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Biomedical subjects

D W Benson

Publications and source records attributed to D W Benson.

At least 73 records · Page 4Linked to original sources
PubMed1989

Bundle branch block during orthodromic reciprocating tachycardia onset in infants.

Transesophageal electrophysiologic studies were performed in 58 infants (age less than or equal to 1 year, median 10 days) with electrocardiographically documented orthodromic reciprocating tachycardia (ORT). The aim was to evaluate the occurrence, type and electrophysiologic effects of bundle branch block (BBB) during ORT onset. Of the 58 infants, 25 (43%) had BBB with pacing-induced tachycardia onset. BBB was initiated by single or double premature atrial extrastimuli and by burst atrial pacing; 4 infants also demonstrated BBB with spontaneous ORT onset during transesophageal study. Two of 25 infants had BBB only after intravenous procainamide. Comparison of the 25 infants exhibiting BBB at ORT onset with the 33 infants not demonstrating BBB revealed that age was not statistically different in the 2 groups, but that severity of illness (based on a 1 to 3 scale) was greater (p less than 0.05) and normal QRS ORT cycle length was shorter (p less than 0.02) in the infants with BBB. Of the 25 infants with BBB at ORT onset, 17 had left BBB, 3 had right BBB and 5 had both left and right BBB. Ventriculoatrial interval or cycle length increases during ORT with BBB in 16 of 25 (64%) infants suggested left free wall-accessory atrioventricular connections.(ABSTRACT TRUNCATED AT 250 WORDS)

Bundle-Branch Block↗
PubMed1989

Direct tricuspid closure versus atrial partitioning in Fontan operation for complex lesions.

Thirty-three patients with complex lesions undergoing the Fontan operation needed either direct tricuspid closure (group 1, 14 patients) or atrial partitioning (group 2, 19 patients). In group 1, the tricuspid patch was sutured to the annulus leaving the coronary sinus draining to the systemic venous atrium. In group 2, atrial partitioning was accomplished with either a Dacron or a polytetrafluoroethylene patch, leaving the coronary sinus draining to the pulmonary venous atrium. Intraoperative distention of the left side was used to check for residual defects. In group 1, complete heart block developed in 5 patients (36%) and patch disruption, in 4 patients (29%). There were 3 late deaths (21%), which were due to sudden death, sepsis caused by Candida, and liver failure. In group 2, no patient had heart block, and patch disruption developed in 1 patient (5%). There was 1 early death (5%) and 2 late deaths (11%), which were due to sepsis caused by Candida and renal failure. Our experience suggests that atrial partitioning is a better approach than direct tricuspid patch closure in patients with complex lesions undergoing the Fontan operation.

Adolescent↗
PubMed1989

Transposition of the great arteries: a comparison of results of the mustard procedure versus the arterial switch.

Sixty infants with transposition of the great arteries and intact ventricular septum underwent primary surgical correction in the first 3 months of life. Twenty-three patients had a Mustard procedure (group 1) and 37 patients, an arterial switch operation (group 2). The mean age at the time of repair was 42 +/- 31 days for group 1 and 8 +/- 6 days for group 2 (p less than 0.001). The mean weight at the time of repair was 3.6 +/- 0.7 kg for group 1 and 3.4 +/- 0.5 kg for group 2 (p = not significant). Operative mortality was 8.7% (2/23) in group 1 and 8.1% (3/37) in group 2 (p = not significant). The incidence of arrhythmias in the early postoperative period was 39% (9/23) in group 1 and 11% (4/37) in group 2 (p less than 0.01). All patients were followed a mean of 4.8 +/- 2.4 years in group 1 and 2.6 +/- 1.4 years in group 2 (p less than 0.001). Postoperative catheterization has been performed in 86% (18/21) of group 1 operative survivors and 50% (17/34) of group 2 operative survivors. Ejection fraction of the systemic ventricle was 79% +/- 15% of predicted normal in group 1 and 98% +/- 6% in group 2 (p less than 0.005). The incidence of late arrhythmias was 57% (12/21) in group 1 and 3% (1/34) in group 2 (p less than 0.001). There have been 2 late deaths in group 1 and 1 late death in group 2 (p = not significant).(ABSTRACT TRUNCATED AT 250 WORDS)

Arrhythmias, Cardiac↗
PubMed1989

Total and myofibrillar protein breakdown in different types of rat skeletal muscle: effects of sepsis and regulation by insulin.

