Frequency Of Ventricular Tachycardia Research Articles

Evaluation of the effect of empagliflozin on prevention of atrial fibrillation after coronary artery bypass grafting: a double-blind, randomized, placebo-controlled trial.

This study is aimed at evaluating the effect of empagliflozin in preventing atrial fibrillation after coronary artery bypass grafting (CABG). Eighty-two patients who fulfilled the inclusion criteria were allocated to the empagliflozin group (n = 43) or placebo group (n = 39). In two groups, patients received empagliflozin or placebo tablets 3days before surgery and on the first three postoperative days (for 6days) in addition to the standard regimen during hospitalization. During the first 3days after surgery, types of arrhythmias after cardiac surgery, including supraventricular arrhythmias, especially postoperative atrial fibrillation (POAF), ventricular arrhythmias, and heart blocks, were assessed by electrocardiogram monitoring. C-reactive protein (CRP) levels were evaluated pre-operatively and postoperative on the third day. The incidence of POAF in the treatment group was lower compared to the control group; however, this reduction was statistically non-significant (p = 0.09). The frequency of ventricular tachycardia was reduced significantly in the treatment group versus patients in the control (p = 0.02). Also, a significant reduction in the frequency of premature ventricular contractions (PVCs) was seen in the treatment group in comparison with the control group (p = 0.001). After the intervention, CRP levels were significantly less in the empagliflozin group compared to the control group in the third postoperative day (p = 0.04). The prophylactic use of empagliflozin effectively reduced the incidence of ventricular arrhythmia in patients undergoing CABG surgery.

Premature ventricular complexes: Assessing burden density in a large national cohort to better define optimal ECG monitoring duration

BackgroundPremature ventricular contraction (PVC) burden is a risk factor for heart failure and cardiovascular death in patients with structural heart disease. Long-term electrocardiographic monitoring can have a significant impact on PVC burden evaluation by further defining PVC distribution patterns. ObjectiveThis study aimed to ascertain the optimal duration of electrocardiographic monitoring to characterize PVC burden and to understand clinical characteristics associated with frequent PVCs and nonsustained ventricular tachycardia in a large US cohort. MethodsCommercial data (iRhythm’s Zio patch) from June 2011 to April 2022 were analyzed. Inclusion criteria were age >18 years, PVC burden ≥5%, and wear period ≥13 days. PVC burden cutoffs were determined on the basis of AHA/ACC/HRS guidelines for very frequent PVCs (10,000–20,000 during 24 hours). Patients were assigned to categories by PVC densities: low, <10%; moderate, 10% to <20%; and high, ≥20%. Mean measured error was assessed at baseline and daily until the wear period’s end for overall PVC burden and different PVC densities. ResultsAnalysis of 106,705 patch monitors revealed a study population with mean age of 70.6 ± 14.6 years (33.6% female). PVC burden was higher in male patients and those >65 years of age. PVC burden mean error decreased from 2.9% at 24 hours to 1.3% at 7 days and 0.7% at 10 days. Number of ventricular tachycardia episodes per patient increased with increasing PVC burden (P < .0001). ConclusionExtending ambulatory monitoring beyond 24 hours to 7 days or more improves accuracy of assessing PVC burden. Ventricular tachycardia frequency and duration vary by initial PVC density, highlighting the need for prolonged cardiac monitoring.

Worldwide Experience With an Irrigated Needle Catheter for Ablation of Refractory Ventricular Arrhythmias: Final Report

