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Biomedical subjects

G D Webb

Publications and source records attributed to G D Webb.

At least 19 recordsLinked to original sources
PubMed1999

Atrial arrhythmia after surgical closure of atrial septal defects in adults.

BACKGROUND: Atrial flutter and atrial fibrillation are causes of morbidity in adults with an atrial septal defect. In this study, we attempted to identify risk factors for atrial flutter and fibrillation both before and after the surgical closure of an atrial septal defect. METHODS: We searched for preoperative and postoperative atrial flutter or fibrillation in 213 adult patients (82 men and 131 women) who underwent surgical closure of atrial septal defects because of symptoms, a substantial left-to-right shunt (ratio of pulmonary to systemic blood flow, >1.5:1), or both at Toronto Hospital between 1986 and 1997. RESULTS: Forty patients (19 percent) had sustained atrial flutter or fibrillation before surgery. As compared with the patients who did not have atrial flutter or fibrillation before surgery, those who did were older (59+/-11 vs. 37+/-13 years, P<0.001) and had higher mean pulmonary arterial pressures (25.0+/-9.7 vs. 19.7+/-8.2 mm Hg, P=0.001). There were no perioperative deaths. After a mean follow-up period of 3.8+/-2.5 years, 24 of the 40 patients (60 percent) continued to have atrial flutter or fibrillation. The mean age of these patients was greater than that of the 16 who converted to sinus rhythm (P=0.02). New-onset atrial flutter or atrial fibrillation was more likely to have developed at follow-up in patients who were older than 40 years at the time of surgery than in those who were 40 or younger (5 of 67 vs. 0 of 106, P=0.008). Late events (those occurring more than one month after surgery) included stroke in six patients (all but one with atrial flutter or fibrillation, one of whom died) and death from noncardiac causes in two patients. Multivariate analysis showed that older age (>40 years) at the time of surgery (P=0.001), the presence of preoperative atrial flutter or fibrillation (P<0.001), and the presence of postoperative atrial flutter or fibrillation or junctional rhythm (P=0.02) were predictive of late postoperative atrial flutter or fibrillation. CONCLUSIONS: The risk of atrial flutter or atrial fibrillation in adults with atrial septal defects is related to the age at the time of surgical repair and the pulmonary arterial pressure. To reduce the morbidity associated with atrial flutter and fibrillation, the timely closure of atrial septal defects is warranted.

Adolescent↗
PubMed1999

Cardiac tamponade and death from intrapericardial rupture [corrected] of sinus of Valsalva aneurysm.

A 35-year-old woman presented with dyspnea and chest pain. She had a large aneurysm of the non-coronary sinus of Valsalva. Before her scheduled urgent surgery, the patient collapsed and died of cardiac tamponade secondary to intrapericardial rupture of the aneurysm. We would advocate urgent repair of this type of lesion to prevent such an outcome. We are aware of no other specific reports addressing extracardiac rupture of non-coronary cusp aneurysms [corrected].

Adult↗
PubMed1998

Total cavopulmonary anastomosis (Fontan) in children with Down's syndrome.

BACKGROUND: There is a paucity of information to guide the management of the child with Down's syndrome and congenital heart disease in whom biventricular repair is precluded. METHODS: Through the cardiology and cardiovascular surgery databases of The Hospital for Sick Children and Toronto Congenital Cardiac Centre for Adults, we identified patients with trisomy 21 and ventricular hypoplasia who had undergone a Fontan procedure (or modification). RESULTS: Of 533 patients who had undergone a Fontan operation between 1976 and 1997, 4 had trisomy 21. All 4 patients had unbalanced complete atrioventricular septal defect with right ventricular hypoplasia in 3 and left ventricular hypoplasia in 1. Three patients survived, and 1 died of endocarditis. The 3 survivors have done well in the short term and medium term without complications related to the pulmonary vasculature. CONCLUSIONS: We suggest that in appropriately selected patients with trisomy 21 and ventricular hypoplasia who are unsuitable for two or one and a half ventricle repair, the Fontan procedure is not contraindicated and provides short-term and medium-term benefit.

Down Syndrome↗
PubMed1997

Sustained ventricular tachycardia in adult patients late after repair of tetralogy of Fallot.

