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Abstract
Transcription of eukaryotic genes by RNA polymerase II (Pol II) yields RNA precursors containing introns that must be spliced out and the flanking exons ligated together. Splicing is catalyzed by a dynamic ribonucleoprotein complex called the spliceosome. Recent evidence has shown that a large fraction of splicing occurs cotranscriptionally as the RNA chain is extruded from Pol II at speeds of up to 5 kb/minute. Splicing is more efficient when it is tethered to the transcription elongation complex, and this linkage permits functional coupling of splicing with transcription. We discuss recent progress that has uncovered a network of connections that link splicing to transcript elongation and other cotranscriptional RNA processing events.
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Affiliation(s)
- Hossein Shenasa
- Department of Biochemistry and Molecular Genetics, RNA Bioscience Initiative, University of Colorado School of Medicine, PO Box 6511, Aurora, CO 80045, USA
| | - David L Bentley
- Department of Biochemistry and Molecular Genetics, RNA Bioscience Initiative, University of Colorado School of Medicine, PO Box 6511, Aurora, CO 80045, USA.
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2
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Abstract
Alternative splicing enables higher eukaryotes to expand mRNA diversity from a finite number of genes through highly combinatorial splice site selection mechanisms that are influenced by the sequence of competing splice sites, cis-regulatory elements binding trans-acting factors, the length of exons and introns harbouring alternative splice sites and RNA secondary structures at putative splice junctions. To test the hypothesis that the intron definition or exon definition modes of splice site recognition direct the selection of alternative splice patterns, we created a database of alternative splice site usage (ALTssDB). When alternative splice sites are embedded within short introns (intron definition), the 5' and 3' splice sites closest to each other across the intron preferentially pair, consistent with previous observations. However, when alternative splice sites are embedded within large flanking introns (exon definition), the 5' and 3' splice sites closest to each other across the exon are preferentially selected. Thus, alternative splicing decisions are influenced by the intron and exon definition modes of splice site recognition. The results demonstrate that the spliceosome pairs splice sites that are closest in proximity within the unit of initial splice site selection.
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Affiliation(s)
- Francisco Carranza
- Department of Microbiology and Molecular Genetics, University of California Irvine, Irvine, California, USA
| | - Hossein Shenasa
- Department of Microbiology and Molecular Genetics, University of California Irvine, Irvine, California, USA
| | - Klemens J Hertel
- Department of Microbiology and Molecular Genetics, University of California Irvine, Irvine, California, USA
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Shenasa H, Movassat M, Forouzmand E, Hertel KJ. Allosteric regulation of U1 snRNP by splicing regulatory proteins controls spliceosomal assembly. RNA 2020; 26:1389-1399. [PMID: 32522889 PMCID: PMC7491332 DOI: 10.1261/rna.075135.120] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Accepted: 06/02/2020] [Indexed: 06/01/2023]
Abstract
Alternative splicing is responsible for much of the transcriptomic and proteomic diversity observed in eukaryotes and involves combinatorial regulation by many cis-acting elements and trans-acting factors. SR and hnRNP splicing regulatory proteins often have opposing effects on splicing efficiency depending on where they bind the pre-mRNA relative to the splice site. Position-dependent splicing repression occurs at spliceosomal E-complex, suggesting that U1 snRNP binds but cannot facilitate higher order spliceosomal assembly. To test the hypothesis that the structure of U1 snRNA changes during activation or repression, we developed a method to structure-probe native U1 snRNP in enriched conformations that mimic activated or repressed spliceosomal E-complexes. While the core of U1 snRNA is highly structured, the 5' end of U1 snRNA shows different SHAPE reactivities and psoralen crosslinking efficiencies depending on where splicing regulatory elements are located relative to the 5' splice site. A motif within the 5' splice site binding region of U1 snRNA is more reactive toward SHAPE electrophiles when repressors are bound, suggesting U1 snRNA is bound, but less base-paired. These observations demonstrate that splicing regulators modulate splice site selection allosterically.
