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Early Repolarization: Difference between revisions
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Characterization of standard 12 lead ECG abnormalities can be facilitated by considering the portion of the cardiac ventricular myocytes action potential which influences them. This is only helpful for action potential phenomena originating with the initial wave of activation. Their temporal timing is influenced mainly by transmural dispersion from endo to epicardium. This contrasts with late potentials which are due to phase 0 of the action potentials (depolarization) originating from myocardium isolated by fatty tissue (epsilon waves of ARVD) or by fibrosis (cardiomyopathy) experiencing major delays. These can be arrhythmogenic because they compete with the normal pacemakers. | Characterization of standard 12 lead ECG abnormalities can be facilitated by considering the portion of the cardiac ventricular myocytes action potential which influences them. This is only helpful for action potential phenomena originating with the initial wave of activation. Their temporal timing is influenced mainly by transmural dispersion from endo to epicardium. This contrasts with late potentials which are due to phase 0 of the action potentials (depolarization) originating from myocardium isolated by fatty tissue (epsilon waves of ARVD) or by fibrosis (cardiomyopathy) experiencing major delays. These can be arrhythmogenic because they compete with the normal pacemakers. | ||
[[Image:projects_repolarization_15_4227574443.jpg|thumbnail|300px|right|The Different Phases of Repolarization.]] | |||
Phase 0 depolarization abnormalities that occur with the initial wave of activation include bundle branch blocks, myocardium damage or abnormalities and intraventicular delays. These can be due to electrical disturbances, myocardial hypertrophy, dilatation, damage or infiltrative disease. | Phase 0 depolarization abnormalities that occur with the initial wave of activation include bundle branch blocks, myocardium damage or abnormalities and intraventicular delays. These can be due to electrical disturbances, myocardial hypertrophy, dilatation, damage or infiltrative disease. | ||
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Phase 3 (late-repolarization) abnormalities can result in T wave abnormalities with similar causes as ST depression as well as abnormalities of QT length caused by medications, electrolyte disturbances and specific genetic conditions (LQTS, SQTS). | Phase 3 (late-repolarization) abnormalities can result in T wave abnormalities with similar causes as ST depression as well as abnormalities of QT length caused by medications, electrolyte disturbances and specific genetic conditions (LQTS, SQTS). | ||
Less understood but recently highlighted are abnormalities of phase 1 (Early Repolarization). These include abnormal action potentials originating in the right ventricle outflow tract (Brugada syndrome) and those originating in the left ventricle (J wave syndromes). | Less understood but recently highlighted are abnormalities of phase 1 (Early Repolarization). These include abnormal action potentials originating in the right ventricle outflow tract (Brugada syndrome) and those originating in the left ventricle (J wave syndromes). | ||
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In fact, though this new, rare syndrome may be found to be more prevalent now that it has been discovered, nomenclature and ECG measurement disagreements could result in more harm than good. This is particularly the case since many of the widely used automated ECG machines put out a statement of ''Early Repolarization'' based on ST elevation in an otherwise normal ECG. | In fact, though this new, rare syndrome may be found to be more prevalent now that it has been discovered, nomenclature and ECG measurement disagreements could result in more harm than good. This is particularly the case since many of the widely used automated ECG machines put out a statement of ''Early Repolarization'' based on ST elevation in an otherwise normal ECG. | ||
{| class="wikitable" border="0" cellpadding="0' cellspacing="0" width="700px" | |||
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{| class="wikitable" border="0" cellpadding="0' cellspacing="0" | |colspan="2"|'''''The figures below compare two of the syndromes caused by abnormalities in phase 1 of the myocyte action potential.''''' | ||
|- | |- | ||
!Similarities | !Similarities | ||
!Differences | !Differences | ||
|- | |- | ||
|[[Image:projects_repolarization_21_272147016.JPG]] | |[[Image:projects_repolarization_21_272147016.JPG|300px|center]] | ||
|[[Image:projects_repolarization_23_1469634712.JPG]] | |[[Image:projects_repolarization_23_1469634712.JPG|300px|center]] | ||
|- | |||
|valign="bottom"|[[Image:projects_repolarization_23_684579393.jpg|300px|center]] | |||
|[[Image:projects_repolarization_23_401991672.jpg|300px|center]] | |||
|- | |- | ||
!Brugada ECG Pattern | !Brugada ECG Pattern | ||
!Haïssaguerre ECG Pattern | !Haïssaguerre ECG Pattern | ||
|} | |} | ||
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A sixth and seventh studies by Olson et al and Hisamatsu et al were excellent population studies but did not consider R wave downslope phenomena (Haïssaguerre Pattern) but only ST elevation and included the anterior leads. Uberoi et al from the Veterans Affairs was one of the largest multi-ethnic population studies and considered R wave downslope phenomena (Haïssaguerre Pattern) as well as ST elevation. | A sixth and seventh studies by Olson et al and Hisamatsu et al were excellent population studies but did not consider R wave downslope phenomena (Haïssaguerre Pattern) but only ST elevation and included the anterior leads. Uberoi et al from the Veterans Affairs was one of the largest multi-ethnic population studies and considered R wave downslope phenomena (Haïssaguerre Pattern) as well as ST elevation. | ||
[[Image:projects_repolarization_29_197264908.jpg|300px|right|thumbnail|The figure shows where the CSE experts indicated that these measurements be made.]] | |||
These eight studies are summarized in this spreadsheet [https://docs.google.com/spreadsheet/pub?hl=en&hl=en&key=0AhMCIH0M0pLYdGFhMVlGQ2RpX3VVUnJlYk1DRzlnU2c&single=true&gid=2&output=html Prognostic ''ER'' studies]. | These eight studies are summarized in this spreadsheet [https://docs.google.com/spreadsheet/pub?hl=en&hl=en&key=0AhMCIH0M0pLYdGFhMVlGQ2RpX3VVUnJlYk1DRzlnU2c&single=true&gid=2&output=html Prognostic ''ER'' studies]. | ||
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===ECG Measuement Issues=== | ===ECG Measuement Issues=== | ||
Before the prognostic significance of the Haïssaguerre Pattern can be demonstrated, there must be agreement on what measurments should be made. It appears that for stable ECG patterns with a QRS duration (including an end QRS slur J wave/slur) less than 120 msec, we should follow the CSE Measurement statement (1985)and consider the J point (also known as QRS end, J-junction, ST0[zero msec] or ST beginning) to occur after the R wave downslope notch/slur/or J wave as determined across all 12 leads. And that the measurement baseline be set in an interval immediately preceding QRS onset as per the CSE Measurement statement. Some of the bizarre and dynamic ECGs may require other rules for measurments but for now the CSE statement should be followed. | Before the prognostic significance of the Haïssaguerre Pattern can be demonstrated, there must be agreement on what measurments should be made. It appears that for stable ECG patterns with a QRS duration (including an end QRS slur J wave/slur) less than 120 msec, we should follow the CSE Measurement statement (1985)and consider the J point (also known as QRS end, J-junction, ST0[zero msec] or ST beginning) to occur after the R wave downslope notch/slur/or J wave as determined across all 12 leads. And that the measurement baseline be set in an interval immediately preceding QRS onset as per the CSE Measurement statement. Some of the bizarre and dynamic ECGs may require other rules for measurments but for now the CSE statement should be followed. | ||
==Summary== | ==Summary== | ||