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Biomedical subjects

Anne M Gillis

Publications and source records attributed to Anne M Gillis.

At least 19 recordsLinked to original sources
PubMed2006

The pacemaker and implantable cardioverter defibrillator recall issue - a Canadian perspective.

In 2005, an unprecedented number of recalls were issued on pacemakers and implantable cardioverter defibrillators. While recalls in the cardiac rhythm device industry are not new, the sheer magnitude of potentially affected patients in 2005 led to a great deal of concern, frustration, and even anger. Physicians have, in many instances, been uncertain when (or if) to recommend device replacement in an environment where the magnitude of the risk and the potential consequences of device failure have not been well defined in a timely way. Doctors and patients are now calling for reform of postmarket analysis and reporting mechanisms. The present article provides a uniquely Canadian perspective on this international issue. Potential solutions include the development of a set of realistic and common expectations, a restoration of confidence in postmarket analysis and reporting mechanisms, increased data transparency, and an increased role for patient and physician groups.

Canada↗
PubMed2006

A novel, simple scale for assessing the symptom severity of atrial fibrillation at the bedside: the CCS-SAF scale.

BACKGROUND: The severity of symptoms caused by atrial fibrillation (AF) is extremely variable. Quantifying the effect of AF on patient well-being is important but there is no simple, commonly accepted measure of the effect of AF on quality of life (QoL). Current QoL measures are cumbersome and impractical for clinical use. OBJECTIVE: To create a simple, concise and readily usable AF severity score to facilitate treatment decisions and physician communication. METHODS: The Canadian Cardiovascular Society (CCS) Severity of Atrial Fibrillation (SAF) Scale is analogous to the CCS Angina Functional Class. The CCS-SAF score is determined using three steps: documentation of possible AF-related symptoms (palpitations, dyspnea, dizziness/syncope, chest pain, weakness/fatigue); determination of symptom-rhythm correlation; and assessment of the effect of these symptoms on patient daily function and QoL. CCS-SAF scores range from 0 (asymptomatic) to 4 (severe impact of symptoms on QoL and activities of daily living). Patients are also categorized by type of AF (paroxysmal versus persistent/permanent). The CCS-SAF Scale will be validated using accepted measures of patient-perceived severity of symptoms and impairment of QoL and will require 'field testing' to ensure its applicability and reproducibility in the clinical setting. CONCLUSIONS: This type of symptom severity scale, like the New York Heart Association Functional Class for heart failure symptoms and the CCS Functional Class for angina symptoms, trades precision and comprehensiveness for simplicity and ease of use at the bedside. A common language to quantify AF severity may help to improve patient care.

Atrial Fibrillation↗
PubMed2006

Electrosurgery in patients with pacemakers/implanted cardioverter defibrillators.

Despite improved protective mechanisms, pacemakers and implanted cardioverter defibrillators are subject to interference from various sources. An effective means of hemostasis, electrocautery generates electromagnetic interference and may be problematic in this patient population. Reported complication rates are low, but the consequences can be serious. Recommendations regarding the management of patients with implanted cardiac devices become increasingly significant both as the number of patients with devices increases and the number of out-of-hospital/minor surgery procedures performed increases. This article provides surgeons and anesthetists with practical recommendations for use of electrocautery in patients with pacemakers or implantable cardiac defibrillators.

Defibrillators, Implantable↗
PubMed2006

Reducing unnecessary right ventricular pacing with the managed ventricular pacing mode in patients with sinus node disease and AV block.

BACKGROUND: Frequent and unnecessary right ventricular apical pacing increases the risk of atrial fibrillation or congestive heart failure. We evaluated a new pacing algorithm, managed ventricular pacing (MVP) which automatically changes modes between AAI/R and DDD/R in patients receiving pacemakers for symptomatic bradycardia. METHODS: Patients were randomized to the MVP mode or DDD/R mode for 1 month and then crossed over to the alternate pacing modality for an additional month. On completion of the crossover phase, the pacing mode selected was individualized and patients were followed for an additional 4 months. RESULTS: Of the 129 patients who successfully completed the crossover study, the cumulative percent ventricular pacing was significantly reduced in the MVP mode (median 1.4%) compared to the DDD/R mode (median 89.6%, 94.0% relative reduction; 95% CI 89.3-98.8%, P < 0.001). Patients with sinus node disease (SND, n = 51) when compared to patients with AV block (AVB) (n = 68) experienced a greater reduction in ventricular pacing with the MVP mode compared to the DDD/R mode (median relative reduction 99.1%; 95% CI 97.5-99.9% vs median relative reduction 60.1%; 95% CI 16.7-93.9% P < 0.001). The reduced percent ventricular pacing during MVP was sustained over longer term follow-up. CONCLUSIONS: The majority of patients with a bradycardia indication for cardiac pacing do not require ventricular pacing most of the time. The MVP mode significantly reduces unnecessary right ventricular pacing. This mode benefits even patients with intermittent AVB and is sustained over longer term follow-up.

