Prolongation of the QT interval in heart failure occurs at low but not at high heart rates.
نویسندگان
چکیده
Abnormal left ventricular structure and function as in, for example, left ventricular hypertrophy or chronic heart failure, is associated with sudden cardiac death and, when the ejection fraction is depressed, with prolongation of the QT interval. The dependence on heart rate of QT interval prolongation in these conditions, and the relationship of any abnormalities either to deranged autonomic nervous system function or to an adverse prognosis, has not been well studied. We therefore investigated (1) the dependence on heart rate of the QT interval, and (2) the relationship between both QT interval and the QT/heart rate slope and markers of adverse prognosis in these two conditions. The QT interval was measured at rest and during exercise in 34 subjects with heart failure, 16 subjects with left ventricular hypertrophy and 16 age-matched controls with normal left ventricular structure and function. QTc (corrected QT) intervals at rest were significantly longer in heart failure patients (471+/-10 ms) than in controls (421+/-6 ms) or in subjects with hypertrophy (420+/-6 ms) (P<0.05). At peak exercise, despite the attainment of similar heart rates, the QT intervals no longer differed from each other, being 281+/-7 ms for controls, 296+/-11 ms in hypertrophy and 303+/-10 ms in heart failure (no significant difference). The QT/heart rate slope was significantly increased in heart failure [2.3+/-0.1 ms.(beats/min)(-1)] compared with controls [1.55+/-0.06 ms.(beats/min)(-1)] and hypertrophy [1. 66+/-0.1 ms.(beats/min)(-1)] (P<0.001). In left ventricular hypertrophy, despite animal data suggesting that QT interval prolongation should occur, no abnormalities were found in QT intervals at rest or during exercise. The QT/heart rate slope did not relate to any markers for an adverse prognosis, except that of prolongation of QT interval. Long QT intervals were associated principally with impairment of left ventricular systolic function. Our data emphasize the dynamic nature of the QT interval abnormalities found in heart failure.
منابع مشابه
Drug induced QT prolongation: the measurement and assessment of the QT interval in clinical practice.
There has been an increasing focus on drug induced QT prolongation including research on drug development and QT prolongation, following the removal of drugs due to torsades de pointes (TdP). Although this has improved our understanding of drug-induced QT prolongation there has been much less research aimed at helping clinicians assess risk in individual patients with drug induced QT prolongati...
متن کاملBackground & Objective : Heart failure is a clinical syndrome and increases in rate by aging. Because changes in ECG and electrolytes are variable, specific and sometimes independent to the disease with different methods to be diagnosed, in this study we tried to find a way to diagnose them. Materials & Methods: This is a retrospective descriptive-analytic study. Data was collected from dec...
متن کاملQT Measurement and Heart Rate Correction during Hypoglycemia: Is There a Bias?
Introduction. Several studies show that hypoglycemia causes QT interval prolongation. The aim of this study was to investigate the effect of QT measurement methodology, heart rate correction, and insulin types during hypoglycemia. Methods. Ten adult subjects with type 1 diabetes had hypoglycemia induced by intravenous injection of two insulin types in a cross-over design. QT measurements were d...
متن کاملQ-T interval prolongation in cirrhosis: Relationship and severity
Background: Cirrhosis as the final stage of progressive fibrosis of liver can affect other organs such as lungs, kidneys and heart. "Cirrhotic cardiomyopathy" involves the electrophysiological abnormalities such as QT interval prolongation. We assessed correlation between corrected QT interval prolongation and severity of cirrhosis based on Child Classification in each ECG lead. ...
متن کاملهای اسید گلوتامیک، تریپتوفان، آلانین tRNA بررسی مولکولی در Long QT وآسپارژین درژنوم میتوکندری بیماران مبتلا بهسندرم مقایسه با گروه کنترل
Background and purpose: Long QT syndrome is a heart arrhythmia identified by prolongation of the QT interval which is a cause of sudden cardiac death in young individuals. In most cases, abnormalities in heart repolarization are reasons of prolongation of action potential and arrhythmia. The activity of ion channels is sensitive to ATP level, therefore, mitochondrial disorders are considered...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Clinical science
دوره 98 5 شماره
صفحات -
تاریخ انتشار 2000