Proteolysis is increased in sepsis, but it is not known whether myofibrillar and non-myofibrillar proteins are broken down in the same fashion, or respond to the same regulatory forces as in non-septic muscle. In this study, therefore, the effect of sepsis on total and myofibrillar protein breakdown in incubated rat extensor digitorum longus (EDL) and soleus (SOL) muscles was determined, and the response in vitro to different concentrations of insulin (10 to 10(5) microU/mL) of protein degradation was studied in incubated EDL muscles from control and septic rats. Sepsis was induced in rats weighing 40 to 60 g by cecal ligation and puncture (CLP). Control animals were sham operated. Sixteen hours after CLP or sham operation, intact EDL and SOL muscles were incubated for two hours in oxygenated Krebs-Henseleit bicarbonate buffer containing glucose (10 mmol/L) and cycloheximide (0.5 mmol/L), and total and myofibrillar protein breakdown was assessed from release into incubation medium of tyrosine and 3-methylhistidine (3-MH), respectively. Tyrosine and 3-MH were determined fluorometrically by high performance liquid chromatography (HPLC). Tissue levels of tyrosine and 3-MH remained stable both in control and septic muscles during incubation for two hours. The rate of tyrosine release was increased during sepsis by 58% (P less than .001) and 15% (NS) in EDL and SOL muscle, respectively. The corresponding figures for 3-MH were 103% (P less than .001) and 21% (NS). Tyrosine release was reduced by insulin at a concentration of 10(3) microU/mL in control muscle and at a concentration of 10(4) microU/mL in septic muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Accelerated idioventricular rhythm complicating atrioventricular junction ablation for automatic atrial tachycardia.

A 13-year-old male with histologic evidence of cardiomyopathy, drug-refractory primary atrial tachycardias, and deteriorating left ventricular function underwent transcatheter His bundle ablation to control ventricular rate. Following an initial successful ablation at the level of the atrioventricular node, the patient exhibited an accelerated escape rhythm of apparent junctional origin (ventricular cycle length = 470 msec, HV = 100 msec) with complete heart block. A second ablation procedure was undertaken, following which an accelerated idioventricular rhythm (cycle length = 500 msec) became apparent and has persisted (follow-up 15 months). Thus, findings in this patient suggest that attempts to control refractory rapid ventricular responses in cardiomyopathy patients with primary atrial tachycardias may be complicated by the potential for junctional and idioventricular sites to exhibit similar abnormally accelerated subsidiary pacemaker function.

Adolescent↗
PubMed1989

Relation between preoperative left ventricular muscle mass and outcome of the Fontan procedure in patients with tricuspid atresia.

The relation between preoperative left ventricular muscle mass and clinical outcome of the Fontan procedure was evaluated retrospectively in 22 patients with tricuspid atresia who were selected for this physiologic surgical correction by conventional hemodynamic criteria. Patients were divided into two groups: group A (excellent or good outcome) and group B (poor outcome or death) based on the clinical course assessed up to 9.5 years postoperatively. Thirteen of 22 group A patients did not have prolonged, clinically significant, systemic venous hypertension and were not on long-term diuretic drug therapy. Nine of 22 group B patients either had clinically significant systemic venous hypertension, required long-term diuretic drug therapy or died (3 patients). Age at surgery, pulmonary arteriolar resistance, left ventricular ejection fraction, end-diastolic volume, end-diastolic pressure, systemic oxygen saturation and pulmonary to systemic blood flow ratio (Qp/Qs) were not statistically different between the two groups. Left ventricular muscle mass, both in group A patients (92 +/- 31 g/m2) and in group B patients (146 +/- 61 g/m2), was greater than the normal mean value (p less than 0.01 and p less than 0.001, respectively). Left ventricular muscle mass in group B was significantly greater than in group A (p less than 0.01). Furthermore, left ventricular muscle mass/end-diastolic volume (mass/volume) ratio, reflecting the extent of left ventricular hypertrophy relative to volume overload, was significantly greater in group B (1.1 +/- 0.28) than in group A (0.84 +/- 0.21) (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Exercise response before and after termination of atrial tachycardia after congenital heart disease surgery.

