William Barrington

Fluoroscopic Screening of Asymptomatic Patients Implanted With the Recalled Riata Lead Family

Background— The Food and Drug Administration recently issued a class I recall of the St. Jude Medical Riata implantable cardioverter-defibrillator lead presumably because of increased risk of electric failure and mechanical separation via inside-out abrasion. We sought to examine the incidence and time dependence of inside-out abrasion in asymptomatic patients implanted with the Riata lead. Methods and Results— Asymptomatic patients implanted with the Riata lead at our institution were offered voluntary fluoroscopic screening in 3 views. Electric testing of the Riata lead with provocative isometric muscle contraction was performed at the time of fluoroscopic screening. Of the 245 patients undergoing fluoroscopic screening, 53 (21.6%) patients showed clear evidence of lead separation. Of these externalized leads, 0%, 13%, and 26% had a dwell time of <3 years, 3 to 5 years, and >5 years, respectively (P=0.037). Externalized leads had a significantly pronounced decrease in R-wave amplitude (−1.7±2.9 mV versus +0.35±2.5 mV; P<0.001), and more patients with externalized leads had ≥25% decrease in R-wave amplitude from baseline (28.0% versus 8.1%; P=0.018). One patient with externalization exhibited new noise on near-field electrogram. Conclusions— The Riata lead exhibits time-dependent high rates of cable externalization exceeding 20% at >5 years of dwell time. Externalized leads are associated with a more pronounced decrease in R-wave amplitude, which may be an early marker of future electric failure. The use of fluoroscopic and electric screening of asymptomatic patients with the Riata lead remains controversial in the management of patients affected by the recent Food and Drug Administration recall.

Selected patients listed for cardiac transplantation may benefit from defibrillator implantation regardless of an established indication.

BACKGROUND End-stage heart failure (HF) patients are at high risk of sudden cardiac death. This study evaluates the role of implantable cardiac defibrillators (ICDs) in HF patients awaiting cardiac transplantation. METHODS We identified 194 consecutive patients (age 51 +/- 12 years) with New York Heart Association Class 3 or 4 HF (ejection fraction 22 +/- 9%) listed for cardiac transplantation, 35 of whom underwent ICD implantation. Of the implanted patients, 16 (Group A) had an established indication for ICD implantation (cardiac arrest, n = 10; sustained ventricular tachycardia [VT], n = 3; and positive electrophysiology study, n = 3). Nineteen patients (Group B) underwent ICD implantation for non-established indications (syncope with non-ischemic cardiomyopathy, n = 4; non-sustained VT, n = 15). There were no procedural complications from ICD implantation. RESULTS During follow-up of 9.2 +/- 10.1 months, there were 3 deaths in the ICD groups (A and B), and 40 in the control group (8.6% vs 25.2%, p = 0.032). Five patients in Group A and 6 in Group B (31%) received appropriate ICD therapy. The number of therapies per patient and the time to the first shock were similar between Groups A and B. Four of 6 Group B patients on outpatient inotropic therapy (67%) received appropriate ICD therapy. CONCLUSIONS Selected end-stage heart failure patients awaiting heart transplantation, including those without established ICD indications, are at high risk for malignant arrhythmias and may benefit from ICD implantation. Patients with ICD seem to have improved survival compared to those without ICD. Randomized prospective studies are needed to confirm these findings.

Complications of replacing implantable devices in response to advisories: A single center experience

BACKGROUND Advisories for implanted devices present a challenging management problem since no specific guidelines exist for device replacement under these circumstances. Since the rate and severity of complications is an important factor in the decision-making, we sought to review our experience with replacement of devices under advisory. METHODS Medical records of patients with devices under advisory were reviewed. A total of 237 patients (age 68+/-13 years, men 71%, implantable cardioverter-defibrillator (ICD) 87%) underwent device replacement in response to advisories (Medtronic Inc. 43% and Guidant Inc. 57%) at our institution between February 2005 and June 2006. RESULTS The mean time from original device implantation to replacement was 31+/-16 months (3-73 months). During a mean follow-up of 198+/-103 days, there was a 5.5% overall rate of complications related to the procedure. Major complications requiring re-operation affected 2.1% of patients. There were no deaths associated with device replacement. Device failure prior to replacement was documented in 1.7% of patients, with syncope occurring in one patient. A history of diabetes mellitus (23%), peripheral vascular disease (4%), obstructive lung disease (7%), end-stage renal disease (2%), or use of anticoagulation (44%) did not predict the occurrence of complications after advisory device replacement. CONCLUSION This single center experience shows a lower major complication rate from replacement of devices under advisory than previously reported. Experience from this center and others may be useful in guiding future management of patients in the setting of device advisories.

