Biomedical subjects
Publications and source records attributed to Martin Green.
The authors report a case of transient left ventricular apical ballooning after a prolonged electrophysiology procedure. Interventional electrophysiologists should be aware of this syndrome as a potential complication.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Surveys of pacing practice have shown a steady increase in pacemaker implantation rates in the past 15 years, despite no major changes in United States guidelines for permanent pacing. There are no data to explain why this is occurring. In this study, records were extracted from the National Hospital Discharge Survey to investigate this. There were 3 major findings. First, age-adjusted implantation rates increased progressively over the study period from 370 per million in 1990 to 612 per million in 2002. Second, it was found that the escalating implantation rate is attributable to increasing implantation for isolated sinus node dysfunction (SND). Implantation for SND increased significantly over the study period (by 102%), whereas implantation for all other indications did not. The increasing implantation for SND is due primarily to the increasing prevalence of SND, with a lesser increase in implantation rate relative to prevalence rate. The third major finding of this study is that there has been a progressive relative and absolute increase in the dual-chamber implantation rate. In 2002, 82.8% of all initial pacemaker implantations were dual-chamber devices. Furthermore, the National Hospital Discharge Survey data indicate that the major randomized pacing trials seem to have had no impact on pacing practice in the United States. In conclusion, age-adjusted implantation rates increased progressively over the study period. This escalating implantation rate is primarily attributable to increasing implantation for SND.
BACKGROUND: Numerous reports have demonstrated an association between autonomic tone and atrial fibrillation (AF). Pulmonary vein (PV) denervation during catheter ablation of AF has been shown to significantly reduce recurrence of AF. OBJECTIVES: The purpose of this study was to assess the safety and efficacy of high-frequency stimulation at mapping cardiac ganglionated plexuses in patients undergoing catheter ablation of AF. METHODS: Fourteen patients with a history of symptomatic AF underwent a single transseptal approach and electroanatomic mapping of the left atrium, right atrium, and coronary sinus. Using high-frequency stimulation with patients under general anesthesia (20-50 Hz, 5-15 V, pulse width 10 ms), mapping of ganglionated plexuses was performed. Radiofrequency (RF) ablation was performed during AF guided by complex fractionated atrial electrograms. Lesions were mostly delivered circumferentially in the antral area of the PVs, predominantly over and adjacent to regions of ganglionated plexuses. RESULTS: There was a mean of 4 +/- 1 (range 2-6) ganglionated plexuses per patient, and a mean total of 3 +/- 1 RF applications were delivered over positive vagal sites. Although a vagal response occurred infrequently during ablation (0.9%), postablation high-frequency stimulation failed to provoke a vagal response in 30 (88%) of 34 previously positive vagal sites that underwent ablation. CONCLUSION: Ganglionated plexuses can be precisely mapped using high-frequency stimulation and are located predominantly in the path of lesions delivered during ablation of AF. Objective documentation of modification of autonomic tone can be documented in the majority of patients. Future studies are required to determine the specific role of mapping and targeting of ganglionated plexuses in patients undergoing catheter ablation of AF.
