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PubMed2002

Short and medium time experience with a tined, multilumen steroid eluting defibrillation lead.

Both leads and pulse generators of implantable defibrillators have undergone important improvements during the last years. New leads should be tested against previous models to demonstrate safety and reliability. When introduced in 1995, the Medtronic 6932 pace, sense and defibrillation lead was compared to the alternative larger 6936 lead in a short-term randomized study with a mean follow-up of 2.4 +/- 2.0 months. A subgroup of patients were followed for 23.9 +/- 9.0 months. Three hundred and thirty-six patients were randomized to receive either the 6932 or the 6936 lead. Defibrillation threshold at implant, tested using a binary search protocol, was similar for the two leads. The pacing threshold was significantly lower for the 6932 lead both at implant and at follow-up, probably due to the steroid eluting tip of the electrode. R-wave amplitudes were similar for the leads, as were the complication rates. During about two years of follow-up, both leads performed well, with a slightly lower pacing threshold for the 6932 lead.

Adult↗
PubMed2002

Left ventricular dysfunction is associated with prolonged average ventricular fibrillation cycle length in patients with implantable cardioverter defibrillators.

OBJECTIVES: In cellular studies, ventricular refractoriness (ERP) is prolonged in heart failure (CHF), but clinical evidence is lacking. The average ventricular fibrillation cycle length (VFCL) has been shown to correlate with local ERP. We hypothesized that the VFCL increases with left ventricular (LV) dysfunction. Therefore, we evaluated intracardiac VFCL recorded by implantable defibrillators (ICD) in patients with and without LV dysfunction. METHODS: We analyzed intracardiac VFCL recorded by sensing leads of Ventak MINI (Guidant) ICD in 49 patients (35 men; age 54 +/- 13 years; 25 (51%) with coronary artery disease; mean LV ejection fraction (EF) 41 +/- 17%, range 76-10) from the European Ventak MINI Investigator Group. No patients were receiving antiarrhythmic drugs, including beta-blockers. Mean and median VFCL were obtained at predischarge testing during first charge time (4.5 +/- 2.7 s, range 1.4-11). RESULTS: Mean median VFCL was 186 +/- 21ms (range 150-230 ms). Patients with LVEF >/= 50% (n = 14) had shorter median VFCL than patients with LVEF < 50% (n = 35), (171 +/- 14 vs. 191 +/- 20 ms; p = 0.002). Median VFCL correlated with LVEF (r = -0.41; p = 0.003) and age (r = 0.28, p = 0.04), but was not significantly associated with charge time and defibrillation threshold at implant. Similar results occurred with mean VFCL. In multiple linear regression and correlation models, only LVEF% was a significant predictor (p < 0.05 for all models) of median VFCL. CONCLUSIONS: LV dysfunction prolongs averaged VFCL in patients at risk for malignant ventricular arrhythmias who have implantable cardioverter defibrillators. This phenomenon might be related to alterations in the ventricular refractory period.

Analysis of Variance↗
PubMed2003

Efficacy of atrial antitachycardia functions for treating atrial fibrillation: observations in patients with a dual-chamber defibrillator.

In patients with conventional indication for ICD implantation, atrial fibrillation may occur in more than 50% during the life-span of the device and may lead to severe adverse events. Dual chamber defibrillators with atrial antitachycardia functions, including prevention algorithms, arrhythmia detection capability and atrial therapy options (antitachy pacing and cardioversion) have been recently introduced. The aim of this review is to examine the effectiveness of these new devices and to identify patients who may benefit. We recently studied 112 patients who received the device because of life-threatening ventricular arrhythmias. Fifty-five percent of them had atrial fibrillation prior to implantation. During the follow-up (one year on average), 27% had at least one episode of sustained atrial tachyarrhythmia. Effectiveness of atrial antitachy pacing was 71% on regular atrial tachycardia and 36% on irregular atrial tachyarrhythmias. Atrial shock efficacy was over 90% when adequately programmed. Interestingly, near half of the episodes started as regular atrial tachycardia and accelerated and became less organized in few minutes. Early delivery of antitachy pacing may increase success rate and decrease the need for atrial shock. Furthermore, it may prevent atrial remodeling and reduce atrial fibrillation burden. Based on our experience, we recommend that all patients with a class I indication for defibrillator implantation (related to risk of ventricular arrhythmias) who have a history of or are at risk of developing atrial tachyarrhythmias should receive a dual chamber defibrillator equipped with atrial antitachycardia functions. Furthermore, patients either with a history of heart failure, with poor functional capacity (functional class III or IV), depressed left ventricular ejection fraction, a need for monitoring of atrial rhythm, or in whom there is some concern about appropriate detection of ventricular arrhythmias, may benefit from a single device capable of managing ventricular and supraventricular arrhythmias.