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Affiliation(s)
- Hossein Shenasa
- Department of Microbiology and Molecular Genetics, University of California Irvine, Irvine, California 92697, USA
| | - Maliheh Movassat
- Department of Microbiology and Molecular Genetics, University of California Irvine, Irvine, California 92697, USA
| | - Elmira Forouzmand
- Department of Microbiology and Molecular Genetics, University of California Irvine, Irvine, California 92697, USA
| | - Klemens J Hertel
- Department of Microbiology and Molecular Genetics, University of California Irvine, Irvine, California 92697, USA
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Shenasa M, Razavi SM, Shenasa H, Al-Ahmad A. The Ideal Cardiac Mapping System. Card Electrophysiol Clin 2019; 11:739-748. [PMID: 31706480 DOI: 10.1016/j.ccep.2019.08.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Cardiac mapping has witnessed significant and unprecedented progress over more than a century. At present, several mapping/imaging technologies are commercially available, alone or in combination. This article briefly discusses the advantages and limitations (disadvantages) of each technique.
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Affiliation(s)
- Mohammad Shenasa
- Department of Cardiovascular Services, Heart and Rhythm Medical Group, O'Connor Hospital, San Jose, CA 95030, USA.
| | - Seyed-Mostafa Razavi
- Department of Cardiovascular Services, Heart and Rhythm Medical Group, O'Connor Hospital, San Jose, CA 95030, USA
| | - Hossein Shenasa
- Department of Cardiovascular Services, Heart and Rhythm Medical Group, O'Connor Hospital, San Jose, CA 95030, USA
| | - Amin Al-Ahmad
- Texas Cardiac Arrhythmia Institute, 3000 North IH35, Suite 700, Austin, TX 78705, USA
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5
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Shenasa H, Hertel KJ. Combinatorial regulation of alternative splicing. Biochim Biophys Acta Gene Regul Mech 2019; 1862:194392. [PMID: 31276857 DOI: 10.1016/j.bbagrm.2019.06.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 06/21/2019] [Accepted: 06/24/2019] [Indexed: 12/23/2022]
Abstract
The generation of protein coding mRNAs from pre-mRNA is a fundamental biological process that is required for gene expression. Alternative pre-mRNA splicing is responsible for much of the transcriptomic and proteomic diversity observed in higher order eukaryotes. Aberrations that disrupt regular alternative splicing patterns are known to cause human diseases, including various cancers. Alternative splicing is a combinatorial process, meaning many factors affect which two splice sites are ligated together. The features that dictate exon inclusion are comprised of splice site strength, intron-exon architecture, RNA secondary structure, splicing regulatory elements, promoter use and transcription speed by RNA polymerase and the presence of post-transcriptional nucleotide modifications. A comprehensive view of all of the factors that influence alternative splicing decisions is necessary to predict splicing outcomes and to understand the molecular basis of disease. This article is part of a Special Issue entitled: RNA structure and splicing regulation edited by Francisco Baralle, Ravindra Singh and Stefan Stamm.
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Affiliation(s)
- Hossein Shenasa
- Department of Microbiology and Molecular Genetics, University of California, Irvine, CA 92697, United States of America
| | - Klemens J Hertel
- Department of Microbiology and Molecular Genetics, University of California, Irvine, CA 92697, United States of America.
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Shenasa M, Heidary S, Shenasa H. Inappropriate ICD shock due to hot tub-induced external electrical interference. J Electrocardiol 2018; 51:852-855. [PMID: 30177327 DOI: 10.1016/j.jelectrocard.2018.06.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Revised: 06/01/2018] [Accepted: 06/26/2018] [Indexed: 11/25/2022]
Abstract
BACKGROUND A 72-year-old white male with a history of rapid nonsustained ventricular tachycardia, hypertrophic cardiomyopathy, and intermittent Brugada-type ECG had a single-lead implantable cardioverter-defibrillator (ICD) implantation and received a sudden ICD shock while in the hot tub. To the best of our knowledge this is the first case report of hot tub jet-induced inappropriate ICD shock. METHODS ICD interrogation and analysis of intracardiac electrograms and event markers. RESULTS ICD interrogation revealed inappropriate ICD shocks due to electrical interference of hot tub engine; 60-cycle electrical artifact mimicking fast ventricular fibrillation erroneously detected by the device. The device then delivered a 34.8 joules shock while the patient was actually in sinus rhythm. CONCLUSIONS Electrical interference due to external sources such as hot tub engines may occur and produce an inappropriate detection and ICD shock. Precaution and patient education is warranted.
