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PubMed2004

Reasons for attending and not attending a support group for recipients of implantable cardioverter defibrillators and their carers.

There is evidence to suggest that people who have an implantable cardioverter defibrillator and their caregivers experience psychological distress. This qualitative descriptive study explored the experiences, concerns and needs of recipients of implantable cardioverter defibrillators and their caregivers who attended or did not attend a support group organized by a public hospital located in Perth, Western Australia, Australia. Eleven recipients of implantable cardioverter defibrillators and their caregivers participated in this study. Among those who attended the support group, four major themes were identified: providing information, connecting with others, helping others and attendance. Explanations for non-attendance included difficulties attending because of the location, not wanting to be reminded about the implantable cardioverter defibrillator, and a perception, among younger recipients, that the support group was comprised of mainly older recipients with whom they had little in common.

Adaptation, Psychological↗
PubMed2006

Implantable cardioverter-defibrillators: a new preventive medical option.

Implantable cardioverter-defibrillator (ICD or defibrillator) therapy has revolutionized the fields of cardiology and electrophysiology. Hundreds of thousands of patients at risk for sudden cardiac death receive them each year. The devices are not much larger than a pacemaker, and they have full pacemaker capabilities in addition to being able to shock patients out of life-threatening ventricular arrhythmias. The Multicenter Automatic Defibrillator Implantation Trial (MADIT) in 1996 was a landmark trial that showed for the first time a mortality benefit of ICD therapy over medications in patients at high risk for sudden death. Multicenter Automatic Defibrillator Implantation Trial II, published in 2002, extended these results to all patients with ischemic heart failure with depressed heart function. Candidates for ICD implantation include most patients with an ejection fraction of <30%, especially those with coronary artery disease. More work needs to be done to define those patients with nonischemic cardiomyopathies who will benefit from ICDs and biventricular pacing for heart failure.

Arrhythmias, Cardiac↗
PubMed1993

Effective defibrillation in pigs using interleaved and common phase sequential biphasic shocks.

Previous studies have shown that low internal defibrillation thresholds (DFTs) can be attained by using two pairs of electrodes and combining biphasic shocks with sequential timing. The purpose of this two-part study was to test the defibrillation efficacy of two new shock sequences, an interleaved biphasic, and a common phase sequential biphasic, that utilized two pairs of electrodes and were developed from the concept of sequential biphasic shocks. In the first part, defibrillation catheters were placed in the right ventricle and the superior vena cava of six anesthetized pigs. A small patch electrode was placed on the LV apex through a subxiphoid incision and a cutaneous patch was placed on the left thorax. The mean DFT energies for the interleaved biphasic (5.2 +/- 0.4 J) and the common phase sequential biphasic waveforms (5.4 +/- 0.4 J) were substantially less (P < 0.0001) than those for either the sequential monophasic (10.6 +/- 1.0 J) or single biphasic waveforms (9.0 +/- 1.0 J). In the second study, which used nine anesthetized pigs, the importance of phase reversal was demonstrated by the finding that the DFT energy of a common phase sequential biphasic shock (6.2 +/- 0.4 J) was much less than a common phase sequential monophasic shock (17.9 +/- 1.3 J, P < 0.0001); furthermore, the average DFT for four common phase sequential biphasic configurations (5.7 +/- 0.2 J) was much less than for a configuration that was similar except that current flow was not reversed in one phase so that no biphasic effect was present (19.7 +/- 1.2 J). The efficacy of common phase sequential biphasics was comparable to that of sequential biphasics. The effectiveness of sequential biphasics, interleaved biphasics, and common phase sequential biphasics is possibly due to two mechanisms: (A) an increase in the potential gradient during a later phase in regions that were low during the first phase, and (B) the exposure of most of the myocardium to a biphasic shock that reduces the minimum extracellular potential gradient needed to defibrillate.

Animals↗
PubMed1993

Defibrillation energy requirements with single endocardial (Endotak) lead.