Arrhythmias, Cardiac↗
PubMed2004

Feasibility and accuracy of pre-procedure imaging of the proximal cephalic vein by duplex ultrasonography in pacemaker and defibrillator implantation.

BACKGROUND: Failure of the cephalic venous approach in pacemaker and defibrillator implantation is always due to the small size and difficulty in isolation of the cephalic vein. We propose that pre-procedure imaging of the proximal cephalic vein is valuable to achieve successful access of cephalic vein. However, the feasibility and accuracy of duplex ultrasonographic imaging of the proximal cephalic vein are unknown. METHODS: The study enrolled 30 consecutive patients who underwent new implantation of permanent pacemakers or defibrillators at our institute. An ultrasound probe scanned along the plane 2 cm beneath the inferior margin of the clavicle to locate the cephalic vein before device implantation. If the vein was well visualized, the venous diameter and the vertical depth were measured. The corresponding surface location of the vein on the chest wall was also identified and recorded by duplex ultrasonography. The echo-derived vertical depths and vascular findings were compared with those measured during surgery. RESULTS: All proximal cephalic veins were well visualized in the infraclavicular region by duplex ultrasonography. They were compressible, patent in color Doppler ultrasound imaging, and displayed phasic change of Doppler signal during respiration, indicating patency in all study veins. The average diameter of the target cephalic vein was 7.7 +/- 1.6 mm (range, 5.0-11.1 mm). The echo-derived vertical depth of the proximal cephalic veins was highly correlated with the depth measured during surgery (28.4 +/- 5.5 vs. 28.4 +/- 5.6 mm, r = 0.93, P < 0.0001). All target cephalic veins were isolated after exploration via the estimated surface location of the chest wall by pre-procedure duplex ultrasonography. Seven (23%) of the studied patients did not have their cephalic vein cannulated successfully. CONCLUSION: The target proximal cephalic vein in pacemaker and defibrillator implantation can be precisely imaged and localized by duplex ultrasonography. Although further studies are needed, our findings pave a way to further study and clarify the implantation problems of cephalic vein approach.

Defibrillators, Implantable↗
PubMed2004

Dual defibrillator improves quality of life and decreases hospitalizations in patients with drug refractory atrial fibrillation.

AIM OF THE STUDY: to evaluate the impact of dual defibrillator implantation on quality of life and resource utilization in patients with drug refractory atrial fibrillation (AF) without prior ventricular arrhythmias. METHODS: Forty patients (28 M, mean age 64 +/- 10) received a dual defibrillator Medtronic 7250. AF was persistent in 60% and paroxysmal in 40%. RESULTS: The follow-up lasted 15 +/- 4 months (range 12-30). Eighty-five percent of patients had atrial tachyarrhythmia recurrences. Among 1366 treated episodes, overall success rate was 60.1% for antitachy pacing and 88.2% for atrial shock. Within one year after implant, arrhythmia related hospitalization number decreased from 1.5 +/- 2.0 to 0.4 +/- 0.8 ( p < 0.01) and 77% of patients were free from hospitalization. As regard to quality of life, Symptom Checklist/Frequency and Severity Scale improved after implant for all items and SF-36 questionnaire showed significant improvements in physical activities because of health problems and social activities. The patients assigned to early delivery of atrial shock after AF onset, when compared with the patients who did not accept atrial shock, showed a significant reduction of AF burden, a higher reduction of hospitalization number and a greater improvement of quality of life. CONCLUSION: Dual defibrillator improved quality of life and decreased resource utilization in patients with drug refractory AF. Early delivering of atrial shock seems to be the most effective option.

