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QRS interval [keywords]
- An Unusual Narrow QRS Complex Tachycardia: What Is the Mechanism? [JOURNAL ARTICLE]
- Ann Noninvasive Electrocardiol 2014 Jul 9.
The electrocardiogram of a 72-year-old woman showed episodes of nonsustained narrow QRS complex tachycardia. Tracing analysis suggested that the arrhythmia was due to interpolated atrial extrasystoles occurring in bigeminal rhythm. Interpolation of atrial extrasystoles is a rare phenomenon. In this condition, a premature atrial beat is "sandwiched" between 2 normal sinus beats, and sinus PP interval containing the extrasystole is often longer than unaffected sinus cycles. Alternative mechanisms for the arrhythmia are discussed, such as: (1) sinus node reentry; (2) 1:2 response to atrial ectopy over the fast and the slow atrioventricular nodal pathways; and (3) couplets of atrial extrasystoles.
- Identification of three novel genetic variations associated with electrocardiographic traits (QRS duration and PR interval) in East Asians. [JOURNAL ARTICLE]
- Hum Mol Genet 2014 Jul 17.
The electrocardiogram has several advantages in detecting cardiac arrhythmia - it is readily available, noninvasive, and cost-efficient. Recent genome-wide association studies have identified single nucleotide polymorphisms that are associated with electrocardiogram measures. We performed a genome-wide association study using Korea Association Resource data for the discovery phase (phase 1, n=6,805) and 2 consecutive replication studies in Japanese populations (phase 2, n=2,285; phase 3, n=5,010) for QRS duration and PR interval. Three novel loci were identified: rs2483280 (PRDM16 locus) and rs335206 (PRDM6 locus) were associated with QRS duration, and rs17026156 (SLC8A1 locus) correlated with PR interval. PRDM16 was recently identified as a causative gene of left ventricular noncompaction and dilated cardiomyopathy in 1p36 deletion syndrome, which is characterized by heart failure, arrhythmia, and sudden cardiac death. Thus, our finding that a PRDM16 SNP is linked to QRS duration strongly implicates PRDM16 in cardiac function. In addition, C allele of rs17026156 increases PR interval (beta±se, 2.39±0.40 ms) and exist far more frequently in East Asians (0.46) than in Europeans and Africans (0.05 and 0.08, respectively).
- Sinus rhythm heart rate estimation in high noise environments by application of a priori RR interval statistics. [Journal Article]
- J Med Eng Technol 2014 Aug; 38(6):317-27.
Abstract Most existing heart beat detection algorithms serially process peaks, which can be either noise or true beats. Serial processing can result in inaccurate detections in the context of high noise. The proposed method relies on the relative regularity of sinus rhythm RR interval changes to select the best sequences of peaks in a 5-10 s long segment of cardiac data. The best sequences with a current data segment are subjected to a trending analysis, to determine whether their associated RR intervals fit within a pattern of prior best segments. The RR regularity scores and the results of the trending analysis are combined into a single sequence score and the final sequence for a segment is chosen from the best sequences based on this overall score. The current heart rate estimate is updated with the final sequence's RR interval by an adaptive filter that weights the overall score. Twenty-four hour RR interval records for 54 normal individuals were parsed into 10-s segments and corrupted with spurious 'noise' peaks, which resulted in a revised RR interval series that included a number of false RR intervals. The algorithm was run on these corrupted RR interval series. The percentages of mean heart rate values within 5 beats min(-1) of the true value were 95%, 88% and 77% for 10, 20 and 30 added noise spikes, respectively. The percentages of mean heart rate values within 10 beats min(-1) of the true value were 98%, 96% and 91% for 10, 20 and 30 added noise spikes, respectively. Accuracy was higher for data segments characterized by relatively low RR interval variability. The proposed algorithm shows promise for estimating average heart rate for sinus rhythm in high noise environments.
- P77Specific consideration when interpreting the hypertrophy response to pressure overload in C57BL/6NTac and C57BL/6J mice. [Journal Article]
- Cardiovasc Res 2014 Jul 15.:S12.
