Unexpected ICD pulse generator failure due to electronic circuit damage caused by electrical overstress.

Because it is a lifesaving device, the unexpected failure of an ICD can be catastrophic. We report ICD electronic circuit failure due to electrical overstress damage (EOS) to the high voltage hybird circuit and other electronic components in a series of ICD pulse generator models. Data were obtained from the Multicenter Registry of Pacemaker and ICD Pacemaker and Lead Failures, and from the manufactures' adverse event reports, that were in the FDA's Manufacturer and User Facility Device Experience (MAUDE) database. Of 16 nonbattery Guidant/CPI ICD pulse generator failures reported to the registry, 6 (38%) have been confirmed by the manufacturer to be EOS related, and Guidant/CPI has reported 273 such failures to the FDA as of 12/29/00. The signs of failure included loss of telemetry and inability to deliver therapy, and some patients have experienced serious adverse events. Hybrid circuit damage may have occurred during capacitor charging or reform, and the majority appears to have happened during normal ICD function. While the incidence of this problem is unknown, a management strategy should be adopted that includes routine follow-up every 3 months and device evaluation after a shock or exposure to external defibrillation or electrosurgical devices. This study suggests that additional data are needed to determine the incidence of this problem, and that our present methods for monitoring the performance of ICD's following market release are inadequate.

Survey of cardiac pacing and implanted defibrillator practice patterns in the United States in 1997.

A survey of implanters of permanent cardiac pacemakers and ICDs in the United States during 1997 was conducted to identify present and changing patterns in indications for pacing, implantation techniques, pacing-mode selection, follow-up, and opinions regarding pacing and ICD related issues. This report is an update from 1993 of surveys performed every 4 years for the International Cardiac Pacing and Electrophysiology Society (ICPES). Questionnaires were sent to implanting physicians who were members of the North American Society of Pacing and Electrophysiology (NASPE), and who might, therefore, be expected to be more conversant than others with the state of the art. Four major manufacturers also provided estimates of the numbers of pacemakers and ICDs implanted in the United States from 1994 through 1997. In 1997, approximately 182,000 new rhythm management devices, including 153,000 primary pacing systems and 29,000 ICDs, were implanted, an increase of 24% for pacemakers and 90% for ICDs since 1994. In 1997, pacemaker implantations were performed by about 8,600 physicians working in 3,300 hospitals and 1,000 independent "surgi-centers." From 1994 to 1997, sales in the United States of dual chamber pacemakers rose from 58% to 69% of the total, and adaptive rate systems from 74% to 90%. ICD sales increased by about 29% per year from 18,700 to 35,000 units. This study disclosed significant differences among implanter subcategories and between present and earlier practices, and it provided useful insights into trends in pacemaker and defibrillator practice. Future surveys would be facilitated if a standardized implant registry like that used in Europe were established in the United States.

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.

Feasibility and initial results of an Internet-based pacemaker and ICD pulse generator and lead registry.

The medical community has no independent source of timely information regarding the performance of pacemaker and ICD pulse generators and leads. Accordingly, the authors established an Internet-based registry of pacemaker and ICD pulse generator and lead failures (www.pacerandicregistry.com). During the first year, they found three previously unreported device problems that were promptly communicated to the participants. Of the failures reported, 11% of ICD and 10% of pacemaker pulse generator failures were heralded by signs other than the expected elective replacement indicator (ERI). Average ICD battery longevity was 4.0 +/- 0.7 years, and average dual chamber pacemaker battery longevity was 6.8 +/- 2.6 years. Disrupted insulation accounted for 54% of pacemaker and 29% of ICD lead failures. Compared to pacemaker pulse generator and lead failure, ICD device failures were more likely to cause severe clinical consequences. In conclusion, an Internet-based registry is feasible and capable of providing timely data regarding the signs, causes, and clinical consequences of pacemaker and ICD failures.

Aortic valve replacement in geriatric patients: determinants of in-hospital mortality.

BACKGROUND: Aortic valve replacement is a common procedure in elderly patients. There has been a great deal of controversy about the risks associated with early mortality. Uncertainty of the risk associated with a small valve continues to remain controversial. This study was designed to identify the risk factors influencing early mortality and establish an accurate model for the prediction of in-hospital mortality. METHODS: One hundred eighty septuagenarians and octogenarians (58% women; mean age, 76 +/- 4.7 years) underwent primary isolated aortic valve replacement between 1986 and 1997. There was an overall mortality of 16.7% (n = 180). Patients with a body surface area less than 1.8 m2 had an in-hospital mortality of 23.2% (n = 95) compared with 8.1% (n = 74; p = 0.009) for patients with a body surface area of 1.8 m2 or more. Patients with a cardiopulmonary bypass time of less than 100 minutes experienced an early mortality of 8.9% (n = 56) compared with a 10.2% (n = 59) early mortality for patients on bypass time between 100 and 124 minutes and a 29.6% (n = 64) early mortality in patients with a pump time longer than 124 minutes (p = 0.040). RESULTS: Multivariate logistic regression analysis identified small body surface area and long cardiopulmonary bypass time as independent risk factors. A higher mortality was seen in female patients and patients receiving smaller valves. However, there was a strong correlation between small body surface area, small valve size, and female gender. CONCLUSIONS: Small body surface area and long cardiopulmonary bypass time are two independent risk factors in early mortality for elderly patients undergoing primary isolated aortic valve replacement. The use of small valves does not influence early mortality.

Management of catheter-induced pulmonary artery perforation: a rare complication in cardiovascular operations.

