Kalyanam Shivkumar

Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California, United States

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Publications (221)938.88 Total impact

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    ABSTRACT: Vagal nerve stimulation (VNS) has been proposed as a cardio-protective intervention. However, regional ventricular electrophysiological effects of VNS are not well characterized. The purpose of this study was to evaluate effects of right and left VNS on electrophysiological properties of the ventricles and hemodynamic parameters. In Yorkshire pigs, a 56-electrode sock was used for epicardial (n=12) and a 64-electrode catheter for endocardial (n=9) activation recovery interval (ARI) recordings at baseline and during VNS. Hemodynamic recordings were obtained using a conductance catheter. Right and left VNS decreased heart rate (84±5 to 71±5 bpm, and 84±4 to 73±5 bpm), LV pressure (89±9 to 77±9 mmHg, and 91±9 to 83±9 mmHg), dP/dt max (1660±154 to 1490±160 mmHg/s, and 1595±155 to 1416±134 mmHg/s) and prolonged ARI (327±18 to 350±23 ms, and 327±16 to 347±21 ms), respectively, p < 0.05 vs. baseline for all parameters, p = NS for right vs. left VNS. No anterior-posterior-lateral regional differences in prolongation of ARI during right or left VNS were found. However, endocardial ARI prolonged more than epicardial, and apical ARI more than basal ARI during both right and left VNS. Changes in dP/dt max showed the strongest correlation with ventricular ARI effects (R(2) = 0.81, p < 0.0001) than either heart rate (R(2) = 0.58, p < 0.01), or LV pressure (R(2)=0.52, p < 0.05). Therefore, right and left VNS have similar effects on ventricular ARI in contrast to sympathetic stimulation that shows regional differences. Decrease in inotropy correlates best with ventricular electrophysiological effects.
    American journal of physiology. Heart and circulatory physiology. 07/2014;
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    ABSTRACT: The goal of this study was to examine the association between ECG repolarization parameters and mortality in Chagas disease (CD) patients living in the United States.
    Indian pacing and electrophysiology journal 07/2014; 14(4):171-80.
  • Article: Abstracts.
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    ABSTRACT: There is a paucity of data on biophysical parameters during radiofrequency ablation of scar-mediated ventricular tachycardia (VT).
    Journal of Cardiovascular Electrophysiology 06/2014; · 3.48 Impact Factor
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    ABSTRACT: The success of pulmonary vein isolation (PVI) for atrial fibrillation (AF) may be improved if stable AF sources identified by Focal Impulse and Rotor Mapping (FIRM) are also eliminated. The long-term results of this approach are unclear outside the centers where FIRM was developed; thus, we assessed outcomes of FIRM-guided AF ablation in the first cases at 10 experienced centers.
    Journal of Cardiovascular Electrophysiology 06/2014; · 3.48 Impact Factor
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    ABSTRACT: Background There is a paucity of data on biophysical parameters during radiofrequency ablation of scar-mediated ventricular tachycardia (VT).Methods and ResultsData was collected from consecutive patients undergoing VT ablation with open-irrigation. Complete data was available for 372 lesions in 21 patients. The frequency of biophysical parameter changes were: >10Ω reduction (80%), bipolar EGM reduction (69%), while loss of capture was uncommon (32%). Unipolar injury current was seen in 72% of radiofrequency applications. Both EGM reduction and impedance drop were seen in 57% and a change in all 3 parameters was seen in only 20% of lesions. Late potentials were eliminated in 33%, reduced/modified in 56%, and remained after ablation in 11%. Epicardial lesions exhibited an impedance drop (90% vs 76%, p = 0.002) and loss of capture (46% vs 27%, p<0.001) more frequently than endocardial lesions. Lesions delivered manually exhibited a >10Ω impedance drop (83% vs 71%, p = 0.02) and an EGM reduction (71% vs 40%, p< 0.001) more frequently than lesions applied using magnetic navigation, although loss of capture, elimination of LPs, and a change in all 3 parameters were similarly observed.ConclusionsVT ablation is inefficient as the majority of radiofrequency lesions do not achieve more than one targeted biophysical parameter. Only one-third of RF applications targeted at LPs result in complete elimination. Epicardial ablation within scar may be more effective than endocardial lesions and lesions applied manually may be more effective than lesions applied using magnetic navigation. New technologies directed at identifying and optimizing ablation effectiveness in scar are clinically warranted.This article is protected by copyright. All rights reserved.
