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Biomedical subjects

M Akhtar

Publications and source records attributed to M Akhtar.

At least 271 records · Page 15Linked to original sources
PubMed1990

Reentrant junctional tachycardias.

Most of the tachycardia arising in the atrioventricular (AV) junction are reentrant in nature. The two most common variety are AV nodal reentry and AV reentry utilizing an accessory pathway of the Kent bundle type. Typically these tachycardias have narrow QRS complex and are regular but an associated right or left bundle branch block could result in a wide QRS complex. Other mechanisms for wide QRS in AV junctional tachycardia include: (a) antidromic reentry; (b) preexcited tachycardia using two accessory pathways; (c) AV nodal reentry with incidental accessory pathway participation; and (d) atriofascicular (nodoventricular)e Mahaim participation. A variety of surface ECG and intracardiac electrophysiological methods are used to delineate the precise mechanisms which is essential for successful nonpharmacological therapy in these patients.

Atrioventricular Node↗
PubMed1990

Automatic implantable cardioverter/defibrillator discharges and acute myocardial injury.

Multiple defibrillations by the automatic implantable cardioverter/defibrillator (AICD) have been reported to result in localized epicardial damage. No data exist, however, regarding whether this damage can be detected in the clinical setting or whether it interferes with the detection of true myocardial infarction. Forty-nine patients who received defibrillations by patch electrodes were studied prospectively. We attempted to document the presence of myocardial injury with the following three commonly used modalities for the detection of myocardial infarction: serial electrocardiographic changes, serial creatine phosphokinase (CPK) and CPK-MB release, and technetium 99m pyrophosphate scanning. Fifteen patients received defibrillations by AICD patches at the time of AICD generator replacement. Nine patients received defibrillations at the time of new AICD lead placement. The average total energy delivered was 85 +/- 29 J. None of these patients had detectable myocardial injury. Ten patients had defibrillations by the AICD patches at the time of bypass operation. One patient in this group developed acute myocardial infarction in the inferior wall after posterior descending coronary bypass operation, as detected by electrocardiogram, 99mTc pyrophosphate scanning, and CPK-MB analysis. Fifteen patients were evaluated for spontaneous AICD discharges. Thirteen had a maximum of five consecutive shocks, and cumulative energy delivered was not greater than 330 J. None of these patients had detectable injury. Two patients had CPK-MB release of 15.3% and 7.5%, respectively. One of these patients had a positive 99mTc pyrophosphate scan. These two patients received 12 and 17 rapid and consecutive AICD discharges, respectively, with cumulative delivered energy of 360 and 510 J, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1990

Carcinoma of the cervix in a pregnant woman with negative Pap smears and colposcopic examination.

A case is reported of squamous cell carcinoma of the cervix developing in a pregnant woman while manifesting five consecutive false-negative Pap smears and colposcopic appearance suggestive of dysplasia. Pap smears and colposcopic examinations are helpful in diagnosing dysplastic and early cancerous lesions of the uterine cervix. We describe a case where both Pap smears and colposcopy failed to diagnose an early occult invasive lesion in the cervix of a pregnant woman who manifested only CINIII by colposcopy, while the Pap smear was falsely negative on five consecutive occasions.

Adult↗
PubMed1989

Dysgerminoma of the ovary with rhabdomyosarcoma. Report of a case.

A 14-year-old girl with a large left ovarian mass underwent excision of the tumor which on histologic examination revealed dysgerminoma mixed with elements of rhabdomyosarcoma. A subsequent staging laparotomy revealed a solitary 1-cm nodule along the pelvic wall. This was composed of rhabdomyosarcoma. Review of literature revealed that soft tissue sarcomas of several types may on occasion be seen in association with gonadal and extragonadal mixed germ cell tumors or in spermatocytic seminoma of the testis. However, no previously published report of a sarcoma arising in a pure dysgerminoma was found in the literature.

Adolescent↗
PubMed1989

Interplay of phosphorylation and dephosphorylation in vision: protein phosphatases of bovine rod outer segments.

