Kevin J. Ferrick

ACC/AHA guidelines for ambulatory electrocardiography: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Revise the Guidelines for Ambulatory Electrocardiography): Developed in collaboration with the North American Society for Pacing and Electrophysiology

A meter drive circuit includes a signal input circuit through which an input signal is applied to a peak hold circuit for producing an output signal which indicates an instantaneous peak value of the input signal and which is held for a predetermined time, a sample and hold circuit for sampling the level of the output signal of the peak hold circuit, and holding the sampled level, and a signal level indicator connected to the sample and hold circuit to provide an indication of the sampled level.

ACC/AHA guidelines for ambulatory electrocardiography: Executive summary and recommendations: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Revise the Guidelines for Ambulatory Electrocardiography): Developed in Collaboration with the North American Society for Pacing and Electrophysiology

Improvements in solid-state digital technology have enhanced transtelephonic transmission of electrocardiography (ECG) data and increased the accuracy of software-based analysis systems. These advances, in addition to better signal quality and greater computer arrhythmia interpretation capabilities, have opened new potential uses for ambulatory electrocardiography (AECG). Traditional uses of AECG for arrhythmia detection have expanded as the result of increased use of multichannel and telemetered signals. The clinical application of arrhythmia monitoring to assess drug and device efficacy has been further defined by new studies. The analysis of transient ST-segment deviation remains controversial, but considerably more data are now available, especially about the prognostic value of detecting asymptomatic ischemia. Heart rate variability (HRV) analysis has shown promise for predicting mortality rates in cardiac patients at high risk. Despite these advances, a true automated analysis system has not been perfected and technician/physician participation is still essential. The widespread availability and low cost of personal computers and workstations has allowed for the development of extremely sophisticated and automated signal processing algorithms. Current AECG equipment provides for the detection and analysis of arrhythmias and ST-segment deviation as well as more sophisticated analyses of R-R intervals, QRS-T morphology including late potentials, Q-T dispersion, and T-wave alternans. There are 2 categories of AECG recorders: continuous recorders, typically used for 24 to 48 hours to investigate symptoms and ECG events that are likely to occur within that time frame, and intermittent recorders, which may be used for long periods of time (weeks to months) to provide briefer, intermittent recordings for investigating events that occur infrequently. ### A. Continuous Recorders Rapidly evolving technologies now allow for direct recording of the ECG signal in a digital format using solid-state recording devices. The direct digital recording avoids all of the biases introduced by the mechanical features of tape recording devices and the problems associated with …

Benefits of implantable defibrillators are overestimated by sudden death rates and better represented by the total arrhythmic death rate

Benefits of the implantable defibrillator on survival were studied in 56 consecutive patients (concomitant coronary bypass or arrythmia surgery in 15) during an 8 year period between 1982 and 1990. During a follow-up period of 29 +/- 25 months, six patients had a sudden death and eight patients had a nonsudden cardiac death. Nonsudden cardiac deaths included three surgical deaths (death within 30 days after the surgery; two in patients without and one in a patient with concomitant cardiac surgery), one arrhythmia-related nonsudden death (death within 24 h after an arrhythmic event despite initial termination of the arrhythmia by the implantable defibrillators) and four nonarrhythmic cardiac deaths. The actuarial survival rate free of events at 1, 2 and 3 years was 96%, 96% and 92%, respectively, for sudden death, 91%, 91% and 87% for sudden death and surgical mortality and 89%, 89% and 85% for total arrhythmic death (sudden death, surgical mortality and arrhythmia-related nonsudden death). Thus, in patients treated with an implantable defibrillator, 1) the rate of sudden death is low (8% at 3 years); 2) 50% of nonsudden cardiac deaths are causally related to arrhythmia (surgical mortality or arrhythmia-related nonsudden death); 3) the total arrhythmic death rate is substantially higher than the sudden death rate; and 4) benefits of an implantable defibrillator are overestimated by reported sudden death and nonsudden cardiac death rates. The benefits may be better represented by the total arrhythmic death and nonarrhythmic cardiac death rates.

Prevalence of a Brugada Pattern Electrocardiogram in an Urban Population in the United States

Objective: To determine the prevalence of a Brugada‐type pattern on routine electrocardiogram (ECG) in an urban population served by a tertiary medical center in the United States.

