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Biomedical subjects

Denis Roy

Publications and source records attributed to Denis Roy.

At least 19 recordsLinked to original sources
PubMed2007

Resource-based adaptive divergence in the freshwater fish Telmatherina from Lake Matano, Indonesia.

Adaptive radiations are an important source of biodiversity, but resolving which ecological pressures seed these processes in natural systems remains difficult. Here the adaptive radiation among Telmatherina, a genus of freshwater fish endemic to an ancient lake in central Sulawesi, Indonesia, was examined to determine its causal root. We demonstrate that all Telmatherina in this lake can be categorized into three lineages each possessing specialized skull shapes and pharyngeal jaw bones allowing them to exploit different resources. These data demonstrate a natural example of how resource partitioning has likely initiated adaptive radiation in a resource limited environment.

Adaptation, Biological↗
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

Concordance between an electroanatomic mapping system and cardiac MRI in arrhythmogenic right ventricular cardiomyopathy.

A 29-year-old man presenting with syncopal ventricular tachycardia was diagnosed with arrhythmogenic right ventricular (RV) cardiomyopathy. Cardiac magnetic resonance imaging (MRI) revealed an unequivocal dyskinetic segment at the basal portion of the RV lateral free wall. Three-dimensional electroanatomic voltage mapping using the EnSite NavX system recorded a low voltage area corresponding to the diseased portion of the right ventricle identified by MRI. This report describes concordance between cardiac MRI and this novel mapping system in arrhythmogenic RV cardiomyopathy.

Adult↗
PubMed2006

Arrhythmias in adult congenital heart disease.

Recent advances in pediatric cardiology and cardiac surgery have allowed a rapidly expanding population of patients with congenital heart disease to thrive well into their adult years. Often after prolonged uneventful clinical courses as children and adolescents, arrhythmias may surface later in life. These arrhythmias are a major source of morbidity. In addition, sudden death is the leading cause of mortality in adult patients with congenital heart disease. This review highlights the various types of brady- and tachyarrhythmias encountered in the more common forms of adult congenital heart disease and explores prognostic implications and therapeutic options.

Adult↗
PubMed2005

Challenges in the addition of probiotic cultures to foods.

Probiotic cultures are increasingly being added to foods in order to develop products with health-promoting properties. Although the literature is abundant on the beneficial effects of bifidobacteria and Lactobacillus acidophilus on health, little information is available on the challenges industry faces in adding these probiotic cultures to food products. The aim of this article is to examine seven issues that should be addressed when developing functional foods: 1) type or form of probiotic that should be used; 2) addition level required to have a beneficial effect; 3) toxicity; 4) effect of the processing steps on viability; 5) determination, in the product, of the cell populations added; 6) stability during storage; 7) changes in sensory properties of the foods.

Bacterial Physiological Phenomena↗
PubMed2005

Anodal right ventricular capture during left ventricular stimulation in CRT-implantable cardioverter defibrillators.

BACKGROUND: Cardiac resynchronization therapy (CRT) has been shown to improve symptoms of patients with moderate to severe heart failure. Optimal CRT involves biventricular or left ventricular (LV) stimulation alone, atrio-ventricular (AV) delay optimization, and possibly interventricular timing adjustment. Recently, anodal capture of the right ventricle (RV) has been described for patients with CRT-pacemakers. It is unknown whether the same phenomenon exists in CRT systems associated with defibrillators (CRT-ICD). The RV leads used in these systems are different from pacemaker leads: they have a larger diameter and shocking coils, which may affect the occurrence of anodal capture. METHODS: We looked for anodal RV capture during LV stimulation in 11 consecutive patients who received a CRT-ICD system with RV leads with a true bipolar design. Fifteen patients who had RV leads with an integrated design were used as controls. Anodal RV and LV thresholds were determined at pulse width (pw) durations of 0.2, 0.5, and 1.0 ms. RESULTS: RV anodal capture during LV pacing was found in 11/11 patients at some output with true bipolar RV leads versus 0/15 patients with RV leads with an integrated bipolar design. Anodal RV capture threshold was more affected by changes in pw duration than LV capture threshold. In CRT-ICD systems, RV leads with a true bipolar design with the proximal ring also used as the anode for LV pacing are associated with a high incidence of anodal RV capture during LV pacing. This may affect the clinical response to alternative resynchronization methods using single LV stimulation or interventricular delay programming.

Adult↗
PubMed2005

The doubly phosphorylated form of HPr, HPr(Ser~P)(His-P), is abundant in exponentially growing cells of Streptococcus thermophilus and phosphorylates the lactose transporter LacS as efficiently as HPr(His~P).