We studied exercise performance before and after conversion of atrial tachycardia to sinus rhythm, atrial bradycardia, or junctional rhythm in 10 patients 9-25 years of age 8-20 years after congenital heart disease surgery (complete transposition of the great arteries, seven of 10 patients). The same maximal cycle (five of 10 patients) or treadmill (five of 10 patients) exercise protocol was performed in atrial tachycardia and sinus rhythm 1-232 days after atrial tachycardia (mean, 34 days). Electrocardiogram, heart rate, and pulmonary gas exchange were recorded. Sinus rhythm exercise increased peak VO2 (mean, 28.7 [sinus rhythm] vs. 24.7 [atrial tachycardia], p less than 0.01), exercise time (p less than 0.01), and O2 pulse at rest (p less than 0.01) and at peak exercise (NS). Mean resting heart rate decreased from 109 to 70 beats/min (p less than 0.01). In atrial tachycardia, peak exercise heart rate was low (80-163 beats/min) because of fixed conduction (six of 10 patients) or high as conduction approached 1:1 (176-252 beats/min) (four of 10 patients). In sinus rhythm, rest to peak exercise heart rate increased in six of 10 patients (p less than 0.05). The data show improved exercise performance in sinus rhythm primarily because of improved heart rate adaptation to exercise, by either permitting increased heart rate response or eliminating excessively high heart rate with inadequate diastolic filling.

Exercise↗
PubMed1989

Effect of heart rate increase on dorsal aortic flow before and after volume loading in the stage 24 chick embryo.

In the stage 24 chick embryo, a paced increase in heart rate reduces stroke volume, presumably by rate-dependent decrease in passive filling. We hypothesized that rate-dependent stroke volume reduction could be abolished by volume loading. Dorsal aortic blood velocity was measured with a 20 mHz pulsed-Doppler meter from a 0.75-mm piezoelectric crystal (eight embryos), and atri-oventricular velocity was simultaneously measured from the ventricular apex (six embryos). Sinus venosus pacing (stimuli of 1 ms duration and less than 4 mA) was performed at intrinsic rate (P:I) and at 150% of intrinsic rate (P:150%I). Volume loading was performed during P:150%I by intravenous injection of 7.5 microL of chick Ringer's solution. Using atrioventricular velocity profile, stroke volume was divided into the proportion due to passive (E-phase) and active (A-phase) filling. Stroke volume was compared during P:I, P:150%I, immediately (P:150%I') and 30 s after (P:150%I") volume loading. Data (mean +/- SEM) were compared by ANOVA. During pacing, stroke volume (mm2/cycle) decreased but increased after volume loading (I, 0.43 +/- 0.03; P:I, 0.37 +/- 0.03; P:150%I, 0.19 +/- 0.03; P:150%I', 0.24 +/- 0.05; P:150%I", 0.28 +/- 0.04 (p less than 0.005). During P:150%I, E-phase filing disappeared and was not restored by volume loading, whereas, A-phase filling diminished but was restored by volume loading. In stage 24 chick embryos, rate-dependent stroke volume decrease is reversed by volume loading that restores stroke volume due to an increase in active filling but not passive filling. Thus, even at rapid heart rate, the embryonic ventricle responds to volume loading, indicating that the Frank-Starling relationship functions during tachycardia in the embryonic heart.

