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Biomedical subjects

S Bharati

Publications and source records attributed to S Bharati.

At least 73 records · Page 4Linked to original sources
PubMed1989

Small aortic valve annulus in children with fixed subaortic stenosis.

Twenty-one hearts with fixed subaortic stenosis (FSAS) were examined pathologically. Thirty children with no hemodynamically significant heart disease, 31 children with valvar aortic stenosis, and 25 children with FSAS were studied by echo- and angiocardiography. The following conclusions were drawn: (1) Patients with FSAS often have abnormal aortic valve leaflets as well as small aortic valve annulus. (2) A small aortic annulus/descending aorta ratio is probably present at birth, and may decrease with increasing age. (3) In some patients with FSAS the aortic valve annulus is too small for simple resection of the fibroelastic tissue. A Konno operation is needed for these patients. (4) M-mode echocardiography has not been useful in identifying abnormally small aortic valve annulus in FSAS patients.

Adolescent↗
PubMed1989

Catheter ablation of the ventricular septum with radiofrequency energy.

The safety and feasibility of performing catheter ablation of the ventricular septum with radiofrequency energy was assessed in a closed-chest canine model. Radiofrequency energy (750 kHz) was delivered in a bipolar manner via the distal electrodes of two quadripolar catheters positioned across the ventricular septum in 10 dogs at two sites. Each site received from 159 to 823 joules of delivered energy over one to three applications. Four additional dogs underwent unipolar radiofrequency ablation with 331 to 767 joules of delivered energy to each septal site. No significant acute or latent arrhythmias were noted. Dogs were killed at 1 day, and at 1, 2, and 4 weeks after the procedure. Out of a possible 40 potential ablation sites on each side of the septum after bipolar ablation, 21 (53%) discrete endocardial lesions were identified, ranging in size from 4 x 3 x 1.5 to 10 x 8 x 4 mm. When 352 joules or more delivered energy was applied per site, lesions were located at 18 of 28 (64%) possible sites. After unipolar radiofrequency ablation, similarly sized lesions were identified at 15 of 16 (94%) ablation sites. Histologic examination demonstrated well-delineated round or ovoid-shaped lesions with microscopic thrombi overlying two lesions. In conclusion, catheter ablation of the ventricular septum with radiofrequency energy appears capable of safely producing discrete areas of necrosis and may provide an alternative to direct current (DC) energy for catheter ablation of ventricular tachycardia originating from the septum.

Animals↗
PubMed1989

Catheter ablation of accessory pathways using radiofrequency energy in the canine coronary sinus.

Ablation of a left-sided accessory pathway with high energy direct-current shocks delivered by an electrode catheter in the coronary sinus is associated with the risk of coronary sinus rupture. The safety and effectiveness of closed chest catheter desiccation in the coronary sinus with use of radiofrequency energy was studied. Radiofrequency energy (174 +/- 74 J) was applied between the distal electrode of a standard electrode catheter placed 3 to 6 cm inside the coronary sinus and a large posterior chest wall patch in 16 dogs. No arrhythmias or hemodynamic changes were observed. Three dogs were killed approximately 1 h after ablation and 13 after 2 to 4 weeks. Lesions in the atrioventricular (AV) sulcus were observed in 14 of 16 dogs. Lesions were 11.6 +/- 6 mm in length, 4.3 +/- 2.3 mm in width and 2.8 +/- 1.4 mm in depth. Microscopic examination showed well circumscribed areas of necrosis and fibrosis in the fat of the AV sulcus. The media and intima of the circumflex coronary artery were not involved nor was the endocardium or mitral apparatus damaged in any dog. Coronary sinus thrombus was present in 3 of 16 dogs. Large amounts of radiofrequency energy can be safely applied to the coronary sinus. The size and location of the lesions produced suggest that this technique may be useful for the interruption of left-sided accessory AV connections in humans.

Animals↗
PubMed1989

Histopathologic changes in the heart including the conduction system after catheter ablation.

