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  • Journal article
    Sohaib SM, Kyriacou A, Jones S, Manisty CH, Mayet J, Kanagaratnam P, Peters NS, Hughes AD, Whinnett ZI, Francis DPet al., 2015,

    Evidence that conflict regarding size of haemodynamic response to interventricular delay optimization of cardiac resynchronization therapy may arise from differences in how atrioventricular delay is kept constant.

    , Europace, Vol: 17, ISSN: 1532-2092

    AIMS: Whether adjusting interventricular (VV) delay changes haemodynamic efficacy of cardiac resynchronization therapy (CRT) is controversial, with conflicting results. This study addresses whether the convention for keeping atrioventricular (AV) delay constant during VV optimization might explain these conflicts. METHOD AND RESULTS: Twenty-two patients in sinus rhythm with existing CRT underwent VV optimization using non-invasive systolic blood pressure. Interventricular optimization was performed with four methods for keeping the AV delay constant: (i) atrium and left ventricle delay kept constant, (ii) atrium and right ventricle delay kept constant, (iii) time to the first-activated ventricle kept constant, and (iv) time to the second-activated ventricle kept constant. In 11 patients this was performed with AV delay of 120 ms, and in 11 at AV optimum. At AV 120 ms, time to the first ventricular lead (left or right) was the overwhelming determinant of haemodynamics (13.75 mmHg at ±80 ms, P < 0.001) with no significant effect of time to second lead (0.47 mmHg, P = 0.50), P < 0.001 for difference. At AV optimum, time to first ventricular lead again had a larger effect (5.03 mmHg, P < 0.001) than time to second (2.92 mmHg, P = 0.001), P = 0.02 for difference. CONCLUSION: Time to first ventricular activation is the overwhelming determinant of circulatory function, regardless of whether this is the left or right ventricular lead. If this is kept constant, the effect of changing time to the second ventricle is small or nil, and is not beneficial. In practice, it may be advisable to leave VV delay at zero. Specifying how AV delay is kept fixed might make future VV delay research more enlightening.
  • Journal article
    Tondato F, Zeng H, Goodchild T, Ng FS, Chronos N, Peters NSet al., 2015,

    Autologous Dermal Fibroblast Injections Slow Atrioventricular Conduction and Ventricular Rate in Atrial Fibrillation in Swine

    , Circulation-Arrhythmia and Electrophysiology, Vol: 8, Pages: 439-446, ISSN: 1941-3149
  • Journal article
    Rivera-Rubio J, Alexiou I, Bharath AA, 2015,

    Appearance-based indoor localization: a comparison of patch descriptor performance

    , Pattern Recognition Letters, Vol: 66, Pages: 109-117, ISSN: 1872-7344

    Vision is one of the most important of the senses, and humans use it extensively during navigation. We evaluated different types of image and video frame descriptors that could be used to determine distinctive visual landmarks for localizing a person based on what is seen by a camera that they carry. To do this, we created a database containing over 3 km of video-sequences with ground-truth in the form of distance travelled along different corridors. Using this database, the accuracy of localization—both in terms of knowing which route a user is on—and in terms of position along a certain route, can be evaluated. For each type of descriptor, we also tested different techniques to encode visual structure and to search between journeys to estimate a user’s position. The techniques include single-frame descriptors, those using sequences of frames, and both color and achromatic descriptors. We found that single-frame indexing worked better within this particular dataset. This might be because the motion of the person holding the camera makes the video too dependent on individual steps and motions of one particular journey. Our results suggest that appearance-based information could be an additional source of navigational data indoors, augmenting that provided by, say, radio signal strength indicators (RSSIs). Such visual information could be collected by crowdsourcing low-resolution video feeds, allowing journeys made by different users to be associated with each other, and location to be inferred without requiring explicit mapping. This offers a complementary approach to methods based on simultaneous localization and mapping (SLAM) algorithms.
  • Journal article
    Finegold J, Bordachar P, Kyriacou A, Sohaib SMA, Kanagaratnam P, Ploux S, Lim B, Peters N, Davies W, Ritter P, Francis DP, Whinnett ZIet al., 2015,

    Atrioventricular delay optimization of cardiac resynchronisation therapy: Comparison of non-invasive blood pressure with invasive haemodynamic measures

