibrillation was induced, but they returned to preventricular fibrillation levels immediately after successful defibrillation. Repeatedly induced ventricular fibrillations have no cumulative detrimental effect on the CBF velocity.

CONCLUSIONS

Repetitively induced ventricular fibrillation and defibrillation during the insertion of implantable cardioverter defibrillator did not show any detrimental changes in CBF. Transcranial Doppler may be a more sensitive device than other currently available cerebral monitors to detect changes in cerebral circulation during a brief episode of ventricular fibrillation and defibrillation.

Total intravenous anesthesia with remifentanil and propofol for implantation of cardioverter-defibrillators in patients with severely reduced left ventricular function

OBJECTIVE

To determine the cardiocirculatory effects of total intravenous anesthesia (TIVA) using remifentanil and propofol in high-risk cardiac surgical patients.

DESIGN

Prospective study of 20 patients undergoing first-time implantation of a cardioverter-defibrillator (ICD).

SETTING

Major, community, university-affiliated hospital.

PARTICIPANTS AND INTERVENTIONS

In 20 patients with severely reduced left ventricular function (left ventricular ejection fraction <30%) undergoing first-time implantation of an ICD, TIVA using remifentanil and propofol was performed.

MEASUREMENTS AND MAIN RESULTS

Extensive hemodynamic monitoring using a pulmonary artery catheter was performed: (T1) before induction of anesthesia, (T2) after intubation, (T3) after skin incision, (T4) after first defibrillation, and (T5) 10 minutes after extubation. Propofol, 3.0 +/- 0.6 mg/kg/h (range, 1.9 to 4.4 mg/kg/h), and remifentanil, 0.30 +/- 0.05 microg/kg/min (range, 0.21 to 0.40 microg/kg/min), were used. Total costs added up to US $44.60 per patient. Patients could be extubated within 12.5 +/- 4.2 minutes after stopping anesthesia. There were significant decreases in heart rate (HR; from 77 +/- 12 to 57 +/- 10 beats/min [T3]), mean arterial blood pressure (MAP; from 98 +/- 14 to 70 +/- 12 mmHg [T2]), and systemic vascular resistance (from 1,551 +/- 309 to 1,233 +/- 274 dyne x s x cm(-5) [T2]). Cardiac index (CI) slightly decreased only at T3 (from 2.46 +/- 0.42 to 1.92 +/- 0.29 L/min/m2; p = 0.04). The decrease in MAP could easily be treated by volume infusion in most patients (17 patients). Sixty-five percent of the patients needed dobutamine to increase CI to greater than 2.0 L/min/m2 (mean dose, 2.2 +/- 1.8 microg/kg/min). Dobutamine could be stopped before extubation in all patients. No patient needed sustained inotropic or ventilatory support and intensive care therapy could be avoided.

CONCLUSION

TIVA using remifentanil and propofol in patients with severely reduced left ventricular function is safe, well-controllable, and allows early extubation after implantation of an ICD. Because patients without complications did not need a postoperative intensive care stay, costs may be considerably reduced.

Myocardial lactate extraction during repeated fibrillation/defibrillation episodes in defibrillator implantation testing

Intraoperative testing with several fibrillation/defibrillation episodes (FDEs) is routinely performed during defibrillator implantation. Testing is considered safe even in patients with severe cardiac impairment, provided the recovery timespans and number of FDEs are adapted to the individual patient. Myocardial lactate extraction (MLE) was examined in two testing protocols. In 30 patients with coronary artery disease defibrillator implantations were performed under intravenous anesthesia. A percutaneous catheter was positioned into the coronary sinus (CS) underfluoroscopy. Two groups were randomly formed: group A (n = 20, mean number of FDEs: 4.2/patient) with 2 minutes waiting time between FDEs, and group B (n = 10, mean number of FDEs 4.1/patients) with 10 minutes between FDEs. Defibrillation pulses were released 15 seconds after T wave shock induced fibrillation. To estimate MLE, arterial and CS blood samples were collected before and after each FDE. After the last FDE, samples were obtained after 5, 10, and up to 20 minutes. In group A, MLE fell from a baseline value of 29.6% +/- 3.6% before the FDEs to 7.8% +/- 5.4% immediately after the episodes. MLE recovered to 27.2% +/- 6.5% within 1 minute and overshot to 35.6% +/- 5.8% within 5 minutes. In group B, MLE decreased from 37.6% +/- 7.5% to 15.1% +/- 8.1% immediately after each FDE and rose to its original value (33.6 +/- 7.8) within the 5-minute recovery period. MLE decreased immediately after each FDE, and recovered within 1 minute even in poor left ventricular function. For full MLE recovery a 2-minute wait between episodes is sufficient, if the total number of FDEs does not exceed four.

