Initial experience with larger laser sheaths for the removal of transvenous pacemaker and implantable defibrillator leads.

BACKGROUND: In a previous randomized trial, the 12F laser sheath removed pacing leads via the implant vein more successfully than traditional mechanical tools alone. Two larger sizes of laser sheath, the 14F and 16F models, were developed to extract defibrillator leads and large-diameter pacing leads implanted for the chronic. These devices use pulsed ultraviolet laser light to core though fibrotic tissue grown over the lead body to free the lead from the vasculature. A mandatory prospective registry studied the safety and effectiveness profiles of the larger laser sheaths vis-à-vis the 12F laser sheath. METHODS AND RESULTS: In this study, 863 patients underwent extraction of 1285 leads at 52 sites. Patients treated with the 14F device tended to have older leads than the 12F population; the 16F population, which comprised mostly defibrillator patients, were younger, had younger leads, and were more often male than the 12F population. Clinical success (extracting the entire lead or the lead body minus the distal electrode) was observed in 91% to 92% of cases for all device sizes. The overall complication rate was 3.6%, with 0.8% perioperative mortality. Incidence of complications was independent of laser sheath size. CONCLUSIONS: The 14F and 16F laser sheaths offer an extraction option for larger long-term transvenous pacemaker and defibrillator leads that is as safe and effective as the 12F laser sheath.

Mechanism of hemodynamic improvement by dual-chamber pacing for severe left ventricular dysfunction: an acute Doppler and catheterization hemodynamic study.

OBJECTIVES: This study was undertaken to determine the mechanism by which improvement in hemodynamic variables may occur with dual-chamber pacing in patients with severe left ventricular dysfunction. BACKGROUND: Dual-chamber pacing has recently been proposed as a therapeutic alternative for the relief of symptoms in patients with dilated cardiomyopathy. METHODS: Fifteen patients with severe left ventricular systolic dysfunction were studied acutely during atrioventricular (AV) sequential pacing at various AV intervals (60, 100, 120, 140, 180 and 240 ms) with use of combined Doppler velocity curves and pressures obtained by high fidelity manometer-tipped catheters and thermodilution cardiac output. RESULTS: Neither cardiac output nor mean left atrial pressure was significantly different when hemodynamic variables in the baseline state were compared with those during AV sequential pacing at the various AV intervals in all patients. The patients were classified into two groups. In group I (eight patients with PR intervals > 200 ms on the rest 12-lead electrocardiogram), cardiac output was significantly increased when AV sequential pacing at the optimal AV interval to output was compared with that at the baseline state (3.0 +/- 1.0 vs. 3.9 +/- 0.43 liters/min, p = 0.005) because timing of mechanical atrial and ventricular synchrony was optimized. In addition, left ventricular end-diastolic pressure and duration of diastolic filling were increased, and diastolic mitral regurgitation was abolished. In group II (seven patients who had normal AV conduction at rest), cardiac output during AV pacing decreased from the baseline value without change in the diastolic filling period. CONCLUSIONS: Dual-chamber pacing may improve acute hemodynamic variables in selected patients with dilated cardiomyopathy, mainly by optimization of the timing of mechanical atrial and ventricular synchrony. Reestablishment of the optimal diastolic filling period and abolition of diastolic mitral regurgitation may also contribute to hemodynamic improvement.

Effect of 1.5 tesla nuclear magnetic resonance imaging scanner on implanted permanent pacemakers.

Patients with a permanent pacemaker are currently restricted from diagnostic nuclear magnetic resonance (NMR) imaging because of potential adverse effects on the pacemaker by the magnet. Previous work has shown that NMR imaging will result in asynchronous pacing of the pulse generator within a given distance of the magnet. The radiofrequency signal generated by the system may also result in rapid cardiac pacing, which may have deleterious effects. This study utilized a 1.5 tesla unit in an in vivo laboratory animal to evaluate the unit's effects on eight different pulse generators from two manufacturers. All pacemakers functioned in an asynchronous mode when placed within a certain distance of the magnet. In addition, transient reed switch inhibition was observed. Seven of the eight pulse generators paced rapidly when exposed to the radiofrequency signal and there was a dramatic decrease in arterial blood pressure. Whether effective rapid cardiac pacing would occur could not be predicted before exposure to the magnetic resonance unit. Nuclear magnetic resonance imaging with high magnetic fields in patients with a pacemaker should continue to be avoided until the mechanism of the rapid cardiac pacing can be further delineated and either predicted or prevented.

