Infants at high risk for sudden infant death syndrome??? Have they been identified???--A commentary.
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Equipment Failure↗
Biomedical subjects
E Krongrad
Publications and source records attributed to E Krongrad.
Abnormal septal motion in patients with postoperative right bundle branch block pattern.
Echocardiograms were performed on 25 patients with postoperative right bundle branch block pattern 3 to 93 months after surgery to assess the possible effects of abnormal cardiac excitation on septal motion. Each of the 25 patients demonstrated a unique pattern of septal motion characterized by the presence of an early systolic anterior septal notch, brief in duration and unrelated to subsequent systolic septal motion, right ventricular size, or surgical procedure. Beginning approximately 70 to 80 msec. after the initial QRS deflection, the septum abruptly moved anteriorly 2 to 7 mm. and then returned to a baseline position. The total duration of this abnormal septal motion lasted 78 to 155 msec. This echocardiographic pattern was not seen in any of 30 patients in two control groups. Twenty had a normal QRS pattern and ten demonstrated right ventricular hypertrophy. In addition, patients who underwent open heart surgery and had normal right ventricular conduction postoperatively did not show this echocardiographic pattern with either normal or paradoxical septal motion. This previously undescribed echocardiographic pattern demonstrates that septal motion is uniquely affected in patients with postoperative right bundle branch block pattern.
Adolescent↗
The QT interval in aborted sudden infant death syndrome infants.
The QT interval was measured in 12 normal and 7 aborted sudden infant death syndrome (SIDS) infants in rapid eye movement (REM) and quiet sleep at monthly intervals through the age of 4 months. An accuracy of better than 2 msec was assured by high resolution of the digitized signal and calibration of each QT measurement with an accurately generated time code. In contrast to current speculations, the QT index was significantly smaller in the infants with aborted SIDS than in the normal infants in both REM and quiet sleep (P less than 0.05). In addition, as in normal infants, the QTc was smaller in REM than in quiet sleep (P less than 0.01). Although these results offer no support for the hypothesis that SIDS results from prolongation of the QT interval, they suggest that aborted SIDS infants have a functional abnormality in the autonomic nervous system.
Autonomic Nervous System↗
Effect of sleep state on the QT interval in normal infants.
Twenty QT intervals selected at random from the middle periods of rapid eye movement (REM) and quiet sleep were measured in 12 normal infants studied at 2 weeks and 1, 2, 3, and 4 months of life. A digitizing system, consisting of a precision rotational potentiometer mounted on a pair of calipers and an A/D converter, was used for measurements. An accuracy of +/- 2 msec was achieved by high resolution of the digitized signal and calibration of each QT measurement with an accurately generated time code. Sleep staging was done visually using an electroencephalogram (EEG), an electrooculogram (EOG), a submental electromyogram (EMG), and behavioral criteria. Our results show that the QT index (QTc = QT/square rootRR) was significantly greater during quiet sleep (mean = 0.439) than during REM sleep (mean = 0.433) (P less than 0.01) and that this difference existed at all ages studied.
Electrocardiography↗
Intraoperative mapping in patients with univentricular hearts.
The location of the specialized cardiac conduction system in patients with univentricular hearts may be extremely variable. Electrophysiologic studies during open heart surgery identified the intraventricular conducting tissue to be consistently located in four sites. In patients with univentricular hearts without an outlet chamber, conducting tissue may be located either at 1. along the posterior wall or 2. along the anterior free wall of the ventricle. In patients with univentricular hearts and an outlet chamber, conducting tissue is uusally located anterior and superior to the bulboventricular foramen and then extends towards the atrium either 1. in between the bulboventricular foramen and the pulmonary valve or 2. along the right margin of the pulmonary artery over the anterior free wall of the ventricle towards the junction of the inter-atrial septum and the right atrial appendage. These electrophysiologic studies are consistent with previously described locations of conducting tissue in similar hearts by histologic methods. The different locations of the intraventricular conducting tissues in patients with univentricular hearts demonstrates the valve and the need for electrophysiologic mapping of the specialized cardiac conduction system during surgical repair of univentricular hearts.
Electrocardiography↗
Electrophysiologic-histologic correlation of the cardiac specialized conduction system in two cases of single ventricle and levotransposition of the great arteries.
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Adolescent↗
Prognosis for patients with congenital heart disease and postoperative intraventricular conduction defects.
