Iatrogenic Pneumohemomediastinum Mimicking Cardiac Tamponade: A Complication of Catheter Ablation Procedure

We describe a patient who developed cardiac tamponade during electrophysiological mapping aimed at ablating an atrioventricular accessory pathway. Transesophageal echocardiography showed compression of the left pulmonary veins due to pneumohemomediastinum secondary to left subclavian vein cannulation.     

The Colchicine Method in the Study of Bone Marrow Cell Proliferation

The rate of metaphase accumulation in the bone marrow cells of AKR micetreated with colchicine was investigated. The influence of this alkaloid onthe differential count of the bone marrow cells in these animals was alsostudied. It was demonstrated that the stathmokinetic effect of colchicine onthe bone marrow cells started almost immediately after the administration ofthe drug. The number of arrested metaphases increased linearly from one-halfhour to six hours after the injection of colchicine, and then fell rapidly.

In rats injected with colchicine, the changes in the bone marrow concentration of this compound were followed for eight hours. The colchicine concentrations increased from the first to the fourth hour, and then fell rapidly, reachingthe zero level at the eighth hour.

From the results obtained, it appeared that four hours post-injection wasthe most convenient time for the study of the bone marrow proliferative activity by the colchicine method when 1.2 mg./Kg. of colchicine per body weightwas used. The fact that four hours after the injection, a mild decrease in thepercentage of mature bone marrow granulocytes was found, may represent alimiting factor, which is, however, of moderate importance in the application ofthis technic.

Submitted on May 5, 1961 Accepted on June 14, 1961     

Detection of Aldehydes in Bronchoalveolar Lavage of Rats Exposed to Ozone

We report the detection of hexanal, heptanal, and nonanal inthe bronchoalveolar lavage (BAL) of rats exposed to 0.5 to 10ppm ozone with or without simultaneous 5% CO₂. These three aldehydesprimarily result from the Criegee ozonation of specific mono-or polyunsaturated fatty acids that are present in significantamounts in the rat lung; e.g., palmitoleic acid gives heptanal,oleic gives nonanal, and linoleic and arachidonic can give hexanal.Hexanal also is produced in the ozone-initiated autoxidationof any n-6 polyunsaturated fatty acid, and thus is a measureof generalized oxidative stress. (Monounsaturated fatty acidsdo not undergo appreciable autoxidation.) This detection andquantitation of aldehydes directly demonstrates for the firsttime that unsaturated fatty acids undergo Criegee ozonationin the lung when ozone is inhaled. Exposure to ozone alone producedsmaller apparent yields of the three aldehydes than did exposureto ozone plus 5% CO₂. Hexanal, heptanal, and nonanal can bedetected in BAL of rats 5 hr after the end of the ozone exposure,but after more than 5 hr only hexanal can be found, probablyfrom ozone-induced autoxidation of n-6 PUFA that continues afterozone exposure. The measured amounts of aldehydes are low, andthat, coupled with inherent biovariability, suggests that aldehydesmay not be useful as quantitative dosimeters. However, theycan be useful biomarkers, since some of these aldehydes (e.g.,nonanal) are produced in ozone-specific pathways and aldehydesare the most easily detected among the lipid ozonation products(LOP). Furthermore, our identification of these aldehydes byBAL, coupled with our recognition that ozone itself cannot penetratefar enough into the lung to cause many of the effects associatedwith the inhalation of ozone, suggests that these aldehydes,as well as other types of LOP (such as hydroxyhydroperoxidesand Criegee ozonides), may act as signal transduction molecules,activating lipases and causing the release of inflammatory moleculesby a variety of pathways not yet entirely elucidated.     

Atrial and Ventricular Pressures in Atrial Flutter

The hemodynamic effects of atrial flutter (AF) are unknown. The purpose of the present study was to investigate the changes in atrial and ventricular pressures after induction of AF. In 23 patients with paroxysmal AF (age 59 ± 9 years), a hemodynamic study was performed both during sinus rhythm and after induction of the tachyarrhythmia. During AF, 13 patients showed a fixed 2:1 AV conduction and 10 patients showed variable conduction. Mean right and left atrial pressures increased (P < 0.001) and right and left ventricular end-diastolic pressures decreased (P < 0.001) after induction of AF. Roth the increase in mean atrial pressures and the decrease in ventricular end-diastolic pressures were present either in the patients with fixed 2:1 AV (heart rate: 133 ± 15 beats/min) or in those with variable conduction (heart rate 96 ± 15 beats/min), but were more marked in the former. AF produces an impairment of atrial function, as evidenced by the increase in mean atrial pressures and reduction in ventricular end-diastolic pressures in the absence of an elevated heart rate. The mechanisms responsible for the increase in mean atrial pressures are unknown; however, atrial contractions against closed AV valves seem to play an important role.     

Determinants of Efficacy of Atrial Pacing in Preventing Atrial Fibrillation Recurrences

Atrial Pacing in Atrial Fibrillation. Introduction: Several studies have shown that single or dual site atrial pacing is effective in reducing he frequency of recurrent atrial fibrillation (AF) in selected patients. However, it is still unclear what the best predictors are of long-term efficacy of atrial pacing. Methods and Results: Forty-seven patients with paroxysmal AF requiring demand pacing underwent electrophysiologic study and dual chamber pacemaker implant. After 4 months of follow-up, patients were divided into two groups according to the presence (group 1) or absence (group 2) of symptomatic AF recurrences. Atrial pacing markedly reduced AF recurrences in all patients. Twenty-four patients were free of arrhythmia. The basal state conduction times (CT_s) and the incremental conduction times (ICT_s), during programmed electric stimulation between the high right atrium (HRA) and the coronary sinus ostium (CS_os) but not between the HRA and the His-bundle region, were significantly longer in group 1. There was no statistical difference in the effective refractory period (ERP) recorded at the HRA, the low right atrium (LRA), and the CS_s between the two groups, whereas the differences between the greatest and least recorded ERPs measured from the HRA, LRA, and CS_os (δERP) were significantly greater in group 1 patients. Two parameters were selected by discriminant multivariate analysis, namely δCT_os (ICT-CT between HRA and CS_os and δERP. The first bad a greater relative importance in predicting AF recurrence (r²= 0.33 and r²= O.1, respectively). Conclusion: Single site atrial pacing is effective in reducing AF recurrences, with decreasing efficacy in patients with greater right atrial conduction delay and wider refractoriness dispersion.