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Affiliation(s)
- Mohammad Shenasa
- Heart & Rhythm Medical Group, San Jose, CA 95128, USA; O'Connor Hospital, San Jose, CA 95128, USA.
| | - Shahriar Heidary
- Heart & Rhythm Medical Group, San Jose, CA 95128, USA; O'Connor Hospital, San Jose, CA 95128, USA
| | - Hossein Shenasa
- Heart & Rhythm Medical Group, San Jose, CA 95128, USA; O'Connor Hospital, San Jose, CA 95128, USA
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7
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Abstract
Hypertension (HTN) is the most common cause of hypertensive heart disease, which comprises of left ventricular hypertrophy (LVH), left atrial enlargement, diastolic dysfunction, functional mitral regurgitation and neurohormonal changes. All of these lead to significant arrhythmias such as atrial fibrillation (AF) as well as ventricular arrhythmias, and are known risk factors for sudden cardiac death (SCD). The association between LVH and SCD is well established, especially in the presence of myocardial ischemia, fibrosis and scar tissue, and AF. Inflammation, fibrosis and oxidative stress, as well as ischemia play a significant role and are the leading pathways to remodeling, arrhythmias, and SCD. Aggressive HTN control may lead, at least in part, to regression of LVH and thus lower the risk of AF and SCD. Therefore, LVH is a powerful, independent predictor of AF, ventricular arrhythmias and SCD, and is significantly underrecognized. Further investigation of the relationship and management of diastolic dysfunction, LVH and genetic factors and their association with SCD is certainly warranted.
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Affiliation(s)
- Mohammad Shenasa
- Department of Cardiovascular Services, O'Connor Hospital, Heart & Rhythm Medical Group, 105 North Bascom Ave, Suite 204, San Jose, CA 95128, United States.
| | - Hossein Shenasa
- Department of Cardiovascular Services, O'Connor Hospital, Heart & Rhythm Medical Group, 105 North Bascom Ave, Suite 204, San Jose, CA 95128, United States
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Abstract
Ranolazine is currently approved as an antianginal agent in patients with chronic angina (class IIA). Ranolazine exhibits antiarrhythmic effects that are related to its multichannel blocking effect, predominantly inhibition of late sodium (late INa) current and the rapid potassium rectifier current (IKr), as well as ICa, late ICa, and INa-Ca. It also suppresses the early and delayed after depolarizations. Ranolazine is effective in the suppression of atrial and ventricular arrhythmias (off-label use) without significant proarrhythmic effect. Currently, ongoing trials are evaluating the efficacy and safety of ranolazine in patients with cardiac arrhythmias; preliminary results suggest that ranolazine, when used alone or in combination with dronedarone, is safe and effective in reducing atrial fibrillation. Ranolazine is not currently approved by the US Food and Drug Administration as an antiarrhythmic agent.
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Affiliation(s)
- Mohammad Shenasa
- Heart and Rhythm Medical Group, Department of Cardiovascular Services, O'Connor Hospital, 105 North Bascom Avenue, San Jose, CA 95128, USA.