Transverse aortic constriction (TAC) has been extensively used as a cardiac stress in genetically modified mice to investigate the molecular mechanisms of cardiac hypertrophy. But the hypertrophic response to TAC can be significantly influenced by the time course of TAC, the age and the genetic background of the mice. The International Knockout Mouse Consortium has selected to use the C57BL/6NTac mouse strain to generate null alleles for all mouse genes; however, we have found a range of baseline cardiac phenotypic differences between this substrain and the commonly used C57BL/6J substrain. Therefore, we have assessed the optimal conditions to induce cardiac hypertrophy by TAC in the C57BL/6NTac strain, and have determined whether the hypertrophic response to TAC is different in these two C57BL/6 substrains.To establish the optimal conditions for TAC-induced hypertrophy in the C57BL/6NTac substrain, 8, 10 and 12-week old mice were subjected to TAC and monitored by echocardiography. Cardiac function was found to significantly deteriorate in 10-12 week old mice after 2 weeks, while 8-week old mice developed hypertrophy after 2 weeks and then reduced cardiac function after 5 weeks. Therefore, 2-week TAC in 8 week old mice was used to further study the hypertrophic response in the two C57BL/6 substrains. Echocardiography, conscious ECG, cardiac haemodynamic assessment, histology, and real-time PCR were conducted to evaluate cardiac function, hypertrophy, fibrosis, and the expression of hypertrophy markers.Cardiac hypertrophy evaluated by heart weight to tibia length ratio (HW/TL) was highly variable in C57BL/6J mice, but this reflected the variation in aortic arch dimension as assessed by echocardiography. When comparing the response to the hypertrophic stimulus, C57BL/6NTac demonstrated greater hypertrophic growth as evaluated by HW/TL, cardiomyocyte cell surface area, and expression of BNP (all p<0.05). Cardiac remodelling such as fibrosis was also more extensive. This exacerbated hypertrophic growth was associated with increased QRS duration (19.33±2.76 vs. 15.29±0.64 ms, p=0.01), QTc interval and multiple ventricular arrhythmias in C57BL/6NTac mice.There are clear differences in the response to pressure overload in widely used C57BL/6 substrains. C57BL/6J mice were found to have a large variation in aortic structure which is reflected in the variable hypertrophic response; whilst the C57BL/6NTac substrain has a consistently exacerbated hypertrophic response. It is therefore essential to consider these distinct phenotypic differences when interpreting data.
- P637Desmin null mouse as a possible experimental model of arrhythmogenic cardiomyopathy. [Journal Article]
- Cardiovasc Res 2014 Jul 15.:S116.
Desmin null mice (Des-/-) develop a multisystem disorder involving cardiac, skeletal, and smooth muscle. Myocardial abnormalities include progressive degeneration, cardiomyocyte death, extensive calcification and fibrosis which lead to a dilated cardiomyopathy pattern. The aim of this study is to investigate the presence of arrhythmias in a Des-/- mouse model as compared to wild type (WT) mice.Mice lacking desmin were generated by gene targeting via homologous recombination as previously describe. Electrocardiographic (ECG) recordings were obtained in 8-months old Des-/- and WT mice (n=17) using a Data Sciences International Telemetry System (St. Paul, MN, USA). ECG data were collected for 5 min every 30 min for 24 consecutive hour, giving 240 min of recording. Arrhythmias were recorded and heart rate, QRS wave duration and PR and QTc (Bazett's formula) intervals and were measured using Ponemah software. Mice also underwent a swimming stress test protocol of 20min total duration under ECG recording.Premature ventricular beats were more often in Des-/- mice (n=16, 85.5±37.9/240min, range 0-612) when compared to the WT (n=8, 3.9±1.3/240min, range 0-15). Heart rate (523±20 vs 566±19 bpm), QRS (16.9±1.3 vs 17.0±0.9 ms) and PR duration (37.1±1.1 vs 34.1±1.5 ms, p=0.07) did not differ between Des-/- and WT mice. Only QTc interval was prolonged in Des-/- mice compared to the WT (186.1±5.9 vs 173.3±3.6 ms, p=0.04). Supraventricular ectopic beats were only present in Des-/- mice (range 3-111). During endurance, more premature ventricular beats were observed in Des-/- mice (range 14-510) compared to the WT (range 2-14) but first and second degree AV block were only present in Des-/- mice.Ventricular and supraventricular arrhythmias are common in Des-/- mice compared to the WT making this genetic model a possible experimental model of arrhythmogenic cardiomyopathy.
- Impact of QRS duration on survival benefit with prophylactic implantable cardioverter-defibrillators: a meta-analysis of randomized controlled trials. [JOURNAL ARTICLE]
- J Cardiovasc Med (Hagerstown) 2014 Jul 10.
