Wolff-Parkinson-white syndrome in d-transposition of the great arteries and mustard baffle.
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Adult↗
Biomedical subjects
Marc Dubuc
Publications and source records attributed to Marc Dubuc.
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↗
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↗
Transcatheter mapping and ablation of arrhythmias in the coronary sinus.
The coronary sinus (CS) is a complex structure of particular interest to cardiac electrophysiologists. It is exploited as an anatomical reference, a site to record left-sided atrial and ventricular signals and for cardiac resynchronization therapy. Perhaps less appreciated, it may itself serve as a substrate for arrhythmias. It is now increasingly recognized that arrhythmias may be targeted by transcatheter ablation within the CS. This review summarizes pertinent anatomic considerations, explores the relationship between the CS and various arrhythmia substrates, elaborates on current indications for intra CS ablation and addresses efficacy and safety concerns associated with transcatheter ablation.
Arrhythmias, Cardiac↗
Cardiac resynchronization therapy in congenital heart disease.
While cardiac resynchronization therapy (CRT) is of proven benefit in selected patients with severe ischemic or dilated cardiomyopathy, refractory symptoms, and conduction delay, extrapolation to congenital heart disease is not straightforward. This rapidly expanding patient population commonly suffers from heart failure, particularly in the presence of a single or systemic right ventricle. Surgical repair may also contribute to ventricular asynchrony. In this systematic review, the current state of knowledge regarding CRT in congenital heart disease is presented. Issues specific to congenital heart disease including right bundle branch block, right (pulmonary) ventricular dysfunction, systemic right ventricular dysfunction, and single ventricle dysfunction are explored. Evidence-based CRT applications for each of these particular conditions are reviewed. Initial experience with CRT in the acute postoperative setting and longer-term, including our own, is elaborated. Unlike standard indications based on multiple randomized clinical trials, supporting evidence for CRT in congenital heart disease is limited to case reports, case series, and small experimental crossover studies in the acute postoperative setting. The heterogeneous patient population, technical limitations from patient size, vascular access issues, and unique forms of ventricular asynchrony further obscure the selection of potential beneficiaries. Despite these limitations, experience thus far has been favorable. Quality of current data precludes definitive evidence-based recommendations, but optimistic initial results suggest that research endeavors in this field should be pursued. Multicenter prospective collaborative efforts are to be encouraged.
Cardiac Pacing, Artificial↗
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↗
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↗
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↗
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↗
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↗
Catheter cryoablation of supraventricular tachycardia: results of the multicenter prospective "frosty" trial.
OBJECTIVE: To study the safety, efficacy, and mapping utility of a new cryoablation catheter. BACKGROUND: The CryoCath Technologies Freezor catheter has been used successfully for cryoablation of supraventricular tachycardia (SVT), but has not been evaluated in a large clinical trial. METHODS: A multicenter clinical trial to evaluate the safety, efficacy, and cryomapping utility of this cryoablation catheter was conducted in 166 subjects. The target of ablation was the slow pathway in patients with SVT due to AV nodal reentry (AVNRT, n = 103), an accessory pathway in patients with AV reentrant SVT (AVRT, n = 51) and the AV junction in patients with atrial fibrillation (AF, n = 12). RESULTS: Acute procedural success (APS) was achieved in 83% of the overall group (95% CI, 76% to 88%). APS in the AVNRT group was 91% (98.3% CI, 82% to 97%), compared to 69% for AVRT (98.3% CI, 51% to 84%) and 67% for AF (98.3% CI, 29% to 93%), a highly significant difference (P < .001 by stepwise logistic regression). In patients with APS, long-term success after 6 months was 91% overall (95% CI, 86% to 96%) and 94% for AVNRT subjects (98.3% CI, 87% to 100%). None of the AVNRT or AVRT subjects required a permanent pacemaker. Cryomapping successfully identified ablation targets in 64% of patients in whom it was attempted. The electrophysiologic effects of cryomapping were completely reversible within minutes in 94% of such attempts. CONCLUSIONS: Catheter cryoablation of SVT is a safe alternative to RF ablation and is clinically effective in patients with AVNRT. Cryomapping can reversibly identify targets for ablation and can help minimize the risk of inadvertent AV block during ablation.
Adult↗
Implantable cardioverter defibrillators in adults with congenital heart disease: a single center experience.
Sudden death is the most frequent cause of late mortality in adults with congenital heart disease. This study reviews the experience of an Adult Congenital Heart Center with the use of implantable cardioverter defibrillators (ICDs). The charts of adults with congenital heart disease who had an ICD implantation were reviewed for diagnosis, residual lesions, reoperations, reason for implantation, complications, and recurrence of arrhythmias. Since 1995, 13 patients (mean age 43 years) had an ICD implantation for aborted sudden death (4), and spontaneous (6), or induced (3) ventricular tachycardia. Diagnosis were repaired (6) or palliated (1) tetralogy of Fallot, operated pulmonary stenosis (2), palliated complex pulmonary atresia (1), congenitally corrected transposition (1), operated ventricular (1), and atrial (1) septal defects. Significant residual lesions included severe pulmonary regurgitation (2), systemic ventricular dysfunction (2), and severe pulmonary hypertension (1). Five patients had a QRS > 180 ms, four had a QRS < 180 ms, four had a paced rhythm. Overall, four (31%) patients had no ventricular dysfunction, no residual lesion, and QRS < 180 ms. During a mean follow-up of 29 months, seven patients had recurrent ventricular tachycardia, three with normal ventricular function, no residual lesion, and QRS < 180 ms. ICD implantation is an important adjunct in the management of adults with congenital heart disease. As malignant arrhythmias occur even in patients with no residual lesion, no QRS prolongation and no ventricular dysfunction, the recognition of those who would benefit from an ICD remains a clinical challenge.