| | - Hamid Assadi
- Heart and Rhythm Medical Group, Department of Cardiovascular Services, O'Connor Hospital, 105 North Bascom Avenue, San Jose, CA 95128, USA
| | - Shahriar Heidary
- Heart and Rhythm Medical Group, Department of Cardiovascular Services, O'Connor Hospital, 105 North Bascom Avenue, San Jose, CA 95128, USA
| | - Hossein Shenasa
- Heart and Rhythm Medical Group, Department of Cardiovascular Services, O'Connor Hospital, 105 North Bascom Avenue, San Jose, CA 95128, USA
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Assadi HR, Shenasa H, Heidary S, Afjei SA, Aminilari S, Shenasa M. IMPROVEMENT IN DIASTOLIC INDICES BY RANOLAZINE: A POTENTIAL MECHANISM FOR ITS ANTI-ISCHEMIC AND ANTIARRHYTHMIC EFFECTS. J Am Coll Cardiol 2015. [DOI: 10.1016/s0735-1097(15)60385-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Shenasa M, Shenasa H, Soleimanieh M. Update on atrial fibrillation. Egypt Heart J 2014. [DOI: 10.1016/j.ehj.2014.03.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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DeGuzman V, Vercoutere W, Shenasa H, Deamer D. Generation of oligonucleotides under hydrothermal conditions by non-enzymatic polymerization. J Mol Evol 2014; 78:251-62. [PMID: 24821106 DOI: 10.1007/s00239-014-9623-2] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Accepted: 05/02/2014] [Indexed: 11/28/2022]
Abstract
We previously reported that 5'-mononucleotides organized within a multilamellar lipid matrix can produce oligomers in the anhydrous phase of hydration-dehydration (HD) cycles. However, hydrolysis of oligomers can occur during hydration, and it is important to better understand the steady state in which ester bond synthesis is balanced by hydrolysis. In order to study condensation products of mononucleotides and hydrolysis of their polymers, we established a simulation of HD cycles that would occur on the early Earth when volcanic land masses emerged from the ocean over 4 billion years ago. At this stage on early Earth, precipitation produced hydrothermal fields characterized by small aqueous pools undergoing evaporation and refilling at elevated temperatures. Here, we confirm that under these conditions, the chemical potential made available by cycles of hydration and dehydration is sufficient to drive synthesis of ester bonds. If 5'-mononucleotides are in solution at millimolar concentrations, then oligomers resembling RNA are synthesized and exist in a steady state with their monomers. Furthermore, if the mononucleotides can form complementary base pairs, then some of the products have properties suggesting that secondary structures are present, including duplex species stabilized by hydrogen bonds.
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Affiliation(s)
- Veronica DeGuzman
- Advanced Studies Laboratory, NASA Ames Research Center, Moffett Field, CA, USA
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Kottkamp H, Hindricks G, Shenasa H, Chen X, Wichter T, Borggrefe M, Breithardt G. Variants of preexcitation--specialized atriofascicular pathways, nodofascicular pathways, and fasciculoventricular pathways: electrophysiologic findings and target sites for radiofrequency catheter ablation. J Cardiovasc Electrophysiol 1996; 7:916-30. [PMID: 8894934 DOI: 10.1111/j.1540-8167.1996.tb00466.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
INTRODUCTION In the present report, the electrophysiologic findings in patients with different types of variants of preexcitation, i.e., atriofascicular, nodofascicular, and fasciculoventricular fibers, and the results of radiofrequency catheter ablation using different target sites are described. METHODS AND RESULTS Twelve patients (mean age 36 +/- 17 years) with variants of the preexcitation syndromes underwent electrophysiologic study and radiofrequency catheter ablation. The atrial origin of atriofascicular pathways remote from the normal AV node was assessed by application of late atrial extrastimuli that advanced ("reset") the timing of the next QRS complex without anterograde penetration into the AV node. In patients with atriofascicular pathways, ablation of the accessory pathway or the retrograde fast AV node pathway was attempted. Ablation of the atriofascicular pathways was guided by a stimulus-delta wave interval mapping in the first five patients and by recording of atriofascicular pathway activation potentials in the next five patients. A nodofascicular pathway was suggested if VA dissociation occurred during tachycardia and if atrial extrastimuli failed to reset the tachycardia without anterograde penetration into the AV node. A fasciculoventricular connection was suggested if the proximal insertion of the accessory pathway was found to arise from the His bundle or bundle branches. The PR interval was expected within normal limits during sinus rhythm and the QRS complex to be slightly prolonged with a discrete slurring of the R wave, suggesting