Two types of protein phosphatases were identified in carefully prepared bovine rod outer segments (ROS). Extraction of the ROS with a medium-salt buffer solubilized protein phosphatase activity that was mainly type 2A, since it was active toward phosphorylase a in the absence of divalent cations, was not retained by heparin-Sepharose, dephosphorylated the alpha-subunit of phosphorylase kinase faster that the beta-subunit, and was unaffected by inhibitor 2. Further extraction of the resulting membranes with a high-salt buffer solubilized additional phosphatase activity which was predominantly type 1, since it was retained by heparin-Sepharose and was blocked by inhibitor 2. The molecular mass of the type 2A phosphatase estimated by gel permeation chromatography on Superose 12 was 100 kDa, suggesting it may be the 2A2 form. Only the ROS type 2A phosphatase dephosphorylated opsin and rhodopsin efficiently. Concordant with this finding, the purified catalytic subunit of protein phosphatase 2A from rabbit skeletal muscle dephosphorylated opsin efficiently, while the type 1 catalytic subunit isolated from this tissue was inactive. Together, the results suggest that the ROS type 2A protein phosphatase plays an important role in regenerating rhodopsin from the various phosphorylated species in vivo. The activity of the enzyme per retina (approximately 85 pmol of Pi released/min) is comparable to that of rhodopsin kinase (100 pmol of phosphate transferred/min).

Animals↗
PubMed1989

Treatment of atrioventricular node reentrant tachycardia with encainide: reversal of drug effect with isoproterenol.

To determine the efficacy of encainide in the treatment of atrioventricular (AV) node reentrant tachycardia, Holter electrocardiographic (ECG) monitoring, exercise treadmill testing and programmed electrical stimulation were performed in 16 patients while they were taking no medication and after steady state levels were reached during treatment with encainide (75 to 200 mg/day; mean 117 +/- 47). In addition, to study the possible reversal of drug effects by sympathetic stimulation, AV node conduction and tachycardia induction were reassessed during isoproterenol infusion (1 to 3 micrograms/min), a dose calculated to increase the rest heart rate by 25 +/- 10%. Sustained AV node reentrant tachycardia could be initiated in all 16 patients in the control state, in 2 patients after encainide and in 10 patients during isoproterenol infusion. The shortest mean atrial paced cycle length sustaining 1:1 AV conduction was 358 +/- 57 ms during the control study, which increased to 409 +/- 59 ms with encainide (p less than 0.01 versus control) and decreased to 313 +/- 31 ms during isoproterenol infusion (p less than 0.01 versus control and encainide). The shortest mean ventricular paced cycle length with 1:1 ventriculoatrial conduction was 337 +/- 56 ms in the control study, 551 + 124 ms with encainide infusion (p less than 0.01 versus control) and 354 +/- 72 ms during isoproterenol infusion in the encainide-loaded state (p less than 0.01 versus both control and encainide). During a mean follow-up period of 19 +/- 10 months, significant clinical recurrences occurred in 4 of the 10 patients in whom tachycardia could still be initiated with encainide (with or without isoproterenol).(ABSTRACT TRUNCATED AT 250 WORDS)

Anilides↗
PubMed1989

Cryoablation of refractory sustained ventricular tachycardia due to coronary artery disease.

