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Biomedical subjects

C J Porter

Publications and source records attributed to C J Porter.

At least 73 records · Page 4Linked to original sources
PubMed1994

Multiple myocardial hamartomas causing ventricular tachycardia in young children: combined surgical modification and medical treatment.

OBJECTIVE: To describe two cases of incessant ventricular tachycardia caused by multiple myocardial hamartomas. MATERIAL AND METHODS: Two infants, 13 and 14 months old, who had had multiple episodes of symptomatic tachycardia were referred to our institution. Incessant ventricular tachycardia was diagnosed. Initially, the patients received pharmacologic therapy. The recurrent tachycardia resulted in notable hemodynamic instability. No structural abnormalities were detected on the echocardiograms. In one patient, an electrophysiologic study revealed that the site of ventricular ectopic beats was in the anterolateral wall of the left ventricle, midway between the apex and the base. In the other patient, a preoperative electrophysiologic study was not undertaken because of the inability to obtain central venous access. RESULTS: Diffuse hamartomas were found throughout the ventricular myocardium in both patients. Surgical resection and cryoablation of the lesions in combination with medical therapy helped control the tachyarrhythmia. At 7 and 17 months postoperatively, the patients were in normal sinus rhythm and were receiving medication. CONCLUSION: In young children who have incessant ventricular tachycardia but no lesion evident on echocardiography, angiography, or other imaging modalities, a myocardial tumor should be suspected, and pharmacologic therapy should be instituted. If the medical regimen fails, surgical intervention should be undertaken, directed at areas localized by inspection and by preoperative and intraoperative electrophysiologic studies.

Anti-Arrhythmia Agents↗
PubMed1994

Tilt-table testing and oral metoprolol therapy in young patients with unexplained syncope.

OBJECTIVE: Tilt-table testing is useful for investigating unexplained syncope in pediatric patients. No data are available on the use of intravenous metoprolol during testing to identify children who might respond to subsequent oral beta-adrenergic blockade or on the efficacy and safety of such oral therapy. DESIGN: To provide these data, we obtained follow-up information on 27 consecutive pediatric patients who had tilt-table testing for unexplained syncope. RESULTS: Nineteen patients (70%) had positive test results with or without isoproterenol infusion. All these patients had negative test results after intravenous infusion of metoprolol and subsequently were treated with oral metoprolol. Taking oral metoprolol therapy alone, 9 (47%) of the 19 patients were asymptomatic, 8 (42%) reported a decreased frequency of syncopal episodes, and 2 (11%) had unchanged or more frequent episodes. The mean dosage of metoprolol required to prevent symptoms was 1.5 mg/kg per day. Mild side effects were reported by 6 (32%) of the 19 patients. Six patients (32%) required additional medications. CONCLUSIONS: We conclude that metoprolol is safe and effective for the treatment of most cases of neurocardiogenic syncope in children and that this response cannot be predicted accurately by the use of intravenous metoprolol during testing.

Administration, Oral↗
PubMed1993

Carotid sinus syndrome and wrestling.

A 17-year-old boy who lost consciousness during wrestling matches was found to have carotid sinus syndrome. To our knowledge, this report is only the second published case of this entity in an adolescent. Herein we discuss possible implications of this finding for the assessment of syncope in pediatric patients.

Adolescent↗
PubMed1993

Incidence and management of dysrhythmias after Fontan procedure.

The modified Fontan procedure for univentricular heart disease results in the full spectrum of significant cardiac arrhythmias: tachycardias and bradycardias. The tachycardias are primarily supraventricular in origin: 1. atrial flutter, 2. primary atrial tachycardia, 3. atrial fibrillation, and 4. accelerated junctional rhythm or junctional tachycardia; however, ventricular tachyarrhythmias occur also, but less frequently. Bradycardia usually is a result of 1. sinoatrial node dysfunction resulting in junctional rhythm or 2. less commonly, atrioventricular conduction abnormalities, such as second degree and third degree atrioventricular block. Finally, the combination of atrial tachyarrhythmias and sinoatrial node dysfunction can occur in a small but significant number of patients after Fontan surgery. A complete array of medical and pacemaker therapeutic options is necessary for the physician to treat these difficult arrhythmias successfully.

