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QRS interval [keywords]
- A new formula for the evaluation of the QT-interval in patients with left bundle branch block. [JOURNAL ARTICLE]
- Heart Rhythm 2014 Aug 19.
Left-bundle-branch-block(LBBB) and QT-prolongation are both associated with a worse prognosis. LBBB lengthens the QT-interval. So far it is not known if QT-time prolongation during LBBB differs in repolarization from QT-time prolongation during narrow QRS.The aim of the present proof-of-concept-study is therefore to develop a formula that allows to compare the adjusted QT-interval during LBBB with reference values and thereby allow interpretation of the QT-interval irrespective of the QRS-widening.60 consecutive patients with sinus-rhythm(SR) and narrow-QRS underwent an EP-study for ablation. In all patients the intrinsic QRS-,QT- and JT-time was measured during SR and ventricular-pacing from the right-ventricular-apex(RVA) and outflow-tract(RVOT) both causing a LBBB. We determined the prolongation of the QT during as compared to SR(ΔQT). ΔQT was then divided by the QRS-length during paced-QRS(QRSb). This describes the percentage of the QRS-duration at LBBB, which must be subtracted from the measured QT(QTb), to determine the modified-QT(QTm).The ratio of ΔQT to paced-QRS was calculated as 48,3%(RVA) and 48.8%(RVOT)[mean 48.5%]. The ratio intrinsic-JTi to paced-JT was 1.0055 (RVA) and 1.0087(RVOT). There was no significant difference in intrinsic-JT vs. paced-JT(p=0.2) CONCLUSION: Right-ventricular-pacing causes a prolongation of the QT due to a paced-LBBB without prolongation of the JT-time. In our study, we have shown that the QT-prolongation caused by the LBBB amounts 48.5% of the QRS-width. This is the value that must be subtracted from the measured QT in LBBB in order to estimate the modified-QT. The resulting Formula for "modified-QT" estimation in LBBB is: QTm = QTb - 48,5%*(QRSb).
- Echocardiographic and clinical response to cardiac resynchronization therapy in heart failure patients with and without previous right ventricular pacing. [JOURNAL ARTICLE]
- Eur J Heart Fail 2014 Jul 31.
Right ventricular pacing (RVp) results in an electrocardiographic left bundle branch block pattern and can lead to heart failure. This study aimed to evaluate echocardiographic and clinical outcomes of heart failure patients with RVp upgraded to cardiac resynchronization therapy (CRT), as they are frequently excluded from multicentre studies.This observational study assessed 655 consecutive patients with QRS ≥120 ms and left ventricular ejection fraction ≤35%. There were 465 patients without significant previous RVp and 190 with RVp >40%. Echocardiograms were analysed pre-CRT and ∼ 1 year post-CRT. Death and heart failure hospitalizations were analysed using Cox regression, adjusted for baseline characteristics. The RVp patients had smaller end-systolic volume (P = 0.002), were older (P < 0.001), and had more atrial fibrillation (P < 0.001) pre-CRT. Ejection fraction and proportion of ischaemic aetiology were similar. One year following CRT implantation the ejection fraction response was greater in the RVp group (8.3 ± 9 vs. 5.8 ± 9 units, P = 0.005). The RVp patients had an adjusted 33% lower risk of death or heart failure hospitalization [hazard ratio (HR) 0.67 95% confidence interval (CI) 0.51-0.89, P = 0.005], while tending to have an adjusted lower risk of death (HR 0.73 95% CI 0.53-1.01, P = 0.055).Despite similar ejection fraction pre-CRT, patients upgraded to CRT with previous RVp have smaller end-systolic volume and respond to CRT at least as well as, if not better than, other wide QRS heart failure patients. A greater improvement in ejection fraction and a lower risk of death or heart failure hospitalization when adjusted for baseline characteristics were seen in those with previous RVp.
- Delayed QRS Transition in the Precordial Leads of an Electrocardiogram as a Predictor of Sudden Cardiac Death in the General Population. [JOURNAL ARTICLE]
- Heart Rhythm 2014 Aug 12.
