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Biomedical subjects

A V Mehta

Publications and source records attributed to A V Mehta.

At least 55 records · Page 3Linked to original sources
PubMed1984

M-mode echocardiographic findings in children with idiopathic restrictive cardiomyopathy.

The M-mode echocardiographic findings in five pediatric patients, ages 4-15 years, with primary idiopathic restrictive cardiomyopathy, diagnosed by cardiac catheterization, and of 12 normal children (control group) are presented. The M-mode echocardiographic findings in patients with restrictive cardiomyopathy were (1) normal left and right ventricular end-diastolic dimension, (2) normal left ventricular posterior wall and interventricular septal thickness (three patients) or mild concentric hypertrophy (two patients), (3) normal opening and closing velocity of the mitral valve, (4) consistently enlarged left atrium (more than 40 mm) in all, and (5) right ventricular systolic time intervals compatible with pulmonary artery hypertension. The left ventricular ejection phase parameters (systolic time intervals, shortening fraction, and mean velocity of circumferential fiber shortening) were normal. Left ventricular relaxation phase parameters (diastolic function) were abnormal. The isovolumic relaxation time index was prolonged, 68 +/- 40 ms (+/- SD), in the study group as compared with 11 +/- 6 ms (+/- SD) in the control group (P less than 0.001). Percent relaxation of left ventricular posterior wall endocardium at 50% of diastole was decreased, 58 +/- 4% (+/- SD), in the study group as compared with 85 +/- 6% (+/- SD) in the control group (P less than 0.005). We conclude that M-mode echocardiography provides a relatively useful and specific noninvasive method for the diagnosis of primary restrictive cardiomyopathy in pediatric patients.

Adolescent↗
PubMed1984

Induction of nonsustained atrial flutter by programmed atrial stimulation in children: incidence, mechanisms, and clinical implications.

Nonsustained atrial flutter was induced by programmed atrial extrastimulation in 6 (4%) of 137 children with preoperative congenital heart defects, who underwent electrophysiologic evaluation as part of cardiac catheterization. None of these patients had ECG or clinical evidence of arrhythmias. Atrial reentry was induced by programmed atrial extrastimulation in these six patients at coupling intervals slightly longer than the coupling interval at which flutter was induced. The flutter cycle length was similar to the atrial refractory periods. The duration ranged between 0.4 second and 60 seconds. The PA interval and the duration of the P wave were normal in all of the patients. Five of the six had normal PR intervals. It is concluded that nonsustained atrial flutter may be induced by programmed atrial extrastimulation in dysrhythmia-free children. The cycle length is determined by atrial refractoriness and, contrary to adults with clinical atrial flutter, prolonged PA and P wave duration are not predisposing factors.

Adolescent↗
PubMed1983

Hemodynamics and intracardiac conduction after operative repair of tetralogy of Fallot.

Electrophysiologic studies were performed in 47 children aged 3 to 18 years, 15 of whom had cardiac arrhythmias 1 to 15 years after repair of tetralogy of Fallot. Six exhibited sinus or atrioventricular nodal dysfunction, 8 had ventricular extrasystoles, and 1 had supraventricular tachycardia. Hemodynamic and electrophysiologic data were obtained at postoperative catheterization. Although electrophysiologic responses were abnormal in a proportion of both the children with and those without arrhythmia, hemodynamic values were similar. Three of 6 children with impaired sinus impulse generation or atrioventricular nodal conduction had a prolonged A-H interval, and in 3 Wenckebach heart block developed at low pacing rates. Ventricular ectopic rhythm was not associated with any particular abnormality of basic intracardiac conduction intervals. Thus, arrhythmias and conduction abnormalities are not consistently related to residual right ventricular hypertension. Abnormalities in electrophysiologic function are common after repair of tetralogy of Fallot in patients with sinus rhythm and may have prognostic implications for these patients.

Adolescent↗
PubMed1983

Multiple atrioventricular nodal pathways--a new electrophysiological phenomenon in children.

Multiple atrioventricular (A-V) nodal pathways are described in five dysrhythmia-free children with congenital heart defects. The five were some (2.9%) of 175 children who underwent diagnostic cardiac catheterization and electrophysiological evaluation over a three year period. Supraventricular tachycardia was not induced during the electrophysiological evaluation. Medical follow-up is recommended since multiple A-V nodal pathways have been demonstrated in adults with A-V nodal reentrant tachycardia.

Adolescent↗
PubMed1983

Blood pressure response to dynamic exercise in adolescents before and after percutaneous transluminal renal artery angioplasty.

