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Biomedical subjects

M Akhtar

Publications and source records attributed to M Akhtar.

At least 235 records · Page 13Linked to original sources
PubMed1992

Role of implantable cardioverter defibrillator therapy in the management of high-risk patients.

Cardiovascular mortality from ventricular tachycardia (VT) and ventricular fibrillation (VF) continues to be a major health problem. Several therapeutic approaches are now available to treat patients with known VT/VF. Among the various therapeutic options are antiarrhythmic drugs, catheter or surgical ablation of VT focus, and implantable cardioverter defibrillator (ICD). The overall 2-year cardiovascular mortality is significantly reduced by ICD therapy. The ICD is particularly useful in patients with 1) no inducible but clinical VT/VF, 2) drug refractory VT/VF, and 3) VT/VF in association with left ventricular ejection fraction of less than or equal to 30%. Significant improvements in ICD therapy have already been made; these improvements include tiered antitachycardia therapy, antibradycardia pacing, lower defibrillation threshold, and longer life of generator. Further improvements are expected, including nonthoracotomy approach to defibrillation, pectoral implant, and dual chamber sensing. It is likely that with all of the advances in ICD therapy its acceptance as a therapeutic option will increase.

Costs and Cost Analysis↗
PubMed1991

Unexplained syncope evaluated by electrophysiologic studies and head-up tilt testing.

OBJECTIVE: To determine the clinical characteristics of subgroups of patients with unexplained syncope having electrophysiologic studies and head-up tilt testing and to assess the efficacy of various therapies. DESIGN: Retrospective study. SETTING: Inpatient services of a tertiary referral center. PATIENTS: Eighty-six consecutively referred patients with unexplained syncope. MEASUREMENTS: All patients had electrophysiologic examinations. Patients with negative results subsequently had head-up tilt testing. MAIN RESULTS: Twenty-nine (34%) patients (group 1) had abnormal electrophysiologic results, with sustained monomorphic ventricular tachycardia induced in 72%. Thirty-four (40%) patients (group 2) had syncope provoked by head-up tilt testing. The cause of syncope remained unexplained in 23 (26%) patients (group 3). Structural heart disease was present in 76%, 6%, and 30% of groups 1, 2, and 3, respectively. In group 1, pharmacologic or nonpharmacologic therapy was recommended based on electrophysiologic evaluation. All group 2 patients had negative results on head-up tilt testing while receiving oral beta blockers (27 patients) or disopyramide (7 patients). Group 3 patients did not receive any specific therapy. During a median follow-up period of 18.5 months, syncope recurred in 9 (10%) patients. CONCLUSIONS: The combination of electrophysiologic evaluation and head-up tilt testing can identify the underlying cause of syncope in as many as 74% of patients presenting with unexplained syncope. Therapeutic strategies formulated according to the results of these diagnostic tests appear to prevent syncope effectively in most patients.

Adolescent↗
PubMed1991

Sudden cardiac death: management of high-risk patients.

Sudden cardiac death remains a leading cause of death in the United States, accounting for more than 350,000 deaths each year, and the survival rate of victims remains low. Most survivors face a significant risk for recurrence. The typical substrate is chronic--abnormal myocardium with fibrosis (often from previous myocardial infarction) and left ventricular dysfunction. Acute triggers for sudden cardiac death are primarily electrical, ischemic, metabolic, neurohormonal, and pharmacologic. In most electrocardiographically documented cases of sudden cardiac death, the trigger-substrate interaction appears to result in ventricular tachycardia and fibrillation. After initial resuscitation, survivors need a thorough cardiovascular evaluation, including definition of coronary anatomy, left ventricular function, and wall-motion abnormalities, as well as an electrophysiologic evaluation. An attempt must be made to determine what each survivor's correctable triggers are. Management should address all reversible triggers, such as acute ischemia and electrolyte abnormalities, and should include modifying or correcting the arrhythmogenic substrate. Empiric antiarrhythmic therapy offers no advantage in such modification. Pharmacologic therapy with antiarrhythmic drugs should be guided by an objective therapeutic endpoint, which is best accomplished through the use of programmed ventricular stimulation and serial electrophysiologic studies. Other therapeutic options include surgical suppression of ventricular tachycardia and implantation of a cardioverter defibrillator.

