Jane M. Trusty

Long-Term Progression and Outcomes With Aging in Patients With Lone Atrial Fibrillation: A 30-Year Follow-Up Study

Background— The long-term natural history of lone atrial fibrillation is unknown. Our objective was to determine the rate and predictors of progression from paroxysmal to permanent atrial fibrillation over 30 years and the long-term risk of heart failure, thromboembolism, and death compared with a control population. Methods and Results— A previously characterized Olmsted County, Minnesota, population with first episode of documented atrial fibrillation between 1950 and 1980 and no concomitant heart disease or hypertension was followed up long term. Of this unique cohort, 76 patients with paroxysmal (n=34), persistent (n=37), or permanent (n=5) lone atrial fibrillation at initial diagnosis met inclusion criteria (mean age at diagnosis, 44.2±11.7 years; male, 78%). Mean duration of follow-up was 25.2±9.5 years. Of 71 patients with paroxysmal or persistent atrial fibrillation, 22 had progression to permanent atrial fibrillation. Overall survival of the 76 patients with lone atrial fibrillation was 92% and 68% at 15 and 30 years, respectively, similar to 86% and 57% survival for the age- and sex-matched Minnesota population. Observed survival free of heart failure was slightly worse than expected (P=0.051). Risk for stroke or transient ischemic attack was similar to the expected population risk during the initial 25 years of follow-up but increased thereafter (P=0.004), although CIs were wide. All patients who had a cerebrovascular event had developed ≥1 risk factor for thromboembolism. Conclusions— Comorbidities significantly modulate progression and complications of atrial fibrillation. Age or development of hypertension increases thromboembolic risk.

Dual-Chamber Pacing for Hypertrophic Cardiomyopathy: A Randomized, Double-Blind, Crossover Trial

OBJECTIVES In a double-blind, randomized, crossover trial we sought to evaluate the effect of dual-chamber pacing in patients with severe symptoms of hypertrophic obstructive cardiomyopathy. BACKGROUND Recently, several cohort trials showed that implantation of a dual-chamber pacemaker in patients with severely symptomatic hypertrophic obstructive cardiomyopathy can relieve symptoms and decrease the severity of the left ventricular outflow tract gradient. However, the outcome of dual-chamber pacing has not been compared with that of standard therapy in a randomized, double-blind trial. METHODS Twenty-one patients with severely symptomatic hypertrophic obstructive cardiomyopathy were entered into this trial after baseline studies consisting of Minnesota quality-of-life assessment, two-dimensional and Doppler echocardiography and cardiopulmonary exercise tests. Nineteen patients completed the protocol and underwent double-blind randomization to either DDD pacing for 3 months followed by backup AAI pacing for 3 months, or the same study arms in reverse order. RESULTS Left ventricular outflow tract gradient decreased significantly to 55 +/- 38 mm Hg after DDD pacing compared with the baseline gradient of 76 +/- 61 mm Hg (p < 0.05) and the gradient of 83 +/- 59 mm Hg after AAI pacing (p < 0.05). Quality-of-life score and exercise duration were significantly improved from the baseline state after the DDD arm but were not significantly different between the DDD arm and the backup AAI arm. Peak oxygen consumption did not significantly differ among the three periods. Overall, 63% of patients had symptomatic improvement during the DDD arm, but 42% also had symptomatic improvement during the AAI backup arm. In addition, 31% had no change and 5% had deterioration of symptoms during the DDD pacing arm. CONCLUSIONS Dual-chamber pacing may relieve symptoms and decrease gradient in patients with hypertrophic obstructive cardiomyopathy. In some patients, however, symptoms do not change or even become worse with dual-chamber pacing. Subjective symptomatic improvement can also occur from implantation of the pacemaker without its hemodynamic benefit, suggesting the role of a placebo effect. Long-term follow-up of a large number of patients in randomized trials is necessary before dual-chamber pacing can be recommended for all patients with severely symptomatic hypertrophic obstructive cardiomyopathy.

