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Biomedical subjects

M Lev

Publications and source records attributed to M Lev.

At least 73 records · Page 4Linked to original sources
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↗
PubMed1988

Warfarin administration reduces synthesis of sulfatides and other sphingolipids in mouse brain.

The modulation of phosphosphingolipid synthesis by vitamin K depletion has been observed in the vitamin K-dependent microorganism, Bacteriodes levii. When cultured briefly without the vitamin, a reduction occurred in the activity of the first enzyme of the sphingolipid pathway, 3-ketodihydrosphingosine synthase. In this report, 16-day-old mice were treated with the vitamin K antagonist, warfarin. Brain microsomes from these animals showed a 19% reduction in synthase activity. Mice treated with warfarin for 2 weeks showed a major reduction in sulfatide level (42%), with a lesser degree or no reduction in levels of gangliosides and cerebrosides. In further experiments, mice were treated with warfarin for 2 weeks and a group was then injected with vitamin K1 (aquamephyton) for 3 days. Enzyme activity returned to a normal level within 2-3 days. Sulfatide levels had increased 33% in the vitamin K-injected group and ganglioside levels also increased, where levels of cerebrosides and sphingomyelin declined. Sulfatide synthesis determined by [35S] sulfate incorporation, showed a 52% increase in incorporation following administration of vitamin K for 3 days. These results suggest a role for vitamin K in the biosynthesis of sulfatides and other sphingolipids in brain. This putative role could be by post-translational protein modification analogous to the role of vitamin K in other systems.

Animals↗
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↗
PubMed1987

Closed chest catheter desiccation of the atrioventricular junction using radiofrequency energy--a new method of catheter ablation.

Closed chest catheter ablation of the atrioventricular (AV) junction has been performed with direct current or laser energy. The effect of 750 kHz radiofrequency energy on ablation of the AV junction was evaluated in 13 dogs. The radiofrequency energy was generated from an electrosurgical generator in the bipolar mode. The radiofrequency output was delivered between two distal electrodes (bipolar ablation) in eight dogs, and between the distal electrode and an external patch electrode (unipolar ablation) in another five dogs at varying power (watts) but with a constant pulse duration of 10 seconds. Complete AV block was achieved in 11 dogs and second degree AV block in 2. During the 4 to 7 day follow-up period, complete AV block persisted in 9 of the 11 dogs with initial complete heart block. The other two had return of AV conduction; one had persistent 2:1 AV block and the other had persistent first degree AV block. Of the two dogs with initial second degree AV block, one developed complete AV block, the other had resumption of 1:1 AV conduction with a normal PR interval. Energy was delivered in 1 to 13 applications per dog. One hundred to 700 J per application was delivered with bipolar ablation and 10 to 100 J with unipolar ablation. There was no damage to the catheter unless the catheter was repeatedly used in excess of 1,500 J of total energy. Ventricular arrhythmias were not observed. Pathologic examination showed well delineated coagulation necrosis at the AV junction without surrounding hemorrhage or mural thrombus. Microscopic findings consisted of necrosis with cell infiltration in the periphery of necrosis. Most injuries involved the AV node, the approaches to the AV node and the penetrating bundle. In conclusion, catheter ablation of the AV junction with radiofrequency energy is safe. It can effectively induce discrete areas of necrosis and produce various degrees of AV block. In addition, ablation by radiofrequency energy has distinct advantages as compared with catheter ablation with direct current or laser energy.

Animals↗
PubMed1987

Electrophysiologic and histologic observations of chronic atrioventricular block induced by closed-chest catheter desiccation with radiofrequency energy.

Direct-current or laser energy has been used to induce atrioventricular (AV) block, but certain complications associated with this type of energy have been reported. We have previously documented that radiofrequency (RF) energy can effectively and safely induce acute AV block in closed-chest dogs during the 4-7 days of follow-up. This study was undertaken to determine if the ablation was permanent and to define the chronic pathology and site of AV block. Complete AV block was successfully achieved in four dogs immediately after ablation with a bipolar "standard" RF output (750 kHz) delivered between the tip electrode of a standard 7F USCI catheter and an external patch electrode on the left lateral chest wall. During 2 months of follow-up, three dogs had persistent complete AV block with a stable escape rhythm; the other had persistent 2:1 AV block. Repeat His bundle recordings were performed at 2 months prior to sacrifice of the dogs. Supra-His AV block was noted in two dogs; His bundle potential could not be recorded in another two. Histologically, the damaged area was well delineated. In all animals, the AV node and, in some dogs, part of the His bundle were completely replaced by granulation tissue and/or cartilage. There was fatty infiltration and also chronic inflammatory cells around the lesions. Neither perforation, hemorrhage nor vacuolation was seen in the adjacent area. Thrombus was not present. It is concluded that RF energy can effectively achieve chronic AV block and produce well-circumscribed pathological lesions.

Animals↗
PubMed1987

Neonatal lupus with congenital atrioventricular block and myocarditis.

This is a case of a child with neonatal lupus and congenital atrioventricular (AV) block, born to a mother with asymptomatic, systemic lupus erythematosus (SLE). The child, despite pacemaker insertion, died of septicemia and myocarditis at the age of three months. Although the association of neonatal lupus with congenital AV block is well-recognized, there are only few pathologic studies of the conduction system reported in the literature. This is such a study in which we emphasize that, due to an altered immune system in the child, septicemia may be the cause of death in some cases.