Frequency of Toxicity With Chemical Conversion of Atrial Fibrillation With Dofetilide

Dofetilide is a class III antiarrhythmic agent approved for the maintenance of sinus rhythm in patients with persistent atrial fibrillation (AF). The goal of this study was to determine if chemical cardioversion (CCV) suggests a greater sensitivity to dofetilide and, therefore, portends a higher risk of proarrhythmia. We analyzed 99 consecutive patients with persistent AF who were loaded on dofetilide before cardioversion. CCV occurred after 2 ± 1.5 doses of dofetilide in 46 patients whereas electrical cardioversion (ECV) was required in the remaining 53 patients after 4.7 ± 1.3 doses. During index hospitalization, there were higher rates of dofetilide discontinuation because of QT prolongation or torsades de pointes (TdP) in the CCV group compared with the ECV group (24% vs 2%, p = 0.001). All patients with CCV requiring drug discontinuation converted after a single dose of dofetilide. Additionally, all 3 patients with TdP were in the CCV group. Furthermore, 15 of the 21 patients with CCV (71%) who converted after the first dose of dofetilide developed significant QT prolongation, requiring dose adjustment or discontinuation of drug. Among patients discharged on drug, AF recurrence and drug discontinuation rates were similar between groups at 2-year follow-up. In patients hospitalized for initiation of dofetilide, CCV occurs in almost 50% and is associated with higher rates of pathologic QT prolongation and TdP compared with those who require ECV. Once discharged on dofetilide, safety and efficacy is similar in both groups. In conclusion, patients with CCV may require closer monitoring for proarrhythmia.

Wide and Narrow Complex Tachycardias: What Is the Mechanism?

December 2001 PACE, Vol. 24 A 49-year-old woman was referred for electrophysiological testing and radiofrequency catheter ablation of recurrent episodes of palpitations of a 10-year duration. The patient had typically been able to terminate the episodes of palpitations with vagal maneuvers until recent months, when they increased in frequency and severity. A 24-hour Holter monitor test showed frequent runs of wide and narrow complex tachycardias, with a recurring pattern of wide complex leading to narrow complex tachycardia of slightly faster rate (Fig. 1). The patient had a full cardiac workup for atypical chest pain and palpitations that included normal stress-thallium test and echocardiogram. During the electrophysiological study, the patient was in sinus rhythm with normal atrio-His (AH) and His-ventricular (HV) intervals of 75 and 50 ms, respectively. The atrioventricular nodal (AVN) Wenckebach cycle length (CL) was 330 ms and the AVN effective refractory period was 200 ms at a drive CL of 600 ms. Ventriculoatrial conduction was observed and the retrograde effective refractory period was 360 ms at a drive CL of 600 ms. With premature atrial stimulation, discontinuous A2H2 versus A1A2 curve was demonstrated. Isoproterenol infusion produced spontaneous runs of wide complex tachycardia that changed into a narrow complex tachycardia at a slightly faster rate. This phenomenon was very reproducible and similar to what was documented on the Holter monitor. What are the mechanisms of the wide and narrow complex tachycardias?

Mitral stenosis: mitral dome excursion at M1 and the mitral opening snap ― the concept of reciprocal heart sounds

The dynamics of the delayed accentuated mitral component (M1) of the first heart sound and the MOS were studied in 11 patients with mitral stenosis of varying severity. Echophonocardiographic (M-mode and 2D) studies were performed with analysis of LA dimensions, dynamics, and mitral valve excursion at the time of M1 and MOS. LA area and length, mitral annular diameter, and mitral dome area (from anulus plane to fused valve tip) and length were measured at M1 and MOS. Significant dynamic increases in mitral dome area and length occurred from M1 to MOS, with less striking but consistent increases in LA area, LA length, and mitral annular diameter. Conversely, mitral dome area and length decreased significantly from MOS to M1, with less striking but consistent decreases in LA area, LA length, and mitral annular diameter. Frame-by-frame video tape analysis showed that dome movement was separate from anulus motion. Mitral dome descent into the left ventricle terminated at MOS and reversal of dome motion terminated at M1. The conformational and dimensional changes that terminated abruptly at MOS reversed and terminated abruptly in a reciprocal manner at the time of the delayed, accentuated M1. When considered in light of known hemodynamic, pressure pulse, and imaging correlates in mitral stenosis, these observations strengthen the hypothesis that the mechanisms involved in the production of M1 and MOS in mitral stenosis are paired or reciprocal in nature, and the delayed, accentuated M1 and the MOS of mitral stenosis are reciprocal cardiovascular sounds.