Thirty-nine patients with medically refractory sustained monomorphic ventricular tachycardia (VT) due to coronary artery disease underwent map-guided cryosurgery. Locations of prior myocardial infarctions had been inferior in 22, anterior in 16 and combined in 1. Mean age was 61 +/- 9 years and the mean number of drug trials per patient before surgery was 3.8 +/- 1.4. Intraoperative endocardial mapping induced 67 tachycardias in 35 patients. Each patient received 6 to 18 (11 +/- 3) endocardial cryothermic applications (15 mm, -60 degrees C, 2 minutes) at areas of earliest activation during VT. Encircling endocardial cryoablation was performed in 4 patients who had unsuccessful mapping. In addition, 11 patients had subendocardial resection of their well-demarcated septal scars as well as cryosurgery. There were 2 in-hospital deaths. At postoperative programmed ventricular stimulation, 28 of the 37 patients (76%) had no inducible or spontaneous VT before hospital discharge. Six patients (16%) with spontaneous or inducible VT had a single morphology and were controlled with antiarrhythmic drugs that had previously failed. Therefore, surgery alone or in combination with drugs was efficacious in 92% of the population surviving surgery. The remaining 3 patients (8%) received automatic implantable cardioverter defibrillators. No significant difference in surgical outcome was seen between patients who had cryosurgery alone and those who had subendocardial resection together with cryoablation. Mean left ventricular ejection fractions before and after surgery were 33 and 39%, respectively (p less than 0.01). Clinical follow-up ranged from 2 to 36 months (18 +/- 12). One patient died of heart failure and another underwent heart transplantation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Fine-needle biopsy: comparison of cellular yield with and without aspiration.

Fine-needle biopsies with and without aspiration were performed on 103 lesions, and the cellular yields obtained by the two techniques were compared. A scoring system was devised by which the amount of material obtained in each needle stick was estimated. The mean score/stick for fine-needle biopsy with aspiration was 2.7; for biopsy without aspiration, it was 2.9. The results of this study indicate that there is no significant difference in the amount of cellular material obtained by the two techniques. It is concluded that needle biopsy without aspiration may be performed routinely with good results.

Biopsy, Needle↗
PubMed1989

Fine-needle aspiration biopsy of clear-cell sarcoma of the kidney: light and electron microscopic features.

Smears from seven fine-needle aspiration biopsies from three patients with clear-cell sarcoma of the kidney were reviewed, and the findings were correlated with corresponding histopathologic appearances. In two cases, the tumor cells were polygonal to spindle-shaped and were loosely arranged in a matrix of mucoid material. The histopathologic examination of the resected tumors in these cases revealed a classic pattern. In the third case, the aspiration smears revealed round to polygonal cells with moderate to abundant cytoplasm but without the mucoid matrix. The predominant histologic appearance of this tumor was an epithelioid trabecular pattern. Electron microscopic findings were similar to those described in published studies.

Biopsy, Needle↗
PubMed1989

Aspiration cytology of Wilms' tumor: correlation of cytologic and histologic features.

We examined the cytomorphologic features of fine-needle aspiration biopsy (FNAB) specimens from 23 Wilms' tumor patients. The findings were correlated with histopathologic patterns from these tumors. The study revealed a close resemblance between the cytologic and histopathologic appearance of various cellular elements in Wilms' tumors. The major cellular patterns seen in Wilms' tumor include blastemal cells, blastemal cells with epithelial differentiation, blastemal cells with tubular differentiation, and stromal elements. It is hoped that recognition of these cellular components in aspiration smears will be helpful in establishing an FNAB diagnosis of Wilms' tumor.

Biopsy, Needle↗
PubMed1989

Isoproterenol reversal of antiarrhythmic effects in patients with inducible sustained ventricular tachyarrhythmias.

Seventeen patients (16 men and 1 woman) were challenged with isoproterenol after their initially inducible sustained ventricular tachyarrhythmia (monomorphic tachycardia in 14 patients and fibrillation in 3) was completely suppressed by class I antiarrhythmic drugs. Coronary artery disease was documented in 11 patients, dilated cardiomyopathy in 2 and no structural heart disease in the remaining 4 patients. The initial presentation was aborted sudden cardiac death (five patients), syncope (eight patients) and symptomatic nonsustained ventricular tachycardia (four patients). The antiarrhythmic drug that rendered the initial ventricular tachyarrhythmias noninducible was class IA in 11 cases, class IC in 5 and combined class IA and IB in 1. The original ventricular tachyarrhythmia became reinducible in 10 patients (group A) and remained noninducible in 7 patients (group B) after isoproterenol infusion at a rate necessary to achieve a 20% increase in heart rate. Despite the results of isoproterenol challenge, all patients were maintained on their electrophysiologically guided antiarrhythmic regimen. During a mean follow-up period of 13 +/- 9 months, 3 of the 10 patients in group A experienced clinical recurrence of tachyarrhythmia; no recurrence was noted in group B. In conclusion, reinducibility of ventricular tachyarrhythmia after beta-adrenergic stimulation seems to identify a subgroup of patients at high risk of subsequent arrhythmic events. Beta-adrenergic blockade or surgical therapy may be indicated in some patients with a positive isoproterenol challenge.