Arrhythmias, Cardiac↗
PubMed1991

'Slow-binding' sixth-ligand inhibitors of cytochrome P-450 aromatase. Studies with 19-thiomethyl- and 19-azido-androstenedione.

The progress curves for the inhibition of aromatase by 19-thiomethylandrostenedione and 19-azidoandrostenedione were found to be non-linear where the extent of inhibition increased with time. Further experiments enabled these compounds to be classified as 'slow-binding' inhibitors of aromatase. The phenomenon was attributed to the formation of an initial E.I complex that rearranged to another species (E.I*) in which the interaction between the enzyme and inhibitor had been maximized, giving rise to tighter binding. When 19-thiomethylandrostenedione was used as the inhibitor the t0.5 (half-time) for the dissociation of E.I* was calculated to be 12.6 min with Ki and Ki* values of 2.4 and 1.4 nM respectively. In the case of 19-azidoandrostenedione, the two separate dissociation constants were not determined, and a single Ki value of 5 nM was obtained. The conclusions drawn from kinetic studies were confirmed by absorption spectrometry, when time-dependent formation of complexes between aromatase and either 19-thiomethylandrostenedione or 19-azidoandrostenedione were observed by the formation of 'Type II' spectra. The two complexes respectively had maxima at 429 and 418 nm. The spectral data suggested that the two inhibitors interact with the haem iron of aromatase, forming hexaco-ordinated species for which structural models are presented.

Androstenedione↗
PubMed1991

Fine-needle aspiration biopsy diagnosis of malignant rhabdoid tumor of the kidney.

A series of six fine-needle aspiration biopsies from three patients with malignant rhabdoid tumor of the kidney is reviewed. The smears revealed round, polygonal, and irregularly shaped cells with large nuclei and prominent nucleoli. Some of the tumor cells contained light pink to purple cytoplasmic inclusions that correlated with the eosinophilic inclusions seen in histopathologic sections and filamentous cytoplasmic aggregates noted on ultrastructural examination. Diagnosis of malignant rhabdoid tumor of the kidney may be suggested from aspiration biopsy smears; however, further confirmation of the diagnosis by histologic or ultrastructural examination is desirable.

Biopsy, Needle↗
PubMed1991

Role of testicular fine-needle aspiration biopsy in the evaluation of male infertility: cytologic and histologic correlation.

A series of testicular fine-needle aspiration biopsy specimens from 272 infertile men with azoospermia were reviewed and categorized according to morphologic patterns. These included active spermatogenesis, 14 (5%); hypospermatogenesis, 106 (39%); Sertoli cells only, 70 (26%); atrophic pattern, 52 (19%); and maturation arrest, 1 (0.36%). In 29 cases (11%) the amount of material was insufficient for evaluation. The histologic and cytologic findings in 52 cases showing spermatogenesis correlated very well in 52 cases for which open testicular biopsy specimens were also available. These findings indicate that fine-needle aspiration biopsy of the testis is a reliable and useful technique for the investigation of patients with azospermia.

Adult↗
PubMed1991

Sensitivity of fine-needle aspiration biopsy in the detection of mycobacterial infections.

A series of 290 fine needle aspiration biopsies (FNABs) processed for mycobacterial cultures are reviewed. The clinicopathologic features in 162 cases were suggestive of tuberculous infection and 86 (53%) of the samples in these cases were culture positive. A comparative histologic and cytologic correlation was carried out in 23 cases. Aspiration smears from caseating granulomas were composed of necrotic debris containing large numbers of polymorphonuclear cells and scattered histiocytes, epithelioid cells, and multinucleated giant cells. In cases of noncaseating granulomas, the smears revealed well-defined aggregates of epithelioid cells without necrotic debris or significant numbers of other inflammatory cells. There was a close correlation between the histologic and cytologic diagnosis of caseating and/or noncaseating granulomatous inflammation.

