PubMed Health⌕ Search

Biomedical subjects

Charles R Kerr

Publications and source records attributed to Charles R Kerr.

17 recordsLinked to original sources
PubMed2006

Efficacy of azimilide for the maintenance of sinus rhythm in patients with paroxysmal atrial fibrillation in the presence and absence of structural heart disease.

Azimilide hydrochloride (azimilide), an investigational antiarrhythmic drug, has shown variable efficacy in preventing atrial fibrillation (AF). This study was designed to assess its efficacy in maintaining sinus rhythm in patients with paroxysmal AF and heart disease. Patients with symptomatic paroxysmal AF were screened for 1 month by transtelephonic monitoring. After recording 1 episode of AF in the screening period, they were randomized to receive azimilide 125 mg or placebo once daily. Patients were stratified by the presence or absence of congestive heart failure or coronary heart disease (CHF/CHD). A maximum of 220 patients without CHF/CHD were randomized, with the remainder having CHF/CHD. Patients with CHF/CHD were monitored for 3 days during loading. The primary efficacy analysis was the time to the first symptomatic recurrence of AF in the CHF/CHD group. Secondary analyses were the time to the first recurrence in the entire population and the time to the first recurrence in those with significant structural heart disease. The median time to recurrence of AF in the CHF/CHD group was 10 days in the 2 treatment arms. Nonsignificant trends were seen toward efficacy of azimilide in the CHF/CHD group (hazard ratio 1.28, 95% confidence interval 0.97 to 1.70, p=0.087), structural heart disease group (hazard ratio 1.22, 95% confidence interval 0.96 to 1.56, p=0.11), and overall group (hazard ratio 1.22, 95% confidence interval 1.00 to 1.49, p=0.053). No patient died. In conclusion, azimilide showed a nonsignificant trend toward efficacy in maintaining sinus rhythm in patients with AF.

Anti-Arrhythmia Agents↗
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↗
PubMed2005

Progression to chronic atrial fibrillation after the initial diagnosis of paroxysmal atrial fibrillation: results from the Canadian Registry of Atrial Fibrillation.

BACKGROUND: After its initial diagnosis, atrial fibrillation (AF) may progress from paroxysmal to chronic AF (CAF). The rate of progression and risk factors for progression are not clearly defined. METHODS: The Canadian Registry of Atrial Fibrillation (CARAF) enrolled patients from 6 Canadian cities at the time of their first electrocardiographic diagnosis of AF. Comprehensive clinical and echocardiographic data were collected and patients were followed annually, carefully documenting clinical outcomes, recurrence of paroxysmal AF, and progression to CAF. Baseline clinical, electrocardiographic, and echocardiographic variables were evaluated by univariate Cox proportionate hazards analysis. A stepwise approach was used to model the association between echocardiographic and clinical variables with progression to CAF. RESULTS: A total of 757 patients with a baseline diagnosis of paroxysmal AF were evaluated. Median follow-up was 8.0 years (range 2 days to 11.1 years). The probability of progression to CAF by 1 year was 8.6% and thereafter there was a slow but steady progression to 24.7% by 5 years. By 5 years, the probability of documented recurrence of any AF (chronic or paroxysmal) was 63.2%. Increasing age, significant aortic stenosis or mitral regurgitation, left atrial enlargement, and diagnosis of cardiomyopathy were independently associated with progression to CAF. A more rapid heart rate during AF was associated with decreased risk of progression. CONCLUSIONS: After the initial diagnosis of paroxysmal AF, there is a slow but steady progression to CAF. Baseline echocardiographic variables, age, cardiomyopathy, and heart rate were independently associated with progression to CAF.

Adolescent↗
PubMed2005

Cerebral oxygenation during defibrillator threshold testing of implantable cardioverter defibrillators.

BACKGROUND: The induction of ventricular fibrillation (VF) during defibrillator threshold testing of implantable cardioverter defibrillators (ICD) provokes global cerebral hypoperfusion and impaired oxygen delivery. Limited data are available on the neurophysiological effects of defibrillator threshold testing. Near infrared spectroscopy (NIRS) can noninvasively measure changes in specific chromophores, which reflect cerebral oxygenation at the intravascular and mitochondrial levels. We performed a prospective trial using NIRS to analyze cerebral cortical oxygenation during defibrillator threshold testing. METHODS: Eleven patients (men = 9; age = 64 +/- 11 years: LVEF = 44 +/- 11%) underwent subpectoral ICD implantation and defibrillator threshold testing under general anesthesia. A NIRO 300 spectrometer was used to measure the absolute changes in the concentrations of oxyhemoglobin, de-oxyhemoglobin, and cytochrome c oxidase copper moiety during each procedure. The mean arterial blood pressure was monitored simultaneously. RESULTS: The mean number of defibrillator threshold tests was two (range 2-6). Twenty-six episodes of VF (duration 13.1 +/- 9.7 seconds; cycle length 230.2 +/- 20.8 ms) and two episodes of VT (duration 15 +/- 2.8 seconds; cycle length 320 +/- 11.3 ms) were induced. Each episode of VF and VT resulted in a decrease in the mean arterial blood pressure to 23.9 +/- 7.5 mmHg (p < or = 0.05) and oxyhemoglobin (-4.2 +/- 1.7 micromol/L; p < or = 0.05) and an increase in de-oxyhemoglobin (2.7 +/- 1.4 micromol/L). There was no change in the cytochrome c oxidase copper moiety redox status (0.09 +/- 0. 30 micromol/L). CONCLUSION: Our results suggest that impaired oxygen delivery during induced VF and VT does not affect oxygen availability at the cellular intra-mitochondrial level.