Changing experience with dual chamber (DDD) pacemakers.

Dual chamber (DDD) or "universal" pacemakers have had a significant impact on the advancement of artificial pacemakers by providing a more physiologic approach to cardiac pacing. However, with the early generation of DDD pacemakers (pacemakers that sense and pace in both the atrium and the ventricle), a significant number of patients experienced pacemaker-mediated tachycardia because intact ventriculoatrial conduction was sensed in the atrium and a reentrant tachycardia was induced. Newer generation DDD pacemakers have provided longer atrial refractory periods, which should correct this problem. In this study the first and second years of a 2 year experience with DDD pacemakers were compared to determine if the newer generation devices have allowed maintenance of pacing in the DDD mode as opposed to reprogramming to some alternate mode because of pacemaker-mediated tachycardia or other pacing problems. The results showed a significant decrease in pacemaker-mediated tachycardia during the second year and continuation of pacing in the DDD mode in a higher percent of patients. This improvement is attributed to improvement in the pulse generator as well as better patient selection.

Effect of dual-chamber pacing on systolic and diastolic function in patients with hypertrophic cardiomyopathy. Acute Doppler echocardiographic and catheterization hemodynamic study.

OBJECTIVES: This study sought to evaluate prospectively the acute hemodynamic effect of dual-chamber pacing by using a combined hemodynamic approach of high fidelity pressure and Doppler velocity measurements. BACKGROUND: Dual-chamber pacing has been proposed recently as an alternative in the symptomatic treatment of patients with hypertrophic obstructive cardiomyopathy. Although early reports documented a decrease in left ventricular outflow tract gradient and symptomatic improvement, questions remain about the hemodynamic effects of dual-chamber pacing on systolic and diastolic function. METHODS: Twenty-nine patients with hypertrophic cardiomyopathy underwent a combined cardiac catheterization and Doppler echocardiographic study during normal sinus rhythm and P-synchronous pacing at various atrioventricular (AV) intervals. High fidelity pressure measurements of left ventricular inflow and left atrial pressures, ascending aortic pressure, thermodilution cardiac output and Doppler mitral flow velocity curves were obtained to evaluate both systolic and diastolic left ventricular function. RESULTS: During AV pacing at the shortest delay of 60 ms, there was a significant decrease in cardiac output (p < 0.05) and peak positive dP/dt (p < 0.05), an increase in mean left atrial pressure (p < 0.05) and a prolongation of tau, the time constant of relaxation (p < 0.05), compared with that during normal sinus rhythm. During pacing at the optimal AV delay (longest AV interval with pre-excitation), there was a similar trend, with deterioration in both systolic and diastolic function variables but of lesser magnitude than that during pacing at the shortest AV intervals. The deterioration in both systolic and diastolic function was present in 21 patients with and 8 without left ventricular outflow obstruction. There was a modest decrease in left ventricular outflow tract gradient from 73.3 +/- 45.0 (mean +/- SD) to 61.3 +/- 40.5 mm Hg (p = 0.03) during dual-chamber pacing at the optimal AV delay compared with that during normal sinus rhythm. CONCLUSIONS: The acute effect of pacing the right atrium and ventricle may be detrimental to both systolic and diastolic function of the left ventricle, particularly at the short AV intervals. Further studies of the long-term effects of dual-chamber pacing in carefully performed randomized studies are needed.

Cardiac arrhythmias in patients with surgical repair of Ebstein's anomaly.

Preoperative, perioperative and postoperative arrhythmias in 52 consecutive patients who underwent operation for Ebstein's anomaly were reviewed. There were 25 male and 27 female patients (mean age 18 years, range 11 months to 64 years). Thirty-four patients had one or more documented arrhythmias preoperatively (18 had paroxysmal supraventricular tachycardia, 10 had paroxysmal atrial fibrillation or flutter, 13 had ventricular arrhythmia and 3 had high grade atrioventricular block). Seven patients without documented arrhythmias had a history typical of tachyarrhythmias. During the perioperative and early postoperative periods, 14 patients had atrial tachyarrhythmias and 8 had ventricular tachycardia or ventricular fibrillation. There were seven deaths between day 1 and 27 months after operation. Five of these deaths were sudden (all in male patients, aged 12 to 34 years), and four of the patients had had perioperative ventricular tachycardia or ventricular fibrillation. One patient was taking one antiarrhythmic agent and another patient was taking two at the time of sudden death. Of the 18 patients with paroxysmal supraventricular tachycardia and 9 patients with paroxysmal atrial fibrillation or flutter preoperatively who were followed up for a mean of 40 and 36 months, respectively, 22 and 33% continued to have symptomatic tachycardia. Of the 11 patients (mean age 9 years) without preoperative documentation or symptoms of arrhythmia, follow-up data were obtained (range 1 to 144 months, mean 31) in 9 patients. None died suddenly or developed symptomatic arrhythmia.