    Journal of Cardiovascular Electrophysiology 06/2014; · 3.48 Impact Factor
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    ABSTRACT: Clinically evident sarcoidosis involving the heart has been noted in at least 2 to 7% of patients with sarcoidosis, but occult involvement is much higher (> 20%). Cardiac sarcoidosis is often not recognized antemortem, as sudden death may be the presenting feature. Cardiac involvement may occur at any point during the course of sarcoidosis and may occur in the absence of pulmonary or systemic involvement. Sarcoidosis can involve any part of the heart, with protean manifestations. Prognosis of cardiac sarcoidosis is related to extent and site(s) of involvement. Most deaths due to cardiac sarcoidosis are due to arrhythmias or conduction defects, but granulomatous infiltration of the myocardium may be lethal. The definitive diagnosis of isolated cardiac sarcoidosis is difficult. The yield of endomyocardial biopsies is low; treatment of cardiac sarcoidosis is often warranted even in the absence of histologic proof. Radionuclide scans are integral to the diagnosis. Currently, 18F-fluorodeoxyglucose positron emission tomography/computed tomography and gadolinium-enhanced magnetic resonance imaging scans are the key imaging modalities to diagnose cardiac sarcoidosis. The prognosis of cardiac sarcoidosis is variable, but mortality rates of untreated cardiac sarcoidosis are high. Although randomized therapeutic trials have not been done, corticosteroids (alone or combined with additional immunosuppressive medications) remain the mainstay of treatment. Because of the potential for sudden cardiac death, implantable cardioverter-defibrillators should be placed in any patient with cardiac sarcoidosis and serious ventricular arrhythmias or heart block, and should be considered for cardiomyopathy. Cardiac transplantation is a viable option for patients with end-stage cardiac sarcoidosis refractory to medical therapy.
    Seminars in Respiratory and Critical Care Medicine 06/2014; 35(3):372-390. · 2.75 Impact Factor
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    ABSTRACT: Background There are a variety of periprocedural anticoagulation strategies for atrial fibrillation (AF) ablation, including the use of dabigatran. It is unclear which strategy is superior.Objective To compare the safety and efficacy of anticoagulation with uninterrupted warfarin, dabigatran, and warfarin with heparin bridging in patients undergoing ablation of AF at four experienced centers.Methods and ResultsIn this retrospective analysis, 882 patients (mean age: 61 ± 11 years) underwent ablation of AF using uninterrupted warfarin (n = 276), dabigatran (n = 374), or warfarin with heparin bridging (n = 232) for periprocedural anticoagulation. The rate of total complications was 23/276 (8.3%) in the uninterrupted warfarin group, 30/374 (8.0%) in the dabigatran group, and 29/232 (12.5%) in the bridged group (P = 0.15). Major complications were more frequent in the uninterrupted warfarin group 12/276 (4.3%) compared with 3/374 (0.8%) in dabigatran and 6/232 (2.6%) in the bridged group (P = 0.01). The most common major complication was the need for transfusion or occurrence of major bleeding. Minor complications did not differ among the three groups. On multivariate analysis, female gender (odds ratio [OR] 1.93, confidence interval [CI] 1.16–3.19, P = 0.011), bridging heparin (OR 2.13, CI 1.100–3.941, P = 0.016), use of triple antithrombotic therapy (OR 1.77, CI 1.05–2.98, P = 0.033), and prior myocardial infarction (OR 2.40, CI 1.01–5.67, P = 0.046) independently predicted total complications.Conclusions When comparing the use of uninterrupted warfarin, dabigatran, and warfarin with heparin bridging in patients undergoing catheter ablation of AF, dabigatran was not associated with increased risk, major complications were more common in the uninterrupted warfarin group, and after adjustment, warfarin with bridging increased total complications.
    Pacing and Clinical Electrophysiology 05/2014; · 1.75 Impact Factor
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    ABSTRACT: Background Cocaine use is a known but rare cause of cardiac arrhythmias. Ventricular arrhythmias related to cocaine may not respond to antiarrhythmic drugs and may need treatment with radiofrequency ablation.Objectives We describe the clinical and electrophysiological characteristics of cocaine- related ventricular tachycardia (VT) from a multicenter registry.Methods Subjects presenting with VT related to cocaine use and being considered for radiofrequency ablation have been included in the study. Patients who were refractory to maximal medical therapy underwent radiofrequency ablation of the VT. Clinical, procedural variables, efficacy and safety outcomes were assessed.ResultsA total of 14 subjects met study criteria (age 44±13, range 18–68 year-old with 79% male, 71% Caucasian). MRI showed evidence of scar only in 43% of patients (6/14). The mechanism of VT was focal in 50% (n = 7) and scar related reentry in 50% (n = 7) based on 3D mapping. The mean VT cycle length was 429±96 msec. The site of origin was epicardial in 16% (3/18) of VTs. Most clinical VTs were hemodynamically stable (75%). Mean ejection fraction at the time of admission was 44±14%. Duration of procedure was 289±50 minutes. One subject developed pericardial tamponade requiring drainage. At 18±11 months follow-up, freedom from arrhythmia was seen in 86% (one case lost to follow-up and 2 died).Conclusion Radiofrequency ablation is not only feasible but also safe and effective in patients who have drug refractory VT related to chronic cocaine use.This article is protected by copyright. All rights reserved.