QRS transition zone is related to the electrical axis of the heart in the horizontal plane, and is easily determined from the precordial leads of a standard 12-lead ECG. However, it is unclear whether delayed QRS transition, or clockwise rotation of the heart, carries prognostic implications and predicts sudden cardiac death (SCD).To study whether delayed transition is associated with mortality and SCD.We evaluated 12-lead ECGs of 10815 Finnish middle-aged subjects from the general population (52% men, mean age 44±8.5 years) and followed them for 30±11 years. Main endpoints were mortality and SCD.Delayed QRS transition at lead V4 or later occurred in 1770 (16.4%) subjects, and markedly delayed transition at lead V5 or later in 146 (1.3%) subjects. Delayed transition zone was associated with older age, male gender, higher BMI, hypertension, baseline cardiovascular disease, leftward shift of the frontal QRS axis, wider QRS-T angle, and electrocardiographic LVH. After adjusting for several clinical and ECG variables, delayed transition was associated with overall mortality (HR 1.15; 95%CI 1.07-1.22; P<0.001) and SCD (HR 1.23; 95%CI 1.03-1.47; P=0.029). Markedly delayed transition at V5 or later predicted significantly SCD (HR 1.89; 95%CI 1.18-3.03; P=0.008) and all-cause mortality (HR 1.30; 95%CI 1.07-1.58; P=0.01). However, further adjustments for repolarization abnormalities attenuated this effect.Delayed QRS transition in the precordial leads of an ECG seems as a novel electrocardiographic risk marker for SCD. Especially markedly delayed transition was associated with significantly increased risk of SCD, independent of confounding factors.
- Left ventricular pacing in neonates and infants with isolated congenital complete or advanced atrioventricular block: short- and medium-term outcome. [JOURNAL ARTICLE]
- Europace 2014 Aug 12.
Right ventricular (RV) pacing may induce left ventricular (LV) dysfunction: neonates and infants with isolated congenital complete/advanced atrioventricular block (CCAVB) are at high risk of developing RV pacing-induced LV dyssynchrony, remodelling, and dysfunction. We prospectively investigated whether LV pacing results in normal LV function and good clinical status in the short/medium term.In this single-centre, prospective study, 10 consecutive patients with CCAVB (median age 4 months, range: 0.1-16) underwent pacemaker implantation (4 VVIR, 6 DDD) using epicardial leads (on the LV apex in 8, on the LV free wall in 2). Data were collected at implantation and at 1- and 12-month follow-up. Echocardiographic evaluation included two-dimensional/three-dimensional assessment of LV dimensions, function (ejection fraction, EF), and ventricular synchrony (interventricular and intraventricular dyssynchrony). Prior to pacemaker implantation, EF was normal in six patients, 50% in two, ≤40% in two. All patients showed good clinical status and normal LV dimensions at follow-up. Patients with LV dilatation and impaired EF at implantation showed LV reverse remodelling and enhanced LV function. Normal LV function and synchrony were observed in most patients (one patient with EF 53% and three patients with mild dyssynchrony at 12-month follow-up). Paced QRS complex tended to be wider than native QRS complexes (P = 0.07); QTc duration of paced complexes was within normal limits or only slightly prolonged, without significant differences compared with QTc interval of native complexes.At short- and medium-term follow-up, LV pacing results in satisfactory LV electromechanical function and synchrony in neonates and infants with CCAVB.
- Ventricular Arrhythmias near the Distal Great Cardiac Vein: A Challenging Arrhythmia for Ablation. [JOURNAL ARTICLE]
- Circ Arrhythm Electrophysiol 2014 Aug 10.
-Catheter ablation (CA) for ventricular arrhythmia (VA) near the distal great cardiac vein (GCV) is often challenging and data are limited.-Analysis was performed of 30 patients (19 male; age 52.8±15.5 years) who underwent CA for focal VA (11 ventricular tachycardia, 19 premature contractions) with early activation in the GCV (36.7±8.0 ms pre-QRS). Angiography in 27 patients showed earliest GCV site within 5 mm of a coronary artery in 20 (74%). Ablation was performed in the GCV in 15 patients and abolished VA in 8. Ablation was attempted at adjacent non-GCV sites in 19 patients and abolished VA in 5 patients (4 from the left ventricular endocardium and 1 from the left coronary cusp); all success had VA with an initial r wave in lead I and activation ≤7 ms after the GCV (GCV-nonGCV interval). In 13 patients percutaneous epicardial mapping was performed, but due to adjacent coronaries only 2 received radiofrequency application with VA elimination in 1. Surgical cryoablation was performed in 3 patients and abolished VA in 2. Overall acute success was achieved in 16 (53%) patients. After a median of 2.8 months, 13 patients remained free of VA. Major complications occurred in 4 patients including coronary injury requiring stenting.-Ablation for this arrhythmia is challenging and often limited by the adjacent coronary vessels. Success of anatomically guided endocardial ablation may be identified by a short GCV-nonGCV interval and r wave in lead I.