BackgroundWe previously reported feasibility of irrigated needle ablation (INA) with a retractable 27-G end-hole needle catheter to treat nonendocardial ventricular arrhythmia substrate, an important cause of ablation failure. ObjectivesThe purpose of this study was to report outcomes and complications in our entire INA-treated population. MethodsPatients with recurrent sustained monomorphic ventricular tachycardia (VT) or high-density premature ventricular contractions (PVCs) despite radiofrequency ablation were prospectively enrolled at 4 centers. Endpoints included a 70% decrease in VT frequency or PVC burden decrease to <5,000/24 h at 6 months. ResultsINA was performed in 111 patients (median: 2 failed prior ablations, 71% nonischemic heart disease, and left ventricular ejection fraction 36% ± 14%). INA acutely abolished targeted PVCs in 33 of 37 patients (89%), and PVCs were reduced to <5,000/day in 29 patients (78%). During 6-month follow-up, freedom from hospitalization was observed in 50 of 72 patients with VT (69%), and improvement or abolition of VT occurred in 47%. All patients received multiple INA applications, with more in the VT group than in the PVC group (median: 12 [IQR: 7-19] vs 7 [5-15]; P < 0.01). After INA, additional endocardial standard radiofrequency ablation was required in 23% of patients. Adverse events included 4 pericardial effusions (3.5%), 3 cases of (anticipated) atrioventricular block (2.6%), and 3 heart failure exacerbations (2.6%). During 6-month follow-up, 5 deaths occurred; none were procedure-related. ConclusionsINA achieves improved arrhythmia control in 78% of patients with PVCs and avoids hospitalization in 69% of patients with VT refractory to standard ablation at 6-month follow-up. Procedural risks are acceptable. (Intramural Needle Ablation for Ablation of Recurrent Ventricular Tachycardia, NCT01791543; Intramural Needle Ablation for the Treatment of Refractory Ventricular Arrhythmias, NCT03204981)

Frequency of Ventricular Tachycardia in First 48 Hours of ST-Elevation Myocardial Infarction

ST-elevation myocardial infarction (STEMI) has a poor long-term prognosis associated with early ventricular tachycardia (VT). Objective: To find out the frequency of ventricular tachycardia in the first 48 hours of ST-elevation myocardial infarction. Methods: After approval from the Hospital ethical committee, the study was conducted in the department of cardiology Hayatabad medical complex Peshawar from 1st October 2020 to 31st March 2021. All the patients having new onset ST-elevation Myocardial infarction as per Operational definition, both genders, aged between 40 and 75 years and who have given consent were included in the study. Non-probability consecutive sampling technique is being used for the sampling. Results: Standard deviation was ±1.357 years, while the average age was 51.56. Gender-wise distribution among patients male was 89(53.6%) and female was 77(46.4%). Distribution of duration of disease among patients 12-24 hours 80(48.2%) and more than 24 hours 86(51.8%) was 100(52.4%). Family History of coronary artery disease (CAD) 84(50.6%), diabetes mellitus 93(56.0%), hypertension 110(66.3%) and smoking status was 118(71.1%). Distribution of ventricular tachycardia was present among 103(62.0%) patients and was absent in 63(38.0%) patients. Conclusions: Ventricular tachycardia is the most common tachycardia occurring in patients in the first 48 hours who sustained myocardial infarction. It was shown that bradyarrhythmia was more common in patients with inferior wall myocardial infarction while ventricular tachycardia was found to be more in patients with anterior wall myocardial infarction.

Abstract 10988: The Dynamic Duo of Electrical and Thyroid Storm Caused by Amiodarone

Case description: A 61 year-old male with a hx of CAD s/p CABG and HFrEF s/p AICD presents with a 4-day history of dizziness and shortness of breath; he was found to be in ventricular tachycardia (VT) storm. ICD interrogation was found to have 13 shocks in 24 hours. His thyroid function tests (TFT) were abnormal: TSH undetectable, elevated FT4 7.7 (0.93-1.7) and T3 246.6 (84-202) ng/dL, respectively. He was diagnosed with severe thyrotoxicosis, likely due to amiodarone-induced thyrotoxicosis (AIT) type 2 and a Burch-Wartofsky score of 50, highly suggestive of thyroid storm (TS). He was started on hydrocortisone, prednisone, propylthiouracil, and metoprolol for the TS. Procainamide drip had been initiated for VT and titrated until VT was controlled. Repeat TFTs in 48 hours showed no changes in TSH or FT4, but T3 had normalized. Procainamide and hydrocortisone were discontinued after VT frequency had decreased. Discussion: An electrical storm (ES) is a state of electrical instability characterized by multiple episodes of VT in 24 hours. In patients with ICD, it is defined as &gt;3 anti-tachycardic pacing therapies or shock. Most patient with ES have severe underlying structural heart disease with various inciting events such as thyrotoxicosis. Amiodarone is the drug of choice in VT; however, complications such as AIT should be recognized. Thyroid hormone has a direct arrhythmogenic effect on the heart through various cellular mechanisms. In our patient, amiodarone was discontinued after the diagnosis of AIT. Procainamide and antithyroid therapy were started, which subsequently controlled the VT. Resistance to therapy can occur, and more elaborate interventions such as plasmapheresis are an option to remove amiodarone, its metabolites, and free thyroid hormones. Conclusion: Amiodarone is the most efficacious medication for VT. However, it is important to recognize possible life-threatening complications of this medication, such as AIT, which itself can exacerbate VT.