    Journal of Cardiovascular Electrophysiology 04/2014; · 3.48 Impact Factor
  • Journal of vascular and interventional radiology: JVIR 04/2014; 25(4):497-509. · 1.81 Impact Factor
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    ABSTRACT: -Data on relative safety, efficacy and role of different percutaneous left ventricular assist devices (pLVADs) for hemodynamic support during the ventricular tachycardia (VT) ablation procedure are very limited. -We performed a multicenter, observational study from a prospective registry including all consecutive patients (N=66) undergoing VT ablation with a pLVAD in 6 centers in United States. Patients with intra aortic balloon pump (IABP group; N=22) were compared with patients with either an Impella or a TandemHeart deivce (Non-IABP group; N=44). There were no significant differences in the baseline characteristics between both the groups. In Non-IABP group a) more patients could undergo entrainment/activation mapping (82% vs 59%; p=0.046), b) more number of unstable VTs could be mapped and ablated per patient (1.05±0.78 vs 0.32±0.48; p<0.001), c) more number of VTs could be terminated by ablation (1.59±1.0 vs 0.91±0.81; p=0.007) and d) fewer VTs were terminated with rescue shocks (1.9±2.2 vs 3.0±1.5; p=0.049) when compared to IABP group. Complications of the procedure trended to be more in the Non-IABP group when compared to the IABP group (32% vs 14%; p=0.143). Intermediate term outcomes (mortality and VT recurrence) during 12±5 month follow-up were not different between both the groups. Left ventricular ejection fraction ≤ 15% was a strong and independent predictor of in-hospital mortality (53% vs 4%; p<0.001). -Impella and TandemHeart use in VT ablation facilitates extensive activation mapping of several unstable VTs and requires fewer rescue shocks during the procedure when compared to using IABP.
    Circulation Arrhythmia and Electrophysiology 02/2014; · 5.95 Impact Factor
  • Pradeep S. Rajendran, Eric Buch, Kalyanam Shivkumar
    Journal of the American College of Cardiology 01/2014; · 14.09 Impact Factor
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    ABSTRACT: Objectives To determine if ablation that targets patient-specific AF-sustaining substrates (rotors or focal sources) is more durable than trigger ablation alone at preventing late AF recurrences. Background Late recurrence substantially limits the efficacy of pulmonary vein (PV) isolation for AF, and is associated with PV reconnection and the emergence of new triggers. Methods We performed 3 year follow-up of the CONFIRM trial, in which 92 consecutive AF patients (70.7% persistent) underwent novel computational mapping to reveal a median of 2 (IQR 1-2) rotors or focal sources in 97.7% of patients during AF. Ablation comprised source (Focal Impulse and Rotor Modulation, FIRM) then conventional ablation in n=27 (FIRM-guided), and conventional ablation alone in n=65 (FIRM-blinded). Patients were followed with implanted ECG monitors when possible (85.2% FIRM guided, 23.1% FIRM-blinded). Results On 890 days follow-up (median; IQR 224–1563) compared FIRM-blinded therapy, patients receiving FIRM-guided ablation maintained higher freedom from AF after 1.2±0.4 procedures (median 1, IQR 1-1) (77.8% vs 38.5%; p=0.001) and a single procedure (p>0.001), and higher freedom from all atrial arrhythmias (p=0.003). Freedom from AF was higher when ablation directly or coincidentally passed through sources than when it missed sources (p>0.001). Conclusions FIRM-guided ablation is more durable than conventional trigger-based ablation at preventing 3 year AF recurrence. Future studies should investigate how ablation of patient-specific AF-sustaining rotors and focal sources alters the natural history of arrhythmia recurrence. Clinical trial info NCT01008722
    Journal of the American College of Cardiology 01/2014; · 14.09 Impact Factor
  • Jason S. Bradfield, Marmar Vaseghi, Kalyanam Shivkumar
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    ABSTRACT: The autonomic nervous system is known to play a significant role in the genesis and persistence of arrhythmias. Neuromodulation has become a new therapeutic strategy for the treatment of ventricular arrhythmias. Catheter based renal denervation (RDN) is being studied as a treatment option for drug-refractory hypertension. Ablation within the renal arteries, by altering efferent and afferent signaling, has the potential to improve blood pressure as well as heart failure, atrial, and ventricular tachyarrhythmias.