a small delta wave. Ten of the 12 patients had evidence for atriofascicular pathways and one patient each for a nodofascicular and fasciculoventricular pathway. In six patients, the atriofascicular pathways were successfully ablated, and in two patients, the retrograde fast AV node pathway. In one patient, a concealed right posteroseptal accessory AV pathway served as the retrograde limb and was successfully ablated. The nodofascicular pathway was shown to be a bystander during AV node reentrant tachycardia. After successful fast AV node pathway ablation resulting in marked PR prolongation, no preexcitation was present during sinus rhythm because of the proximal insertion of the nodofascicular pathway distal to the delay producing parts of the AV node. The proximal insertion of the fasciculoventricular pathway was suggested to arise distal to the AV node at the site of the penetrating AV bundle. The earliest ventricular activation at the His-bundle recording site indicated the ventricular insertion of this accessory connection into the ventricular summit. The fasciculoventricular connection gave rise to a fixed ventricular preexcitation and served as a bystander during orthodromic AV reentrant tachycardia incorporating a left-sided accessory AV pathway. CONCLUSION The majority of patients with variants of the preexcitation syndrome present with specialized atriofascicular pathways that seem to originate from remnants of the specialized AV ring tissue. Nodofascicular and fasciculoventricular pathways exist and may give rise to preexcitation, although their functional role in participation of clinical arrhythmias still needs to be elucidated. In the present study, both a fasciculoventricular pathway and a nodofascicular pathway acted as a bystander.
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Affiliation(s)
- H Kottkamp
- Hospital of the Westfälische Wilhelms-University, Department of Cardiology and Angiology, Münster, Germany
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Willems S, Shenasa H, Kottkamp H, Chen X, Hindricks G, Yli-Mäyry S, Haverkamp W, Wichter T, Rotman B, Breithardt G, Borggrefe M. Temperature-controlled slow pathway ablation for treatment of atrioventricular nodal reentrant tachycardia using a combined anatomical and electrogram guided strategy. Eur Heart J 1996; 17:1092-102. [PMID: 8809528 DOI: 10.1093/oxfordjournals.eurheartj.a015006] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
AIMS Anatomical and electrogram-guided techniques have been used separately for slow pathway ablation in atrioventricular nodal reentrant tachycardia. The aims of the present study were to analyse electrogram characteristics of target sites and biophysical parameters using a combined anatomical and electrogram-guided technique for temperature-controlled radiofrequency catheter ablation of the slow pathway. METHODS AND RESULTS Using a temperature-controlled (pre-selected 60 degrees C) catheter system, 53 patients with atrioventricular nodal reentrant tachycardia underwent slow pathway radiofrequency ablation. Mapping was started posteroseptally near the coronary sinus ostium and continued towards the midseptal area if needed. The longest and latest atrial electrograms with an atrioventricular ratio of < or = 0.5 were targeted. After a median of two pulses (mean 2.36 +/- 1.33), atrioventricular nodal reentrant tachycardia was rendered non-inducible in all patients without complications. Successful sites had longer atrial electrograms (78.8 +/- 9.8 vs 67.6 +/- 13.3 ms, P < 0.003) and larger ventricular electrogram amplitudes (92.4 +/- 51.2 vs 63.1 +/- 28.8 mV, P < 0.05) than the failed sites, but had a similar atrioventricular ratio, P-A interval and atrial electrogram amplitude. Overall, an atrial electrogram duration of > or = 70 ms was associated with effective radiofrequency delivery, with 86% sensitivity and 62% specificity. The achieved temperature maximum was 62.3 +/- 9.8 degrees C at successful and 58.8 +/- 9.0 degrees C at unsuccessful sites (ns). There was no significant difference between successful and unsuccessful applications with respect to power output, impedance and total delivery energy. During a pre-discharge study, three patients with inducible atrioventricular nodal reentrant tachycardia underwent a repeat ablation. During 12.3 +/- 2.5 (6-15) months of follow-up, three others had a clinical recurrence of atrioventricular nodal reentrant tachycardia. CONCLUSIONS The combined approach for slow pathway ablation is highly effective, requiring a low number of radiofrequency pulses. Long atrial activation time seems to be the most powerful predictor of success. Similar catheter tip temperature levels during successful and unsuccessful radiofrequency applications indicate that suboptimal selection of target sites rather than ineffective heating due to poor catheter tissue coupling is responsible for unsuccessful energy delivery.