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.

Pacemaker lead extraction with the laser sheath: results of the pacing lead extraction with the excimer sheath (PLEXES) trial.

OBJECTIVES: The purpose of this study was to evaluate the safety and effectiveness of pacemaker lead extraction with the excimer sheath in comparison to nonlaser lead extraction. BACKGROUND: Fibrotic attachments that develop between chronically implanted pacemaker leads and to the venous, valvular and cardiac structures are the major obstacles to safe and consistent lead extraction. Locking stylets and telescoping sheaths produce a technically demanding but effective technique of mechanically disrupting the fibrosis. However, ultraviolet excimer laser light dissolves instead of tearing the tissue attachments. METHODS: A randomized trial of lead extraction was conducted in 301 patients with 465 chronically implanted pacemaker leads. The laser group patients had the leads removed with identical tools as the nonlaser group with the exception that the inner telescoping sheath was replaced with the 12-F excimer laser sheath. Success for both groups was defined as complete lead removal with the randomized therapy without complications. RESULTS: Complete lead removal rate was 94% in the laser group and 64% in the nonlaser group (p = 0.001). Failed nonlaser extraction was completed with the laser tools 88% of the time. The mean time to achieve a successful lead extraction was significantly reduced for patients randomized to the laser tools, 10.1 +/- 11.5 min compared with 12.9 +/- 19.2 min for patients randomized to nonlaser techniques (p < 0.04). Potentially life-threatening complications occurred in none of the nonlaser and three of the laser patients, including one death (p = NS). CONCLUSIONS: Laser-assisted pacemaker lead extraction has significant clinical advantages over extraction without laser tools and is associated with significant risks.

Relation between mode of pacing and long-term survival in the very elderly.

OBJECTIVES: This study analyzes the relationship between pacing mode and long-term survival in a large group of very elderly patients (> or = 80 years old). BACKGROUND: The relationship between pacing mode and long-term survival is not clear. Because the number of very elderly who are candidates for pacing is increasing, issues related to pacemaker (PM) use in the elderly have important clinical and economic implications. METHODS: We retrospectively reviewed 432 patients (mean age, 84.5+/-3.9 years) who received their initial PM (ventricular in 310 and dual chamber in 122) between 1980 and 1992. Follow-up was complete (3.5+/-2.6 years). Observed survival was estimated by the Kaplan-Meier method. Age- and gender-matched cohorts from the Minnesota population were used for expected survival. Log-rank test and Cox regression hazard model were used for univariate and multivariate analyses. RESULTS: Patients with ventricular PMs appeared to have poor overall survival compared with those with dual-chamber PMs. Observed survival after PM implantation in high grade atrioventricular block (AVB) patients was significantly worse than expected survival of the age- and gender-matched population (p < 0.0001), whereas observed survival of patients with sinus node dysfunction was not significantly different from expected survival of the matched population (p = 0.413). By univariate analysis, ventricular pacing in patients with AVB appeared to be associated with poor survival compared with dual-chamber pacing (hazard ratio [HR] 2.08; 95% confidence interval [CI] 1.33 to 3.33). After multivariate analysis, this difference was no longer significant (HR 1.41; 95% CI 0.88 to 2.27). Independent predictors of all-cause mortality were number of comorbid illnesses, New York Heart Association functional class, left ventricular depression and older age at implant. Pacing mode was not an independent predictor of overall survival. Older age at implantation, diabetes mellitus, dementia, history of paroxysmal atrial fibrillation and earlier year of implantation were independent predictors of ventricular pacemaker selection. CONCLUSIONS: After PM implantation, long-term survival among very elderly patients was not affected by pacing mode after correction of baseline differences. Selection bias was present in pacing mode in the very elderly, with ventricular pacing selected for sicker and older patients, perhaps partly explaining the apparent "beneficial impact on survival" observed with dual-chamber pacing.

