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Biomedical subjects

Laurent Macle

Publications and source records attributed to Laurent Macle.

At least 19 recordsLinked to original sources
PubMed2006

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↗
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↗
PubMed2005

Prevalence of pulmonary vein disconnection after anatomical ablation for atrial fibrillation: consequences of wide atrial encircling of the pulmonary veins.

AIMS: Anatomical and wide atrial encircling of the pulmonary veins (PVs) has been proposed as a cure of atrial fibrillation (AF). We evaluated the acute achievement of electrical PV isolation using this approach. In addition, the consequences of wide encircling of the PVs with isolation were assessed. METHODS AND RESULTS: Twenty patients with paroxysmal AF were studied. Anatomically guided ablation was performed utilizing the CARTO system to deliver coalescent lesions circumferentially around each PV to produce a voltage reduction to <0.1 mV, with the operator blinded to recordings of circumferential PV mapping. After achieving the anatomical endpoint, the incidence of residual conduction and the amplitude and conduction delay of residual PV potentials were determined. Electrical isolation of the PV was then performed and the residual far-field potentials evaluated. Individual PV ablation was performed in all PVs. Anatomically guided PV ablation was performed for 47.3+/-11 min, after which 44 (55%) PVs were electrically isolated. In the remaining 45%, despite abolition of the local potential at the ablation site, PV potentials [amplitude 0.2 mV (range 0.09-0.75) and delay of 50.3+/-12.6 ms] were identified by circumferential mapping. After electrical isolation (12.2+/-11.7 min ablation), 55 (69%) PVs demonstrated far-field potentials; with a greater incidence (P=0.015) and amplitude (P=0.021) on the left compared with the right PVs. At 13.2+/-8.3 months follow-up, 13 patients (65%) remained arrhythmia-free without anti-arrhythmics. In four patients (20%), spontaneous sustained left atrial macrore-entry required re-mapping and ablation. Macrore-entry was observed to utilize regions around or bordering the previous ablation as its substrate. CONCLUSION: Anatomically guided circumferential PV ablation results in apparently coalescent but electrically incomplete lesions with residual conduction in 45% of PVs. Wide encircling of the PVs was associated with left atrial macrore-entry in 20% of patients.

Atrial Fibrillation↗
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

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↗
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↗
PubMed2004

Technique and results of linear ablation at the mitral isthmus.

BACKGROUND: This prospective clinical study evaluates the feasibility and efficacy of combined linear mitral isthmus ablation and pulmonary vein (PV) isolation in patients with paroxysmal atrial fibrillation (AF). METHODS AND RESULTS: One hundred consecutive patients (13 women; age 55+/-10 years) with drug-refractory, symptomatic paroxysmal AF underwent PV isolation and linear ablation of the cavotricuspid isthmus and the mitral isthmus (lateral mitral annulus to the left inferior PV). They were compared with 100 consecutive patients (14 women; age, 52+/-10 years) undergoing PV isolation and cavotricuspid ablation without mitral isthmus ablation. Bidirectional mitral isthmus block was confirmed by demonstrating (1) a parallel corridor of double potentials during coronary sinus (CS) pacing, (2) an activation detour by pacing either side of the line, and (3) differential pacing techniques. Isolation of all PVs and cavotricuspid isthmus ablation were performed successfully in all. Mitral isthmus block was achieved in 92 patients after 20+/-10 minutes of endocardial radiofrequency application and an additional 5+/-4 minutes of epicardial radiofrequency application from within the CS in 68, resulting in a conduction delay of 151+/-26 ms during CS pacing. Thirty-two patients with mitral isthmus ablation compared with 49 without had recurrent atrial arrhythmia (P=0.02) requiring further ablation. At 1 year after the last procedure, 87 patients with mitral isthmus ablation and 69 without (P=0.002) were arrhythmia free without antiarrhythmic drugs, mitral isthmus ablation being the only factor associated with long-term success (RR for AF recurrence, 0.2; CI, 0.1 to 0.4; P<0.001). CONCLUSIONS: Catheter ablation of the mitral isthmus results consistently in demonstrable conduction block and is associated with a high cure rate for paroxysmal AF.

Aged↗
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

Prospective randomised comparison of irrigated-tip and large-tip catheter ablation of cavotricuspid isthmus-dependent atrial flutter.

BACKGROUND: Radiofrequency (RF) ablation of cavotricuspid isthmus (CTI) dependent flutter can be performed using different types of ablation catheters. It has been proposed that irrigated and large-tip catheters are capable of creating larger lesions, resulting in greater efficacy. This prospective, randomised clinical study compared the efficacy of irrigated and large-tip catheters of different designs. METHODS: Eighty patients (69 men, 66+/-11 years) undergoing de novo RF ablation of CTI-dependent flutter were randomised to ablation using one of the following catheters: (i) externally-irrigated 20), (ii) internally-cooled (n=20), (iii) single sensor, 8-mm tip (n=20), or (iv) double sensor, 8-mm tip (n=20). The study endpoint was the demonstration of bidirectional CTI conduction block within 12 min of cumulative RF delivery. Crossover to the externally-irrigated catheter was permitted if this was not achieved. The ablation and procedural parameters, safety and efficacy were compared. RESULTS: The primary endpoint was achieved in 64 patients (80%), including all 20 patients randomised to the externally-irrigated catheter. Crossover was required in 16 patients: 9 initially using the internally-cooled catheter (45%), 3 using single-sensor, 8-mm-tip (15%), and 4 using double-sensor, 8-mm-tip (20%) catheters. The higher initial failure rate with the internally-cooled-tip catheter was significant compared to the externally-irrigated (p = 0.001) and single-sensor, 8-mm-tip (p = 0.04) catheters. The externally-irrigated catheter achieved the study endpoint more frequently with fewer RF applications of shorter duration compared to the internally-cooled-tip catheter and 8-mm-tip catheters, the difference being significant compared with internally cooled ablation. No major complications were observed. CONCLUSION: Among commonly used ablation catheters, the externally-irrigated catheter has a higher efficacy for rapid achievement of CTI block.

