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Bradley P Knight

Publications and source records attributed to Bradley P Knight.

At least 19 recordsLinked to original sources
PubMed2006

Rapid assessment of left ventricular systolic function in a pacemaker clinic using a hand-carried ultrasound device.

OBJECTIVE: Pacemaker recipients with left ventricular (LV) dysfunction are potential candidates for upgrades to implantable defibrillators or cardiac resynchronization devices. This study sought to determine if a hand-carried ultrasound (HCU) device could be used for rapid, inexpensive identification of LV dysfunction in a busy pacemaker clinic. MATERIALS AND METHODS: Eighty patients undergoing routine pacemaker check were enrolled. Patients underwent HCU imaging in the sitting position during device interrogation, by an internist who had 20 h of didactic training and 20 practice examinations. LV dysfunction was defined as ejection fraction (EF) <40%. Patients also underwent echocardiography limited to EF assessment by a sonographer using a full-feature platform. RESULTS: The mean age was 75 +/- 13 years; 49% were female. Coronary artery disease was present in 29%; 82% were NYHA class I or II. At the time of HCU imaging, 48% of patients were receiving RV pacing. HCU images were interpretable in 91% (73/80) and required 3.7 +/- 0.9 min to complete. Based on the full-feature echo, LV dysfunction prevalence was 17/80 (21%); 25% of these patients were NYHA class I. The sensitivity of the HCU exam was 75%, specificity was 91%, negative predictive value was 93%, positive predictive value was 71%, and accuracy was 88%. CONCLUSIONS: HCU screening in a pacemaker clinic by a non-cardiologist can rapidly and accurately identify pacemaker recipients with at least moderate LV dysfunction who might be candidates for device upgrades. Ventricular dyssynchrony associated with RV pacing does not limit HCU identification of LV dysfunction.

Aged↗
PubMed2006

Integration of cardiac imaging and electrophysiology during catheter ablation procedures for atrial fibrillation.

As nonpharmacologic therapies for atrial fibrillation expand, the complexity of the anatomical and electrical substrates of atrial fibrillation requires integration of multiple imaging modalities for successful treatment. Combining chamber-specific imaging and electrophysiologic data points during ablation therapy has improved pulmonary vein isolation accuracy while diminishing risk. Merging 3-dimensional computed tomography left atrial renditions, intracardiac echocardiography, and electroanatomical mapping during pulmonary vein isolation is a reality that relates the complex anatomy of the left atrium to its often variable electrical targets. Direct visualization of radiofrequency lesion formation as well as electrode-tissue contact during current delivery has been accomplished in animal models using ultrasound and infrared imaging tools. The combination of these early integrative stepping stones may lead to imaging with real-time feedback relating tissue desiccation to electrical effect and lesion transmurality. Atrial fibrillation ablation outcome will improve as the electrophysiology laboratory continues to integrate real-time 3-dimensional cardiac chamber and tissue images before, during, and after radiofrequency or cryoablation of specific electrophysiologic targets.

Atrial Fibrillation↗
PubMed2006

AHA/ACCF Scientific Statement on the evaluation of syncope: from the American Heart Association Councils on Clinical Cardiology, Cardiovascular Nursing, Cardiovascular Disease in the Young, and Stroke, and the Quality of Care and Outcomes Research Interdisciplinary Working Group; and the American College of Cardiology Foundation: in collaboration with the Heart Rhythm Society: endorsed by the American Autonomic Society.

Explore the source record for details and available documents.

Adult↗
PubMed2006

Prophylactic pacemaker use to allow beta-blocker therapy in patients with chronic heart failure with bradycardia.

BACKGROUND: Although the benefits of beta-blocker therapy for patients with congestive heart failure (CHF) are independent of pretreatment heart rate, patients with chronic systolic heart failure and low resting heart rates are often excluded from beta-blocker therapy. We investigated the effectiveness and cost-effectiveness of prophylactic pacemaker insertion to facilitate beta-blocker use in these patients. METHODS: A Markov model simulated the natural history of a cohort of clinically stable patients with CHF (ejection fraction < or = 35%, mean age 60 years) with resting heart rates of < 68 beat/min. Two strategies were evaluated: (1) conventional therapy (conventional)-the risks for death and hospitalization were derived from the angiotensin-converting enzyme inhibitor arm of the SOLVD treatment trial; and (2) pacemaker insertion with atrial pacing and carvedilol therapy (pacemaker-carvedilol)-risk reductions for death and CHF-related hospitalizations for carvedilol compared with conventional therapy were derived from the US Carvedilol Heart Failure Study. We assumed full carvedilol benefits for 2 years, declining benefits for the next 3 and no additional benefits after 5 years, whereas pacemaker-related adverse events persisted. RESULTS: In the base case, the pacemaker-carvedilol strategy increased mean survival by 1.3 years at an incremental cost of $7800, for an incremental cost-effectiveness of $6100 per year of life saved. Results were most sensitive to theoretical pacing-induced harm, changes in hospitalization cost, and reductions in beta-blocker benefits. CONCLUSION: Prophylactic pacemaker insertion to facilitate beta-blocker treatment in patients with CHF with low resting heart rates has the potential to produce clinical benefits in a highly cost-effective manner.

