Biomedical subjects
Publications and source records attributed to John Camm.
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AIMS: Recent guidelines have recommended more wide-ranging indications for the use of implantable cardioverter defibrillator (ICD) therapy, yet even more restrained previous guidelines have not been implemented for a variety of reasons. METHODS AND RESULTS: This brief review critically examines the reasons most frequently put forward to explain this failure. Contrary to the frequently repeated speculation that the risk stratification for sudden death and hence prophylactic placement of ICDs is reasonably accurate, there is little cost difference between pharmacotherapy and ICD treatment over the long term. ICD therapy does not utilize an undue proportion of the healthcare budget, and the healthcare systems in Europe can afford this therapy. CONCLUSION: Financial reasons are neither accurate nor adequate explanations for the failure of the European medical community to implement European guidelines for the implantation of ICDs for primary and secondary prevention of sudden cardiac death.
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BACKGROUND: This study investigated onset scenarios of atrial fibrillation (AF), the first phase of the Atrial Fibrillation Therapy (AFT) trial, to determine potential arrhythmogenic triggers as targets for atrial pacing algorithms that have been proposed for prevention of AF. METHODS AND RESULTS: Ninety-eight patients (58 men; age 65+/-11 years) with recurrent, symptomatic, drug-refractory AF and a conventional pacemaker indication in 31 of 98 received a dual-chamber pacemaker. Using novel diagnostic pacemaker features AF onset scenarios were prospectively evaluated in 612 AF episodes during a 2-month monitoring period, with atrial pacing limited to 40 bpm. The most common onset scenario was premature atrial complexes (PACs) before AF (48% onsets per patient), followed by bradycardia (33%), sudden onset (17%), and tachycardia (0%). Combinations of onset scenarios were frequent (median 2 different scenarios per patient). A main study finding was the significance of repetitive AF, with 33% of onsets per patient being initiated within 5 minutes of a previous AF episode. Sudden onsets were more frequent among patients with than without repetitive AF (24% versus 0% onsets per patient, P=0.011), whereas the proportion of PACs before AF was not statistically different (50% versus 37%, P=0.52); however, patients with repetitive AF had more PACs per hour (72 versus 29, P=0.023) and a higher number of AF episodes per day (17 versus 0, P=0.001) and were more likely to have at least 1 PAC-related onset (90% versus 53%, P<0.0001). CONCLUSIONS: Novel diagnostic pacemaker features allowed a detailed individual analysis of rate and rhythm changes before AF and thus uncovered a substantial intraindividual and interindividual variability of AF onset scenarios.
Treatment of atrial fibrillation (AF) has been undergoing significant changes recently. This is due partly to different mechanisms proposed for persistent and permanent AF and partly due to the introduction of energy-based techniques, providing less invasive procedures. This article aims to review the mechanisms of AF leading to the changes in clinical practice and to review the results of surgery, energy-based, and percutaneous techniques. It is difficult to compare and contrast the results of reported series in the literature due to different definitions of AF; freedom from and recurrence of it. Furthermore, in most series it is difficult to distinguish results of surgery for lone AF and AF associated with valvular heart disease and coronary artery disease.
