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Repolarization Abnormalities (repolarization + abnormality)

Distribution by Scientific Domains

Medical Sciences	100%

Selected Abstracts

Repolarization Abnormality in Idiopathic Ventricular Fibrillation:

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2004
Assessment Using 24-Hour QT-RR, QaT-RR Relationships
Introduction: We evaluated the characteristics of QT-RR and QaT (apex of T wave)-RR relationships in patients with idiopathic ventricular fibrillation (IVF) compared with control subjects. We hypothesized that IVF patients have unique repolarization dynamics related to a reduced fast Na current and a prominent transient outward current. Methods and Results: The study group consisted of 9 men (age 47 ± 10 years) with IVF (6 with Brugada type and 3 with non-Brugada type) who had experienced nocturnal episodes of VF. The control group consisted of 28 healthy age-matched men (age 44 ± 12 years). The relationships between QT and RR intervals and between QaT and RR intervals were analyzed from 24-hour Holter ECG data using an automatic measurement system. Both QT and QaT at RR intervals of 0.6, 1.0, and 1.2 seconds were determined from QT-RR and QaT-RR linear regression lines. Both QT-RR and QaT-RR slopes were lower in the IVF group than in the control group (QT-RR: 0.092 ± 0.023 vs 0.137 ± 0.031, P < 0.001; QaT-RR: 0.109 ± 0.025 vs 0.153 ± 0.028, P < 0.001). QT at an RR interval of 0.6 second did not differ between two groups, but QT at RR intervals of either 1.0 or 1.2 seconds was significantly shorter in the IVF group than in the control group (RR 1.0 s: 0.384 ± 0.018 vs 0.399 ± 0.017, P < 0.05; RR 1.2 s: 0.402 ± 0.019 vs 0.426 ± 0.020, P < 0.01). QaT at RR intervals of either 1.0 or 1.2 seconds also was shorter in the IVF group (RR 1.0 s: 0.289 ± 0.022 vs 0.312 ± 0.021, P < 0.01; RR 1.2 s: 0.311 ± 0.024 vs 0.343 ± 0.024, P < 0.01). In four patients, oral administration of disopyramide (300 mg/day) was effective in suppressing VF episodes and increased slopes of QT-RR and QaT-RR relationships. Conclusion: IVF patients had lower slopes of QT-RR and QaT-RR regression lines and impaired prolongation of QT and QaT at longer RR intervals compared with control subjects. These unique repolarization dynamics may be related to the frequent occurrence of VF episodes at night. (J Cardiovasc Electrophysiol, Vol. 15, pp. 59-63, January 2004) [source]

Modelling and imaging cardiac repolarization abnormalities

JOURNAL OF INTERNAL MEDICINE, Issue 1 2006
Y. RUDY
Abstract. Repolarization abnormalities, including those induced by the congenital or acquired long QT (LQT) syndrome, provide a substrate for life-threatening cardiac arrhythmias. In this article, we use computational biology to link HERG mutations mechanistically to the resulting abnormalities of the whole-cell action potential. We study how the kinetic properties of IKs (the slow delayed rectifier) that are conferred by molecular subunit interactions, facilitate its role in repolarization and ,repolarization reserve'. A new noninvasive imaging modality (electrocardiographic imaging) is shown to image cardiac repolarization on the epicardial surface, suggesting its possible role in risk stratification, diagnosis and treatment of LQT syndrome. [source]

Heart Rate Changes and ECG Abnormalities During Epileptic Seizures: Prevalence and Definition of an Objective Clinical Sign

EPILEPSIA, Issue 8 2002
Maeike Zijlmans
Summary: ,Purpose: To determine the prevalence of heart rate changes and ECG abnormalities during epileptic seizures and to determine the timing of heart rate changes compared to the first electrographic and clinical signs. To assess the risk factors for the occurrence of ECG abnormalities. Methods: We analyzed retrospectively 281 seizures in 81 patients with intractable epilepsy who had prolonged video-EEG and two-channel ECG. The nature and timing of heart rate changes compared to the electrographic and clinical seizure onset was determined. The ictal period (including one minute preictally and three minutes postictally) was analyzed for cardiac arrhythmias, conduction and repolarization abnormalities. Risk factors for cardiac abnormalities were investigated using parametric and non-parametric statistics. Results: There was an increase in heart rate of at least 10 beats/minute in 73% of seizures (93% of patients) and this occurred most often around seizure onset. In 23% of seizures (49% of patients) the rate increase preceded both the electrographic and the clinical onset. ECG abnormalities were found in 26% of seizures (44% of patients). One patient had an asystole for 30 seconds. Long seizure duration increased the occurrence of ECG abnormalities. No other risk factor was found. Conclusions: Heart rate changes occur frequently and occur around the time or even before the earliest electrographic or clinical change. The change can clarify the timing of seizure onset and the specific rate pattern may be useful for seizure diagnosis and for automatic seizure detection. ECG abnormalities occur often and repeatedly in several seizures of the same patient. [source]