Aged↗
PubMed2004

"Dormant" pulmonary vein conduction revealed by adenosine after ostial radiofrequency catheter ablation.

INTRODUCTION: The endogenous nucleoside adenosine is an important intermediate in cellular metabolism, a regulator of function in many organ systems, and a pharmacologic agent with potent electrophysiologic effects. We studied the effects of adenosine on the activation of the pulmonary veins (PVs) after successful ostial isolation in patients with atrial fibrillation (AF). METHODS AND RESULTS: Twenty-nine patients (21 male; mean age 54 +/- 10 years) with refractory highly symptomatic persistent (n = 9) or paroxysmal (n = 20) AF were included in the study. PV isolation was performed using radiofrequency catheter ablation guided by a multipolar basket catheter (Constellation, Boston Scientific). After successful PV isolation, we studied the effects of intravenous adenosine (12-18 mg) on activation of the upper PVs. A total of 83 PVs were successfully isolated. After adenosine, PV activity was recorded in 10 (34%) of 29 left upper PVs studied and in 3 (13%) of 24 right upper PVs, coupled to atrial activity for 20 +/- 7 seconds (adenosine positive). In 8 (62%) of 13 cases, PV potentials were recorded in the distal electrodes of the basket catheter only. Dissociated PV rhythms (N = 8) present after PV isolation disappeared after adenosine for 18 +/- 7 seconds, even if reconduction was missing. In 14 patients (48%), a second EP study was performed for recurrence of AF. Adenosine-positive PVs had a nonsignificant higher rate of recovery of conduction than adenosine-negative veins (71% vs 35%, P = 0.095). CONCLUSION: Adenosine induces transient conduction in 25% of PVs following successful isolation. Further studies are necessary to determine the physiologic or pathophysiologic role of adenosine-induced reconduction in human hearts or other organ systems.

Adenosine↗
PubMed2003

Reverse remodeling of sinus node function after catheter ablation of atrial fibrillation in patients with prolonged sinus pauses.

BACKGROUND: Symptomatic prolonged sinus pauses on termination of atrial fibrillation (AF) are an indication for pacemaker implantation. We evaluated sinus node function and clinical outcome in patients with prolonged sinus pauses on termination of arrhythmia who underwent ablation of paroxysmal AF. METHODS AND RESULTS: Twenty patients with paroxysmal AF and prolonged sinus pauses (> or =3 seconds) on termination of AF underwent ablation between May 1995 and November 2002. Patients with sinus pauses independent of episodes of AF were excluded from the analysis. The procedure included pulmonary vein and linear atrial ablation. After ablation, sinus node function was assessed during the first week and at 1, 3, and 6 months, by 24-hour ambulatory monitoring to determine the mean heart rate and heart rate range, and by exercise testing to determine the maximal heart rate. Corrected sinus node recovery time was determined at the completion of ablation and at 24.0+/-11.3 months at 600 and 400 ms. After AF ablation, there was a significant improvement of sinus node function, with an increase in the mean heart rate (P=0.001), maximal heart rate (P<0.0001), and heart rate range (P<0.0001). The corrected sinus node recovery time decreased in all patients evaluated at 600 ms (P=0.016) and 400 ms (P=0.019). At 26.0+/-17.6 months, 18 patients (85%) had no recurrence of AF (in the absence of medication), with no symptoms attributable to bradycardia or sinus pauses on ambulatory monitoring. Two patients had infrequent episodes of AF, 1 requiring pacemaker implantation. CONCLUSIONS: Prolonged sinus pauses after paroxysms of AF may result from depression of sinus node function that can be eliminated by curative ablation of AF. This is accompanied by improvement in parameters of sinus node function, suggesting reverse remodeling of the sinus node.

Atrial Fibrillation↗
PubMed2003

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↗
PubMed2003

Radiation exposure during radiofrequency catheter ablation for atrial fibrillation.

RF catheter ablation of paroxysmal atrial fibrillation (PAF) is associated with prolonged fluoroscopy. The procedural duration and fluoroscopic exposure to patients and medical staff were recorded and compared among 43 ablation procedures for PAF, 20 for common atrial flutter, and 16 for accessory pathways. Patient radiation exposure was measured by dosimeters placed over the xyphoid, while that of physicians and nurses was measured by dosimeters placed outside and inside the lead apron. The mean fluoroscopy time was 57 +/- 30 minutes for PAF, 20 +/- 10 minutes for common flutter, and 22 +/- 21 minutes for accessory pathway ablation. The patient median radiation exposure was 1110 microSv for PAF, compared with 500 microSv for common flutter and 560 microSv for accessory pathway ablation (P < 0.01). The median radiation exposure to physician and nurse inside the lead apron were, respectively, 2 microSv and 3 microSv for PAF, 1 microSv and 2 microSv for common flutter, and < 0.5 microSv and 3 microSv for accessory pathway ablations. RF catheter ablation for PAF was associated with prolonged fluoroscopy times and a twofold higher radiation exposure to the patient and physician compared with other ablation procedures. Assuming 300 procedures/year, radiation exposure to the medical staff was below the upper recommended annual dose limit.

Atrial Fibrillation↗