{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,11]],"date-time":"2026-03-11T22:48:06Z","timestamp":1773269286416,"version":"3.50.1"},"reference-count":42,"publisher":"Ovid Technologies (Wolters Kluwer Health)","issue":"4","content-domain":{"domain":["www.ahajournals.org"],"crossmark-restriction":true},"short-container-title":["JAHA"],"published-print":{"date-parts":[[2012,8,6]]},"abstract":"<jats:sec xml:lang=\"en\">\n            <jats:title>Background<\/jats:title>\n            <jats:p xml:lang=\"en\">Better sudden cardiac death risk markers are needed in ischemic cardiomyopathy (ICM). Increased heterogeneity of electrical restitution is an important mechanism underlying the risk of ventricular arrhythmia (VA). Our aim was to develop and test a novel quantitative surface electrocardiogram\u2013based measure of VA risk in patients with ICM: the Regional Restitution Instability Index (R2I2).<\/jats:p>\n          <\/jats:sec>\n          <jats:sec xml:lang=\"en\">\n            <jats:title>Methods and Results<\/jats:title>\n            <jats:p xml:lang=\"en\">\n              R2I2, the mean of the standard deviation of residuals from the mean gradient for each ECG lead at a range of diastolic intervals, was measured retrospectively from high\u2010resolution 12\u2010lead ECGs recorded during an electrophysiology study. Patient groups were as follows: Study group, 26 patients with ICM being assessed for implantable defibrillator; Control group, 29 patients with supraventricular tachycardia undergoing electrophysiology study; and Replication group, 40 further patients with ICM. R2I2 was significantly higher in the Study patients than in Controls (mean\u00a0\u00b1\u00a0standard error of the mean: 1.09\u00b10.06 versus 0.63\u00b10.04,\n              <jats:italic>P<\/jats:italic>\n              &lt;0.001). Over a median follow\u2010up period of 23\u00a0months, 6 of 26 Study group patients had VA or death. R2I2 predicted VA or death independently of demographic factors, electrophysiology study result, left ventricular ejection fraction, or QRS duration (Cox model,\n              <jats:italic>P<\/jats:italic>\n              =0.029). R2I2 correlated with peri\u2010infarct zone as assessed by cardiac magnetic resonance imaging (r=0.51,\n              <jats:italic>P<\/jats:italic>\n              =0.024). The findings were replicated in the Replication group: R2I2 was significantly higher in 11 of 40 Replication patients experiencing VA (1.18\u00b10.10 versus 0.92\u00b10.05,\n              <jats:italic>P<\/jats:italic>\n              =0.019). In combined analysis of ICM cohorts, R2I2 \u22651.03 identified subjects with significantly higher risk of VA or death (43%) compared with R2I2 &lt;1.03 (11%) (\n              <jats:italic>P<\/jats:italic>\n              =0.004).\n            <\/jats:p>\n          <\/jats:sec>\n          <jats:sec xml:lang=\"en\">\n            <jats:title>Conclusions<\/jats:title>\n            <jats:p xml:lang=\"en\">\n              In this pilot study, we have developed a novel VA risk marker, R2I2, and have shown that it correlated with a structural measure of arrhythmic risk and predicted risk of VA or death in patients with ICM. R2I2 may improve risk stratification and merits further evaluation. (\n              <jats:bold>\n                <jats:italic>J Am Heart Assoc<\/jats:italic>\n                . 2012;1:e001552 doi\n              <\/jats:bold>\n              :\n              <jats:ext-link xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" ext-link-type=\"doi\" xlink:href=\"10.1161\/JAHA.112.001552\">10.1161\/JAHA.112.001552<\/jats:ext-link>\n              .)\n            <\/jats:p>\n          <\/jats:sec>","DOI":"10.1161\/jaha.112.001552","type":"journal-article","created":{"date-parts":[[2012,9,21]],"date-time":"2012-09-21T17:49:16Z","timestamp":1348249756000},"update-policy":"https:\/\/doi.org\/10.1161\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":24,"title":["A Novel Surface Electrocardiogram\u2013Based Marker of Ventricular Arrhythmia Risk in Patients With Ischemic Cardiomyopathy"],"prefix":"10.1161","volume":"1","author":[{"given":"William B.","family":"Nicolson","sequence":"first","affiliation":[{"name":"From the Department of Cardiovascular Sciences,\rUniversity of Leicester"},{"name":"National Institute for Health Research Leicester Cardiovascular Biomedical Research Unit,\rGlenfield Hospital"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Gerry P.","family":"McCann","sequence":"additional","affiliation":[{"name":"National Institute for Health Research Leicester Cardiovascular Biomedical Research Unit,\rGlenfield Hospital"},{"name":"University Hospitals of Leicester NHS Trust,\rLeicester, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Peter D.","family":"Brown","sequence":"additional","affiliation":[{"name":"From the Department of Cardiovascular Sciences,\rUniversity of Leicester"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Alastair J.","family":"Sandilands","sequence":"additional","affiliation":[{"name":"University Hospitals of Leicester NHS Trust,\rLeicester, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Peter J.","family":"Stafford","sequence":"additional","affiliation":[{"name":"University Hospitals of Leicester NHS Trust,\rLeicester, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Fernando S.","family":"Schlindwein","sequence":"additional","affiliation":[{"name":"Department of Engineering,\rUniversity of Leicester"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Nilesh J.","family":"Samani","sequence":"additional","affiliation":[{"name":"From the Department of Cardiovascular Sciences,\rUniversity of Leicester"},{"name":"National Institute for Health Research Leicester Cardiovascular Biomedical Research Unit,\rGlenfield Hospital"},{"name":"University Hospitals of Leicester NHS Trust,\rLeicester, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"G. Andr\u00e9","family":"Ng","sequence":"additional","affiliation":[{"name":"From the Department of Cardiovascular Sciences,\rUniversity of Leicester"},{"name":"National Institute for Health Research Leicester Cardiovascular Biomedical Research Unit,\rGlenfield Hospital"},{"name":"University Hospitals of Leicester NHS Trust,\rLeicester, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"276","reference":[{"key":"e_1_3_4_2_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0002-9149(97)00477-3"},{"key":"e_1_3_4_3_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.ahj.2007.01.024"},{"key":"e_1_3_4_4_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.ahj.2007.03.002"},{"key":"e_1_3_4_5_2","doi-asserted-by":"publisher","DOI":"10.1161\/01.RES.14.1.44"},{"key":"e_1_3_4_6_2","doi-asserted-by":"publisher","DOI":"10.1161\/01.CIR.67.6.1356"},{"key":"e_1_3_4_7_2","doi-asserted-by":"publisher","DOI":"10.1186\/1475-925X-4-54"},{"key":"e_1_3_4_8_2","doi-asserted-by":"publisher","DOI":"10.1124\/jpet.105.095471"},{"key":"e_1_3_4_9_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.jelectrocard.2007.10.001"},{"key":"e_1_3_4_10_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.jacc.2009.01.056"},{"key":"e_1_3_4_11_2","doi-asserted-by":"publisher","DOI":"10.1161\/CIRCULATIONAHA.106.613414"},{"key":"e_1_3_4_12_2","doi-asserted-by":"publisher","DOI":"10.1161\/CIRCULATIONAHA.106.653568"},{"key":"e_1_3_4_13_2","unstructured":"National Institute for Health and Clinical Excellence . January 2006. Implantable cardioverter defibrillators for arrhythmias Review of Technology Appraisal 11. TA95. London: National Institute for Health and Clinical Excellence. 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