Pacemaker troubleshooting: when MVP is not the most valuable parameter.
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Aged↗
Biomedical subjects
Bernard Thibault
Publications and source records attributed to Bernard Thibault.
Demographics, treatment and outcome of acute coronary syndromes: 17 years of experience in a specialized cardiac centre.
BACKGROUND: Epidemiological information on patients with acute coronary syndromes managed in specialized cardiac centres is limited. OBJECTIVE: To report the evolution of demographics, treatment and outcome of patients admitted to a tertiary coronary care unit (CCU) over a 17-year period. METHODS: A prospective database of 18,719 patients admitted from April 1986 to March 2003 in a 21-bed CCU was analyzed. RESULTS: From 1986 to 2003, the number of admissions increased from 937 to 1577 per year, while the length of stay declined from 7.5 to 3.5 days. The mean age increased from 58.4 to 63.4 years, and the proportion of men remained stable at approximately 70%. The use of coronary angiograms increased from 49.8% to 81.1% in all patients, while fibrinolysis dropped to 0.4%. In-hospital mortality decreased from 9% to 1.5%. The percentage of overall instrumentation (arterial line, central venous catheter, temporary pacemaker, Swan-Ganz catheter and intra-aortic balloon pump) decreased from 38% to 8.1%. From 1995 to 2003, the proportion of stenting during percutaneous transluminal coronary angioplasty increased dramatically from 0% to 86%. In the past five years, surgical revascularization has remained stable at approximately 20% of all admissions. The proportion of patients discharged with a noncoronary chest pain diagnosis has remained constant at approximately 4%. INTERPRETATION: There has been a tremendous increase in efficiency, with an approximate doubling of the admissions turnover rate in a tertiary CCU. Patients with acute coronary syndromes are stratified faster and treated more invasively. Therapeutic advances are reflected by an almost linear 0.5% per year decrease in in-hospital mortality.
Age Distribution↗
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↗
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↗
Right atrial tachycardia in a patient with severe atrial conduction disturbances and an anatomically normal heart.
We describe a case of abnormal right atrial (RA) conduction in a patient with atrial tachycardia (AT) but no history of structural heart disease or cardiac surgery. Following ablation of AT, the patient experienced typical atrial flutter (AFL) and a postcardioversion ECG suggestive of low atrial rhythm. Repeat EPS and three-dimensional electroanatomic activation mapping showed unusual RA activation during SR. This case illustrates the possibility that abnormal intraatrial conduction may lead to unusual patterns of activation in the RA which can serve as a necessary substrate for the initiation and maintenance of macro-reentry circuits.
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↗
Enhanced left atrial mapping using digitally synchronized NavX three-dimensional nonfluoroscopic mapping and high-resolution computed tomographic imaging for catheter ablation of atrial fibrillation.
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Atrial Fibrillation↗
Randomized controlled study of detection enhancements versus rate-only detection to prevent inappropriate therapy in a dual-chamber implantable cardioverter-defibrillator.
OBJECTIVES: The purpose of this study was to compare rate-only detection to enhanced detection in a dual-chamber implantable cardioverter-defibrillator (ICD), to discriminate ventricular tachycardia from supraventricular tachycardia. BACKGROUND: ICDs are highly effective in treating ventricular tachycardia (VT) or ventricular fibrillation (VF). However, they frequently deliver inappropriate therapy during supraventricular tachycardia (SVT). METHODS: We conducted a randomized clinical trial of detection enhancements in a dual-chamber ICD compared to control (rate-only) detection to discriminate VT from SVT. Detection enhancements included a specific standardized protocol identical for all patients for programming rate stability, sudden onset, atrial-to-ventricular relationship (sudden onset = 9% and rate stability = 10 ms; V > A "on"), and "sustained rate duration" (3 minutes). The primary endpoint was the time to first inappropriate therapy classified by a blinded events committee. RESULTS: One hundred forty-nine patients had a history of sustained VT or VF. Mean age (+/- SD) was 60 +/- 13 years; 83% were male, and mean ejection fraction was 35 +/- 15%. Control (n = 70) and "enhanced" (n = 79) groups did not differ with regard to age, sex, ejection fraction, or primary arrhythmia. The proportion of patients free of inappropriate therapy over time was significantly higher in the enhanced versus the control group (hazard ratio = 0.47, P = .011). High-energy shocks were reduced from 0.58 +/- 4.23 shocks/patient/month in the control group to 0.04 +/- 0.15 shocks/patient/month in the enhanced group (P = .0425). No patient programmed per protocol failed to receive therapy for VT detected by the ICD (422 VT episodes). CONCLUSIONS: Standardized programming in a dual-chamber ICD leads to a significant and clinically important reduction in inappropriate therapies compared to rate-only detection and does not compromise safety with respect to appropriate treatment of VT.
Age Factors↗
Utility of a nonfluoroscopic navigation system for pulmonary vein isolation.
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Body Surface Potential Mapping↗
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↗
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↗
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↗
Alternating narrow and wide complex tachycardia.
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Adult↗
New approaches to atrial fibrillation management: a critical review of a rapidly evolving field.
Atrial fibrillation (AF) is the most common cardiac arrhythmia, the prevalence of which is increasing with the aging of the population. Because of its clinical importance and the lack of highly satisfactory management approaches, AF is the subject of active clinical and research efforts. This paper reviews recent and on-going developments in pharmacological and non-drug management of AF. The ideal therapeutic goal for AF is the production and maintenance of sinus rhythm. Comparative studies suggest that available class I and III drugs have comparable and modest efficacy for sinus rhythm maintenance. Amiodarone, with actions of all antiarrhythmic classes, has recently been shown to have clearly superior efficacy compared with other available drugs. Newer agents are in development, but their advantages are as yet unclear and appear limited. A potentially interesting approach is the prescription of drugs upon the occurrence of an attack, rather than on a continuous basis. Recent insights into AF mechanisms may permit therapy to prevent development of the AF substrate. An alternative to sinus rhythm maintenance is a rate control approach, with no attempt to prevent AF. Drugs to effect rate control include digitalis, beta-blockers and calcium channel antagonists. Digitalis has limited value for control of exercise heart rate and for paroxysmal AF, but is particularly well suited for patients with concomitant AF and congestive heart failure. AV-nodal ablation and pacing is an effective alternative for rate control but leaves the patient pacemaker dependent. The relative merits of rate versus rhythm control are being evaluated in ongoing trials, preliminary results of which indicate no statistically significant differences in primary endpoints but highlight the risks of rhythm control therapy. In patients requiring pacemakers, physiological pacing (dual chamber devices or atrial pacing) has an advantage over purely ventricular pacemakers in AF prevention. Newer pacing modalities that produce more synchronised atrial activation, as well as pacemakers that prevent excessive atrial rate swings, show promise in AF prevention and may soon see wider use. The usefulness of automatic atrial defibrillators is presently limited by discomfort during shocks. Targeted destruction of pulmonary vein foci by radiofrequency catheter ablation suppresses paroxysmal AF. Efficacy in persistent AF is lower and still under study. Problems include potential recurrence in other veins and a small but nontrivial risk of pulmonary vein stenosis. Surgical division of the atria into zones with limited electrical connection, the MAZE procedure, is highly effective in AF prevention but is a major intervention that is not applicable to most patients. In conclusion, significant advances are being made in the management of patients with AF but much more work remains to be done.
Anti-Arrhythmia Agents↗