Female↗
PubMed1987

Low-energy transvenous ablation of the canine atrioventricular conduction system with a suction electrode catheter.

A single suction electrode catheter was used for His bundle electrogram recording. His bundle pacing, and low-energy (20 or 30 J) His bundle ablation in seven dogs. The suction electrode catheter was actively fixed to the atrial endocardium at the His bundle level. Electrophysiologic studies were performed in the control state, immediately after, and late (greater than 40 days) after His bundle ablation and results were correlated with histologic findings in the conduction system. Unipolar His bundle recording and pacing were successfully performed in all dogs with the suction electrode catheter before and after ablation. Complete heart block developed after a single 20 J shock delivered via the suction electrode catheter in all dogs immediately, but reverted to 1:1 atrioventricular conduction with first-degree atrioventricular block in two dogs in which one or two additional shocks (20 or 30 J) produced complete heart block. Mean ablation energy per shock was 22 +/- 4 J. The mean total delivered energy per dog was 31 +/- 20 J. Late electrophysiologic study in all dogs showed persistent complete heart block in five dogs and paroxysmal second-degree or third-degree atrioventricular block in two dogs. Gross examination of the ablation site showed a white plaque above the medial tricuspid leaflet (1.4 to 2.0 cm long and 0.4 to 0.6 cm wide). Microscopically, fibrosis of the penetrating and branching His bundle was seen in all dogs, with minimal atrioventricular node and atrial involvement. Significant proximal right bundle branch fibrosis was observed in the two dogs receiving one or two additional shocks. We conclude that the suction electrode catheter permits repeated His bundle recording, pacing, and ablation with a single catheter. Permanent and safe low-energy ablation of the canine His bundle is feasible. Focal injury localized to the target area in the conduction system can be obtained.

Animals↗
PubMed1986

Congenital abnormalities of the conduction system in sudden death in young adults.

The sudden death of four apparently healthy young people, three men aged 25, 24 and 21 years, respectively, and one woman aged 20 years, was investigated. The heart was of normal size in two and was slightly enlarged in two. The conduction system in all hearts was serially sectioned. In all hearts the His bundle showed loop formation. In two, the branching bundle was left-sided with the right bundle branch intramyocardial. In the other two, the His bundle was markedly fragmented. Two had myocarditis, and three had arteriolosclerosis of the summit of the ventricular septum. These findings suggest the following: autopsy may be otherwise normal or show minimal findings in cases of sudden death in young people, with significant abnormalities seen only in the conduction system. The common denominator in the conduction system may be a congenital abnormality of the His bundle (in two hearts it was fragmented, in two it was left-sided and there was loop formation in all). Acquired changes may be present, such as arteriolosclerosis of the summit of the ventricular septum (three cases), myocarditis (two cases), and fatty infiltration in the atria (all four cases), a congenital abnormality of the His bundle with or without other findings (congenital or acquired) may cause reentrant phenomena or increased automaticity, ventricular arrhythmias and sudden death.

Adult↗
PubMed1986

Long-term follow-up of cardiac rhythm in repaired total anomalous pulmonary venous drainage.

Seven consecutive patients with total anomalous pulmonary venous drainage were operated at the Medical College of Ohio at Toledo and long-term follow-up is reported on their rhythm status. The patients were generally under 3 months of age at operation. All patients are alive at the present time. The median length of follow-up is 4 years. Five of the 7 patients demonstrated ectopic pacemaker activity and 2 exhibited episodes of nodal rhythm as well. In general, these were not apparent on standard screening electrocardiography. There was no correlation between the presence or absence of this arrhythmia and the type of repair. It is concluded that arrhythmias may be present in these patients, but that they are unrelated to the type of surgery performed. The ectopic atrial focus may be of no clinical significance but there is more cause for concern in those patients with nodal rhythm.

Arrhythmias, Cardiac↗
PubMed1986

Histologic changes and arrhythmogenicity after discharge through transseptal catheter electrode.

Ventricular tachycardia commonly arises within the intraventricular septum and successful catheter ablation of septal tachycardia might be enhanced by transseptal electrode placement. We have evaluated the safety of a transseptal ablation procedure. Arrhythmogenicity and histology were examined after high-energy capacitor discharges were delivered to an intracavitary cathode-anode pair placed on opposite sides of the interventricular septum in pentobarbital-anesthetized dogs. After two discharges of 200 or 100 J proved lethal, paired discharges of 30 or 50 J (10 dogs) or a single discharge of 100 J (four dogs) was used to induce 28 lesions. Acute rhythm changes and risk of induction of ventricular tachycardia by programmed stimulation were measures of arrhythmogenicity. Gross and histologic examination of the hearts after 20 min to 28 days allowed characterization of the evolution of lesions. The conduction system in nearby and remote locations was extensively examined in four dogs. Refractory ventricular fibrillation developed with paired shocks at 200 or 100 J. At lower energy levels, acute ventricular fibrillation occurred with 12 of 20 shocks (60%), but defibrillation was consistently achieved. After ablation, no dog had ventricular tachycardia or fibrillation induced with programmed stimulation. Matching anodal and cathodal lesions spanned the septum without perforation in 10 of 16 dogs, and the lesions were of similar histology. Each contained central areas of hemorrhage surrounded by a region of coagulation necrosis merging with normal myocytes peripherally. There was necrosis and edema without inflammation at 20 min, acute inflammatory cell infiltration at 1 to 2 days, and myocyte replacement by granulation tissue after 6 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