QRS duration is an important risk factor for both sudden cardiac death and all-cause mortality in patients with moderate to severe left ventricular systolic dysfunction. However, it is unknown whether baseline QRS duration can help predict the mortality benefit from implantable cardioverter-defibrillators (ICDs) when used for primary prevention purposes.Our objective was to examine the relationship between baseline QRS duration and mortality reduction with ICDs implanted for primary prevention by performing a meta-analysis of all available randomized clinical trials.A systematic literature search of SCOPUS (covering MEDLINE and EMBASE) was conducted for randomized controlled clinical trials involving ICDs. Primary prevention trials of systolic dysfunction that reported all-cause mortality according to subgroups on the basis of baseline QRS duration were included.A total of four randomized controlled clinical trials enrolling 3561 patients were included. Patients with QRS durations less than 120 ms [n = 2002, hazard ratio 0.78, 95% confidence interval (CI) 0.63-0.96, P = 0.018] and at least 120 ms (n = 1559, hazard ratio 0.59, 95% CI 0.48-0.73, P = 0.0000009) had significant decreases in all-cause mortality. On heterogeneity analysis, a strong trend for greater magnitude of benefit in patients with QRS at least 120 ms was observed (22% risk reduction vs. 41% risk reduction, P = 0.066).For primary prevention purposes, ICDs are effective in reducing all-cause mortality in moderate to severe systolic dysfunction regardless of QRS duration. However, patients with a baseline QRS duration of at least 120 ms seem to derive a greater mortality benefit from ICDs.
- Carbon monoxide poisoning increases Tpeak-Tend dispersion and QTc dispersion. [JOURNAL ARTICLE]
- Cardiovasc J Afr 2014 May/June; 25(3):106-109.
Carbon monoxide (CO) poisoning leads to cardiac dysrhythmia. Increased heterogeneity in ventricular repolarisation on electrocardiogram (ECG) shows an increased risk of arrhythmia. A number of parameters are used to evaluate ventricular repolarisation heterogeneity on ECG. The aim of our study is to investigate the effect of acute CO poisoning on indirect parameters of ventricular repolarisation on ECG.Sixty-seven patients were included in this case-control study. Thirty patients with acute CO poisoning were assigned to group 1 (19 females, mean age: 30.8 ± 11.3 years). A control group was formed with patients without known cardiac disease (group 2, n = 37; 25 females, mean age: 26.0 ± 5.2 years). Twelve-lead ECG and serum electrolyte levels were recorded in all patients. Also, carboxyhaemoglobin (COHb) levels were recorded in group 1. Tpeak-Tend ( TpTe ) interval, TpTe dispersion, TpTe/QT ratio, QT interval and QTd durations were measured as parameters of ventricular repolarisation. Corrected QT (QTc ) and QTc dispersion (QTcd ) intervals were determined with the Bazett's formula.The mean COHb level in group 1 was 27.6 ± 7.4% and mean duration of CO exposure was 163.5 ± 110.9 min. No statistically significant difference was found in age, gender, serum electrolytes or blood pressure levels between the groups. QRS, QT, QTc, TpTe interval and TpTe/QT ratio were similar between the groups (p > 0.05). QTcd (65.7 ± 64.4 vs 42.1 ± 14.2 ms, p = 0.003) and TpTe dispersion (40.5 ± 14.8 vs 33.2 ± 4.9 ms, p = 0.006) were significantly longer in group 1 than group 2. COHb level was moderately correlated with TpTe dispersion (r = 0.29; p = 0.01).To our knowledge, this is the first study to investigate TpTe interval and dispersion in CO poisoning. Our results showed that TpTe dispersion and QTc dispersion increased after CO poisoning.
- Efficacy and safety of aripiprazole in Chinese Han schizophrenia subjects: A randomized, double-blind, active parallel-controlled, multicenter clinical trial. [JOURNAL ARTICLE]
- Schizophr Res 2014 Jun 30.
Antipsychotics, such as aripiprazole and risperidone, are often used to treat individuals with schizophrenia. The efficacy as well as safety of aripiprazole in Western populations has been described. The objective of this study is to investigate the efficacy, safety, and tolerability of aripiprazole and risperidone in Chinese Han schizophrenia subjects in mainland China.The 6-week, double-blind, randomized, parallel study was conducted in 5 medical centers in mainland China from November 2007 to March 2011. A total of 279 subjects with a primary DSM-IV diagnosis of schizophrenia were randomly assigned (with a randomization ratio of 1:1) to aripiprazole (n=139) or risperidone (n=140). Efficacy measurements included the Positive and Negative Syndrome Scale (PANSS) total, positive, negative and general psychopathology subscale scores, and Clinical Global Impressions-Severity of Illness (CGI-S), and Improvement scale scores. Extrapyramidal symptoms (EPS), weight gain, serum prolactin level, QTc interval, and self-reported adverse events were also assessed as measures of safety and tolerability.Both the aripiprazole and risperidone groups showed statistically significant improvement of PANSS total, positive, negative, general psychopathology subscale scores, and CGI-S scores from baseline to the endpoint (all p<0.01). Significant improvement was noted in the first week for both treatment groups. There were no significant differences in efficacy measurements between the two treatment groups. Mean change of PANSS total scores from baseline to the endpoint was -26.8±18.1 for aripiprazole and -30.0±17.7 for risperidone, (p=0.1475). The responder rate was 71% (n=99) and 76% (n=107) for aripiprazole and risperidone, respectively, (p=0.323). The incidences of EPS were similar in the aripiprazole (25%, n=35) and risperidone groups (24%, n=34), respectively (p=0.757). No clinically meaningful effects on QTc interval, QRS duration, or PR interval were observed in either treatment groups. However, the incidence of clinically significant weight gain (p=0.0118) and hyperprolactinemia (p<0.001) in the aripiprazole group was significantly lower than in the risperidone group.The study demonstrated that aripiprazole, as well as risperidone, had rapid and persistent efficacy for psychotic symptoms from the first week of therapy. There may be poor efficacy for aripiprazole compared with risperidone for overall improvement, but there were no significant differences in this study. Aripiprazole showed good tolerability with less weight gain and hyperprolactinemia compared with risperidone. The overall efficacy and safety of aripiprazole in Chinese Han schizophrenia subjects were similar to that reported in Western populations.
