Effects of pink grapefruit juice on QT variability in patients with dilated or hypertensive cardiomyopathy and in healthy subjects.

Recent evidence shows that pink grapefruit juice, which is a recommended dietary addition that contains high amounts of the antioxidant flavonoid naringenin, prolongs the corrected QT (QT(c)), a noninvasive electrophysiological marker of spatial myocardial repolarization, and does so by inhibiting the rapid component of the delayed rectifier K+ current (I(Kr)). Prompted by the observation that all class III antiarrhythmic drugs inhibit this current, thereby sometimes provoking torsades de pointes, we compared the effects of a liter of freshly squeezed pink grapefruit juice with those of 2 commonly used class III antiarrhythmics amiodarone and sotalol on the major noninvasive markers of temporal variability in myocardial repolarization used to stratify the risk of sudden death from malignant ventricular arrhythmias. In 32 subjects, 10 with postischemic dilated cardiomyopathy, 12 with hypertensive cardiomyopathy, and 10 healthy, we assessed QT(c) and QT variability index (QTVI) after administration of fresh pink grapefruit juice, placebo, amiodarone, or sotalol.

Early impairment of myocardial function in young patients with beta-thalassemia major.

Background And Objective: One of the chief causes of death in patients with beta-thalassemia major (TM) remains heart failure due to iron overload. We investigated possible differences in myocardial function between a population of young asymptomatic patients with TM and healthy controls all of whom underwent an echocardiographic study, including tissue Doppler (TDI) and strain imaging (SI) analysis and cardiac magnetic resonance imaging (MRI).

Methods: 30 young asymptomatic patients with TM (16 taking deferoxamine and 14 taking deferiprone) and 30 healthy subjects underwent a cardiac MRI with T2* technique and an echocardiographic evaluation including systolic myocardial velocities (Sm), early (Em) and late (Am) diastolic velocities and systolic strain (S) at the level of basal segments of the lateral left ventricle (LV), interventricular septum (Septal) and lateral right ventricle (RV) wall.

Increased QT variability in young asymptomatic patients with beta-thalassemia major.

Background: Despite recent progress in iron chelation therapy, sudden cardiac death due to malignant ventricular arrhythmias remains a vexing, clinical problem in patients with beta-thalassemia major (TM). In this study we assessed whether the major indices of QT variability, emerging tools for risk stratification of sudden cardiac death, differ in young asymptomatic patients with TM and healthy persons.

Methods: Thirty patients with TM and 30 healthy control subjects underwent a 5-min electrocardiography recording to calculate the following variables: QT variance (QT(v)), QT(v) normalized for mean QT (QTVN) and QT variability index (QTVI).

QT variability strongly predicts sudden cardiac death in asymptomatic subjects with mild or moderate left ventricular systolic dysfunction: a prospective study.

Aims: The most widely accepted marker for stratifying the risk of sudden cardiac death (SCD) in post myocardial infarction patients is a depressed left ventricular function. Left ventricular ejection fractions (EF) of 35% or less increase the risk of sudden death but values between 35 and 40% raise concern. The underlying pathophysiological mechanism is sustained ventricular tachycardia or fibrillation, both associated with increased cardiac repolarization variability.