The need for thoracotomy in usually high risk patients has limited the use of the implantable cardioverter defibrillator. Initial clinical results with endocardial and subcutaneous patch electrodes (SQPs) are encouraging. Using a single endocardial lead in the absence of a SQP for chronic implantation of the cardioverter defibrillator, the goal of the study was to obtain defibrillation thresholds (DFTs) of 15 Joules (J) or less and to investigate changes in DFT over time. We tested 19 consecutive patients (15 men, 4 women) age 62 +/- 8.5 years with malignant ventricular arrhythmias (14 VT/5 VF). The underlying heart disease was coronary artery disease in 15 patients, dilative cardiomyopathy in two patients, and primary electrical disease in two patients. Four patients had undergone previous cardiac surgery. Left ventricular ejection fraction ranged between 14% and 66% (39% +/- 12.6%). Pacing thresholds (0.54 +/- 0.17 V at 0.5 msec), R wave amplitude for pacemaker sensing (14.2 +/- 7.0 mV), slew rate (2.12 +/- 1.4 V/sec), and resistance (500.3 +/- 73.9 W) were sufficient in all patients. Eighteen patients met our endocardial implant criteria with a DFT < or = 15 J (10.05 +/- 4.03 J) using monophasic (14 patients) or biphasic (four patients) pulse wave forms. In the one remaining patient, with a DFT of 20 J, we implanted a SQP but there was no reduction of the DFT. All patients tested showed successful defibrillation prior to discharge. During follow-up of 88 patient-months (1-9 months), 114 spontaneous VT/VF episodes occurred in five patients and were all successfully terminated. Eleven patients with a minimum follow-up of 2 months were reassessed.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Pacing, Artificial↗
PubMed1994

Electrode polarity is an important determinant of defibrillation efficacy using a nonthoracotomy system.

Experimental and clinical data using epicardial patch electrodes and monophasic waveform suggest that electrode polarity may be an important determinant of defibrillation efficacy. Our objective was to examine the effect of electrode polarity in an animal model using a nonthoracotomy system and monophasic and biphasic waveforms for defibrillation. We examined the effect of lead polarity in 14 pentobarbital anesthetized dogs (21.1 +/- 2.4 kg) using monophasic and biphasic shocks and a nonthoracotomy system. Monophasic and single capacitor biphasic shocks of 10-msec total duration were used. The lead system consisted of a right ventricular catheter electrode with 4-cm2 surface area and a left chest wall subcutaneous patch electrode with 13.9-cm2 surface area. Electrode polarities RV(-)-Patch(+) and RV(+)Patch(-) were tested using both monophasic and biphasic waveforms. Alternating current was used to induce ventricular fibrillation and test shocks were delivered after 10 seconds of ventricular fibrillation. Each polarity configuration for monophasic and biphasic waveforms was tested four times at five different capacitor voltage levels (200-600 V, in 100-V increments). Defibrillation efficacy curves were constructed using logistic regression analysis for each animal and energies associated with 80% probability of successful defibrillation (E80) were determined. The mean E80 +/- SD values were as follows. Monophasic waveform: RV(-)Patch(+) 23.4 +/- 7.5 J; RV(+)Patch(-) 20.9 +/- 7.9 J (P < 0.03). Biphasic waveform: RV(-)Patch(+) 15.8 +/- 6.8 J; RV(+)Patch(-) 12.5 +/- 6.0 J (P < 0.03). The mean impedance values for both waveforms using either polarity ranged from 65.4 to 67 ohms and were not significantly different.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Early postoperative increase in defibrillation threshold with nonthoracotomy system in humans.