Anti-Arrhythmia Agents↗
PubMed1992

The polyoxyethylene/polyoxypropylene block co-polymer poloxamer-407 selectively redirects intravenously injected microspheres to sinusoidal endothelial cells of rabbit bone marrow.

Small colloidal particulates (150 nm and below, in diameter) can be redirected specifically to the rabbit bone marrow following intravenous administration by coating their surface with the block co-polymer poloxamer-407, a non-ionic surfactant. The coated colloids are sequestered by the sinusoidal endothelial cells of the bone marrow and are accumulated in dense bodies within these cells. The uptake of poloxamer-407-coated colloids by marrow endothelial cells suggests that the steric repulsive barrier, imposed by the polyoxyethylene segment of the polymer, to particle-cell interaction can apparently be overcome by a specific interaction mechanism(s) with the cell surface. Such a dramatic uptake cannot be achieved with other block co-polymers of similar structure to poloxamer-407. The application of the current model for the site-specific targeting of drug carriers to bone marrow and the prevention of the adherence of metastases of tumours which selectively colonize the bone marrow endothelium is discussed.

Animals↗
PubMed1991

Non-phagocytic uptake of intravenously injected microspheres in rat spleen: influence of particle size and hydrophilic coating.

A recent development in prolonging the circulation time of drug carriers, such as liposomes and microspheres, has been to minimize their removal by macrophages of the reticuloendothelial system by covering their surface with hydrophilic polymers such as poloxamers, poloxamines and poly(ethyleneglycols). Here we demonstrate that this strategy may not necessarily prolong the circulatory half-life of drug carriers in all animal models. In rats, as opposed to rabbits, a non-phagocytic mechanism in the spleen may be triggered to remove efficiently from the blood drug carriers coated with hydrophilic coatings. Both the size of particle and its hydrophilic coating may act synergistically to trigger this non-phagocytic mechanism. In rats, a remarkable log to log relationship between particle size and spleen uptake was observed for both uncoated and polymeric coated microspheres. The potential implication of these observations in site-specific delivery of drug carriers is discussed.

Animals↗
PubMed1991

Investigation of products arising from enzymatic digestion of advanced glycated albumin by high-performance liquid chromatography/mass spectrometry.

The structural investigation of the products arising from 28 days incubation of albumin with high glucose concentration and further enzymatic hydrolysis has been carried out by means of high-performance liquid chromatography/mass spectrometry (HPLC/MS) under plasmaspray conditions. By this approach many different compounds have been detected, and for most of them, possible structures have been proposed on the basis of literature data and molecular weight assignments.

Animals↗
PubMed1991

Detecting arrhythmia by exercise electrocardiography in pediatric patients: assessment of sensitivity and influence on clinical management.

We studied 49 patients with suspected arrhythmias (group 1) and 92 patients with previously documented arrhythmias (group 2) who underwent exercise electrocardiography (EECG) at our institution between 1979 and 1987. Among group 1 patients, all of whom had sinus rhythm before exercise, 10 (20%) had abnormal findings on EECG, and treatment was modified in 4 of these 10 (8% of group 1). Further testing (24-hour ambulatory or transtelephonic electrocardiographic monitoring or electrophysiologic study) of the 39 patients with normal EECG findings revealed 8 additional patients with arrhythmias. In group 1, the sensitivity of EECG was 56%, and its negative predictive value was 79%. Group 2 consisted of 38 patients with atrial arrhythmias, 31 with ventricular arrhythmias, and 23 with atrioventricular conduction abnormalities before EECG. Of these 92 patients, 68 (74%) had abnormal EECG findings. All but 1 of the 24 patients with normal findings underwent further testing, and rhythm abnormalities were induced in 16. Patients with atrial arrhythmias were more likely to have normal EECG results (42%) than were those with ventricular arrhythmias (23%) or an atrioventricular conduction abnormality (4%). Of the 35 patients who had been referred for suppression of an arrhythmia, 25 (71%) had abnormal rhythm suppressed during exercise. Clinical management was modified in 27% of group 2 patients on the basis of EECG findings.

