Objective: One of the most important side effects of opioids is their influence on the electrical activity of the heart. This review focusses on the effects of opioids on QT interval prolongation and their arrhythmogenic liability. Methods: By using various keywords, papers published up to 2018 in different databases were searched and identified. The search terms were opioids names, corrected QT interval, human-ether-a-go-go gene, torsades de pointes (TdP), cardiac arrhythmias, opioid dependence and other relevant terms. It emphasized the effects of each opioid agent alone on electrocardiogram (ECG) and some interactions. Results: Available data indicate that some opioids such as methadone are high-risk even at low doses, and have potential for prolongation of the QT interval and development of TdP, a dangerous ventricular tachycardia. A number of opioids such as tramadol and oxycodone are intermediate risk drugs and may develop long QT interval and TdP in high doses. Some other opioids such as morphine and buprenorphine are low-risk drugs and do not produce QT interval prolongation and TdP at least in routine doses. Opium-consumers are at higher risk of supra-ventricular arrhythmias, sinus bradycardia, cardiac block and atrial fibrillation. Conclusion: The cardiac arrhythmogenicity of various opioids is different. Methadone has a higher capability to induce long QT interval and dangerous arrhythmias in conventional doses than others. To reduce of arrhythmogenic risk, high doses of opioids must be used cautiously with periodic monitoring of ECG in high-risk consumers such as patients under opioid maintenance treatment.

Objective: We aimed to assess the influence of Melissa officinalis (lemon balm), a well-known herbal drug with numerous applications in traditional and modern medicine, on cardiac conduction and susceptibility to lethal ventricular arrhythmia. Materials and Methods: Forty-two male Wistar rats were divided into a control group (CTL), an M. officinalis group that received the aqueous extract of M. officinalis L. intraperitoneally (i.p.) at dosages of 50, 100, 200 and 400 mg/ml/kg, respectively, and an amiodarone group (Amio group) that received 30 mg/ml/kg i.p. of amiodarone. Heart ischemia/reperfusion was induced by the ligation and release of the left anterior descending branch of the left coronary artery. Results: There were no statistical differences between the groups in the basal heart rate and blood pressure. PR, corrected QT (QTc) and QRS intervals increased in the M. officinalis and Amio groups. PR and QTc were statistically significant only in the Amio group and QRS was significant only in the group receiving 400 mg of M. officinalis (M400 group) in comparison with the CTL group. During the reperfusion period, the decrease in ventricular fibrillations was statistically significant in all groups (except the M400 group) when compared with the CTL group. The score of arrhythmia severity also decreased, but was statistically significant only in the Amio group (p < 0.05 vs. CTL group). Conclusions: Our findings suggest that M. officinalis extract has a mild protective effect against reperfusion-induced lethal ventricular arrhythmias in rats.

This study was designed to assess the effects of saffron (Crocus sativus) on rats' heart with isoproterenol-induced myocardial injury. Animals were divided randomly into four groups: vehicle-control group (CTL); ISO group, administrated with Isoproterenol 85 mg/kg s.c.; saffron group; and finally combined Saffron + ISO group. Basal and final serum levels of heart troponin I, heart tissue antioxidants and histopathological indices were assessed in all groups. Isoproterenol administration significantly increased serum level of troponin I when compared to control group (3.46 +/- 0.77 vs. 0.53 +/- 0.35 ml in ng/ml, P < 0.001) and reduced significantly the glutathione peroxidase activity of heart muscle (1.63 +/- 0.21 vs. 4.01 +/- 0.64 nmol/mg protein, P < 0.05). The grade of heart muscle damages was severe in more than 70% of ISO group animals. Saffron + ISO group showed remarkably decreased intensity of tissue destruction and significantly decreased serum levels of heart troponin I, when compared to ISO group (1.25 +/- 0.23 vs. 3.46 +/- 0.77 ng/ml, P < 0.05). The level of glutathione peroxidase activity in Saffron + ISO animals did not have significant decline compared to saffron alone. These results suggest the protective role of saffron on ischemic hearts by biochemical and histopathological findings.

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Context: Saffron (Crocus sativus L.) has been used as a cuisine spice in eastern and western societies for thousands of years. In traditional medicine, saffron is recommended for the treatment of various kinds of disorders including heart palpitations. Objective: We investigated the hypothesis of the protective effect of saffron on lethal cardiac arrhythmias induced by heart ischemia-reperfusion in rat. Materials and methods: Animals were divided into a control (CTL) group that received tap water, Saf50, Saf100 and Saf200 groups that were orally treated with aqueous extracts of saffron, at dosages of 50, 100 and 200 mg/kg/day, respectively, and amiodarone (Amio) group that orally received 30 mg/kg/day for seven days. On day 8, heart ischemia-reperfusion was induced by ligation and releasing of the left anterior descending coronary artery. Results: During reperfusion, the numbers and durations of ventricular fibrillation (VF) decreased in all groups compared to the CTL group (p50.05). Ventricular tachycardia (VT)/VF numbers (3.2 AE 1.2), durations (4.9 AE 2.6) and also arrhythmia severity (1.9 AE 0.35) were decreased significantly in the Saf100 group versus CTL group values (18.4 AE 11.6, 52 AE 31 and 3.3 AE 0.3, respectively). The PR and QTcn intervals of ECG were significantly longer in the Saf200 group (p50.001 versus CTL). The other doses of saffron only significantly prolonged the QTcn interval. Conclusion:The results suggest that pretreatment with saffron, especially at the dosage of 100 mg/kg/day, attenuates the susceptibility and incidence of fatal ventricular arrhythmia during the reperfusion period in the rat. This protective effect is apparently mediated through reduction of electrical conductivity and prolonging the action potential duration.

Some Asian people believe that opium can protect the cardiovascular system. To assess this belief, we investigated the effect of passive opium smoking (POS) on cardiovascular indices in rabbits with ischemic and non-ischemic hearts.Rabbits (n = 43) were divided into control (CTL), short term opium (SO) and long term opium (LO) groups. SO and LO groups were exposed to opium smoking for 3 days and 4 weeks, respectively. ECG, blood pressure (BP), left ventricular pressure and cardiac troponin I levels were recorded. Isoproterenol (ISO) was injected to induce cardiac ischemia and after 4 h the above variables were measured along with cardiac histopathology assessment.All groups showed significant increments in troponin I level (P < 0.05) except the CTL group. This trend was more obvious in ISO-treated groups. Mean arterial pressure (MAP) significantly decreased in all groups (p< 0.05) except the LO group. Opium exposure attenuated ISO-induced myodegeneration but augmented tissue congestion and hemorrhage.In conclusion, higher troponin I serum level and ECG changes were found in passive opium smoking groups. This evidence is against the belief that opium can protect the cardiovascular system.