In Streptococcus thermophilus, lactose is taken up by LacS, a transporter that comprises a membrane translocator domain and a hydrophilic regulatory domain homologous to the IIA proteins and protein domains of the phosphoenolpyruvate:sugar phosphotransferase system (PTS). The IIA domain of LacS (IIALacS) possesses a histidine residue that can be phosphorylated by HPr(His~P), a protein component of the PTS. However, determination of the cellular levels of the different forms of HPr, namely, HPr, HPr(His~P), HPr(Ser-P), and HPr(Ser-P)(His~P), in exponentially lactose-growing cells revealed that the doubly phosphorylated form of HPr represented 75% and 25% of the total HPr in S. thermophilus ATCC 19258 and S. thermophilus SMQ-301, respectively. Experiments conducted with [32P]PEP and purified recombinant S. thermophilus ATCC 19258 proteins (EI, HPr, and IIALacS) showed that IIALacS was reversibly phosphorylated by HPr(Ser-P)(His~P) at a rate similar to that measured with HPr(His~P). Sequence analysis of the IIALacS protein domains from several S. thermophilus strains indicated that they can be divided into two groups on the basis of their amino acid sequences. The amino acid sequence of IIALacS from group I, to which strain 19258 belongs, differed from that of group II at 11 to 12 positions. To ascertain whether IIALacS from group II could also be phosphorylated by HPr(His~P) and HPr(Ser-P)(His~P), in vitro phosphorylation experiments were conducted with purified proteins from Streptococcus salivarius ATCC 25975, which possesses a IIALacS very similar to group II S. thermophilus IIALacS. The results indicated that S. salivarius IIALacS was phosphorylated by HPr(Ser-P)(His~P) at a higher rate than that observed with HPr(His~P). Our results suggest that the reversible phosphorylation of IIALacS in S. thermophilus is accomplished by HPr(Ser-P)(His~P) as well as by HPr(His~P).

Amino Acid Sequence↗
PubMed2005

Sudden death and hypertrophic cardiomyopathy: a review.

Hypertrophic cardiomyopathy is a genetic disease that affects the cardiac sarcomere, resulting in myocardial hypertrophy and disarray. Affected patients have a predisposition for malignant ventricular tachyarrhythmias and, consequently, sudden cardiac death. With the availability of therapeutic measures that prevent sudden death, the identification of high-risk patients is now of greater importance. Clinical risk factors for sudden death (ie, age, syncope, family history of sudden cardiac death, cardiac arrest survivor, nonsustained ventricular tachycardia and abnormal blood pressure response to exercise) have been identified. The clinical electrophysiological study is of limited use for stratifying these patients. More recently, increased attention has been given to the degree of echocardiographically documented left ventricular hypertrophy and prognostically significant genetic mutations. Once a high-risk patient is identified, prophylactic treatment is warranted. For this purpose, amiodarone has been supplanted by the implantable cardioverter-defibrillator. Implantable cardioverter-defibrillator treatment appears to reduce the risk of sudden cardiac death in both primary and secondary prevention settings. Thus, tools are now available to identify and treat high-risk patients with hypertrophic cardiomyopathy.

Amiodarone↗
PubMed2005

Atrial fibrillation: basic and clinical research at the Montreal Heart Institute.

The present article reviews pertinent contributions from the Montreal Heart Institute, Montreal, Quebec, to the understanding of the mechanisms and treatment of atrial fibrillation. The article discusses the usefulness of anticoagulant therapy, antiarrhythmic drug therapy for sinus rhythm maintenance, the electrophysiological basis of atrial fibrillation and the investigation of new energy sources for catheter ablation. Future directions at the Montreal Heart Institute are also briefly addressed.

Academies and Institutes↗
PubMed2005

Drug therapy for termination of atrial fibrillation and maintenance of sinus rhythm.

Antiarrhythmic drug therapy to maintain sinus rhythm has not been demonstrated in randomized clinical trials to improve prognosis or prevent thromboembolic complications in patients with atrial fibrillation (AF). Therefore, drug therapy to restore and maintain sinus rhythm should be limited to those patients who have a greater symptomatic burden of AF. Patients with AF may be completely unaware of their arrhythmia or may present with palpitations, poor exercise tolerance or symptoms of congestive heart failure. In general, younger patients with paroxysmal arrhythmia and patients with decreased left ventricular compliance tend to be more symptomatic. The present article outlines the mechanisms of action of antiarrhythmic drugs in AF. Drugs that are recommended and frequently used to convert AF and maintain sinus rhythm are reviewed, and the toxicity of antiarrhythmic drug toxicity is discussed.

Anti-Arrhythmia Agents↗
PubMed2004

A randomized, controlled trial of RSD1235, a novel anti-arrhythmic agent, in the treatment of recent onset atrial fibrillation.