Aged↗
PubMed2005

Automatic external defibrillators--time for a change?

Defibrillation is the definitive treatment for cardiac arrest. Until relatively recently the use of defibrillators was restricted to medical staff and paramedics. The development of automatic external defibrillators (AEDs) now means that this life-saving equipment may be used by anyone with a short period of training. This article will review the patho-physiology of cardiac arrest, the use of AEDs and their significance to the dental team. A medical emergency could happen at any time in the dental practice. Cardiac arrest is the most serious emergency that can occur. Whilst life-threatening incidents are very rare, the dental team requires to be trained in the management of a cardiac arrest.

Cardiopulmonary Resuscitation↗
PubMed2001

Prospective randomized comparison of 50%/50% versus 65%/65% tilt biphasic waveform on defibrillation in humans.

It is unknown if there is a single optimal biphasic waveform for defibrillation. Biphasic waveform tilt may be an important determinant of defibrillation efficacy. The purpose of this study was to compare acute defibrillation success with a three-electrode configuration in humans using 50%/50% versus 65%/65% tilt truncated exponential, biphasic waveforms delivered through a 110-microF capacitor. Acute DFTs for biphasic waveforms with 50%/50% versus 65%/65% tilt were measured in random order in 60 patients using a binary search method. The electrode configuration consisted of a RV coil as the cathode, and a SVC coil plus a pectoral active can emulator (CAN) as the anode. The waveforms were derived from an external voltage source with 110-microF capacitance, and the leading edge voltage of phase 2 was equal to the trailing edge voltage of phase 1. Stored energy DFT (9.2 +/- 5.7 [50%/50%] vs 10.8 +/- 6.4 [65%/65%] J, P = 0.007), current DFT (10.9 +/- 4.0 [50%/50%] vs 12.0 +/- 4.4 [65%/65%] A, P = 0.002) and voltage DFT (391 +/- 118 [50%/50%] vs 424 +/- 128 [65%/65%] V, P = 0.004) were significantly lower for the 50%/50% tilt waveform versus the 65%/65% tilt waveform using this three-electrode configuration and a 110-microF capacitor. For an RV(-)/SVC plus CAN(+) electrode configuration and a 110-microF capacitor, a 50%/50% tilt biphasic waveform results in a 15% reduction in energy DFT, 9% reduction in current DFT, and 8% reduction in voltage DFT versus a 65%/65% tilt biphasic waveform.

Aged↗
PubMed2001

Implantation of a dual chamber pacing and sensing single pass defibrillation lead.

Dual-chamber ICDs are increasingly used to avoid inappropriate shocks due to supraventricular tachycardias. Additionally, many ICD patients will probably benefit from dual chamber pacing. The purpose of this pilot study was to evaluate the intraoperative performance and short-term follow-up of an innovative single pass right ventricular defibrillation lead capable of bipolar sensing and pacing in the right atrium and ventricle. Implantation of this single pass right ventricular defibrillation lead was successful in all 13 patients (age 63 +/- 8 years; LVEF 0.44 +/- 0.16; New York Heart Association [NYHA] 2.4 +/- 0.4, previous open heart surgery in all patients). The operation time was 79 +/- 29 minutes, the fluoroscopy time 4.7 +/- 3.1 minutes. No perioperative complications occurred. The intraoperative atrial sensing was 1.7 +/- 0.5 mV, the atrial pacing threshold product was 0.20 +/- 0.14 V/ms (range 0.03-0.50 V/ms). The defibrillation threshold was 8.8 +/- 2.7 J. At prehospital discharge and at 1-month and 3-month follow-up, atrial sensing was 1.9 +/- 0.9, 2.1 +/- 0.5, and 2.7 +/- 0.6 mV, respectively, (P = NS, P < 0.05, P < 0.05 to implant, respectively), the mean atrial threshold product 0.79, 1.65, and 1.29 V/ms, respectively. In two patients, an intermittent exit block occurred in different body postures. All spontaneous and induced ventricular arrhythmias were detected and terminated appropriately. Thus, in a highly selected patient group, atrial and ventricular sensing and pacing with a single lead is possible under consideration of an atrial pacing dysfunction in 17% of patients.