OBJECTIVES: We sought to determine the features associated with sustained monoform ventricular tachycardia (VT) in adult patients late after repair of tetralogy of Fallot (TOF) and to review their management. BACKGROUND: Patients with repair of TOF are at risk for sudden death. Risk factors for ventricular arrhythmia have been identified from patients with ventricular ectopic beats because of the low prevalence of sustained VT. METHODS: From a retrospective chart review of patients assessed between January 1990 and December 1994, 18 adult patients with VT were identified and compared with 192 with repaired TOF free of sustained arrhythmia. RESULTS: There was no significant difference in age at repair, age at follow-up or operative history. Patients with VT had frequent ventricular ectopic beats (6 of 9 vs. 21 of 101), low cardiac index ([mean +/- SD] 2.4 +/- 0.4 vs. 3.0 +/- 0.8) and more structural abnormalities of the right ventricle (outflow tract aneurysms and pulmonary or tricuspid regurgitation) than control patients. Electrophysiologic map-guided operation was performed in 10 of 14 patients who required reoperation. VT has reoccurred in three of these patients. Four patients did not undergo operation (three received amiodarone; one underwent defibrillator implantation). Two patients with VT also had severe heart failure and died. CONCLUSIONS: Most patients with VT late after repair of TOF have outflow tract aneurysms or pulmonary regurgitation, or both. These patients have a greater frequency of ventricular ectopic beats than arrhythmia-free patients after repair of TOF. A combined approach of correcting significant structural abnormalities (pulmonary valve replacement or right ventricular aneurysmectomy, or both) with intraoperative electrophysiologic-guided ablation may reduce the potential risk of deterioration in ventricular function and enable arrhythmia management to be optimized.

Adult↗
PubMed1997

Pulmonary valve replacement late after repair of tetralogy of Fallot.

BACKGROUND: Pulmonary valve incompetence is usually well tolerated after tetralogy of Fallot repair but may result in late progressive right heart failure as manifested by increasing fatigue, dyspnea, and frequently arrhythmias. METHODS: All patients who underwent pulmonary valve replacement in our center late after repair of tetralogy of Fallot were reviewed. RESULTS: Eighty-five patients had elective pulmonary valve replacement late (median, 9.3 years) after repair. Operative risk was low (1.1%). Ninety percent of survivors are in New York Heart Association class I. Survival 10 years after pulmonary valve replacement is 95%, with 86% of the patients free of reoperation for valve failure. CONCLUSIONS: Pulmonary valve replacement is infrequently required after repair of tetralogy of Fallot. Pulmonary valve replacement may be performed electively with little risk; it improves symptoms of right heart failure and provides satisfactory long-term survival with low risk of early valve failure. As the population of patients who have had repair of tetralogy of Fallot ages, pulmonary valve replacement will become a more frequent consideration.

Adolescent↗
PubMed1997

Caretakers' knowledge and preparation abilities of salt-sugar solution in north-eastern Nigeria.

Awareness and knowledge of oral rehydration therapy (ORT) and preparation abilities of salt-sugar solution (SSS) were investigated by means of focus group discussions and complemented by a structured questionnaire survey of mothers in rural and urban areas of north-eastern Nigeria. ORT awareness was high with some intra-regional variations. Perception of ORT function was, however, grossly unrealistic, with a third to four-fifth of mothers expecting ORT to stop diarrhoea. At least one quarter of mothers lacked adequate SSS preparation abilities and the materials and ingredients required for its preparation. Re-evaluation of the content and method of imparting health education messages in ORT promotion is recommended. Such messages should emphasise the function of ORT. It is also recommended that standardised cups for water, salt and sugar measurements be provided to households as a ready means of ensuring the correct preparation of SSS in the home-based management of diarrhoea.

Adult↗
PubMed1996

Congenitally corrected transposition of the great arteries in the adult: functional status and complications.

OBJECTIVES: We sought to assess the clinical outcome, functional status and complications of adult patients with congenitally corrected transposition of the great arteries. BACKGROUND: Congenitally corrected transposition is a rare form of congenital heart disease, although survival into adult life may be expected. Little information is available on the long-term prognosis of these patients once they have reached adulthood. This study focuses exclusively on patients >18 years old followed up at a single tertiary referral center. METHODS: The charts of all patients with a diagnosis of congenitally corrected transposition of the great arteries from the Toronto Congenital Cardiac Centre for Adults since 1985 were reviewed. Data were available for 52 patients, 26 of whom had undergone radionuclide angiography. Mortality, clinical and functional status, surgical procedures and complications were reviewed. RESULTS: Thirteen patients (25%) died; age at death was 38.5 +/- 12.5 years (mean +/- SD). The current age of survivors is 32.7 years (range 18.2 to 54.3). Of the survivors, 17 had palliative procedures, and 25 had definitive repair, 11 of whom required reoperation. Left ventricle to pulmonary artery conduit replacement was necessary in seven patients. Eighteen patients have permanent pacemakers, nine of whom developed complete heart block perioperatively. Nine patients developed progressive atrioventricular (AV) block unrelated to operation. Supraventricular arrhythmias occurred in 15 patients. Progressive systemic AV valve regurgitation developed in 10 patients and endocarditis in 6. CONCLUSIONS: Congenitally corrected transposition in the adult patient is not a benign condition. Late complications are common and warrant careful, long-term follow-up.