Adrenergic beta-Antagonists↗
PubMed2006

Disparities in the use of primary prevention and defibrillator therapy among blacks and women.

OBJECTIVES: This study determines whether there are racial or gender disparities in the use of implantable cardioverter-defibrillator therapy for primary prevention of sudden cardiac death. BACKGROUND: Primary prevention of sudden death with implantable cardioverter-defibrillator therapy has been shown to improve survival for high-risk patients with coronary artery disease and left ventricular dysfunction. METHODS: The Center for Medicare and Medicaid Services Medicare database from the year 2002 was used to identify patients who were potential candidates for implantable cardioverter-defibrillator therapy on the basis of a combination of International Classification of Diseases, Ninth Revision, Clinical Modification codes that reflected the presence of an ischemic cardiomyopathy. This cohort was analyzed to determine which patients received implantable cardioverter-defibrillator therapy during the same year. The clinical characteristics of the potential implantable cardioverter-defibrillator candidates were compared with those who actually received an implantable cardioverter-defibrillator. RESULTS: A total 132565 Medicare patients hospitalized during 2002 were identified as having an ischemic cardiomyopathy; 10370 (8%) of these patients underwent implantable cardioverter-defibrillator implantation during the same year. The percentage of patients who underwent implantable cardioverter-defibrillator implantation was higher for men compared with women (10.2% vs 3.5%; P<.001) and whites compared with blacks (8.1 vs 5.4; P<.001). After multivariate analysis, age, gender, and race remained independent predictors of implantable cardioverter-defibrillator implantation. Women with an ischemic cardiomyopathy were 65% less likely to receive implantable cardioverter-defibrillator therapy compared with men (P<.001), and black patients were 31% less likely to receive implantable cardioverter-defibrillator therapy compared with patients of other races (P < .001). CONCLUSIONS: Use of implantable cardioverter-defibrillator therapy for primary prevention of sudden death among the elderly population identified as having an ischemic cardiomyopathy was significantly lower among women compared with men, and among blacks compared with whites. Further exploration of gender and racial barriers to appropriate implantable cardioverter-defibrillator use for primary prevention is needed.

Black or African American↗
PubMed2006

Slow pathway ablation for atrioventricular nodal reentry using a right internal jugular vein approach: a case series.

BACKGROUND: Inferior venous access to the right heart is not possible in some patients due to congenital or acquired obstruction of the inferior vena cava (IVC). Although right-sided electrophysiology procedures have been performed successfully in patients with a previously placed IVC filter by direct placement of catheters through the filter, an alternative approach is necessary in some patients. METHODS: This case series describes three patients with an IVC filter who underwent successful ablation of the slow pathway for typical atrioventricular (AV) nodal reentrant tachycardia using a superior vena cava (SVC) approach via the right internal jugular (IJ) vein. Two separate introducer sheaths were placed into the IJ vein using separate punctures. This permitted placement of a standard deflectable ablation catheter and an additional catheter in the right atrium to monitor for ventriculoatrial conduction during the junctional rhythm associated with ablation of the slow AV nodal pathway. RESULTS: Catheter ablation was successful in each patient. The number of radiofrequency current applications was 7, 17, and 27. There were no procedural complications and no patient had recurrent tachycardia during follow-up. CONCLUSIONS: Catheter ablation of the slow AV nodal pathway can be performed successfully and safely in patients with inferior venous barriers to the right heart using an SVC approach via the right IJ vein.

Catheter Ablation↗
PubMed2006

Defibrillation energy requirements in an ICD population receiving cardiac resynchronization therapy.