Aged↗
PubMed2001

Waveform optimization for internal atrial defibrillation: effects of waveform rounding, phase duration, and voltage swing.

The aim of this study was to compare the efficacy of internal atrial defibrillation by conventional truncated exponential biphasic waveforms with and without waveform rounding (1-2 phases) and to determine optimal duration for this novel double rounded waveform. Atrial fibrillation, induced by rapid electrical stimulation, was converted by internal shocks through defibrillation catheters (lateral right atrium and coronary sinus) in anesthetised sheep. Rounding the leading edges of the conventional biphasic waveform (Ventritex HVS-02; settings 100/-50 V, 150/-70 V, and 200/-100 V; n = 8) reduced delivered peak and trough voltages, currents, and energy (by > or = 21 %, P < 0.001; for double (both phases) rounded) without decreasing cardioversion success. At 100/-50 V the efficacy of single (first phase) rounded (53 +/- 13%; mean +/- SEM) and double rounded (59 +/- 11%) shocks was similar to the conventional waveform (56 +/- 14%). Double rounded waveform (phase durations 1-20 ms) efficacy was optimum at 6-10 ms phase duration (100% success at 10-ms phase duration; 1.52 +/- 0.04 J delivered energy; n = 6). Successful cardioversion by conventional, single rounded, and double rounded biphasic waveforms (duration 6 ms each phase), conventional monophasic, rounded monophasic (duration 12 ms), and a damped sine waveform correlated strongly with peak-to-trough voltage swing within the waveform (r = 0.882; P < 0.01; n = 8). For internal atrial defibrillation, rounding both phases of the conventional biphasic waveforms, the double rounded waveform, permits similar efficacy to the conventional truncated exponential biphasic waveform at reduced peak voltage, current, and delivered energy. Optimum phase duration is 6-10 ms (tested range 1-20 ms).

Animals↗
PubMed2001

Minimally invasive cardioverter defibrillator implantation for children: an animal model and pediatric case report.

The smaller venous capacitance in infants and small children may hamper transvenous ICD lead implantation, and epicardial approaches require thoracotomy and have associated complications. The study evaluated the feasibility and performance of subcutaneous arrays and active can ICDs without transvenous shocking coils or epicardial patches. An immature and mature pig were anesthetized and ventilated. A pacing lead was inserted in the right ventricle for fibrillation induction and rate sensing. Subcutaneous arrays were positioned in the right and left chest walls. An ICD emulator was placed in abdominal and prepectoral pockets. Fluoroscopic images were acquired for each electrical vector configuration (array --> can, can --> array, array --> array, array + array --> can). Ventricular fibrillation was induced and DFT testing performed. Defibrillation was achieved in all ten trials in the immature piglet, with DFT < or = 9 J, regardless of vector configuration. Using a single subcutaneous array and active can, the shock impedance ranged from 28-36 ohms. With two arrays, shocking impedance fell to 15-22 ohms. In the adult pig, defibrillation was not accomplished with maximum energy of 40 J, using all vector configurations. Using data garnered from these experiments, this technique was then successfully performed in a 2-year-old child with VT and repaired congenital heart disease, needing an ICD. This study demonstrates the feasibility of leadless ICD implantation in an immature animal and successful implementation in a small child. A single subcutaneous array and active can resulted in excellent implant characteristics and DFTs with a minimally invasive approach. Defibrillation was not possible in a larger animal, possibly due to maximal available energy. This may be of value for small children requiring ICD implantation.

Animals↗
PubMed2002

Effect of coexisting cardiovascular disease on the long-term efficacy and safety of the implantable atrial defibrillator.