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Affiliation(s)
- S Willems
- Hospital of the Westfälische Wilhems University of Münster, Department of Cardiology and Angiology, Germany
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15
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Abstract
OBJECTIVES This study evaluates 1) the safety and efficacy of catheter delivery of radiofrequency current to eliminate sustained sinoatrial node reentrant tachycardia; 2) the incidence of sinoatrial node reentrant tachycardia in the current group of patients undergoing electrophysiologic study for paroxysmal supraventricular tachycardia; and 3) the association of sinoatrial node reentrant tachycardia with other tachyarrhythmias. BACKGROUND Sustained sinoatrial node reentrant tachycardia is an uncommon cause of paroxysmal supraventricular tachycardia that is reported to occur infrequently in conjunction with other arrhythmias. Although pharmacologic and surgical therapies are available, there is limited information with regard to catheter ablation of sinoatrial node reentrant tachycardia. METHODS Ten patients with sustained sinoatrial node reentrant tachycardia underwent electrophysiologic study and radiofrequency current ablation. Patients were followed up for 9.2 +/- 6.0 months. RESULTS Of 343 consecutive patients referred for electrophysiologic evaluation of paroxysmal supraventricular tachycardia, 11 (3.2%) were found to have inducible sustained sinoatrial node reentrant tachycardia. Nine of the 11 patients had other associated arrhythmias, including atrioventricular (AV) node reentrant tachycardia (6 patients), AV reciprocating tachycardia (2 patients), ectopic atrial tachycardia (2 patients) and bundle branch reentrant tachycardia (1 patient). In 10 patients, direct ablation of sinoatrial node reentrant tachycardia was attempted and was successful in all (confidence interval for failure 0-0.26). Sinoatrial node reentrant tachycardia was eliminated with a median of four radiofrequency current applications (range 1 to 10) at 20 to 30 W. Successful ablation site characteristics during sinoatrial node reentrant tachycardia included 1) atrial activation > or = 35 ms (mean 44 +/- 8 ms) before the onset of the surface P wave, 2) atrial activation > or = 20 ms (mean 28 +/- 6 ms) before the onset of high right atrial activation, and 3) significantly prolonged and fractionated electrograms (mean duration 87 +/- 21 ms). No complications were encountered, and there have been no recurrences of sinoatrial node reentrant tachycardia. CONCLUSIONS Sinoatrial node reentrant tachycardia may be effectively and safely treated with radiofrequency current ablation at the site of earliest atrial activation.
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Affiliation(s)
- W E Sanders
- Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710
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Page RL, Shenasa H, Evans JJ, Sorrentino RA, Wharton JM, Prystowsky EN. Radiofrequency catheter ablation of idiopathic recurrent ventricular tachycardia with right bundle branch block, left axis morphology. Pacing Clin Electrophysiol 1993; 16:327-36. [PMID: 7680462 DOI: 10.1111/j.1540-8159.1993.tb01584.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Idiopathic ventricular tachycardia with right bundle branch block and left axis deviation morphology is a well described clinical syndrome. Previous studies have mapped the tachycardia focus to the inferior septal region at the base of the posterior papillary muscle of the left ventricle. We describe two typical cases in a 20-year-old man and 29-year-old woman in which the tachycardia focus was localized with endocardial mapping techniques. In both cases the ventricular tachycardia focus was ablated with application of radiofrequency current at the inferior septal region. There were no complications of the procedures. The patients remain asymptomatic over follow-up of 7 and 4 months, respectively.