OBJECTIVES: The purpose of this study was to determine the efficacy and safety of intravenous RSD1235 in terminating recent onset atrial fibrillation (AF). BACKGROUND: Anti-arrhythmic drugs currently available to terminate AF have limited efficacy and safety. RSD1235 is a novel atrial selective anti-arrhythmic drug. METHODS: This was a phase II, multi-centered, randomized, double-blinded, step-dose, placebo-controlled, parallel group study. Fifty-six patients from 15 U.S. and Canadian sites with AF of 3 to 72 h duration were randomized to one of two RSD1235 dose groups or to placebo. The two RSD1235 groups were RSD-1 (0.5 mg/kg followed by 1 mg/kg) or RSD-2 (2 mg/kg followed by 3 mg/kg), by intravenous infusion over 10 min; a second dose was given only if AF was present. The primary end point was termination of AF during infusion or within 30-min after the last infusion. Secondary end points included the number of patients in sinus rhythm at 0.5, 1, and 24 h post-last infusion and time to conversion to sinus rhythm. RESULTS: The RSD-2 dose showed significant differences over placebo in: 1) termination of AF (61% vs. 5%, p < 0.0005); 2) patients in sinus rhythm at 30 min (56% vs. 5%, p < 0.001); 3) sinus rhythm at 1 h (53% vs. 5%, p = 0.0014); and 4) median time to conversion to SR (14 vs. 162 min, p = 0.016). There were no serious adverse events related to RSD1235. CONCLUSIONS: RSD1235, a new atrial-selective anti-arrhythmic agent, appears to be efficacious and safe for converting recent onset AF to sinus rhythm.

Adult↗
PubMed2004

Prognostic significance of newly acquired bundle branch block after aortic valve replacement.

There is controversy concerning the prognostic significance of conduction delays that occur after aortic valve replacement (AVR). We retrospectively reviewed 389 consecutive patients who underwent AVR at our institution between April 1995 and March 1997. Adverse events were defined as the occurrence of complete atrioventricular block, syncope, or sudden cardiac death. Among 262 patients included in our database, 31 (11.8%) had a preoperative bundle branch block (BBB) and 41 (15.6%) developed new BBB postoperatively. At a mean follow-up of 54 months, the event rate was 1.6% (3 of 190) in patients with no BBB versus 17% (7 of 41, p = 0.0004) in patients who developed new BBB after surgery. There were 4 events (4 of 15 = 26.6%, p = 0.0006) in patients who developed new left BBB and 3 (3 of 26, 11.5%, p = 0.02) in those who developed new right BBB after AVR. There was also an increased adverse event rate in patients who had preoperative BBB (3 of 31, 9.7%, p = 0.037). By multivariate analysis, a new and persistent BBB acquired after surgery was the only independent predictor of adverse events during follow-up (odds ratio 8.85, p = 0.0004). The highest event rate was seen in patients who developed new left BBB and left axis deviation after surgery. Most events occurred during the first year of follow-up. A new and persistent BBB acquired after AVR is associated with an increased adverse event rate. This finding suggests that early prophylactic pacemaker implantation should be considered in these patients.

Aged↗
PubMed2004

Beta-radiation for the creation of linear lesions in the canine atrium.

BACKGROUND: Creating linear lesions is important for the treatment of arrhythmias such as atrial flutter and fibrillation. Making these lesions with standard radiofrequency catheters can be difficult and may result in charring and thrombosis. The purpose of this study was to evaluate beta-radiation as a novel energy source for creating linear myocardial lesions. METHODS AND RESULTS: Eight dogs with intact conduction across the cavotricuspid isthmus were studied. The isthmus was irradiated (25 to 50 Gy) with strontium/yttrium-90 delivered via a deflectable 7F catheter (Novoste Corporation). There were no immediate effects, but bidirectional conduction block developed during follow-up studies in 7 of 8 dogs. The dog without conduction block received 25 Gy. After the animals were euthanized, histology revealed transmural, linear areas of fibrosis without any thrombus. CONCLUSIONS: Beta-radiation can safely and effectively create linear lesions that are contiguous and nonthrombogenic. This energy source may become an interesting adjunct to radiofrequency for the treatment of atrial flutter and fibrillation.

Animals↗
PubMed2004

Comparison of fructose-1,6-bisphosphatase gene (fbp) sequences for the identification of Lactobacillus rhamnosus.

Comparative analysis of fructose-1,6-bisphosphatase gene (fbp) sequences was evaluated for the differentiation of reference and clinical strains of Lactobacillus rhamnosus. The sequences of 1,971 nucleotides of the fbp gene were determined on both DNA strands for 21 L. rhamnosus strains, representing reference, probiotic, and clinical strains. No PCR amplification of the fbp gene was observed for other species of the Lactobacillus casei complex (L. casei and L. zeae) or strains of Lactobacillus acidophilus, Streptococcus thermophilus, and Escherichia coli. Phylogenetic analysis of the fbp putative amino acid sequences of L. rhamnosus strains by the neighbor-joining method showed clear distinct positions of this species. The phylogenetic tree, derived from fbp nucleotide sequences, showed four clear divisions between strains of L. rhamnosus. From a taxonomic point of view, our results confirm for the first time that fbp gene sequences have high discriminating power for strains of L. rhamnosus that are difficult to differentiate.

