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Biomedical subjects

B E Armstrong

Publications and source records attributed to B E Armstrong.

27 records · Page 2Linked to original sources
PubMed1982

Heart block in children. Evaluation of subsidiary ventricular pacemaker recovery times and ECG tape recordings.

To evaluate subsidiary ventricular pacemaker function in 20 children with congenital or surgically induced complete heart block, we measured recovery times following overdrive ventricular pacing. Long-term ECG tape recordings were performed in eight of these children. Ages ranged from 1 month to 17 years. The resting R-R intervals ranged from 595 to 1,740 msec. The ventricles were paced at various cycle lengths of 400 to 1,000 msec with either transvenous electrode catheters or surgically implanted epicardial electrodes. His bundle recordings showed that the site of block did not allow separation of patients with symptoms from those without symptoms. Prolonged recovery times were present in patients with block above the His bundle recording site who had symptoms of syncope or dizziness, as well as in patients who had a wide QRS. However, some asymptomatic patient with heart block above the His bundle recording site also had long recovery times. None of the asymptomatic patients who had ECG tape recordings had paroxysmal tachycardia in more than 300 hours of recordings. However, one symptomatic patient with congenital heart block and a prolonged recovery time had brief episodes of paroxysmal ventricular tachycardia that produced no symptoms at the time of recording. The results suggest that the coexistence of prolonged recovery times and paroxysmal tachycardia may be predisposing factors to the development of symptoms in patients with complete heart block. We believe that further electrophysiologic investigation of this possibility is warranted in patients with heart block.

Adolescent↗
PubMed1981

Radionuclide quantitation of right-to-left intracardiac shunts in children.

A simple, noninvasive method for measurement of right-to-left intracardiac shunts would enhance the management of patients with congenital heart disease. This study describes application of data processing techniques used previously in dye-indicator curves to data recorded during the initial transit of radioactive bolus through the central circulation. Radionuclide angiocardiograms were performed in 20 children, mean age 30 months, immediately after cardiac catheterization for congenital heart disease. The radionuclide data recorded over the carotid artery were used to replace arterial sampling required for dye indicators, and forward triangles were fitted to calculate the right-to-left shunt in an approach similar to that of Wood for indicator-dilution curves. Ten of the children had right-to-left shunts by Fick and radionuclide measurement, and 10 of the children with septal defects had no right-to-left shunt by either technique. Both the radionuclide and Fick measurements correlated well (r = 0.95). Therefore, radionuclide angiocardiographic data may be used for accurate calculation of right-to-left shunts in small children, eliminating the need for arterial sampling.

Cardiac Catheterization↗
PubMed1980

Nonivasive detection of retrograde descending aortic flow in infants using continuous wave doppler ultrasonography. Implications for diagnosis of aortic run-off lesions.

Continuous wave Doppler ultrasonography was utilized to detect and characterize descending aortic blood flow velocity patterns in 27 preterm and term infants with or without an aortic run-off lesion proximal to the descending aorta. The effects of coexistent intracardiac defects on the velocity time profiles were evaluated by comparing records from patients with no intracardiac defects or systemic run-off lesions to those with a variety of intracardiac defects but no systemic run-off lesion. No significant alterations were noted. In all patients, the velocity tracing in systole was triangular in shape. During diastole, however, there were qualitative and quantitative differences between patients with and without a proximal run-off lesion. In those without a run-off lesion, retrograde descending aortic flow was present only in early diastole, and aortic flow velocity oscillated around the zero baseline during mid and late diastole. In those with a run-off lesion, retrograde flow present in early diastole continued throughout diastole. Quantitatively, the ratio of the area under the retrograde flow portion of the tracing to the forward flow portion was significantly greater in those with a run-off lesion. The velocity time profiles obtained with CW Doppler were similar to those previously obtained invasively with electromagnetic flow probes of catheter-mounted velocitometers. CW Doppler ultrasonograpy provides a reliable, noninvasive method for describing descending aortic blood flow velocity in infants.

Aorta, Thoracic↗
PubMed1980

Catecholamine induced double tachycardia: case report in a child.

A six-year-old girl with syncope in association with atrial flutter-fibrillation and ventricular tachycardia produced by exercise or emotion is presented. The tachycardias could be reproduced by low-dose isoproterenol infusion and were blocked by high dose propranolol therapy. Catecholamine-induced tachyarrhythmias should be suspected in children with unexplained syncope in association with exercise or emotion.

Atrial Fibrillation↗
PubMed1979

The force-interval relationship of the left ventricle.

We have carried out a quantitative analysis of the force-interval relationship of the human left ventricle and compared it to previous studies done in both intact subjects as well as isolated muscle. The characteristics of the force-interval relationship of the normal patient resembed those of normal isolated mammalian muscle (except when exposed to high levels of catecholamines). The relationship in group 2 (patients with increased left ventricular dimensions and normal pressure indices) resembled those obtained from isolated muscles from hypertrophied hearts. The relationship from group 3 (patients with increased left ventricular EDDs and depressed pressure indices, two of whom were in clinical heart failure) resumbled those induced in normal muscles exposed to high levels of catecholamines, and those obtained from experimentally induced heart failure. The force-interval relationships of the four patients who fell into the third group were strikingly different from the other groups. This suggests that the force-interval relationship may be useful to describe changes in the inotropic state of the patient's heart.

Adolescent↗