The stability of the defibrillation threshold (DFT) early after implantation of an implantable cardioverter defibrillator was evaluated in 15 patients. All but one patient had a three lead nonthoracotomy system using a subcutaneous patch, a right ventricular endocardial lead, and a lead in coronary sinus (n = 5) or superior vena cava (n = 9). Shocks were delivered using simultaneous in nine, sequential in three, and single pathway (coronary sinus not used) in one patient. DFTs were measured at implant (n = 15), 2-8 days postoperation (postop, n = 15), and 4-6 weeks later (n = 8). The DFT was defined as the lowest energy shock that resulted in successful defibrillation. The DFT was assessed with output beginning at 18 joules or 2-4 joules above the implant DFT. All shocks were delivered in 2- to 4-joule increments or decrements. DFTs were significantly higher postoperatively than DFTs at implant (22.7 +/- 7.0 J vs 16.9 +/- 3.9 J; P < 0.05). Eight of 15 patients had DFT determined at all three study periods. In these patients, DFT increased at postop (22.8 +/- 8.3 J vs 16.4 +/- 3.9 J at implant; P < 0.05) and returned to baseline at 4-6 weeks (16 +/- 7.1 J vs 16.4 +/- 3.9 J at implant; P = N.S.). Thus, in patients with a multilead nonthoracotomy system, a DFT rise was observed early after implant. The DFT appears to return to baseline in 4-6 weeks. These results have important implications for programming energy output after implantable cardioverter defibrillator implantation.

Adult↗
PubMed1994

Effectiveness of noninvasive programmed stimulation for initiating ventricular tachyarrhythmias in patients with third-generation implantable cardioverter defibrillators.

Previous generations of implantable cardioverter defibrillators (ICDs) required invasive electrophysiological testing to assess defibrillator function. Newer third-generation ICDs include the capability for performing noninvasive programmed stimulation (NIPS) and may reduce the need for invasive studies to assess tachycardia recognition and antitachycardia therapy algorithms. The effectiveness of ICD-based NIPS for the induction of ventricular arrhythmias has not, however, been formally assessed. Third-generation ICDs were implanted in 79 patients, who underwent a total of 166 postoperative defibrillator tests. NIPS with rapid ventricular pacing was performed in all patients in an attempt to induce ventricular fibrillation. In patients with prior sustained uniform ventricular tachycardia, programmed stimulation with up to three extrastimuli was performed in order to attempt to initiate the clinical ventricular tachcardia. Ventricular fibrillation was induced with NIPS in 146 of 166 studies (88%). Ventricular tachycardia was initiated with NIPS in 104 of 123 studies (85%). The type of defibrillator and the use of endocardial or epicardial rate sensing/pacing leads did not influence the efficacy of NIPS. NIPS with third-generation ICDs is generally effective at inducing ventricular fibrillation and clinically relevant ventricular tachycardias, and reduces the need to perform invasive electrophysiological testing following device implantation. In a minority of patients temporary transvenous pacing catheters must still be used to facilitate arrhythmia induction.

Adult↗
PubMed1994

Undersensing during ventricular tachyarrhythmias in a third-generation implantable cardioverter defibrillator: diagnosis using stored electrograms and correction with programming.

Third-generation implantable cardioverter defibrillators with stored electrograms allow diagnosis of various sensing problems that may lead to an inappropriate device response. Undersensing of ventricular tachyarrhythmias is a potentially serious problem, as it may lead to failure to deliver therapy. To determine the incidence of this problem, we reviewed 98 patients with Ventritex Cadence defibrillator systems and found 2 patients in whom defibrillation therapy was delayed or aborted because of undersensing during induced ventricular tachyarrhythmias. In both cases, examination of stored electrograms revealed variation in electrogram amplitude, which presumably resulted in failure of the autogain feature to increase its sensitivity enough to count each complex. During charging, criteria for redetection of sinus rhythm were met because of this undercounting, leading to failure to deliver defibrillation therapy. This problem was detected in both patients 4-6 weeks following device implant during device testing, and both patients had been started on antiarrhythmic drug therapy prior to this testing. Programming the sinus redetection parameter from nominal to slow, increasing the number of beats necessary to confirm resumption of sinus rhythm, corrected the problem in both patients. Device testing in the electrophysiology laboratory, routinely postoperatively and following initiation of antiarrhythmic drug therapy, and the ability to retrieve stored electrograms are useful in detecting such sensing anomalies.