Adult↗
PubMed1989

Endodermal sinus (yolk sac) tumor in infants and children. A clinical and pathologic study: an 11 year review.

We reviewed the clinical features, treatment, and results of children with gonadal and extragonadal yolk sac (endodermal sinus) tumors seen in the King Faisal Specialist Hospital and Research Centre between 1976 and 1987. There were nine children (seven girls and two boys) with ages ranging from 7 months to 12 years (median of 3.5 years). Sites of origin included the vagina (two cases), face (two cases), sacrum (two cases), mediastinum (one case), ovary (one case), and testicle (1 case). All children had elevated alpha-fetoprotein (AFP) at diagnosis. One girl had complete surgical excision of an ovarian tumor at the time of diagnosis, and one boy had surgical excision of the testis. In the remaining seven children, the tumor was unresectable. Surgery was limited to a biopsy in six children. All patients received different combinations of chemotherapy, including vincristine (VCR), actinomycin D (Act-D), cyclophosphamide (Cyclo), adriamycin (Adria), bleomycin (Bleo), cis-platinum (CDDP), vinblastine (VBL), and VP-16. Of the nine patients, one was lost to follow-up while in remission, five died, one was lost to follow-up, and three are alive and disease-free at 15, 55, and 67 months from diagnosis. This review demonstrates an unusual preponderance of the extragonadal form of endodermal sinus tumor among our patients.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1989

Purification of an Escherichia coli serogroup O157:H7 verotoxin and its detection in North American hemorrhagic colitis isolates.

Verotoxin (VT), which is immunologically unrelated to VT1 (Shiga-like toxin I), was purified from the culture filtrate of Escherichia coli hemorrhagic colitis serogroup O157:H7 strain 3657 by copper ion chelate affinity chromatography followed by anion-exchange chromatography. The isoelectric point by sucrose density gradient isoelectric focusing was 5.0, the molecular weight by gel filtration on Superose 12 was about 60,000, and the 50% cytopathic dose for Vero cells was about 1 pg. This toxin was found by immunological methods to be the predominant VT in E. coli O157 isolates associated with illness in North America, with 38 of 42 strains tested producing this toxin, 20 in combination with VT1. VT from strain 3657 is immunologically identical to the described Shiga-like toxin II (VT2) of E. coli strains (from the United States) K-12(pEB1) and C600(933W) but only partially related to VT of strain E32511 (from the United Kingdom), the first to be named VT2.

Animals↗
PubMed1989

Classical pituitary apoplexy presentation and a follow-up of 13 patients.

Thirteen patients who presented with signs and symptoms of pituitary disease gave a history of classical pituitary apoplexy. Six presented with acute symptoms and in 7 the history antedated the admission by a mean of 887 days (range 365-2,190 days). All patients had an enlarged eroded sella. CT scans revealed a bleed in the tumor in 11 (histologically confirmed in all 8 patients operated), evidence of residual tumor in 1 and an empty sella (ES) in 1 patient. Hypopituitarism was present in 9, 4 were endocrinologically normal, 8 had visual problems requiring decompressive surgery and radiotherapy (RT) was given to 7 patients. They were subsequently followed for a median period of 730 days (range 365-3,385 days). During this time an empty sella developed in 5, 2 of whom had no surgery or RT; 4 remained endocrinologically normal, and a second hemorrhage occurred in 2 patients. Histological evidence of previous bleeds was noted in 6 of the 8 patients treated surgically. We conclude that apoplexy (1) may produce complete or partial tumor destruction with or without preservation of endocrine function; (2) recurrent, often silent, bleeding into a pituitary tumor appears to be a common event; (3) RT should be withheld unless recurrent tumor is documented (since at least 2 patients in this study have experienced spontaneous resolution of the tumor); and (4) the presence of an enlarged eroded fossa with an ES is reasonable presumptive evidence of an infarction of a pre-existing pituitary tumor.

