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Emotionally charged events are associated with an increased risk of sudden cardiac death (SCD). In this study we assessed RR and QT variability index (QTVI) at baseline during anger recall test (AR). We calculated QTVI from a 5-min ECG recording and from a 10-beats segment around the presumed maximum sympathetic activation in thirty post-myocardial infarction patients under β-blocker therapy and 10 controls underwent. In all groups, the low-frequency component of RR and SBP increased during AR. In all recordings, the QTVI calculated on a 5-min ECG recording and the QTVI(10 beats) were higher in patients than in controls (P < 0.05). The QTVI during AR remained unchanged from baseline within each group. Conversely, during AR, the QTVI(10 beats) in controls diminished significantly (P < 0.05) from baseline whereas in patients remained unchanged. The inability to buffer an acute stress-induced increase in sympathetic activity could explain why events charged with acute stress are associated with an increased risk of ventricular arrhythmias in this setting of patients and support the role of cognitive behavior stress management strategies.

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. After pink grapefruit juice and sotalol, all these indexes increased significantly from values observed after placebo (P<0.05) and from values after amiodarone (P<0.05). Conversely, after amiodarone, QT(c), but not QTVI, increased significantly from values after placebo (P<0.05). Presumably because of its high naringenin glycoside content, pink grapefruit juice prolongs cardiac repolarization and concurrently increases temporal cardiac repolarization dispersion. The potential proarrhythmic actions of pink grapefruit juice might be of concern in patients with major myocardial structural disorders.