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Biomedical subjects

M Akhtar

Publications and source records attributed to M Akhtar.

At least 307 records · Page 17Linked to original sources
PubMed1988

Efficacy of cryosurgery alone for refractory monomorphic sustained ventricular tachycardia due to inferior wall infarction.

The efficacy of cryosurgery alone was evaluated in 15 patients with refractory monomorphic sustained ventricular tachycardias related to inferior wall infarction. Patients were 64 +/- 9 (SD) years old and had a mean left ventricular ejection fraction of 39.2 +/- 11.2%. Thirty different tachycardias were mapped with the origin localized to the septum or inferior wall in 20 (67%), near the mitral valve anulus in 6 (20%) and at the base of the posterior papillary muscle in 4 (13%) tachycardias. Endocardial cryoablation of these sites was performed with 6 to 13 (mean 9.2 +/- 1.8) cryolesions per heart. No mitral valve replacement was performed. There was one postoperative death as a result of sepsis. Cryoablation abolished inducible ventricular tachycardia in 11 patients. Of the other three patients, the tachycardia in two was controlled with a single antiarrhythmic agent that had previously failed to suppress inducible ventricular tachycardia. Thus, clinical success was obtained in 13 (93%) of 14 patients. The remaining patient received an automatic implantable cardioverter defibrillator. Ejection fraction remained unchanged or improved after surgery in 14 patients (93%). There have been no late deaths, recurrence of sustained ventricular tachycardia or significant mitral regurgitation during a mean follow-up period of 19 +/- 7 months. These results compare quite favorably with those previously reported for subendocardial resection alone, and indicate that cryosurgery is highly effective, does not result in deterioration of left ventricular function and preserves mitral valve competence when cryoablation of the posterior papillary muscle is necessary.

Aged↗
PubMed1988

Kaposi's sarcoma in cyclosporine-induced gingival hyperplasia.

In the cases presented in this report, Kaposi's sarcoma developed in the gingiva of two patients with cyclosporine-induced gingival hyperplasia. The tumor was clinically inapparent, and was diagnosed unexpectedly following biopsy of the hypertrophied gingiva. This unusual presentation has not been reported previously.

Adult↗
PubMed1988

Membranoproliferative glomerulonephritis in a patient with primary Sjögren's syndrome. Report of a case with review of the literature.

Glomerulonephritis complicating primary Sjögren's syndrome is extremely rare, with only 3 cases of membranoproliferative glomerulonephritis reported in the literature. We report on a 55-year-old woman with a long-standing history of dryness of the mouth and eyes who was found to have nephrotic syndrome. Extensive investigations indicated primary Sjögren's syndrome. Kidney biopsy revealed a membranoproliferative glomerulonephritis. Treatment with prednisone and cyclophosphamide resulted in complete remission of nephrotic syndrome. The pathogenesis of glomerulonephritis appears to be due to deposition of circulating immune complexes.

Female↗
PubMed1988

Atriofascicular connection or a nodoventricular Mahaim fiber? Electrophysiologic elucidation of the pathway and associated reentrant circuit.

Accessory pathways showing decremental properties and inserting into the right ventricle have been frequently described as "nodoventricular" or Mahaim pathways. However, conclusive evidence for a nodal origination of such pathways is lacking. The patient in this study had characteristics typical of such a pathway. Antegradely, the pathway showed decremental, nodelike conduction properties. With the aid of right bundle branch recordings, the pathway was demonstrated to insert directly into the right bundle branch. Atrioventricular reciprocating tachycardia could be readily initiated by atrial or ventricular pacing. The QRS morphology was normal during sinus rhythm and demonstrated a left bundle branch block pattern with normal axis during tachycardia. The reentrant circuit involved antegrade conduction over the accessory pathway and retrograde conduction via the bundle branches, His bundle, and the atrioventricular node. More significantly, late atrial stimuli delivered during tachycardia could preexcite the ventricle via the accessory pathway despite their inability to enter the atrioventricular node. Thus, the upper "turn around" of the reentrant circuit involved atrial tissue and the accessory pathway originated directly from the right atrium independent of the atrioventricular node. In view of these new findings and other recent observations during surgical resection of similar pathways, a reassessment of previous descriptions of "nodoventricular" fibers may be necessary. Many of these pathways may actually represent atriofascicular or atrioventricular connections with decremental properties.

Adolescent↗
PubMed1988

Transcatheter electrical ablation of right bundle branch. A method of treating macroreentrant ventricular tachycardia attributed to bundle branch reentry.