Animals↗
PubMed1989

Effect of sepsis on calcium uptake and content in skeletal muscle and regulation in vitro by calcium of total and myofibrillar protein breakdown in control and septic muscle: results from a preliminary study.

Because high calcium concentration in vitro stimulates muscle proteolysis, calcium has been implicated in the pathogenesis of increased muscle breakdown in different catabolic conditions. Protein breakdown in skeletal muscle is increased during sepsis, but the effect of sepsis on muscle calcium uptake and content is not known. In this study the influence of sepsis, induced in rats by cecal ligation and puncture, on muscle calcium uptake and content was studied. Sixteen hours after cecal ligation and puncture or sham operation, calcium content of the extensor digitorum longus (EDL) and soleus (SOL) muscles was determined with an atomic absorption spectrometer. Calcium uptake was measured in intact SOL muscles incubated in the presence of calcium 45 (45Ca) for between 1 and 120 minutes. Total and myofibrillar protein breakdown was determined in SOL muscles, incubated in the presence of different calcium concentrations (0; 2.5; 5.0 mmol/L), and measured as release into the incubation medium of tyrosine and 3-methylhistidine (3-MH), respectively. Calcium content was increased by 51% (p less than 0.001) during sepsis in SOL and by 10% (p less than 0.05) in EDL muscle. There was no difference in 45Ca uptake between control and septic muscles during the early phase (1 to 5 minutes) of incubation. During more extended incubation (30 to 120 minutes), muscles from septic rats took up significantly more 45Ca than control muscles (p less than 0.05). Tyrosine release by incubated SOL muscles from control and septic rats was increased when calcium was added to the incubation medium, and at a calcium concentration of 2.5 mmol/L, the increase in tyrosine release was greater in septic than in control muscle. Addition of calcium to the incubation medium did not affect 3-MH release in control or septic muscle. The results suggest that calcium uptake and content in skeletal muscle are increased during sepsis and that high calcium concentrations in vitro stimulate nonmyofibrillar protein breakdown. Muscles from septic animals may be more sensitive to the effect of calcium in vitro than muscles from nonseptic rats. Whether increased calcium uptake and content in skeletal muscle is partly responsible for accelerated muscle proteolysis during sepsis remains to be determined.

Animals↗
PubMed1988

Role of transesophageal pacing in evaluation of palpitations in children and adolescents.

Transesophageal atrial pacing was used to evaluate the cause of palpitations in 28 patients ages 3 to 18 years (mean 11). Palpitations were defined as the sustained (seconds to minutes) sensation of rapid heart beating. Each patient had had greater than 2 episodes of palpitations. No patient had other evidence of heart disease. Standard electrocardiogram was normal (23 of 28 patients), demonstrated ventricular preexcitation (3 of 28 patients) or demonstrated short PR interval (2 of 28 patients). In selected patients, ambulatory monitoring (11 patients) or exercise testing (3 patients) was performed but failed to demonstrate a cause of palpitations. In an effort to initiate tachycardia, a similar transesophageal atrial pacing protocol was performed in each patient. The protocol consisted of: (1) single extrastimuli at progressively closer intervals during sinus rhythm and after an 8-beat pacing train at greater than or equal to 1 cycle lengths and (2) incremental atrial pacing to the point of second-degree atrioventricular block. If this pacing regimen failed to initiate tachycardia, it was repeated during isoproterenol infusion (0.02, 0.05 and 0.1 micrograms/kg/min) and then following intravenous atropine (0.04 mg/kg) administration. During the study, tachycardia was initiated in 20 of 28 patients (71%) (14 of 15 patients greater than 10 years, 6 of 13 patients less than or equal to 10 years; p less than 0.01, Fisher's exact test). Electrophysiologic characteristics of induced tachycardia suggested reentry within the atrioventricular node (8 of 20 patients) or orthodromic reciprocating tachycardia (12 of 20 patients). In 3 of 12 patients with orthodromic reciprocating tachycardia, a transition to atrial fibrillation was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

Clinical and electrophysiologic features of fetal and neonatal paroxysmal atrial tachycardia resulting in congestive heart failure.