Effect of ventricular shock strength on cardiac hemodynamics

INTRODUCTION

The effect of implantable defibrillator shocks on cardiac hemodynamics is poorly understood. The purpose of this study was to test the hypothesis that ventricular defibrillator shocks adversely effect cardiac hemodynamics.

METHODS AND RESULTS

The cardiac index was determined by calculating the mitral valve inflow with transesophogeal Doppler during nonthoracotomy defibrillator implantation in 17 patients. The cardiac index was determined before, and immediately, 1 minute, 2 minutes, and 4 minutes after shocks were delivered during defibrillation energy requirement testing with 27- to 34-, 15-, 10-, 5-, 3-, or 1-J shocks. The cardiac index was also measured at the same time points after 27- to 34-, and 1-J shocks delivered during the baseline rhythm. The cardiac index decreased from 2.30 +/- 0.40 L/min per m2 before a 27- to 34-J shock during defibrillation energy requirement testing to 2.14 +/- 0.45 L/min per m2 immediately afterwards (P = 0.001). This effect persisted for > 4 minutes. An adverse hemodynamic effect of similar magnitude occurred after 15 J (P = 0.003) and 10-J shocks (P = 0.01), but dissipated after 4 minutes and within 2 minutes, respectively. There was a significant correlation between shock strength and the percent change in cardiac index (r = 0.3, P = 0.03). The cardiac index decreased 14% after a 27- to 34-J shock during the baseline rhythm (P < 0.0001). This effect persisted for < 4 minutes. A 1-J shock during the baseline rhythm did not effect the cardiac index.

CONCLUSION

Defibrillator shocks > 9 J delivered during the baseline rhythm or during defibrillation energy requirement testing result in a 10% to 15% reduction in cardiac index, whereas smaller energy shocks do not affect cardiac hemodynamics. The duration and extent of the adverse effect are proportional to the shock strength. Shock strength, and not ventricular fibrillation, appears to be most responsible for this effect. Therefore, the detrimental hemodynamic effects of high-energy shocks may be avoided when low-energy defibrillation is used.

Changes in human coronary sinus blood flow and myocardial metabolism induced by ventricular fibrillation and defibrillation

BACKGROUND

During implantation of cardioverter-defibrillators, repeated inductions of ventricular fibrillation and defibrillation are performed. Little is known about the myocardial metabolism associated with ventricular fibrillation and defibrillation in humans.

METHODS

Sixteen patients scheduled for transvenous cardioverter-defibrillator implantation were included in the study. In 10 of the patients, blood samples were taken simultaneously in the coronary sinus and radial artery and analyzed for PO2, PCO2, standard bicarbonate, pH, lactate, alanine, glucose, and glycerol. Oxygen saturation, base excess, and oxygen content were calculated. The patients were studied before, shortly after, and 2 and 5 minutes after successful defibrillation. In six of the patients, coronary sinus blood flow was registered continuously.

RESULTS

The coronary sinus blood flow declined from a basal value of 93 +/- 16 mL/min to 35 +/- 6 mL/min 14 +/- 2 seconds after induction of ventricular fibrillation. Following termination of ventricular fibrillation, coronary sinus blood flow increased to a peak value of 227 +/- 75 mL/min. Oxygen saturation, PO2, and oxygen content in the coronary sinus increased by approximately 25% shortly after each episode of ventricular fibrillation and defibrillation. The coronary sinus lactate increased and the arterio-coronary sinus lactate difference decreased shortly after each of the four episodes, but was normalized within 2 minutes.

CONCLUSIONS

Repeated threshold tests during defibrillator implantation did not cause any long-lasting or cumulative metabolic effects, indicating that the described technique, with a 5-minute recovery period in between episodes, is safe as regards myocardial metabolism.

A prospective evaluation of two defibrillation safety margin techniques in patients with low defibrillation energy requirements

INTRODUCTION

In patients undergoing defibrillator implantation, an appropriate defibrillation safety margin has been considered to be either 10 J or an energy equal to the defibrillation energy requirement. However, a previous clinical report suggested that a larger safety margin may be required in patients with a low defibrillation energy requirement. Therefore, the purpose of this prospective study was to compare the defibrillation efficacy of the two safety margin techniques in patients with a low defibrillation energy requirement.