The blood pressure response to maximal bicycle exercise was studied using the James protocol in two adolescents with renal artery stenosis before and after percutaneous transluminal renal artery angioplasty. Prior to angioplasty, one patient (pt A) had persistent and one patient (pt B) had labile elevation of the resting blood pressure above the 95th percentile for age; both patients had elevated systolic blood pressure at maximal exercise (pt A: 215 mm Hg; James expected 170 +/- 20; pt B: 228 mm Hg; James expected 156 +/- 15). Following angioplasty, both patients had resting blood pressures below the 95th percentile for age; patient A had improved systolic pressure at maximal exercise (195 mm Hg) while patient B had persistent elevation in the exercise systolic blood pressure (215 mm Hg). Angiography confirmed the presence of residual/recurrent renal artery stenosis in patient B. We conclude that measurement of blood pressure during exercise may reveal residual abnormalities not apparent at rest and thus may be useful in assessing the result of renal artery angioplasty in children with renal artery stenosis.

Adolescent↗
PubMed1982

Right ventricular apical activation time in children. Reference standards for clinical use.

To differentiate proximal from peripheral right bundle-branch block, several investigators have used the right ventricular apical (RVA) activation time, but there is a lack of reference standards for infants and other children. Using intracardiac electrography, His bundle and RVA electrograms were recorded in 123 children before surgery for various types of congenital cardiac malformations. None had evidence of conduction defects on their surface ECG. The average RVA activation time was 15 +/- 7 msec (+/- SD) linearly increasing with age from infancy to adolescence. The values found in this large population may be useful as reference standards for right bundle-branch conduction times in other infants and children.

Adolescent↗
PubMed1982

Procainamide elimination kinetics in pediatric patients.

Procainamide kinetics were studied in six children after a single intravenous dose. Two-compartment kinetic analysis of serum concentration-time curves of five children, who received a dose of 5.5 +/- 0.9 mg/kg (mean +/- SD), revealed the following values for kinetic parameters: distribution half-life, 10.3 +/- 3.4 min; elimination half-life, 1.7 +/- 0.1 hr; elimination constant, 1.2 +/- 0.3 hr-1; plasma clearance 19.4 +/- 2.0 ml/min/kg, and steady-state volume of distribution, 2.2 +/- 0.3 l/kg. A sixth patient, who received an accidental overdose of 28 mg/kg, had altered elimination kinetics due to drug-induced hypotension. N-acetylprocainamide (NAPA) was detected in serum samples obtained soon after procainamide dosing and peak concentrations were attained at 1 to 2 hr. NAPA levels were lower than corresponding procainamide concentrations at most sampling periods. The findings of short elimination half-life and rapid plasma clearance of procainamide in children suggest that continuous intravenous infusion may be necessary to maintain therapeutically effective plasma concentrations in these patients.

Arrhythmias, Cardiac↗
PubMed1982

Sinus and atrioventricular nodal function: Preoperative and early postoperative assessment in children.

Ninety-three rapid atrial pacing studies were performed in 38 children to compare preoperative and early postoperative function of the sinus and atrioventricular (AV) nodes. The interval between the preoperative and postoperative studies was under 6 months in the majority of patients. Postoperative studies were performed within 48 hours of operation and between 4 and 8 days after operation. Sinus nodal function as measured by sinus nodal recovery time (SNRT) was an unreliable index in determining depression since the number who improved postoperatively (10/55) was nearly equal to the number that worsened (12/55). The majority who had abnormal function postoperatively demonstrated a junctional rather than sinus recovery focus. This finding appears a more definitive and more reproducible indicator of sinus node depression in the postoperative patient. Postoperative AV nodal function was decreased (as measured by the cycle length [CL] at which Wenckebach periodicity occurred) in 15 of 55 studies (27%) of the entire group. There was nearly an equal chance for improvement (24%) in function. This also applied to those patients who had sequential studies. Therefore, this method of assessment for AV nodal function was unreliable, or else the operation did not affect the node significantly. The latter is unlikely in view of late postoperative data. The greatest utility of this test was to determine the capability for AV conduction in certain patients with slow escape rhythms in the absence of surface P waves, and to differentiate complete heart block from AV dissociation when atrial activity was absent. Despite the variability of effects on the sinus and AV nodes in these patients, those who demonstrated depression had a significantly higher incidence of dysrhythmias (80% of patients with sinus nodal depression and 100% of patients with AV nodal depression).

Adolescent↗
PubMed1981

Determinants of ventricular refractory periods in children with congenital heart disease: effects of cycle length and age.

Ventricular effective refractory periods (ERP) and functional refractory periods (FRP) were determined by programmed ventricular extrastimulation in 53 pediatric patients with a spectrum of congenital heart disorders. Of these 63 children (ages 8 months to 18 years), 38 were preoperative, 17 had repair of their cardiac lesion via right ventriculotomy, and eight were postoperative without a ventriculotomy. We demonstrated that there was a linear relationship between the cycle length and ventricular refractory periods. The regression equations 73 + 0.29 x cycle length (msec) for the ventricular ERP (msec) and 80 + 0.30 x cycle length (msec) for ventricular FRP (msec) were found to define the determined properties of ventricular refractory periods (VRP) in children. These VRP characteristics were independent of age in children less than 13 years of age.