Exacerbation of ventricular arrhythmias during the postoperative period after implantation of an automatic defibrillator

The postoperative course of 68 consecutive patients treated with an implantable defibrillator during the period from 1982 through 1990 was studied. In 46 patients (group 1), no concomitant surgery was performed during the implantation. In 22 patients (group 2), concomitant surgery (coronary artery bypass [n = 12], valve replacement [n = 3] or arrhythmia surgery [n = 7]) was performed. All patients in group 1 were clinically stable before surgery, receiving an antiarrhythmic regimen chosen by serial drug testings. The same regimen was continued postoperatively. Eight of the 46 patients in group 1 whose condition had been stable in the hospital for 19 +/- 25 days preoperatively developed multiple episodes of sustained ventricular tachycardia 4 +/- 9 days after implantation while receiving the same antiarrhythmic regimen. Although the exacerbation was transient in some patients, six required different antiarrhythmic therapy and one eventually died. Two additional patients had frequent and prolonged episodes of nonsustained ventricular tachycardia that could trigger the defibrillator, requiring changes in the antiarrhythmic regimen. Another patient had progressive cardiac failure and died on day 5. A marked (sevenfold) increase in asymptomatic ventricular arrhythmias was noted in 42% of the remaining 35 patients. In group 2 (combined surgery), one patient developed refractory ventricular tachycardia 3 days postoperatively and died on that day. Three patients developed frequent nonsustained ventricular tachycardia postoperatively, requiring changes in the antiarrhythmic regimen. The overall surgical mortality rate was 4.4% (4.3% in group 1 and 4.5% in group 2) and was due to refractory ventricular tachycardia in two patients and cardiac failure in one.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-Term outcomes and modes of death of patients treated with nonthoracotomy implantable defibrillators

Long-term outcomes of all patients who underwent nonthoracotomy implantable cardioverter-defibrillator (ICD) implantation at our institution from April 1991 to October 1994 were studied using the intention-to-treat analysis. Of 94 consecutive patients, 81 underwent nonthoracotomy ICD implantation and 13 underwent thoracotomy (for concomitant surgery in 11 and unavailability of nonthoracotomy leads in 2). Six of 81 patients had a high defibrillation threshold, 4 subsequently underwent thoracotomy, and 2 were treated with amiodarone. Surgical mortality was 0%. The duration of follow-up was 20 +/- 13 months, and was > 12 months in 74% of 67 living patients. Actuarial survival rates at 1 and 2 years were, respectively, 98% and 94% for sudden death and 91% and 83% for total mortality. Deaths during long-term follow-up were mostly due to nonsudden cardiac or noncardiac deaths. Two-year mortality rates were 12% and 25% in patients with ejection fraction > or = 30% and < 30%, respectively. Thus, instances of sudden death and surgical mortality are very few in patients with nonthoracotomy ICDs. Deaths during long-term follow-up are mostly due to nonsudden cardiac and noncardiac deaths. Therefore, ICD therapy may have greater impact on survival in patients with lower risks of nonsudden cardiac and cardiac death (e.g., younger patients with minimal heart disease) than in patients with severe cardiac or noncardiac disease. Prospective studies are needed to address this question.

Long-term stability of defibrillation thresholds with intrapericardial defibrillator patches.

From March 1982 to May 1, 1992, 105 consecutive patients underwent initial implant of cardioverter defibrillators (ICD) at our institution. Twenty‐nine patients (23 male and 6 female, average ejection fraction 32.24%) with ICD systems implanted via thoracotomy and either intra‐ or extrapericardial patches, had one or more revisions including 56 generator changes or staged implant procedures, three patch revisions, one patch lead fracture without revision, and one sensing lead revision. The time between pulse generator revisions averaged 19.5 months. Initial defibrillation threshold mean was 12.8 joules (n = 25); at first revision, 14.46 joules (n = 29), (P = NS); by fifth revision, 15.0 joules (n = 2), (P = NS). One patch was noted to be crinkled at 70 months; one patch had migrated by 39 months, and two patch leads had fractured at the costal margin by 69 and 90 months. One patient with marginal defibrillation thresholds had an additional patch placed at revision to an upgraded ICD unit. Once acceptable defibrillation threshold (DFT) is obtained, the long‐term intrapericardial DFT remains stable unless a specific problem occurs. As a small, nonstatistically significant increase in DFT may occur, caution must be exercised in patients with marginal DFTs.

