Elaine Clark

Publications of Elaine Clark

• Localization of accessory pathways in the Wolff-Parkinson-White pattern--physician versus computer interpretation of the same algorithm.

  Authors: Andrew D McGavigan, Elaine Clark, F Russell Quinn, Andrew C Rankin, Peter W Macfarlane

  Pacing and clinical electrophysiology : PACE. 09/2007; 30(8):998-1002.

  BACKGROUND: There are several published algorithms for the prediction of accessory pathway (AP) location in the Wolff-Parkinson-White syndrome from the 12-lead electrocardiogram (ECG). Most depend onBACKGROUND: There are several published algorithms for the prediction of accessory pathway (AP) location in the Wolff-Parkinson-White syndrome from the 12-lead electrocardiogram (ECG). Most depend on stepwise criteria, and minor disagreements between observers over QRS transition point or delta wave axis may lead to different classification of pathway location. We compared the utility of a computerized program in identifying pathway location from the ECG using the algorithm published by Fitzpatrick and coworkers(3) against physician assessment with the same algorithm. METHODS: Thirty-one 12-lead ECGs with an overt preexcitation pattern were examined by three physicians and AP localized to one of eight anatomical sites using the Fitzpatrick algorithm, with disagreements resolved by consensus. Similarly, pathway location was determined by the Glasgow ECG program with the Fitzpatrick algorithm incorporated into its logic. RESULTS: The agreement between each physician and their consensus was 28/31, 29/31, and 29/31. Similarly, assessment by the Glasgow program produced agreement with the physician consensus in 29/31 cases. Of the 24 patients who underwent radiofrequency ablation, the program localized the pathway to the true or adjacent annular region in 20, compared to 20/24 by physician assessment of the algorithm, producing a similar predictive accuracy to published data. CONCLUSION: This study has shown that incorporation of the Fitzpatrick algorithm for AP location into a widely used computer program results in the same level of performance as that of experienced physicians and may be useful in clinical practice as an aid to referral for electrophysiological study and ablation.

• Evaluation of the electrocardiographic criteria for left ventricular hypertrophy.

  Authors: Iain Morrison, Elaine Clark, Peter W Macfarlane

  Anadolu kardiyoloji dergisi : AKD = the Anatolian journal of cardiology. 08/2007; 7 Suppl 1:159-63.

  OBJECTIVE: Left ventricular hypertrophy (LVH) is an independent predictor of cardiovascular (CV) mortality.This study compared different criteria including Sokolow-Lyon and Cornell, in terms ofOBJECTIVE: Left ventricular hypertrophy (LVH) is an independent predictor of cardiovascular (CV) mortality.This study compared different criteria including Sokolow-Lyon and Cornell, in terms of voltage and voltage-QRS-duration products, as well as point-scoring systems such as the Romhilt-Estes, Perugia and Glasgow-Royal-Infirmary modified Romhilt-Estes score. METHODS: Patients undergoing echocardiography were recruited from the cardiology department in Glasgow Royal Infirmary. Echocardiographically derived left ventricular mass was indexed to body surface area and using sex dependent thresholds, LVH was determined. Electrocardiograms (ECG) were processed using The University of Glasgow Analysis Program, permitting different LVH criteria to be calculated and evaluated. Inclusion criteria for this study were that the patients had a technically adequate echocardiogram and ECG. RESULTS: The main analysis used 51 male and 76 female patients. At published thresholds, the Lewis index gave the greatest sensitivity of the voltage criteria (12%). However, adjusted to 95% specificity, the Cornell index produced the greatest sensitivity at 19%. The best voltage-duration product was the Cornell product that gave 15% sensitivity and 19% when adjusted to 95% specificity.The point scoring systems proved to be the most accurate with the Perugia score being 22% sensitive and the Glasgow Royal Infirmary modified Romhilt-Estes score 24 % sensitive, both at 95% specificity. CONCLUSION: This study finds that ECG criteria for LVH that use only voltage are relatively poor predictors of LVH. This study also finds that the best criteria for assessing LVH are the point scoring criteria, in particular the Glasgow Royal Infirmary Modified Romhilt-Estes score.

• The assessment of autonomic function in chronic atrial fibrillation: description of a non-invasive technique based on circadian rhythm of atrioventricular nodal functional refractory periods.

  Authors: Aleem U Khand, Andrew C Rankin, John G F Cleland, Islay Gemmell, Elaine Clark, Peter W Macfarlane

  Europace : European pacing, arrhythmias, and cardiac electrophysiology : journal of the working groups on cardiac pacing, arrhythmias, and cardiac cellular electrophysiology of the European Society of Cardiology. 12/2006; 8(11):927-34.