Aged↗
PubMed1994

The economic impact of transvenous defibrillation lead systems.

The purpose of this study was to compare implant charges and convalescence for transvenous and epicardial defibrillation systems. Hospital stay, intensive care utilization, professional fees, and hospital bills were compared in 44 patients who underwent implantation of a cardiac defibrillator between September 1991 and May 1993. Twenty-five consecutive patients received an epicardial lead system, while 19 consecutive patients underwent implantation of the entire transvenous defibrillation system in the electrophysiology laboratory. There were no significant differences between the two groups in mean age or left ventricular ejection fraction. There was a significant reduction in postoperative hospital convalescence from 7.2 +/- 2.0 days with epicardial systems to 3.1 +/- 1.5 days with transvenous systems (P < 0.001). Postoperative intensive care unit stay was significantly reduced with transvenous systems compared with epicardial systems (0.1 +/- 0.2 vs 1.5 +/- 0.9 days; P < 0.001). Hospital charges were also significantly reduced with the transvenous lead system implants. Mean implant charges were lower with transvenous systems: $32,090 +/- $2,620 vs $38,307 +/- $2,701 (P < 0.001); convalescence charges were lower: $5,861 +/- $5,010 $12,447 +/- $4,969 (P < 0.001); the total hospital bill was also significantly lower with transvenous systems: $53,459 +/- $12,588 vs $71,981 +/- $16,172 (P < 0.001). Professional fees for implantation ($4,131 +/- $1,724 vs $6,100 +/- 0, P < 0.001), convalescence care ($1,258 +/- $960 vs $2,846 +/- $1,770; P < 0.001), and total professional fees ($12,925 +/- $4,772 vs $15,731 +/- $4,055, P < 0.05) were lower in the transvenous defibrillation group.(ABSTRACT TRUNCATED AT 250 WORDS)

Convalescence↗
PubMed1995

Defibrillator implantation in a patient with a persistent left superior vena cava.

The implantation of a transvenous cardioverter defibrillator (PCD 7217B) was performed in a patient with a persistent left superior vena cava. The defibrillation electrodes were positioned in the right ventricle and the superior vena cava via the right subclavian vein. A subcutaneous patch had to be implanted at the left lateral chest wall to achieve sufficient defibrillation thresholds. Three weeks later the system had to be removed because of a generator pocket infection. During the second implantation we placed one electrode in the persistent left superior vena cava perpendicular to the electrode in the right ventricle. Using this configuration transvenous defibrillation was possible without an additional subcutaneous patch.

Adult↗
PubMed1995

Woven wire patches are superior to solid disks for subcutaneous electrodes: implications for active can defibrillation.

The housing of the implantable cardioverter defibrillator (ICD) is being considered for a remote electrode to replace the conventional subcutaneous woven wire patch. It is not clear that the solid smooth and rigid metal surface of the ICD housing will provide the same performance as does the woven wire patch. We compared a solid titanium disk to a titanium woven wire patch for defibrillation performance in a canine model. The patch had a smaller outline area, a slightly smaller conductive perimeter, and slightly less of a small feature surface area than did the disk. The remote electrode (disk or patch) was inserted at the point of maximal apical cardiac impulse. A commercially available endocardial electrode was placed in the right ventricle (RV). Conventional biphasic shocks (140-microFrench capacitor and 65% tilt) were delivered between the RV and subcutaneous electrode. The patch had significantly lower resistances than did the disk (81.6 +/- 8.0 omega vs 90.0 +/- 11.6 omega P < 0.006). The patch also had significantly lower stored energy defibrillation thresholds than did the disk (8.0 +/- 2.6 J vs 9.3 +/- 3.3 J, P < 0.007). In spite of smaller values for every geometrical dimension, the woven wire patch out performed the solid disk for defibrillation with conventional biphasic waveforms. Since the ICD housing is typically smooth titanium, the use of waveforms better suited for the active can configuration may deserve a systematic evaluation.