Adult↗
PubMed1996

Sudden cardiac death in the adult with congenital heart disease.

Preliminary results of a review of sudden cardiac death in the adult with congenital heart disease were presented at the Canadian Adult Congenital Heart (CACH) Network meeting during the Canadian Cardiovascular Society's annual meeting in October 1994. Of 125 patients who were known to have died, sufficient details were available for 92 to determine the circumstance of death. Sudden death occurred in 23 patients (estimated incidence 5.3 per 1000 patients followed per year) at an average age of 33.5 +/- 11.9 years. Surgical procedures included intracardiac repair in 12, palliative procedures in only six and no cardiac surgery in six. Nine patients with sudden death had Eisenmenger syndrome. Right or left ventricular abnormalities were present in 15 of 21 patients with premorbid echocardiographic evaluation. A prior history of ventricular arrhythmia was available in only three patients. Sudden death is a significant cause of mortality in adults with congenital heart disease. Determination of risk factors will be an important aspect of the patient database under development by the CACH Network.

Adult↗
PubMed1995

Cardiopulmonary function in adult patients late after Fontan repair.

OBJECTIVES: The clinical status and exercise assessment of adult patients late after the Fontan operation were reviewed to determine cardiovascular function. BACKGROUND: The Fontan operation is the final operation for many patients with tricuspid atresia or a single ventricle. Follow-up reports describe most patients to be in Canadian Cardiovascular Society functional class I or II. Objective measures of cardiac performance in the pediatric age group have shown significant dysfunction. METHODS: Forty-seven adult patients were seen late after the Fontan operation at the Toronto Congenital Cardiac Centre for Adults. Thirty of these underwent cycle ergometry to determine maximal exercise capacity. Maximal ventilation, maximal oxygen uptake and anaerobic threshold were determined from a ramp exercise protocol. Ejection fraction at rest and during exercise was measured with gated radionuclide angiography. Results were compared with those of eight normal volunteers. Results are given as mean +/- SD. RESULTS: Thirty patients underwent cardiopulmonary exercise testing 6.7 +/- 3.9 years after a first Fontan operation. Clinically 93% were in functional class I or II. The Fontan group patients had a significantly lower maximal work load (548 +/- 171 vs. 1,094 +/- 190 kilopond-meters, p < 0.00001), anaerobic threshold (11.2 +/- 2.9 vs. 23.6 +/- 4.6 ml/kg per min) and maximal oxygen consumption (14.8 +/- 4.5 vs. 42.1 +/- 10.0 ml/kg per min). Systemic ventricular ejection fraction was lower at rest (38 +/- 12% vs. 58 +/- 7%) and during exercise (40 +/- 15% vs. 70 +/- 8%). CONCLUSIONS: Despite a clinical impression of good function, by objective measures adult patients continue to have significant cardiovascular limitation late after the Fontan operation.

Adult↗
PubMed1995

Effect of extracellular potassium concentration on the sodium-potassium pump rate in human lymphocytes.

1. The purpose of this study was to determine whether physiological changes in extracellular free [K+] cause significant changes in the Na(+)-K+ pump rate and intracellular free [Na+]. 2. The Na(+)-K+ pump rate was measured in human lymphocytes by determining ouabain-sensitive 86Rb+ influx at several concentrations of K+. The Na(+)-K+ pump rate increased within the physiological range of extracellular free [K+] (K1/2 = 1.5 mmol/l). 3. To test the hypothesis that elevation of extracellular free [K+] reduces intracellular free [Na+] rapidly, which in turn then slows the pump rate during experimental incubations, lymphocyte intracellular free [Na+] was measured using the fluorochrome sodium-binding benzofuran isophthalate. With larger elevations of extracellular free [K+], intracellular free [Na+] dropped more rapidly. Thus previous discrepancies among determinations of K1/2 may be the result of variations in incubation times, which can skew the pump rates measured during incubations in various extracellular free [K+] values. Steady-state intracellular free [Na+] varied inversely with extracellular free [K+].

Adult↗
PubMed1993

Changes in sodium transport during the human menstrual cycle and pregnancy.