METHODS AND RESULTS

Sixty patients who underwent implantation of a defibrillator and who had a low defibrillation energy requirement (< or = 6 J) underwent six separate inductions of ventricular fibrillation, at least 5 minutes apart. For each of the first three inductions of ventricular fibrillation, the first two shocks were equal to either the defibrillation energy requirement plus 10 J (14.6+/-1.0 J), or to twice the defibrillation energy requirement (9.9+/-2.3 J). The alternate technique was used for the subsequent three inductions of ventricular fibrillation. For each induction of ventricular fibrillation, the first shock success rate was 99.5%+/-4.3% for shocks using the defibrillation energy requirement plus 10 J, compared to 95.0%+/-17.2% for shocks at twice the defibrillation energy requirement (P = 0.02). The charge time (P < 0.0001) and the total duration of ventricular fibrillation (P < 0.0001) were each approximately 1 second longer with the defibrillation energy requirement plus 10 J technique.

CONCLUSION

This study is the first to compare prospectively the defibrillation efficacy of two defibrillation safety margins. In patients with a defibrillation energy requirement < or = 6 J, a higher rate of successful defibrillation is achieved with a safety margin of 10 J than with a safety margin equal to the defibrillation energy requirement.

Brief episodes of ventricular fibrillation do not influence postischemic cerebral perfusion assessed by positron emission tomography

OBJECTIVES

To establish the defibrillation threshold in patients receiving an implantable cardioverter defibrillator, at least three episodes of ventricular fibrillation are induced and converted back to regular rhythm, using direct current countershocks. The aim of this study was to examine the influence of repeated short episodes of ventricular fibrillation on global and regional cerebral perfusion.

DESIGN

A prospective, descriptive study.

SETTING

A positron emission tomography laboratory at a university hospital.

PATIENTS

Four patients, admitted for defibrillation threshold tests 2 yrs after the implantation of a cardioverter defibrillator, were included in the study. Global and regional cerebral blood flow was measured by cerebral positron emission tomography, using an 15O-labeled tracer under propofol-induced general anesthesia. Electroencephalograms (EEGs) were concomitantly recorded.

INTERVENTIONS

Induction and conversion of ventricular fibrillation.

MEASUREMENTS AND MAIN RESULTS

No effect on global cerebral perfusion was observed after induced ventricular fibrillation lasting 21 +/- 3 secs. The average global cerebral perfusion was 23 +/- 1 mL/100 g/min after induction of anesthesia and 31 +/- 8 mL/100 g/min and 24 +/- 2 mL/100 g/min immediately after the termination of the first and second ventricular fibrillation episodes, respectively. Ten minutes after the second and the third threshold tests, global cerebral perfusion was 21 +/- 1 mL/100 g/min and 21 +/- 2 mL/100 g/min, respectively. Regional cerebral perfusion and EEGs were not influenced.

CONCLUSION

Short episodes of ventricular fibrillation did not induce any measurable effects on global and regional cerebral perfusion detectable by positron emission tomography 30 secs and 10 mins after restitution of sinus rhythm.

Probability of successful defibrillation at multiples of the defibrillation energy requirement in patients with an implantable defibrillator

BACKGROUND

The probability of successful defibrillation has been determined in normal animals but not in patients undergoing defibrillator implantation. Therefore, the purpose of this prospective study was to determine the probability of successful defibrillation in humans on the basis of a step-down defibrillation energy requirement.

METHODS AND RESULTS

Fifty-three consecutive patients underwent five separate inductions of ventricular fibrillation after the defibrillation energy requirement was determined with the use of small decrements and a step-down protocol (20, 15, 12, 10, 8, 6, 5, 4, 3, 2, 1, and 0.8 J). The first shock energy for defibrillation was either 1.0, 1.3, 1.5, 1.7, or 2.0 times the defibrillation energy requirement, and the likelihoods of successful defibrillation were 70+/-27%, 84+/-12%, 86+/-25%, 80+/-29%, and 88+/-32%, respectively (P=.03). The frequencies of uniformly successful defibrillation (5 of 5 defibrillation attempts) were 30%, 27%, 60%, 64%, and 73%, respectively (P=.01). Seven patients in whom the defibrillation energy requirement was <4 J had an overall rate of successful defibrillation of 54+/-20% compared with 86+/-20% in the remaining 47 patients (P=.002). The likelihood of successful defibrillation at twice the defibrillation energy requirement was 98% in the 46 patients with a defibrillation energy requirement of >4 J and 67% in the 7 patients with a defibrillation energy requirement of <4 J (P=.17). An absolute safety margin of 7 J was associated with a 96% probability of successful defibrillation.