Animals↗
PubMed1995

Influence of malpositioned transvenous leads on defibrillation efficacy with and without a subcutaneous array electrode.

Some patients cannot receive a transvenous lead system because of high defibrillation thresholds (DFTs). We hypothesized that a right ventricular (RV) catheter electrode not extending as far as possible into the RV apex could cause high DFTs. Recently, a subcutaneous array (SQA) electrode has been shown to lower DFTs substantially. We compared the influence of a malpositioned RV catheter electrode on defibrillation efficacy for endocardial lead systems with and without a SQA. In eight anesthetized pigs, defibrillation catheters were placed in the RV apex and near the junction of the superior vena cava (SVC) and right atrium. SQA, formed by three elements, each 20 cm in length, was placed in the left thorax. DFTs were determined for a biphasic waveform using an up/down protocol with the RV catheter at the apex and with it repositioned 1-cm and 2-cm proximal to the apex. The mean DFT energies for the configurations with a SQA were less than those without a SQA for every catheter position. The placement of the RV catheter away from the apex caused an increase in defibrillation energy for the configurations without a SQA (apex: 17.1 +/- 3.8 J [mean +/- SD]; 1 cm: 20.1 +/- 4.6 J; 2 cm: 27.6 +/- 9.5 J; P < 0.05), but not for the configurations with a SQA (apex: 12.2 +/- 2.2 J; 1 cm: 12.3 +/- 2.9 J; 2 cm: 12.1 +/- 0.9 J: P = NS). These results suggest that a malpositioned RV catheter electrode, at the time of implantation or by late dislodgment, significantly elevates DFTs for a total endocardial system but not for a system that includes a SQA.

Animals↗
PubMed1995

Subclavian crush syndrome complicating transvenous cardioverter defibrillator systems.

UNLABELLED: Subclavian crush syndrome, described with pacemaker leads implanted via subclavian puncture, may occur when conductor fractures and insulation breaches develop by compression of a lead between the first rib and clavicle. We reviewed our experience in 164 patients who underwent intended implantation of transvenous defibrillator systems to determine the clinical relevance of subclavian crush syndrome in defibrillator patients. Venous access was obtained via subclavian puncture in 114 patients (70%) and via cephalic cut-down in 50 patients (30%). Nonthoracotomy lead systems, with or without subcutaneous patch, were successfully implanted in 131 of 164 patients (79.9%). Thoracotomy was required in 32 patients (19.5%) and subxiphoid patch in 1 patient (0.6%). Over a mean of 12.9 months (range 1-62 months), 3 patients (1.8%) required revision of the rate sensing lead/coil or superior vena cava coil after development of lead compression fractures in the region of the clavicle and first rib. In all 3 patients the leads had been implanted via subclavian puncture (2.6% of patients in whom the subclavian technique was utilized). Two patients presented with spurious shocks. One patient was asymptomatic. CONCLUSIONS: When venous access is obtained via subclavian puncture, subclavian crush syndrome may develop in patients with transvenous defibrillator systems. Patients may be asymptomatic and lead fractures may go unrecognized. When implanting transvenous defibrillator systems, strong consideration should be given to obtaining venous access primarily via the cephalic cut-down technique.

Aged↗
PubMed1995

Defibrillation thresholds are lower with smaller storage capacitors.

