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Biomedical subjects

M Roelke

Publications and source records attributed to M Roelke.

At least 19 recordsLinked to original sources
PubMed2001

Laser extraction of entrapped leads.

Removing entrapped pacing and defibrillator leads has been greatly simplified by making use of the excimer laser extractor. Sixty-two leads were successfully removed, although where appropriate, portions of the lead remained in place in 10 cases. There were two serious complications, one tear of the superior vena cava during an ICD extraction and one tear of the atrium during an atrial lead extraction. Both were controlled successfully through emergency sternotomy. Although extracting entrapped leads has been much simplified by making use of the laser extractor, the process is not free of serious complications. Those involved in explanting leads should be aware of the outcomes and be prepared for emergent management.

Device Removal↗
PubMed2000

Serial lead impedance measurements confirm fixation of helical screw electrodes during pacemaker implantation.

The purpose of this study was to determine whether serial measurements of helical screw pacemaker lead impedance could reliably confirm electrode fixation in the right atrium and right ventricle. Fixation is generally assessed fluoroscopically, which can be misleading because the myocardium is radiolucent. Alternatively, because the electrical conductivity of blood is greater than that of myocardium, serial measurements of the lead impedance might be expected to show an impedance increase with appropriate fixation of the pacemaker electrode when the electrode becomes embedded in myocardial tissue. Impedance measurements were made during the placement of 23 atrial and 28 ventricular active fixation electrodes in 31 consecutive patients. Impedance measurements were recorded in unipolar and bipolar electrode configurations with the electrode free floating in the chamber, unfixed (with exposed screws) but touching the endocardial surface, and after fixation. No significant impedance differences were found between free-floating and unfixed electrode positions. With fixation, the lead impedance increased significantly in the ventricle (P = 0.0001, unipolar and bipolar) and the atrium (P = 0.0069 unipolar and 0.0052 bipolar). Typical increases, reflected by median values, were 197 ohms unipolar and 203 ohms bipolar in the ventricle and 47 ohms unipolar and 53 ohms bipolar in the atrium for electrodes with permanently exposed or retractable screw designs. Comparing serial measurements of lead impedance before and after electrode fixation is a valid electrical method of confirming appropriate fixation of helical screw electrodes.

Aged↗
PubMed2000

Patients' attitudes toward implanted defibrillator shocks.

In addition to its beneficial effect on patient survival, the implanted cardioverter defibrillator (ICD) changes a patient's life physically, socially, and psychologically. For improved patient management, it is important to understand the quality-of-life changes that accompany this mode of treatment. To this end, 119 patients were surveyed retrospectively and interviewed concurrently regarding their emotional, physical, and behavioral responses to ICD shocks and to the device itself. Most (55%) correctly estimated the total number of shocks they had received within a 10% margin. They found the shocks severe, 79% assigning a score between 3 and 5 on a scale of 1-5. Common descriptions of the shock sensation were a blow to the body or a spasm causing the entire body to jump. Most patients tolerated the shocks as lifesaving, but 23% dreaded shocks and 5% even said they would rather be without the ICD and take their chances. After a shock, 50% of patients called their physician and 42% continued their daily routine. Thirty percent went to a hospital emergency room or called a rescue service. Sixty-five percent had no preshock prodromes. Fifty-four percent were interested in the programmable option of a warning signal prior to a shock, while 31% preferred no warning. Of the 74% who were advised not to drive after implantation, 29% drove anyway. Five patients were shocked while driving with no resulting accidents. We conclude that most patients find ICD shocks moderately uncomfortable, but they tolerate them because of the lifesaving protection provided by the device.

Adult↗
PubMed2000

Reduced frequency of retention wire fractures suggests that elective explantation of affected atrial leads is no longer indicated.

Since 1994, 611 patients with atrial Accufix leads have been followed. Consideration was given to explanting these leads based on the presence or absence of fractures of the retention wire. All leads were followed according to a protocol proposed by the manufacturer, chiefly by regular 6-month high quality X rays and fluoroscopic evaluation. The impact of various conditions on the incidence of fracture was evaluated, such as the shape and location of the lead, prior open heart surgery, and the implantation route. The only factor related to the frequency of fractures was the shape of the lead, fractures occurring statistically more frequently if the leads were pulled from their normal J shape into an L or straightened configuration. The frequency of fractures has plateaued at 6 through 9 years with no further occurrence of Class III or IV fractures (protrusion of the fractured segment). Altogether there were nine (1.5%) Class III and Class IV fractures at the 9-year follow-up. Actuarial survival, in Class I or II, was 97%. We concluded, that the frequency of retention wire fractures has plateaued. This information coupled with the knowledge that the Accufix lead extraction can be difficult and dangerous, suggests that the remaining leads are best left in place.

Adolescent↗
PubMed1999

Pacemaker interference with screening mammography.

In female pacemaker recipients undergoing screening mammography, the impact of a pulse generator placed in the pectoral region has yet to be reviewed. We evaluated mammograms from 74 female pacemaker patients aged 40 years and older. The pulse generator obscured a portion of the mammogram in 7 patients (12%). During pacemaker implantation in women, the potential for the pulse generator to interfere with screening mammography should be considered. Baseline mammography should be obtained or reviewed; in high risk patients a nonconventional location for the pulse generator may be appropriate.

Adult↗
PubMed1998

Transvenous single lead atrial defibrillation: efficacy and risk of ventricular fibrillation in an ischemic canine model.