  AIMS: Heart rate variability (HRV) parameters can be used to assess autonomic function and to predict outcome, but this has been done exclusively in patients with sinus rhythm. Atrial fibrillationAIMS: Heart rate variability (HRV) parameters can be used to assess autonomic function and to predict outcome, but this has been done exclusively in patients with sinus rhythm. Atrial fibrillation (AF) is the commonest sustained arrhythmia and is particularly prevalent in heart failure. We have developed a simple index to assess autonomic function in patients with chronic AF. METHODS AND RESULTS: Forty patients with chronic AF (>1 month) and symptoms of heart failure underwent ambulatory 24 h electrocardiography recording as well as evaluation of symptoms, exercise capacity (6 min walk distance), ventricular function (echocardiography and radionuclide ventriculography), and neuroendocrine activation. A number of standard HRV parameters shown to have prognostic significance in sinus rhythm were also determined. A modified in-house HRV statistical programme was used to filter labelled QRS intervals and to compute the 5th percentile RR interval in each hour. This parameter has been shown to approximate the functional refractory period (FRP) of the atrioventricular node (AVN). A cosine curve was fitted to hourly 5th percentile RR intervals for each patient and from this was estimated the diurnal change in hourly 5th percentile RR interval (approximating DeltaFRP of the AVN) and, by inference, diurnal variation in sympathovagal input to the AVN. Digoxin was the sole agent permitted for control of ventricular rate. DeltaFRP of the AVN varied and revealed a significant correlation, on multivariate analysis, with mean RR interval (P<0.001), SDARR (SD of 5-min average RR intervals during 24 h, P<0.001), and NYHA class of heart failure (classes III and IV heart failure vs. classes I and II, P=0.02). SDARR has previously been shown independently to predict mortality in patients with chronic AF and heart failure. CONCLUSION: This analysis describes a novel non-invasive method for assessing autonomic function in chronic AF. Whether DeltaFRP in chronic AF patients can independently predict adverse prognosis or sudden death requires further study.

• Heart rate variability fraction--a new reportable measure of 24-hour R-R interval variation.

  Authors: Maciej Sosnowski, Elaine Clark, Shahid Latif, Peter W Macfarlane, Michal Tendera

  Annals of noninvasive electrocardiology : the official journal of the International Society for Holter and Noninvasive Electrocardiology, Inc. 01/2005; 10(1):7-15.

  BACKGROUND: The scatterplot of R-R intervals has several unique features. Its numerical evaluation may produce a new useful index of global heart rate variability (HRV) from Holter recordings.BACKGROUND: The scatterplot of R-R intervals has several unique features. Its numerical evaluation may produce a new useful index of global heart rate variability (HRV) from Holter recordings. METHODS: Two-hundred and ten middle-aged healthy subjects were enrolled in this study. The study was repeated the next day in 165 subjects. Each subject had a 24-hour ECG recording taken. Preprocessed data were transferred into a personal computer and the standard HRV time-domain indices: standard deviation of total normal R-R intervals (SDNN), standard deviation of averaged means of normal R-R intervals over 5-minute periods (SDANN), triangular index (TI), and pNN50 were determined. The scatterplot area (0.2-1.8 second) was divided into 256 boxes, each of 0.1-second interval, and the number of paired R-R intervals was counted. The heart rate variability fraction (HRVF) was calculated as the two highest counts divided by the number of total beats differing from the consecutive beat by <50 ms. The HRVF was obtained by subtracting this fraction from 1, and converting the result to a percentage. RESULTS: The normal value of the HRVF was 52.7 +/- 8.6%. The 2-98% range calculated from the normal probability plot was 35.1-70.3%. The HRVF varied significantly with gender (female 48.7 +/- 8.4% vs male 53.6 +/- 8.6%, P = 0.002). The HRVF correlated with RRI (r = 0.525) and showed a similar or better relationship with SDNN (0.851), SDANN (0.653), and TI (0.845) than did the standard HRV measures with each other. Bland-Altman plot showed a good day-by-day reproducibility of the HRVF, with the intraclass correlation coefficient of 0.839 and a low relative standard error difference (1.8%). CONCLUSION: We introduced a new index of HRV, which is easy for computation, robust, reproducible, easy to understand, and may overcome the limitations that belong to the standard HRV measures. This index, named HRV fraction, by combining magnitude, distribution, and heart-rate influences, might become a clinically useful index of global HRV.

• Modification of ACC/ESC criteria for acute myocardial infarction.

  Authors: Peter W Macfarlane, David Browne, Brian Devine, Elaine Clark, Evan Miller, Jodat Seyal, David Hampton

  Journal of electrocardiology. 02/2004; 37 Suppl:98-103.

  The American College of Cardiology (ACC) and European Society of Cardiology (ESC) recently proposed criteria for acute ST elevation myocardial infarction (STEMI). These criteria were based on STjThe American College of Cardiology (ACC) and European Society of Cardiology (ESC) recently proposed criteria for acute ST elevation myocardial infarction (STEMI). These criteria were based on STj >0.1 mV in limbs leads and V4-V6, or STj >0.2 mV in V1 to V3 with criteria being met in two contiguous leads. The criteria were neither age nor sex dependent and the aim of the present study was to evaluate whether or not improved STEMI criteria that were age and gender dependent could be developed. A training set of 789 ECGs from patients presenting with chest pain due to cardiac and other causes was available for study. Revised criteria for STEMI were developed using these data as well as ECGs from a normal adult population of 859 males and 637 females. A test set of ECGs was available in the form of 1220 ECGs recorded from a separate hospital from patients presenting with chest pain. 248 patients had an acute myocardial infarction on the basis of conventional clinical criteria while 972 did not. There was an improvement in sensitivity using the new criteria compared to the old criteria from 41.5% to 46.7% while specificity improved from 96.0% to 98.5%. Specificity in normals improved from 92.6% to 99.8%. The conclusion drawn is that while the ACC/ESC criteria are simple to apply, they are not particularly specific and can be improved by being supplemented by other ECG measures and optimized for age and sex.