Intraventricular conduction defects are common following repair of various forms of congenital heart disease. Such defects may affect adversely the long-term prognosis of patients in whom cardiac hemodynamics were adequately restored. Review of previously published studies suggests that the site of the conduction defect may be the reason for the different prognoses reported for patients from different institutions. The so-called "trifascicular block" pattern which sometimes occurs following open heart surgery is probably due to a more extensive lesion to the branching and penetrating parts of the His bundle rather than additional injury to the posterior left bundle branch fibers. Transient complete heart block in the immediate postoperative period seems to be a predictor for late development of complete heart block or sudden death at least as powerful as right bundle branch block and left anterior hemiblock.
Bundle-Branch Block↗
Etiology of right bundle branch block pattern following surgical repair of atrioventricular cushion defects.
Electrocardiograms and surgical data from 12 patients with complete atrioventricular canal defects and 24 patients with ostium primum defects were evaluated before and after open heart surgery in order to document the incidence of postoperative right bundle branch block. The use and precise location of septal sutures utilized for repair were specifically noted in order to assess their possible role in the genesis of the postoperative right bundle branch block pattern. Septal sutures were placed in all patients with atrioventricular canal defects, and ten (83 percent) of these 12 patients developed right bundle branch block. Seven (29 percent) of the 24 patients with ostium primum defects developed a postoperative right bundle branch block, and in all seven patients, septal sutures were utilized. None of the patients with an ostium primum defect without septal sutures developed a right bundle branch block, and none of the patients in this series developed complete heart block.
Adolescent↗
Outflow tract obstruction in tetralogy of Fallot. Intraoperative analysis by echocardiography.
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Adolescent↗
Histologic observations of the cardiac conduction system in a patient with postoperative bilateral bundle branch block.
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Bundle-Branch Block↗
Hemodynamic effects of rapid atrial stimulation in adult and young dogs.
We evaluated the use of rapid atrial stimulation (RAS) to produce 2:1 atrioventricular (AV) block as a method for treating supraventricular tachycardias. We studied the cardiovascular hemodynamic changes before and after block in eight adult dogs and nine young dogs (3-4 1/2 weeks old). In each dog an electrocardiogram; cardiac index; aortic, pulmonary, and left ventricular (LV) systolic and end-diastolic pressures; and LV (dp/dt) p were recorded simultaneously and pulmonary ans systemic resistances were calculated. Measurements were obtained during (1) the control state, (2) RAS with maximal 1:1 AV conduction, (3) RAS with 2:1 AV block, and (4) RAS with 1:1 AV conduction at 50% of the rate which resulted in 2:1 AV block. Comparison of the hemodynamic effect of RAS with maximal 1:1 AV conduction and hemodynamics in the control state showed that there was a significant decrease in cardiac index and aortic mean pressure of 39% and 15%, respectively. When hemodynamic changes during RAS with 2:1 AV block were compared with those during RAS with maximal 1:1 AV conduction, cardiac index, LV systolic pressure, and aortic mean pressure increased by 52%, 17%, and 22%, respectively. LV (dp/dt) p increased by 20% and was significantly higher during RAS with 2:1 AV block than at higher ventricular rates obtained with RAS and maximal 1:1 AV conduction. We found that in this acute study the hemodynamic findings for the young dogs were similar to those for adult dogs. The data suggest that (1) significant hemodynamic improvement is obtained by RAS causing 2:1 AV block when compared to higher ventricular rates associated with 1:1 AV conduction; (2) in addition to increasing the diastolic filling period, reducing the very high ventricular rates improves the cardiac contractile state, and (3) RAS and 2:1 AV block may provide a useful technique for the management of some patients with intractable supraventricular tachycardia.
Animals↗
Signal enhancement for detection of specialized atrioventricular conduction system electrograms during open-heart surgery.
A method for signal enhancement of electrograms of the specialized atrioventricular conduction system is presented. This method allows a single electrogram to replace the tracings of bipolar electrograms previously required to ensure recognition of the specialezed conduction system and yet maintains the safety afforded by use of three pairs of recording electrodes. In addition, this new signal is enhanced in magnitude and is always unidirectional (positive). These features are desirable for automated signal recognition. This method therefore provides an important step toward future automation and signal recognition of specialized conduction system electrograms during open-heart surgery.
Animals↗
Transient bacteremia in pediatric patients after dental extraction.
