The impact of SMARTpass algorithm status on inappropriate shock rates in the UNTOUCHED Study

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): Boston Scientific Corporation

Background

The current Subcutaneous ICD (S-ICD) model incorporates SMART Pass (SP) to improve sensing and discrimination capabilities to reduce inappropriate shocks (IAS). SP status is programmable but may also be disabled automatically in the setting of low amplitude signals or low heart rate in order to avoid under-sensing of VT/VF.

Objective

To evaluate SP impact on IAS, appropriate shocks (AS), complications and mortality in the UNTOUCHED S-ICD trial.

Methods

Primary prevention patients (pts, n=1111) with ejection fraction ≤35% and no pacing requirement were followed for up to 18 months. SP status during a study visit was programmed ON or OFF and status between visits was either consistently OFF, ON, or automatically disabled (DIS). The impact of SP status on pt outcomes was evaluated using Kaplan-Meier (K-M) analysis. Multivariable proportional hazard analysis identified predictors of IAS and SP disable events.

Results

Percent of pts with SP always ON, always OFF, ON with DIS, and OFF then ON with no DIS were 56, 16, 15, and 13%, respectively. At least one SP DIS occurred in 177 pts, but only 13% had 2 or more, mostly due to PVCs and low EGM amplitudes. Significant multivariable predictors of SP disable events are history of atrial fibrillation (hazard ratio (HR) 2.49, odds ratio (OR) (1.49-4.16); p=.0005), only one passing vector at S-ICD screening, (HR 1.85, OR (1.10-3.10; p=.0202) and lower left ventricular ejection fraction (HR 1.05, OR (1.01-1.08); p=.0074). K-M IAS rates were highest for pts experiencing DIS (fig 1) and lowest for SP ON. While neither AS (p=0.58) nor complication (p=0.58) rates varied significantly according to SP status, mortality was lower for pts with SP ON during any duration of time (p=0.044) by univariate analysis. Further analysis is planned to better understand the relationship between SP status and mortality.

Conclusion

Patients in the UNTOUCHED trial with SMART Pass (SP) consistently ON had significantly fewer inappropriate shocks, with no impact on appropriate therapy for VT/VF. Patients with history of atrial fibrillation, lower left ventricular ejection fraction, and only one passing vector at S-ICD screening are at higher risk of SP disable events; therefore, care should be taken for these patients to assess SP status and their higher risk for inappropriate shocks.

The incidence and clinical ramifications for leadless pacemaker fixation mechanism exposure on the epicardial surface

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): Boston Scientific and Abbott

Background

Leadless pacemaker (LP) fixation mechanism exposure (FE) by penetration of the epicardial surface has been described. Previously reported animal model studies showed FE for 7/10 Micra LPs, versus 4/10 CapSureFix Novus RV pacing leads (both Medtronic). However, it is unknown whether FE causes pericardial effusion or pericarditis or does not have clinical significance.

Purpose

To determine the incidence of FE of a novel LP in a chronic animal model and its association with acute or chronic pericardial effusion.

Methods

 Canine subjects were implanted with novel LPs (Boston Scientific) in an ongoing study. Acute pericardial effusion was assessed by post-procedural transthoracic echocardiography (TTE). Chronic pericardial effusion was assessed by TTE 90 days after implantation and post-mortem assessed pericardial fluid colour (PFC) and volume (PFV). FE was assessed visually at necropsy. Mann-Whitney U tests and chi-squared tests were used to determine whether greater PFV, more haemorrhagic PFC or LP implantation location differed significantly between subjects with and without FE.

Results

 Results to date are reported. Canine subjects (n = 71) were chronically implanted with LPs. Due to 14 in-vivo retrievals, data is shown of 57 subjects with LPs in situ at necropsy. Pre-deployment radiocontrast injection confirmed LP position (RV apex n = 41; RV apicoseptal n = 16), and mechanical stability and electrical testing confirmed adequate talon fixation after deployment. Necropsy after median 94 days (IQR 91-540) demonstrated FE in 11 cases (19%) (figure). No acute nor chronic pericardial effusion was seen on TTE. Mean PFV for animals with and without FE was 1.8 and 1.6 cc, respectively. FE did not show an association with PFV or colour (p= 0.53 and p = 0.83, respectively). For two animals, PFV and PFC are not available; FE was not observed in either of these cases. LP implantation location was not associated with incidence of FE (p = 1.00).

