[Shock-wave lithotripsy in choledocholithiasis in a female patient with a cardiac pacemaker]. / Litotrypse rázovou vlnou pro choledocholitiázu u nemocné s kardiostimulátorem.

BACKGROUND: Extracorporeal shock wave lithotripsy is relatively contraindicated in patients with an implanted cardiac pacemaker. Shock waves can damage the pacemaker by mechanical pressure and also by electromagnetic induction. Since the distance between the applicator and the pacemaker is small during biliary lithotripsy, the risk of damaging the pacemaker is greater. In the following case, the patient presented with a stone in the common bile duct, and had an implanted pacemaker. Lithotripsy with non-synchronized shock waves was the method of choice since conventional surgery was high risk in this specific case. CASE REPORT: In an 84-year-old woman with a stone in the proximal part of the common bile duct, endoscopic attempts of extraction failed. Therefore, shock wave lithotripsy was indicated. This patient had serious heart disease with an interference of spontaneous heart action with the pacemaker at a ratio of 1:1. We decided to treat with shock wave lithotripsy. The application of shock waves was without side effects on the patient and the pacemaker. CONCLUSION: This case is interesting as it highlights the possibility of using the Czech made MEDILIT lithotriptor in the treatment of choledocholitiasis in patients with a pacemaker. Even so, it is necessary to monitor the patient's ECG to ensure the possibility of immediate external stimulation.

A three-site programmed electrical stimulation protocol in patients with and without ventricular tachyarrhythmias.

Programmed electrical stimulation (PES) of the ventricle plays an important role in diagnosis and in testing the effect of pharmacological and non-pharmacological therapy of ventricular tachyarrhythmias. A stimulation protocol should reliably reproduce clinical ventricular tachyarrhythmia. The authors compared the results of the standard one-site protocol to those of a new test delivering extrastimuli alternately into the right and left ventricle. In group I (control group, n = 37), clinically without ventricular tachycardia, tachycardia could not be induced in any of the patients. In group II (n = 30), with clinical ventricular tachycardia, inducibility was in 22 patients using the standard test, and in 23 patients using the new test. The authors conclude that this modification of the PES protocol with alternate extrastimulus delivery into the right and left ventricle does not seem to contribute significantly to PES sensitivity compared to the standard one-site stimulation protocol. It is not clear whether or not another stimulation protocol with alternate stimulus delivery to both ventricles or to different sites in the right ventricle will raise the sensitivity, specificity and reproducibility of the PES test.

Changes in ventricular effective refractory periods after two extrastimuli and ventricular electrical instability.

Using programmed stimulation with one and three extrastimuli delivered in the right ventricular apex, we compared the effective refractory period (ERP) during sinus rhythm (ERP-SR) and during the third extrastimulus (ERP-S3) in patients without ventricular tachycardias (control group, n = 87) and in patients with documented ventricular tachycardia (VT group, n = 76). The protocol was not completed to determine ERP-S3 in one patient in the control group and in 15 patients in the VT group. We observed a significantly greater change (i.e., shortening) in ERP after two extrastimuli in the VT group compared with patients without VT (delta ERP = 45 +/- 20 msec in the control group and 70 +/- 16 msec in the VT group, P < 0.001). This electrophysiological phenomenon, along with conduction delay, may play an important role in VT induction.

Effect of stretch combined with electrical stimulation on the type of sarcomeres produced at the ends of muscle fibers.

Stretching a muscle results in a rapid addition of sarcomeres at the ends of the muscle fibers. The effect of a pattern of electrical stimulation resembling that of a slow motoneuron on the newly formed muscle tissue in a stretched, fast-contracting muscle was investigated. We found that after a period as short as 4 days, the type of sarcomeres which were added on to the ends of the existing myofibrils differed from those in the middle regions of the experimental muscles: there was a much higher proportion of type I and type IIA sarcomeres in the stretch-stimulated ends. This study showed that reprogramming of the synthesis of fiber type-specific contractile proteins can be achieved and detected within a very short time by using electrical stimulation combined with stretch.

Sine2/triangle/square wave generator for pacemaker testing.

We describe a device which generates the most widely used test signals for sensitivity measurements of noncompetitive pacemakers--sine2, triangle and square waves. The test generator can operate in free-running mode or it can be triggered by impulses from the pacemaker tested, thus enabling measurement of the sensitivity response of the pacemaker sensing circuits within the whole automatic interval, including determination of the pacemaker refractory period.

Adrenergic and cholinergic induced contractions of tracheal smooth muscle in the rabbit as demonstrated by a new in vivo method.

An in vivo tracheal muscle preparation in the rabbit was developed which enabled us to measure changes in the isometric tension of the trachealis muscle in response to electrical stimulation of autonomic nerves and to i.v. administration of autonomic agonists and antagonists. The preparation was very sensitive to injections of carbachol, and showed graded contractions to stimulation of the caudal end of the cut cervical vagus as frequency and strength of stimulation were increased. Stimulation of the rostral end of the cut cervical sympathetic nerve fibers produced contractions in all preparations. This effect was mimicked by the alpha-adrenoceptor agonist, phenylephrine. The effects of both sympathetic stimulation and phenylephrine were blocked by phentolamine and not inhibited by pretreatment with atropine or propranolol. Sympathetic stimulation produced contractions of the trachealis muscle whether the initial tone was normal or actively increased by carbachol, while adrenaline produced relaxation when the initial tone was high. Using this new in vivo trachealis muscle preparation in the rabbit, we could show that sympathetic stimulation produced contractions of the trachealis muscle. This effect is consistent with the existence of smooth muscle activating alpha adrenoceptors.

Disintegration of microorganisms and preparation of yeast cell walls in a new type of disintegrator.

Microbial cells were disintegrated in a new type of rotary disintegrator with a disc stirrer by a combination of shear force layers, collisions, and rolling of glass beads which were brought into motion by the stirrer. The rate of disintegration at a given dry bed volume of Ballotini beads and a given volume of cell suspension is proportional to the peripheral velocity of the stirrer up to 18 m/sec. Horizontal arrangement of the stirrer increases the effectiveness about five times; 100% disintegration of yeast cells was achieved under optimal conditions within 72 sec at a concentration of 3.5g (dry weight)/100 ml of suspension, and within 96 sec at a concentration of 10.5g (dry weight)/100ml. At 17.5 g (dry weight)/100 ml, the stirrer began to slip. The cell walls of yeast were obtained at the desired degree of crushing and the course of purification was determined by infrared spectral analysis.