Abstract 11402: Targeting RyR2 to Suppress Ventricular Arrhythmias and Improve Left Ventricular Function in Chronic Ischemic Heart Disease

Introduction: Sarcoplasmic reticulum Ca +2 leak from RyR2 is a common finding in chronic ischemic heart disease (CIHD) and may be a key driver for ventricular arrhythmias and reduced excitation-contraction coupling in failingm myocytes. Here, we test the hypothesis that targeting Ca +2 leak using the non-selective RyR inhibitor, Dantrolene, suppresses ventricular arrhythmias and improves left ventricular contractile function in CIDH. Methods: CHID was induced in 24 C57BL/6J mice by left coronary artery ligation. Four weeks after myocardial infarction (MI), subcutaneous osmotic pumps were placed to deliver continuous dantrolene (20 mg/kg/day) or vehicle (0.9% Saline). Left ventricular (LV) function was assessed by echocardiogram at 4-, 7- and 10-weeks post-MI. Peripheral muscle strength was assessed by provoked electromyogram at 6 weeks. Inducibility of ventricular tachycardia (VT) was assessed by rapid transesophageal pacing with isoproterenol at 10 weeks. Results: Dantrolene reduced the peripheral muscle strength in mice (0.014±0.001 vs 0.010±0.001 N, P&lt;0.05), but had no adverse effects on weight loss or mortality. Dantrolene increased fractional shortening (18.7±1.3% vs 22.1±1.6%, P&lt;0.001) and mean velocity fiber shortening (mVcfc 1.37±0.09 vs 1.74±0.1 circ/sec, P&lt;0.002) in non-infarcted regions at 10 weeks. This prevented the progression in LV ejection fraction reduction from 4 to 10 weeks (Saline: 35.6±3.4% to 30.6%±3.4%; Dantrolene 34.6±2.4% to 38.1±1.9% vs, P&lt;0.01). Dantrolene reduced VT frequency per animal (0.083±0.04 vs 0.028±0.02 VT/pacing train, P&lt;0.02) and the total duration of inducible VT per animal (59.2±24 secs vs 1.2±0.6 sec, P&lt;0.04). Dantrolene significantly prolonged the ventricular effective refractory period (VERP) (35.1±1.6 msec vs 42.0±0.9 msec, P&lt;0.005). Conclusion: Dantrolene suppression of RyR2 diastolic Ca +2 leak in chronic ischemic heart failure improves the systolic function of surviving myocardium and reduces VT burden by prolonging the VERP, preventing the re-entry circuit for VT in this model. RyR2 inhibition may represent a new therapeutic target for the treatment of CIDH with ventricular arrhythmias.

Prognostic factors in patients with acute myocardial infarction underwent extracorporeal membrane oxygenation in hospital or out-of-hospital cardiac arrest

Abstract Background Patients with acute myocardial infarction (AMI) who require extracorporeal membrane oxygenation (ECMO) have worse outcomes than those who do not, and patients with AMI with out-of-hospital cardiac arrest (OHCA) also have worse outcomes than those without OHCA. However, there have been still unclear points regarding the prognostic factors of AMI patients who underwent ECMO with or without OHCA. The aim of this study was to investigate the prognostic factors of AMI patients who underwent ECMO with and without OHCA, respectively. Methods/Results Ninety-eight consecutive patients (age:67±11 years, male:83.7%) who underwent ECMO for AMI were enrolled from November 2008 to December 2020. The primary endpoint was in-hospital mortality within 30-day, and we investigated the risk factors associated with 30-day mortality in AMI patients underwent ECMO with or without OHCA, respectively. In the group with OHCA (n=47), 30-day death occurred in 22 patients (47%). BMI, lactate and serum creatinine levels after the introduction of ECMO were significantly greater in patients with than without 30-day death (27.0±5.2 vs 21.0±2.9 kg/m2, p&amp;lt;0.001, 12.1±4.3 vs 7.5±3.6 mmol/L, p&amp;lt;0.001, 1.68±1.24 vs 1.41±1.07 mg/dL, p=0.039, respectively). The multivariate regression analysis showed that lactate level was independently associated with the poor outcome (Odds ratio: 1.32, 95% CI: 1.11–1.57, p&amp;lt;0.001). ROC curve analysis showed that the cut-off values: 7.8mmol/L of lactate had moderate accuracy to predict 30-day mortality (sensitivity:76%, specificity:86%, AUC:0.81). In the group without OHCA (n=51), 30-day death occurred in 20 patients (39%). The frequency of ventricular tachycardia / fibrillation (VT/VF) at initiation of ECMO was significantly higher (61.3% vs 25.0%, p=0.021), the frequency of mechanical complication was significantly lower (6.5% vs 30.0%, p=0.045) in patients without 30-day death than with 30-day death. The multivariate regression analysis showed that VT/VF at initiation of ECMO was independently associated with good outcome (Odds ratio: 0.21, 95% CI: 0.06–0.73, p=0.01). Conclusions With OHCA, increased lactate was the risk factor that was significantly associated with poor outcome in AMI patients underwent ECMO. Without OHCA, AMI patients who underwent ECMO due to rhythm trouble such as VT/VF had a good outcome. ECMO patients with AMI may have different prognostic factors with or without OHCA. Funding Acknowledgement Type of funding sources: None. Patient characteristics