Those clinical and electrophysiologic features of paroxysmal atrial tachycardia (PAT) that appeared to be the cause of prenatal congestive heart failure (CHF) (hydrops fetalis) were evaluated in 12 neonates, ages 1 to 14 days, and compared with those occurring in 12 neonates, ages 2 to 34 days, who developed CHF from PAT diagnosed postnatally. Transesophageal electrophysiologic evaluation was performed after birth or at the time of PAT occurrence in the prenatal CHF group and at the time of CHF diagnosis in the postnatal CHF group. Before the electrophysiologic study, spontaneous PAT onset and termination were observed in all prenatal CHF neonates. In the postnatal CHF neonates, however, a single, prolonged episode of PAT was observed. During PAT, all neonates were observed to have a regular heart rate, normal QRS morphology and ventriculoatrial interval exceeding 80 ms. These findings suggested an orthodromic reciprocating tachycardia using an accessory atrioventricular connection as the tachycardia mechanism. In the 12 neonates with prenatal CHF, the PAT cycle length measured 243 +/- 30 ms, whereas in the 12 neonates with postnatal CHF it measured 208 +/- 19 ms (p less than 0.003). Neonates with prenatal CHF secondary to PAT appear to develop CHF from multiple PATs recurring at relatively long cycle lengths (slow heart rates), whereas postnatal CHF neonates develop heart failure symptoms during a sustained tachycardia episode with relatively short cycle lengths (fast heart rates).

Edema↗
PubMed1988

Surgical management of patients with interrupted aortic arch and severe subaortic stenosis.

Ten patients underwent palliative surgery for interrupted aortic arch and severe subaortic obstruction due to posterior displacement of the conal septum. Their ages ranged between 4 and 28 days (mean, 11.0 +/- 7.7 days) and their weights, between 2.1 and 4.2 kg (mean, 2.85 +/- 0.6 kg). Preoperative echocardiography and cardiac catheterization were performed on all patients. The ratios of the left ventricular outflow tract diameters and the ascending aortic diameters to the descending aortic diameters were 0.56 +/- 0.03 and 0.56 +/- 0.06, respectively, compared with 0.81 +/- 0.12 and 0.95 +/- 0.17, respectively, in 20 patients with interrupted aortic arch but without obstruction (p less than 0.001). Four of the 10 patients underwent pulmonary artery banding and insertion of a bypass graft between the ascending and the descending aorta. All 4 died of low cardiac output soon after operation (100% operative mortality). The remaining 6 patients underwent banding and insertion of a graft between the main pulmonary artery proximal to the band, and the descending aorta. All of these patients survived, and all except 1 are doing well 3 months to 4 years postoperatively. The use of a pulmonary artery-descending aorta conduit and of distal pulmonary artery banding provides good palliation for patients with interrupted aortic arch and major subaortic stenosis.

Aorta, Thoracic↗
PubMed1988

Comparison of single versus multidose blood cardioplegia in arterial switch procedures.