CONCLUSIONS

The probability of successful defibrillation is 70% at the defibrillation energy requirement. The probability plateaus at 88%, at twice the defibrillation energy requirement. A 96% probability of successful defibrillation is achieved at an absolute safety margin of 7 J, and a 98% success rate is achieved at energies that are twice the defibrillation energy requirement if the defibrillation energy requirement is >4 J. If the defibrillation energy requirement is <4 J, larger multiples of the defibrillation energy requirement are needed to achieve a high probability of successful defibrillation.

Impact of implant techniques on complications with current implantable cardioverter-defibrillator systems

Implantable cardioverter-defibrillator (ICD) treatment has been in use since 1980 to prevent sudden cardiac death. The high efficacy of the original epicardial systems to terminate tachyarrhythmias was impaired by a substantial perioperative mortality and morbidity. The more "modern" transvenous ICD systems have shown a similar high efficacy in terminating ventricular tachyarrhythmias, but with a lower mortality and morbidity. As a background for discussing the impact on complications with present transvenous implantation techniques, the literature was reviewed. A large pacemaker series was used for comparison. Lead complications clearly related to design, material, or manufacture were not reviewed. The present review, covering 107 references over 40 years, gives support for the notion that in transvenously implanted ICD patients the incidence of acute and late complications related to implantation technique is now acceptable. The rate of hematomas, symptomatic thromboembolic complications, perforations, and to a certain degree infections could be improved, however. The major risk factors for implantation-related complications are discussed, and suggestions for future improvement are given.

Cardiac output is not affected during intraoperative testing of the automatic implantable cardioverter defibrillator

INTRODUCTION

Perioperative mortality of patients undergoing implantation of automatic implantable cardioverter defibrillators (ICDs) has been reduced dramatically following the availability of transvenous-subcutaneous defibrillation leads. However, patients with severely reduced left ventricular function show a substantial rate of nonsudden cardiac mortality within the first year. Whether repeated intraoperative inductions of ventricular tachycardia/fibrillation (VT/VF) during implantation lead to hemodynamic deterioration and thus might contribute to development of end-stage heart failure in these patients is unknown. The purpose of the present study was to determine cardiac output and hemodynamic performance during transvenous-subcutaneous ICD implantation in patients with severe left ventricular dysfunction.

METHODS AND RESULTS

In 11 patients with a left ventricular ejection fraction (EF) < or = 0.35, cardiac output was measured automatically with a combined continuous cardiac output/mixed venous oxygen saturation pulmonary artery catheter system. ICD implantation was performed during standardized general anesthesia. In the 11 patients (EF = 27 +/- 2% [mean +/- SEM]) a total of 95 episodes of VT/VF followed by defibrillation were induced (episodes per patient = 9 +/- 1; range 6 to 11). Cardiac index was 2.2 +/- 0.2 L.min-1.m-2 after induction of anesthesia (before start of surgery), and 1.9 +/- 0.1 L.min-1.m-2 immediately before first induction of VT/VF. After the last episode of VT/VF, cardiac index was 2.1 +/- 0.2 L.min-1.m-2. Cardiac index measured 1, 2, and 3 minutes after induction of VT/VF was not significantly different when compared to the preinduction value during any episode of VT/VF induction. Similarly, stroke volume index was 39 +/- 5 mL.m-2 immediately before first induction of VT/VF and 36 +/- 3 mL.m-2 after the last episode of VT/VF (NS). At the end of surgery, hemodynamic parameters did not exhibit any significant difference when compared to the data obtained before start of ICD implantation and testing.

CONCLUSION

Extensive defibrillation tests during transvenous-subcutaneous ICD implantation in patients with severe left ventricular dysfunction are not associated with acute deterioration of cardiac performance.

[Anesthesia and implantable automatic defibrillator]

Since the introduction of first generation automatic implantable cardioverter defibrillators (AICD) in 1980, an increasing number of such devices have been inserted in patients at high risk for sudden death by ventricular tachycardia or fibrillation (VT/VF). With the improvement of technology and implanting techniques, devices may be inserted at present subcutaneously into the abdominal or the thoracic wall, rather than by thoracotomy. The anaesthesist is involved in the primary implantation of the AICD and the secondary testing of efficiency. Implantation generally requires general anaesthesia and the extension of monitoring is guided by the patient's underlying disease(s). The efficiency of the implanted system is tested one to two months later in inducing VT/VF under general anaesthesia and in determining the defibrillation threshold. The anaesthetist may also have to take care of patients with a AICD. For such cases the following recommendations can be made: a) gloves should be worn by doctors and nurses coming into contact with these patients, in order to limit the risk of electrification; b) a ring magnet must be available to inactivate the unit; c) in case of external defibrillation, the external paddles should be oriented perpendicularly to the line joining the two implanted electrodes; d) AICD should be disabled during electrocautery and prior to electroconvulsive therapy; e) the assistance of a electrophysiologist may be helpful for the management of these patients.