Biopsy, Needle↗
PubMed1991

Diagnosis of cutaneous leishmaniasis by fine-needle aspiration biopsy: report of a case.

A case of cutaneous leishmaniasis diagnosed by fine-needle aspiration biopsy is presented. The cytologic smears revealed lymphocytes, plasma cells, and macrophages. Large numbers of Leishmania organisms were present within the macrophages and in the intercellular spaces. Part of the material was used for a microbiologic culture, which revealed large numbers of promastigotes. These were studied by light, transmission, and scanning electron microscopy.

Adult↗
PubMed1991

Fine-needle aspiration biopsy of papillary thyroid carcinoma: cytologic, histologic, and ultrastructural correlations.

Aspiration smears from a series of 21 papillary thyroid carcinomas were studied and a number of morphologic features correlated with the histologic and ultrastructural patterns. These included types of papillary structures, metaplastic cells, grooved and lobulated nuclei, optically clear nuclei, intranuclear inclusions, and macrophages. Generally there was a close correlation between histologic and cytologic findings. The numbers of macrophages and metaplastic cells appeared to be exaggerated in aspiration smears as compared with those seen on histologic sections. Optically clear nuclei were not seen on the air-dried cytologic smears. Grooved nuclei were somewhat difficult to recognize in the aspiration smears, although lobulated nuclei were identified easily. We consider the latter to be a significant feature in the diagnosis of papillary carcinoma. Ultrastructurally grooved nuclei showed a deep linear indentation of the nuclear membranes. Lobulated nuclei were characterized by multiple indentations that divided the nucleus into several lobules.

Biopsy↗
PubMed1991

Fine-needle aspiration biopsy (FNAB) diagnosis of testicular involvement in acute lymphoblastic leukemia in children.

A series of 106 fine-needle aspiration biopsy specimens obtained from the testes of children with acute lymphoblastic leukemia was reviewed retrospectively. Involvement by leukemia was seen in 34, there was no evidence of disease in 52, and the cellular sample was inadequate in 20. All aspiration smears, except those with leukemic involvement, showed a variable number of Sertoli cells. Testicular leukemia was diagnosed by the presence of numerous leukemic cells and rare or no Sertoli cells. Fine-needle aspiration biopsy is a simple but effective technique for diagnosing leukemic involvement of the testis in children with acute lymphoblastic leukemia.

Biopsy, Needle↗
PubMed1991

Lipoid pneumonia in infants: a radiological-pathological study.

A series of nine infants, 2-8 months of age, with a history of animal or vegetable fat intake within 10 days after birth, is presented. The infants developed respiratory problems and failure to thrive. Plain films and computed tomography showed areas of consolidation in the medial-posterior parts of the lungs. The areas of consolidation showed three types of changes at computed tomography. Attenuation measurements did not reveal fat. To establish the diagnosis, fine needle aspiration biopsy, tru-cut biopsy and/or open lung biopsy was done in eight infants and bronchopulmonary lavage in one patient. The pathological findings were an intense lymphocytic infiltration with scattered granulomas which contained lipid deposit.

Biopsy, Needle↗
PubMed1991

Echocardiographic demonstration of decreased left ventricular dimensions and vigorous myocardial contraction during syncope induced by head-up tilt.