The pathology of the heart, including that of the conduction system, after various catheter techniques used to ablate the various parts of the conduction system and the myocardium, were examined histologically by serial sections. The experiments were conducted on canines. The conduction system studies included the approaches to the AV node, the AV node, the AV bundle and bundle branches, as well as, the central fibrous body, the tricuspid, mitral and aortic valves. The methods of ablation were DC shock, laser and radio frequency energy. Production of the complete AV block clinically was associated with fibrosis with or without cartilage formation of the approaches to the AV node, the AV node, the bundle and the beginning of the bundle branches in most cases. On the other hand, creation of first degree AV block was associated with fibrotic changes in the approaches to the AV node and the AV node, and second degree block with more changes to the AV node. Coronary sinus ablation resulted in necrosis and fibrosis of the coronary sinus wall with occasional thrombosis of the coronary sinus. The adjacent atrial and/or the ventricular myocardium also showed fibrosis. Likewise, ventricular septal ablation was associated with focal areas of fibrosis of the myocardium. The conduction system was intact in both of the above experiments. In one human where complete AV block was created to manage intractable atrial fibrillation, the AV node, the bundle, and the bundle branches were fibrosed. In addition, there was a fibrosed atrio-Hisian connection and the patient died suddenly six weeks after the ablative procedure. The surrounding structures close to the vicinity of the conduction system, such as the aortic, tricuspid, mitral valve, the central fibrous body, and the summit ventricular septum are involved to a varying degree. In summary, (1) Whatever the method of ablation may be, the end result was fibrosis with or without cartilage formation of the ablative area. (2) Congenital anomalies of the conduction system such as an atrio-Hisian connection may remain elusive for ablative methods, and arrhythmias may persist and may cause sudden death in some cases.

Animals↗
PubMed1989

Chronic incomplete atrioventricular block induced by radiofrequency catheter ablation.

To determine if catheter ablation of the atrioventricular (AV) junction with radiofrequency energy can induce chronic incomplete (first- and second-degree) AV block to avoid the need for a permanent pacemaker, 20 closed-chest dogs were studied. Group 1 (10 dogs) received radiofrequency energy (750 kHz) with a fixed power setting (5 or 10 W) while increasing the pulse duration from 10 to 50 seconds for each application. Group 2 (10 dogs) received energy with a fixed pulse duration (20 or 30 seconds) while increasing the power setting from 5 to 10 W or from 10 to 20 W during each energy delivery. Radiofrequency energy was delivered between a chest-patch electrode and the distal electrode of a regular 7F tripolar His bundle catheter. For each application, the energy delivery was interrupted when 1) the PR interval prolonged (greater than 50%) or 2) second-degree or complete AV block occurred and persisted up to 5 seconds. The ablation procedure ended when there was 1) persistent PR prolongation (greater than 50%) or persistent second-degree AV block (lasting greater than 30 minutes) after ablation, 2) occurrence of two consecutive transient (less than 1 minute) complete AV blocks after each energy delivery, or 3) complete AV block (lasting greater than 2 minutes) after ablation. Of seven dogs in group 1 and five dogs in group 2 in which incomplete AV block was achieved 1 hour after the procedure, six in group 1 and five in group 2 remained in incomplete AV block 2-3 months after ablation. One dog in group 1 progressed into complete AV block. Of the remaining three dogs in group 1 and five dogs in group 2 in which complete AV block was initially achieved 1 hour after ablation, two in group 1 and four in group 2 continued to have complete AV block, whereas one in each group had AV conduction returned to incomplete at 1-2 months of follow-up. Thus, a total of 13 dogs had chronic incomplete AV block induced by radiofrequency catheter ablation. Pathologic examination of the conduction system in two dogs with first-degree AV block, two dogs with second-degree AV block, and one dog with complete AV block showed discrete scars involving the approaches to the AV node and the AV node itself. It is concluded that, in most dogs studied, chronic incomplete AV block could be achieved by careful titration of the dosage of radiofrequency energy and by regulation of the ablation end points.

Animals↗
PubMed1989

Conduction system in children with acquired immunodeficiency syndrome.

Six children died of acquired immunodeficiency syndrome (AIDS), four of them females, ages 7 months, 13 months, 2 years 8 months, and 4 years; and two of them males, aged 2 1/2 and 7 years. They were born to IV drug-addicted parents. The conduction system (CS) and the entire heart were studied by serial section. In all cases the heart was hypertrophied and enlarged; one had total thrombotic occlusion of the right coronary artery with extensive infarction of the ventricular septum. Vascular changes also were found in all hearts, involving small arteries, arterioles, and venules. In the arteries, they involved the intima, media, and adventitia, and perivascular areas in a degenerative and inflammatory process. The elastic tissue was especially affected. A nonspecific myocarditis was present in four cases and epicarditis in all. Changes in the summit of the ventricular septum were present in four cases, consisting of increased fibrosis and arteriolosclerosis. The CS changes varied in location, showing either vasculitis, myocarditis, or fragmentation of the bundle with lobulation and fibrosis. The changes in the conduction system were not as severe as the changes in the surrounding myocardium. In one case the ECG was abnormal, showing left hemiblock. This corresponded to the finding of fibrosis, vacuolization of cells, and space formation in the left bundle branch.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Selective transepicardial ablation in the immature canine myocardium. A more precise method.