OBJECTIVES: While defibrillation energy requirements (DERs) have been extensively studied in patients receiving conventional defibrillators, the DERs of patients receiving cardiac resynchronization therapy with defibrillation capability (CRT-D) devices have not been well described. The purpose of this analysis was to characterize DERs (defined as true threshold or the presence of appropriate safety margins) in patients undergoing implant of a CRT-D and to determine whether DERs in this population were similar to those reported for patients undergoing implantation of conventional defibrillators. METHODS: Data were analyzed retrospectively from the VENTAK CHF/CONTAK CD biventricular pacing study. An appropriate safety margin of at least 10 J was verified with at least two successful conversions with 21 J or less. Multivariate logistic regression was performed to determine baseline predictors of failed DER testing. RESULTS: Of 501 patients enrolled, 444 (89%) had successful DER test outcomes. Of the remaining 57 patients, 34 converted with energies > or = 21J, and 23 had their testing terminated prematurely or were not tested, primarily due to patient condition. Larger left ventricular internal dimension in diastole (P = 0.003) and prolonged procedure time (P = 0.01) were significant predictors of higher energy requirements. Few significant complications arose from DER testing. CONCLUSIONS: DER testing can be accomplished safely and successfully in the majority of CRT-D patients. However, safety margins cannot be ascertained in a significant number of these patients. Left ventricular inner diameter in diastole (LVIDd) and prolonged procedure time may predict higher DERs, and could be used to anticipate the need for a high-energy device or inclusion of a subcutaneous array.

Aged↗
PubMed2006

Predictors of appropriate defibrillator therapy among patients with an implantable defibrillator that delivers cardiac resynchronization therapy.

INTRODUCTION: The purpose of this study was to determine predictors of appropriate implantable defibrillator (ICD) therapy among patients with heart failure who are treated with a cardiac resynchronization therapy-defibrillator (CRT-D). METHODS AND RESULTS: Patients enrolled in the Ventak CHF/Contak CD study were treated with a CRT-D device and were required to have NYHA class II-IV CHF, QRS duration > or = 120 msec, and a class I or II indication for an ICD. The study database was retrospectively analyzed during the 6-month postimplant period to identify predictors of appropriate ICD therapy. Five hundred and one of the 581 patients enrolled in the trial had successful device implantation and were included in this analysis. Patients were mostly male (83%), 66 +/- 11 years old, and had coronary artery disease (69%), a mean left ventricular ejection fraction (EF) = 0.22 +/- 0.07, and NYHA class II (33%), III (58%), or IV (9%) CHF symptoms. During 6 months of follow-up, 73 of 501 (14%) patients received an appropriate ICD therapy. Two independent predictors of appropriate therapy were identified: a history of a spontaneous, sustained ventricular arrhythmia (HR = 2.05; 95% CI = 1.31-3.20; P = 0.002) and NYHA class IV CHF (HR = 1.81; 95% CI = 1.10-2.96; P = 0.019). When patients with NYHA class II were excluded from analysis, a history of a sustained ventricular arrhythmia and the presence of NYHA class IV CHF symptoms remained as independent predictors of appropriate ICD therapy. CONCLUSIONS: In a select population of advanced heart failure patients receiving a CRT-D, NYHA class IV CHF was a powerful independent predictor of appropriate ICD therapy. Approximately one-quarter of the patients with NYHA class IV CHF who received a CRT-D device received an appropriate ICD therapy within 3 months after implant. Additional studies are needed to confirm an association between class IV CHF symptoms and an increased frequency of ICD shocks.

Aged↗
PubMed2006

Imaging techniques in cardiac electrophysiology.

Modern cardiac electrophysiology procedures include catheter-based arrhythmia ablation and transvenous device implantation, which are highly dependent on accurate, real-time cardiac imaging. With the realization that anatomic structures are critical to successful electrophysiologic procedures, accurately defining a patient's cardiac anatomy has become more important. Fluoroscopy allows for 2D imaging of cardiac structures in real-time, and is used to guide catheter and lead placement, but does not allow for visualization of soft tissues. Intracardiac echocardiography allows for both direct visualization of anatomic structures within the heart and real-time imaging during catheter placement. Despite advances in intracardiac echocardiography catheters that allow for larger windows, the ability to accurately delineate anatomic structures depends on the patient's anatomy and operator experience. Neither of these techniques allows for electrical mapping of the heart; however, both anatomic and electrical intracardiac mapping can be achieved with advanced mapping systems. These systems allow for real-time catheter localization, help elucidate cardiac anatomy, evaluate electrical activation during arrhythmias and guide catheter placement for deliverance of radiofrequency current. More recently, 3D cardiac computed tomography has been used to accurately define intracardiac anatomy; however, catheter tracking and electrical mapping cannot be performed by computed tomography. Mapping systems are now being merged with computed tomography images to produce an accurate anatomic and electrical map of the heart to guide catheter ablations. The objective of this paper is to describe the current imaging and mapping techniques used in electrophysiologic procedures.