Action Potentials↗
PubMed1981

Echocardiographic assessment of right bundle branch injury after repair of tetralogy of Fallot.

Nineteen patients, ages 3 1/2-18 years, with electrocardiographic evidence of right bundle branch injury after intracardiac repair of tetralogy of Fallot, underwent invasive intracardiac electrophysiologic evaluation 1-13 years (mean 4.4 years) postoperatively. Categorization of the site of right bundle branch injury as proximal or distal was made by determining the V-RVA interval. In 11 of the patients, the V RVA interval was prolonged (> 35 msec), indicating proximal right bundle branch injury and in the other eight it was normal (< 35 msec), indicating distal bundle branch injury. Within 24 hours of the study, all patients were studied by M-mode echocardiography. Measurements were made of the tricuspid valve closure, mitral valve closure and the difference between the two, or the delta value. All but one patient with distal bundle branch injury had delta values of less than 40 msec (range 8-38 msec), while 10 or 11 patients with proximal bundle branch injury had delta values greater than 40 msec (range 41-116 msec). there was a significant positive correlation (r = 0.74, p < 0.001) between V-RVA and the delta value. We conclude that the delta value is an indicator of relative activation delay of the right ventricle, and therefore, in most cases, proximal vs distal bundle branch injury can be diagnosed noninvasively.

Adolescent↗
PubMed1981

Congenital systemic arteriovenous fistula between the descending aorta, azygos vein, and superior vena cava.

Various congenital systemic arteriovenous fistulas have been described. An unusual case of congenital systemic arteriovenous fistula arising from the descending aorta and draining separately into the superior vena cava, the azygos vein, and the innominate vein is reported. Clinically, this case simulated a patent ductus arteriosus. To our knowledge, this particular anomaly has not been described before.

Angiography↗
PubMed1980

Dual atrioventricular nodal pathways: a benign finding in arrhythmia-free children with heart disease.

The incidence and significance of dual atrioventricular (A-V) nodal pathways are described in 78 children with associated congenital or acquired heart disease. None of these patients had clinical or electrocardiographic evidence of arrhythmia. Dual A-V nodal pathways were observed in 35 percent of the preoperative group and in 33 percent of the postoperative group. Despite this substrate for A-V nodal reentry, supraventricular tachycardia was neither induced during electrophysiologic evaluation nor did it develop clinically over a follow-up period of 1 month to 15 years. It is concluded that dual A-V nodal pathways are common and may be a benign finding in arrhythmia-free children with heart disease.

Adolescent↗
PubMedDate not supplied

Familial symptomatic sinus bradycardia: autosomal dominant inheritance.

Symptomatic sinus bradycardia, due to either sick sinus syndrome or vagotonia, can be familial, affecting several members of a family. We report an 18-year-old male patient with palpitations and limited exercise capacity who was noted to have severe sinus bradycardia. His resting heart rate was 40/min, with normal PR and corrected QT intervals, and sinus pauses up to 6 seconds during sleep. Exercise treadmill test and pharmacologic autonomic blockade during electrophysiologic studies abolished the bradycardia, suggestive of vagotonia rather than intrinsic sinus node dysfunction. This patient's father and a female cousin had a similar clinical history but associated with syncope and severe sinus bradycardia. The mode of transmission appeared to be autosomal dominant. All three have permanent demand pacemakers implanted and are asymptomatic.

Adolescent↗
PubMedDate not supplied

Polysplenia.

Explore the source record for details and available documents.

Heart Block↗
PubMedDate not supplied

Long-term efficacy and safety of atenolol for supraventricular tachycardia in children.

Propranolol, a first-generation nonselective beta-adrenoceptor blocking agent, is commonly used to treat pediatric arrhythmias. Atenolol, relatively long-acting, cardioselective beta-adrenoceptor blocking agent, has been successfully used in adults with supraventricular tachycardia (SVT). There is only one report on the use of atenolol in children with SVT; and our report is on the first long-term prospective study to evaluate the use of atenolol in children. A group of 22 children < 18 years of age with clinical SVT were enrolled in the study. The tachycardia was documented on electrocardiograms in each case and was confirmed by electrophysiologic studies in some. Once-a-day oral atenolol was started as a monotherapy. Of the 22 children with various types of SVT, 13 (59%) were well controlled on long-term oral atenolol therapy. The effective dose of atenolol ranged between 0.3 and 1.3 mg/kg/day (median effective dose 0.7 mg/kg/day). Five children had some adverse effects. However, none in the successful group of 13 patients required drug discontinuation because of such effects. Once-a-day oral atenolol as a monotherapy is effective and relatively safe for long-term management of SVT during childhood. It is an attractive alternative beta-adrenoceptor blocking agent for the management of pediatric arrhythmias.

Adolescent↗