The numerous surgical and transcatheter ablation methods widely applicable to the adult heart have had limited use and efficacy in the immature myocardium. This study introduces a more precise modification of the transepicardial approach to ablation, applicable to the immature heart, by combining selective mapping and simultaneous ablation techniques. To determine the specificity of this method, we attempted His bundle and sinus node ablations in 14 beagle puppies (aged 2 to 4 months). After a thoracotomy, a custom bipolar needle mapping/ablation probe, attached to a standard electrophysiologic recorder, was applied along the aortoatrial and atrial-superior vena caval junctions to record maximal epicardial His bundle and sinus node impulses, respectively. Complete ablation was achieved by the single injection of 10% formalin specifically into the desired target region of the conduction system after the probe was advanced into the myocardium proper. Ventricular pacing was then instituted, the thoracotomy closed, and the animals allowed to recover. After 4 months' observation, bidirectional complete atrioventricular block persisted. High right atrial electrical activity was absent in the animals that underwent sinus node ablation. Programmed stimulation failed to induce any arrhythmias. Histologic study demonstrated selective His bundle and sinus node destruction with minimal involvement of surrounding tissue. This study demonstrates a reproducible transepicardial approach to precise ablation in the immature heart.

Aging↗
PubMed1988

The echo-transponder electrode catheter: a new method for mapping the left ventricle.

The ability to locate catheter position in the left ventricle with respect to endocardial landmarks might enhance the accuracy of ventricular tachycardia mapping. An echo-transponder system (Telectronics, Inc.) was compared with biplane fluoroscopy for left ventricular endocardial mapping. A 6F electrode catheter was modified with the addition of a piezoelectric crystal 5 mm from the tip. This crystal was connected to a transponder that received and transmitted ultrasound, resulting in a discrete artifact on the two-dimensional echocardiographic image corresponding to the position of the catheter tip. Catheters were introduced percutaneously into the left ventricle of nine anesthetized dogs. Two-dimensional echo-transponder and biplane fluoroscopic images were recorded on videotape with the catheter at multiple endocardial sites. Catheter location was marked by delivering radiofrequency current to the distal electrode, creating a small endocardial lesion. Catheter location by echo-transponder and by fluoroscopy were compared with lesion location without knowledge of other data. Location by echo-transponder was 8.7 +/- 5.1 mm from the center of the radiofrequency lesion versus 14 + 7.8 mm by fluoroscopy (n = 15, p = 0.023). Echo-transponder localization is more precise than is biplane fluoroscopy and may enhance the accuracy of left ventricular electrophysiologic mapping.

Animals↗
PubMed1988

Short- and long-term effects of transcatheter ablation of the coronary sinus by radiofrequency energy.

Catheter ablation of left-sided atrioventricular accessory pathways through the coronary sinus by direct-current shock may be complicated by rupture and thrombosis of the coronary sinus and injury to the coronary arteries. This study examined short and long-term effects of radiofrequency catheter ablation of the coronary sinus in 20 closed-chest dogs to determine whether this technique is feasible for potential interruption of left-sided accessory pathways. Single-pulsed radiofrequency energy (750 kHz, 85-293 J) was delivered to three sites in the distal and middle coronary sinus between the distal (1) or the proximal electrodes (2 or 3) of a standard 6 French quadripolar catheter and a chest-wall patch electrode. Single-pulsed radiofrequency energy (78-293 J) was also applied to two sites near the ostium of the coronary sinus with the proximal (4) or the distal (1) electrode of the same catheter. Coronary artery and levophase coronary sinus angiograms obtained before and immediately after ablation, as well as before killing, showed intact vascular structures in all dogs. Right atrial, pulmonary arterial, and aortic pressures measured in three dogs did not change significantly at the time of energy delivery. No significant changes were found in atrioventricular nodal refractoriness and conduction. None of the dogs had significant rhythm disturbances during and after ablation as evaluated by ambulatory electrocardiographic monitoring and periodic rhythm strips at follow-up. Ten dogs were killed 1-7 days after ablation, three dogs were killed at 4 weeks, three dogs at 6 weeks, two dogs at 8 weeks, and two dogs at 12 weeks. Discrete lesions ranging in size from 3 x 3 to 8 x 10 mm2 in surface area and 0.5-4.5 mm in depth were found in the coronary sinus with most of the lesions extending to the left atrial and left ventricular myocardium. There was neither rupture of the coronary sinus nor occlusion of the coronary arteries. Mural thrombus was found in the coronary sinus on five acute lesions in two dogs, but none was noted on the chronic lesions, which was characterized by chronic granulation tissue and fibrosis. Two dogs in the study during chronic conditions had damage to branches of the underlying coronary artery that showed necrotizing arteritis and arterial sclerosis. Conduction system studies in four dogs showed some chronic inflammatory and fibrotic changes. Similar discrete lesions were found in situ in the coronary sinus of four postmortem human hearts with radiofrequency catheter ablation.(ABSTRACT TRUNCATED AT 400 WORDS)