Adult↗
PubMed1989

Sustained bundle branch reentry as a mechanism of clinical tachycardia.

The incidence of sustained bundle branch reentrant (BBR) tachycardia as a clinical or induced arrhythmia or both continues to be underreported. At our institution, BBR has been the underlying mechanism of sustained monomorphic ventricular tachycardia in approximately 6% of patients, whereas mechanisms unrelated to BBR were the cause in the rest. Data gathered from 20 consecutive patients showed electrophysiologic characteristics that suggest this possibility. These include induction of sustained monomorphic tachycardia with typical left or right bundle branch block morphology or both and atrioventricular dissociation or ventriculoatrial block. On intracardiac electrograms, all previously published criteria for BBR were fulfilled, and in addition, whenever there was a change in the cycle length of tachycardia, the His to His cycle length variation produced similar changes in ventricular activation during subsequent complexes with no relation to the preceding ventricular activation cycles. Compared with patients with ventricular tachycardia due to mechanisms unrelated to BBR, patients with BBR had frequent combination of nonspecific intraventricular conduction defects and prolonged HV intervals (100% vs. 11%, p less than 0.001). When this combination was associated with a tachycardia showing a left bundle branch block pattern, BBR accounted for the majority compared with mechanisms unrelated to BBR (73% vs. 27%, p less than 0.01). The above finding in patients with dilated cardiomyopathy should raise the suspicion of sustained BBR because dilated cardiomyopathy was observed in 95% of the patients with BBR. Twelve of the 20 patients were treated with antiarrhythmic agents, and the other eight were managed by selective catheter ablation of the right bundle branch with electrical energy. Our data suggest that sustained BBR is not an uncommon mechanism of tachycardia; it can be induced readily in the laboratory and is amendable to catheter ablation by the very nature of its circuit. The clinical and electrophysiologic features outlined in this study should enable one to correctly diagnose this important arrhythmia.

Adult↗
PubMed1989

Electrophysiologic spectrum of concealed intranodal conduction during atrial rate acceleration in a model of 2:1 atrioventricular block.

Concealed anterograde penetration of the atrioventricular (AV) node has been used to explain a wide variety of electrocardiographic findings. The effects of atrial rate acceleration on this phenomenon remain undefined. To examine the dynamic interrelations between conducted and nonconducted beats at different atrial rates, a unique atrial pacing protocol of functional 2:1 AV block was used in 10 patients. The pacing protocol involved abrupt transitions from 2:1 to 1:1 AV conduction and enabled quantification of conduction delay produced by nonpropagated impulses over extremes of atrial rate. Stable 2:1 AV conduction was maintained over a mean range of atrial paced cycle lengths of 289 +/- 29.6 to 223 +/- 33.0 msec, respectively. The mean AV conduction time during 2:1 and corresponding 1:1 drives at the longest atrial paced rates were 169 +/- 33.5 and 136.5 +/- 26.9 msec, respectively--revealing a significant effect of nonpropagated impulses on subsequent conduction. Surprisingly, at the shortest atrial paced rates, the mean AV conduction times were 191.5 +/- 31.8 and 161.0 +/- 23.3 msec, respectively. The lack of significant changes in conduction time between 2:1 and 1:1 drives at the extremes of atrial rate (32.5 vs. 30 msec, p = NS) suggests that the effect of concealed conduction is "fixed" and independent of rate. Clinical implications and postulated electrophysiologic mechanisms are discussed.

Adult↗