Syncope Evaluation in the Emergency Department Study (SEEDS) A Multidisciplinary Approach to Syncope Management

Background—The primary aim and central hypothesis of the study are that a designated syncope unit in the emergency department improves diagnostic yield and reduces hospital admission for patients with syncope who are at intermediate risk for an adverse cardiovascular outcome. Methods and Results—In this prospective, randomized, single-center study, patients were randomly allocated to 2 treatment arms: syncope unit evaluation and standard care. The 2 groups were compared with &khgr;2 test for independence of categorical variables. Wilcoxon rank sum test was used for continuous variables. Survival was estimated with the Kaplan-Meier method. One hundred three consecutive patients (53 women; mean age 64±17 years) entered the study. Fifty-one patients were randomized to the syncope unit. For the syncope unit and standard care patients, the presumptive diagnosis was established in 34 (67%) and 5 (10%) patients (P<0.001), respectively, hospital admission was required for 22 (43%) and 51 (98%) patients (P<0.001), and total patient-hospital days were reduced from 140 to 64. Actuarial survival was 97% and 90% (P=0.30), and survival free from recurrent syncope was 88% and 89% (P=0.72) at 2 years for the syncope unit and standard care groups, respectively. Conclusions—The novel syncope unit designed for this study significantly improved diagnostic yield in the emergency department and reduced hospital admission and total length of hospital stay without affecting recurrent syncope and all-cause mortality among intermediate-risk patients. Observations from the present study provide benchmark data for improving patient care and effectively utilizing healthcare resources.

Permanent pacemaker infections: Characterization and management

From January 1974 to June 1980, a total of 46 patients were treated for infections involving permanent pacing systems. Demographic characteristics, types of infecting organisms, specific clinical features, significance of an infected foreign body and various medical and surgical treatment methods are described. Likely infecting organisms depend on the mode of presentation and the time course of the infection. Optimal treatment for the large majority of patients requires removal of the entire infected pacing system. In a subgroup of patients, a short course of antibiotic therapy followed by one stage surgery involving implantation of a new pacing system and concurrent explanation of the infected pacemaker was used safely with excellent results.

High failure rate for an epicardial implantable cardioverter-defibrillator lead: implications for long-term follow-up of patients with an implantable cardioverter-defibrillator.

OBJECTIVES The purpose of this study was to determine the risk of epicardial lead failure during long-term follow-up and its mode of presentation. BACKGROUND Despite the high prevalence of epicardial lead-based implantable cardioverter-defibrillators, their long-term performance is unknown, and appropriate follow-up has not been established. METHODS The study group comprised all patients in whom an epicardial lead system was implanted at the Mayo Clinic between October 31, 1984 and November 3, 1994. The number of lead fractures and leads with fluid within the insulation and the mode of presentation were determined retrospectively by review of patient visits, radiographs of lead systems and data derived from formal lead testing. RESULTS At 4 years, the survival rate free of lead malfunction, using formal lead testing, for 160 Medtronic epicardial patches (models 6897 and 6921) was 72% compared with 92.5% for the 179 Cardiac Pacemaker, Inc. (CPI) patches (models 0040 and 0041) (p = 0.01). In addition, five Medtronic patches in three patients had fluid within the lead insulation but no obvious fracture. No CPI patches had fluid identified within the leads. Of 330 Medtronic epicardial pace/sense leads (model 6917), the 4-year survival rate free of lead malfunction as assessed by lead testing was 96%. In all, 19 presentations of lead malfunction were found in 17 patients (2 patients had more than one lead fracture at different times). In 11 (58%) of these presentations, the patients were asymptomatic despite the presence of obvious lead fracture. CONCLUSIONS Epicardial lead malfunction is common on long-term follow-up, and some leads have a failure rate of 28% at 4 years. Many patients with fractured leads remain asymptomatic, despite involvement of multiple leads in some cases. Therefore, consideration should be given to regular periodic lead testing in addition to routine X-ray examination, as asymptomatic lead malfunction can present with normal chest X-ray findings.

Electrophysiologic Manifestations of Ventricular Tachyarrhythmias Provoking Appropriate Defibrillator Interventions in High-Risk Patients with Hypertrophic Cardiomyopathy

Introduction: Our objective was to determine features of ventricular tachyarrhythmias triggering appropriate implantable cardioverter‐defibrillator (ICD) interventions in hypertrophic cardiomyopathy (HCM).

Influence of ventricular function and presence or absence of coronary artery disease on results of electrophysiologic testing for asymptomatic nonsustained ventricular tachycardia.