Angiography↗
PubMed1988

Conduction system in a trained jogger with sudden death.

A 47-year-old extremely active, entirely asymptomatic trained jogger was found dead in bed. He was known to have had sinus bradycardia with first-degree atrioventricular block for eight years and a type 1 second-degree block five years prior to death. A permanent pacemaker had been inserted, and apparently the patient was then in good health and maintained his jogging program until he died suddenly. The conduction system revealed an atrioventricular node situated more to the left of the atrial septum than usual, which made tenuous connection with the surrounding atria due to marked fatty infiltration. The atrioventricular node as it joined the left-sided His bundle revealed fatty metamorphosis, fibrosis, disarray of myocardial fibers, and mononuclear cell infiltration. The right bundle branch was intramyocardial and fibrosed throughout. Increased aging changes of the left side of the septum with arteriolosclerosis and patchy fibrosis were present. This is the first case in which the atrioventricular node was more to the left side of the atrial septum with fatty separation of the node from the surrounding atrial musculature, with myocardial disarray of the nodal-His bundle junction. Although congenital abnormality of the conduction system may remain silent without symptoms for a long time, it should be kept in mind that sudden death may occur sooner or later in some susceptible individuals.

Atrioventricular Node↗
PubMed1988

Conduction system in sudden unexpected death a considerable time after repair of atrial septal defect.

The cause of sudden death in young people with congenital heart disease, months or years postoperatively following total surgical correction, is today unknown despite complete autopsy. This is a study of the conduction system in four cases of atrial septal defect of the fossa ovalis type (secundum) who died suddenly several months to years following surgical repair and who were living a normal life. The study suggests that changes in the sinoatrial node and its approaches produced by surgery aided by a pulling effect of a floppy mitral valve on the central fibrous body and hence, on the conduction system, and the unknown familial genetic arrhythmic effect on the conduction system contributed to the sudden death of these patients.

Adolescent↗
PubMed1988

Familial sudden death. Report of a case and review of the literature.

A 15 1/2-year-old boy died suddenly while swimming. He had a family history of sudden death involving three consecutive generations, including a brother. The patient had a history of exercise-related syncope, for which he was being treated with nadolol. Autopsy showed enlarged heart, normal coronary arteries, right ventricular septal hypertrophy, quadricuspid pulmonary valve, accessory tricuspid valve, and a moderately elongated and thickened mitral valve. Conduction system revealed that the penetrating bundle was pushed to the left side of the summit of the ventricular septum by the right ventricular septal hypertrophy; it was lobulated and showed fatty-fibrous changes. These findings extended throughout the beginning of the bundle branches. We conclude that in this patient with familial sudden death and normal QT interval, the abnormal right ventricular septal hypertrophy altered the course and produced degenerative changes in the conduction system, which may have caused sudden death.

Adolescent↗
PubMed1987

Horizontal ventricular septum with dextroversion: hearts with and without aortic atresia.

Two hearts with horizontal ventricular septum, dextroversion (situs solitus), ventricular septal defects, and malaligned great vessels are reported. One of the hearts had aortic atresia and the infant died; the other patient had a Fontan-type physiologic correction. Reviewing the literature, the following conclusions are drawn: (a) Hearts with horizontal ventricular septum and those with criss-cross atrioventricular connections may be the result of different degrees of rotation of the ventricular muscle mass. This rotation is not likely to be postseptational but preseptational. (b) Only those hearts with a complete 180 degrees rotation should be called criss-cross hearts. (c) Partial rotation results in a horizontal septum such that the right ventricle is invariably superior, regardless of atrioventricular concordance or discordance, situs solitus or inversus, or dextroversion. (d) Physiologic surgical correction is often possible but has to be tailored to the details of each heart.

Aorta↗