Aged↗
PubMed2005

Controversies in pacing: indications and programming.

This article reviews controversies in cardiac pacing in four areas: methods to prevent unnecessary right ventricular pacing and optimal ventricular pacing sites in the bradycardia population, pacing for prevention of atrial fibrillation (AF), a novel pacing technique for the treatment of heart failure, and pacing for the treatment of sleep apnea. Frequent right ventricular pacing has been reported to increase the incidence of AF and congestive heart failure. However, many patients with pacemakers for bradycardia have intrinsic atrioventricular conduction most of the time. Optimal programming of pacemakers and new algorithms designed to reduce unnecessary ventricular pacing are discussed. Pacing algorithms for prevention of AF have generally been shown to be ineffective. Atrial antitachycardia pacing has been shown to reduce the burden of atrial tachyarrhythmias in selected patients. Cardiac contractility modulation has recently been reported to be a promising new approach to the treatment of heart failure. Some pacing techniques may be effective in the treatment of sleep apnea but larger, long-term clinical trials are required to demonstrate a significant clinical benefit.

Atrial Fibrillation↗
PubMed2005

High atrial antitachycardia pacing therapy efficacy is associated with a reduction in atrial tachyarrhythmia burden in a subset of patients with sinus node dysfunction and paroxysmal atrial fibrillation.

BACKGROUND: Atrial tachycardia (AT) and atrial flutter that occur in association with paroxysmal atrial fibrillation (AF) can be successfully terminated by antitachycardia pacing (ATP) therapy. We hypothesized that atrial ATP therapy reduces AT/AF burden in a subset of patients with symptomatic bradycardia and frequent paroxysmal AT/AF. OBJECTIVES: This study evaluated the effect of atrial ATP therapy on AT/AF burden in a pacemaker population with paroxysmal AF. METHODS: We compared AT/AF burden in 261 patients who received a Medtronic AT500 pacemaker for treatment of AT/AF in the setting of symptomatic bradycardia based on device-classified atrial ATP efficacy < 60% and > or = 60%. Patients with > or = 10 device-detected episodes of AT/AF before and after atrial ATP therapy initiation were identified from four clinical studies performed in 72 centers worldwide. RESULTS: The high efficacy group comprised 75 patients with atrial ATP efficacy > or = 60%. The low efficacy group comprised 186 patients with atrial ATP efficacy < 60%. AT/AF episode frequency was similar in both groups prior to ATP activation and decreased in the low efficacy group following ATP activation. Following atrial ATP initiation, total AT/AF burden increased slightly in the low ATP efficacy group (median 2.77 [25th-75th percentiles 0.84-5.86] hours/day vs 2.92 [0.59-8.12] hours/day, P = .01). In contrast, total AT/AF burden decreased significantly in the high efficacy group (median 2.46 [0.29-8.88] hours/day vs 0.68 [0.13-2.97] hours/day, P < .001). CONCLUSION: Up to 30% of patients with frequent episodes of paroxysmal AF and symptomatic bradycardia experience a reduction in AT/AF burden from atrial ATP therapy over time.

Aged↗
PubMed2005

Referring patients for consideration of device treatment of sudden cardiac death and heart failure: incorporating evidence-based therapies within the Canadian health care system.