The long-term efficacy and safety of implantable atrial defibrillator (IAD) therapy in patients with AF and cardiovascular disease is unclear. The aim of this study was to evaluate the efficacy and safety of IAD therapy in patients with and without coexisting cardiovascular disease. In 115 patients implanted with an IAD, 85 patients had cardiovascular disease: 41 (48%) patients had 1 cardiovascular abnormality, 29 (35%) patients had 2, 13 (15%) patients had 3, and 2 (2%) patients had 4 different cardiovascular abnormalities. The device was programmed into a rhythm monitoring mode for the first 3-month postimplant period. All defibrillation therapy was performed under physician supervision to monitor safety and efficacy. After this initial monitoring period, patients were allowed to activate their device away from the hospital or clinic. A total of 357 spontaneous AF episodes occurred in 83 (72%) patients during observed operation and the mean shock efficacy was 93.5+/-20.3% (lower 95% confidence interval [CI] 89.8%). As of the lastfollow-up, 58 (55%) patients had transition to receive nonphysician observed therapy. Forty-two (72%) patients had experienced 332 episodes of AF for which theyhad received device therapy away from the hospital/clinic (mean shock efficacy 90.5+/-39.7%). The presence of hypertension, valvular heart disease, and ischemic heart disease did not affect the shock efficacy of the IAD during physician observed and nonobserved therapy (P > 0.05). However, the presence of congestive heart failure was associated with a lower clinical efficacy during observed and nonobserved therapy (P < 0.05). Overall, 5,262 shocks have been delivered with the IAD without any episode of proarrhythmia. The observed proarrhythmic risk was 0%, with an estimated maximum proarrhythmic risk of 0.06% per shock (95% upper CI). A stand-alone IAD appears to be safe in the presence of cardiovascular disease. The lower clinical efficacy for AF associated with congestive heart failure might be related to a higher rate of early reinitiation of AF after defibrillation.

Adult↗
PubMed2003

Rapid atrial pacing does not decrease the atrial defibrillation threshold.

The aim of the study was to evaluate the effect of preshock atrial pacing on the atrial defibrillation threshold (DFT) during internal cardioversion of AF. The implantable atrial defibrillator has been added to the therapeutic options for patients with recurrent episodes of persistent AF. Although the device is efficient in restoring sinus rhythm, patient discomfort is a limitation. Methods that lower the ADFT are needed. Eleven patients with AF underwent internal cardioversion. In a randomized, crossover design, ADFT testing was performed, applying a step-up protocol starting at 100 V. Rapid atrial pacing was performed with a right atrial catheter for 20 seconds at 90% of the average cycle length of the fibrillatory waves and was immediately followed by a biphasic defibrillation shock. At each energy level, pacing + shock was compared to shock only, until the level at which sinus rhythm was restored by both modes. The step-up protocol was thereafter repeated using the inverse sequence of the two modes. A total of 19 ADFTs were obtained. For 10 the ADFT was lower with pacing + shock, in 4 equal and in 5 higher, than with shock only. The ADFT (mean +/- SD) with pacing + shock was 260 +/- 84 V(3.4 +/- 2.9 J) and did not differ from shock only: 268 +/- 85 V(3.8 +/- 3.0 J) (P > 0.05). The coefficient of variation and the coefficient of reproducibility for pacing + shock was 16% and 60 V, respectively, and for shock only 17% and 61 V. Rapid atrial pacing did not influence the internal ADFT in AF. The randomized, crossover protocol used was reproducible between different modes, and seems useful when testing the impact of different interventions on the ADFT.

Atrial Fibrillation↗
PubMed2002

Temporal patterns of atrial arrhythmia recurrences in patients with implantable defibrillators: implications for assessing antiarrhythmic therapies.