Optimal Implantable Cardioverter Defibrillator (ICD) Generator Replacement

Implantable cardioverter defibrillators (ICDs) include small, battery-powered generators, the longevity of which depends on a patients rate of consumption. Generator replacement, however, involves risks, including death. Hence, a trade-off exists between prematurely exposing the patient to these risks and allowing for the possibility that the device is unable to deliver therapy when needed. Currently, replacements are performed using a one-size-fits-all approach. Here, we develop a Markov decision process model to determine patient-specific optimal replacement policies as a function of patient age and the remaining battery capacity. We analytically establish that the optimal policy is of threshold-type in the remaining capacity, but not necessarily in patient age. Based on clinical data, we conduct a large computational study that suggests that under the optimal policy, patients undergoing initial implantation at age 30--40, 41--60, and 61--80 see an approximate decrease in the total expected number of replacements of 8%--14%, 8%--15% and 8%--19%, respectively, while achieving the same or greater expected lifetime.

A novel manoeuvre for discerning supraventricular tachycardia mechanism.

AIMS Discerning supraventricular tachycardia (SVT) mechanism during catheter ablation procedures can be difficult and time-consuming, which, when combined with diagnostic error, places patients at risk of unnecessary complications. Distinguishing atrial tachycardia (AT) from AV nodal re-entry tachycardia (AVNRT) may be particularly vexatious. Value-added techniques are thus always welcome, particularly if they are not time-consuming nor require complex intracardiac lead configurations. In this study, we assessed whether a new technique, simultaneous right atrial and right ventricular pacing (RA + RV) during ongoing SVT, met these criteria. METHODS AND RESULTS Using a simple intracardiac lead configuration (right atrial appendage, His bundle, right ventricular apex), the response to RA + RV delivered at 80-90% of the SVT cycle length, was examined in 80 patients referred for catheter ablation. In each patient, the actual tachycardia mechanism was adjudicated by standard electrophysiologic criteria ± successful catheter ablation. Mechanisms of SVT included, non-exclusively, AVNRT (24 patients), accessory pathway-mediated (orthodromic) re-entry (AVRT; 23 patients), AT (10 patients), and sinus tachycardia (ST induced with isoproterenol; 49 patients). Immediately after cessation of RA + RV pacing during persistent SVT, the first intracardiac electrogram observed was right atrial in all AT whereas it was His bundle in all AVNRT. The response during AVRT was mixed. CONCLUSIONS In this preliminary evaluation, RA + RV pacing appears to add value to the existing armamentarium of electrophysiologic indices to discern SVT mechanism, in particular with respect to discriminating between AVNRT and AT.

An unusual defibrillator lead-associated echodensity.

A 62-year-old woman with nonischemic cardiomyopathy underwent the prophylactic implantation of a single-chamber implantable cardioverter-defibrillator. The first rib extrathoracic axillary vein approach under fluoroscopic guidance was used for vascular access. The system comprised a model 6935 single-coil lead and a model D314DRG generator (Medtronic, Minneapolis, MN). The lead was implanted in the right ventricular apex and was affixed to the pectoral tissue by using a suture sleeve in the usual fashion. One year later, transthoracic echocardiography was performed for the evaluation of malaise and worsening dyspnea on exertion. It revealed the presence of a mobile echodensity associated with the lead in the vicinity of the tricuspid valve, suspective of vegetation or thrombus. Subsequent transesophageal echocardiography showed similar findings (Figure 1 and

Heart Failure and Pulmonary Embolism

Figure 1. Posteroanterior view of the patient’s chest Xray performed 6 months after the pacemaker implantation. The white arrow points to the position of the left ventricular pacing lead upon presentation to the hospital with shortness of breath. orubicin cardiac toxicity presented to the hospital with a one-week history of increasing shortness of breath, dyspnea on exertion, and lower extremity edema. The patient’s past medical history is significant for Hodgkin’s disease diagnosed in the year 2000, currently in remission, severe dilated cardiomyopathy with a left ventricular ejection fraction of 15%, status-post biventricular permanent pacemaker (InSync III Model 8042, Medtronic, Minneapolis, MN USA) implantation in July 2003.