Home About us Contact
|
Home About us Contact | ||
|
|
||
QRS Interval (qr + interval)
Selected AbstractsPatient and Physician Determinants of Implantable Cardioverter Defibrillator Use in the Heart Failure PopulationCONGESTIVE HEART FAILURE, Issue 4 2010Sanders H. Chae MD Recent studies report surprisingly low rates of implantable cardioverter defibrillator (ICD) placement for primary prevention against sudden cardiac death among patients with heart failure and left ventricular systolic dysfunction. Reasons for the low rates of utilization are not well understood. The authors examined ICD implantation rates at a university-based tertiary care center and used multivariable analysis to identify independent factors associated with ICD utilization. The ICD implantation rate for 850 eligible patients was 70%. Forty-seven (18%) patients refused implantation; women were twice as likely to refuse compared to men (8% vs 4%, P=.013). Race was not associated with utilization. On multivariable analysis, independent predictors of implantation included having a heart failure specialist (odds ratio [OR], 8.13; P<.001) or general cardiologist (OR, 2.23; P=.13) managing care, age range 70 to 79 (OR, 0.55; P<.001) or 80 and older (OR, 0.26; P<.001), female sex (OR, 0.49; P<.001), QRS interval (OR, 1.016; P<.001), diastolic blood pressure (OR, 0.979; P=.011), cerebrovascular disease (OR, 0.44; P=.007), and dementia (OR, 0.13; P=.002). Our registry of patients with cardiomyopathy and heart failure reveals that high rates of utilization are possible. Factors closely associated with ICD utilization include type of physician coordinating care, age, and comorbidities. Congest Heart Fail. 2010;16:141,146. © 2010 Wiley Periodicals, Inc. [source] Cardiac function and antiepileptic drug treatment in the elderly: A comparison between lamotrigine and sustained-release carbamazepineEPILEPSIA, Issue 8 2009Erik Saetre Summary Purpose:, To investigate the comparative effects of carbamazepine (CBZ) and lamotrigine (LTG) on electrocardiography (ECG) parameters in elderly patients with newly diagnosed epilepsy. Methods:,, The study was conducted in the Norwegian subcohort (n = 108) of an international randomized double-blind 40-week trial, which compared the efficacy and tolerability of LTG and sustained-release CBZ in patients aged 65 and older with newly diagnosed epilepsy. Target maintenance doses were 400 mg/day for CBZ and 100 mg/day for LTG, with adjustments based on clinical response. Patients with significant unpaced atrioventricular (AV) conduction defect were excluded. Resting 12-lead ECG recordings were made under standardized conditions at pretreatment (baseline) and at the 40-week study visit (treatment visit). Changes in QRS interval (primary endpoint), heart rate (HR), PQ, and QTc (HR-corrected QT) intervals were assessed and compared between groups. Results:, Of the 108 patients randomized, 33 discontinued prematurely because of adverse events (n = 24, none of which was cardiac) or other reasons (n = 9), and 15 were nonevaluable due to incomplete ECG data. None of the assessed ECG parameters differed significantly between groups at baseline. No significant ECG changes were recorded between baseline and treatment visit for QRS duration and QTc intervals, whereas HR fell and PQ intervals increased slightly on both treatments. However, there were no differences between groups in changes from baseline to treatment visit. There were no significant relationships between individual ECG changes and serum drug concentrations, except for QTc intervals, which decreased slightly with increasing CBZ concentrations. The proportion of patients with ECG parameters outside the normal range at treatment visit was similar to that recorded at baseline. Discussion:, Clinically significant ECG changes are not common during treatment with CBZ or LTG in elderly patients with no preexisting significant AV conduction defects. [source] Response to Cardiac Resynchronization Therapy: Is It Time to Expand the Criteria?PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 10 2009HENNEKE VERSTEEG M.Sc. Background: Cardiac resynchronization therapy (CRT) is a promising treatment for a subgroup of patients with advanced congestive heart failure and a prolonged QRS interval. Despite the majority of patients benefiting from CRT, 10,40% of patients do not respond to this treatment and are labeled as nonresponders. Given that there is a lack of consensus on how to define response to CRT, the purpose of this viewpoint is to discuss currently used definitions and their shortcomings, and to provide recommendations as to how an expansion of the criteria for CRT response may be useful to clinicians. Methods and Results: Analysis of the literature and case reports indicates that the majority of established measures of CRT response, including New York Heart Association functional class and echocardiographic, hemodynamic, and neurohormonal parameters, are poor associates of patient-reported symptoms and quality of life. Moreover, the potential moderating role of psychological factors in determining