The growing use of the implantable cardioverter defibrillator (ICD) in Canada reflects the impact that primary and secondary prevention trials have had in demonstrating the superiority of the ICD over medical therapy in the prevention of sudden cardiac death in high-risk populations. Currently, there are significant regional disparities in ICD implantation in Canada. These disparities may reflect a lack of regional ICD implant and follow-up programs, and capping of funding for ICDs. In addition to increased funding for ICD systems, more resources are required to perform device implantations and follow patients over the long-term. Potentially eligible patients should be referred to an electrophysiologist for consideration of ICD therapy for the prevention of sudden cardiac death or to an electrophysiologist/ heart failure specialist for the consideration of combination cardiac resynchronization and ICD therapy for the management of refractory heart failure.

Canada↗
PubMed2005

Pacing for the prevention of atrial fibrillation.

Multiple randomized clinical trials have demonstrated that atrial or dual-chamber pacing prevents paroxysmal and permanent atrial fibrillation (AF) in patients with symptomatic bradycardia as the primary indication for cardiac pacing. The benefit of atrial pacing for the prevention of AF is observed predominantly in patients with sinus node dysfunction. Emerging evidence also suggests that the risk of AF is directly linked to the proportion of time that ventricular pacing occurs. Consequently, pacemakers should be programmed to minimize the amount of ventricular pacing in patients with intrinsic atrioventricular conduction. Temporary atrial pacing following heart surgery may be of benefit for the prevention of perioperative AF. Atrial pacing has not been shown to prevent AF in patients without symptomatic bradycardia. In addition, selective pacing algorithms designed to prevent AF have minimal or no incremental benefits for the prevention of AF. At present, the role of selective atrial lead site(s) for the prevention of AF remains uncertain.

Algorithms↗
PubMed2005

Therapies for the prevention of stroke and other vascular events in atrial fibrillation and atrial flutter.

Stroke is the major clinical cause of atrial fibrillation (AF). Treatments to reduce the risk of stroke and other vascular events are an important part of AF management. Oral anticoagulation is effective against stroke and has an acceptable risk of adverse events (primarily bleeding). Acetylsalicylic acid is less effective than oral anticoagulants but better tolerated. Anticoagulants are recommended for AF patients with risk factors for stroke.

Atrial Fibrillation↗
PubMed2004

Heart block in mice overexpressing calcineurin but not NF-AT3.

OBJECTIVE: Overexpression of calcineurin causes cardiac hypertrophy and arrhythmic deaths. During disease development, sinus bradycardia followed by high degree atrioventricular (AV) block finally culminating in ventricular asystole has been observed over time in calcineurin hearts. AV block is associated with the development of pleomorphic ventricular tachycardia in mice and downregulation of potassium currents in ventricular myocytes. We tested the hypothesis that the abnormalities of AV block and propensity to ventricular tachycardia relate to overexpression of calcineurin independent of the development of hypertrophy. METHODS: Cardiac electrophysiologic properties were compared in isolated perfused hearts with ventricular hypertrophy due to overexpression of calcineurin or NF-AT3 and in their corresponding wild types at 15 or 30 days of age. RESULTS: Compared to wild-type hearts, significant prolongation of sinus node recovery times was noted in both NF-AT3 and calcineurin hearts. Compared to wild-type hearts, Wenckebach cycle length (WCL) and the left ventricular effective refractory period (LVERP) were significantly prolonged in the calcineurin hearts (p<0.05) but not NF-AT3 hearts. In calcineurin mice, left ventricular effective refractory period impinged on Wenckebach cycle length resulting in a significant correlation between left ventricular effective refractory period and Wenckebach cycle length (r(2)=0.56). No such correlation was observed for wild type or NF-AT3 hearts. At 30 days of development, ventricular tachycardia developed in 70% of calcineurin hearts compared to 0% wild-type hearts (p=0.003), whereas ventricular tachycardia was observed in 33% of NF-AT3 hearts and 10% of corresponding wild-type hearts (p=NS). CONCLUSIONS: The prolonged ventricular refractoriness, seen only in calcineurin hearts, impinges on Wenckebach cycle length resulting in heart block and is associated with propensity to ventricular tachycardia.

Animals↗
PubMed2004

Canadian Trial of Physiological Pacing: Effects of physiological pacing during long-term follow-up.