OBJECTIVES: The purpose of this study was to evaluate the associations of transthoracic echocardiographic parameters with recurrent atrial fibrillation (AF) and/or stroke. BACKGROUND: The Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) study, an evaluation of elderly patients with AF at risk for stroke, provided an opportunity to evaluate the implications of echocardiographic parameters in patients with AF. METHODS: Transthoracic echocardiographic measures of mitral regurgitation (MR), left atrial (LA) diameter, and left ventricular (LV) function were evaluated in the AFFIRM rate- and rhythm-control patients who had sinus rhythm resume and had these data available. Risk for recurrent AF or stroke was evaluated with respect to transthoracic echocardiographic measures. RESULTS: Of 2,474 patients studied, 457 had > or =2(+)/4(+) MR, and 726 had a LA diameter >4.5 cm. The LV ejection fraction was abnormal in 543 patients. The cumulative probabilities of at least one AF recurrence/stroke were 46%/1% after 1 year and 84%/5% by the end of the trial (> 5 years), respectively. Multivariate analysis showed that randomization to the rhythm-control arm (hazard ratio [HR] = 0.64; p < 0.0001) and a qualifying episode of AF being the first known episode (HR = 0.70; p < 0.0001) were associated with decreased risk. Duration of qualifying AF episode >48 h (HR = 1.55; p < 0.0001) and LA diameter (p = 0.008) were associated with an increased risk of recurrent AF. Recurrent AF was more likely with larger LA diameters (HR = 1.21, 1.16, and 1.32 for mild, moderate, and severe enlargement, respectively). No transthoracic echocardiographic measures were associated with risk of stroke. CONCLUSIONS: In the AFFIRM study, large transthoracic echocardiographic LA diameters were associated with recurrent AF, but no measured echocardiographic parameter was associated with stroke.
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.
BACKGROUND: The relative contribution of the atrial septum and interatrial connections to biatrial activation is a fundamental concept of human cardiac electrophysiology that has yet to be fully characterized. The purpose of the present study was to determine how both atria are coupled electrically. METHODS AND RESULTS: Twenty patients (16 men; mean age 54+/-11years) with a history of symptomatic atrial fibrillation (AF) underwent simultaneous biatrial noncontact mapping before catheter ablation of AF. The multiple electrode array catheters were positioned, respectively, in the left atrium (LA; transseptally) and the right atrium (RA). In all but 2 patients, isopotential maps revealed that endocardial septal activations of the RA and LA were separate, independent, and asynchronous of each other. Interatrial conduction was related to the site of initial atrial depolarization, revealing conduction over Bachmann's bundle in all patients during sinus rhythm, high RA pacing, and pacing from the LA appendage. Pacing from the coronary sinus was associated with conduction over the interatrial connection at the level of the coronary sinus in all patients, and conduction over Bachmann's bundle also occurred in 5 (26%) of 19 patients. Interatrial conduction over the fossa ovalis occurred in only 2 (2%) of the 116 segments analyzed. CONCLUSIONS: Electrical coupling of the RA and LA in humans is predominantly provided by muscular connections at the level of Bachmann's bundle and the coronary sinus. The true septum (the fossa ovalis and its limbus) of the RA and LA is asynchronous and discordant, usually without contralateral conduction during sinus rhythm or atrial pacing.
Explore the source record for details and available documents.
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.
Biatrial pacing is a promising new therapy for drug refractory AF. This article reports two studies. First, an initial 14-patient experience with a novel technique for biatrial pacing. The authors attempted to pace from the LA vein branches of the proximal CS for LA stimulation. LA vein pacing would potentially offer the advantages of greater interatrial synchronization and possibly greater reduction in AF burden and also of lesser far-field R wave sensing and greater lead stability. Second, a postmortem series examining the number, size, and site of LA veins draining into the proximal CS is described. LA vein pacing was successful in 9 of 14 patients. LA vein electrode parameters have been stable during a median follow-up of 580 days. There were three early lead dislodgments but no other complications. In the second study, a postmortem analysis of 43 human hearts was performed. The study found that 38 (88.4%) of 43 hearts had at least one LA vein draining into the proximal 5 cm of the CS. In addition, 81.2% (33/43) had at least one vein greater than 4 Fr caliber. Thus, pacing in a greater proportion of patients might be achieved by the development and use of smaller (3, 4, and 5 Fr) electrodes. Furthermore, these smaller leads would obviously allow deeper advancement into the LA veins with the potential advantages of greater interatrial synchronization and lead stability and lesser far-field R wave sensing.