BACKGROUND: Pulmonary artery perforation is a rare but often fatal complication of the pulmonary artery catheter occurring in cardiovascular operations and at catheterization facilities. We used our experience and a review of the literature to formulate diagnostic and management strategies. METHODS: During a 13-year period, 12 patients with pulmonary artery perforations were treated in a center that performed an average of 860 open-heart procedures per year. Clinical presentation varied from minor hemoptysis to major airway hemorrhage, hypoxia, exsanguination, and cardiac arrest. Airway bleeding occurred shortly after weaning from cardiopulmonary bypass in 5 patients or postoperatively after wedging the catheter in 6. One patient developed a hemothorax and had a cardiac arrest. Treatment included assurance of gas exchange, endobronchial lavage, isolation of the bleeding bronchus and control of hemorrhage by conservative therapy, pulmonary resection, pulmonary artery repair, and arterial embolization. RESULTS: Five of the 12 patients died (42%). Recurrent hemorrhage occurred in 40% of patients (2 of 5) treated conservatively compared with none of the patients (0 of 7) having surgical treatment. Forty three percent of patients (3 of 7) treated surgically died; 20% of patients (1 of 5) treated conservatively died. One patient succumbed without treatment. CONCLUSIONS: Pulmonary artery perforation is a rare and often fatal complication of pulmonary artery catheterization. This was apparent with patients who had airway hemorrhages as a result of weaning from cardiopulmonary bypass or after balloon inflation. Recurrent and fatal hemorrhage was frequent in patients treated by conservative therapy alone. Surgical intervention was effective in control of hemorrhage but did not reduce the number of deaths. Treatment remains highly individualized. It is advisable to be cautious in inserting Swan-Ganz catheters and to avoid their use unless absolutely necessary.

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.

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.

Recommendations for extraction of chronically implanted transvenous pacing and defibrillator leads: indications, facilities, training. North American Society of Pacing and Electrophysiology Lead Extraction Conference Faculty.

The procedure of lead removal has recently matured into a definable, teachable art with its own specific tools and techniques. It is now time to recognize and formalize the practice of lead removal according to the current methods of medicine and the health care industry. In addition, since at this time the only prospective scientific study of lead extraction is the PLEXES trial, we suggest that studies relating to the techniques of and indications for lead extraction be designed. Recommendations for a common set of definitions, for a framework of training and reviewing physicians in the art, for general methods of reimbursement, and for consistency among clinical trials have been made. Implementation of these recommendations will require additional effort and cooperation from practicing physicians, medical societies, hospital administrations, and industry.

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.

Bedside estimation of risk as an aid for decision-making in cardiac surgery.

BACKGROUND: Evaluations of the cardiac-surgery mortality rates of hospitals and surgeons can be fair and realistic only when the observed mortality rates are compared with expected rates with preoperative risk factors taken into account. Risk-approximation calculations also can assist patients and physicians in discussing the risk of cardiac surgery, especially if the estimation of surgical mortality takes all of the important risk factors into account. METHODS: A logistic regression model was developed in which 47 potential risk factors were considered, and a method requiring only simple addition and graphic interpretation was designed for approximating the estimated risk easily and quickly, with paper and pencil alone. RESULTS: The estimates provided by the simplified model correlated well with the observed mortality rates. CONCLUSIONS: A simple approximation of a logistic regression model has been found to be helpful in discussions between physicians and patients contemplating aortocoronary bypass or valve-related surgery.

Mannitol, furosemide, and dopamine infusion in postoperative renal failure complicating cardiac surgery.

BACKGROUND: Acute renal failure occurring in the postoperative period, requiring dialysis after cardiac surgery is an important risk factor for an early mortality, and the overall mortality of this complication is as high as 40% to 60%. Dialysis in the early postoperative period is often complicated by acute hemodynamic, metabolic, and hematologic effects that adversely affect cardiopulmonary function in patients stabilizing from recent surgery. The purpose of this study was to avoid the need for dialysis by infusion of the solution of mannitol, furosemide, and dopamine in the early postoperative period in oliguric renal failure. METHODS: One hundred patients with postoperative oliguric or anuric renal failure despite adequate postoperative cardiac output and hemodynamic function were randomized. Forty patients (group A) were given intermittent doses of diuretics (furosemide, bumetadine, and ethracrynic acid) and fluids. Sixty patients (group B) were given continuous infusion of the solution of mannitol, furosemide, and dopamine; the infusion was started within 6 hours (mean 3.5 hours) in subgroup B1 (n = 30), and later than 6 hours (mean 7.5 hours) in subgroup B2 (n = 30) after the onset of renal failure. RESULTS: Diuresis occurred in 93.3% of group B (n = 56) versus 10% in group A (n = 4; patients with preop normal renal function). Ninety percent of group A (n = 36) required dialysis versus only 6.7% of group B (n = 4; patients with preexisting renal disease of subgroup B2). Renal function returned to preoperative normal (serum creatinine 0.9 +/- 0.05, p < 0.0001) or baseline value (serum creatinine 2.5 +/- 0.01, p < 0.0001) after first postoperative week in subgroup B1 and third postoperative week in subgroup B2. CONCLUSIONS: Infusion of solution of mannitol, furosemide, and dopamine promoted diuresis in patients with acute postoperative renal failure with adequate postoperative cardiac output and had decreased the need for dialysis in the majority of patients. Early administration of this solution in acute renal failure caused early restoration of renal function to normal or baseline status. It remains to be determined whether routine administration of this solution in the early postoperative period for oliguric renal failure influences the long-term mortality and morbidity in those patients who do require dialysis.

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.