Comparison of PR, QRS, and QT interval measurements by seven ECG interpretation programs.

BACKGROUND: Electrocardiograph-generated measurements of PR, QRS, and QT intervals are generally thought to be more precise than manual measurements on paper records. However, the performance of different programs has not been well compared. METHODS: Routinely obtained digital electrocardiograms (ECGs), including over 500 pediatric ECGs, were used to create over 2000 10 s analog ECGs that were replayed through seven commercially available electrocardiographs. The measurements for PR interval, QRS duration, and QT interval made by each program were extracted and compared against each other (using the median of the programs after correction for program bias) and the population mean values. RESULTS: Small but significant systematic biases were seen between programs. The smallest and largest variation from the population mean differed by 4.7 ms for PR intervals, 5.8 ms for QRS duration, and 12.4 ms for QT intervals. In pairwise comparison programs showed similar accuracy for most ECGs, with the average absolute errors at the 75th percentile for PR intervals being 4-6 ms from the median, QRS duration 4-8 ms, and QT interval 6-10 ms. However, substantial differences were present in the numbers and extent of large, clinically significant errors (e.g at the 98th percentile), for which programs differed by a factor of two for absolute errors, as well as differences in the mix of overestimations and underestimations. CONCLUSIONS: When reading digital ECGs, users should be aware that small systematic differences exist between programs and that there may be large clinically important errors in difficult cases.

Performance of seven ECG interpretation programs in identifying arrhythmia and acute cardiovascular syndrome.

BACKGROUND: No direct comparison of current electrocardiogram (ECG) interpretation programs exists. OBJECTIVE: Assess the accuracy of ECG interpretation programs in detecting abnormal rhythms and flagging for priority review records with alterations secondary to acute coronary syndrome (ACS). METHODS: More than 2,000 digital ECGs from hospitals and databases in Europe, USA, and Australia, were obtained from consecutive adult and pediatric patients and converted to 10 s analog samples that were replayed on seven electrocardiographs and classified by the manufacturers' interpretation programs. We assessed ability to distinguish sinus rhythm from non-sinus rhythm, identify atrial fibrillation/flutter and other abnormal rhythms, and accuracy in flagging results for priority review. If all seven programs' interpretation statements did not agree, cases were reviewed by experienced cardiologists. RESULTS: All programs could distinguish well between sinus and non-sinus rhythms and could identify atrial fibrillation/flutter or other abnormal rhythms. However, false-positive rates varied from 2.1% to 5.5% for non-sinus rhythm, from 0.7% to 4.4% for atrial fibrillation/flutter, and from 1.5% to 3.0% for other abnormal rhythms. False-negative rates varied from 12.0% to 7.5%, 9.9% to 2.7%, and 55.9% to 30.5%, respectively. Flagging of ACS varied by a factor of 2.5 between programs. Physicians flagged more ECGs for prompt review, but also showed variance of around a factor of 2. False-negative values differed between programs by a factor of 2 but was high for all (>50%). Agreement between programs and majority reviewer decisions was 46-62%. CONCLUSIONS: Automatic interpretations of rhythms and ACS differ between programs. Healthcare institutions should not rely on ECG software "critical result" flags alone to decide the ACS workflow.

Cardiac resynchronization therapy: a comparison among left ventricular bipolar, quadripolar and active fixation leads.

We evaluated the performance of 3 different left ventricular leads (LV) for resynchronization therapy: bipolar (BL), quadripolar (QL) and active fixation leads (AFL). We enrolled 290 consecutive CRTD candidates implanted with BL (n = 136) or QL (n = 97) or AFL (n = 57). Over a minimum 10 months follow-up, we assessed: (a) composite technical endpoint (TE) (phrenic nerve stimulation at 8 V@0.4 ms, safety margin between myocardial and phrenic threshold <2V, LV dislodgement and failure to achieve the target pacing site), (b) composite clinical endpoint (CE) (death, hospitalization for heart failure, heart transplantation, lead extraction for infection), (c) reverse remodeling (RR) (reduction of end systolic volume >15%). Baseline characteristics of the 3 groups were similar. At follow-up the incidence of TE was 36.3%, 14.3% and 19.9% in BL, AFL and QL, respectively (p < 0.01). Moreover, the incidence of RR was 56%, 64% and 68% in BL, AFL and QL respectively (p = 0.02). There were no significant differences in CE (p = 0.380). On a multivariable analysis, "non-BL leads" was the single predictor of an improved clinical outcome. QL and AFL are superior to conventional BL by enhancing pacing of the target site: AFL through prevention of lead dislodgement while QL through improved management of phrenic nerve stimulation.

Use of antihistamines and risk of ventricular tachyarrhythmia: a nested case-control study in five European countries from the ARITMO project.