One hundred ten patients with asymptomatic nonsustained ventricular tachycardia (VT) were evaluated prospectively to assess the value of electrophysiologic testing. This testing consisted of up to 3 extrastimuli delivered during 3 drive cycle lengths from 2 right ventricular sites. A positive study was defined as monomorphic VT lasting 30 seconds or requiring cardioversion. Patients with a positive study were treated, and serial drug testing was done. An event during follow-up was sustained VT or cardiac arrest. The mean follow-up was 15 months. Of 57 patients with an ejection fraction greater than or equal to 40%, 6 had a positive electrophysiologic test with 1 event and 51 had a negative test with 1 event. Twenty-eight patients had an ejection fraction less than 40% and coronary artery disease: 14 had a positive test with 1 event, and 14 had a negative test with 3 events. Twenty-five patients had an ejection fraction less than 40% and no coronary artery disease: 1 had a positive test with no events, and 24 had a negative test with 8 events. Only ejection fraction and congestive heart failure class were found to be independent predictors of outcome. Patients with an ejection fraction greater than 40% had low inducibility (11%), had few events (3.5%) and did not require electrophysiologic testing. In patients with an ejection fraction less than 40% and coronary artery disease, inducibility was high (50%) and a negative study was of no value. Patients with an ejection fraction less than 40% and no coronary artery disease had low inducibility (4%), had frequent events (33%) and did not benefit from electrophysiologic testing.

Consistent Subcutaneous Prepectoral Implantation of a New Implantable Cardioverter Defibrillator

OBJECTIVE To describe the use of a new implantable cardioverter defibrillator (ICD) that can be placed in the prepectoral region rather than implanted in the abdominal wall. DESIGN We report the experience of placement of this new ICD in the prepectoral region in 13 patients from Sept. 28, 1993, through Jan. 10, 1994, at the Mayo Clinic. MATERIAL AND METHODS Thirteen consecutive patients offered this new ICD underwent placement of transvenous defibrillation leads, and the pulse generator was placed in a pocket formed in the subcutaneous, prepectoral space. Testing ensured a defibrillation threshold of 24 J or less. RESULTS In all 13 patients, the pulse generator could be placed in the subcutaneous, prepectoral space. In all except one patient, acceptable defibrillation thresholds were achieved by using lead systems placed totally transvenously. Only one patient required placement of a subcutaneous patch. All but two patients were dismissed from the hospital within 3 days after the ICD implantation. CONCLUSION Consistent subcutaneous, prepectoral placement of this new ICD pulse generator is possible. Because the entire procedure can be performed in the pacemaker implantation room, the potential exists for decreasing the duration of the hospitalization and associated costs.

Determination of pacing capture in implantable defibrillators: benefit of evoked response detection using RV coil to can vector.

SPLETT, V., et al.: Determination of Pacing Capture in Implantable Defibrillators: Benefit of Evoked Response Detection Using RV Coil to Can Vector. Automatic detection of capture in ICDs would be useful for ensuring normal pacing function and lead integrity and may increase device longevity. Evoked response detection can be difficult due to postpace polarization. Polarization on the RV coil to can vector, however, should be absent when pacing with a true bipolar lead (pace tip to ring). Polarization on the RV coil to can vector should be low in an integrated bipolar lead due to the large surface area of the coil. Ventricular‐paced responses were prospectively recorded in 20 patients during ICD implantation or replacement. Capture and loss of capture responses were noted during threshold searches with electrograms recorded between the RV coil and can. A detector was designed to discriminate between capture and noncapture‐paced responses using data from the first 11 patients and validated on the remaining 9. The detector had a sensitivity of 99.9% (detected capture on capture beats), and had a specificity of 100% (detected no capture on noncapture beats) for all lead configurations. There was no measurable polarization with true bipolar leads. In integrated bipolar leads, maximum polarization ranged from 0.0 to 16.7mV. In conclusion, paced evoked responses can be detected in ICDs using the RV coil to can vector using standard pacing waveforms. Special polarization reducing pacing waveforms are not required. These observations could be used to design ICDs with automatic pacing threshold detection.

Dual-Chamber Pacing for Cardiomyopathies: A 1996 Clinical Perspective

Implantation of a permanent pacemaker is an accepted mode of therapy for symptomatic bradyarrhythmias. Application of pacemaker technology for the treatment of cardiomyopathies has generated considerable interest and enthusiastic support in recent years. In both hypertrophic cardiomyopathy and dilated cardiomyopathy, dual-chamber pacing has been shown to decrease symptoms and improve hemodynamics; however, not all patients will benefit from dual-chamber pacing. Technical considerations must be acknowledged in order to obtain optimal benefit with dual-chamber pacing. In addition, other more accepted therapies are available for patients with symptomatic cardiomyopathies. The purposes of this article are to review critically the current literature on the use of dual-chamber pacemakers in patients with either hypertrophic or dilated cardiomyopathy and to provide a clinical perspective based on current knowledge.