Electrophysiological Studies on Cardiac Catheter Ablation

Clinical and animal investigations have pointed out that high energy electrical shocks are associated with the development of cardiac arrhythmias and with variable success in permanent ablation. The effects of electrode configuration and location on the size of the recorded electrogram was investigated to help explain variable catheter ablation results. We analyzed the cellular effects of catheter ablation shocks and found depression of resting potential, action potential amplitude, dV/dt and action potential duration. The most severe effects were noted with high current densities in tissues located between the cathode and anode. Damage was worse nearest the cathode. Similar cellular studies were completed using argon laser photoablation. Again, there was a decrease in resting potential, action potential amplitude and dV/dt. Laser energy led to a more focal region of myocardium void of action potentials and the border zone of injury was smaller. We also investigated the effects of lower energy shocks)1 to 10 joule) on cardiac tissues. Using microelectrodes, we observed that the membrane potential can "hang up" at the depolarized levels for varying periods of time and that conduction is altered during this membrane "hang-up" period. The duration and membrane hang-up level correlated with shock intensity and shock duration. Sequential shocks resulted in additive membrane "hang-up". We believe that membrane hang-up may be associated with brief arrhythmias observed following catheter ablation since conduction, refractoriness and excitability are all altered.     

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.     

Candida onychomycosis—an evaluation of the role of Candida species in nail disease

Nail infections caused by Candida species are normally associated with chronic paronychia or chronic mucocutaneous candidiasis (CMCC). However, the role of Candida in the pathogenesis of other primary nail dystrophies has been questioned in view of their response to antifungal therapy alone. In the present study of 86 patients with primary nail dystrophies from which Candida was isolated, three patterns of nail involvement were found. Nineteen patients, of whom 17 had CMCC, had total dystrophic onychomycosis of at least two nails. The second group consisted of 27 patients with paronychia and lateral onycholysis. In a further 40 patients, who did not have paronychia, Candida was isolated from nails showing primary distal and lateral onycholysis. These changes were mainly seen in patients with peripheral vascular disease, particularly Raynaud's disease, or Cushing's syndrome. Nail biopsies from patients in the latter two groups confirmed the presence of yeasts and mycelium in the nail plate and 17 (46%) of those receiving antifungal therapy with ketoconazole or itraconazole showed complete clearance of the nail dystrophy. Good responses to therapy were seen more frequently in patients with peripheral vascular disease or Cushing's syndrome of whom 15 (72%) recovered; distal erosion of the nail plate, mycelium in the nail plate on biopsy or direct microscopy together with the isolation of C. albicans were all associated with good responses to antifungals. In addition to patients with CMCC or paronychia, therefore, Candida appears to be a significant pathogen in some patients with primary onycholysis of the finger nails, particularly where there is underlying peripheral vascular disease or Cushing's syndrome.     

Intrathoracic Impedance Preceding Ventricular Tachyarrhythmia Episodes

Background: Heart failure is associated with ventricular tachyarrhythmias (VT/VF). Fluid accumulation during worsened heart failure may trigger VT/VF. Increased intrathoracic impedance has been correlated with fluid accumulation during heart failure. Implanted defibrillators capable of daily measures of intrathoracic impedance allow correlation of impedance with occurrence of VT/VF. We hypothesized that VT/VF episodes are preceded by decreases in intrathoracic impedance. The goal was to identify the relationship of intrathoracic impedance measured by implanted cardioverter defibrillators to the occurrence of VT/VF. Method: Implanted defibrillator follow‐up data were obtained retrospectively. Those with Medtronic OptiVol (Medtronic Inc., Minneapolis, MN, USA), storing averaged daily and reference impedance values, were reviewed for VT/VF episodes. Impedance changes in the week leading up to VT/VF were analyzed. Results: A total of 317 VT/VF episodes in a cohort of 121 patients’ follow‐up data were evaluated. Averaged daily intrathoracic impedance declined preceding 64% of VT/VF episodes, with an average decline of 0.46 ± 0.35 Ohms from the day before the VT/VF episodes. However, the mean values of the averaged daily and reference impedance did not change significantly. A novel measure, ΔTI, the sum of the daily differences between the averaged daily and reference impedance, was negative preceding 66% of VT/VF episodes (P < 0.001). The mean ΔTI was ?4.0 ± 1.3 Ohms, which was significantly lower than the theoretically expected value of zero Ohms (P < 0.01). Conclusion: (1) Averaged daily impedance declined preceding 64% of VT/VF episodes, but the overall decline was of small magnitude; (2) a novel measure, ΔTI, was negative preceding 66% of VT/VF episodes, and significantly below zero. (PACE 2010; 33:960–966)     

Fat delays emptying but increases forward and backward antral flow as assessed by flow-sensitive magnetic resonance imaging

Flow has been assessed in the gastric antrum using a velocity-sensitive version of the high-speed magnetic resonance imaging technique, echo planar imaging (EPI). Eight healthy volunteers attended fasted on three separate days and consumed 800 mL of either a 5% glucose (0.2 kcal mL-1), 10% glucose (0.4 kcal mL-1) or an isotonic mixed nutrient meal, Fresubin (1 kcal mL-1, 27.2 g fat). Gastric volumes were obtained at 10-min intervals for 1 h. Flow measurements were performed on a single slice through the antropyloric region 5 and 35 min after meal ingestion. Gastric volumes at 45 min were inversely proportional to the calorie density of the meal with (mean +/- SEM) 89 +/- 10%* of the Fresubin, 64 +/- 5%* of the 10% glucose and 41 +/- 5% of the 5% glucose remaining (*P < 0.005 vs 5% glucose). Substantial forward and backward antral flow was observed after all three meals in the initial 5-min imaging period. AT 35 min flow activity was significantly greater after both the high-calorie meals relative to the 5% meal (total number of flow events: Fresubin = 6.6 +/- 1.7,[symbol: see text] 10% glucose = 9.9 +/- 2.2, [symbol: see text] 5% glucose = 2.5 +/- 0.9,[symbol: see text] P < 0.03,[symbol: see text] P < 0.007 vs 5% glucose, n = 8). Peak forward velocities for the initial phase of emptying tended to be greater for the rapidly emptying 5% meal (5.9 +/- 0.8 cm-1) compared with the Fresubin (3.3 +/- 0.6 cm-1, P < 0.069, n = 8) and the 10% glucose (2.9 +/- 1.0 cm-1, P < 0.068, n = 8) meals. In spite of delayed gastric emptying, high-calorie meals were associated with substantial to and fro movements which may be important for meal tritruration and fat emulsification.