The purposes of this study were to evaluate a method that predicts transthoracic impedance in advance of defibrillating shocks in humans and to assess the importance of transthoracic impedance in low-energy defibrillation. Via defibrillator electrodes we applied 31 kHz current to the chest during the defibrillator charge cycle, before the defibrillating shock was actually delivered. The current flow was limited by transthoracic impedance; a microprocessor monitored the predischarge current flow and determined the predischarge impedance by calibration against known resistance values. Actual impedance to the defibrillating shock was also determined and compared with the predicted impedance. With this approach we predicted impedance in 19 patients who received 66 shocks for ventricular and atrial arrhythmias. Predicted impedance (y) correlated very well with actual impedance (x): y = .90x + 11.3; r = .97. To determine the importance of impedance in defibrillation and cardioversion, we prospectively gathered data from 96 patients who received shocks of various energies for ventricular or atrial arrhythmias. In patients with high transthoracic impedance (> 97 Q), low-energy shocks (. 100 J) for ventricular defibrillation had only a 20% success rate as opposed to a 70% success rate for low-energy shocks in patients with low or average impedance (p < .05). We conclude that transthoracic impedance can be accurately predicted in advance of defibrillation and cardioversion. This method permits the preshock identification of patients with high impedance in whom attempts to defibrillate with low-energy shocks are inappropriate. Circulation 70, No. 2, 303-308, 1984. ATRIAL and ventricular arrhythmias can be terminated by a damped sinusoidal electrical shock. The operator selects the shock energy (joules), but defibrillation or cardioversion is achieved by passage of current (amperes) MethodsThe study was approved by the University of Iowa HumanResearch Committee. Data were collected prospectively from a total of 96 patients receiving shocks for ventricular fibrillation ("defibrillation") and for ventricular tachycardia, atrial fibrillation, or atrial flutter ("cardioversion"). We defined defibrillation as the conversion of ventricular fibrillation to an organized rhythm, usually sinus rhythm. We defined cardioversion as the conversion of ventricular tachycardia to a supraventricular rhythm or the conversion of atrial fibrillation or atrial flutter to sinus rhythm. The patients underwent defibrillation or cardioversion in the coronary care unit, emergency room, electrophysiology laboratory, or inpatient wards. For the initial portion of this study (impedance prediction) the electrodes used were either standard hand-held electrode paddles or self-adhesive electrode pads; the two types of electrodes are equally effective. In the second phase of the study (relationship of shock success to transthoracic impedance) we analyzed data from an ongoing, prospective study of self-adhesive, monitor-defibrillator pads for d...

The efficacy of self-adhesive electrode pads for defibrillation and cardioversion was assessed in 80 patients who received 267 shocks from self-adhesive pads. In all but two patients, defibrillation or cardioversion was achieved at least once. The pads were equally effective when used in the apex-anterior or apex-posterior position. The transthoracic impedance using self-adhesive pads was 75 +/- 21 ohms (mean +/- standard deviation), which is similar to previously reported transthoracic impedance in defibrillation, using standard hand-held electrode paddles of 67 +/- 36 ohms. It is concluded that self-adhesive electrode pads are effective for defibrillation and cardioversion.

The authors describe a preparation for a photochromic compound for the introductory organic laboratory.

In a 40 year old man with a 1 month total occlusion of a dominant right coronary artery, persistent angina despite medical management indicated inadequate coronary collateral supply to the posterolateral myocardium originally supplied by the totally occluded vessel. Initial attempts at reperfusion of the chronically occluded vessel with an angioplasty guide wire and balloon were unsuccessful. However, administration of intracoronary streptokinase resulted in partial reperfusion, after which successful wire-guided balloon angioplasty was accomplished. This case illustrates the potential utility of combining a thrombolytic agent with angioplasty in attempting reperfusion for management of selected cases of chronic total coronary artery occlusion.

We report an unusual complication of transvenous pacing: extreme coiling of a pacemaker catheter, which formed a redundant, twisted loop protruding into the right ventricular outflow tract. This may be a result of "twiddling" (rotation) of the pacemaker generator by the patient and/or inadequate fixation of the catheter at the venous entry site. Careful fixation of the generator to the venous entry site within the subcutaneous pocket may prevent such a complication.