Conclusion

 Fixation mechanism exposure by the talons of a novel leadless pacemaker was observed in 19% of animals implanted and was not associated with acute or chronic pericardial effusion. Abstract Figure 1

916The impact of anesthesia choice on subcutaneous implantable cardioverter defibrillator outcomes: acute and one year results from the post approval study

Funding Acknowledgements

This study was financially supported by Boston Scientific

The influence of anesthesia technique on the outcomes of subcutaneous implantable cardioverter defibrillator (SICD) implantation has not been prospectively evaluated.

The aim of the present analysis was to characterize the effect of anesthesia choice acutely and over a year follow-up in the large "real-world" cohort of the SICD Post Approval Study (SICD-PAS).

Patients received either general anesthesia (GA), conscious sedation (CS), or monitored anesthesia care (MAC) at the implanting physicians" discretion.  Acute results and complications over one year were compared between GA, CS and MAC.

1,631 patients were studied.  64.3% received GA , 29.2% received CS and 6.6% received MAC.  Procedure times were shortest for MAC versus GA and CS (Table 1).  Cross-over from CS and MAC to GA occurred in 2.9% and 1.9% of procedures, respectively.  The mean left ventricular ejection fraction (LVEF) was lower in the MAC cohort compared with GA and CS.  GA patients were less often discharged the same day than CS and MAC.  Patients who had GA were more likely to have had intra-operative DFT testing, while successful DFT testing at implant did not differ among groups (Table 1).  At one year, freedom from total complications did not differ between groups (93.3% for GA, 92.9% for CS and 87.8% for MAC, p = 0.095) nor did freedom from inappropriate shocks (94% for GA, 94.2% for CS, 88.9% for MAC, p = 0.138) nor appropriate shocks (95.8% for GA, 95% for CS, 95% for MAC, p = 0.747).

All three anesthesia techniques had similar acute and one year outcomes but, despite having worse LVEF, patients who received MAC had shorter procedure times and infrequently required conversion to GA.  GA was associated with higher rates of next day patient discharge.  These results suggest that MAC may be preferred for the majority of patients. This observation should be confirmed with prospective trials.

Table 1:Characteristics and Outcomes Parameter Conscious Sedation General Anesthesia Monitored Anesthesia Care P value Gender[%(N/Total)] Male 68.1 (324/476) 69.3 (726/1048) 66.4 (71/107) 0.77 Age (years) mean ± SD 54 ± 15 53 ± 15 54 ± 13 0.61 Body Mass Index mean ± SD 30 ± 7 30 ± 8 29 ± 6 0.41 Creatinine (mg/dL) mean ± SD 2 ± 2 2 ± 4 2 ± 2 0.43 LVEF (%) mean ± SD 33 ± 15 32 ± 15 26 ± 9 <0.001 Procedure Time (min) mean ± SD 85 ± 42 75 ± 33 65 ± 30 <0.001 Same Day Discharge % 70.3% 64.3% 72.6% 0.03 DFT Attempted % 84% 89.1% 81.3% 0.004 Successful DFT % 98.7% 98.6% 98.8% 0.97

Successful external cardioversion of atrial fibrillation in patients referred to an electrophysiologist for internal cardioversion

BACKGROUND

Internal cardioversion of atrial fibrillation with direct current energy has become an increasingly employed technique for patients who fail external cardioversion.

HYPOTHESIS

The purpose of this study was to determine whether internal cardioversion could be avoided by careful attention to cardioversion technique in a group of patients referred specifically for internal cardioversion after failed external cardioversion by community cardiologists.

METHODS

We performed external cardioversion utilizing two operators applying significant pressure to the thorax with up to 360 J prior to the planned internal cardioversion in 20 patients referred for internal cardioversion after failed attempts at external cardioversion.

RESULTS

Sixteen patients (80%) were successfully cardioverted and avoided the risk, inconvenience, and cost of internal cardioversion.

CONCLUSION

External cardioversion with significant anterior paddle pressure by two operators can decrease the need for internal cardioversion in a significant portion of patients referred to electrophysiologists for internal cardioversion and should be considered prior to an invasive procedure.

