Verapamil or Adenosine for the Immediate Treatment of Supraventricular Tachycardia

A comparison of verapamil with adenosine for the immediate treatmentof supraventricular tachycardia was made from a retrospectivereview of 164 spontaneous episodes of paroxysmal tachycardiain 43 patients. Verapamil administered to 33 patients restoredsinus rhythm in 91 of 112 episodes (81 per cent). Hypotensionoccurred in 9 per cent of episodes. Adenosine terminated 94per cent of episodes of supraventricular tachycardia in 25 patients.The arrhythmia recurred shortly after adenosine restored sinusrhythm in 20 episodes. Transient side effects were common. Fifteenpatients were treated with both agents. Adenosine was successfulin all, but verapamil failed to restore sinus rhythm at leastonce in seven of the 15 patients. Early recurrence of tachycardiaoccurred in five of these after adenosine, but in only one afterverapamil. Verapamil and adenosine are both effective in the treatmentof supraventricular tachycardia; adenosine has the higher successrate and is safer, but transient symptoms are common and arrhythmiasmay recur.     

An Automatic Microcomputer System for Analysis of Monophasic Action Potentials

A computer system for rapid measurement and analysis of monophasic action potentials (MAPs) recorded in vivo was developed. MAPs recorded from the epicardium of mongrel dogs using a contact electrode were digitized by analog-to-digital conversion at a sampling rate of 1 kHz per channel for computer data acquisition. Activation time was detected using a sliding 10-point window at the location where the average positive dV/dT exceeds an adjustable threshold value in order to eliminate spurious detection due to baseline variability or motion artifact. Action potential duration (APD) was determined at 50% and 90% (APD50, APD90) repolarization levels at the first sample point below these detection levels. In addition, a tangent algorithm (APDtan) that detects peak negative dV/dT during repolarization was developed. APDtan was determined from the location of onset of activation to the intersection of tangent and baseline. APDtan allowed estimation of APD in the presence of subsequent premature beats when APD90 was not measurable. To validate activation time measurements, 4,600 action potentials were analyzed during fixed rate pacing. Over a range of paced coupling intervals from 200 to 1000 msec, an R2 value of 0.99968 and a slope of 0.9959 were obtained by linear regression between paced and calculated intervals. To validate APD measurements, 5035 action potentials were analyzed in five animals during fixed rate pacing (longer than 3 minutes) when action potential duration should be constant. Average coefficient of variation of 1.25%, 1.65%, and 1.14% were obtained for APD50, APD90, and APDtan, respectively. This algorithm provides a rapid and accurate method to analyze MAP activation and duration for basic physiological studies such as the determination of initiation of arrhythmias.     

Hydroxyurea therapy in β-thalassaemia intermedia: improvement in haematological parameters due to enhanced β-globin synthesis

Summary. The β-thalassaemias represent a heterogenous group of diseases resulting from decreased erythroid β-globin mRNA expression and imbalanced a/β-globin chain synthesis which are manifest clinically by ineffective erythropoiesis and excessive haemolysis. Increasing levels of haemoglobin F (HbF) by pharmacological agents has been proposed to ameliorate the severity of the disease by improving the balance in globin chain synthesis. Hydroxyurea (HU), as an effective agent with low toxicity for activating 7-globin gene, has been shown to enhance HbF synthesis in experimental animals and in patients with sickle cell anaemia. However, previous trials of HU in β-thalassaemia patients are ambiguous, with a small number having increased HbF synthesis. In a recent study of HU effects in Chinese j3 -thalassaemia patients we unexpectedly found that two unrelated patients with β-thalassaemia intermedia demonstrated an improvement in the effectiveness of erythropoiesis reflected by an increase in haemoglobin concentration (from 4-1 to 6-3 g/dl, patient 1; from 6-5 to 97 g/dl, patient 2) and in red cell volume (from 68 to 104 fl, patient 1; from 68 to 85 fl, patient 2) after a period of excess of 300 d of low-dosage HU treatment. These effects, however, appear to be due to increased,3-globin biosynthesis, because the percentage of HbF decreased in each patient as total Hb increased. This was reflected by changes in the β/a ratio (from 0'301 to 0-581, patient 1; from 0'348 to 0-487, patient 2) with minimal changes in 7-globin biosynthesis. We conclude that in addition to its known effects in stimulating 7-globin production, hydroxyurea may have a more general role in augmenting globin synthesis, including β-globin in some thalassaemia intermedia patients who maintain the capacity to express normal β-globin chains.     