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Affiliation(s)
- R L Page
- Department of Medicine, Duke University Medical Center, Durham, North Carolina
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Shenasa H, Calderone A, Vermeulen M, Paradis P, Stephens H, Cardinal R, de Champlain J, Rouleau JL. Chronic doxorubicin induced cardiomyopathy in rabbits: mechanical, intracellular action potential, and beta adrenergic characteristics of the failing myocardium. Cardiovasc Res 1990; 24:591-604. [PMID: 2170016 DOI: 10.1093/cvr/24.7.591] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
STUDY OBJECTIVE The aim was to assess myocardial, electrophysiological, and adrenergic changes caused by chronic administration of doxorubicin. DESIGN Doxorubicin induced cardiotoxicity was produced in three groups of rabbits by injecting doxorubicin 0.75 mg.kg-1 three times a week for 7, 9 and 11 weeks. There were 36 controls. All studies were conducted within 16 to 36 h after the last injection. Histological, mechanical, and action potential changes produced by doxorubicin were examined in vitro. The effects of doxorubicin on beta adrenergic receptors and cyclic adenosine monophosphate (AMP) generation in myocardial membrane preparations were also evaluated. EXPERIMENTAL MATERIAL 145 New Zealand white rabbits, 2.4-2.7 kg, were used. After excision of the heart, a papillary muscle was used for mechanical studies, a portion of the septum for intracellular action potential studies, and the rest of the heart for histological or biochemical studies. MEASUREMENTS AND RESULTS Histological studies showed widespread myocardial damage that became more severe as the cumulative doses increased. Right ventricular papillary muscles of doxorubicin treated rabbits had lower total tension (1.5 v 3.3 g.mm-2 for controls, p less than 0.05) and dT/dt, shorter contraction duration, and lower velocity of shortening than the control muscles under all loading conditions. The changes progressed as the cumulative doxorubicin dose increased. Action potential duration was shorter in the doxorubicin treated groups (APD50 = 76 v 62 ms for controls, p less than 0.01), although resting action potential amplitude was normal. Tension-frequency response (6-36 stimuli.min-1) and response to increasing calcium concentrations (2.54-6.32 mM) were attenuated in the doxorubicin group. Percent change in tension and dT/dt in response to noradrenaline (50 microM), isoprenaline (20 microM), or dibutyryl cyclic AMP (40 mM), was increased in the doxorubicin group v controls (300-600% v 100-200% respectively), despite chronic increase in circulating catecholamines, depletion of myocardial catecholamines, and no change in beta adrenergic receptor number or affinity. The apparent increase in beta adrenergic responsiveness in the doxorubicin group may have been partly due to decreased basal cyclic AMP production (13 v 31 pMol.mg-1 protein.min-1, p less than 0.01), although maximum catecholamine stimulated cyclic AMP production was only mildly decreased (251 v 315 pMol.mg-1 protein.min-1, p less than 0.05). CONCLUSIONS - The subacute effects of chronic doxorubicin become progressively more marked as the cumulative dose increases, and there are significant differences in the myocardial characteristics between this chronic model and other models of heart failure. These differences may be related to the cytotoxic effects of doxorubicin on membranes and membrane bound enzymes.
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Affiliation(s)
- H Shenasa
- Research Center, Hôpital du Sacré-Coeur de Montréal, Québec, Canada
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Rouleau JL, Juneau C, Stephens H, Shenasa H, Parmley WW, Brutsaert DL. Mechanical properties of papillary muscle in cardiac failure: importance of pathogenesis and of ventricle of origin. J Mol Cell Cardiol 1989; 21:817-28. [PMID: 2528642 DOI: 10.1016/0022-2828(89)90721-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
In an attempt to better understand what causes impairment of failing myocardium, the mechanical characteristics of papillary muscles from three different models of congestive heart failure were compared at varying stages of hypertrophy and failure: adriamycin cardiotoxic rabbit, cardiomyopathic hamster and infra-renal aorto-caval shunted dog. Except for right ventricular muscles from the shunted dogs, in all groups there was a significant decrease in total twitch tension, +dT/dt, -dT/dt, Vmax, +dL/dt, and -dL/dt. However, there were major differences in twitch duration between the three models with time to attain peak tension and peak shortening and time to attain half tension decline decreasing in right ventricular papillary muscles from adriamycin rabbits but increasing in right ventricular papillary muscles from shunted dogs and no change occurring in left ventricular papillary muscles from cardiomyopathic hamsters or shunted dogs. Load dependence as assessed by time to relaxation index for 30% afterload contractions was decreased in all but right ventricular muscles from shunted dogs. These results indicate that despite some common characteristics, major differences exist between papillary muscles from different models of congestive heart failure depending on the pathophysiological process involved and the ventricle of origin.
