Bidirectional Ventricular Tachycardia in a Young Female: A Case of Andersen-Tawil Syndrome

ABSTRACT Bidirectional ventricular tachycardia (VT) is a rare ventricular dysrhythmia with a limited differential diagnosis that includes digitalis toxicity, catecholaminergic polymorphic VT, aconite poisoning, and genetic channelopathy syndromes, specifically, Andersen–Tawil syndrome (ATS). We present a case of a young female with palpitations found to have bidirectional VT on cardiac event monitor and strong family history of cardiac dysrhythmias. Her physical examination findings included minor dysmorphic features of mandibular hypoplasia, hypertelorism, and clinodactyly. The patient was clinically diagnosed with ATS and started on a beta-blocker for control of ectopy. A second Holter review demonstrated markedly decreased burden of ventricular ectopy compared to the initial monitoring. She was referred for genetic testing, which revealed a KCNJ2 mutation. Bidirectional VT is an uncommon ventricular dysrhythmia that has a limited differential diagnosis, one of which is ATS—a rare genetic disorder that results from mutations in the KCNJ2 gene. The condition is frequently associated with developmental, skeletal, and cardiac abnormalities. Although there are no strong recommendations that exist for treatment of ventricular dysrhythmias associated with this genetic disorder, we demonstrate a case of clinical improvement in a patient with ATS by using the beta-blocker metoprolol succinate. Furthermore, we propose that ATS patients may not need exercise restrictions as overall ventricular ectopy burden decreased with exercise and there was no prolongation of the QT interval. This patient will continue to follow up in our clinic to reassess symptom burden and for continued monitoring for the development of any new features.

Antiarrhythmic Properties of Phenytoin

BACKGROUND: Phenytoin has long been used to treat epilepsy and for some time as an antiarrhythmic drug (AAD). It is known that the diastolic calcium leakage through dysfunctional cardiac ryanodine receptors (RyR2) is a mechanism for arrhythmias in heart failure. Recent evidence suggests that phenytoin inhibits dysfunctional RyR2, reduces the calcium leak during diastole in heart failure, and may improve cardiac systolic function. This indicates the potential for repurposing phenytoin as an AAD in patients with heart failure.METHODS: A systematic search of MEDLINE, Embase, and the Cochrane Library databases was performed in March 2019. The search was limited to the studies published in the English language from 1946 to 2019. Studies on the antiarrhythmic effects of phenytoin in adults compared to no treatment or other AADs were included. Studies were excluded if there was insufficient clinical data regarding antiarrhythmic effects, dosing and administration of phenytoin and other ADDs. Conference abstracts, editorials, case studies and review articles were also excluded. RESULTS: A total of 157 non-duplicate titles were screened, and 25 articles underwent full-text review. 13 studies met the inclusion criteria, representing a total of 985 patients. Phenytoin was found to be effective in treating arrhythmias associated with digitalis toxicity, and in suppressing premature ventricular contractions (PVCs). In a recent animal study, phenytoin inhibited diastolic calcium leak through dysfunctional RyR2 in failing sheep hearts and improved cardiac systolic function without affecting normal functional RyR2.CONCLUSION: Phenytoin has an acceptable safety profile when used as an AAD. It has some utility in treating digitalis-induced arrhythmias and suppressing PVCs, however, further study is needed to determine its efficacy as an antiarrhythmic in heart failure patients given new evidence of its RyR2 stabilising properties.TRIAL REGISTRATION NUMBER: PROSPERO database (CRD42019129125).

Transient bilateral chorea secondary to digoxin toxicity in a female with acute kidney injury: a case report

Background Chorea secondary to digoxin toxicity is rare, with only three published cases describing the phenomenon. We report the case of a 78-year-old female presenting with intermittent vomiting and diarrhoea for 4 weeks. She had a history of chronic kidney disease and digoxin use for atrial fibrillation. Case summary A 78-year-old lady presented to the emergency department with a 4-week history of intermittent vomiting and diarrhoea. These symptoms commenced after a course of antibiotics prescribed by her general practitioner for a urinary tract infection. Her admission electrocardiogram demonstrated atrial fibrillation at a rate of 32, with evidence of digitalis toxicity. Her creatinine was 396 µmol/L (44–80 µmol/L) with digoxin level 8.1 nmol/L (0.77–1.5 nmol/L). Initially, treatment was with digoxin-specific antibody (FAB) and fluid resuscitation. Within 24 h, she developed transient head, neck, and bilateral upper limb chorea. Review of medications revealed no other likely causative agent. Neuroimaging showed no new ischaemia, but stable established bilateral infarcts of the basal ganglia. Haloperidol 0.5 mg twice daily was commenced. Three days later as digoxin levels normalized, the chorea resolved entirely without recurrence. Discussion We have identified three reported cases of digoxin-induced chorea. Our case resembles two of the published cases where a transient bilateral chorea, associated with digitalis toxicity and resolving within a few days of normalization of digoxin levels was demonstrated. There were no other focal neurological signs or symptoms. It has been postulated that an alteration to dopaminergic neuronal activity is a potential mechanism, as digoxin also demonstrates neuropsychiatric side effects such as psychosis and depression.

Difficult Atrial Fibrilation Rate-Control and Digitalis Toxicity in Mitral-Valve Prolapse Patient with Hyperthyroidism

Rate-control is important management in patient with atrial fibrillation. The optimum rate control provides a decrease of symptoms, improves hemodynamics and prevents tachycardia-induced cardiomyopathy. Rate-control could be difficult to achieve because of patient's comorbidities and special treatment strategy is needed to resolve it. A-46-yo. male, came to ER with palpitation. Holosystolic murmur was heard at apex, radiating to axilla. ECG showed atrial fibrillation, with rapid ventricular response 180 bpm. Echocardiography showed dilated LA and LV, false-normal LV function with EF 59% and anterior mitral-valve prolapse with moderate mitral regurgitation. Acute treatment was administration of digoxin and beta blockers, but ventricular rate wasn’t controlled, until 1.5 mg doses of digoxin was administered. Then patient develops acute digitalis intoxication. After toxicity management, rapid ventricular rate recurs. Patient reevaluation showed hyperthyroidism with low TSH and high T4. Methimazole and propranolol was given and rate-control was achieved shortly after euthyroid state, in 2 months treatment. This patient suffered difficult rate-control despite guidelines-based management. Digitalis intoxication was developed after administration of several therapeutic doses. The diagnosis of hyperthyroidism is central in management of this case. Coexistent of hyperthyroidism and mitral-valve prolapse may be explained by genetic, autoimmune, and thyroid hormone effects in myocardium.