Surgical cardiac sympathetic denervation in patients with VT storm: long term follow-up data

Abstract Background Surgical Cardiac Sympathetic Denervation (CSD) is a procedure which involves surgical removal of terminal cervical and thoracic sympathetic ganglion for reducing sympathetic discharge to the heart. CSD is usually performed as a last desperate measure in treatment of ventricular tachycardia (VT). We report here the clinical profile and long-term follow-up of all our patients who underwent CSD (unilateral or bilateral) predominantly upfront prior to considering catheter ablation of VT for VT storm. Material and methods We retrospectively collected data of all patients who underwent CSD for VT storm between year 2010 till 2019. Success of CSD was defined as successful discharge of patient from the hospital after the procedure more than 75% decrease in the frequency of VT after two weeks of surgical procedure. Results A total of 65 patients underwent CSD in the above-mentioned period and the average duration of follow-up was 28 months. The clinical parameters, demographic data and outcome analysis is provided in details in table 1. Only 14 (21.5%) patients underwent attempt of catheter ablation of VT prior to considering CSD. CSD was successful in 53 (81.5%) of patients. There was a significant decline in the incidence of number of ICD or external shocks before and after CSD (25.2±39.4 vs 1.09±2.9) respectively. There was no significant effect of CSD on ejection fraction. None of the available clinical parameters predicted the success of CSD. Discussion and conclusion The current retrospective analysis reemphasize the role of surgical CSD in treatment of patients with VT storm. As in predominant patient's CSD was performed even before the attempting catheter-based ablation, it brings in a new dimension in the treatment of VT. Efficacy of CSD (81.5%) in experienced hand is equivalent or even better than catheter-based ablation in patients with VT storm. Funding Acknowledgement Type of funding source: None

Poor Sleep Quality Associated With High Risk Of Ventricular Tachycardia After Acute Myocardial Infarction.

BackgroundSleep disorders (SDs) are usually associated with an increase in frequency of ventricular tachycardia (VT). However, the relationship between SDs and the prevalence of VT within the first week of acute myocardial infarction (AMI) remains unclear. This study aimed to evaluate their associations and potential mechanisms.MethodsThis structured questionnaire-based cross-sectional study enrolled 303 patients with AMI from a hospital in northern China. Pittsburgh Sleep Quality Index (PSQI) was used to determine sleep quality of subjects. Heart rate variability (HRV) of patients was investigated by ambulatory electrocardiography recorders. Enzyme-linked immunosorbent assay was used to measure the plasma levels of catecholamine in a subgroup including 80 patients with AMI.ResultsAfter adjusting to basic cardiovascular characteristics, results of multivariate logistic regression demonstrated that the global PSQI score and its main components were positively associated with VT prevalence in inpatients with AMI. There were significantly different HRV parameters interpreted as autonomic nerve activity in two groups of AMI patients with different sleep quality. In addition, we found the influence of sleep quality on plasma concentrations of adrenaline and norepinephrine in AMI patients.ConclusionSleep status was significantly associated with the initiation of VT within the first week of AMI, probably due to the effect of SDs on sympathetic nerve activity. Amelioration of sleep quality and sympathetic hyperactivity may be prospective strategy to curb arrhythmias after AMI.