Present implantable cardioverter defibrillators use a wide range of capacitance values for the storage capacitor. However, the optimal capacitance value is unknown. We hypothesized that a smaller capacitor, by delivering its charge in a time closer to the heart chronaxie, should lower the defibrillation threshold (DFT). We compared the energy required to defibrillate 10 open-chest dogs, after 15 seconds of ventricular fibrillation, with a monophasic, time-truncated waveform delivered from either a 85-microF or a 140-microF capacitor. Shocks were delivered through a pair of 14-cm2 epicardial patch electrodes: The two capacitors were randomly tested twice with each dog using a modified 3-reversal method for each DFT determination. The average stored and delivered DFT energies for the 85-microF capacitor were 6.0 +/- 1.7 joules and 5.2 +/- 1.5 joules, respectively, compared to 6.7 +/- 1.7 joules and 6.0 +/- 1.5 joules for the 140-microF capacitor (P = 0.01 and P = 0.004, respectively). The mean leading edge voltages were higher, the pulse duration shorter, and the mean impedance lower for the 85-microF capacitor. The impedance was inversely related to the pulse duration and the voltage decay suggesting that, at least in part, the mechanism of improved defibrillation could be accounted for by the waveform electrical characteristics. There was an equal number of episodes of postshock bradyarrhythmias and tachyarrhythmias following discharges from each capacitor. Moreover, there was no relationship between the likelihood of these arrhythmias and either the initial voltage or the delivered current nor there was a higher number of episodes of postshock hypotension following the smaller capacitor discharges.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1996

Comparative reproducibility of defibrillation threshold and upper limit of vulnerability.

The upper limit of vulnerability (ULV) is the strength at or above which VF is not induced when a stimulus is delivered during the vulnerable phase of the cardiac cycle. Previous studies have demonstrated a statistically significant correlation between the ULV and the defibrillation threshold (DFT) in groups of patients. However, the correlation between ULV and DFT may not be close in individual patients. This imperfect correlation may be due to physiological factors or to limitations of the measurement methods. The reproducibility of either DFT or ULV has not been studied critically. The purpose of this study was to compare the reproducibility of clinically applicable methods for determination of DFT and ULV. We prospectively studied 25 patients with a transvenous implantable cardioverter defibrillator (Medtronic 7219D) at postoperative electrophysiological study. DFT was defined as the lowest energy that defibrillated after 10 seconds of VF. The ULV was defined as the lowest energy that did not induce VF with three shocks at 0, 20, and 40 ms before the peak of the T wave in ventricular paced rhythm at a cycle length of 500 ms. Both the DFT and the ULV were determined twice for biphasic pulses using a three-step, midpoint protocol. There was no significant difference between the two determinations of DFT (10.1 +/- 5.9 J vs 10.4 +/- 5.8 J), the two determinations of ULV (13.4 +/- 6.8 J vs 13.8 +/- 6.6) or the DFT-ULV Pearson correlation coefficients for each determination (0.84, P < 0.001 vs 0.75, P < 0.001). To analyze reproducibility, Lin concordance coefficients for second determination versus first determination were constructed for both ULV and DFT. This coefficient is similar to the Pearson correlation coefficient, but measures closeness to the line of identity rather than the line of regression. The Lin concordance coefficient for ULV was higher than that for DFT (0.93, 95% CI 0.85-0.97 vs 0.64, 95% CI 0.33-0.82; P < 0.01). For paired comparison of defibrillation efficacy under different experimental conditions, the sample sizes required to detect differences of 2 J, 3 J, and 4 J (80% power, P < 0.05) were 52, 24, and 15 for DFT versus 15, 8, and 6 for ULV. We conclude that a simple, clinically applicable method for determination of ULV is more reproducible than the single point DFT. Measured correlations between the ULV and single point are limited by the reproducibility of the DFT measurement.

Defibrillators, Implantable↗
PubMed1996

Lead fracture in cephalic versus subclavian approach with transvenous implantable cardioverter defibrillator systems.