Use of the Saline Infusion Electrode Catheter for Improved Energy Delivery and Increased Lesion Size in Radiofrequency Catheter Ablation

Although radiofrequency catheter ablation has undergone explosive growth as the treatment for a variety of arrhythmias, a limiting factor with the existing catheter delivery system has been the relatively small size of the lesions, which appears to be in part due to coagulum formation around the catheter tip, producing a rise in impedance and limiting energy delivery. In order to test the hypothesis that infusion of saline during radiofrequency current application can increase the lesion size and decrease the incidence of impedance rise, ten dogs were each given two radiofrequency ablation lesions to the left ventricular endocardium. One of these lesions was delivered with a standard 7 French quadripolar catheter with a 2-mm tip, and the second was done with a 7 French Iuminal electrode catheter (also with a 2-mm tip) for the infusion of normal saline during the delivery of radiofrequency energy. Energy was delivered for 60 seconds at either 10 or 20 watts at two distinct sites in the left ventricle for each animal. Four to 7 days following ablation, the animals were sacrificed for pathological examination. The lesions created with the saline infusion catheter were significantly bigger than those produced with a standard catheter (7.3 × 7.0 × 5.1 vs 5.2 × 4.9 × 3.5 mm, respectively, P < 0.001). At the lower energy level (10 W), none of the animals with the saline infusion catheter experienced an impedance rise versus 3 of 5 of the animals in whom the standard catheter was used. At the higher level (20 W), only 1 of 5 dogs had an impedance rise with the saline infusion catheter versus 5 of 5 with the standard catheter. We conclude that the use of a saline infusion catheter for radiofrequency energy delivery during catheter ablation produces a significantly larger lesion than that produced with a standard catheter and is effective in preventing impedance rise.     

Outcomes in Patients Requiring Cardioversion Following Catheter Ablation of Atrial Fibrillation

Outcomes of Cardioversion Post AF Ablation.   Introduction: Early recurrence of atrial tachyarrhythmias is commonly noted after catheter ablation of atrial fibrillation (AF). The long-term outcomes of patients who require cardioversion for persistent AF after AF ablation is not known. This study reports the outcomes of patients who underwent cardioversion for persistent AF or atrial flutter following an AF ablation procedure.
Methods: The patient population comprised 55 patients (mean age 58 ± 10 years, 35% paroxysmal) who underwent catheter ablation of AF and subsequently required electrical cardioversion for persistent AF (45 patients) or atrial flutter (10 patients). Cardioversion was defined as early (within 90 days of the ablation procedure) or late (between 90 and 180 days following ablation).
Results: The mean follow-up duration was 15 ± 8 months. Forty-six of the 55 patients (84%) patients experienced recurrence during follow-up. The average time to recurrence after cardioversion was 37 days. Of the 55 patients, 8 (15%) patients had a complete success, 11 (20%) patients had a partial success and 36 patients (65%) had a failed outcome. Seven of the 43 patients (16%) who underwent early cardioversion had a complete success as opposed to one of 12 patients (8%) who underwent late cardioversion (P = 0.49).
Conclusions: This study shows that >80% of patients who undergo cardioversion for persistent AF or atrial flutter after AF ablation have recurrence. The timing of cardioversion did not affect the outcome. These findings allow clinicians to provide realistic expectations to patients regarding the long-term outcome and/or requirement for a second ablation procedure. (J Cardiovasc Electrophysiol, Vol. 21, pp. 27–32, January 2010)     

A Prospective Study Evaluating the Role of Obesity and Obstructive Sleep Apnea for Outcomes After Catheter Ablation of Atrial Fibrillation

Effect of Obesity and OSA on Outcomes Post AF Ablation . Background: Obesity and obstructive sleep apnea (OSA) have a strong association with atrial fibrillation (AF). The purpose of this study was to prospectively determine the effects of obesity, assessed by the body mass index (BMI) and OSA on the efficacy of catheter ablation of AF. Methods: The patient population consisted of 109 patients (mean age: 60 ± 10 years, 79% male, 67% paroxysmal, mean BMI 28 ± 5 kg/m²) who underwent catheter ablation of AF. Based on BMI, patients were classified as normal (<25 kg/m²), overweight (≥25 and <30 kg/m²), or obese (≥30 kg/m²). OSA was assessed by the Berlin questionnaire. Clinical success was defined as at least 90% reduction in AF burden after 3‐month blanking period. Mean duration of follow‐up was 11 ± 4 months. Results: Of the 75 patients with clinical success, 25 (33%) had normal BMI, 29 (39%) were overweight, and 21 (28%) were obese. Among the 34 patients with failed outcome, 5 (15%) had normal BMI, 14 (41%) were overweight, and 15 (44%) were obese (P = 0.04). Twenty‐eight of the 48 patients with OSA (58%) had clinical success as opposed to 47 of the 61 patients (77%) without OSA (P = 0.036). On multivariate analysis, only BMI emerged as an independent predictor of procedural failure ((OR 1.11, CI: 1.00–1.21, P = 0.03). Conclusions: The results of this prospective study show that obesity, a modifiable risk factor, is an independent predictor of procedural failure after catheter ablation of AF. Whether treating obesity may improve the results of catheter ablation of AF warrants further investigation. (J Cardiovasc Electrophysiol, Vol. 21, pp. 521‐525, May 2010)     

