Alan D. Bernstein

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.

Pacemaker-implantation complication rates: an analysis of some contributing factors

An examination of 632 consecutive pacemaker implantations performed at a single institution by 29 implanting physicians over a 5 year period was made to determine which factors affected the 37 perioperative complications experienced. The introducer method of vein access contributed significantly to the complication rate, which was also related to the number of physician implanters on the staff and the makeup of the implantation teams. Of greatest interest was the substantially large incidence of complications experienced by implanters who performed fewer than 12 implantations per year, and particularly the incidence of lead-related complications.

The NASPE*/BPEG** Generic Pacemaker Code for Antibradyarrhythmia and Adaptive‐Rate Pacing and Antitachyarrhythmia Devices

A new generic pacemaker code, derived from and compatible with the Revised ICHD Code, was proposed jointly by the North American Society of Pacing and Electrophysiology (NASPE) Mode Code Committee and the British Pacing and Electrophysiology Croup (BPEC), and has been adopted by the NASPE Board of Trustees. It is abbreviated as the NBC (for “NASPE/BPEC Generic”) Code, and was developed to permit extension of the generic‐code concept to pacemakers whose escape rate is continuously controlled by monitoring some physiologic variable, rather than determined by fixed escape intervals measured from stimuli or sensed depolarizations, and to antitachyarrhythmia devices including cardioverters and defibrillators. The NASPE/BPEC Code incorporates an “R” in the fourth position to signify rate modulation (adaptive‐rate pacing), and one of four letters in the fifth position to indicate the presence of antitachyarrhythmia‐pacing capability or of cardioversion or defibrillation functions.

Patients' Attitudes Toward Implanted Defibrillator Shocks

In addition to its beneficial effect on patient survival, the implanted cardioverter defibriliator (ICD) changes a patients 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 life saving, 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.

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.

Extraction of implanted transvenous pacing leads: a review of a persistent clinical problem.

Within a few months of implantation, permanent pacemaker leads become ensheathed in fibrocollagenous tissue. This tissue may anchor the lead so that it is difficult, dangerous, or impossible to remove it. Leads with bulbous or finned tips are particularly resistant to extraction. The risks of applying traction to an entrapped lead include induction of bradycardia or ventricular tachycardia and fibrillation, invagination of the right ventricle, avulsion of the right ventricular myocardium or tricuspid valve, hemopericardium, and cardiac tamponade. Forceful traction may result in uncoiling of the conductor, disruption of the insulation, or complete fracture, leaving an intravascular remnant that may embolize or be a source for thrombosis. Although fixation and abandonment of an inactive chronically implanted lead is frequently appropriate and is known to pose little long-term risk, the retained inactive lead may interact adversely with a new active lead and then increase the risk of venous thrombosis, serve as a potential nidus for infection, or produce spurious electrical sensing signals that may be sensed by the pulse generator. Absolute indications for lead removal are those in which there would be a life-threatening situation if the lead were to remain in situ. In the absence of an absolute indication, the decision to proceed with extraction must be made by weighing the potential for serious morbidity or mortality against risks of the extraction technique. Techniques for lead removal include traction and open cardiotomy operations. When a portion of the lead is intravascular, forceps, snares, baskets, countertraction, or lead-transection devices may be used to retrieve the fragment.

Survey of Cardiac Pacing and Implanted Defibrillator Practice Patterns in the United States in 1997

Bernstein, A.D., et al.: 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.

Clinical usefulness of risk-stratified outcome analysis in cardiac surgery in New Jersey

BACKGROUND The results of aortocoronary bypass grafting are under increasing scrutiny by the Health Care Financing Agency, health maintenance organizations, and the news media. Surgeons and hospital administrators are concerned that erroneous conclusions may be drawn from raw outcome data, which do not reflect the patients preoperative condition. It is our contention that any realistic comparison of results among surgeons or institutions must take that condition into account through a process of risk management. METHODS We have developed a statistical model for risk stratification based on data compiled systematically at the Newark Beth Israel Medical Center since 1980. Univariate analysis and stepwise logistic regression are used to identify the most significant risk factors and determine the appropriate weight for each. Our original risk stratification system has now been updated by eliminating the optional fields and reweighting the variables. This has reduced the subjective input and improved the accuracy. RESULTS Use of the modified system shows good correlation between expected and observed outcomes at our institution and in other cases reported to the New Jersey Department of Health. It has improved the results especially in high-risk cases: in total, a group of 5,336 patients have been assessed by the modified system: the expected mortality overall was 7.2% and the observed mortality was 5.4%. In 1,280 high-risk patients, ie, those with an expected mortality of greater than 11%, the expected mortality was 16.2% and the observed mortality was 12.3%. CONCLUSIONS Our results suggest a decline in length of hospital stay and beneficial changes in operative procedures. They also indicate that exclusion of high-risk cases will result in only minimal financial savings, perhaps less than 2%.

The NASPE /BPEG Defibrillator Code

A new generic code, patterned after and compatible with the NASPE/BPEG Generic Pacemaker Code (NBG Code) was adopted by the NASPE Board of Trustees on January 23. 1993. It was developed by the NASPE Mode Code Committee, including members of the North American Society of Pacing and Electrophysiology (NASPE) and the British Pacing and Electrophysiology Croup (BPEC). It is abbreviated as the NBD (for NASPE/BPEC Defibrillator) Code. It is intended for describing the capabilities and operation of implanted cardioverter defibrillators (ICDs) in conversation, record keeping, and device labeling, and incorporates four positions designating: (1) shock location; (2) antitachycardia pacing location; (3) means of tachycardia detection; and (4) antibradycardia pacing location. An additional Short Form, intended only for use in conversation, was defined as a concise means of distinguishing devices capable of shock alone, shock plus antibradycardia pacing, and shock plus antitachycardia and antibradycardia pacing.

Cardiac Pacing in the 1980s: Treatment and Techniques in Transition

The pacemaker of the 1980s is designed to maintain atrioventricular synchrony through dual-chamber pacing. This pacemaker is multiprogrammable and capable of telemetric transmission of biologic, electronic and electrophysiologic data. Several developments have made this therapeutic modality possible: 1) the cumulative survival rate of many lithium-battery pacemakers exceeds 95% at 5 years; 2) lead and connector problems are rare; 3) atrial and ventricular electrode malfunctions occur in less than 2% of implants; and 4) new introducer techniques have simplified implantation (mortality and major morbidity rates are 0.5 and 0.4%, respectively). With multiprogrammability, pacemaker function can be optimized for the patients needs, and about 20% of reoperations can be avoided. Ninety-six dual-chamber (DDD) pacemakers, 55 of which have been followed up for more than 3 months, have provided trouble-free performance and have yielded salutary clinical results, particularly when implanted to replace previous ventricular inhibited units. Problems with these pacemakers have included unusual pacing electrocardiograms, pacemaker eccentricities, programmer maintenance, pacing and follow-up complexities and costs. In the 1980s, effort will be required to find a balance between rapidly evolving technology and the clinical need for complex pacing systems. From 1978 to 1981, the rate of pacemaker implantation grew from 309 to 513 implants per million population per year, and there are now approximately 500,000 patients with implanted pacemakers living in the United States. Indications for pacing are ill-defined, because in many cases the assessment of clinical response to pacing is largely subjective, lacking satisfactory quantitative indexes. This decade will be a time of reappraisal of the extent of clinical applicability of new techniques, particularly the multiprogrammable dual-chamber system which, after 3 years of clinical trial, shows promise of being the predominant pacemaker of the immediate future.