Modelling and imaging cardiac repolarization abnormalities

Epsilon-Like Electrocardiographic Pattern in a Patient with Brugada Syndrome

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 3 2009
Ozcan Ozeke M.D.
Both Brugada syndrome (BrS) and arrhythmogenic right ventricle dysplasia/cardiomyopathy (ARVD/C) can cause repolarization abnormalities in right precordial leads and predispose to sudden cardiac death (SCD) due to ventricular arrhythmias. Although there is controversy over whether BrS is distinct from ARVD/C, it is believed that both are different clinical entities with respect to both the clinical presentation and the genetic predisposition. The coexistence of these two relatively rare clinical entities is also reported, but, some hypothesized that it is more possible that disease of the right ventricular muscle might accentuate the Brugada electrocardiographic pattern. In clinic practice, there may be cases where the dividing line is not so clear. We report a 33-year-old male presenting with recurrent syncope, who has a peculiar pattern of coved-type ST-segment elevation (ST-SE) with epsilon-like wave in right precordial leads. [source]

Beat-to-Beat QT Dynamics in Healthy Subjects

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 1 2004
Berit T. Jensen M.D.
Background: Measures of QT dynamics express repolarization abnormalities that carry prognostic information, but the reproducibility of beat-to-beat QT dynamics has never been established. The QT interval is prolonged at night, but how the circadian rhythm and heart rate influence the dynamic QT measurements is still unsettled. The aims of the present study were: (1) to describe the reproducibility of beat-to-beat QT dynamics with respect to intrasubject, between-subject, and between-observer variability and (2) to describe the normal range, circadian variation, and heart rate dependence of QT dynamics. Methods: Ambulatory Holter recordings were performed three times on 20 healthy volunteers and were analyzed by two experienced cardiologists. Slope and intercept of the QT/RR regression, the variability of QT and R-R intervals expressed as the standard deviation, and the relation between QT and RR variability expressed as a variability ratio were measured among other QT dynamics. Results: The reproducibility of all QT dynamics was good. All QT dynamics showed circadian variation when calculated on an hourly basis. The day/night variation in slope could be explained by the differences in heart rate, whereas the day/night variation in intercept was heart rate independent. Conclusion: The present study shows that reliable automatic QT measurements could be performed, encouraging further evaluation of the clinical value of QT dynamics in risk stratification of cardiac patients. [source]

Electrocardiographic Transmural Dispersion of Repolarization in Patients with Inherited Short QT Syndrome

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 3 2008
Olli Anttonen M.D.
Background: Short QT syndrome (SQTS) carries an increased risk for sudden cardiac death. However, only a short QT interval does not express the risk of ventricular arrhythmias. Thus, additional evaluation of the repolarization abnormality in SQTS patients is essential. In experimental models of SQTS, increased transmural dispersion of repolarization (TDR) and its electrocardiographic counterpart T-wave peak to T-wave end interval (TPE) appeared critical for induction of polymorphic ventricular tachycardia (PMVT). In a clinical study with acquired long QT syndrome patients, TPE/QT ratio > 0.28 indicated arrhythmia risk. We hypothesized that the TPE/QT ratio would be greater in SQTS patients than in control subjects. Methods and Results: We compared the behavior of the electrocardiographic TDR in three seriously symptomatic SQTS patients of unknown genotype presenting baseline QTc values <320 ms and in nine healthy age-matched control subjects. We determined QT and TPE intervals as well as TPE/QT ratio from 24-hour ECG recordings using a computer-assisted program. Diurnal average of TPE/QT ratio was 0.28 ± 0.03 in SQTS patients and 0.21 ± 0.02 in control subjects (P = 0.01). SQTS patients had also lesser capacity to change TPE intervals from steady-state conditions to abrupt maximal values than control subjects. Conclusion: SQTS patients have increased and autonomically uncontrolled electrocardiographic TDR. According to experimental SQTS models, the present results may in part explain increased vulnerability of SQTS patients to ventricular arrhythmias. [source]