Transvenous atrial defibrillation with multiple atrial lead systems has been shown to be effective in models without the potential for ventricular arrhythmias. The specific aim of this study was to evaluate the efficacy and safety of transvenous single lead atrial defibrillation in a canine model of ischemic cardiomyopathy. Ten dogs had ischemic cardiomyopathy induced by repeated intracoronary microsphere injections. The mean LV ejection fraction decreased from 71% +/- 9% to 38% +/- 14% (P = 0.003). Spontaneous atrial fibrillation (AF) developed in four dogs, and in six AF was induced electrically. Atrial defibrillation thresholds (ADFTs) were determined with synchronous low energy shocks using a transvenous tripolar lead with two defibrillation coils (right ventricle, superior vena cava) and an integrated sensing lead (RV coil vs electrode tip). The ADFTs derived by logistic regression were compared at 50% and 90% probability of success (ED50, ED90): ED50 was 2.4 +/- 1.7 J and 2.9 +/- 2.1 J, respectively, for 5- and 10-ms monophasic shocks, and 1.8 +/- 0.9 J, respectively, for 5- and 10-ms biphasic shocks. Immediately after 3 of 2,179 (0.1%) synchronized shocks, ventricular fibrillation (VF) developed. VF was induced in 3 of 1,062 (0.3%) shocks with integrated sensing (RV coil vs electrode tip) compared to 0 of 1,117 shocks when a separate bipolar RV sensing electrode was used for synchronization. In our canine model of ischemic cardiomyopathy, low energy atrial defibrillation via a transvenous single lead system was highly effective. However, there was a small but definite risk of VF induction, which seemed to be greater when an integrated as opposed to a true bipolar RV sensing was used.

Animals↗
PubMed1997

The treatment of patients with infected implantable cardioverter-defibrillator systems.

OBJECTIVE: The purpose of this study was to evaluate the treatment of patients with infected implantable cardioverter-defibrillator systems. METHODS: Retrospective analysis was done of the cases of 21 patients treated for implantable cardioverter-defibrillator infection during an 11-year period. RESULTS: Of 723 cardioverter-defibrillator implantations (550 primary implants, 173 replacements), nine (1.2%) were complicated by early postoperative device-related infections. Late infections developed in two patients 19 and 22 months, respectively, after implantation. Ten other patients were transferred to our institution for treatment of cardioverter-defibrillator infection. The time from implantation to overt infection was 2.2 +/- 1.3 months, excluding the two late infections. The responsible organisms were Staphylococcus aureus (9), Staphylococcus epidermidis (6), Streptococcus hemolyticus (1), gram-negative bacteria (3), Candida albicans (1), and Corynebacterium (1). All patients were treated with intravenous antibiotic drugs. Total system removal was done in 15 patients and partial removal in 2; in 4, the cardioverter-defibrillator system was not explanted. There were no perioperative deaths. A new implantable cardioverter-defibrillator system was reimplanted in 7 patients after 2 to 6 weeks of antibiotic therapy. Ten patients were treated without reimplantation (2 arrhythmia operation, 8 antiarrhythmic drugs). Four patients (3 patients without explantation and 1 with partial system removal) were treated with maintenance long-term antibiotic therapy. During a mean follow-up of 21 +/- 2.8 months, no patient had clinical recurrence of infection. One patient treated with antiarrhythmic drugs without system reimplantation died suddenly. CONCLUSIONS: Infections that involve implantable cardioverter-defibrillator systems can be safely managed by removing the entire system with reimplantation after intravenous antibiotic therapy. In selected patients in whom the risk for system explantation is high and anticipated life expectancy is short, long-term antibiotic therapy to suppress low-virulence infections may represent an acceptable alternative.

Adult↗
PubMed1996

Inhibition of bradycardia pacing caused by far-field atrial sensing in a third-generation cardioverter defibrillator with an automatic gain feature.

The diagnostic accuracy of implantable cardioverter defibrillators may be improved by automatically adjusting gain algorithms, which in general reduce the likelihood of oversensing while maintaining the ability to detect the low amplitude signals associated with ventricular fibrillation. We present a patient with a third-generation device who developed prolonged ventricular asystole arising as a complication of the automatic gain feature. During asystole the device automatically increased sensitivity in order to prevent undersensing of ventricular fibrillation, which in this case resulted in far-field sensing of atrial activity and inhibition of ventricular pacing.

Aged↗
PubMed1995

Limitations and late complications of third-generation automatic cardioverter-defibrillators.

BACKGROUND: This study examines the limitations and complex management problems associated with the use of tiered-therapy, implantable cardioverter-defibrillators (ICDs). METHODS AND RESULTS: The study group comprises the first 154 patients undergoing implantation of tiered-therapy ICDs at our institution. Pulse generators from three different manufacturers were used. In 39 patients, a complete nonthoracotomy lead system was used. The perioperative mortality was 1.3%. Of these 154 patients, 37% experienced late postoperative problems. Twenty-one patients required system revision within 36.5 months (mean, 8.57 +/- 11.3) of surgery. Reasons for revision were spurious shocks due to electrode fractures (3) or electrode adapter malfunction (2), inadequate signal from endocardial rate-sensing electrodes (3), superior vena cava or right ventricular coil migration (5), failure to correct tachyarrhythmias due to a postimplant rise in defibrillation threshold (5), or pulse generator failure (3). One of these patients required system removal for infection after revision of an endocardial lead. A further 32 patients received inappropriate shocks for atrial fibrillation with a rapid ventricular response or sinus tachycardia. Two of these patients also received shocks for ventricular tachycardia initiated by antitachycardia pacing triggered by atrial fibrillation. Ventricular pacing for bradycardia was associated with inappropriate shocks due to excessive autogain in 2 patients. CONCLUSIONS: Despite the major diagnostic and therapeutic advantages of tiered-therapy ICDs, a significant proportion of patients continue to experience hardware-related complications or receive inappropriate shocks.

Algorithms↗