Systolic arterial pressure recovery after ventricular fibrillation in pigs

Ventricular fibrillation (VF) is induced during implantable cardioverter defibrillator insertion and can result in cardiovascular collapse. The relation between repeated VF trials of varying duration and systolic blood pressure (SBP) recovery rate was studied in 6 pigs. Two implantable cardioverter defibrillator patches were placed on the heart, and VF was varied in a cyclic pattern until cardiovascular collapse occurred. A negative logarithmic relation between SBP recovery rate and duration of VF was found in 4 of the pigs with correlation coefficients of 0.62 to 0.97 (p < 0.05). The overall correlation coefficient was 0.51 for all 116 data points (p < 0.001). Although there was a significant (p < 0.05) decrease in average (+/- standard error of the mean) baseline SBP in the second half of each experiment (83 +/- 5 mm Hg versus 77 +/- 6 mm Hg), no significant difference in SBP was observed during VF (17 +/- 1 mm Hg versus 16 +/- 1 mm Hg) or after 15 seconds of SBP recovery (51 +/- 4 mm Hg versus 46 +/- 3 mm Hg) between the two halves of the experiments. Cardiovascular collapse occurred without warning; epinephrine was effective in reversing it. In conclusion, SBP recovery rate and duration of VF have a negative logarithmic relation consistent with a negative effect on left ventricular contractility with prolongation of VF. The onset of cardiovascular collapse during implantable cardioverter defibrillator testing cannot be predicted on the basis of monitored blood pressure alone.

Systolic arterial pressure recovery after ventricular fibrillation/flutter in humans

Although the elective induction of cardiac arrest for implantable defibrillator insertion under general anesthesia is widely used, the hemodynamics of recovery of arterial blood pressure after cardiac arrest is not well-defined. Accordingly, the time course of recovery of systolic arterial pressure was studied in seven patients during the repetitive induction of ventricular fibrillation (n = 6) or ventricular flutter (n = 1). The mean number of episodes of cardiac arrest was 7 +/- 2, and the mean drop in systolic pressure was 84 +/- 16 mmHg. The mean recovery time for systolic pressure was 10 +/- 6 seconds, the average systolic pressure recovery rate was 13 +/- 14 mmHg/sec, and the mean percent systolic pressure recovery was 94% +/- 9%. A negative logarithmic relation was found to exist between the rate of systolic arterial pressure recovery and the duration of ventricular fibrillation or flutter with a correlation coefficient of 0.68 to 0.97 (P < 0.05) in five of the seven patients. A linear relation between the time for systolic pressure recovery and duration of asystole was also defined. These results are consistent with the view that prolongation of ventricular fibrillation or flutter increases the duration of arterial pressure recovery through a negative effect on left ventricular contractility. Increased understanding of these relations may lead to increased safety of implantable defibrillator insertion.

Hemodynamic deterioration during ICD implant: predictors of high-risk patients

Defibrillation threshold (DFT) testing during implantation of the cardioverter defibrillator is associated with hemodynamic deterioration and pump failure in many patients. We investigated the influence of DFT testing on cardiac function intraoperatively using a balloon-tipped catheter. In 13 consecutive patients with a nonthoracotomy approach, a mean of 3.4 +/- 1.4 episodes of ventricular fibrillation were induced with an overall ischemic time of 87 +/- 54 seconds. At the end of DFT testing, patients with a left ventricular ejection fraction (EF) of < 30% had significant impairment of cardiac index (1.6 +/- 0.5 L/min/m2 after testing vs 2.2 +/- 0.6 L/min/m2 before the procedure). One patient with severely comprised ventricular function needed prolonged positive inotropic support. The left ventricular function of patients with a preoperative EF > or = 30%, however, was not changed (2.2 +/- 0.5 L/min/m2 after testing and 2.2 +/- 0.5 L/min/m2 before testing). The two groups did not differ with respect to the number of testing episodes, ischemic time, or DFT. Thus patients with a low preoperative EF (< 30%) are threatened by a severe left ventricular deterioration during ICD implantation. Close hemodynamic monitoring with a balloon-tipped catheter is recommended in these patients.