INTRODUCTION: The statistical measures commonly used to assess therapies for recurrent atrial arrhythmias (such as time to first recurrence) often assume a uniformly random pattern of arrhythmic events over time. However, the true temporal pattern of atrial arrhythmia recurrences is unknown. The aim of this study was to use linear and nonlinear analyses to characterize the temporal pattern of atrial arrhythmia recurrences in patients with implantable cardioverter defibrillators. METHODS AND RESULTS: The time and date of atrial tachyarrhythmias recorded in 65 patients with combined atrial and ventricular defibrillators were used to construct a probability density function (PDF) and a model of a Poisson distribution of arrhythmic events for each patient. Average patient age was 66 +/- 10 years and follow-up was 7.8 +/- 4.8 months. A total of 10,759 episodes of atrial tachyarrhythmias were analyzed (range 43 to 618 episodes per patient). The PDF fit a power law distribution for all 65 patients, with an average r2 = 0.89 +/- 0.08. The PDF distribution differed significantly from the model Poisson distribution in 47 of 65 patients (P = 0.0002). Differences from the Poisson distribution were noted for patients both taking (30/43 patients; P < or = 0.015) and not taking (17/22 patients; P < or = 0.017) antiarrhythmic drugs. Median time between atrial arrhythmia detections for all 65 patients was 10.8 minutes. CONCLUSION: In implantable cardioverter defibrillator patients, the temporal pattern of frequent recurrences of atrial tachyarrhythmias usually is characterized by a power law distribution. The unique statistical properties of this type of distribution should be considered in designing outcome measures for treatment of atrial tachyarrhythmias.

Adult↗
PubMed2002

Determinants of first-shock success for atrial implantable cardioverter defibrillators.

INTRODUCTION: The aim of this study was to identify determinants of first-shock success for defibrillation of spontaneous atrial fibrillation (AF) in ambulatory patients with an atrial implantable cardioverter defibrillator (ICD). The determinants of first-shock success in ambulatory patients with atrial ICDs are unknown. METHODS AND RESULTS: We used the generalized estimating equation method to analyze determinants of first-shock success in 50 consecutive atrial ICD recipients in whom DFT+ (weakest shock that defibrillates on two consecutive trials) was determined at implant and spontaneous AF was shocked with shock strength > or = 2 x DFT+. DFT+ was 6.2 +/- 3.1 J. Of 470 first shocks, 407 were successful (generalized estimating equation 85%, confidence interval 79% to 90%). Determinants of first-shock success were use of coronary sinus electrode (univariate P = 0.02; multivariate P < 0.001, relative risk 5.0), absence of a Class III antiarrhythmic drug (univariate P = 0.06; multivariate P < 0.001, relative risk 3.2), absence of early recurrence of atrial fibrillation (ERAF; univariate P = 0.06; multivariate P = 0.02, relative risk 2.9), and longer duration of AF prior to shock > or = 3 hours (univariate: P = 0.02; multivariate P = NS). Sinus rhythm >1 minute persisted after 93% of first shocks in patients without documented ERAF but after only 58% of shocks in patients with documented ERAF (P < 0.001). CONCLUSION: Reducing ERAF is critical to achieving a clinically acceptable rate of persistent sinus rhythm after first shocks. For first shocks > or = 2 x DFT +, success is not increased by programming stronger shocks. Early cardioversion does not increase first-shock success.

Ambulatory Care↗
PubMed2003

Automated external defibrillator arrhythmia detection in a model of cardiac arrest due to commotio cordis.

INTRODUCTION: Cardiac arrest due to chest wall blows (commotio cordis) has been reported with increasing frequency in children, and only about 15% of victims survive. Automated external defibrillators (AEDs) have been shown to be life saving in adults with cardiac arrest, but data on their use in children are limited. In a swine model of commotio cordis designed to be most relevant to young children, we assessed the efficacy of a commercially available AED for recognition and termination of ventricular fibrillation. METHODS AND RESULTS: Ventricular fibrillation was produced in anesthetized juvenile swine by precordial impact from a baseball under controlled conditions. Animals were randomized to defibrillation after 1, 2, 4, or 6 minutes of ventricular fibrillation. Twenty-six swine underwent 50 ventricular fibrillation inductions. Sensitivity of the AED for recognition of ventricular fibrillation was 98%, and specificity for nonshockable episodes was 100%. All episodes of ventricular fibrillation were successfully terminated by the AED. CONCLUSION: In this experimental model of commotio cordis, the AED proved to be highly sensitive and specific for recognition of ventricular fibrillation and effective in terminating the arrhythmia and restoring sinus rhythm. These findings suggest that early defibrillation with the AED could save young lives on the athletic field.