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Affiliation(s)
- J L Rouleau
- Centre de Recherche, Hôpital du Sacré-Coeur de Montréal, Université de Montréal
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Paradis P, Rouleau JL, Shenasa H, Brakier-Gingras L. Protein synthesis is increased in heart failure induced by low dose adriamycin in rabbits. Can J Physiol Pharmacol 1989; 67:197-201. [PMID: 2743206 DOI: 10.1139/y89-033] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Congestive heart failure was induced in rabbits by a chronic treatment with a low dose of adriamycin (0.75 mg/kg intravenously 3 times per week for 11 weeks). Twenty-four to 48 h after the last injection, adriamycin-treated rabbits had a three-fold increase in plasma norepinephrine, a seven-fold increase in plasma epinephrine, a 19 +/- 8% increase in heart rate, and a 54 +/- 10% decrease in the total tension generated by their isolated papillary muscles, when compared with normal age-matched controls. This demonstrated the occurrence of the cardiomyopathy and heart failure. The effect of adriamycin on myocardial and diaphragmatic protein synthesis was examined in vivo after a 1-h infusion with [3H]leucine and in vitro after a 2-h incubation of right ventricular papillary muscle with [3H]leucine. The rate of in vivo [3H]leucine incorporation into total protein was increased in the heart of the adriamycin-treated rabbits. The increases were 60 +/- 16% in the left ventricle, 49 +/- 18% in the septum, 32 +/- 18% in the right ventricle, and 66 +/- 16% in the atria. A similar increase was observed when measuring the rate of [3H]leucine incorporation into myosin, a myofibrillar protein, and when the rate of [3H]leucine incorporation into total protein was measured in vitro in papillary muscle. In contrast, the rate of [3H]leucine incorporation into total protein of the diaphragm was not significantly changed.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- P Paradis
- Centre de recherche, Hôpital du Sacré-Coeur, Montréal, Québec, Canada
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Rouleau JL, Paradis P, Shenasa H, Juneau C. Faster time to peak tension and velocity of shortening in right versus left ventricular trabeculae and papillary muscles of dogs. Circ Res 1986; 59:556-61. [PMID: 3802429 DOI: 10.1161/01.res.59.5.556] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Some of the mechanical characteristics of papillary muscles and trabeculae (n = 14) isolated from the free wall of the right ventricle of dogs were compared to those obtained from the free wall of the left ventricle (n = 14). Peak total tension (7.2 +/- 1.6 versus 7.9 +/- 1.7 g/mm2, p = NS) and peak velocity of tension development (31 +/- 8 vs. 28 +/- 4 g/mm2/sec, p = NS) were similar in both groups of muscles. However, right ventricular muscles shortened faster over nearly all loading conditions, and during isometric contraction, their time to attain peak total tension was shorter (336 +/- 26 vs. 401 +/- 42 msec, p less than 0.005) than that of left ventricular muscles. Varying stimulation rates (6, 12, 24, and 36 stimuli/min), increasing calcium concentration from 2.54 to 6.35 mM or adding norepinephrine 50 microM, did not significantly alter these differences. There were no differences in myosin isozymes (V1, V2, or V3) between ventricles to explain these differences. These results indicate that important mechanical differences exist between right and left ventricular myocardium and that these differences should be considered when extrapolations are made from myocardium of one area of the heart to another.
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