The present study describes the clinical and electrophysiological characteristics of sustained bundle branch reentrant ventricular tachycardia treated with electrical ablation of the right bundle branch. Seven patients presented with syncopal episodes, and six of the seven had documented episodes of ventricular tachycardia. All patients had depressed left ventricular ejection fraction with cardiomegaly. Six of the seven had dilated cardiomyopathy in the absence of significant coronary disease. Twelve-lead electrocardiograms in all seven patients during sinus rhythm were remarkably similar; six demonstrated intraventricular conduction defect resembling left bundle branch block, and one showed left anterior fascicular block. All patients showed prolonged His-to-ventricle intervals during sinus rhythm. Sustained ventricular tachycardia (with atrioventricular dissociation) because of bundle branch reentry was induced in all patients during baseline electrophysiological study. The His-to-ventricle intervals during tachycardia were similar to those seen during sinus rhythm. Electrical ablation of the right bundle branch was accomplished in each patient with delivery of two electrical shocks (170-310 J) through electrode catheters. Right bundle branch block developed on their surface electrocardiogram immediately after the ablation. Follow-up electrophysiological studies showed no inducible ventricular tachycardia. Clinical follow-up showed no recurrence of syncope or ventricular tachycardia. From the data presented, the following can be concluded. First, right bundle branch ablation is a safe and promising means of treating ventricular tachycardia because of bundle branch reentry and can obviate the need for antiarrhythmic drug therapy and its frequent undesirable side effects. Second, there are common clinical and electrophysiological characteristics that are frequently seen in patients with this tachycardia, and the recognition of these common characteristics should alert the physician to a bundle branch reentrant mechanism of ventricular tachycardia.

Aged↗
PubMed1988

Modulation of conduction and refractoriness in atrioventricular junctional reentrant circuit. Effect on reentry initiated by atrial extrastimulus.

The importance of activation sequence of an atrioventricular junctional reentrant (AVJRe) circuit, before delivery of an extrastimulus, has received little attention in studies concerned with clinical tachycardias. In this study a change in activation sequence was accomplished using bidirectional activation (V-A sequential pacing) during the basic drive (V1A1-V1A1). It was noted that, compared with an atrial extrastimulus (A2) after an atrial drive (A1-A1), earlier activation (by V1 impulse of the V1A1-V1A1 drive) consistently improved conduction, or decreased refractoriness, or both, in the anterograde as well as the retrograde pathway of the AVJRe circuit. In all patients, five with AV nodal reentry and six with Wolff-Parkinson-White syndrome, reentrant tachycardia could be prevented during V-A sequential pacing. In four of eleven patients, reentry was prevented despite achieving the so-called critical atrioventricular nodal delays that had previously caused reentry during control study. This finding suggested that conduction delay necessary for reentry was related to the site of block, which in turn was affected by V-A sequential pacing. We concluded that changing the activation sequence during basic drive modulates conduction and refractoriness in AVJRe circuits, and allows the study of a wide range of electrophysical factors that prevent or permit reentry.

Adult↗
PubMed1988

Behavior of postextrasystolic His-Purkinje system refractoriness after multiple premature beats.

Although the steady-state refractoriness of the human His-Purkinje system has been shown to be directly related to the cycle length of pacing, the effect that a varying number of premature beats would have on His-Purkinje system refractoriness of the first postextrasystolic beat has not been described. These effects were systematically investigated in 10 patients with normal intraventricular conduction. The His-Purkinje system relative refractory period (HPS-RRP) of the postextrasystolic beat and that of a comparable constant cycle length ventricular drive were measured by the ventricular extrastimulus technique. Results were as follows: the HPS-RRP of the postextrasystolic beat after one premature beat was longer than the HPS-RRP during a comparable constant ventricular drive. However, with the addition of each successive premature beat, the HPS-RRP of the postextrasystolic beat alternated between lower and higher values, in a manner dependent on whether there was an odd or even number of premature beats. In contrast, ventricular refractoriness of the postextrasystolic beats behaved in a cumulative manner, decreasing progressively with the addition of each premature beat.

Bundle of His↗
PubMed1988

Mesangio-proliferative glomerulonephritis associated with Kimura's disease.

A 16-year-old Saudi male with angiolymphoid hyperplasia and eosinophilia (Kimura's disease) for six years developed nephrotic syndrome. Renal biopsy revealed mesangio-proliferative glomerulonephritis. The patient was treated with prednisone which resulted in complete remission. This case is unique as it occurred in a Saudi patient and responded well to therapy.

Adolescent↗
PubMed1987

On the disulphide bonds of rhodopsins.

Carboxymethylation using 14C- or 3H-labelled iodoacetic acid has been used to identify the cysteine residues in bovine rhodopsin involved in the formation of the two intramolecular disulphide bridges. Iodo[2-14C]acetic acid was used to modify 5.8-5.9 residues of cysteine under non-reducing conditions. After dialysis and reduction of disulphide bridges by 2-mercaptoethanol, iodo[2-3H]acetic acid was employed to covalently modify 3.3-3.6 residues of cysteine. Peptide purification and sequencing has unambiguously shown that cysteine residues 322 and 323 are only carboxymethylated after reduction of disulphide bridges. Indirect evidence presented, now coupled with the earlier finding [Findlay & Pappin (1986) Biochem. J. 238, 625-642] suggests that the other disulphide bridge is formed between cysteine residues 110 and 187. A comparison is made of all the sequences of mammalian rhodopsins and colour pigments and attention is drawn to the fact that whereas Cys-322 and Cys-323 are conserved only in three rhodopsins (bovine, ovine and human), the residues corresponding to Cys-110 and Cys-187 are found in all the visual proteins (from rods as well as human cones).

