Asystole Following Left Ventricular Pacing

During biventricular ICD implantation, pacing the epicardial inferior posterior-lateral surface of the left ventricle via the coronary sinus produced asystole. The proposed mechanism is a Bezold-Jarisch reflex manifested by a drop in heart rate and blood pressure through direct C fiber stimulation. (PACE 2004; 27[Pt. I]:815–817)     

Six-Month Exposure of Strain A/J Mice to Cigarette Sidestream Smoke: Cell Kinetics and Lung Tumor Data

Male strain A/J mice were exposed to sidestream smoke (SS) generatedfrom burning Kentucky 1R4F reference cigarettes. Chamber concentrationswere 4 mg/m³ of total suspended respirable particulate matter(TSP). Animals were exposed 6 hr a day, 5 days a week. One-weekcumulative labeling indices were significantly increased inthe large intrapulmonary airways during the 1st week and inthe respiratory epithelium of the nasal and maxillar turbinatesduring the first 3 weeks of exposure and then returned to controlvalues. Subsequently, signs of increased cell proliferationwere again found in the nasal and maxillar turbinates duringthe 9th and 16th exposure weeks. The experiment was terminatedafter 6 months. The number of animals bearing lung tumors wasthe same in smoke-exposed as in filtered airexposed animalsas was the average number of tumors per lung. Analysis of theDNA of individual tumors obtained from exposed and control micefor K-ras mutations suggested that exon 2 might be a specifictarget for SS. It was concluded that (1) duration of exposurewas too short or (2) concentration of TSP was too low to reveala possible carcinogenic potential of SS in strain A/J mice orthat (3) SS is not carcinogenic in strain A mice.     

Hemiazygous Coil Placement for High‐Defibrillation Thresholds in a Patient with a Right‐Sided Implantable Cardioverter Defibrillator

A 41‐year‐old man underwent implantation of a right‐sided implantable cardioverter defibrillator after removal of an infected left‐sided system. Defibrillation threshold (DFT) testing on the right‐sided system failed to convert ventricular fibrillation at maximum device output (35 J) compared with a DFT of less than 15 J on the previous left‐sided system. A single‐coil lead was selectively placed into the hemiazygous vein, which courses leftward of the spine in a posterior‐anterior projection, resulting in an improved shocking vector and reduction in DFTs to less than 25 J. (PACE 2012; 35:e10–e12)     

I NTRODUCTION TO F IRE P REVENTION,F IFTH E DITION

Objectives: To determine whether members of a ski patrol, most of whom have no off-season medical responsibilities, can successfully complete an automated external defibrillator (AED) training program prior to the ski season, and retain AED skills at the end of the season and at the beginning of the following season. Methods: A prospective educational study was conducted with 61 ski patrol personnel: 51 (84%) had no other medical training, 44 (72%) had no off-season medical duties, and 57 (93%) had no prior exposure to AEDs. Prior to the ski season (December 1, 1998), all members were trained and tested using the standard American Heart Association (AHA) AED training package and a Life-Pak 500 AED and AED Trainer donated by the Medtronic Physio-Control Corporation. Both after the ski season (April 1, 1999) and prior to the following season (October 30, 1999), with no refresher training, participants were retested with the same written and practical exams. Cochrane's linear trend test was used to compare scores on the practical and written tests over time. Results: For the three testing sessions, practical test pass rates were 95%, 92%, and 97%, and written test pass rates were 100%, 98%, and 98%. There was no change in individuals' scores on either the written test (p = 0.914) or the practical test (p = 0.413) over time. Conclusions: A heterogeneous group of ski patrollers can successfully complete an AED training course, with good skill retention both after the ski season and at the beginning of the following season.     

Signal-Averaged ECG Prior to and Serially After Thrombolytic Therapy for Acute Myocardial Infarction

Signal averaging has been performed to evaluate late potentials following infarction and the administration of thrombolytic therapy. Most studies have recorded signal-averaged electrocardiograms (SAECGs) at least 12 hours after the onset of the infarction. In this study, SAECGs were recorded before thrombolytic therapy and serially over 7–10 days following infarction in 21 patients. The high frequency QRS duration was significantly shortened at 1 and 24 hours compared to presentation (96.8 ± 11.3 ms and 93.4 ± 8.0 ms vs 103.3 ± 14.3 ms, respectively, P < 0.05) and there was an increase in the terminal voltage over time, significant at 1 hour and 3 days (57.3 ± 29.1 μV and 58.6 ± 44.7 μV vs 44.4 ± 35.5 μV, respectively, P < 0.01). Five patients met criteria for ventricular late potentials on at least one SAECG. The prevalence of late potentials was higher in patients with Q wave infarctions, or with occluded infarct related arteries. These changes in myocardial activation may be related to ischemia and reperfusion, and may not correlate with the development of a fixed substrate for reentry.     

STUDIES OF STAPHYLOCOCCAL TOXINS IN RELATION TO TOXIC EPIDERMAL NECROLYSIS (THE SCALDED SKIN SYNDROME)

Summary.— A diffusible product which causes extensive epidermal splitting in new-born mice, has been obtained from phage group II staphylococci in a highly purified form. It is free of staphylococcal α-toxin, δ-toxin and hyaluronidase and has a molecular weight of approximately 33,000. Criteria of purity are presented and the possible role of this factor in experimental T.E.N. is discussed.     

Chemical mechanism to account for artifactual formation of shortened peptides with free alpha-amino groups in solid phase peptide synthesis

The formation of terminated peptides with free α-amino groups has often been observed in stepwise solid phase peptide synthesis. This has been attributed to variable accessibility in regions of the swollen crosslinked resin supports. It is now shown that impurities in the amino acid reagents are responsible for these by-products. Thus, sec. -butyloxycarbonylamino acids were isolated from tert. -butyloxycarbonylamino acids after treatment with trifluoroacetic acid under standard deprotection conditions for the removal of the tert. -butyloxycarbonyl (Boc) group. Direct reverse phase HPLC analysis of Boc-amino acids from commercial sources also showed the sec. -Boc-amino acids as impurities present at varying levels. The sec. -Boc group was stable to treatment at room temperature with trifluoroacetic acid in dichloromethane (1:1, v/v) (half-life 7 years), but was removed by HF-anisole under the standard conditions of cleavage and deprotection of assembled peptides. In model syntheses, the level of terminated free peptides corresponded to the level of preexisting sec. -Boc-amino acid impurities present in the Boc-amino acid reagents. Use of Boc-amino acids with no detectable sec. -Boc resulted in negligible levels (< 0.05%) of terminated peptides. The problem is thus readily overcome by the use of pure Boc-amino acid starting materials and is not a reflection of a shortcoming inherent to the polymer supported nature of solid phase syntheses as has been previously suggested.     

VOOR—Nondemand Rate Modulated Pacing Necessitated by Myopotential Inhibition

This report describes the use of the temperature sensitive rate modulated nondemand pacing mode (VOOR) in a patient with significant myopotential inhibition of pacemaker output during exercise. The VOOR mode eliminated myopotential sensing which had prevented an exertion related increase in heart rate. The patient has done well with VOOH pacing for the past year. VOOR pacing is useful in selected cases.