Brain↗
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↗
PubMed2004

Limitations to antiarrhythmic drug use in patients with atrial fibrillation.

BACKGROUND: Of the antiarrhythmic agents currently marketed in Canada, 5 are commonly used to treat atrial fibrillation (AF). The impact of contraindications, warnings and precautions for the use of these drugs in patients with AF is not known. We evaluated the proportion of patients with AF for whom contraindications, warnings and/or precautions might limit the use of these commonly prescribed drugs and the proportion of patients actually receiving antiarrhythmic drugs despite the presence of contraindications and/or warnings. METHODS: A total of 723 patients with electrocardiographically confirmed, new-onset paroxysmal AF who were enrolled in the Canadian Registry of Atrial Fibrillation were used in this analysis. The 1996 Compendium of Pharmaceuticals and Specialties was used to obtain contraindications, warnings and precautions for use of 5 antiarrhythmic drugs: flecainide, quinidine, sotalol, amiodarone and propafenone. Proportions of patients with contraindications, warnings and/or precautions for use of any of these drugs owing to comorbid conditions or concomitant drug therapy were calculated, regardless of whether the drugs had been prescribed. We then calculated the proportion of patients taking each antiarrhythmic drug at 3 months despite contraindications and/or warnings. RESULTS: At baseline, when conditions for contraindications and warnings were combined, 414 (57%), 235 (33%), 327 (45%), 285 (39%) and 272 (38%) patients had restrictions for the use of flecainide, quinidine, sotalol, amiodarone and propafenone respectively. Among 465 patients actually taking these medications at 3-month follow-up, 33.3% (2/6), 83.3% (40/48), 36.4% (92/253), 64.1% (25/39) and 34.5% (41/119) respectively had contraindications and/or warnings against their use. The burden of comorbid disease among patients with AF was noteworthy: 404 (56%) had structural heart disease, which included 227 (31%) with ischemic heart disease, 158 (22%) with left ventricular systolic dysfunction and 106 (15%) with heart failure. INTERPRETATION: The high burden of comorbid disease and concomitant drug use in a large proportion of patients with AF limits the suitability of existing antiarrhythmic drugs. Over one-third of patients with new-onset AF received antiarrhythmic drugs despite the presence of contraindications or warnings. Although such restrictions may not preclude the use of these drugs, the results demonstrate the need for new antiarrhythmic drugs with fewer limitations.

Aged↗
PubMed2004

Prognostic differences between atrial fibrillation and atrial flutter.

This report presents the outcome of a cohort of 94 patients with atrial fibrillation from the Canadian Registry of Atrial Fibrillation, in which we paid particular attention to the probability of stroke and death. We also evaluated warfarin use over time and compared left atrial dimensions in patients with atrial flutter with those with atrial fibrillation.

Aged↗
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

The association of left atrial size and occurrence of atrial fibrillation: a prospective cohort study from the Canadian Registry of Atrial Fibrillation.

BACKGROUND: The effect of left atrial (LA) dimension on the recurrence of atrial fibrillation (AF) has been examined in small studies. We evaluated the effect of LA dimension on the occurrence of AF using 2- and 4-year echocardiographic data in a large cohort of patients with new onset AF. METHODS: The Canadian Registry of AF (CARAF) enrolled subjects with AF at the first electrocardiographically confirmed diagnosis. Patients were classified at 2 and 4 years as no recurrent AF (No RAF), paroxysmal AF (PAF), or chronic AF (CAF) based on clinical symptoms and electrocardiographic documentation. The association between baseline, 2-, and 4-year LA dimensions with occurrence of AF as determined by echocardiography was evaluated using a multivariate analysis. RESULTS: The No RAF group (n = 176) had a significantly smaller LA dimension (36.9 +/- 6.8 mm) at baseline compared to the CAF group (n = 227) (42.8 +/- 7.5 mm, P <.0001). The No RAF and PAF (n = 153) groups did not have a significant change in LA dimension at 2 or 4 years. Only those with CAF had a significant increase in LA dimension at 2 and 4 years, +1.39 mm (95% CI 0.01-2.8) and +3.48 mm (95% CI 1.8-5.2), respectively. CONCLUSIONS: A larger baseline LA dimension is associated with progression to CAF. Patients with no or paroxysmal recurrence had no change in LA dimension over a 4-year period. These findings have implications in tailoring modes of therapy in patients with AF.