Prevalence and prognostic significance of prolonged QTc interval in emergency medical patients: A prospective observational study.

Introduction:QTc interval is affected by many factors and prolongation of same may have prognostic significance. A significant number of patients admitted in medical emergency are acutely ill, have multiple comorbidities and are on medications, all of these factors might affect QTc interval and prognosis.Materials and Methods:Single-center, prospective, observational study was carried out on 279 patients of different illnesses recruited from emergency medical services attached to the Department of Internal Medicine at Postgraduate Institute of Medical Education and Research, Chandigarh, India, a tertiary care hospital.Results:Out of 279 patients, 95 were found to have prolonged QTc interval with the prevalence of 34.1%. Fifteen patients (5.4%) had markedly prolonged QTc interval (QTc >500 ms). Of various medical conditions, we found statistically significantly higher number of patients of chronic kidney disease (P = 0.047), chronic liver disease (P < 0.001), hemorrhagic cerebrovascular accident (P = 0.026), and heart failure (P = 0.009) with prolonged QTc interval. Among laboratory abnormalities, patients with low hemoglobin (P = 0.032), with deranged renal functions (P = 0.033), and with hypokalemia (P = 0.026) had a greater share of patients with prolonged QTc interval. There was no difference in duration of hospital stay and frequency of hospital mortality between two groups, although, on subgroup analysis, patients with markedly prolonged QTc interval had significantly higher hospital mortality (P = 0.029). The frequency of ventricular tachycardia was also significantly higher in patients with prolonged QTc interval (P = 0.008).Conclusion:High prevalence of prolonged QTc interval was found in Indian emergency medical patients. There was no difference in hospital mortality though on subgroup analysis, patients with markedly prolonged QTc interval had significantly more episodes of in-hospital ventricular tachycardia and hospital mortality.

Chronic obstructive pulmonary disease as a risk factor for ventricular arrhythmias independent of left ventricular function

The association between chronic obstructive pulmonary disease (COPD) and sudden cardiac death has not been fully elucidated. The purpose of this study was to investigate whether decreased left ventricular ejection fraction (LVEF) can explain the increased rate of ventricular tachycardia (VT) in COPD. This retrospective study included consecutive adult patients who underwent pulmonary function testing (PFT), Holter monitoring, and transthoracic echocardiography. COPD was correlated with the frequency of VT in a multivariate analysis that adjusted for known confounders including LVEF. Long-term all-cause mortality of patients with COPD and VT was examined. Of the 6351 patients included in this study (age 66 ± 15 years; 48% woman; 92% Caucasian, LVEF 59% ± 12%), 2800 (44%) had PFT indicative of COPD. VT was nearly twice as likely to occur during Holter monitoring in COPD patients (13% vs 23%; P<.001), and the severity of COPD correlated with the risk of VT (21% vs 28% vs 37% for mild-moderate, severe, and very severe COPD; P <.001). COPD and VT remained independently associated (P <.001) even after adjusting for LVEF, demographics, and comorbidities (age, sex, body mass index, hypertension, chronic kidney disease, coronary artery disease, cancer history, diabetes mellitus). COPD was associated with all-cause mortality independently of LVEF (P <.001). COPD patients are at higher risk for VT and mortality. This may not be fully attributed to the confounding effect of systolic heart failure measured by LVEF. Further studies are needed to explore the mechanistic interactions between VT and COPD in order to determine whether antiarrhythmic strategies would apply especially to patients with severe COPD.

Ibutilide Effectiveness and Safety in the Cardioversion of Atrial Fibrillation and Flutter in the Community Emergency Department