Gas chromatography-orthogonal acceleration time-of-flight mass spectrometry (GC-oaTOFMS) is an emerging technique offering a straightforward access to a resolving power up to 7000. This paper deals with the use of GC-oaTOFMS to identify the flavor components of a complex seafood flavor extract and to quantify furanones formed in model Maillard reactions. A seafood extract was selected as a representative example for complex food flavors and was previously analyzed using GC-quadrupole MS, leaving several molecules unidentified. GC-oaTOFMS analysis was focused on these unknowns to evaluate its potential in flavor research, particularly for determining exact masses. N-Methyldithiodimethylamine, 6-methyl-5-hepten-2-one, and tetrahydro-2,4-dimethyl-4H-pyrrolo[2,1-d]-1,3,5-dithiazine were successfully identified on the basis of the precise mass determination of their molecular ions and their major fragments. A second set of experiments was performed to test the capabilities of the GC-oaTOFMS for quantification. Calibration curves were found to be linear over a dynamic range of 10(3) for the quantification of furanones. The quantitative data obtained using GC-oaTOFMS confirmed earlier results that the formation of 4-hydroxy-2,5-dimethyl-3(2H)-furanone was favored in the xylose/glycine model reaction and 2(or 5)-ethyl-4-hydroxy-5(or 2)-methyl-3(2H)-furanone in the xylose/alanine model reaction. It was concluded that GC-oaTOFMS may become a powerful analytical tool for the flavor chemist for both identification and quantification purposes, the latter in particular when combined with stable isotope dilution assay.
Explore the source record for details and available documents.
Whether migrating birds compensate for wind drift or not is a fundamental question in bird migration research. The procedures to demonstrate and quantitatively estimate wind drift or compensation are fraught with difficulties and pitfalls. In this paper, we evaluate four methods that have been used in several studies over the past decades. We evaluate the methods by analysing a model migratory movement with a realistic scatter in flight directions, for the ideal cases of full drift and complete compensation. Results obtained with the different methods are then compared with the "true behaviour" of the model movement, illustrating that spurious patterns of drift and compensation arise in some cases. We also illustrate and evaluate the different methods of estimating drift for a real case, based on tracking radar measurements of bird migration in relation to winds. Calculating the linear regression of mean geographic track (resulting flight direction) and heading directions (directions of the birds' body axis) of a migratory movement under different wind conditions in relation to the angle alpha (the angle between mean track and heading) always provides robust and reliable results. Comparing mean flight directions between occasions with winds from the left and right of the mean flight direction of the whole migratory movement also always provides expected and correct measures of drift. In contrast, regressions of individual flight directions in relation to alpha (the angle between track and heading for the specific individuals or flocks) are liable to produce biased and spurious results, overestimating compensation/overcompensation if following winds dominate in the analysis and overestimating drift/overdrift if opposed winds are dominating. Comparing mean directions for cases with winds from the left and right in relation to individual flight directions also gives biased and spurious results unless there is full variation in wind directions or an equal distribution of crosswinds from left and right. The results of the methodological evaluation and the analysis of the real case indicate that some earlier analyses of wind drift may have to be re-evaluated.
Circumferential lesions to the pulmonary vein (PV) ostia to cause conduction block at the junction of the PV and left atrium could offer a new approach during catheter ablation of patients with paroxysmal (focal) atrial fibrillation. Diode laser can deliver energy through diffusing or ring fiber tips. In three pigs weighing between 60 and 65 kg, transseptal puncture was performed and a fiberoptic balloon catheter with a collapsed profile of 10 Fr was advanced through a sheath under fluoroscopic guidance to the ostium of the right and left PVs. The balloon was inflated with a 3-cc mixture of D2O (deuterium oxide) and contrast to deliver circumferential lesions with a 15-mm diameter x 3-mm ring width of light. Applications consisted of 3.2 to 3.8 W/cm for 120 seconds; the animals were sacrificed 3 hours after ablation for pathological examination. Photonic energy was delivered successfully to the ostium of five of the five targeted PVs, and was well tolerated hemodynamically in each animal without ectopy. Gross inspection revealed endocardial lesions at the ostium of four of five PVs, confined to the atrium in each and circumferential in three of five PVs. Microscopically, transmural coagulation necrosis of the atrium was present at the ostium of three of five PVs, and extended into the myocardial sleeves of two PVs. Photonic energy delivery using a fiberoptic balloon catheter can create circumferential lesions to the PV ostia, suggesting that this new form of energy delivery may be therapeutically advantageous for pulmonary vein ablation with need to pursue chronic studies.
