Successful treatment of medically refractory ventricular fibrillation with emergency cardiopulmonary bypass in an adolescent with corrected complex congenital heart disease.
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Adolescent↗
Biomedical subjects
J Kratz
Publications and source records attributed to J Kratz.
Chronotropic incompetence: a common and progressive finding in pacemaker patients.
Thirty-eight patients (ages 40 to 77 years, mean 63) followed in a pacemaker clinic underwent exercise treadmill tests to determine chronotropic incompetence. There were 28 men and 10 women. Twenty-seven patients had atrioventricular (AV) block and 11 patients had sick sinus syndrome. All patients were exercised to fatigue. None of the patients were receiving beta-blockers or other drugs that could reduce heart rate. Maximum heart rate (MHR) and percent predicted maximum heart rate (% PMHR) were used as an index of chronotropic incompetence. Chronotropic incompetence was defined as inability to achieve a % PMHR of greater than 80%. The overall incidence of chronotropic incompetence was 58% (22 of 38 patients). We examined the relationship between chronotropic incompetence and the time to pacemaker implantation. We found that in patients who had pacemakers for less than 2 years, the mean MHR was 125 +/- 21.6 beats/min compared with 111.9 +/- 23.6 beats/min for patients who had pacemakers implanted for longer than 4 years. Similarly, the mean % PMHR decreased from 76.5 +/- 12.5% to 68.7 +/- 15.4% in patients with pacemakers less than 2 years versus those with pacemakers for more than 4 years. Fifty-three percent of the patients with a pacemaker less than 2 years old were chronotropic incompetent versus 70% of the patients with a pacemaker more than 4 years old. These data suggest that chronotropic incompetence worsens with time after pacemaker implant. To further support this, eight patients with AV block underwent a second stress test an average of 2 years following the first.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Identification of two distinct microtubule binding domains on recombinant rat MAP 1B.
A set of partially overlapping cDNA clones covering 9 kb of continuous sequence encoding the high molecular weight microtubule-associated protein (MAP) 1B, was isolated from a rat brain library in lambda gt11. The protein encoded was immunoreactive with monoclonal antibodies raised against calf MAP 1B, rat MAP 1X, and rat MAP 5, as shown by immunoblotting. Using Northern blot analysis, it was shown that the level of MAP 1B mRNA increased dramatically upon nerve growth factor-induced PC12 cell differentiation. The expression of polypeptides encoded by cDNA constructs, in conjunction with microtubule binding assays, revealed two separate microtubule binding domains, corresponding to sequences at the 5' and 3' end of the mRNA. As shown by DNA sequencing, the binding domain encoded by 5' terminal sequences consisted of the basic repeat motif KKEE(I/V), previously identified in mouse MAP 1B (Noble, M., S. A. Lewis, N. J. Cowan, J. Cell Biol. 109, 3367-3376 (1989)). The second binding domain, too, was found to be basic, but without any apparent repeat structure. It is concluded that single proteolytically unprocessed MAP 1B molecules would have the potential to function as microtubule cross-linkers.
Amino Acid Sequence↗
Single- versus dual-chamber sensor-driven pacing: comparison of cardiac outputs.
Previous studies have shown that single-chamber sensor-driven pacing improves exercise tolerance for patients with chronotropic incompetence. However, long-term single-chamber pacing has a number of inherent problems that limit its usefulness. Although sensor-driven dual-chamber pacing largely obviates the problems inherent with single-chamber sensor-driven pacing, the physiologic benefit of dual-chamber sensor-driven pacing has not yet been demonstrated. Accordingly, the purpose of this study was to compare exercise-induced cardiac output for patients with chronotropic incompetence, after programming their pacemakers to either a simulated sensor-driven single or simulated dual-chamber mode. Cardiac output was measured noninvasively at rest and peak exercise using standard Doppler-derived measurements, obtained in a blinded fashion. At rest the Doppler-derived resting VVI and DDD cardiac outputs were 4.49 +/- 0.3 L/min and 4.68 +/- 0.3 L/min, respectively. At peak exercise, the DDD cardiac output was 5.07 +/- 0.5 L/min, whereas the simulated activity VVI and DDD cardiac outputs were 6.33 +/- 0.6 L/min and 7.41 +/- 0.70 L/min, respectively. Analysis of variance showed that there was an overall significant difference in cardiac output from rest to peak exercise (p less than 0.001). However, only the simulated activity DDD cardiac output was significantly different from its respective control value (p less than 0.05). Thus this study shows for the first time that the addition of rate responsiveness to dual-chamber pacing results in a significant improvement in cardiac output for patients with chronotropic incompetence.
Aged↗
The subpectoral pocket: the preferred implant site for pediatric pacemakers.