Evolving indications for permanent pacing.

Indications for permanent pacemakers have expanded in recent years. The American College of Cardiology (ACC) and American Heart Association (AHA) guidelines for implantation of cardiac pacemakers were recently updated and now include several of the newer indications. Greatest interest about newer applications of pacemaker therapy focuses on hypertrophic obstructive cardiomyopathy, dilated cardiomyopathy, and pacing for the prevention of atrial fibrillation. Pacing for neurocardiogenic syncope remains controversial despite emerging data. Pacing for long QT syndrome, pacing after cardiac transplantation, and pacing for hemodynamic improvement in the occasional patient with first-degree atrioventricular block and hemodynamic compromise also warrant attention. Available clinical data are discussed in the context of the recent ACC and AHA guidelines.

Symptomatic conduction system disease in cardiac amyloidosis.

Symptomatic conduction system disease in cardiac amyloidosis and its management has been reported infrequently. We report our experience of patients with amyloidosis having symptomatic conduction system disease requiring permanent pacemaker implantation.

Evolving indications for permanent cardiac pacing: an appraisal of the 1998 American College of Cardiology/American Heart Association Guidelines.

Concise and complete guidelines of indications for permanent pacemakers are critical for the clinician involved in permanent pacing. A critical appraisal of the American College of Cardiology/American Heart Association 1998 guidelines on indications for permanent pacing clarifies inconsistencies and expands on information within the current guidelines.

Long-term survival after pacemaker implantation for heart block in patients > or = 65 years.

Permanent pacing can prevent recurrent symptoms and reduce mortality in elderly patients with symptomatic high-degree atrioventricular (AV) block. However, long-term survival with respect to comparable control subjects has not been well defined. In our study, relative long-term survival and prognostic predictors after permanent pacemaker implantation for symptomatic high-degree AV block were assessed among all residents of Olmsted County, Minnesota, who were > or = 65 years old. Of the 154 patients, 77 were men and 77 were women (mean age 80 +/- 7 years). Follow-up was 0.1 to 19.8 years (mean 4.2 +/- 2.8). Sixty-nine patients had isolated AV block and 85 had coexisting heart disease. Observed survival at 1, 3, 5, and 10 years was 85%, 68%, 52%, 21%, and 72%, 50%, 31%, 11% for patients with isolated AV block and patients with coexisting heart disease, respectively (p = 0.006). Observed survival in patients 65 to 79 years old with isolated AV block was comparable to age- and sex-matched cohorts (p = 0.53), but in patients aged > or = 80 years, it was less than that for control subjects (p = 0.014). In patients with coexisting heart disease, observed survival was less than that for control subjects in patients 65 to 79 years old (p < 0.001) and > or = 80 years (p < 0.001). Multivariate analysis identified congestive heart failure, chronic obstructive pulmonary disease, age, syncope, insulin-dependent diabetes mellitus, and male gender as independent predictors of increased mortality.

Long-term survival after permanent pacemaker implantation for sick sinus syndrome.

In this population-based study, long-term survival and prognostic factors were examined in 148 patients, 55 men and 93 women, from Olmsted County, Minnesota, who had permanent pacemaker implantation for sick sinus syndrome between 1969 and 1991. The overall survival for patients who had received a permanent pacemaker for sick sinus syndrome was significantly worse than that of an age- and sex-matched control population (p < 0.0001). The increased mortality was attributable at least in part to the presence of structural heart disease in patients with sick sinus syndrome who had undergone permanent pacemaker implantation (82 of 148 patients, 55%). Survival of patients with isolated sick sinus syndrome was comparable (p = 0.6729), whereas in patients with structural heart disease it was significantly worse than expected (p < 0.0001). Symptoms were eliminated or improved in 116 patients (78%) after pacemaker implantation. Multivariate analysis identified congestive heart failure, valvular heart disease, history of stroke or transient ischemic attack, and age as independent risk factors for mortality. However, there was a trend toward decreased survival in patients who had received ventricular pacing compared with those who had received dual-chamber pacing, but this difference did not reach statistical significance (p = 0.0556). The mode of pacing was not an independent risk factor (p = 0.23). The observed survival of patients aged < 80 years was significantly worse than expected (p < 0.0001), whereas that of patients aged > or = 80 years was similar to the expected (p = 0.22).