- ST-T segment changes in patients with tricyclic antidepressant poisoning. [Journal Article]
- J Res Pharm Pract 2013 Jul; 2(3):110-3.
Tricyclic antidepressant (TCA) poisoning is among highly prevalent and potentially dangerous toxicities. ST-T changes are observed in the electrocardiogram (ECG) of most of TCA poisoned patients. We aimed to study ST-T segment changes in TCA toxicity and its probable relationship with other ECG findings.This retrospective study was carried out in Noor and Ali Asghar University Hospital, Isfahan (Iran) in 2012. Patients with TCA toxicity based on the patients' history who had not consumed any cardio-active drugs and did not have a past medical history of cardiovascular disease in the recent 5 years, were randomly selected and investigated. Their demographic and medical data on admission including ECG, age, sex, type and amount of ingested TCA, poisoning severity score, QRS changes, QT interval, heart axis position and R-wave were all recorded. ST-T changes and their relation with other ECG parameters have been determined using statistical analysis.Medical records of 272 patients were analyzed. In symptomatic patients, ST change prevalence was 40.8% and T change prevalence was 9.5%. In asymptomatic patients, the frequency of ST and T changes were 4.8% and 0.8%, respectively (P < 0.05). The most common ST and T changes in baseline (on admission) ECG were non-significant elevation (15.4%), significant elevation (11%) in pre-cordial leads, and T-wave flattening (6.6%). A statistically significant correlation was documented between ST segment changes with QRS and R-wave in aVR. The correlation between T-wave changes and R-wave in aVR lead was also significant.ST-T changes in TCA poisoned patients are more prevalent in symptomatic patients. Obviously for a more definite conclusion, it is necessary to design a prospective study with the control group. This may facilitate a better understanding of ST-T segment changes.
- Evaluation and management of wolff-Parkinson-white in athletes. [Journal Article]
- Sports Health 2014 Jul; 6(4):326-32.
Wolff-Parkinson-White (WPW) is a cardiac conduction system disorder characterized by abnormal accessory conduction pathways between the atria and the ventricles. Symptomatic patients classically present with palpitations, presyncope, or syncope that results from supraventricular tachycardia. While rare, sudden cardiac death may be the first manifestation of underlying disease and occurs more frequently in exercising individuals.Medline and PubMed databases were evaluated through 2012, with the following keywords: WPW, Wolff-Parkinson-White, pre-excitation, sudden cardiac death, risk stratification, and athletes. Selected articles identified through the primary search, along with relevant references from those articles, were reviewed for pertinent clinical information regarding the identification, evaluation, risk stratification, and management of WPW as they pertained to the care of athletes.Systematic review.Level 1.Diagnosis of WPW is confirmed by characteristic electrocardiogram changes, which include a delta wave, short PR interval, and widened QRS complex. Utilization of the electrocardiogram as part of the preparticipation physical evaluation may allow for early identification of asymptomatic individuals with a WPW pattern. Risk stratification techniques identify individuals at risk for malignant arrhythmias who may be candidates for curative therapy through transcatheter ablation.WPW accounts for at least 1% of sudden death in athletes and has a prevalence of at least 1 to 4.5 per 1000 children and adults. The risk of lethal arrhythmia appears to be higher in asymptomatic children than in adults, and sudden cardiac death is often the sentinel event. The athlete with WPW should be evaluated for symptoms and the presence of intermittent or persistent pre-excitation, which dictates further consultation, treatment, and monitoring strategies as well as return to play.