Fifty-three patients with transposition of the great arteries and Taussig-Bing anomaly undergoing an arterial switch procedure were divided into two groups. Group 1 (N = 32) received multidose cardioplegia injected initially into the aortic root and subsequently into the coronary artery orifices and Group 2 (N = 21), single-dose cardioplegia injected into the aortic root. The mean aortic cross-clamp and bypass times were generally longer in Group 1 compared with Group 2. Group 1 patients with simple transposition undergoing primary repair (N = 15) had an aortic cross-clamp time of 80 +/- 8 minutes and a bypass time of 203 +/- 27 minutes versus 64 +/- 6 minutes (p less than 0.001) and 170 +/- 15 minutes (p less than 0.01), respectively, for similar patients in Group 2 (N = 10). Group 1 patients with simple transposition undergoing staged repair (N = 7) had an aortic cross-clamp time of 71 +/- 6 minutes and a bypass time of 201 +/- 24 minutes versus 66 +/- 4 minutes (p = not significant [NS]) and 226 +/- 25 minutes (p = NS), respectively, for Group 2 (N = 6). In Group 1 patients with complex transposition (N = 10), the aortic bypass time was 79 +/- 12 minutes and the bypass time was 261 +/- 40 minutes versus 64 +/- 11 minutes (p less than 0.05) and 225 +/- 16 minutes (p less than 0.1), respectively, for Group 2 (N = 5). Early mortality was 16% (5/32) in Group 1; there were no early deaths in Group 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Aorta↗
PubMed1988

Transesophageal pacing and electrocardiography in the neonate: diagnostic and therapeutic uses.

Transesophageal pacing and electrocardiography have important diagnostic and therapeutic uses in the neonate. Electrode placement is simple, and transesophageal ECG recording may be accomplished using available ECG recorders. Transesophageal pacing requires a special stimulator to administer stimulus pulses of 10 msec duration. Transesophageal ECG aids in establishing specific electrophysiologic Transesophageal ECG aids in establishing specific electrophysiologic diagnosis in neonates with rhythm disturbances. Transesophageal pacing is useful for treatment of atrial bradycardia as well as for cardioversion of a variety of tachycardias. There have been no serious long-term complications reported from use of transesophageal pacing and electrocardiography.

Cardiac Pacing, Artificial↗
PubMed1987

Success of re-use of cardiac electrode catheters.

The feasibility of cardiac electrode catheter re-use was prospectively evaluated over a 5-year period (1981 to 1986), during which time 178 catheters were used 1,526 times for 847 electrophysiologic procedures. Detailed records of catheter testing and use were maintained. No complications were encountered during the study period. All re-used catheters functioned for cardiac pacing and electrographic recording. Surveillance cultures and biologic indicators revealed that adequate sterilization procedures were used. Thus, electrode catheters may be safely re-used provided a thorough cleaning, testing and record-keeping system is instituted. This may result in lower patient cost (approximately $30 per re-use vs [200 per single use) for electrophysiologic catheterization.

Cardiac Catheterization↗
PubMed1987

Role of extrastimulus site and tachycardia cycle length in inducibility of atrial preexcitation by premature ventricular stimulation during reciprocating tachycardia.

Preexcitation of the atria during reciprocating tachycardia (RT) by a premature ventricular complex occurring when the His bundle is refractory provides direct evidence of the presence of accessory atrioventricular (AV) connection. The impact of ventricular stimulation site and RT cycle length on inducibility of atrial preexcitation was assessed in 38 patients with RT utilizing a single accessory AV connection (right free wall in 5 patients, left free wall in 21 and posterior septal/paraseptal in 12). Extrastimuli were inserted at right ventricular (RV) apical, left ventricular (LV) septal and LV free wall sites. Inducibility of and magnitude of atrial preexcitation increased as stimulation site approached accessory AV connection site. Thus, for RV free wall connections, RV extrastimuli preexcited the atria in 5 of 5 patients, LV septal in 1 of 5 and LV free wall in 0 of 4. For LV free wall accessory connections, RV extrastimuli preexcited the atria in only 3 of 21 patients, compared with 12 of 17 with LV septal and 20 of 21 with LV free wall stimulation. Additionally, the magnitude of atrial preexcitation achieved was related to RT cycle length, diminishing as cycle length shortened. Finally, in a few instances both RV apical and LV free wall extrastimuli failed to elicit preexcitation in patients with a posterior septal connection. Thus, ventricular pacing site and RT cycle length contribute importantly to induction of atrial preexcitation by ventricular extrastimulation technique and should be considered during evaluation of patients with RT in whom accessory AV connections may be present.

Adolescent↗