Biomedical subjects

T Kohl

Publications and source records attributed to T Kohl.

43 records · Page 3Linked to original sources

PubMed1996

Fetal endoscopic ('Fetendo') tracheal clip.

Fetal surgery can correct several life-threatening malformations before birth. Despite recent advances in fetal surgery, preterm labor remains a major problem directly related to the large uterine incision required for fetal exposure. Fetal endoscopic surgery ("Fetendo") obviates the need for a large uterine incision and may reduce the overall risks of fetal surgery by causing less uterine trauma and ultimately less preterm labor. Temporary tracheal occlusion is a promising strategy to enlarge the lungs in fetuses with congenital diaphragmatic hernia. Using the technology developed for laparoscopic surgery and for temporary tracheal occlusion, we have developed an endoscopic technique for tracheal occlusion with an endoscopic clip in a fetal sheep model. The evolution of this technique may allow temporary tracheal occlusion without incisional hysterotomy or maternal laparotomy.

Animals↗

PubMed1996

Evaluation of umbilical venous blood flow by Doppler color flow mapping and conventional ultrasonographic methods.

Ultrasonographic measurement of umbilical venous blood flow as a reflection of placental blood flow has been used for assessment of fetal well-being. Because fetal and maternal factors may prevent satisfactory measurement of umbilical venous diameter and flow velocity, an alternative method would be helpful. We found that, in 35 human fetuses between 18 and 35 weeks of gestation, that both variables for umbilical venous flow calculation can be measured from a single Doppler color frame with close measurement agreement to conventional combined cross-sectional pulsed Doppler ultrasonographic measurements. Thus, this method provides an alternative to the conventional method or may be used for a cross-check and has the potential for automated flow calculation.

Blood Flow Velocity↗

PubMed1996

Percutaneous access to the uterus for fetal surgery.

In utero repair of selected life-threatening malformations in the human fetus is now a clinical reality, yet fetal surgery continues to pose significant risks to both the mother and the unborn child. Preterm labor is a major problem directly related to the large uterine incision required for fetal exposure. Using technology developed for laparoscopic surgery, we have devised instruments and techniques to perform fetal endoscopic surgery. We now report a percutaneous technique for direct endoscopic access to the uterus. Minimally invasive fetoscopic surgery may expand the indications for fetal surgery by decreasing fetal risks, facilitating intervention earlier in gestation, and reducing preterm labor. This technique was developed in 4 fetal lambs who underwent endoscopic intervention at 105-110 days gestation (term = 145 days). Under ultrasound guidance, a 20-gauge spinal needle was advanced through the maternal abdomen, uterus, and directly into the amniotic cavity. Warmed saline was infused through the needle to expand the amniotic cavity. Next, a 5-mm balloon-tipped trocar was placed percutaneously with ultrasound guidance into the amniotic cavity. A 5-mm laparoscope was introduced and under endoamniotic vision two more 5-mm trocars were percutaneously placed. In all four sheep a 5-mm trocar was placed percutaneously into the gravid uterus. The most difficult step was puncturing through the amniotic membranes, but the sharp tip of the trocar facilitated getting into the amniotic cavity. Excellent visualization of the fetus was obtained with minimal uterine trauma. We have developed a fetoscopic technique in sheep for percutaneous placement of trocars into the uterus using ultrasound guidance. This approach allowed excellent visualization of the fetus with significantly less uterine trauma than open fetal surgery and is an essential prerequisite for future fetal endoscopic interventions.

Animals↗

PubMed1995

Echocardiographic evaluation of congenital mitral valve anomalies in children.

Congenital mitral valve anomalies were diagnosed in 65 children, whose ages ranged from newborn to 18 years, using 2-dimensional, color, pulsed-, and continuous-wave Doppler ultrasound. Data were collected over 7.5 years from 13,400 new studies. Data in these patients were compared with those obtained by cardiac catheterization, cardiac surgery, and autopsy. We detected 4 different lesions: (1) congenital mitral stenosis with 2 papillary muscles (n = 24); (2) parachute mitral valve, with a single papillary muscle (n = 24); (3) isolated cleft in the mitral valve (n = 10); and (4) double-orifice mitral valve (n = 7). A supravalvar mitral ring was detected in 21 patients with mitral stenosis; however, it never occurred as an isolated lesion and was invariably associated with some other left ventricular inflow or outflow obstruction. The supravalvar ring was associated with a parachute deformity of the mitral valve in 17 patients; in only 4 was this abnormality associated with mitral stenosis with 2 papillary muscles. In patients with congenital mitral stenosis, the peak and mean transmitral Doppler velocities were increased significantly compared with those in controls (peak velocity 1.53 +/- 0.74 vs 0.86 +/- 0.25 m/s, respectively, p < 0.01; mean velocity 1.13 +/- 0.61 vs 0.58 +/- 0.11 m/s, respectively, p < 0.01). The correlation between mean transmitral pressure gradient obtained by Doppler and cardiac catheterization was fair (r = 0.75). However, the correlation between the mitral valve areas calculated by the Doppler pressure half-time method and by the Gorlin formula was poor (r = 0.57).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1995