health outcomes after CRT has largely been neglected. Conclusions: It is recommended to routinely assess health status after CRT with a disease-specific questionnaire in standard clinical practice and to examine its determinants, including psychological factors such as personality traits and depression. This may lead to improved (secondary) treatment and prognosis in CHF patients treated with CRT. [source] Atrial Fibrillation Induction and Determination of Atrial Vulnerable Period Using Very Low Energy Synchronized Biatrial Shock in Normal Subjects and in Patients with Atrial FibrillationPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 4 2000HUNG-FAT TSE The atrial vulnerable periods (A VP)for shock induction of atrial fibrillation (AF) in humans have not been clearly defined. Furthermore, the safety and efficacy of using low energy biatrial shock delivered transvenously for AF induction are unknown. We tested the safety and efficacy of using very low energy biatrial shocks, delivered between the right atrium and the coronary sinus for AF induction and used this technique to characterize the A VP in nine controls and nine patients with AF. Thirty-volt and 60-V 3/3-ms biphasic shocks were delivered, starting from 50 ms before the atrial effective refractory period with 20-ms increments until the end of the QRS interval to determine the AVP front, AVP end, and the AVP duration. Successful AF induction could be achieved in eight (89%) of the nine controls and in nine (100%) of the nine patients with AF without any complication. In patients with AF, the AVP front started significantly earlier within the QRS complex, and the AVP duration and the AVP duration/QRS percent ratios were also significantly greater as compared to controls. Furthermore, a higher induction shock energy in patients with AF was associated with an increase in AF inducibility and significantly increased the AVP duration and A VP duration/QRS percent ratio as compared to the controls. This study demonstrated the safe and efficacy of delivering a very low energy biatrial shock during the AVP within the R wave for AF induction. The characteristics of A VP in patients with AF were significantly different from normal subjects. [source] Frequency of Acute Coronary Syndrome in Patients with Normal Electrocardiogram Performed during Presence or Absence of Chest PainACADEMIC EMERGENCY MEDICINE, Issue 6 2009Samuel D. Turnipseed MD Abstract Objectives:, The authors hypothesized that patients with active chest pain at the time of a normal electrocardiogram (ECG) have a lower frequency of acute coronary syndrome (ACS) than patients being evaluated for chest pain but with no active chest pain at the time of a normal ECG. The study objective was to describe the association between chest pain in patients with a normal ECG and the diagnosis of ACS. Methods:, This was a prospective observational study of emergency department (ED) patients with a chief complaint of chest pain and an initial normal ECG admitted to the hospital for chest pain evaluation over a 1-year period. Two groups were identified: patients with chest pain during the ECG and patients without chest pain during the ECG. Normal ECG criteria were as follow: 1) normal sinus rhythm with heart rate of 55,105 beats/min, 2) normal QRS interval and ST segment, and 3) normal T-wave morphology or T-wave flattening. "Normal" excludes pathologic Q waves, left ventricular hypertrophy, nonspecific ST-T wave abnormalities, any ST depression, and discrepancies in the axis between the T wave and the QRS. Patients' initial ED ECGs were interpreted as normal or abnormal by two emergency physicians (EPs); differences in interpretation were resolved by a cardiologist. ACS was defined as follows: 1) elevation and characteristic evolution of troponin I level, 2) coronary angiography demonstrating >70% stenosis in a major coronary artery, or 3) positive noninvasive cardiac stress test. Chi-square analysis was performed and odds ratios (ORs) are presented. Results:, A total of 1,741 patients were admitted with cardiopulmonary symptoms; 387 met study criteria. The study group comprised 199 males (51%) and 188 females (49%), mean age was 56 years (range, 25,90 years), and 106 (27%) had known coronary artery disease (CAD). A total of 261 (67%) patients experienced chest pain during ECG; 126 (33%) patients experienced no chest pain during ECG. There was no difference between the two groups in age, sex, cardiac risk factors, or known CAD. The frequency of ACS for the total study group was 17% (67/387). There was no difference in prevalence of ACS based on the presence or absence of chest pain (16% or 42/261 vs. 20% or 25/126; OR = 0.77, 95% confidence interval = 0.45 to 1.33, p = 0.4). Conclusions:, Contrary to our hypothesis concerning patients who presented to the ED with a chief complaint of chest pain, our study demonstrated no difference in the frequency of acute coronary syndrome between patients with chest pain at the time of acquisition of a normal electrocardiogram and those without chest pain during acquisition of a normal electrocardiogram. [source] Influence of exposure to electromagnetic field on the cardiovascular systemAUTONOMIC & AUTACOID PHARMACOLOGY, Issue 1 2005J. H. Jeong Summary 1 We examined whether extremely low frequency electromagnetic fields (ELF-EMF) affect the basal level of cardiovascular parameters and influence of drugs acting on the sympathetic nervous system. 