- Effects of combined netupitant and palonosetron (NEPA), a cancer supportive care antiemetic, on the ECG of healthy subjects: an ICH E14 thorough QT trial. [Journal Article]
- Springerplus 2014.:389.
Chemotherapy-induced nausea and vomiting is ranked among the worst side effects of chemotherapy. NEPA is an oral fixed-dose combination antiemetic under development, consisting of netupitant 300 mg, a highly selective NK1 receptor antagonist (RA), and palonosetron 0.5 mg, a pharmacologically and clinically distinct 5-HT3 RA. Although palonosetron is not associated with relevant ECG effects, this study evaluated cardiovascular safety of netupitant in combination with palonosetron, as well as its tolerability. This randomised, placebo- and positively controlled study in 197 subjects included 4 treatment groups: placebo, 200 mg netupitant + 0.5 mg palonosetron (NEPA200/0.5), 600 mg netupitant + 1.5 mg palonosetron (NEPA600/1.5, a supratherapeutic dose), and 400 mg moxifloxacin. Assessments included a 24-h baseline ECG recording, followed by a single dose of treatment and ECG measurements for 2 days. Mean placebo-corrected time-averaged changes from baseline were similar in NEPA200/0.5 and NEPA600/1.5 groups primarily for individually heart rate-corrected QT interval (QTcI: +4.7 and +3.6 ms, respectively) and for heart rate (HR: -3.3 bpm and -3.0 bpm), PR interval (-0.4 ms and 0.2 ms), and QRS interval (1 ms and 0.5 ms). The time-matched analysis showed no upper confidence interval >10 ms, with no suggestion of a QTc effect by pharmacokinetic-pharmacodynamic modeling for parent/metabolites. Moxifloxacin showed the expected placebo-corrected change from baseline (+8.4 ms time average) and the expected profile to establish assay sensitivity. No new morphologic changes of clinical relevance were observed. Treatment-related adverse events were comparable among groups. This study showed that NEPA treatments produced no significant effects on QTcI, HR, PR interval, QRS interval, and cardiac morphology relative to placebo, even at supratherapeutic doses.
- Incidence of and risk factors for sick sinus syndrome in the general population. [Journal Article]
- J Am Coll Cardiol 2014 Aug 12; 64(6):531-8.
Little is known about the incidence of and risk factors for sick sinus syndrome (SSS), a common indication for pacemaker implantation.This study sought to describe the epidemiology of SSS.This analysis included 20,572 participants (mean baseline age 59 years, 43% male) in the ARIC (Atherosclerosis Risk In Communities) study and the CHS (Cardiovascular Health Study), who at baseline were free of prevalent atrial fibrillation and pacemaker therapy, had a heart rate of ≥50 beats/min unless using beta blockers, and were identified as of white or black race. Incident SSS cases were identified by hospital discharge International Classification of Disease-revision 9-Clinical Modification code 427.81 and validated by medical record review.During an average 17 years of follow-up, 291 incident SSS cases were identified (unadjusted rate 0.8 per 1,000 person-years). Incidence increased with age (hazard ratio [HR]: 1.73; 95% confidence interval [CI]: 1.47 to 2.05 per 5-year increment), and blacks had a 41% lower risk of SSS than whites (HR: 0.59; 95% CI: 0.37 to 0.98). Incident SSS was associated with greater baseline body mass index, height, N-terminal pro-B-type natriuretic peptide, and cystatin C, with longer QRS interval, with lower heart rate, and with prevalent hypertension, right bundle branch block, and cardiovascular disease. We project that the annual number of new SSS cases in the United States will increase from 78,000 in 2012 to 172,000 in 2060.Blacks have a lower risk of SSS than whites, and several cardiovascular risk factors were associated with incident SSS. With the aging of the population, the number of Americans with SSS will increase dramatically over the next 50 years.
- Fragmented QRS and prediction of paroxysmal atrial fibrillation episodes. [Journal Article]
- Pak J Med Sci 2014 Jul; 30(4):862-7.