    Trends in Cardiovascular Medicine. 01/2014;
  • Heart Rhythm. 01/2014;
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    ABSTRACT: We report here, for the first time, two cases demonstrating a synergistic application of bilateral cardiac sympathetic decentralization and multimodal psychiatric treatment for the assessment and management of anxiety following recurrent Implantable Cardioverter Defibrillator (ICD) shocks. In a first case the combination of bilateral cardiac sympathetic decentralization (BCSD), cognitive behavioral psychotherapy and anxiolytic medication was sufficient to attenuate the patient's symptoms and maladaptive behaviors, with a maintained benefit at 1 year. Among the more prominent subjective changes in the post-lesion state we observed a decrease in aversive interoceptive sensations, particularly of the heartbeat. The patient continued to experience cognitive threat appraisals on a frequent basis, although these were no longer incapacitating. In a second case, we report the effect of BCSD on autonomic tone and subjective state. In the post-lesion state we observed attenuated sympathetic responses to the valsalva maneuver, isometric handgrip and mental arithmetic stressor, including decreased systolic and diastolic blood pressure and, decreased skin conductance. Collectively, these preliminary findings suggest that an integrative, multidisciplinary approach to treating anxiety disorders in the setting of ventricular arrhythmias and recurrent ICD shocks can result in sustained improvements in physical, psychological, and functional status. These findings raise the possibility of a potential role for the stellate ganglion in the modulation of emotional experience and afferent transmission of interoceptive information to the central nervous system.
    Frontiers in Integrative Neuroscience 01/2014; 7:98.
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    ABSTRACT: Objectives The objective of this study was to determine whether premature ventricular contractions (PVCs) arising from the aortic sinuses of Valsalva (SOV) and great cardiac vein (GCV) have coupling interval (CI) characteristics that differentiate them from other ectopic foci. Background PVCs occur at relatively fixed CI from the preceding normal QRS in most patients. However, we observed patients with PVCs originating in unusual areas (SOV and GCV) in whom the PVC CI was highly variable. We hypothesized that PVCs from these areas occur seemingly randomly due to lack of electrotonic effects of surrounding myocardium. Methods 73 consecutive patients referred for PVC ablation were assessed. Twelve consecutive PVC coupling intervals were recorded. The ΔCI (max-min CI) was measured. Results We studied 73 patients (age 50±16 years, 47% male). PVC origin was right ventricular (RV) in 29 (40%), left ventricular (LV) in 17 (23%), SOV 21 (29%) and GCV in 6 (8%). There was a significant difference between the mean ΔCI of RV/LV compared to SOV/GCV PVCs (33±15 ms vs 116±52 ms, p<0.0001). A ΔCI of>60 ms demonstrated a sensitivity of 89%, specificity of 100%, positive predictive value of 100% and negative predictive value of 94%. Cardiac events were more common in the SOV/GCV vs the RV/LV group (7/27 [26%] vs 2/46 [4%], p<0.02). Conclusions ΔCI is more pronounced in PVCs originating from the SOV or GCV. ΔCI of 60 ms helps discriminate the origin of PVCs prior to diagnostic electrophysiologic study and may be associated with increased frequency of cardiac events.
    Journal of the American College of Cardiology 01/2014; · 14.09 Impact Factor
  • Cardiac electrophysiology clinics 01/2014;
  • Olujimi A Ajijola, Roderick Tung, Kalyanam Shivkumar
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    ABSTRACT: Advances in the treatment of myocardial infarction (MI) have improved survival after ischemic cardiac injury. Post-infarct structural and functional remodeling results in electrophysiologic substrates at risk for monomorphic ventricular tachycardia (MMVT). Characterization of this substrate using a variety of clinical and investigative tools has improved our understanding of MMVT circuits, and has accelerated the development of device and catheter-based therapies aimed at identification and elimination of this arrhythmia. This review will discuss the central role of the ischemic heart disease substrate in the development MMVT. Electrophysiologic characterization of the post-infarct myocardium using bipolar electrogram amplitudes to delineate scar border zones will be reviewed. Functional electrogram determinants of reentrant circuits such as isolated late potentials will be discussed. Strategies for catheter ablation of reentrant ventricular tachycardia, including structural and functional targets will also be examined, as will the role of the epicardial mapping and ablation in the management of recurrent MMVT.
    Indian heart journal 01/2014; 66S1:S24-S34.