PURPOSE: After regulatory restrictions for terfenadine and astemizole in '90s, only scarce evidence on proarrhythmic potential of antihistamines has been published. We evaluate the risk of ventricular tachyarrhythmia (VA) related to the use of individual antihistamines. METHODS: A matched case-control study nested in a cohort of new users of antihistamines was conducted within the EU-funded ARITMO project. Data on 1997-2010 were retrieved from seven healthcare databases: AARHUS (Denmark), GEPARD (Germany), HSD and ERD (Italy), PHARMO and IPCI (Netherlands) and THIN (UK). Cases of VA were selected and up to 100 controls were matched to each case. The odds ratio (OR) of current use for individual antihistamines (AHs) was estimated using conditional logistic regression. RESULTS: For agents largely used to prevent allergic symptoms, such as cetirizine, levocetirizine, loratadine, desloratadine and fexofenadine, we found no VA risk. A statistically significant, increased risk of VA was found only for current use of cyclizine in the pooled analysis (ORadj, 5.3; 3.6-7.6) and in THIN (ORadj, 5.3; 95% CI, 3.7-7.6), for dimetindene in GEPARD (ORadj, 3.9; 1.1-14.7) and for ebastine in GEPARD (ORadj, 3.3; 1.1-10.8) and PHARMO (ORadj, 4.6; 1.3-16.2). CONCLUSIONS: The risk of VA associated with a few specific antihistamines could be ascribable to heterogeneity in pattern of use or in receptor binding profile.

AF burden is important - fact or fiction?

Asymptomatic atrial fibrillation (AF) is common and in view of its prognostic impact (the same as of clinically overt AF) knowledge of the overall AF burden (defined as the amount of time spent in AF) appears to be important, both for scientific and clinical reasons. Data collected on more than 12,000 patients indicate that cardiac implantable electrical devices (CIEDs) are validated tools for measuring AF burden and that AF burden is associated with an increased risk of stroke. A maximum daily AF burden of ≥ 1 h carries important negative prognostic implications and may be a clinically relevant parameter for improving risk stratification for stroke. Decision-making should primarily consider the context in which asymptomatic, subclinical arrhythmias are detected (i.e. primary or secondary prevention of stroke and systemic embolism) and the risk profile of every individual patient with regard to thromboembolic and haemorrhagic risk, as well as patient preferences and values. Continuous monitoring using CIEDs with extensive data storage capabilities allow in-depth study of the temporal relationship between AF and ischaemic stroke. The relationships between AF and stroke are complex. AF is certainly a risk factor for cardioembolic stroke, with a cause-effect relationship between the arrhythmia and a thromboembolic event, the latter being related to atrial thrombi. However, AF can also be a simple 'marker of risk', with a non-causal association between the arrhythmia and stroke, the latter being possibly related to atheroemboli from the aorta, the carotid arteries or from other sources.

Expenditure and value for money: the challenge of implantable cardioverter defibrillators.

Many technology-driven interventions entail considerable financial cost, raising affordability issues. The implantable cardioverter defibrillator (ICD) is a case of an effective primary prevention intervention with high initial costs that is capable of delivering long-term population benefits. At first glance, such interventions may provoke diffidence, if not active resistance, due to the financial burdens which inevitably accompany their widespread adoption. In this article, we review the available economic tools that can help address the ICD cost issue. We think awareness of such knowledge may facilitate dialogues between physicians, administrators and policymakers, and help foster rational decision-making.

Electrical cardioversion for persistent atrial fibrillation or atrial flutter in clinical practice: predictors of long-term outcome.

Despite the results of Atrial Fibrillation Follow-up Investigation of Rhythm Management and Rate Control versus Electrical Cardioversion for Persistent Atrial Fibrillation trials, which favour a general shift in atrial fibrillation (AF) therapeutic approach towards control of ventricular rate, a strategy based on restoration of sinus rhythm could still play a role in selected patients at lower risk of AF recurrence. We explored possible predictors of relapses after external electrical cardioversion among patients with persistent AF or atrial flutter (AFL). We analysed the clinical characteristics and conventional echocardiographic parameters of patients with persistent AF/AFL enrolled in an institutional electrical cardioversion programme. Among 242 patients (AF/AFL, 195/47; mean age 62+/-13 years), sinus rhythm was restored in 215 (89%) and maintained in 73 (34%) at a follow-up of 930 days (median). No baseline clinical/echocardiographic variables predicted acute efficacy of cardioversion at logistic regression analysis. However, two variables predicted long-term AF/AFL recurrence among patients with successful cardioversion at multivariate Cox's proportional hazards analysis: (i) duration of arrhythmia>or=1 year (HR, 2.07; 95% CI, 1.29-3.33) and (ii) presence of previous cardioversion (HR, 1.67; 95% CI, 1.17-2.38). These variables also presented high-positive predictive values (72% and 80% respectively). Whereas the high acute efficacy of electrical cardioversion (approximately 90%) does not appear to be predictable, two simple clinical variables could help identify patients at higher risk of long-term AF/AFL recurrence after successful electrical cardioversion. We think there could be a case for initially attempting external electrical cardioversion to patients who have had AF/AFL for <1 year. In such patients, the chance of long-term success appears to be relatively high.