Rise of Defibrillation Energy Requirement Under Carvedilol Therapy

MELICHERCIK, et al. : Rise of Defibrillation Energy Requirement Under Carvedilol Therapy. Carvedilol, a nonselective β1-, β2-adrenoreceptor blocking agent with α1-adrenoreceptor blocking activity, is often prescribed as an adjunctive pharmacological therapy in patients who received an ICD. Despite the new ICD technology, concomitant antiarrhythmic therapy still represents the most important concern in patients with an ICD. As illustrated by this case, carvedilol may also increase the energy requirement for internal defibrillation.     

Rate and Time Dependent Effects of D-Sotalol on the Monophasic Action Potential After Sudden Increase of the Heart Rate

Experimental and clinical data suggests that almost all Class III antiarrhythmic agents diminish their ability to prolong cardiac repolarization at fast heart rates. However, only limited data exists about the time course of efficacy decay of Class III agents after sudden increase of the heart rate. In the present study, we assessed both rate and time dependent changes of the efficacy of d-sotalol in higher stimulation frequencies following an abrupt increase in heart rate. This might imitate the situation seen in the development of paroxysmal tachycardias. Monophasic action potentials were recorded from the right ventricular apex during sinus rhythm and constant stimulation with the paced cycle length (PCL) of 550 ms, 400 ms, and 330 ms in the baseline and 20 minutes after intravenous administration of d-sotalol (2.5 mg/kg) in seven patients with documented life-threatening ventricular tachyarrhythmias. D-sotalol significantly prolonged monophasic action potential duration at different steady-state heart rates (sinus rhythm: 21.1%± 3.6%; PCL 550 ms: 16.6%± 4.3%, 400 ms: 11.2%± 2.7%, 330 ms: 5.8%± 2.1%). The prolongation is significantly shorter in higher steady-state pacing, confirming a pronounced reverse-use dependent decrease of the efficacy of d-sotalol at faster stimulation frequencies. After the abrupt increase in heart rate, the beat-to-beat adaptation of the postdrug action potential prolongation exhibits only slight reverse-use dependent shortening. The decrease of the efficacy of d-sotalol is insignificant for the first 20 consecutive beats at the stimulation frequency of the PCL of 400 msec (from 16.6% at PCL of 550 ms to 14.6% at the 20th beat of the PCL of 400 ms), and for the first ten consecutive beats at the stimulation frequency of the PCL of 330 ms (from 16.8% at PCL of 550 ms to 12.3% at the 10th beat of the PCL of 330 ms). This slow decay of action potential prolongation after an abrupt increase in heart rate might contribute to the antiarrhythmic action of d-sotalol in cardiac tachyarrhythmias.     

Significance of Supraventricular Tachyarrhythmias in Patients with Implanted Pacing Cardioverter Defibrillators

Eighty-six patients were treated with an implantable cardioverter defibrillator (ICD) because of sustained ventricalar tachycardia (VT) or ventricular fibrillation (VF). In 27 patients an epicardial system was used, in 59 patients a transvenous system with a subcutaneous patch electrode was implanted. During a mean follow-up time of 17 ± 9 months, inappropriate activations of the ICD due to supraventricular tachycardia were documented by Holter monitoring in 14 patients (16%). In 8 patients paroxysmal atrial fibrillation (AF), in 2 patients chronic AF, in 1 patient atrial flutter, and in 3 patients sinus tachycardia triggered antitachycardia pacing functions (12 patients) or internal defibrillation (2 patients). In 3 patients (5%) VT was induced by inappropriate antitachycardia pacing. In an additional 18 patients (21%) inappropriate activation of antitachycardia functions due to atrial tachyarrhythmias were suspected based on telemetry readouts or the patient's history. Inappropriate activation of ICD therapy triggered by intermittent supraventricular tachyarrhythmias is common. Further improvements of detection algorithms for supraventricular tachycardia are required in future device generations.     

Anesthetic implications of ornithine transcarbamylase deficiency

Background: Ornithine transcarbamylase deficiency (OTCD) is an X‐linked urea cycle disorder associated with potentially fatal episodes of hyperammonemia. Children with OTCD often require anesthesia. There is insufficient information regarding perioperative complications and optimal management of anesthesia in these patients. Aim: To retrospectively review the medical records of children with OTCD to ascertain the nature and frequency of peri‐procedural complications. Methods/Materials: The electronic medical records of Mayo Clinic patients with OTCD who underwent anesthesia between the dates of January 2003 and September 2009 were reviewed. Results: Nine patients with OTCD underwent 25 anesthetics using a variety of anesthetic techniques, including four major surgeries. Eleven procedures were performed prior to OTCD diagnosis and those patients were not receiving therapy for a urea cycle disorder. In the other cases, patients were on a variety of therapies for OTCD. Fourteen patients were outpatient procedures. Clinical signs of postoperative metabolic decompensation did not occur. Conclusions: In this series, patients with OTCD tolerated anesthesia well. Choice of perioperative management of OTCD and the choice of anesthetic technique should be individualized and based on clinical circumstances, but should have the underlying aim of minimizing protein catabolism. It appears patients with stable OTCD may undergo minor procedures as outpatients safely.     

The role for liver biopsy in haemophiliacs infected with the hepatitis C virus

Assessment of chronic hepatitis C virus infection requires a liver biopsy in most circumstances. There is a reluctance to perform liver biopsy in haemophiliacs because of a perceived risk of haemorrhage, although with adequate factor concentrate replacement in patients without factor concentrate inhibitors it should be safe. We report a 4-year experience of liver biopsy in patients with haemophilia infected with chronic hepatitis C virus. Of 55 patients seropositive for anti-HCV, 35 have undergone liver biopsy; the median age of this group was 33 years (range 13–68). Seven patients had a normal liver. 22 had portal tract inflammation, four with lymphoid aggregates. Mild piecemeal necrosis was observed in only two and no bile duct injury was found. 11 patients had mild mixed micro- and macro-vesicular fat. 19 patients had no evidence of fibrosis despite an estimated median duration of disease of 20 years (range 8–43). In the remaining 16 patients the maximum degree of fibrosis achieved was stage III. Patients with more significant fibrosis could not be identified on the basis of ALT or HCV RNA. There were no complications of liver biopsy in this series. Liver biopsy following a well-defined protocol in chronic hepatitis C virus haemophiliac carriers is safe in the absence of factor concentrate inhibitors. In this young group of patients without HIV infection there was no evidence of significant liver disease despite a considerable duration of disease. Performing liver biopsy allows accurate information to be given to the patient and avoids unnecessary therapy. The relative youth of this group may be important in the light of the benign histology.