Amino Acid Sequence↗
PubMed1987

Surgical treatment of bilateral synchronous Wilms' tumors.

Definite progress has been made in the treatment of bilateral Wilms' tumors with marked improvement in the prognosis. This is confirmed in our series of 6 consecutive patients with synchronous tumors. The recent trend toward more conservative surgery, double or triple drug chemotherapy, and avoidance of high-dose radiation therapy has yielded good results.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1987

Effects of abrupt changes in cycle length on atrial refractory periods in man.

While the electrophysiologic effects of sudden changes in cycle length on the His-Purkinje System and ventricular myocardial refractoriness are better known, the behavior of atrial myocardium in this regard is poorly understood. The effects of an abrupt long to short cycle length change (11 patients: group A) and/or short to long cycle length alteration (18 patients: group B) on the atrial effective and functional refractory period were assessed during electrophysiologic studies. The values thus obtained were compared to those observed during the scanning of both constant long and constant short cycle lengths of the same duration. In group A the effective and functional refractory periods of the right atrium measured 250 +/- 38 msec and 296 +/- 31 msec during a constant long cycle length of 709 +/- 80 msec, whereas the same parameters had values of 228 +/- 30 msec and 260 +/- 32 msec, respectively, at a constant short cycle length of 436 +/- 81 msec. With an abrupt change in cycle length from long to short (a change of 273 +/- 75 msec), the effective and functional atrial refractory periods were 225 +/- 29 and 267 +/- 29 msec in that order, and these values closely approximated those seen with a constant short cycle length. Similarly, the two atrial refractory period parameters in group B measured 218 +/- 16 msec and 262 +/- 19 msec during a constant short cycle length of 414 +/- 68 msec and were 236 +/- 17 msec and 284 +/- 21 msec, respectively, at a constant long cycle length of 689 +/- 92 msec.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Pacing, Artificial↗
PubMed1987

Effect of concealed anterograde impulse penetration on retrograde atrioventricular nodal conduction in man.

The manner in which concealed anterograde impulse penetration may affect retrograde atrioventricular nodal conduction was studied systematically in 12 patients with intact ventriculoatrial (VA) conduction. After the last beat of a basic atrial drive (A1), an extrastimulus (A2) was introduced 20 msec inside the effective refractory period of the atrioventricular node. A ventricular extrastimulus (Vp) was then introduced at a progressively shorter A1Vp coupling interval both in the presence (method I) and absence (method II) of A2. In two patients, Vp was never conducted retrogradely to the atria with method I despite the presence of VA conduction during method II. In the remaining 10 patients, the VpAp interval was longer with method I vs method II; moreover, retrograde block of Vp ultimately occurred at a mean A2Vp coupling interval of 359 +/- 153 msec (range 190 to 540 msec) during method I despite the persistence of VA conduction during method II at comparable A1Vp coupling intervals. Before onset of retrograde block in method I, the VpAp curve took one of the following three forms: (1) crescendo, a progressively increasing VpAp interval; (2) flat, a constant VpAp interval, (four cases); or (3) discontinuous, a marked jump in the VpAp interval before the onset of retrograde block (two cases). Our findings may serve to elucidate some poorly understood electrophysiologic phenomena.

Aged↗
PubMed1987

Electrophysiologic mechanisms of orthodromic tachycardia initiation during ventricular pacing in the Wolff-Parkinson-White syndrome.

Orthodromic tachycardia is the most common arrhythmia in patients with Wolff-Parkinson-White syndrome. It is often initiated during incremental ventricular pacing that requires the onset of retrograde block along the normal pathway (that is, atrioventricular [AV] node-His-Purkinje system) with concomitant retrograde atrial activation by way of the accessory pathway. However, the site of retrograde block, that is, the AV node versus the His-Purkinje system, during incremental ventricular pacing and, hence, the mechanism of orthodromic tachycardia initiation have not been systematically elucidated. The mechanisms of orthodromic tachycardia induction were studied in 17 patients with Wolff-Parkinson-White syndrome using a specially designed pacing protocol. A beat by beat analysis indicated that the retrograde His-Purkinje system block was the most common initiating mechanism of orthodromic tachycardia in 14 of the 17 cases. In two cases, AV node block preceded the onset of orthodromic tachycardia, whereas the data in the remaining case suggested that both mechanisms were operative but at different pacing cycle lengths. The orthodromic tachycardia induction with His-Purkinje system block occurred within the first two cycles in most cases. When orthodromic tachycardia initiation was delayed beyond the first two cycles of the ventricular train it represented either a 2:1 block in the His-Purkinje system; a linking phenomenon in the His-Purkinje system; or a block in the AV node. These data have methodologic, mechanistic and therapeutic implications for patients with the Wolff-Parkinson-White syndrome.

Cardiac Pacing, Artificial↗