Little is known about the use of ibutilide for cardioversion in atrial fibrillation and flutter outside of clinical trials. We seek to describe patient characteristics, ibutilide administration patterns, cardioversion rates, and adverse outcomes in the community emergency department (ED) setting. We also evaluate potential predictors of cardioversion success. Using a retrospective cohort of adults who received ibutilide in 21 community EDs between January 2009 and June 2015, we gathered demographic and clinical variables from electronic health records and structured manual chart review. We calculated rates of cardioversion and frequency of ventricular tachycardia within 4 hours and estimated adjusted odds ratios (aOR) in a multivariate regression model for potential predictors of cardioversion. Among 361 patients, the median age was 61 years (interquartile range 53 to 71 years) and most had recent-onset atrial fibrillation and flutter (98.1%). Five percent of the cohort had a history of heart failure. The initial QTc interval was prolonged (>480 ms) in 29.4% of patients, and 3.1% were hypokalemic (<3.5 mEq/L). The mean ibutilide dose was 1.5 mg (SD 0.5 mg) and the rate of ibutilide-related cardioversion within 4 hours was 54.8% (95% confidence interval [CI] 49.6% to 60.1%), 50.5% for atrial fibrillation and 75.0% for atrial flutter. Two patients experienced ventricular tachycardia (0.6%), both during their second ibutilide infusion. Age (in decades) (aOR 1.3; 95% CI 1.1 to 1.5), atrial flutter (versus atrial fibrillation) (aOR 2.7; 95% CI 1.4 to 5.1), and no history of atrial fibrillation and flutter (aOR2.0; 95% CI 1.2 to 3.1) were associated with cardioversion. The effectiveness and safety of ibutilide in this community ED setting were consistent with clinical trial results despite less stringent patient selection criteria.

Long-Term Success of Irrigated Radiofrequency Catheter Ablation of Sustained Ventricular Tachycardia: Post-Approval THERMOCOOL VT Trial

BackgroundRadiofrequency catheter ablation is used to treat recurrent ventricular tachycardia (VT). ObjectivesThis study evaluated long-term safety and effectiveness of radiofrequency catheter ablation using an open-irrigated catheter. MethodsPatients with sustained monomorphic ventricular tachycardia associated with coronary disease were analyzed for cardiovascular-specific adverse events within 7 days of treatment, hospitalization duration, 6-month sustained monomorphic ventricular tachycardia recurrence, quality of life measured by the Hospital Anxiety and Depression Scale, long-term (1-, 2-, and 3-year) survival, symptomatic VT control, and amiodarone use. ResultsOverall, 249 patients, mean age 67.4 years, were enrolled. The cardiovascular-specific adverse events rate was 3.9% (9 of 233) with no strokes. Noninducibility of targeted VT was achieved in 75.9% of patients. Post-ablation median hospitalization was 2 days. At 6 months, 62.0% (114 of 184) of patients had no sustained monomorphic ventricular tachycardia recurrence; the proportion of patients with implantable cardioverter-defibrillator shocks decreased from 81.2% to 26.8% (p < 0.0001); the frequency of VT in implantable cardioverter-defibrillator patients with recurrences was reduced by ≥50% in 63.8% of patients; and the proportion with normal Hospital Anxiety and Depression Scale scores increased from 48.8% to 69.1% (p < 0.001). Patient-reported VT remained steady for 1, 2, and 3 years at 22.7%, 29.8%, and 24.1%, respectively. Amiodarone use and hospitalization decreased from 55% and 77.2% pre-ablation to 23.3% and 30.7%, 18.5% and 36.7%, 17.7% and 31.3% at 1, 2, and 3 years, respectively. ConclusionsRadiofrequency catheter ablation reduced implantable cardioverter-defibrillator shocks and VT episodes and improved quality of life at 6 months. A steady 3-year nonrecurrence rate with reduced amiodarone use and hospitalizations indicate improved long-term outcomes. (NaviStar ThermoCool Catheter for Endocardial RF Ablation in Patients With Ventricular Tachycardia [THERMOCOOL VT]; NCT00412607)

Aconite poisoning with arrhythmia and shock

A 55-year-old male presented with history of nausea, vomiting, palpitation paresthesis and profuse sweating in emergency department 2h after ingestion of “Bachnaag” (Aconite) root. Examination revealed shock with irregular pulses. Initial ECG showed frequent multifocal ventricular ectopics (VE), which later turned to short runs of ventricular tachycardia (VT). Immediate gastric lavage was done and activated charcoal given. Patient was treated with fluid resuscitation without any improvement in blood pressure. Patient was started on nor-adrenaline infusion with gradual recovery from hypotension over a period of 6h, but support was continued for 48h. Amiodarone was started to control ventricular excitability, which persisted over 72h with gradual decrease in frequency of VT and VE. Patient was discharged with normal sinus rhythm on oral amiodarone on 5th day of hospitalization. On follow-up after 2 weeks patient was totally asymptomatic and amiodarone was stopped.