Lead fracture, occurring in approximately 1%-4% of patients, is an infrequent, but potentially catastrophic complication of permanent pacing systems. Its incidence in transvenous defibrillator systems has not been established. We analyzed data from 757 patients undergoing implantation of transvenous cardioverter defibrillator systems using the Medtronic Transvene Lead system between October 20, 1989 and June 25, 1992 to determine if site of venous approach influenced incidence of lead fracture. All patients received a 3-lead system in 1 of 3 configurations: (1) right ventricle/superior vena cava/subcutaneous patch; (2) right ventricle/coronary sinus/subcutaneous patch; or (3) right ventricle/superior vena cava/coronary sinus. Of 767 right ventricular leads placed, 523 were placed via the subclavian vein, 221 via cephalic vein, and 18 via the internal jugular (5 leads were implanted using another vein). The total number of leads is greater than the total number of patients, as five patients received a second defibrillator system if the initial system was explanted and reimplanted for any reason. Seven patients (0.9%) had right ventricular lead fracture, presenting with inappropriate defibrillator shocks (1), loss of pacing ability (3), both loss of pacing ability and inappropriate shocks (1), or increased pacing threshold (2). All patients required reoperation. All had leads placed by the subclavian venous approach, with chest X ray confirming fracture at the clavicle-first rib junction in 6 of 7 cases. Using Fisher's Exact test, the difference in lead fracture between subclavian and cephalic vein implant approached statistical significance (P = 0.08). The trend toward increased lead fracture incidence with leads placed via subclavian vein suggests that cephalic vein approach may be preferable to avoid this complication.

Defibrillators, Implantable↗
PubMed1997

A patch in the pectoral position lowers defibrillation threshold.

Implantable pacemaker cardioverter defibrillators are now available with biphasic waveforms, which have been shown to markedly improve defibrillation thresholds (DFTs). However, in a number of patients the DFT remains high. Also, DFT may increase after implantation, especially if antiarrhythmic drugs are added. We report on the use of a subcutaneous patch in the pectoral position in 15 patients receiving a transvenous defibrillator as a method of easily reducing the DFT. A 660-mm2 patch electrode was placed beneath the generator in a pocket created on the pectoral fascia. The energy required for defibrillation was lowered by 56% on average, and the system impedance was lowered by a mean of 25%. This maneuver allowed all patients to undergo a successful implant with adequate safety margin.

Defibrillators, Implantable↗
PubMed1997

Interactions between transvenous nonthoracotomy cardioverter defibrillator systems and permanent transvenous endocardial pacemakers.

Limited information is available regarding potential adverse interactions between transvenous nonthoracotomy cardioverter defibrillators and pacemakers. We describe our experience with 37 patients who have undergone successful implantation of both a transvenous defibrillator and pacemaker. The patients' mean age was 64 +/- 12.9 years. Thirty-three were male and four were female. The mean LVEF was 30.8% +/- 11.8%. The indications for pacemaker implantation included sick sinus syndrome in 13 patients, complete heart block in 15 patients, sinus bradycardia secondary to medications in 8 patients, and neurocardiogenic syncope in 1 patient. The indications for insertion of a defibrillator included medically refractory VT in 27 patients and sudden cardiac death in 10 patients. Twenty-three patients received an Endotak lead and 14 patients received a Transvene lead. Eighteen patients had a pacemaker prior to an ICD, 14 patients had an ICD prior to a pacemaker, and 4 patients had both devices placed simultaneously. Interaction was evaluated at implant of the second device and 1-3 days after both devices were placed. Detection of VF/VT was analyzed during asynchronous pacing (DOO/VOO) with maximum pacing output. In addition, in six patients, DFT was determined before and after pacemaker implantation. In 14 patients (38%), device interactions that could not always be optimally corrected were observed. In five patients, the pacemaker was reset to the "noise reversion" mode after high energy ICD discharge. Oversensing of atrial pacemaker stimuli resulted in inappropriate ICD firings in four patients. This was observed only with a specific device and could not be prevented by atrial lead repositioning in two of them, but required reprogramming of the pacemaker to the VVI mode. An increase in DFT was observed in five patients who had a pacemaker implanted after an ICD. Compared with previously published studies, a greater frequency of transvenous ICD and pacemaker interactions were observed. Considering that almost 50% of the patients already have a pacemaker at the time of ICD implant, the availability of defibrillators with dual chamber pacing capability will not eliminate the potential for this problem.

Aged↗