BACKGROUND: The Canadian Trial of Physiological Pacing (CTOPP) reported that the risk of stroke or cardiovascular death was similar between patients receiving ventricular versus physiological pacemakers at the end of the original follow-up period of 3 years. However, the occurrence of atrial fibrillation was significantly less frequent with physiological pacemakers. To assess a potential delayed benefit of physiological pacing, follow-up of patients in this study was extended to 6 years. METHODS AND RESULTS: A total of 1474 patients requiring a pacemaker for symptomatic bradycardia were randomized to receive ventricular and 1094 to physiological pacemakers. The primary outcome was stroke or cardiovascular death. The study was completed in July 1998, and follow-up was extended to July 2001. At a mean follow-up of 6.4 years, there was no difference between treatment groups in the primary outcome of cardiovascular death or stroke. There was no significant difference in total mortality or stroke between groups. There was a significantly lower rate of development of atrial fibrillation in the physiological group, with a relative risk reduction of 20.1% (CI, 5.4 to 32.5; P=0.009). CONCLUSIONS: The CTOPP extended study does not show a difference in cardiovascular death or stroke, or in total mortality, or in stroke between patients implanted with ventricular or physiological pacemakers over a mean follow-up of >6 years. However, there is a persistent significant reduction in the development of atrial fibrillation with physiological pacing.

Atrial Fibrillation↗
PubMed2004

Rhythm control in atrial fibrillation: endpoints for device-based trials.

Newer generations of pacemakers and implantable cardioverter defibrillators have enhanced diagnostic features that permit detection and storage of information about the frequency, duration, time of onset, and rate characteristics of multiple consecutive episodes of atrial tachycardia and atrial fibrillation (AF). Parameters available in implantable devices that might serve as outcome measures to assess the impact of pharmacologic and nonpharmacologic therapies for prevention of AF include time to first recurrence of AF, intervals between successive episodes of AF, AF frequency, AF duration, AF burden (amount/unit time), and episodes of symptomatic AF. Each parameter has advantages and limitations. The characteristics/temporal patterns of AF may determine the ideal study outcome measure to address a specific hypothesis. Clinical studies of therapies for prevention of AF need to be directed to populations with the arrhythmia substrate that will be targeted by the therapy. Device-based metrics are suitable to assess the impact of pacing or pharmacologic therapies for prevention of AF. However, it is important to establish that suppression of AF is associated with an improvement in some clinical outcome. Relevant outcomes might include improvement in symptoms, quality of life, or functional capacity; reduction in hospitalization for cardiovascular causes, stroke death, or overall mortality; or a composite of some of these parameters.

Atrial Fibrillation↗
PubMed2004

Ventricular high-rate episodes in pacemaker diagnostics identify a high-risk subgroup of patients with tachy-brady syndrome.

OBJECTIVES: The purpose of this study was to evaluate the frequency and clinical significance of ventricular high-rate (VHR) episodes (ventricular rate >162 bpm) in patients with symptomatic bradycardia and paroxysmal atrial fibrillation (AF). BACKGROUND: Newer pacemakers have enhanced diagnostic features that permit detection and storage of detailed information about the frequency, duration, and time of onset of multiple episodes of AF, atrial tachycardia (AT), and ventricular tachycardia (VT). However, the prevalence and prognostic value of AF associated with rapid ventricular rates in the pacemaker population are unknown. METHODS: We prospectively followed 125 patients who received a Medtronic AT 500/501 pacemaker for symptomatic bradycardia and paroxysmal AF. RESULTS: AF recurred in 112 patients (90%) during 22 +/- 8 months of follow-up. A total of 1,324 VHR episodes occurred in 38 patients (30%). Episodes with available electrograms (n = 560) were reviewed and classified as AF (n = 279; 50%), AT (n = 266; 47%) or VT (n = 15; 3%). AF burden was higher in patients with VHR episodes (median 1.9 vs 0.2 hours/day; P < .001). After controlling for AT/AF burden and heart disease, VHR episodes were a significant independent predictor of hospitalization for cardiovascular symptoms (odds ratio 2.92, 95% confidence interval 1.33-6.38; P = .007). Heart rate control improved over time in the cohort, and the frequency of VHR episodes decreased during follow-up (P < .001). CONCLUSIONS: VHR episodes documented in the pacemaker diagnostics identify a high-risk subgroup of patients with AF. Monitoring VHR episodes may be useful for identifying pacemaker patients with AF who require more vigilant monitoring, additional investigations, and/or additional interventions.

Aged↗