Adolescent↗
PubMed1990

Long-term outcome after surgical repair of isolated atrial septal defect. Follow-up at 27 to 32 years.

BACKGROUND: Atrial septal defects have been surgically correctable for more than 30 years. The long-term survival rates among patients treated in the early era of cardiac surgery are poorly documented, but such data are of critical importance to the future medical care, employability, and insurability of these patients. METHODS: To determine the natural history of surgically corrected atrial septal defects, we studied all 123 patients who underwent repair of an isolated defect (ostium secundum or sinus venosus) at the Mayo Clinic between 1956 and 1960, 27 to 32 years after the procedure. The follow-up status of all patients was determined by written questionnaires and telephone interviews. Hospital records and death certificates were obtained if interim hospitalization or death had occurred. RESULTS: The overall 30-year actuarial survival rate among survivors of the perioperative period was 74 percent, as compared with 85 percent among controls matched for age and sex. The perioperative mortality was 3.3 percent (four deaths). Actuarial 27-year survival rates among patients in the younger two quartiles according to age at operation (less than or equal to 11 years and 12 to 24 years) were no different from rates among controls--97 percent and 93 percent, respectively. In the two older quartiles (25 to 41 years and greater than 41 years), 27-year survival rates were significantly less (P less than 0.001)--84 percent and 40 percent, respectively--than in controls (91 and 59 percent). Independent predictors of long-term survival according to multivariate analysis were age at operation (P less than 0.0001) and systolic pressure in the main pulmonary artery before operation (P less than 0.0027). When repair was performed in older patients, late cardiac failure, stroke, and atrial fibrillation were significantly more frequent. CONCLUSIONS: Among patients with surgically repaired atrial septal defects, those operated on before the age of 25 have an excellent prognosis, but older patients require careful, regular supervision.

Actuarial Analysis↗
PubMed1990

Sudden death after repair of double-outlet right ventricle.

The outlook for patients with double-outlet right ventricle has improved since the development of corrective operations. Late arrhythmic deaths after successful procedures have been reported; however, the magnitude remains unknown. This study was undertaken to identify the magnitude of late sudden death and the significant factors associated with it. From 1965 through 1985, 118 patients underwent corrective operation for double-outlet right ventricle; of these, 23 died in the hospital and six were lost to follow-up. The 89 remaining patients (52 male and 37 female) made up the study population. Their mean age (+/- SD) was 10.3 +/- 7.8 years at the time of repair. The mean duration of follow-up was 82 months. Of the 22 late deaths, 16 (73%) were sudden. Eight (50%) of the sudden deaths occurred within 1 year of operation. Cox proportional hazards multivariate analysis revealed the following significant risk factors for late sudden death: older age at the time of operation, perioperative or postoperative ventricular tachyarrhythmias, and third-degree atrioventricular block. Factors not associated with late sudden death included year of operation, sex, type and number of associated cardiac anomalies, preoperative functional class, previous palliative procedures, surgical technique, perioperative or postoperative single premature ventricular contractions, and postoperative left or right bundle branch block with or without fascicular block. We conclude that the incidence of late sudden death after successful surgical repair of double-outlet right ventricle is very high. Complete corrective operation at an early age and aggressive diagnosis and treatment of arrhythmias and conduction defects after operation are warranted.

Adolescent↗
PubMed1989

Utility of temporary atrial epicardial electrodes in postoperative pediatric cardiac patients.