Effect of radiofrequency current on previously implanted pacemaker and defibrillator ventricular lead systems

We compared the response of endocardial lead systems to radiofrequency (RF) current delivered during atrio-ventricular junction ablation (AVJA) for atrial fibrillation with uncontrolled ventricular rate in 107 patients. The mean age was 67 +/- 11 years and the mean ejection fraction 42 +/- 15%. Patients were divided into 3 groups based on the type of ventricular lead present at the time of ablation: a previously implanted defibrillator lead (group 3, n = 13), a previously implanted pacemaker lead (group 2, n = 46) or a temporary lead (group 1, n = 48), which was subsequently followed by a permanent lead implantation. During AVJA, a median of 5 RF applications (44 +/- 8 W) were given via 4-5-mm electrodes. All but 1 patient had right-sided lesions, while 6 patients also had left sided lesions. Ventricular pacing thresholds were evaluated immediately pre- and post-ablation at 24 hours and at 1 to 3 months. Increases in ventricular pacing voltage thresholds were noted in all 3 groups over time, with the greatest mean increase in group 3 patients: [table: see text]. A greater than 2-fold increase in pacing thresholds was observed only with previously implanted leads, usually within the first 48 hours. It occurred significantly more often in patients with group 3 (6/13 [46%]) compared to group 2 (6/46 [13%], odds ratio 7.6, P = 0.006). A progressive rise in pacing threshold required lead revision in 2/13 group 3 patients (15%) and 2/46 group 2 patients (4%). While RF current has only minor effects on pacing threshold in most patients with previously implanted ventricular lead systems, clinically important alterations requiring device reprogramming or lead revision may occur. Group 3 are significantly more vulnerable to RF current, though the mechanisms are unclear. Group 1 during AVJA, followed by permanent lead implantation appears advisable. Pts with a previously implanted group 3 who require AVJA should be monitored closely.

Atypical atrial flutter originating in the right atrial free wall

BACKGROUND

Data from experimental models of atrial flutter indicate that macro-reentrant circuits may be confined by anatomic and functional barriers remote from the tricuspid annulus-eustachian ridge atrial isthmus. Data characterizing the various forms of atypical atrial flutter in humans are limited.

METHODS AND RESULTS

In 6 of 160 consecutive patients referred for ablation of counterclockwise and/or clockwise typical atrial flutter, an additional atypical atrial flutter was mapped to the right atrial free wall. Five patients had no prior cardiac surgery. Incisional atrial tachycardia was excluded in the remaining patient. High-density electroanatomic maps of the reentrant circuit were obtained in 3 patients. Radiofrequency energy application from a discrete midlateral right atrial central line of conduction block to the inferior vena cava terminated and prevented the reinduction of atypical atrial flutter in each patient. Atrial flutter has not recurred in any patient (follow-up, 18+/-17 months; range, 3 to 40 months).

CONCLUSIONS

Atrial flutter can arise in the right atrial free wall. This form of atypical atrial flutter could account for spontaneous or inducible atrial flutter observed in patients referred for ablation and is eliminated with linear ablation directed at the inferolateral right atrium.

Frozen shoulder syndrome associated with subpectoral defibrillator implantation

Pectoral implantation of transvenous non-thoracotomy internal cardioverter defibrillators (ICD) has resulted in very few complications whether placed subpectorally or subcutaneously. We report the case of a 68 year old man with a subpectorally implanted MINI-plus (Cardiac Pacemakers, Incorporated, St. Paul, Mn.) transvenous ICD who developed nearly instantaneous severe ipsilateral shoulder pain and immobilization. The symptoms progressed despite aggressive physical therapy. We elected to remove the device from the pectoral site and place it in a traditional abdominal position due to the severity, duration and refractoriness of his symptoms. This procedure utilized the chronic Endotak DSP (Model 0125, Cardiac Pacemakers, Incorporated) transvenous lead, a compatible Endotak DSP lead extender (Model 6952, Cardiac Pacemakers, Incorporated) and the above described ICD. Immediate relief of symptoms was accomplished by relocation of the device to an abdominal site. This intervention should be reserved for patients with severely debilitating symptoms. Prospective comparison of subpectoral and subcutaneous surgical approaches with respect to patient comfort and acceptance and complications may be warranted.