Body Surface Potential Mapping↗
PubMed2005

Role of permanent pacing to prevent atrial fibrillation: science advisory from the American Heart Association Council on Clinical Cardiology (Subcommittee on Electrocardiography and Arrhythmias) and the Quality of Care and Outcomes Research Interdisciplinary Working Group, in collaboration with the Heart Rhythm Society.

This advisory summarizes the current database on pacing modalities and algorithms used to prevent and terminate atrial fibrillation (AF). On the basis of the evidence indicating that ventricular pacing is associated with a higher incidence of AF in patients with sinus node dysfunction, a patient who has a history of AF and needs a pacemaker for bradycardia should receive a physiological pacemaker (dual chamber or atrial) rather than a single-chamber ventricular pacemaker. For patients who need a dual-chamber pacemaker, efforts should be made to program the device to minimize the amount of ventricular pacing when atrioventricular conduction is intact. Many pacemakers and implantable defibrillators have features designed to prevent AF and to terminate AF with rapid atrial pacing. The evidence to support their use is limited, although these algorithms appear to be safe and usually add little additional cost. For patients who have a bradycardia indication for pacing and also have AF, no consistent data from large randomized trials support the use of alternative single-site atrial pacing, multisite right atrial pacing, biatrial pacing, overdrive pacing, or antitachycardia atrial pacing. Even fewer data support the use of atrial pacing in the management of AF in patients without symptomatic bradycardia. At present, permanent pacing to prevent AF is not indicated; however, additional studies are ongoing, which will help to clarify the role of permanent pacing for AF.

Algorithms↗
PubMed2005

Direct visualization of coronary sinus ostium and branches with a flexible steerable fiberoptic infrared endoscope.

BACKGROUND: Placement of electrophysiology catheters and pacing leads in the coronary sinus is challenging in some patients, particularly those with dilated cardiomyopathy. We hypothesized that cannulation of the coronary sinus and its branches can be facilitated by direct visualization. This study reports our experience with navigation into and within the coronary sinus in a closed-chest animal preparation, using a flexible steerable fiberoptic infrared endoscope that allows visualization through flowing blood. OBJECTIVES: The purpose of this study was to assess the feasibility of direct visualization of endocardial structures through infrared endoscopy. METHODS: Internal jugular venous access was obtained in 10 healthy mongrel dogs (weight 35-45 kg). The infrared endoscope (2900 fiber imaging bundle, wavelength 1,620 nm, frame rate 10-30/s, 320 x 256 pixels) was advanced to the coronary sinus ostium and branches by direct visualization of anatomic landmarks, such as the tricuspid valve and inferior vena cava. Localization was confirmed by fluoroscopy, contrast injection, and pathologic examination. RESULTS: Structures such as the tricuspid valve and inferior vena cava were visualized at distances of 1 to 2 cm, allowing successful coronary sinus identification and engagement in all 10 dogs. Coronary sinus branch images closely resembled pathologic findings. CONCLUSION: Direct visualization of the coronary sinus ostium and branches is possible through infrared endoscopy. This technique likely will facilitate coronary sinus engagement and navigation for pacing lead and catheter placement.

Angioscopy↗
PubMed2005

Direct imaging of transvenous radiofrequency cardiac ablation using a steerable fiberoptic infrared endoscope.

BACKGROUND: Direct imaging through blood has been achieved in vivo using fiberoptics and infrared wavelength technology. OBJECTIVES: The purpose of this study was to determine the feasibility of using a percutaneous, steerable, fiberoptic infrared endoscope to identify and characterize the electrode-tissue interface during transvenous cardiac ablation. METHODS: Infrared endoscopy was performed during 24 catheter ablation attempts in 10 mongrel dogs. Infrared imaging was performed through a transparent dome located at the tip of a 7Fr steerable endoscope using an imaging wavelength of 1,620 nm. Radiofrequency ablation was performed using a 4-mm-tip electrode catheter. Attempts were made to identify the electrode-endocardial interface at each ablation site and to characterize any signal changes during ablation. RESULTS: The electrode-tissue interface could be identified at 19 of the 24 ablation sites. Changes at the electrode-tissue interface were observed during ablation at 14 sites, which included a gradual increase in the tissue signal intensity at 12 sites. Small lucencies near the ablation electrode were observed at six sites. There was no interference during energy delivery. Endocardial features identified by endoscopy correlated with the postmortem appearance. CONCLUSION: Direct imaging of intracardiac structures and the electrode-tissue interface can be achieved through blood during transvenous catheter ablation with infrared endoscopy using a steerable, fiberoptic, infrared endoscopic catheter. Ablation lesion formation can be seen as a gradual increase in signal intensity. Fiberoptic infrared endoscopy appears to be a promising new tool for guiding catheter ablation.

Animals↗