A stepwise testing protocol for modern implantable cardioverter-defibrillator systems to prevent pacemaker-implantable cardioverter-defibrillator interactions.

Current use of newer implantable cardioverter-defibrillators (ICDs) has changed the spectrum of pacemaker-ICD interactions and provided new tools for testing and understanding those interactions. Testing for pacemaker-ICD interactions was performed in 31 procedures involving 22 patients. The protocol included: (1) evaluation of pacemaker stimulus artifact amplitude and its ratio to that of the evoked ventricular electrogram, (2) testing for inhibition of ventricular fibrillation (VF) detection by the ICD during asynchronous pacing at maximum output, (3) evaluation by pacemaker event marker recordings of pacemaker sensing behavior while programmed to nonasynchronous mode during ventricular tachycardia (VT) or VF, and (4) evaluation of postshock interactions. Inhibition of detection of VT/VF was found in 6 of 22 patients (27.2%). Large stimulus artifact amplitude (>2 mV) or stimulus artifact:evoked QRS ratio > 1/3 had a positive predictive accuracy of 18% and 14.4%, respectively, and a negative predictive accuracy of 100% and 92.3%, respectively, for clinically significant interaction. Asynchronous pacing occurred in 16 of 31 procedures (51.6%), and was due to underdetection by the pacemaker in 4 of 16 (25%) and noise reversion in 12 of 16 (75%). Postshock phenomena occurred in 6 cases, 3 of which were clinically significant. Overall, 11 of 22 patients (50%) had clinically significant interactions discovered by this protocol, which led to system revisions in 6 and to pacemaker output reprogramming in 5. Thus, pacemaker-ICD interactions are frequently detected using a thorough and systematic protocol. Most cases can be managed by system revision or pacemaker reprogramming.

Indications, effectiveness, and long-term dependency in permanent pacing after cardiac surgery.

The purposes of this study were to define predictors of long-term pacemaker dependency in patients having permanent pacemakers implanted shortly after cardiac surgery, and to evaluate short- and long-term results and survival in this population. Data from 120 adult patients with implantation since 1980 were retrospectively analyzed. Acute and chronic complication rates (4.2% and 16.6%, respectively) were not higher than those expected in the general paced population. In addition, continuous rhythm was evaluated by use of pacemaker inhibition in a subgroup of 20 patients to verify the validity of clinical criteria for pacemaker dependency. Of the patients evaluated for dependency, 41% eventually became nondependent. Prolonged monitoring with an inhibited pacemaker confirmed the accuracy of our method of clinical evaluation of pacemaker dependency. Significant predictors of long-term pacemaker dependency were complete atrioventricular block as the indication and bypass time of > 120 minutes (by multivariate and univariate analyses, respectively). Postoperative complete atrioventricular block is the most important predictor of pacemaker dependency, enabling an earlier decision on permanent pacemaker implantation (no later than the sixth and the ninth postoperative days for wide-complex and narrow-complex escape, respectively). Further prospective studies are needed to define optimal implantation times for indications other than complete atrioventricular block.

The next 5 years in cardiac pacemakers: a preview.

Advances in cardiac pacing continue at an astounding rate, and, occasionally, technologic capabilities are developed almost faster than they can be implemented clinically. The development and implementation of single- and dual-chamber rate-adaptive pacemakers have been the major thrusts in cardiac pacing in recent years. Rate-adaptive pacing will continue to be of primary interest in the future as investigators search for the perfect "sensor" and attempt to develop rate-adaptive pacemakers with multiple sensors. The "smart" pacemaker--that is, an autoprogramming, autodiagnostic device--will also be refined. The ultimate "smart" pacemaker would be capable of automatically adjusting output and sensing factors as well as altering the rate-adaptive variables and even changing the pacing mode in response to variations in the underlying rhythm. Other aspects of cardiac pacing that will be actively investigated include new low-threshold pacing lead designs, refinements of the single-lead pacing system capable of P-synchronous pacing, and diagnostic information that can be derived from sensors used for rate-adaptive pacing.

Second-degree atrioventricular block: a reappraisal.