Amino Acid Sequence↗
PubMed2004

Thromboembolic events occur despite sinus rhythm maintenance in patients treated for atrial fibrillation: The Canadian Trial of Atrial Fibrillation experience.

BACKGROUND: Anticoagulation reduces the risk of stroke in patients with atrial fibrillation. It is not clear whether patients who revert and are maintained in sinus rhythm should continue to receive warfarin. The recommendation is to anticoagulate these patients for a minimum of four weeks after cardioversion. Whether warfarin should be maintained for a longer period of time is unknown. METHODS AND RESULTS: To address this question, data from the Canadian Trial of Atrial Fibrillation were reviewed. Among the 403 patients, 81.9% had at least one risk factor for stroke, of whom only 60% were on warfarin. Nine thromboembolic events occurred in nine patients (2.2%): all had at least one risk factor for stroke. Six events occurred in patients who were either not anticoagulated (n=4) or for whom the international normalization ratio was subtherapeutic (n=2). Eight of the nine patients were in sinus rhythm at the last follow-up visit before and at the time of evaluation of the thromboembolic event. CONCLUSIONS: Anticoagulants are underused in atrial fibrillation patients at risk of stroke. Thromboembolic events are most often associated with suboptimal levels of anticoagulation and they occur despite the appearance of sinus rhythm maintenance.

Aged↗
PubMed2003

The medical office of the 21st century (MOXXI): effectiveness of computerized decision-making support in reducing inappropriate prescribing in primary care.

BACKGROUND: Adverse drug-related events are common in the elderly, and inappropriate prescribing is a preventable risk factor. Our objective was to determine whether inappropriate prescribing could be reduced when primary care physicians had computer-based access to information on all prescriptions dispensed and automated alerts for potential prescribing problems. METHODS: We randomly assigned 107 primary care physicians with at least 100 patients aged 66 years and older (total 12 560) to a group receiving computerized decision-making support (CDS) or a control group. Physicians in the CDS group had access to information on current and past prescriptions through a dedicated computer link to the provincial seniors' drug-insurance program. When any of 159 clinically relevant prescribing problems were identified by the CDS software, the physician received an alert that identified the nature of the problem, possible consequences and alternative therapy. The rate of initiation and discontinuation of potentially inappropriate prescriptions was assessed over a 13-month period. RESULTS: In the 2 months before the study, 31.8% of the patients in the CDS group and 33.3% of those in the control group had at least 1 potentially inappropriate prescription. During the study the number of new potentially inappropriate prescriptions per 1000 visits was significantly lower (18%) in the CDS group than in the control group (relative rate [RR] 0.82, 95% confidence interval [CI] 0.69-0.98), but differences between the groups in the rate of discontinuation of potentially inappropriate prescriptions were significant only for therapeutic duplication by the study physician and another physician (RR 1.66, 95% CI 0.99-2.79) and drug interactions caused by prescriptions written by the study physician (RR 2.15, 95% CI 0.98-4.70). INTERPRETATION: Computer-based access to complete drug profiles and alerts about potential prescribing problems reduces the rate of initiation of potentially inappropriate prescriptions but has a more selective effect on the discontinuation of such prescriptions.

Adult↗
PubMed2003

Identification of atrial tissue in pulmonary veins using intravascular ultrasound.

BACKGROUND: Atrial fibrillation (AF) is initiated by ectopic beats originating in the sleeve of atrial tissue in pulmonary veins (PVs). Circumferential ablation of PVs can, thus, result in a cure of AF. Identification of this PV arrhythmogenic tissue has been exclusively on the basis of electrophysiologic recordings. The purpose of this study was to visualize this tissue using intravascular ultrasound (IVUS). Methods and results In all, 15 patients undergoing AF ablation had IVUS studies of their PVs. A total of 21 veins had a wall thickness less than 0.1 mm, whereas 31 veins had well-demarcated areas of thickening measuring 0.81 +/- 0.32 mm. Electrophysiologic recordings from these thickened areas showed typical high-frequency potentials associated with arrhythmogenic atrial tissue in the PVs. Ectopic beats initiating AF always originated from these areas. PVs without thickening on IVUS did not have these potentials. CONCLUSIONS: IVUS permits visualization of atrial tissue in the PVs, and arrhythmogenic PVs are qualitatively and quantitatively different from nonarrhythmogenic PVs.

Action Potentials↗