Enhancement of intracardiac navigation by new GPS-guided location system (MediGuide Technologies)

Ventricular tachycardia in patients with structural heart disease is a clinical relevant arrhythmogenic disorder. Many of these patients require a combination of implantable cardioverter-defibrillator (ICD) for prevention of sudden cardiac death with antiarrhythmic medications to decrease the frequency of ventricular tachycardia (VT) episodes. However, ICD cannot prevent arrhythmia episodes and medication has only limited efficacy and in relevant number of patients it has to be discontinued due to multiple side effects. Severalreportsinthelastdecadehaveshownthatinpatientswith frequently recurrent ventricular arrhythmia episodes catheter ablation can be a highly effective therapy as an adjunct to ICD and/or medical treatment. In addition, the SMASH-VT and VTACH trials demonstrates, that prophylactic VT ablation results in a prolonged time to recurrence of VT in patients with stable VT, previous myocardial infarction, and reduced left ventricular ejection fraction. 1,2 According to this data it is hardlysurprising that, besides atrialfibrillation ablation, treatment of ventricular tachycardia is the next big frontier in the field of interventional therapy of cardiac arrhythmias. However, management of ventricular tachycardia is still challenging driven by a complex three-dimensional substrate. Successful treatment requires a comprehensive understanding and visualization of cardiac anatomy and electrical activation. Beside conventional fluoroscopy, 3-D electromagnetic mapping systems have been introduced to facilitate catheter navigation. Currently used techniques have some weaknesses. For instance, fluoroscopy provides only two-dimensional information, where it is difficult to repeatedly guide the catheter to the same area of interest. Thus, with prolonged procedures there is an increased X-ray exposure, adding risk for both the patient and the physician. One limitation of available 3-D-mapping system is failing to sufficiently compensate for respiratory, cardiac cycle, and patient movement and the limited integration on fluoroscopy. Recently, a new intracardiac navigation system (MediGuide TM System) was introduced to overcome this limitation and to merge the key benefits of fluoroscopy and 3-D-mapping system in a unique manner. In the following we are going to introduce this technology and present potential implications on interventional treatment of ventricular arrhythmias.

Function of the CaMKII-ryanodine receptor signaling pathway in rabbits with left ventricular hypertrophy and triggered ventricular arrhythmia.

Calcium calmodulin-dependent kinase II (CaMKII) can be more active in patients with left ventricular hypertrophy (LVH), which in turn causes phosphorylation of ryanodine receptors, resulting in inactivation and the instability of intracellular calcium homeostasis. The present study aimed to determine the effect of CaMKII-ryanodine receptor pathway signaling in rabbits with left ventricular hypertrophy and triggered ventricular arrhythmia. Forty New Zealand rabbits were randomized into four groups (10 per group): sham group, LVH group, KN-93 group (LVH+KN-93), and ryanodine group (LVH+ryanodine). Rabbits in the LVH, KN-93, and ryanodine groups were used to establish a left ventricular hypertrophy model by the coarctation of the abdominal aorta, while those in the sham group did not undergo the coarctation. After eight weeks, action potentials (APs) were recorded simultaneously in the endocardium and epicardium, and a transmural electrocardiogram (ECG) was also recorded in the rabbit left ventricular wedge model. Drugs were administered to the animals in the KN-93 and ryanodine groups, and the frequency of triggered APs and ventricular tachycardia was recorded after the rabbits were given isoprenaline (1 μmol/L) and high-frequency stimulation. The frequency (animals/group) of triggered APs was 0/10 in the sham group, 10/10 in the LVH group, 4/10 in the KN-93 group, and 1/10 in the ryanodine group. The frequencies of ventricular tachycardia were 0/10, 9/10, 3/10, and 1/10, respectively. The frequencies of polymorphic ventricular tachycardia or ventricular fibrillation were 0/10, 7/10, 2/10, and 1/10, respectively. The frequencies of triggered ventricular arrhythmias in the KN-93 and ryanodine groups were much lower than those in the LVH group (P<0.05). KN-93 and ryanodine can effectively reduce the occurrence of triggered ventricular arrhythmia in rabbits with LVH. The CaMKII-ryanodine signaling pathway can be used as a new means of treating ventricular arrhythmia.