1. We have studied the transport of Na+ and K+ by erythrocytes during the follicular and luteal phases of the human menstrual cycle, and in pregnant compared with non-pregnant women. Venous blood was drawn from 10 healthy young women (not taking any medication or hormones) 1-2 days after menstruation and from the same women 7-9 days after ovulation. For the pregnancy part of the study, blood was drawn from eight other normotensive non-pregnant women and from eight age-matched normotensive pregnant women (36-43 weeks gestation). 2. Intracellular erythrocyte and plasma Na+ and K+ concentrations were measured by flame photometry. The increase in the intracellular Na+ concentration during a 1 h 37 degrees C incubation of fresh whole blood with 0.2 mmol/l ouabain (compared with no ouabain) was measured to determine the rate of active Na+ efflux. The Na(+)-K+ pump rate constant was calculated by dividing the active Na+ efflux rate by the intracellular Na+ concentration. 3. In fresh blood, the intracellular erythrocyte Na+ concentration (P < 0.002) and the plasma K+ concentration (P < 0.01) were both lower in pregnant than in non-pregnant women. The Na(+)-K+ pump rate constant was higher (P < 0.02) during the luteal phase than during the follicular phase, and in pregnant compared with non-pregnant women. 4. We conclude that short-acting hormones in the plasma most probably account for the changes in the Na(+)-K+ pump rate constant during the menstrual cycle.

Adult↗
PubMed1993

Dissociation of changes in metabolic rate and blood pressure with erythrocyte Na-K pump activity in older men after endurance training.

We examined whether changes in resting metabolic rate (RMR) and blood pressure in older normotensive men in response to endurance training were associated with alterations in the Na-K pump activity of plasma-bathed erythrocytes. Eleven men performed cycling exercise three times a week for 8 weeks, and six other men served as controls. Measurements included: RMR by indirect calorimetry, supine blood pressure, body composition by underwater weighing, plasma and erythrocyte Na and K parameters using flame photometry and ouabain. Peak VO2 increased 12% (p < .001), RMR increased 10% (p < .01), mean blood pressure decreased 5% (p < .05), erythrocyte K increased 5% (p < .01), plasma K decreased 7% (p < .001), and plasma Na decreased by 4% (p < .001) in response to training. Erythrocyte Na and Na-K pump rate did not change, nor did the individual changes correlate with changes in RMR or mean blood pressure. Exercise training increases RMR and reduces blood pressure in older men, but these changes are dissociated with erythrocyte Na-K pump activity.

Adenosine Triphosphate↗
PubMed1993

Sodium-potassium pump activity contributes to the age-related decline in resting metabolic rate.

We examined the hypothesis that a decline in Na-K pump activity contributes to the lower resting metabolic rate (RMR) in older males, independent of the loss of fat-free mass. Plasma and erythrocyte Na and K concentrations were measured using flame photometry. Changes in these concentrations after incubation with and without ouabain were used to calculate erythrocyte Na-K pump rate and rate constant in 27 younger (28 +/- 7 yr) and 25 older (67 +/- 6 yr) men. Older men showed an 18% lower erythrocyte Na-K pump rate constant (0.32 +/- 0.09 vs. 0.39 +/- 0.10 h-1; P < 0.01), a 12% lower RMR (1.10 +/- 0.14 vs. 1.25 +/- 0.14 kcal/min; P < 0.01) and an 8% lower level of fat-free mass (61.7 +/- 5.8 vs. 67.4 +/- 8.1 kg; P < 0.01) relative to younger men. A lower RMR persisted in older men (1.14 +/- 0.12 kcal/min) compared to younger men (1.21 +/- 0.12 kcal/min; P < 0.05) after control for the effect of fat-free mass. No differences in RMR were found, however, between older (1.17 +/- 0.13 kcal/min) and younger men (1.20 +/- 0.13 kcal/min) after controlling for both fat-free mass and the erythrocyte Na-K pump rate constant. A positive relation was noted between RMR and the erythrocyte Na-K pump rate constant, after removing the effects of fat-free mass (partial r = 0.30; P < 0.05). Our results support the conclusions that: 1) the in vivo activity of the Na-K pump is related to RMR, and 2) the age-related reduction in Na-K pump activity is a partial contributor to the decline in RMR in older men.

Adult↗
PubMed1993

Transposition complexes.

Transposition complex refers to the reversal of the normal connection of the ventricles to the great arteries, and includes both complete transposition of the great arteries (TGA) and congenitally corrected TGA. Adults with complete TGA usually have had an atrial switch (Mustard or Senning), procedures now abandoned in many pediatric centers in favor of the arterial switch (Jatene). The course and treatment of patients with congenitally corrected TGA is much more variable, depending on which associated lesions are present. Such patients share the tendency to complete heart block, systemic tricuspid AV valve regurgitation, and systemic RV dysfunction. Information about these conditions in adults is urgently needed to reduce our reliance on extrapolation from the pediatric experience.

Humans↗