Pacemakers and implantable cardioverter defibrillators: device longevity is more important than smaller size: the patient's viewpoint.

The size of pacemakers and implantable cardioverter defibrillators (ICDs) has been diminishing progressively. If two devices are otherwise identical in components, features and technology, the one with a larger battery should have a longer service life. Therefore, patients who receive smaller devices may require more frequent surgery to replace the devices. It is uncertain whether this tradeoff for smaller size is desired by patients. We surveyed 156 patients to determine whether patients prefer a larger, longer‐lasting device, or a smaller device that is less noticeable but requires more frequent surgery. The effects of subgroups were evaluated; these included body habitus, age, gender, and patients seen at time of pulse generator replacement (PGR), initial implant, or follow‐up. Among 156 patients surveyed, 151 expressed a preference. Of these, 90.1% preferred the larger device and 9.9% the smaller device (P < 0.0001). Among thin patients, 79.5% preferred a larger device. Ninety percent of males and 89.2% of females selected the larger device. Among younger patients (≤72 years), 89.6% preferred the larger device, as did 90.5% of older patients (>72 years). Of patients undergoing PGR or initial implants, 95% favored the larger device, as did 86% of patients presenting for follow‐up. The vast majority of patients prefer a larger device to reduce the number of potential replacement operations. This preference crosses the spectrum of those with a previously implanted device, those undergoing initial implants, those returning for routine follow‐up, and patients of various ages, gender, and habitus.

Initial Experience with Transvenous Implantable Cardioverter Defibrillator Lead Systems: Operative Morbidity and Mortality

Introduction of non‐thoracotomy lead systems™ (Medtronic, Inc.) for the implantable cardioverter defibrillator (ICD) has expanded the indications for use of this mode of therapy. Patients previously considered “too ill” to undergo a thoracotomy as well as patients who are at a high risk for developing sudden death but without previous cardiac arrest, are now considered candidates. The initial experience with the non‐thoracotomy lead system at our institution was analyzed for morbidity and mortality. Thirty‐four patients underwent attempted intravascular lead implantation, with 30 having initial successful implantation (88.2%). There were 23 males; average ejection fraction (EF) was 38.6%. Three patients developed pulmonary edema and low output immediately after the procedure. Three patients developed electromechanical dissociation during defibrillation threshold testing. A prolonged testing time for the non‐thoracotomy lead system was noted when compared to the thoracotomy system (57.39 vs 32.30 min; P < 0.0000). There were more intraoperative morbidities with the non‐thoracotomy leads than with the thoracotomy system. There were no perioperative deaths. The potential consequences of prolonged anesthesia time and extensive defibrillation threshold testing should be considered when choosing the route of ICD implant, the type of anesthesia, and the intraoperative testing protocol for each patient.

Heart Rate Variability and Diastolic Heart Failure

Diastolic heart failure accounts for up to 40% of patients with congestive heart failure (CHF), and is associated with a better prognosis as compared to patients with systolic dysfunction. Nevertheless, patients with diastolic dysfunction have a significantly higher mortality as compared to the normal population. Reduced heart rate variability (HRV), a marker of autonomic dysfunction, is associated with increased mortality in patients with systolic heart failure. We therefore sought to determine to what extent HRV is altered in a population of patients with diastolic heart failure. Twenty‐four hour ambulatory (Holter) recordings were performed in 19 consecutive patients with diastolic heart failure, in 9 patients with systolic heart failure, as well as in 9 healthy volunteers (normal controls). Time and frequency domain HRV variables were obtained for all three groups of patients. Both Time and Frequency domain variables were found to be reduced in both heart failure groups compared to normal controls. When compared with each other, patients with diastolic function had relatively higher values of HRV variables, compared to those with systolic dysfunction (SDNN, Total power, ULF power, all P ≤ 0.05). Patients with diastolic dysfunction have reduced HRV, suggesting a disturbed sympathetic‐parasympathetic balance. Nevertheless, values for HRV are not as profoundly reduced as in patients with systolic dysfunction. The relative preservation of sympathetic‐parasympathetic balance may explain the better prognosis in this patient population. (PACE 2004; 27:299–303)