Implantation technique for pediatric pacemaking has evolved from predominantly epicardial to predominantly endocardial. One of the potential problems with endocardial pacing in children is their very thin subcutaneous tissue, which can result in an unpleasant cosmetic result. The superficialness of the pacemaker pulse generator also may render it more susceptible to erosion and infection. A series is presented of pediatric patients who underwent implantation of a transvenous bipolar pacing system in the pediatric catheterization laboratory. The pacemaker was implanted under the pectoralis major muscle after a muscle spreading incision was made. The lead was also introduced into the subclavian vein under the pectoralis muscle. No complications resulted, and the cosmetic result was judged to be good to excellent by the parents and physicians. No infections or erosions occurred. The subpectoral pocket is recommended as the preferred site for implantation of transvenous pacemakers in pediatric patients.
Adolescent↗
Evaluation and management of tricuspid valve disease.
The four groups of pathophysiologic changes of the tricuspid valve are discussed; these include functional insufficiency, organic insufficiency, stenosis, and congenital defects. A thorough understanding of these underlying abnormal changes has led to the ability to correct malfunction of the tricuspid valve in a reliable manner.
Endocarditis↗
Is activity sensored pacing in children and young adults a feasible option?
Activity sensing pacemakers are being utilized with increasing frequency in adults, but less frequently in the pediatric and young adult age group. We evaluated 12 young patients with activity sensing devices. Seven of the implanted devices were VVIRO, four were DDDRO and one was AAIRO. Patients ranged in age from 1-21 years, mean 9.3 years, median 8 years. Weights ranged from 8.25 to 80 kgs, mean 35 kgs, median 27.6 kgs. Anatomical diagnoses revealed six normal hearts, two P/O tetralogy, one P/O transposition, two P/O ablations, and one P/O Fontan. Rhythm diagnoses included congenital complete atrioventricular block in five, acquired complete atrioventricular block in three, sinus bradycardia in two, and His-bundle catheter ablation in one patient. Rate responsive settings of medium and 7 were used in 10 out of 12 patients. Treadmill exercise testing showed that 5 out of 7 patients' rates were controlled by the activity sensor at peak exercise while two were tracking sinus rhythm (average rate increase was 76.8 ppm in the five patients). Ambulatory monitoring revealed that 10 out of 12 patients used their activity sensor to control their heart rate (average rate increase was 54 ppm). Follow-up has ranged from 1-26 months, mean 6.8 months, median 5.5 months. There was one death. Effective rate modulated, activity sensing pacing was achieved in 7 out of 9 young patients. It should be considered when the atrium itself is not a feasible sensor.
Adolescent↗
Interventional treatment for ventricular arrhythmias: the initial South Carolina case.
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Aged↗
Atrial tracking (synchronous) pacing in a pediatric and young adult population.
One hundred pediatric and young adult patients underwent implantation of an atrial tracking pacemaker. Seventy-four pacemakers paced in an atrioventricular (AV) sequential mode at the lower rate limit (DDD) while 26 paced in a ventricular demand mode at the lower rate limit (VDD). Five patients required reoperation during follow-up of 1 month to 2.5 years (mean 1.5 years). Six additional patients required programming to ventricular demand (3) or AV sequential (3) pacing, because of development of sinus bradycardia (2), atrial sensing problems (1) or pacemaker-mediated tachycardia (3). Pulse generators that could sense atrial signals less than 1.0 mV and had a programmable atrial refractory period did not require reprogramming out of the atrial tracking mode. No patient developed atrial flutter or fibrillation. Sensing problems during exercise occurred in 37% of the first 60 pacemakers but in none of the last 40, which had improved electronic components. Atrial tracking pacing is feasible in pediatric and young adult patients.
Adolescent↗
R1767, an example of the evolution of resistance plasmids.
The Salmonella R-factor system R1767 undergoes frequent rearrangement of its plasmid components. The flux of genetic material within this plasmid system depends on a combination of illegitimate and homologous recombination. The presence of several copies of IS160 and two multiresistance transposons, Tn2410 and Tn2411, are substantial reasons for the observed variations.
Biological Evolution↗
Transposable multiresistance.
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Bacteria↗
Evolution of Tn21-related transposons: isolation of Tn2425, which harbours IS161.
The isolation of two multi-resistance transposons, Tn2425 and Tn1831, and their relation to Tn21 and Tn2424, is described. A 1.7 kb segment present in Tn2424 and Tn2425 was identified as an IS element by rec-independent transposition, resulting in a cointegrate structure that carries two direct repeated copies of the IS element. By the isolation of this IS element we demonstrated that transposition is one mechanism leading to sequence variations in Tn21-like structures, especially in the region between the mer operon and the sul gene.
Ampicillin↗