Retrograde fast pathway ablation for atrioventricular nodal reentry associated with markedly prolonged PR intervals

Three patients with typical atrioventricular nodal reentrant tachycardia (AVNRT) and markedly prolonged PR intervals (>300 ms) without dual pathway physiology at baseline or during isoproterenol infusion underwent successful fast pathway ablation and remained asymptomatic without recurrent AVNRT, atrioventricular block, or symptomatic bradycardia for a mean of 19 months. In patients with recurrent AVNRT and markedly prolonged PR intervals, selective ablation of the retrograde fast pathway can eliminate AVNRT without further impairment of anterograde atrioventricular nodal function.

Atrial fibrillation after radiofrequency ablation of type I atrial flutter: time to onset, determinants, and clinical course

BACKGROUND

The occurrence of atrial fibrillation after ablation of type I atrial flutter remains an important clinical problem. To gain further insight into the pathogenesis and significance of postablation atrial fibrillation, we examined the time to onset, determinants, and clinical course of atrial fibrillation after ablation of type I flutter in a large patient cohort.

METHODS AND RESULTS

Of 110 consecutive patients with ablation of type I atrial flutter, atrial fibrillation was documented in 28 (25%) during a mean follow-up of 20.1+/-9.2 months (cumulative probability of 12% at 1 month, 23% at 1 year, and 30% at 2 years). Among 17 clinical and procedural variables, only a history of spontaneous atrial fibrillation (relative risk 3.9, 95% confidence intervals 1.8 to 8.8, P=0.001) and left ventricular ejection fraction <50% (relative risk 3.8, 95% confidence intervals 1.7 to 8.5, P=0.001) were significant and independent predictors of subsequent atrial fibrillation. The presence of both these characteristics identified a high-risk group with a 74% occurrence of atrial fibrillation. Patients with only 1 of these characteristics were at intermediate risk (20%), and those with neither characteristic were at lowest risk (10%). The determinants and clinical course of atrial fibrillation did not differ between an early (< or = 1 month) compared with a later onset. Atrial fibrillation was persistent and recurrent, requiring long-term therapy in 18 patients, including 12 of 19 (63%) with prior atrial fibrillation and left ventricular dysfunction.

CONCLUSIONS

Atrial fibrillation after type I flutter ablation is primarily determined by the presence of a preexisting structural and electrophysiological substrate. These data should be considered in planning postablation management. The persistent risk of atrial fibrillation in this population also suggests a potentially important role for atrial fibrillation as a trigger rather than a consequence of type I atrial flutter.

The myths of emergency medical care access in the managed care era

In this paper, we examine the perception that emergency care is unusually expensive. We discuss the myths that have fueled the ineffective and sometimes deleterious efforts to limit access to emergency care. We demonstrate the reasons why these efforts are seriously flawed and propose alternate strategies that aim to improve outcomes, including cooperative ventures between hospitals and managed care organizations. We challenge managed care organizations and healthcare providers to collaborate and lead the drive to improve the cost and clinical effectiveness of emergency care.

Adenosine-sensitive bundle branch reentry

INTRODUCTION

Bundle branch reentry is an uncommon mechanism for ventricular tachycardia. More infrequently, both fascicles of the left bundle may provide the substrate for such macroreentrant bundle branch circuits, so-called interfascicular reentry. The effect of adenosine on bundle branch reentrant mechanisms of tachycardia is unknown.

METHODS AND RESULTS

A 59-year-old man with no apparent structural heart disease and history of frequent symptomatic wide complex tachycardias was referred to our center for further electrophysiologic evaluation. During electrophysiologic study, a similar tachycardia was reproducibly initiated only during isoproterenol infusion, which had the characteristics of bundle branch reentry, possibly using a left interfascicular mechanism. Intravenous adenosine reproducibly terminated the tachycardia. Application of radiofrequency energy to the breakout site from the left posterior fascicle prevented subsequent tachycardia induction and rendered the patient free of spontaneous tachycardia during long-term follow-up.

CONCLUSIONS

Patients with ventricular tachycardia involving a bundle branch reentrant circuit may be sensitive to adenosine. These results suggest that adenosine may not only inhibit catecholamine-mediated triggered activity but also some catecholamine-mediated reentrant ventricular arrhythmias.