Two-dimensional echocardiography was performed during a head-up tilt test in 11 control subjects (group I) and 18 patients with recurrent unexplained syncope. In four patients (group II), the head-up tilt test was negative at baseline and after isoproterenol infusion. Syncope was induced during baseline head-up tilt in nine patients (group III) and after isoproterenol challenge in five (group IV). The echocardiographic variables assessed were left ventricular end-systolic and end-diastolic areas and percent fractional shortening. At the end of head-up tilt, end-systolic area decreased by 4.5 +/- 1.3 and 3.0 +/- 1.2 cm2 in groups III and IV, respectively, compared with 0.5 +/- 0.7 and 0.2 +/- 0.1 cm2 in groups I and II, respectively (p less than 0.04). Similarly, end-diastolic area decreased by 5.5 +/- 2.6 cm2 in group III compared with 2.7 +/- 1.9 and 1.75 +/- 0.4 cm2 in group I and II, respectively (p less than 0.04). Additionally, at the end of the baseline study, fractional shortening was significantly greater in group III and group IV (43 +/- 5%) than in groups I and II (p less than 0.01). In conclusion, syncope induced by head-up tilt is associated with vigorous myocardial contraction and a significant decrease in left ventricular end-systolic dimensions. This left ventricular hypercontractility may play an important role in the pathogenesis of syncope induced by head-up tilt.

Adult↗
PubMed1991

Cardiovascular causes of syncope. Identifying and controlling trigger mechanisms.

Syncope usually has a cardiovascular source, so neurologic evaluation has a low diagnostic yield in these patients. Cardiac arrhythmias in persons with or without structural heart disease can produce syncope. Neurocardiogenic dysfunction that results in diminished venous return and hypercontractility is another frequent cause. Postural hypotension or left ventricular outflow obstruction may also be to blame. Careful history taking and physical examination, head-up tilt testing, echocardiography or radionuclide isotope imaging, and electrophysiologic study are often diagnostic. However, syncope remains undiagnosed in some patients, and they may require periodic reassessment. Treatment options are available for most cardiovascular disorders, among them use of pharmacologic agents; catheter, surgical, or radio-frequency modification of certain tachycardias; and permanent pacing.

Cardiac Pacing, Artificial↗
PubMed1991

When is it safe not to replace an implantable cardioverter defibrillator generator?

In most reports on patients receiving implantable cardioverter defibrillators, shocks were received mainly during the first 2 to 3 years. Thus, the question had been raised as to the need for device replacement after 3 or 4 years if no shocks had been received. In order to answer this question, shock experience in 184 patients receiving the implantable cardioverter defibrillator was analyzed. Patients were followed for a mean of 24 +/- 18.7 months. A patient's shock was judged to be appropriate if there was electrocardiographic documentation of sustained ventricular tachyarrhythmia at the time of shock or if it was preceded by sudden onset of presyncopal or syncopal symptoms. The majority of patients had coronary artery disease. In approximately two-thirds of patients, left ventricular ejection fraction was below 40%. One hundred fourteen patients had inducible sustained monomorphic ventricular tachycardia. On follow-up, there were 29 deaths, five of which were sudden. Sixty-eight patients received an appropriate shock during follow-up (37%). Over 90% of these 68 received their first shock within the 2 years after implant. The actuarial risk of receiving an appropriate shock by the fifth year after implant was 69%. Conversely, 31% of patients who survived 5 years had not received an appropriate shock. Hazard analysis indicates that there is a high incidence of first appropriate shock during the year following implant. Subsequently, the incidence dropped to a relatively steady rate with a rise in this rate during the fifth year. This analysis suggested a bimodal distribution of appropriate shocks.(ABSTRACT TRUNCATED AT 250 WORDS)

Actuarial Analysis↗
PubMed1991

Does reception of appropriate shocks from the implantable cardioverter defibrillator affect survival?