In this review, we discuss the various forms and causes of second-degree atrioventricular (AV) block and the reasons they remain poorly understood. Both type I and type II block characterize block of a single sinus P wave. Type I block describes visible, differing, and generally decremental AV conduction. Type II block describes what appears to be an all-or-none conduction without visible changes in the AV conduction time before and after the blocked impulse. Although the diagnosis of type II block is possible with an increasing sinus rate, absence of sinus slowing is an important criterion of type II block because a vagal surge (generally a benign condition) can cause simultaneous sinus slowing and AV nodal block, which can superficially resemble type II block. The diagnosis of type II block cannot be established if the first postblock P wave is followed by a shortened PR interval or is not discernible. A pattern resembling a narrow QRS type II block in association with an obvious type I structure in the same recording (e.g., Holter) effectively rules out type II block because the coexistence of both types of narrow QRS block is exceedingly rare. Concealed His bundle or ventricular extrasystoles confined to the specialized conduction system without myocardial penetration and depolarization can produce electrocardiographic patterns that mimic type I and/or type II block (pseudo-AV block). All correctly defined type II blocks are infranodal. A narrow QRS type I block is almost always AV nodal, whereas a type I block with bundle branch block barring acute myocardial infarction is infranodal in 60% to 70% of cases. A 2:1 AV block cannot be classified in terms of type I or type II block, but it can be nodal or infranodal. Infranodal blocks require pacing regardless of form or symptoms. The widespread use of numerous disparate definitions of type II block appears primarily responsible for many of the problems surrounding second-degree AV block. Adherence to the correct definitions provides a logical and simple framework for clinical evaluation.

Venous complications after insertion of a transvenous pacemaker.

We reviewed the incidence, clinical features, current diagnostic evaluations, and treatments of venous complications that can occur after implantation of a transvenous pacemaker. Of the approximately 80 published articles on the potential venous complications after implantation of a permanent transvenous pacemaker, we selected 63 that addressed the clinical features, diagnosis, and treatment of pacemaker lead-induced venous thrombosis, which occurs in approximately 30 to 45% of patients early or late after implantation of a transvenous pacemaker. Most patients with chronic deep venous thrombosis remain asymptomatic because of the development of an adequate venous collateral circulation. Clinical features of pacemaker lead-induced deep venous thrombosis, although rare, are easily recognized. They should be sought routinely during follow-up of all patients with transvenous pacemaker leads because venous obstruction can interfere with intravenously administered therapy, monitoring of central venous pressure, and revision of a pacemaker lead. Acute deep venous thrombosis is likely to be symptomatic. Early recognition and treatment of acute deep venous thrombosis may help to decrease the potential morbidity and mortality. The definitive diagnosis of pacemaker lead-induced venous thrombosis necessitates contrast-enhanced or digital subtraction venography. Management includes anticoagulation, thrombolytic therapy, surgical intervention, and, recently, percutaneous transluminal balloon venoplasty and depends on the duration, extent, and site of venous occlusion as well as the accompanying symptoms.

Sinus node dysfunction in pediatric and young adult patients: treatment by implantation of a permanent pacemaker in 39 cases.

To examine the clinical course of sinus node dysfunction that necessitates permanent pacing in the pediatric and young adult populations, we studied the records of the 39 patients 40 years of age or younger (mean age, 23 years) who underwent implantation of a permanent pacemaker for treatment of this disorder at our medical center between 1960 and 1983. The tachycardia-bradycardia syndrome was the most common rhythm disturbance, and syncope was the most frequent initial symptom. All symptomatic patients noted resolution of symptoms after pacemaker implantation. Twenty-five of the 39 patients (64%) had associated cardiovascular disease, most commonly transposition of the great arteries. In each of the 11 patients with this anomaly, sinus node dysfunction developed after a surgical procedure for correction of the defect. Of the total patient population, 20 patients (51%) had previously undergone a cardiac operation. The mean interval between pacemaker implantation and the previous operation was 105 months. After a mean follow-up of 50.5 months, the patients with no obvious underlying heart disease have done well. Each of the eight patients who have died had underlying cardiovascular disease. None of the deaths was thought to be pacemaker related. Sinus node dysfunction should be considered in the differential diagnosis of young patients with syncope or dizziness, especially if they have undergone a reparative cardiac surgical procedure. If symptomatic sinus node dysfunction is confirmed, permanent pacing is an effective therapeutic modality. In the absence of associated heart disease, the prognosis seems to be excellent.