The utility of atrial electrograms recorded from temporary bipolar atrial epicardial electrodes in postoperative pediatric cardiac patients was assessed by (1) examining the accuracy of the surface electrocardiographic tracings and (2) analyzing the treatment modalities used for the arrhythmias diagnosed on the basis of the atrial electrograms. Atrial electrograms were obtained simultaneously with single-lead surface electrocardiographic recordings from 20 pediatric patients (ages 7 months to 11 years) after intracardiac repair of congenital heart defects. Interpretations of 25 surface recordings by five pediatric cardiologists were compared with analyses of the electrograms. Sinus rhythm was interpreted correctly by most reviewers 100% of the time, whereas atrioventricular conduction disturbances and narrow QRS tachycardias were identified correctly 77% and 14% of the time, respectively. Of those rhythms incorrectly interpreted, 89% had some type of active therapeutic intervention. Single-lead surface electrocardiographic recordings are imprecise for evaluating postoperative rhythms in pediatric cardiac patients, and our experience suggests that rhythms for which active intervention is necessary may be more difficult to interpret correctly by surface monitoring alone.

Arrhythmias, Cardiac↗
PubMed1988

Characterization of glutathione conjugates by fast atom bombardment/tandem mass spectrometry.

The collisionally activated decomposition of [M + H]+ ions, generated by fast atom bombardment (FAB) of glutathione conjugates, has been studied by tandem mass spectrometry (MS/MS) using hybrid sector/quadrupole instruments. Abundant fragments of diagnostic utility were present in the daughter ion spectra. Common fragmentation modes were observed but their relative importance was strongly dependent on the nature of the conjugated species. As an example of a general approach to the characterization of glutathione conjugates in biological samples, the acetaminophen-glutathione conjugate was identified in rat bile, following coadministration of (2H0)- and (2H3)acetaminophen, using the experimental sequence: (i) conventional FAB mass spectrometric analysis, (ii) MS/MS using constant neutral loss (129 u) scanning to identify parent ions corresponding to glutathione conjugates, (iii) MS/MS to yield daughter ion spectra of parents so identified and corresponding to (2H0)- and (2H3)-labeled conjugates.

Animals↗
PubMed1988

Long-term outcome of patients undergoing surgical repair of isolated pulmonary valve stenosis. Follow-up at 20-30 years.

In a group of 191 consecutive patients who underwent operation at the Mayo Clinic for isolated pulmonary valve stenosis between 1956 and 1967, late results were excellent. In patients surviving operation before the age of 21 years, long-term survival was similar to that in an age- and sex-matched control population. In the other patients, late survival and functional status were good, but survival was poorer than in the control population. This late attrition, most likely due to the sequelae of long-standing right ventricular hypertrophy, suggests the need for continued surveillance. Late sudden death occurred in only three patients, between 10 and 21 years postoperatively. The finding of normal life expectancy for such patients who survive operation before age 21 is important for actuarial purposes and for the patients' career and employment plans.

Adolescent↗
PubMed1988

The modified Fontan operation for asplenia and polysplenia syndromes.

From 1975 through 1986, 49 patients with asplenia (23 patients) or polysplenia (26 patients) syndromes underwent a modified Fontan operation. All patients had anomalous systemic venous return, and 43 (88%) had anomalous pulmonary venous return. The atrioventricular valve anatomy varied: 36 patients had a common atrial chamber and common atrioventricular valve, eight had mitral valve atresia, and five had severe mitral valve hypoplasia. Redirection of systemic venous return was accomplished by (1) atrial baffle (29 patients), (2) intraatrial conduit (19 patients), and (3) extraatrial conduit (one patient). There were 21 (43%) hospital deaths overall. However, since 1985, six of 22 patients (27%) have died. Increased mortality was seen in patients requiring atrioventricular valve repair or replacement (8/11, 73%) and in patients with asplenia (65%). Lower mortality was seen in patients with polysplenia (24%) and those receiving an intraatrial conduit (26%), although this decrease also represents the more recent experience. We conclude: (1) The Fontan operation for patients with asplenia or polysplenia syndromes has resulted in a significant (although recently declining) mortality; (2) mortality is higher in patients with asplenia; (3) patients with atrioventricular valve insufficiency requiring repair or replacement are at higher risk; and (4) intraatrial conduits seem to offer promise for successfully accomplishing this repair.

Abnormalities, Multiple↗