Prior studies have demonstrated the relationship between cardiovascular diseases and fragmented QRS (fQRS). fQRS was also associated with ventricular arrhythmias. Our objective was to find out the relationship between fQRS and paroxysmal atrial fibrillation (PAF).A total of 301 patients without overt structural heart disease were prospectively included in the study. Patients were divided in to 2 groups according to presence of fQRS. Multivariate logistic regression analysis was used to assess the predictive value of fQRS for predicting PAF.One hundred and three patients had fQRS. Patients with fQRS were older (53±16.8 vs 45.3±17.2, p<0.001), with larger left atrium (LA) (33.2±5.9 vs 30.1±5.9 mm, p=0.001), with thicker interventricular septum (IVS) (10.2±1.9 vs 9.5±2.3 mm, p=0.032), more diabetic (19.8 vs 10.6%, p=0.029) and have more PAF episodes (22.3 vs 4.1%, p<0.001) in comparison with patients without fQRS. fQRS was an independent predictor of detecting PAF episode (odds ratio, 9.69; 95% confidence interval, 2.46-38.15, p=0.001). Hypertension and diabetes mellitus were also predictive.The presence of fQRS independently predicted PAF episodes in holter monitoring (HM). Further studies are needed to clarify the clinical implications of this finding.
- The role of adenosine receptors and endogenous adenosine in citalopram-induced cardiovascular toxicity. [Journal Article]
- Indian J Pharmacol 2014 Jul; 46(4):378-85.
We investigated the role of adenosine in citalopram-induced cardiotoxicity.Protocol 1: Rats were randomized into four groups. Sodium cromoglycate was administered to rats. Citalopram was infused after the 5% dextrose, 8-Cyclopentyl-1,3-dipropylxanthine (DPCPX; A1 receptor antagonist), 8-(-3-chlorostyryl)-caffeine (CSC; A2a receptor antagonist), or dimethyl sulfoxide (DMSO) administrations. Protocol 2: First group received 5% dextrose intraperitoneally 1 hour prior to citalopram. Other rats were pretreated with erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA; inhibitor of adenosine deaminase) and S-(4-Nitrobenzyl)-6-thioinosine (NBTI; inhibitor of facilitated adenosine transport). After pretreatment, group 2 received 5% dextrose and group 3 received citalopram. Adenosine concentrations, mean arterial pressure (MAP), heart rate (HR), QRS duration and QT interval were evaluated.In the dextrose group, citalopram infusion caused a significant decrease in MAP and HR and caused a significant prolongation in QRS and QT. DPCPX infusion significantly prevented the prolongation of the QT interval when compared to control. In the second protocol, citalopram infusion did not cause a significant change in plasma adenosine concentrations, but a significant increase observed in EHNA/NBTI groups. In EHNA/NBTI groups, citalopram-induced MAP and HR reductions, QRS and QT prolongations were more significant than the dextrose group.Citalopram may lead to QT prolongation by stimulating adenosine A1 receptors without affecting the release of adenosine.
- Levels of circulating anti-muscarinic and anti-adrenergic antibodies and their effect on cardiac arrhythmias and dysautonomia in murine models of Chagas disease. [JOURNAL ARTICLE]
- Parasitology 2014 Aug 5.:1-10.
SUMMARY Antibodies (Ab) recognizing G-protein coupled receptors, such as β 1 and β 2 adrenergic (anti-β 1-AR and anti-β 2-AR, respectively) and muscarinic cholinergic receptors (anti-M2-CR) may contribute to cardiac damage, however their role in chronic chagasic cardiomyopathy is still controversial. We describe that Trypanosoma cruzi-infected C3H/He mice show increased P and QRS wave duration, and PR and QTc intervals, while the most significant ECG alterations in C57BL/6 are prolonged P wave and PR interval. Echocardiogram analyses show right ventricle dilation in infected animals of both mouse lineages. Analyses of heart rate variability (HRV) in chronically infected C3H/He mice show no alteration of the evaluated parameters, while C57BL/6 infected mice display significantly lower values of HRV components, suggesting autonomic dysfunction. The time-course analysis of anti-β 1-AR, anti-β 2-AR and anti-M2-CR Ab titres in C3H/He infected mice indicate that anti-β 1-AR Ab are detected only in the chronic phase, while anti-β 2-AR and anti-M2-CR are observed in the acute phase, diminish at 60 dpi and increase again in the chronic phase. Chronically infected C57BL/6 mice presented a significant increase in only anti-M2-CR Ab titres. Furthermore, anti-β 1-AR, anti-β 2-AR and anti-M2-CR, exhibit significantly higher prevalence in chronically T. cruzi-infected C3H/He mice when compared with C57BL/6. These observations suggest that T. cruzi infection leads to host-specific cardiac electric alterations.