The implantable cardioverter defibrillator has become an important therapeutic modality for treatment of life-threatening ventricular tachyarrhythmias. Recent reports have suggested that patients who receive appropriate shocks from this device have an inordinately high overall mortality, and questioned the extent of benefit these patients derive from the implant. This report analyzed the survival among 184 patients who received the implantable cardioverter defibrillator to assess survival differences between patients who received appropriate shocks versus those who did not. At a mean follow-up of 24 +/- 18.7 months, 68 patients received an appropriate shock from their device while 116 did not receive an appropriate shock. Overall survival of the entire population was quite similar to those published by others. There was no significant difference between overall survival of patients who received an appropriate shock versus those who did not. However, there was a statistically significant difference in sudden death mortality. The group of patients that received appropriate shocks included all five sudden deaths. This observation suggested that sudden death in this population was likely due to ventricular tachyarrhythmias rather than strictly bradycardia or asystole. The "benefit" of the device to the entire population was also assessed by estimating survival after receipt of the first appropriate shock. Using this approach, an estimated 10% of patients died without receiving an appropriate shock. In other words, ultimately, 90% of patients were expected to benefit from the device. This survival curve, which initiated only after receipt of the first appropriate shock was fairly similar to those estimated from conventional methods. Therefore, survival after receipt of an appropriate shock was comparable to overall survival and there was no significant difference between survival of patients who received appropriate shocks and those who did not.

Death, Sudden, Cardiac↗
PubMed1991

Maintenance of atrioventricular sequence after His-bundle ablation for paroxysmal supraventricular rhythm disorders: a unique use of the fallback mode in dual chamber pacemakers.

The usual mode of controlling ventricular rate after His-bundle ablation is placement of a ventricular demand rate responsive pacemaker. Atrioventricular synchrony is therefore lost in individuals whose atrial rhythm disturbances are paroxysmal. Thirty-seven His ablations were performed at this institution, since January of 1983, for atrial rhythm disturbances that were not suppressible with medical therapy alone. Of those, ten patients were identified whose atrial rhythm disturbances were intermittent and who would otherwise benefit by having proper atrioventricular sequence during sinus rhythm. These patients underwent placement of a dual chamber pacemaker system having a fallback mode. At a mean follow-up period of 17 +/- 11 months, eight patients continued to maintain proper atrioventricular sequence with ventricular pacing tracking atrial activation during sinus rhythm. Supraventricular tachyarrhythmic attacks were associated with attainment of the programmed upper rate limit at which time the fallback mode was activated and the pacemaker automatically converted to a ventricular demand (VVI) mode. Restoration of normal sinus rhythm was associated with restoration of proper atrioventricular sequence. Two patients have developed chronic atrial fibrillation and their pacemakers continue to function in the fallback mode as VVI devices. In conclusion, intermittent supraventricular tachyarrhythmias which are resistant to drug therapy can be treated with His ablation and dual chamber pacing utilizing special pacemaker features such as the fallback mode.

Bundle of His↗
PubMed1991

Survival in patients with depressed left ventricular function treated by implantable cardioverter defibrillator.

Mortality in patients with cardiovascular disease is generally due to pump failure or lethal ventricular arrhythmias. In patients with ventricular tachycardia (VT) or ventricular fibrillation (VF) and poor left ventricular (LV) function the death rate is particularly high. The overall incidence of premature arrhythmic death rate in patients with poor LV function is not totally clear. Since implantable cardioverter defibrillator (ICD) could prevent arrhythmic death in any population, we proceeded to analyze mortalities in patients with poor LV function who received ICD. Among a total of 200 consecutive patients receiving ICD at our institution, 68 (34%) had LV ejection fraction (LVEF) of less than 30%. Thirty-one of these (45%) experienced appropriate ICD discharges and 17/31 (55%) had multiple shocks. Survival curves in this population revealed a 5 year projected overall survival of 11% whereas an actual survival was 60%. Even those who ultimately died from nonsudden causes, life was prolonged by ICD in a significant number of cases. Based upon these findings it is concluded that ICD has a major impact on survival in patients with poor LV function suggesting that many of these patients die prematurely from arrhythmia causes.

Actuarial Analysis↗