Direct fetal administration of adenosine for the termination of incessant supraventricular tachycardia.

BACKGROUND: Adenosine terminates supraventricular reentry tachycardia safely and effectively in the pediatric age group. CASE: The recurrence of pretreated incessant tachycardia led to severe hydrops in a 28-week-old fetus. The tachycardia was terminated instantly with direct fetal administration of adenosine via the umbilical vein. Normal heart rate and rhythm were then preserved temporarily with digoxin and flecainide. CONCLUSION: Direct fetal adenosine administration might be helpful in the treatment of fetal reentry tachycardias if the sinus rhythm achieved quickly can be preserved by long-acting antiarrhythmic drugs. Such a combined therapeutic approach might be especially advantageous in hydropic fetuses.

Adenosine↗

PubMedDate not supplied

Fetal echocardiography: new grounds to explore during fetal cardiac intervention.

Over the past decade, revolutionary advances in ultrasound imaging technology have allowed the study of the evolution of congenital heart disease during fetal life. The frustration arising from watching the prenatal progression of severe semilunar valve obstructions and therapy-refractory fetal arrhythmias has prompted the interest in developing procedures for fetal cardiac intervention. Ultrasound techniques as the primary diagnostic and monitoring modalities in fetal medicine will play a key role in defining patient groups, peri-interventional assessment of fetal hemodynamics, and monitoring during these procedures. The purpose of this article is to provide pediatric cardiologists and perinatal medicine specialists an overview over the various technical approaches at fetal cardiac intervention and the special tasks that fetal echocardiography will have to accomplish. It also aims at illustrating the potential of fetal echocardiography for fetal selection.

Catheterization↗

PubMedDate not supplied

Simultaneous in utero assessment of AV nodal and ventricular electrophysiologic parameters in the fetal sheep heart.

BACKGROUND: Fetal tachyarrhythmias are usually of supraventricular origin. To investigate whether specific electrophysiologic properties of the fetal heart contribute to this preponderance by either favoring supraventricular tachycardias or by rendering ventricular tachycardias unlikely, we measured fetal electrophysiologic parameters in utero using transuterine fetal transesophageal electrocardiograms in fetal sheep. Since overdrive pacing may help to establish the mechanism of an arrhythmia and may be used to treat fetal tachycardias, different modes of transesophageal pacing in utero were also assessed. METHODS AND RESULTS: Decapolar electrophysiology catheters were fetoscopically inserted into the esophagus of 9 fetal sheep (pregnancy duration 94- 105 days, term = 145 days). Electrocardiograms were recorded simultaneously from all adjacent bipoles and from two pacing wires sutured onto the fetal shoulders. Pacing was attempted either via two adjacent electrodes of the intraesophageal catheter or via the most distal and most proximal electrode. Fetal cycle length, PQ, and QT intervals were close to (approx. 75 %), but fetal QRS duration was < 20 % of maternal values, thus shifting the relation between activation and repolarization towards longer excitation wave lengths. Fetal QT dispersion was small (< or = 10 ms). Atrial pacing was achieved in all fetuses using distant electrodes, and with lower thresholds when compared to closely spaced bipolar electrodes (p < 0.05). CONCLUSIONS: (I) An altered relation between ventricular activation and repolarization and a low dispersion of ventricular repolarization may protect the fetal heart against ventricular reentrant tachycardias. (II) Relatively normal fetal AV nodal conduction delay already provides one of the prerequisites for supraventricular reentrant tachycardias involving the AV node at this stage of fetal development. (III) High-rate esophageal pacing of the fetal atria is best achieved using widely spaced bipolar pacing electrodes.

Animals↗