Predominantly a disease of advancing age, atrial fibrillation (AF) is the most common sustained arrhythmia. Its prevalence is rising as the proportion of elderly people in the population continues its inexorable rise. Without more effective therapeutic interventions, AF-related cardiovascular and cerebrovascular morbidity and mortality will also continue to rise. Antiarrhythmic drugs are an essential tool in the management of AF and may be used as premedication before cardioversion; together with cardioversion to help or assist cardioversion; or given afterward to prevent recurrence. If AF recurs after one or two cardioversions, then it is usual to adopt a rate control strategy; highly symptomatic patients who fail cardioversion may benefit from ablation therapy. We are already on the threshold of a large expansion in the use of ablation therapy, a strategy that has potential to deliver dramatic improvements in outcome. Not only can AF be cured by ablative therapy, but there is also evidence that it confers functional improvement as well. It will not, however, be appropriate for all AF patients and pharmacological therapies will continue to have an important place in the management of AF. The plethora of antiarrhythmic drugs currently available for the treatment of AF is a reflection that none is wholly satisfactory, each having limited efficacy combined with poor safety and tolerability. Improved class III antiarrhythmic agents, such as dronedarone; new classes of antiarrhythmic agents, such as atrial repolarization delaying agents; and upstream therapies dealing with substrate represent potential sources of new pharmacological therapies for AF.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
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AIMS: An understanding of the temporal trends on the risks of arrhythmic death (AD) vs. non-arrhythmic deaths (NAD) after myocardial infarction (MI) is crucial in deciding the optimal timing for risk stratification and treatment window for prophylactic antiarrhythmic treatment. However, contemporary data on such information is lacking. METHODS AND RESULTS: Individual patient data were pooled from the placebo arms of EMIAT, CAMIAT, SWORD, TRACE, and DIAMOND-MI who had a recent MI and left ventricular ejection fraction (LVEF) <40% or frequent ventricular premature beats (VPBs). Temporal trends were investigated for all studies from day 45 after acute myocardial infarction (AMI) to account for different recruitment periods between trials, and then from the onset of MI for TRACE and DIAMOND-MI that recruited patients within 2 weeks after MI. In total, 3104 patients (median age 65, range: 23-92; 2471 males) were pooled from all five studies, with a total of 487 deaths at 2-year follow-up; 220 deaths were ADs and 172 were NADs. The risks of both AD and NAD were highest in the first 6 months but the risk of AD was consistently higher than that of NAD throughout the 2-year period [rate of death/100 person-year at risk (AD/NAD): 8.09/6.07 (45 days to 6 months), 4.07/3.35 (>6-12 months), 4.34/3.60 (>12-18 months), 3.76/2.77 (>18-24 months)]. There were significant interactions between the temporal trends of mortalities and gender (P=0.03) and history of hypertension (P=0.04). A similar trend was observed when mortality was measured from time of onset of MI from the combined TRACE and DIAMOND-MI dataset. CONCLUSION: Our study provided the first contemporary evidence that in high-risk post-MI patients with LVEF <40% or frequent VPBs, the risk of AD was higher than that of NAD for up to 2 years although in female patients, they became increasingly more likely to die from NAD after 6 months. Therefore, risk stratification of post-MI patient at high risk of AD remains a worthwhile exercise. However, the risks of AD (and NAD) were highest in the first 6 months after AMI and level-off thereafter, suggesting that the optimal window period for risk stratification for implantable cardioverter defibrillator after AMI is in the first 6 months.
Prevalent low-frequency (PLF) oscillation of heart rate and turbulence slope (TS) are both powerful postmyocardial infarction (MI) risk factors. Abnormal composite risk stratifier (CRS) was defined as abnormal PLF or abnormal TS when PLF was not analyzable. We compared the predictive power of CRS with the previously published predictive value of conventional electrophysiological (EP) testing based on the presence of nonsustained ventricular tachycardia (NSVT) and inducibility of sustained ventricular tachycardia/fibrillation (VT/VF) during programmed ventricular stimulation (PVS). PLF and TS were calculated from baseline Holter recordings in the placebo population of European Amiodarone Infarction Myocardial Infarction Trial (EMIAT trial) (n = 633; LVEF </= 40%; 87 deaths; 22-month follow-up). Previously established cut-off values of PLF >/= 0.1 Hz and TS </= 2.5 ms/RR were used. The clinical characteristics of the EMIAT population were similar to those of the Multicenter Unsustained Tachycardia Trial (MUSTT trial). Therefore, we compared the predictive power of CRS and conventional PVS using the values of 35% VT/VF inducibility during PVS in NSVT patients, and a 33% and 50% increase in all-cause and arrhythmic mortality, respectively, associated with VT/VF inducibility in MUSTT. Projecting the predictive power of PVS in MUSTT into the EMIAT population yielded a sensitivity of 13.8% and 14.0% and positive predictive value (PPV) of 27.9% and 14.0% for all-cause and arrhythmic mortality, respectively, whereas an abnormal CRS was associated with sensitivities of 46.0% and 46.5% and PPV of 37.4% and 18.7%. Compared with the noninvasive Holter-based CRS, invasive PVS appears inferior in the identification of high-risk post-MI patients with left ventricular dysfunction.
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