2 Male rats were exposed to sham control and EMF (60 Hz, 20 G) for 1 (MF-1) or 5 days (MF-5). We evaluated the alterations of blood pressure (BP), pulse pressure (PP), heart rate (HR), and the PR interval, QRS interval and QT interval on the electrocardiogram and dysrhythmic ratio in basal level and dysrhythmia induced by , -adrenoceptor agonists. 3 In terms of the basal levels, there were no statistically significant differences among control, MF-1 and MF-5 in PR interval, QRS interval, mean BP, HR and PP. However, the QT interval, representing ventricular repolarization, was significantly reduced by MF-1 (P < 0.05). 4 (,)-Dobutamine (,1 -adrenoceptor-selective agonist)-induced tachycardia was significantly suppressed by ELF-EMF exposure in MF-1 for the increase in HR (,HR), the decrease in QRS interval (,QRS) and the decrease in QT (,QT) interval. Adrenaline (nonselective , -receptor agonist)-induced dysrhythmia was also significantly suppressed by ELF-EMF in MF-1 for the number of missing beats, the dysrhythmic ratio, and the increase in BP and PP. 5 These results indicated that 1-day exposure to ELF-EMF (60 Hz, 20 G) could suppress the increase in HR by affecting ventricular repolarization and may have a down-regulatory effect on responses of the cardiovascular system induced by sympathetic agonists. [source] Familial Aggregation and Heritability of Electrocardiographic Intervals and Heart Rate in a Rural Chinese PopulationANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2 2009Jianping Li M.D., Ph.D. Background: Estimates of the genetic influences on electrocardiographic (ECG) parameters are inconsistent in previous reports, and no such studies have been performed in China. So we estimated genetic contributions to PR and QRS intervals and the rate-adjusted QT interval (Bazett's QTc) in a Chinese rural population. Methods: A total of 2909 subjects from 847 families were enrolled in the current study. Genetic contributions to ECG parameters were estimated in two ways: correlation coefficients among family members (father-mother, parent-offspring, first sibling-other sibling) and the heritability of each of the ECG parameters. Results: Our results showed significant correlations among family members on theses parameters: the correlation coefficients for PR interval, QRS duration, QTc interval, and HR, between parent-sibling, and sibling-sibling were 0.17 and 0.13, 0.18 and 0.23, 0.22 and 0.28, 0.19 and 0.18, respectively. The heritability for PR interval, QRS duration, QTc interval, and HR were estimated as 0.34, 0.43, 0.40, and 0.34, respectively. Conclusion: Genetic factors, together with the environmental and other cofactors contribute no more than 60% to the variance of the ECG intervals, supporting the concept that multiple factors, including gene-gene and gene-environment interactions could influence ECG interval phenotypes, and genetic factors play a major role. [source] Proarrhythmic potential of halofantrine, terfenadine and clofilium in a modified in vivo model of torsade de pointesBRITISH JOURNAL OF PHARMACOLOGY, Issue 4 2002Andrew J Batey This study was designed to compare the proarrhythmic activity of the antimalarial drug, halofantrine and the antihistamine, terfenadine, with that of clofilium a K+ channel blocking drug that can induce torsade de pointes. Experiments were performed in pentobarbitone-anaesthetized, open-chest rabbits. Each rabbit received intermittent, rising dose i.v. infusions of the ,-adrenoceptor agonist phenylephrine. During these infusions rabbits also received increasing i.v. doses of clofilium (20, 60 and 200 nmol kg,1 min,1), terfenadine (75, 250 and 750 nmol kg,1 min,1), halofantrine (6, 20 and 60 ,mol kg,1) or vehicle. Clofilium and halofantrine caused dose-dependent increases in the rate-corrected QT interval (QTc), whereas terfenadine prolonged PR and QRS intervals rather than prolonging cardiac repolarization. Progressive bradycardia occurred in all groups. After administration of the highest dose of each drug halofantrine caused a modest decrease in blood pressure, but terfenadine had profound hypotensive effects resulting in death of most rabbits. The total number of ventricular premature beats was highest in the clofilium group. Torsade de pointes occurred in 6 out of 8 clofilium-treated rabbits and 4 out of 6 of those which received halofantrine, but was not seen in any of the seven terfenadine-treated rabbits. These results show that, like clofilium, halofantrine can cause torsade de pointes in a modified anaesthetized rabbit model whereas the primary adverse effect of terfenadine was cardiac contractile failure. British Journal of Pharmacology (2002) 135, 1003,1012; doi:10.1038/sj.bjp.0704550 [source] | ||||||||||||||||||||||