    , INTERNATIONAL JOURNAL OF CARDIOLOGY, Vol: 180, Pages: 221-222, ISSN: 0167-5273
  • Journal article
    Jamil-Copley S, Vergara P, Carbucicchio C, Linton N, Koa-Wing M, Luther V, Francis DP, Peters NS, Davies DW, Tondo C, Della Bella P, Kanagaratnam Pet al., 2015,

    Application of Ripple Mapping to Visualize Slow Conduction Channels Within the Infarct-Related Left Ventricular Scar

    , CIRCULATION-ARRHYTHMIA AND ELECTROPHYSIOLOGY, Vol: 8, Pages: 76-U110, ISSN: 1941-3149
  • Journal article
    Kirubakaran S, Chowdhury RA, Hall MCS, Patel PM, Garratt CJ, Peters NSet al., 2015,

    Fractionation of electrograms is caused by colocalized conduction block and connexin disorganization in the absence of fibrosis as AF becomes persistent in the goat model

    , HEART RHYTHM, Vol: 12, Pages: 397-408, ISSN: 1547-5271
  • Journal article
    Christensen K, Manani KA, Peters NS, 2015,

    Simple model for identifying critical regions in atrial fibrillation

    , Physical Review Letters, Vol: 114, ISSN: 0031-9007

    Atrial fibrillation (AF) is the most common abnormal heart rhythm and the single biggest cause of stroke. Ablation, destroying regions of the atria, is applied largely empirically and can be curative but with a disappointing clinical success rate. We design a simple model of activation wave front propagation on an anisotropic structure mimicking the branching network of heart muscle cells. This integration of phenomenological dynamics and pertinent structure shows how AF emerges spontaneously when the transverse cell-to-cell coupling decreases, as occurs with age, beyond a threshold value. We identify critical regions responsible for the initiation and maintenance of AF, the ablation of which terminates AF. The simplicity of the model allows us to calculate analytically the risk of arrhythmia and express the threshold value of transversal cell-to-cell coupling as a function of the model parameters. This threshold value decreases with increasing refractory period by reducing the number of critical regions which can initiate and sustain microreentrant circuits. These biologically testable predictions might inform ablation therapies and arrhythmic risk assessment.
  • Journal article
    Lagarto J, Dyer BT, Talbot C, Sikkel MB, Peters NS, French PMW, Lyon AR, Dunsby Cet al., 2015,

    Application of time-resolved autofluorescence to label-free in vivo optical mapping of changes in tissue matrix and metabolism associated with myocardial infarction and heart failure

    , Biomedical Optics Express, Vol: 6, Pages: 324-346, ISSN: 2156-7085

    We investigate the potential of an instrument combining timeresolvedspectrofluorometry and diffuse reflectance spectroscopy tomeasure structural and metabolic changes in cardiac tissue in vivo in a 16week post-myocardial infarction heart failure model in rats. In the scarregion, we observed changes in the fluorescence signal that can beexplained by increased collagen content, which is in good agreement withhistology. In areas remote from the scar tissue, we measured changes in thefluorescence signal (p < 0.001) that cannot be explained by differences incollagen content and we attribute this to altered metabolism within themyocardium. A linear discriminant analysis algorithm was applied to themeasurements to predict the tissue disease state. When we combine allmeasurements, our results reveal high diagnostic accuracy in the infarctedarea (100%) and border zone (94.44%) as well as in remote regions fromthe scar (> 77%). Overall, our results demonstrate the potential of ourinstrument to characterize structural and metabolic changes in a failing heartin vivo without using exogenous labels.
  • Journal article
    Zaman JAB, Peters NS, Narayan SM, 2015,

    Rotor mapping and ablation to treat atrial fibrillation

    , CURRENT OPINION IN CARDIOLOGY, Vol: 30, Pages: 24-32, ISSN: 0268-4705
  • Journal article
    Petitjean C, Zuluaga MA, Bai W, Dacher J-N, Grosgeorge D, Caudron J, Ruan S, Ben Ayed I, Cardoso MJ, Chen H-C, Jimenez-Carretero D, Ledesma-Carbayo MJ, Davatzikos C, Doshi J, Erus G, Maier OMO, Nambakhsh CMS, Ou Y, Ourselin S, Peng C-W, Peters NS, Peters TM, Rajchi M, Rueckert D, Santos A, Shi W, Wang C-W, Wang H, Yuan Jet al., 2015,

    Right ventricle segmentation from cardiac MRI: A collation study

    , MEDICAL IMAGE ANALYSIS, Vol: 19, Pages: 187-202, ISSN: 1361-8415

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