Aged↗
PubMed2004

New-onset sustained ventricular tachycardia and fibrillation early after cardiac operations.

BACKGROUND: Malignant ventricular tachyarrhythmia early after cardiac surgery is an uncommon arrhythmic complication but has a negative impact on mortality. The purpose of this study was to evaluate the incidence of new-onset sustained postoperative ventricular tachycardia-ventricular fibrillation and to identify risk factors for the dysrhythmia. METHODS: Demographic, clinical, operative, and postoperative data, including a variable of postoperative ventricular tachycardia, were prospectively obtained from 4748 patients undergoing nonemergency coronary artery bypass graft and(or) valve replacement with no history of sustained ventricular tachycardia or sudden death. A detailed analysis was performed to define the risk factors for the ventricular tachycardia and the prognostic impact of the arrhythmia on 30-day mortality was evaluated. RESULTS: Forty-five patients (0.95%) had sustained ventricular tachycardia or ventricular fibrillation and the initial episode occurred 3.9 +/- 5.2 days (mean +/- standard deviation) after surgery. By multivariate analysis, female sex (odds ratio, 1.982), left ventricular ejection fraction (< 35%: > 50%, 4.771), the presence of pulmonary hypertension (3.066), the presence of systemic hypertension (2.391), and pump time (per 10 minutes, 1.085) were independently associated with the dysrhythmias. Early mortality of patients with the arrhythmia was 28.9%, strikingly higher than that of patients without ventricular tachycardia/ventricular fibrillation (1.9%). CONCLUSIONS: Left ventricular ejection fraction is the strongest risk factor for new-onset postoperative sustained ventricular tachycardia-ventricular fibrillation; female sex, pump time, pulmonary and systemic hypertension are independent predictors of the dysrhythmias; the arrhythmia is associated with increased 30-day mortality after cardiac surgery.

Aged↗
PubMed2003

Guidelines for implantable cardioverter defibrillator follow-up in Canada: a consensus statement of the Canadian Working Group on Cardiac Pacing.

A survey on the follow-up practices of patients with implantable cardioverter defibrillators (ICDs) in Canada was conducted by the Canadian Working Group on Cardiac Pacing in 1999. The survey identified the need for national guidelines. The present guidelines for ICD follow-up represent a consensus statement of the Canadian Working Group on Cardiac Pacing. They recommend that patients be assessed before hospital discharge, at two to 12 weeks following implantation, six months after implantation, and at a minimum of every six months thereafter. More frequent assessments may be required for some patients depending on associated cardiovascular problems and specific ICD devices. A typical follow-up visit should include a targeted cardiovascular assessment, interrogation of the ICD, review of telemetered data, assessment of the underlying rhythm, pacing and sensing thresholds, lead impedance and appropriate reprogramming of ICD parameters to optimize device function and longevity.

Cardiac Pacing, Artificial↗
PubMed2002

Long-term survival following radiofrequency catheter ablation of atrioventricular junction for atrial fibrillation: clinical and ablation determinants of mortality.

BACKGROUND: For patients with drug-refractory atrial fibrillation, radiofrequency catheter ablation of the atrioventricular junction and pacemaker implantation is a nonpharmacologic option routinely used nowadays. Few data are available on the long-term survival following the procedure or on evaluation of the risk factors for death in a large study cohort. METHODS: The patient population included 359 subjects undergoing atrioventricular junction ablation and pacemaker insertion. Fourteen clinical and 9 ablation variables were collected at baseline. During a mean following-up of 40.8 +/- 25.6 months, 46 patients died. Survival probability was estimated by the Kaplan-Meier methods. Multivariate Cox proportional hazards regression analysis was applied to define predictors of death. RESULTS: Mean age was 64.6 +/- 10.6 years with 203 male (57.7%). Actuarial survival probability for the total patients was 0.953 and 0.827 at 1 and 5 year. Four clinical variables, but no ablation variables, were found to be independent predictors of death: age > or =65 year (hazard ratio [HR], 1.92; 95% confidence interval [CI], 1.00-3.69), the presence of heart failure (HR, 3.83; 95% CI, 1.87-7.86), coexisting diabetes (HR, 2.91; 95% CI, 1.47-5.77), and the value of fractional shortening < or =20% (HR, 5.79, 95% CI, 3.00-11.18). There were 20 deaths in 28 patients with > or =3 risk factors and 4 deaths in 115 patients with no risk factor. CONCLUSION: The risk of death in patients undergoing ablation and pacing can be identified by readily available clinical variables. Patients with multiple risk factors are associated with an increasing mortality.

Adult↗