Part 13: First Aid

Part 13: First Aid

Cardiac Magnetic Resonance Detection of Myocardial Scarring in Hypertrophic Cardiomyopathy: Correlation With Histopathology and Prevalence of Ventricular Tachycardia

In hypertrophic cardiomyopathy (HCM) patients undergoing surgical myectomy, we sought to determine the association between pre-operative cardiac magnetic resonance (CMR) findings, small intramural coronary arteriole dysplasia (SICAD) on histopathology, and ventricular tachycardia (VT). Myocardial scarring (fibrosis) and SICAD are frequently observed on histopathology in HCM patients. CMR measures wall thickness and detects scar. Sixty symptomatic HCM patients (62% men; mean age 51 +/- 14 years), with preserved ejection fraction (mean 64 +/- 5%) and no angiographic coronary disease underwent CMR (cine and delayed post-contrast) using a Siemens 1.5 T scanner, followed by septal myectomy. Maximal basal septal thickness was recorded on cine CMR. Scar was determined (percentage of total myocardium) on delayed post-contrast CMR images and quantified as none, mild (0% to 25%), moderate (26% to 50%), or severe (>50%). VT was assessed using Holter monitoring. Degree of SICAD was determined (normal, mild, moderate, and severe) on histopathology of surgical specimen. SICAD and scar were seen in 45 (75%) and 38 (63%) patients, respectively. In 15 patients without SICAD, 12 (80%) had no scar; 23 (70%) patients with mild SICAD had mild scar on CMR. On multivariate analysis, degree of SICAD was independently associated with scar on CMR (Wald chi-square statistic: 6.8, p < 0.01). Patients with basal septal scar on CMR had higher VT frequency compared with those without (27% vs. 5%, p = 0.03). A strong association exists between degree of SICAD and myocardial scarring seen on CMR.

Short‐Long Sequences Prior to Ventricular Tachycardia Onset: Analysis of VAST Trial Electrograms

The recently published Ventricular Arrhythmia Suppression Trial (VAST) found no effect of rate-smoothing (RS) algorithm on frequency of ventricular tachycardia (VT) episodes in patients with implantable defibrillator. A similar recent trial reported an opposite result. In order to determine possible reasons for the discrepancy between the trials and achieve better understanding of events preceding VT onset, we analyzed stored device electrograms preceding 162 VT episodes from 50 VAST trial patients with dual-chamber devices. In this analysis, short-long sequences were more common prior to polymorphic VTs than before monomorphic VTs. The proportion of VT episodes preceded by short-long sequences was lower during randomization to RS ON (5.3% vs 31.3%, P < 0.001). For patients with multiple episodes of monomorphic VT, there was higher interpatient than intrapatient variability in preceding RR intervals. When adjusting for this similarity of RR interval sequences preceding VT onset in individual patients, the difference in proportion short-long sequences between RS ON and RS OFF programming was no longer significant. Episodes of VT were preceded by stereotypic, patient-specific sequences of RR intervals in several VAST trial patients. RS reduced the percentage of VTs preceded by short-long sequences, but did not change overall VT incidence.

Comprehensive Analyses of Arrhythmogenic Substrates and Vulnerability to Ventricular Tachycardia in Left Ventricular Hypertrophy in Salt-Sensitive Hypertensive Rats

The contribution of conduction disturbances to susceptibility to ventricular tachycardia (VT) has not been directly examined in the process of left ventricular hypertrophy (LVH). Dahl salt-sensitive (S) and -resistant rats were raised on a high-salt diet. After echocardiography, a fractionation study was conducted using wavelet transform analysis, which reflects conduction disturbances, recording of monophasic action potential (MAP), measurement of conduction velocity, and programmed extrastimuli for the induction of VT, as well as patch-clamp analysis at 10, 13 and 16 weeks (W) (n=7, each). Systolic blood pressure, wall thickness and MAP duration significantly increased at 10W in S rats, whereas conduction velocity decreased and MAP duration and the power of wavelet transform increased at 13W and 16W. Paired extrastimuli induced polymorphic VT only at 13W and 16W in S rats. VT frequency correlated inversely with conduction velocity and positively with MAP duration. Power of wavelet transform correlated negatively with conduction velocity and positively with VT vulnerability. The patch-clamp study revealed that the action potential duration significantly increased in S rats with aging, and correlated with MAP duration. Latently progressing slow and inhomogeneous conduction, as well as a repolarization abnormality, may contribute to VT vulnerability in hypertensive LVH.