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Biomedical subjects

H H Scheld

Publications and source records attributed to H H Scheld.

342 records · Page 19Linked to original sources
PubMed1981

Actively adhering endocardial leads for pacing in children.

Cardiac pacing in children still presents problems concerning the most favorable placement of the generator and, in particular, the growth-induced electrode complications. Whereas in infants epicardial implantation is unavoidable, one would prefer transvenous placement in older children to permit replacement or removal without extensive operative measures. The use of actively anchorable endocardial leads seems advantageous because of the possibility of placing long electrode loops in the cavity of the right atrium without increasing the risk of dislodgement. In this way overextension of the lead during growth may be avoided. Since June 1975 we have performed ventricular pacing in 10 children, aged 2 to 9 years, by using a transvenous screw-in electrode (surface 6 mm2). Acute threshold values ranged from 0.4 to 0.7 mA ap a pulse duration of 1.0 msec and sensitivity between 6.5 and 8.7 mV. Electrode function has been without complications up to now. In 6 patients we implanted programmable pacemaker systems which allowed postoperative threshold measurements. The chronic threshold value has not increased above 2.3 mA in any of these cases. In our opinion, actively anchorable endocardial leads present significant advantages for pacing in childhood.

Child↗
PubMed1979

Recovery of the heart after normothermic ischemia. Part I: Ultrastructural findings during postischemic reperfusion.

The influence of controlled ischemia on myocardial ultrastructure was investigated in isolated, metabolically supported canine hearts. Recovery of functionally normal tissue as indicated by the reversibility of morphological alterations was observed up to 60 minutes of anoxia. It was shown that prolonged reperfusion of the empty beating heart supports the recovery of normal cellular ultrastructure. Severe ischemic damage of mitochondria due to ischemia of 60 minutes was almost completely reversible after a reperfusion period of 50 minutes.

Animals↗
PubMed1978

[The influence of postischemic reperfusion on the recovery of ischemic lesions of the left ventricle (author's transl)].

In an isolated dog heart preparation the influence of normothermic ischemic arrest and recovery of the ventricular function during the period of post-ischemic reperfusion were investigated. If ischemic arrest has caused a depression of ventricular function, the functional recovery of the myocardium cannot be improved significantly by a prolonged reperfusion of the empty beating heart.

Animals↗
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↗
PubMedDate not supplied

Reproducibility of quantitative pediatric transesophageal echocardiography.

Transesophageal echocardiography (TEE) is commonly used to monitor cardiac function and to assess cavitary size. For the interpretation of quantitative echocardiographic data, the degree of their reproducibility should be considered. The variability of quantitative TEE was evaluated in this study. To assess intraobserver, beat-to-beat, interobserver, and repositioning variability, TEE examinations of 46 patients with congenital heart defects were analyzed. The mean beat-to-beat variability of 8.5% (range 4.2% to 12.3%) exceeded the mean intraobserver variability of 4.9% (1.9% to 8.1%). The mean interobserver difference between two observers was 3.4% (0.2% to 11.9%). Differences in image acquisition caused by repositioning of the transesophageal probe contributed the most (6.4% to 13.3%; mean 10.5%) to the variability of two-dimensional TEE. Changes seen on TEE studies should be interpreted as abnormal only when they exceed the total variability of this method.

Adolescent↗
PubMedDate not supplied

Perioperative myocardial injury in patients undergoing aortic valve replacement.

In cases of myocardial hypertrophy myocardial protection may be insufficient. In order to determine the factors responsible for myocardial injury we assessed myocardial injury in 54 patients undergoing isolated aortic valve replacement. In all cases hypothermic cardioplegic arrest was induced. At 13 different times we measured the serum level of creatine-kinase (CK), myocardial bound creatine-kinase (CKmb), lactic dehydrogenase (LDH), alpha-hydroxybutyrate dehydrogenase (alpha-HBDH), glutamic oxaloacetic transferase (GOT) and myoglobin. The mean duration of ischemia was 52.6 +/- 16.2 minutes and the mean time of extracorporeal circulation was 85.85 +/- 20.25 minutes. By performance of a multiple regression analysis a significant correlation between ischemia and LDH and alpha-HBDH was found; CK, GOT, LDH and alpha-HBDH correlated with duration of extracorporeal circulation. In none of the patients was a low cardiac output syndrome observed. From our results we conclude that in our study myocardial protection was sufficient and therefore the detrimental effects of extracorporeal circulation were the determining factors of enzyme release.

