Effect of Ibutilide, a New Class III Agent, On Sustained Atrial Fibrillation in a Canine Model of Acute Ischemia and Myocardial Dysfunction Induced By Microembolization

The effect of ibutiJide, a new Class III antiarrhythmic agent, upon acute onset atriai fibriJIation was investigated in a closed-chest canine model of acute left ventricular fLVj dysfunction. Twenty-four anesthetized mongrel dogs, mean weight 24.9 ± 4 kg were subjected to coronary artery microsphere emboiization and volume Joading, followed by attempted induction of atrial fihrillation (AF) by rapid atrial pacing. Acute ischemic LV dysfunction was successfully induced by emboiization in aii dogs, and caused significant (P < 0.02) decreases in LV systolic pressure, peak + dp/dt (and ? dp/dtj, stroke volume, and RR interval; whereas LV end diastolic pressure and QTc significantiy increased. Sustained AF (≥ 30 min) was successfully induced in 15 of 24 dogs (62%) and unsustained AF (< 30 min) was induced in the remainder (38%). At 30 minutes after induction of sustained AF, 15 dogs were randomized to intravenous ibutiiide (0.15 mg/kg, given as a 0.075 mg/kg bolus, followed by 0.075 mg/kg infusion over 1 hour; n = 7) or placebo (saline; n = 8). There were no statistically significant differences between the ibutilide and the placebo groups with respect to mean LV systolic pressure, LV end diastoJic pressure, LV dp/dt, RR intervaJ, or QTc intervaJ during AF prior to infusion. All seven dogs receiving ibutiJide converted to sinus rhythm after a median of 3 minutes (range 0.5–26 min), whiJe onJy three of eight pJacebo dogs (P < 0.03J converted to sinus rhythm after a median duration of 30 minutes (range 15–60 min) (P < 0.04 for difference in time to conversionj. QTc prolonged by 27 ± 17%, 1 hour after ibutiJide, but was unaJtered after pJacebo (P ≥ 0.02). There were no significant hemodynamic changes after either ibutiJide or pJacebo. We concJude that: (1) sustained AF (> 30 min) can be readily induced in this closed-chest animal model and used t o test antiarrhythmic agents acutely; and (2) intravenous ibutiJide is effective in rapidJy terminating acute onset AF; the drug prolongs the QT_c intervaJ but does not exacerbate preexisting hemodynamic compromise in the acutely ischemic LV.     

Rapid Ventricular Pacing in a Pacemaker Patient Undergoing Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) generates potent electromagnetic forces in the form of a static, gradient, or pulsed radiofrequency magnetic field that can result in pacemaker malfunction. This report documents a case of rapid cardiac pacing during MRI in a patient with a dual chamber pacemaker. Although the mechanism of rapid cardiac pacing is unclear, it was directly related to radiofrequency pulsing. We postulated that the lead acts as an antenna for radiofrequency energy that interacts with the pacemaker's output circuit, thus, causing cardiac pacing at a cycle length representing a multiple of the repetition time; or perhaps rapid pacing is related to induced currents generated between the MRI unit and the pacing lead.     

Neutron activation analysis of trace elements in skin

Copper and zinc levels were estimated in serum and skin of nineteen vitiligo patients as well as in pigmented moles, seborrhoeic warts and normal skin. In seborrhoeic warts, high zinc levels were associated with excessive melanization and an abundance of ATPase+ve dendritic cells. Zinc levels were also significantly increased in pigmented moles compared with those in normal surrounding skin. In vitiligo, there was a significant reduction in serum zinc while copper levels were increased in the hyperpigmented zone surrounding the lesion. The results of copper analysis in vitiligo neither support a deficiency role for copper nor justify its use in the treatment of that disease.     

Effect of increasing depth of dexmedetomidine anesthesia on upper airway morphology in children

Objective: This prospective study examines the dose–response effects of dexmedetomidine on upper airway morphology in children with no obstructive sleep apnea (OSA). Aim: To determine the effect of increasing doses of dexmedetomidine on static and dynamic magnetic resonance (MR) images of the upper airway in spontaneously breathing children with no OSA. Background: General anesthetics and sedatives attenuate upper airway muscle activity, rendering the airway vulnerable to obstruction. Dose–response effects of dexmedetomidine on upper airway of children are not known. We prospectively examined the dose–response effects of dexmedetomidine on upper airway morphology in children. Methods/Materials: Increasing doses of dexmedetomidine was administered to 23 children scheduled for MR imaging of the brain while breathing spontaneously via the native airway. Static axial and dynamic sagittal midline MR ciné images of the upper airway were obtained during low (1 mcg·kg⁻¹·h⁻¹) and high (3 mcg·kg⁻¹·h⁻¹) doses of dexmedetomidine. The airway anteroposterior diameter, transverse diameter, and cross‐sectional areas were measured manually by two independent observers. Static airway measurements were taken at the level of the nasopharyngeal airway (sagittal images) and retroglossal airway (RGA) (sagittal and axial images). Dynamic change in cross‐sectional area of airway between inspiration and expiration was considered a measure of airway collapsibility. Results: Static axial measurements of RGA did not change with increasing dose of dexmedetomidine. Most sagittal airway dimensions demonstrated clinically modest, although statistically significant, reductions with high dose compared to low dose dexmedetomidine. Although, the dynamic changes in nasopharyngeal and retroglossal area with respiration were marginally greater for high dose than for low dose dexmedetomidine, no subject exhibited any clinical evidence of airway obstruction. Conclusion: Upper airway changes associated with increasing doses of dexmedetomidine in children with no OSA are small in magnitude and do not appear to be associated with clinical signs of airway obstruction. Even though these changes are small, all precautions to manage airway obstruction should be taken when dexmedetomidine is used for sedation.     

Immediate and Long-Term Outcome of Redo Percutaneous Mitral Valvuloplasty: Comparison with Initial Procedure in Patients with Rheumatic Mitral Restenosis

Aims: We explored the immediate and long-term outcome of redo percutaneous mitral valvuloplasty (PMV) in a series of patients with mitral restenosis in comparison with initial PMV in the same series.
Methods: We enrolled 40 consecutive patients presenting with mitral restenosis after successful initial PMV. Redo PMV was performed by the antegrade transseptal approach using either the Inoue technique or the multitrack technique. Reassessment by transthoracic echocardiography was repeated 48 hours later, and annually thereafter. Procedural success was defined as 50% or more increase of mitral valve area (MVA) with a final MVA ≥1.5 cm², without major complications. Restenosis was defined as loss of >50% of the initial gain of MVA by the preceding PMV with a final MVA <1.5 cm².
Results: Procedural success was achieved in 37 (92.5%) patients. Both the initial and redo procedures were similar concerning the final MVA and mean transmitral pressure gradient (P > 0.05 for all). The gain of MVA was higher in the initial as compared to the redo procedure (P < 0.001). The initial mitral valve score correlated negatively with the final MVA in both the initial and redo procedures, and was the only independent predictor of the time to redo procedure, by multivariate regression analysis. At long-term follow-up (61 ± 2.8 months), the mean MVA was 1.6 ± 0.3 cm². Three patients—out of 12 available for follow-up—developed restenosis.
Conclusion: Redo PMV for mitral restenosis is feasible, safe, and achieves immediate and long-term outcome comparable to initial PMV. (J Interven Cardiol 2010;23:1–6)