BACKGROUND: The impact of atrial fibrillation (AF) and its treatment on health-related quality of life (QOL) is not well understood. We assessed QOL in patients with symptomatic AF participating in the Canadian Trial of Atrial Fibrillation. METHODS: Self-report QOL questionnaires including the Short-Form-36 (SF-36), symptom checklist (SCL) and AF Severity Scale (AFSS) were completed at baseline and 3, and 12 months after randomization. RESULTS: The study group was aged 65 +/- 10 years and 59% were male. By design, 50% of patients were randomized to amiodarone (n = 132), 25% to sotalol (n = 66), and 25% to propafenone (n = 66). Most patients had normal left ventricular function (89%). Physical (41.9 +/- 9.3 to 43.7 +/- 9.2, P =.001) and mental health (47.5 +/- 10.5 to 49.0 +/- 9.8, P =.023) summary measures from the SF-36 improved significantly from baseline to 3 months. Arrhythmia symptom frequency and severity (SCL) also improved markedly from baseline to 3 months (symptom frequency 20.4 +/- 9.4 to 16.2 +/- 9.5 and symptom severity 16.7 +/- 8.2 to 12.9 +/- 7.4, both P <.001). QOL improvements were not significantly different among the groups randomized to amiodarone, sotalol, or propafenone. However, patients with no symptomatic recurrences of AF had higher scores at 3 months on measures of global well-being than those with recurrences in the first 3 months (7.4 +/- 1.8 vs 6.9 +/- 1.8, P <.05). There were no significant QOL changes from the 3 to 12 month assessment. CONCLUSION: In patients with symptomatic AF, QOL improves after treatment, independent of the specific drug used for treatment. This is especially true for patients in whom treatment prevents AF recurrence.
Two nationwide surveys were carried out using an electronic poll of 2,000 GPs and postal questionnaires were sent to 30,000 patients with osteoarthritis (OA). Both surveys found a high level of gastro-intestinal (GI) side-effects in patients treated with non-steroidal anti-inflammatory drugs (NSAIDs). Almost every GP (97%) reported experience of patients suffering GI symptoms while on an NSAID, 38% reported patients who had been hospitalised and 4% reported patients who had died owing to NSAID-induced side-effects. Most GPs (92%) said they were concerned about GI safety when prescribing an NSAID and almost a third (32%) said they were concerned about litigation from patients who had experienced a bleed. Use of NSAIDs in OA remained high, with 44% of GPs prescribing conventional NSAIDs to at least three quarters of their patients, 57% of GPs using simple analgesia and just 12% using a cyclo-oxygenase-2 (COX-2) selective inhibitor in over 74% of patients. Some 45% of patients reported receiving NSAIDs compared with 43% on simple analgesia and 4% on COX-2 selective inhibitors. Most GPs (69%) stated that their main therapeutic objective in using an NSAID to treat OA was to control pain without GI side-effects. Almost a quarter (24%) said they used low-dose NSAIDs in the hope that this would control pain without GI side-effects. Dissatisfaction with treatment was the most common reason reported by GPs for patients on an NSAID to re-present, with 73% citing either breakthrough pain or incomplete pain relief as the most common reason for patient dissatisfaction. This mirrored the patients' perception, with 63% citing inadequate pain relief as their main reason for dissatisfaction with current painkillers compared to 17% who cited stomach upsets or irritation. Patient and GP appear to be united in their concern at the GI risks of NSAID treatment. In the light of this and recent data on the efficacy, safety profile and cost-effectiveness of COX-2 selective inhibitors, GPs should re-examine their medical management of OA.