Animals↗
PubMed2004

Two hearts and one defibrillator.

A patient who had undergone heterotopic heart transplantation and placement of an implantable cardioverter defibrillator in his native heart underwent generator change. Defibrillation testing induced ventricular fibrillation in his donor heart. To prevent this potentially lethal complication, defibrillator shock therapy must be synchronized to the donor heart R wave.

Aged↗
PubMed2000

Detection of ventricular fibrillation in implantable defibrillators with automatic gain control amplifiers: effects of programming sensitivity.

AIMS: In newer implantable cardioverter-defibrillators with automatic gain control amplifiers the maximum possible sensitivity is programmed with the aim of securing optimal detection of ventricular fibrillation. This study was designed to prove that a reduction in maximum sensitivity is safe with respect to appropriate sensing of ventricular fibrillation, while avoiding sensing of extracardiac signals. METHODS AND RESULTS: Forty-two consecutive patients, undergoing defibrillator implantation/replacement with programmable maximum auto-gain sensing sensitivity (Ventak Mini III, Ventak AV , Guidant, St. Paul, MN, U.S.A.), were prospectively investigated. Thirty-four patients were implanted with a dual-coil lead system, providing integrated bipolar sensing (Endotak, Guidant, St. Paul, MN, U.S.A.), eight patients received a single-coil lead system with true bipolar sensing (Sprint, Medtronic, Minneapolis, MN, U.S.A.). During device implantation and pre-discharge testing, arrhythmia detection times of induced ventricular fibrillation were compared at programmed maximum (0.18 mV) and minimum (0.43 mV) sensitivity in a randomized manner. Seventy-six induced episodes of ventricular fibrillation were analysed. The mean arrhythmia detection times did not differ between the programmed sensing levels (maximum sensitivity: 1612 +/- 307 ms, vs minimal sensitivity: 1,602 +/- 330 ms; P = ns). The results were not affected by the type of implanted lead system (integrated bipolar versus true bipolar sensing). CONCLUSION: In the implantable defibrillator devices, reduction in maximum sensitivity did not impair the detection of induced episodes of ventricular fibrillation.

Amplifiers, Electronic↗
PubMed2001

[Daily activities and circadian variation of ventricular tachyarrhythmias in patients with implanted defibrillator].

BACKGROUND AND STUDY AIM: Acute cardiovascular events may be triggered by physical and mental stress. Does also the typical circadian variation of arrhythmia recurrence (morning peak of events) in patients with implanted cardioverter-defibrillator correlate with the individual circadian variation of physical and mental daily activities? PATIENTS AND METHODS: In 29 consecutive patients with a minimum of three documented ventricular tachyarrhythmias after defibrillator implantation the circadian variation of habitual daily activities was determined in a standardized interview and compared to the individual circadian variation of arrhythmic events saved in the defibrillator event memory during long-term follow-up. RESULTS: The habitually highest physical and mental activity was determined during the time period with most arrhythmic events in 55 % and 23 % of patients, respectively. A comparison of the level of activity during the time period with the highest event frequency to the mean activity level during the rest of the day (without sleeping time) revealed significantly higher physical activity during the time of day with the highest arrhythmia recurrence. There was a positive correlation between circadian variation of arrhythmic events and the sum of all activities (r = 0.34, p < 0.05) and physical activities alone (r = 0.25, p = 0.056) while a relationship to mental activities alone could not be shown (r = 0.02, p = 0.84) CONCLUSION: The circadian variation of acute cardiovascular events may be discussed as an essential factor influencing the circadian variation of habitual daily activities in patients with cardiac disease.

Activities of Daily Living↗