The incidence of bacteremia in a group of well children undergoing dental extraction of both normal and abscessed teeth was determined. Blood samples were obtained from each child before and immediately after dental instrumentation and then cultured aerobically and anaerobically. Eleven of 36 (30%) of the postextraction cultures were positive, and Streptococcus viridans grew from all of them. Bacteremia was more common after the extraction of diseased teeth, and there was no relationship between bacteremia and the number or species of teeth removed.
Adolescent↗
Ventricular paired pacing to control rapid ventricular heart rate following open heart surgery. Observations on ectopic automaticity. Report of a case in a four-month-old patient.
An unusual case is presented in which an atrioventricular (A-V) junctional tachycardia at a rate of 285 beats/min developed in the immediate postoperative period following surgical repair (a Mustard procedure) of transposition of the great vessels in a four-month-old infant. With that heart rate the systolic blood pressure bacame 35-40 mm Hg and urinary output ceased. Ventricular paired pacing was employed successfully to halve the mechanically effective ventricular rate. This resulted in a clinically effective blood pressure and return of normal urinary output. The clinical course of the A-V junctional tachycardia, plus its response to several interventions, suggested that the mechanism of the A-V junctional tachycardia was automatic rather than re-entrant. The study demonstrates that ventricular paired pacing for the control of cardiac arrhythmias is a useful clinical technique in selected cases.
Atrioventricular Node↗
Intraoperative recording of the His bundle electrogram in man. An assessment of its precision.
To estimate the effect of distance between the electrode and the signal source on the amplitude of the His bundle electrogram (HBE) recorded during open heart surgery, a specially designed probe, containing six pairs of closely spaced (1 mm) electrodes was placed on the endocardial surface of the right atrium such that each electrode pair was parallel to the course of the His bundle. The amplitude of the HBE recorded through electrodes closest to the His bundle ranged from 0.76 to 2.44 mV, at 1mm from 0.38 to 1.13 mV, at 2mm from 0.27 to 0.86 mV, and at 3 mm from 0.2 to 0.44 mV. Maximal amplitude of HBE decreased by 57% at 1mm, 73% at 2 mm, and 82% at 3mm. The percent decrease was initially rapid, then declined more slowly at distances greater than 1 mm, resembling in form data obtained previously in animal studies by different techniques. Since the maximum HBE was greater than 1.0 mV in nine of 11 patients, and equal to or greater than 1.0 mV in only two of 11 patients at 1 mm, and less than 1.0 mV in all patients 2.0 mm from the maximal HBE, the anatomic location of the His bundle can be estimated from HBE amplitude. Intracardiac electrograms, recorded through closely spaced bipolar electrodes during open heart surgery, afford clinically useful precision in locating the specialized conduction tissue of the heart.
Adolescent↗
Subpulmonary obstruction in congenitally corrected transposition of the great arteries due to ventricular membranous septal aneurysms.
The clinical, hemodynamic, and angiographic observations, as well as the surgical approach used for repair in three patients with congenitally corrected transposition of the great arteries and ventricular membranous septal aneurysms, are presented. In two of the three patients the membranous septal aneurysm caused subpulmonary obstruction, with 94 and 125 mm Hg systolic gradients. In each patient the aneurysm was demonstrated by angiocardiography, which also showed differences in size and shape with cardiac systole and diastole. Review of the previously described reports indicates that patients with congenitally corrected transposition often display various forms of pulmonary outflow obstruction and when a ventricular membranous septal aneurysm exists, a significant subpulmonary obstruction is present in most patients. The unique anatomic relationship between the pulmonary artery and a ventricular membranous septal aneurysm in patients with transposition of the great arteries with and without atrioventricular discordance explains why subpulmonary obstruction sometimes develops.
Adolescent↗
Left anterior and left posterior hemiblock in tricuspid atresia and transposition of the great vessels: observations and electrocardiographic nomenclature and electrophysiologic mechanisms.
A patient with tricuspid atresia and characteristic electrocardiographic features of counterclockwise and superiorly oriented frontal plane QRS loop (left anterior hemiblock) is presented. Operative intervention resulted in a clockwise and inferior rotation of the frontal QRS loop (left posterior hemiblock) without the development of complete left bundle branch block. This observation suggests that the electrocardiographic pattern of left anterior hemiblock may result from other mechanisms in addition to block of the left bundle branch fibers oriented toward the anterior part of the left ventricle. The case further suggests that electrocardiographic patterns of apparent A-V conduction defects may not be at all associated with true block in the A-V conduction system. Further, it emphasizes the fact that various electrophysiologic mechanisms may account for identical electrocardiographic patterns.
Child↗