Measuring the Complexity of Atrial Fibrillation Electrograms

AF Electrogram Complexity. Introduction: Complex fractionated atrial electrograms (CFAE) have been identified as targets for atrial fibrillation (AF) ablation. Robust automatic algorithms to objectively classify these signals would be useful. The aim of this study was to evaluate Shannon's entropy (ShEn) and the Kolmogorov‐Smirnov (K‐S) test as a measure of signal complexity and to compare these measures with fractional intervals (FI) in distinguishing CFAE from non‐CFAE signals. Methods and Results: Electrogram recordings of 5 seconds obtained from multiple atrial sites in 13 patients (11 M, 58 ± 10 years old) undergoing AF ablation were visually examined by 4 independent reviewers. Electrograms were classified as CFAE if they met Nademanee criteria. Agreement of 3 or more reviewers was considered consensus and the resulting classification was used as the gold standard. A total of 297 recordings were examined. Of these, 107 were consensus CFAE, 111 were non‐CFAE, and 79 were equivocal or noninterpretable. FIs less than 120 ms identified CFAEs with sensitivity of 87% and specificity of 79%. ShEn, with optimal parameters using receiver‐operator characteristic curves, resulted in a sensitivity of 87% and specificity of 81% in identifying CFAE. The K‐S test resulted in an optimal sensitivity of 100% and specificity of 95% in classifying uninterpretable electrogram from all other electrograms. Conclusions: ShEn showed comparable results to FI in distinguishing CFAE from non‐CFAE without requiring user input for threshold levels. Thus, measuring electrogram complexity using ShEn may have utility in objectively and automatically identifying CFAE sites for AF ablation. (J Cardiovasc Electrophysiol, Vol. 21, pp. 649‐655, June 2010)     

Adults with cerebral palsy: a workshop to define the challenges of treating and preventing secondary musculoskeletal and neuromuscular complications in this rapidly growing population

Although the neurological injury associated with cerebral palsy (CP) is non-progressive, adults with the disorder often develop musculoskeletal and neurological symptoms, such as severe pain, chronic fatigue, and a premature decline in mobility and function, as they age. Little is known about how to manage, much less prevent, these symptoms. This paper summarizes the findings of a multi-disciplinary workshop, sponsored by the Cerebral Palsy International Research Foundation, the American Academy for Cerebral Palsy and Developmental Medicine, and Reaching for the Stars, convened to review current knowledge and begin to develop a blueprint for future research. The goals of the workshop were to (1) define the current incidence and prevalence of CP, (2) review the known complications for persons aging with CP, (3) review current understanding of physiological processes that may contribute to loss of function and premature aging in CP, (4) evaluate current treatment interventions in terms of long-term outcomes, (5) identify cutting-edge technologies in neurorehabilitation that may help prevent or treat the effects of accelerated aging for persons diagnosed with CP, and (6) identify strategies to ensure that individuals with CP receive evidence-based care as they transition from pediatric to adult-care services.     

Diabetes and Multiple Stents Independently Double the Risk of Short-term Revascularization

Several studies show worse outcome for diabetic patients after percutaneous transluminal coronary angioplasty (PTCA). There are relatively few studies evaluating outcome in the modern era of coronary stenting. We compared the incidence of death, myocardial infarction (MI), and repeat target lesion revascularization (RTLR) by PTCA or coronary artery bypass grafting (CABG) over a 6-month follow-up in 110 diabetic and 400 nondiabetic patients receiving Palmaz-Schatz stents. All patients received aspirin/ticlopidine and stents were deployed using high-pressure inflations. Seventy-five (68.2%) diabetic patients and 272 (68%) nondiabetic patients had single stents, while 35 (31.8%) diabetic and 128 (32%) nondiabetic patients had multiple stents (≥ 2stents in the same vessel). The success rate and acute major complications were not significantly different between diabetic and nondiabetic patients. There was also no significant difference in death, MI, and repeat PTCA between these two groups. Diabetic patients underwent CABG more frequently than nondiabetic patients (12.7% vs 3.2%, respectively, P =0.001) and diabetic patients also had RTLR more frequently than nondiabetic patients (25.5% vs 12.8%, respectively, P = 0.002) during 6-month follow-up. Multivariate analysis showed that diabetes and multiple stents independently contributed to the 6-month RTLR rate. Coronary stenting in diabetic patients can be carried out with a high success rate and low incidence of acute major complications. The presence of diabetes mellitus and multiple stent placement significantly increase the incidence of repeat target lesion revascularization.