Adolescent↗
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↗
Lower incidence of thrombus formation with cryoenergy versus radiofrequency catheter ablation.
BACKGROUND: Radiofrequency (RF) catheter ablation is limited by thromboembolic complications. The objective of this study was to compare the incidence and characteristics of thrombi complicating RF and cryoenergy ablation, a novel technology for the catheter-based treatment of arrhythmias. METHODS AND RESULTS: Ablation lesions (n=197) were performed in 22 mongrel dogs at right atrial, right ventricular, and left ventricular sites preselected by a randomized factorial design devised to compare RF ablation with cryocatheter configurations of varying sizes (7F and 9F), cooling rates (-1 degrees C/s, -5 degrees C/s, and -20 degrees C/s) and target temperatures (-55 degrees C and -75 degrees C). Animals were pretreated with acetylsalicylic acid and received intraprocedural intravenous unfractionated heparin. Seven days after ablation, the incidence of thrombus formation was significantly higher with RF than with cryoablation (75.8% versus 30.1%, P=0.0005). In a multiple regression model, RF energy remained an independent predictor of thrombus formation compared with cryoenergy (OR, 5.6; 95% CI, 1.7, 18.1; P=0.0042). Thrombus volume was also significantly greater with RF than with cryoablation (median, 2.8 versus 0.0 mm3; P<0.0001). More voluminous thrombi were associated with larger RF lesions, but cryolesion dimensions were not predictive of thrombus size. CONCLUSIONS: RF energy is significantly more thrombogenic than cryoenergy, with a higher incidence of thrombus formation and larger thrombus volumes. The extent of hyperthermic tissue injury is positively correlated with thrombus bulk, whereas cryoenergy lesion size does not predict thrombus volume, most likely reflecting intact tissue ultrastructure with endothelial cell preservation.
Animals↗
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↗
Surgical radiofrequency ablation induces coronary endothelial dysfunction in porcine coronary arteries.
OBJECTIVES: Surgical radiofrequency ablation is increasingly used during open heart surgery for the treatment of chronic atrial fibrillation. The purpose of this study was to determine the effects of application of radiofrequency on coronary endothelial function and structure and establish the relationship between coronary lesions and distance of radiofrequency application. METHODS: Six Landrace swine (25.9+/-2.0 kg) were included in the study. With the heart kept beating, three epicardial radiofrequency lesions (20 W, 20 s duration, 60 degrees C) 2 cm in length each, were created 1, 5 and 10 mm away from the left anterior descending and the right coronary arteries. The circumflex artery served as control. Coronary rings were placed in organ chambers. After contraction to KCl and prostaglandin F2alpha, endothelium-dependent relaxations to bradykinin were studied. Gomori trichrome and hematoxylin-eosin safran staining were used for histological evaluation. RESULTS: Exposure to radiofrequency 1 mm from the coronary arteries caused a significant decrease in endothelium-independent contractions to KCl and endothelium-dependent relaxations to bradykinin compared to controls (P<0.05). No significant decrease of endothelium-dependent relaxations occurred for rings exposed to radiofrequency at a distance of 5 and 10 mm, compared to controls. Histological examination showed endothelial disruption and medial smooth muscle cells at different stages of necrosis up to 5 mm from the radiofrequency application site. CONCLUSIONS: Radiofrequency may induce coronary endothelial functional and morphological damages when applied less than 5 mm from the artery. Caution must be exerted during left atrial radiofrequency application due to the proximity of the circumflex artery.
Animals↗
Mönckeberg's sling.
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Atrioventricular Node↗
Prognostic significance of ventricular arrhythmias post-myocardial infarction.
Despite improvements in management strategies, ventricular arrhythmias remain important markers of electrical instability and contribute to the identification of patients at increased risk of sudden cardiac death post-myocardial infarction (MI). Over the past 20 years, understanding of pathophysiological mechanisms and implications of various types of ventricular arrhythmias has evolved remarkably. This systematic review details the prognostic significance of ventricular arrhythmias classified by type and time of onset post-MI. Subacute and late premature ventricular complexes are associated with increased mortality independent of left ventricular function. Although nonsustained ventricular tachycardia (VT) in the acute phase post-MI is of questionable significance, later onset heralds poorer prognosis. Sustained monomorphic VT in the acute post-MI phase is associated with infarct extension, heart failure and increased mortality. Extensive wall motion abnormalities, left ventricular dysfunction and aneurysm formation correlate with later postinfarct sustained VT. Inhospital mortality is higher when ventricular fibrillation presents in the acute phase but long term prognosis is not adversely affected.
Anti-Arrhythmia Agents↗