Adult↗
PubMedDate not supplied

Preservation of high energy phosphates in hypertrophied human myocardium.

Hypertrophied hearts are extremely vulnerable to ischemia. In 61 patients with aortic valve disease undergoing surgery we investigated the quality of myocardial protection obtained with three different methods of crystalloid cardioplegia. To exclude the influence of temperature differences the regional myocardial temperatures were continuously measured and adjusted to the same level in all patients. Before and after ischemia and after 10 minutes reperfusion myocardial biopsies were taken and the high energy phosphates and lactic acid determined. In one group St. Thomas cardioplegia was used, in another Bretschneider cardioplegia and in the third the Hamburg method. There were no significant differences between the three groups at the end of ischemia and after 10 minutes reperfusion. After 10 minutes reperfusion the metabolic alterations caused by ischemia were in part reversible. From our results we conclude that each of the cardioplegias used is able to protect a hypertrophied heart adequately against ischemia during cardiac arrest.

Adenosine Diphosphate↗
PubMedDate not supplied

Myxoma of the aortic valve in a child.

Myxomas are predominantly located in the right on left atrium. We report an unusual case of a myxoma adherent to the aortic valve. The child presented with symptoms of subaortic stenosis. By invasive methods a tumor was diagnosed located at the aortic valve. After surgical removal the child recovered soon and is doing well. According to our knowledge this is the first report of a myxoma of the aortic valve.

Aortic Valve↗
PubMedDate not supplied

Enhancement of myocardial energy potentials in man by glucose-insulin treatment before and after ischaemic heart arrest.

Thirty-six patients undergoing aortic valve replacement were investigated to ascertain whether the addition of glucose-insulin before and after ischaemic heart arrest could aid to the functional recovery of hearts following global ischaemia. One group of patients (n = 14) received glucose plus insulin from the onset of anaesthesia until crossclamping of the aorta (1 g + 1.5 U/kg bw X h). A second dose (0.5 g + 1.0 U/kg bw) was given at the end of ischaemia. 22 patients, serving as control received glucose in the same manner but without insulin. Needle biopsies from the left ventricular apex region were obtained: before starting cardiopulmonary bypass; at the end of ischaemia; and after 10 minutes of reperfusion and analyzed for its content of ATP, CP ADP and lactate. In both groups ATP and CP were significantly decreased after ischaemia and increased after reperfusion. ADP and lactate levels were elevated after ischaemia and decreased after reperfusion in the insulin-group but not in the control-group. During the total investigation period ATP- and CP-concentrations in the insulin-group were higher compared to the control-group, whereas ADP and lactate of the control-group were above the insulin-group.

Adenosine Diphosphate↗
PubMedDate not supplied

Surgical therapy of pulmonary thrombosis due to candidiasis in a premature infant.

We report a case of surgical removal of a pulmonary thrombosis in a premature infant with candidemia. The pulmonary thrombotic material contained candida albicans. Following surgical therapy the child recovered soon and candidemia did not recur. We conclude that surgical treatment of pulmonary thrombosis can be successfully done even in premature infants.

Candidiasis↗
PubMedDate not supplied

The use of expanded polytetrafluoroethylene (PTFE) grafts for myocardial revascularization.

In 18 patients necessitating aorto-coronary bypass grafting procedures in whom suitable veins were not available, 22 PTFE grafts were used in combination with 47 saphenous-vein grafts. 14 patients were studied angiographically 1-26 months after operation, with a mean follow-up of 12 months. 59% of the expanded PTFE grafts and 86% saphenous vein grafts were patent. Factors affecting PTFE graft patency were similar to those of vein grafts. We conclude, that it is reasonable to use this artificial prosthesis only when sufficient veins are not available. Expanded PTFE grafts of 3-5 mm diameter can remain patent and functional for more than 2 years.

Blood Vessel Prosthesis↗