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    ABSTRACT: Left and bilateral CSD have been shown to reduce burden of ventricular arrhythmias acutely in a small number of patients with VT storm. The effects of this procedure beyond the acute setting are unknown. The purpose of this study was to evaluate the intermediate and long-term effects of left and bilateral cardiac sympathetic denervation (CSD) in patients with cardiomyopathy and refractory ventricular tachy-arrhythmias (VT) or VT storm. Retrospective analysis of medical records for patients who underwent either left or bilateral cardiac sympathetic denervation for VT storm or refractory VT between April 2009 and December 2012 was performed. Forty one patients underwent CSD (left CSD: n = 14; bilateral CSD: n = 27). There was a significant reduction in the burden of ICD shocks during follow up as compared to the 12 months prior to the procedure. The number of ICD shocks was reduced from a mean of 19.6±19 pre-procedure to 2.3±2.9 post-procedure, P<0.001, with 90% of patients experiencing a reduction in ICD shocks. At a mean follow up of 367±251 days post-procedure, survival free of ICD shock was 30% of in the left CSD group and 48% in the bilateral CSD group. Shock free survival was greater in the bilateral group than in the left CSD group, P=0.04. In patients with VT storm, bilateral CSD is more beneficial than left CSD. The beneficial effects of bilateral CSD extend beyond the acute post-sympathectomy period, with continued freedom from ICD shocks in 48% of patients and a significant reduction in ICD shocks in 90% of patients.
    Heart rhythm: the official journal of the Heart Rhythm Society 11/2013; · 4.56 Impact Factor
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    ABSTRACT: The aim of this study was to determine the pertinent anesthetic considerations for patients undergoing surgical sympathectomy for electrical storm (incessant ventricular tachycardia (VT) refractory to traditional therapies). This is a retrospective review of a prospective database. This single-center study took place in a university hospital setting. Twenty-six patients were enrolled. Fifteen patients underwent left-sided sympathectomy, whereas 11 patients underwent bilateral sympathectomy. Anesthetic management of these patients was quite complex, requiring invasive monitoring, transesophageal echocardiography, one-lung ventilation, programming of cardiac rhythm management devices, and titration of vasoactive medications. Paired t test of hemodynamic data before, during, and after surgery showed no significant difference between preoperative and postoperative blood pressure values, regardless of whether the patient underwent unilateral or bilateral sympathectomy. Eight patients remained free of VT, three patients responded well to titration of oral medications, and one patient required 2 radiofrequency ablations after sympathectomy to control his VT. Three patients continued to have VT episodes, although reduced in frequency compared with before the procedure. Four patients were lost to followup. Overall, five patients within the cohort died within 30 days of the procedure. No patients developed any anesthetic complications or Horner's syndrome. The overall perioperative mortality (within the first 7 days of the procedure) was 2 of 26, or 7.7%. The anesthetic management of patients undergoing surgical sympathectomy for electrical storm can be quite complex, because these patients often present in a moribund and emergent state and cannot be optimized using current ACC/AHA guidelines. Expertise in invasive monitoring, transesophageal echocardiography, one-lung ventilation, cardiac rhythm device management, and pressor management is crucial for optimal anesthetic care.
    Journal of cardiothoracic and vascular anesthesia 11/2013; · 1.06 Impact Factor

Publication Stats

1k Citations
938.88 Total Impact Points

Institutions

  • 2014
    • Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center
      Torrance, California, United States
  • 1998–2014
    • University of California, Los Angeles
      • Division of Cardiology
      Los Angeles, California, United States
  • 2012–2013
    • University of California, San Diego
      • Department of Medicine
      San Diego, California, United States
    • The Ohio State University
      Columbus, Ohio, United States
  • 2009–2013
    • University of Southern California
      Los Angeles, California, United States
    • UCLA Cardiovascular Research Laboratory
      Los Angeles, California, United States
  • 2009–2012
    • University of California, Davis
      • Department of Biomedical Engineering
      Davis, CA, United States
  • 2011
    • CSU Mentor
      Long Beach, California, United States
    • St. David's North Austin Medical Center
      Austin, Texas, United States
  • 2010
    • University of Texas at Austin
      Austin, Texas, United States
  • 2007–2010
    • Stanford University
      • E. L. Ginzton Laboratory
      Stanford, CA, United States
  • 2007–2009
    • Oregon Health and Science University
      Portland, Oregon, United States
  • 2001–2002
    • University of Iowa
      Iowa City, Iowa, United States
    • University of Iowa Children's Hospital
      Iowa City, Iowa, United States
  • 1993–1996
    • Henry Ford Hospital
      • Department of Internal Medicine
      Detroit, Michigan, United States