Malpractice claims against emergency physicians in Massachusetts: 1975-1993

This study reviewed 549 malpractice claims filed against emergency physicians in Massachusetts from 1975 through 1993, with a total of $39,168,891 of indemnity and expense spent on the 549 closed claims. High-risk diagnostic categories (chest pain, abdominal pain, wounds, fractures, pediatric fever/meningitis, epiglottitis, central nervous system bleeding, and abdominal aortic aneurysm) accounted for 63.75% of all closed claims and 64.23% of the total indemnity and expense spent on closed claims. Missed myocardial infarction (chest pain) claims accounted for 25.47% of the total cost of closed claims but only 10.38% of closed claims. The number of claims for missed myocardial infarction increased in the post-1988 closed claim group compared to the pre-1988 group; fractures and wounds were significantly less frequent in the post-1988 group. The frequency of high-risk claims decreased in the post-1988 group, largely because of the decline in fracture and wound claims. The category of missed myocardial infarction had a larger percentage of claims closed with indemnity payment than without indemnity payment. This parameter may serve as a marker for the overall seriousness of claims associated with a particular allegation, unlike the average cost per claim, which may be skewed by a few large awards.

Atraumatic rupture of utero-ovarian vessels during pregnancy: a lethal presentation of maternal shock

Spontaneous rupture of utero-ovarian vessels during pregnancy is a rare cause of maternal and fetal loss. We report the case of a 30-year-old woman who presented to the emergency department in her third trimester with frank maternal shock. The prompt recognition of shock, correction of hypovolemia, and rapid surgical intervention by her obstetrician led to a favorable outcome for both mother and child.

Massachusetts emergency medicine closed malpractice claims: 1988-1990

STUDY PURPOSE

To describe the characteristics of malpractice claims against emergency physicians and to identify causes and potential preventability of such claims.

POPULATION

Malpractice claims closed in 1988, 1989, and 1990 against emergency physicians insured by the Massachusetts Joint Underwriters Association were compared with claims closed from 1980 to 1987 as investigated in our previous study.

METHODS

Retrospective review of malpractice claim files by board-certified emergency physicians.

RESULTS

The average indemnity and expense per claim were higher in the current study population than in our previous study population (P = .05). Claims in eight high-risk diagnostic areas (chest pain, abdominal pain, fractures, wounds, pediatric fever/meningitis, subarachnoid hemorrhage, aortic aneurysm, and epiglottitis) accounted for 50.8% of claims in this study and 55.5% of total monetary losses. Four claims in this study were related to two instances of failure of an emergency department radiograph follow-up system. The evaluation of patients who were intoxicated contributed to major monetary losses, especially in cases of fractures and head injury.

CONCLUSION

Emergency physicians must have a particular awareness of their great risk exposure for missed myocardial infarction. Addition of dictation or voice-activated record generation systems, departmental protocols for radiograph follow-ups, and holding and re-evaluation of the intoxicated patient will help provide systems supports for reducing the liability of individual emergency physicians.

Use of autopsy results in the emergency department quality assurance plan

Traditionally, the autopsy is viewed as the ultimate quality assurance indicator in clinical medicine, yet very few clinical departments actually incorporate autopsy results in their formal quality assurance plans. Consequently, to investigate how autopsy results can be included on our emergency department plan, the clinical and autopsy diagnoses of 244 patients were reviewed retrospectively and compared to identify conditions that were unapparent or misdiagnosed at the time of death. The study period was from January 1984 through June 1988. The average yearly ED census was 33,266. Differences between clinical and autopsy diagnoses were categorized as class 1, 2, 3, or 4 findings. Major unexpected findings (classes 1 and 2) were found in ten patients (4%); the most common missed diagnoses were aortic dissection 3 (1.2%) and pulmonary embolus 2 (0.8%). Minor unexpected findings (classes 3 and 4) were discovered in 14 patients (5.8%). The results clearly identify unexpected findings and point to the need for more aggressive evaluations of certain conditions. Systematic review of autopsy data as presented has led to meaningful changes and delivery of care to emergency patients. Autopsies are a vital source of outcome-based information that should be part of every ED's quality assurance and risk management plan.

Chemotherapy-induced painful acral erythema in childhood: Burgdorf's reaction

Painful acral erythema as a reaction to intensive chemotherapy has been increasingly recognized since 1982. It has not been reported in the pediatric literature. We report its occurrence in a 3-year-old boy who had received intensive chemotherapy for acute lymphoblastic leukemia.