BACKGROUND: Direct oral anticoagulants (DOACs) are commonly co-prescribed with amiodarone/diltiazem/verapamil, but whether there is a drug interaction between these drugs is unclear.
OBJECTIVE: The purpose of this study was to investigate the risk of clinical outcomes associated with concomitant use of DOACs and amiodarone/diltiazem/verapamil.
METHODS: We identified DOAC users in the Clinical Practice Research Datalink Aurum from January 1, 2011, to December 31, 2019. We used a cohort design to estimate hazard ratios for ischemic stroke, myocardial infarction, venous thromboembolism, intracranial bleeding, gastrointestinal bleeding, other bleeding, cardiovascular mortality, and all-cause mortality, comparing DOACs + amiodarone/diltiazem/verapamil users and DOACs + beta-blocker users. A case-crossover design comparing odds of exposure to different drug initiation patterns for all outcomes in hazard window vs referent window within an individual also was conducted.
RESULTS: Of 397,459 DOAC users, we included 9075 co-prescribed amiodarone, 9612 co-prescribed diltiazem, and 2907 co-prescribed verapamil. There was no difference in risk of any outcomes between DOACs + amiodarone/diltiazem/verapamil users vs DOACs + beta-blocker users in the cohort design. However, in the case-crossover design, we observed an odds ratio (OR) of 2.09 (99% confidence interval [CI] 1.37-3.18) for all-cause mortality associated with initiation of a DOAC while taking amiodarone, which was greater than that observed for DOAC monotherapy (OR 1.30; 99% CI 1.25-1.35). Similar findings were observed for cardiovascular mortality and all-cause mortality respectively with diltiazem.
CONCLUSIONS: Our study showed no evidence of higher bleeding or cardiovascular risk associated with co-prescribed DOACs and amiodarone, diltiazem, or verapamil. Elevated risks of cardiovascular and all-cause mortality were only observed during DOAC initiation when diltiazem/amiodarone were being taken.

Carbamazepine remains a first-line antiepileptic medication for the treatment of partial seizures. Despite its widespread use, carbamazepine has significant neurotoxicity and hypersensitivity reactions. We report a case of a patient post-kidney transplant who was on regular carbamazepine for childhood epilepsy and developed nystagmus, diplopia and a broad-base gait after receiving diltiazem. Understanding of the interaction between diltiazem and carbamazepine is necessary to prevent the neurotoxic effects.

BACKGROUND: Atrial arrhythmias such as paroxysmal supraventricular tachycardia (PSVT) and atrial flutter (AF) are common in the perioperative setting. They commonly resolve spontaneously. However, occasionally, they may continually progress to fatal arrhythmias or cause complications. Therefore, prompt and appropriate management is important.
METHODS: A 46-year-old female patient diagnosed with cervical C6-7 radiculopathy characterized by decreased sensation in the right third, fourth and fifth fingers underwent C6-7 anterior cervical disc fusion surgery. Electrocardiography showed PSVT and ventricular tachycardia during C6-7 disc retraction. However, the patient remained stable. Initial treatment with esmolol and lidocaine for ventricular tachycardia was ineffective. Carotid massage and Valsalva maneuver were attempted but PSVT did not resolve. The surgery was paused, and the patient\'s fraction of inspired oxygen was set to 100%. Adenosine was administered for pharmacological management of PSVT. The arrhythmia temporarily resolved. However, it then transformed into AF. Diltiazem was administered, which briefly decreased blood pressure, which immediately recovered. Surgery resumed while the patient was in normal sinus rhythm. She was discharged safely on postoperative day 6 without complications or abnormalities. Currently, she is living a healthy life without arrhythmia recurrence.
CONCLUSIONS: Ganglia associated with cardiac arrhythmias in the surgical site should be identified during cervical spine surgery.

BACKGROUND: Atrial flutter with 1:1 conduction to the ventricles is a dangerous cardiac arrhythmia. Contemporary guidelines recommend atrioventricular nodal blocking agents should be co-administered with class 1C anti-arrhythmics, as prophylaxis against 1:1 flutter. No guidance is provided on the type or strength of atrioventricular nodal blockade required, and in practice, these agents are frequently prescribed at low dose, or even omitted, due to their side effect profile.
METHODS: A 62 year old Caucasian man with a history of paroxysmal atrial fibrillation treated with flecainide, presented with atrial flutter with 1:1 conduction to the ventricles and was cardioverted. Diltiazem was added to prevent this complication and he again presented with atrial flutter with 1:1 conduction to the ventricles, despite prophylaxis with coadministration of diltiazem.
CONCLUSIONS: This case report demonstrates failure of diltiazem to prevent 1:1 flutter in a patient chronically treated with flecainide for paroxysmal atrial fibrillation.

Photosensitivity is a condition of heightened skin sensitivity to sunlight or other forms of ultraviolet light. The case presented here highlights a rare occurrence of diltiazem-induced photosensitivity in an 87-year-old female patient with a history of atrial fibrillation and multiple comorbidities. The patient developed a distinctive erythematous rash limited to the sun-exposed area of the left side of her face during her hospital stay for respiratory failure and pneumonia. The localized distribution of the rash, along with its resolution upon reducing sun exposure, strongly suggested a photosensitivity reaction induced by diltiazem. Prompt discontinuation of the medication and transitioning to verapamil led to the resolution of the cutaneous manifestations. This case emphasizes the importance of recognizing and managing photosensitivity reactions as potential adverse effects of medications, such as diltiazem. Further research is needed to better understand the pathophysiology and risk factors associated with photosensitivity reactions to calcium channel blockers. Through this case report, we aim to contribute to the existing knowledge in this field and emphasize the significance of vigilance in clinical practice.

BACKGROUND: Gabapentin is commonly prescribed for the treatment of neuropathic pain, restless leg syndrome, and partial-onset seizures. Although the most frequent side effects of gabapentin are associated with the central nervous system, gabapentin can also affect the cardiovascular system. Case reports and observational studies have showed that gabapentin can be associated with increased risk of atrial fibrillation. However, all the evidence is concentrated in patients older than 65 years old with comorbidities that predispose them to the development of arrhythmias.
METHODS: We describe a case of an African American male in his 20s that presented to our chronic pain clinic with lumbar radiculitis and developed atrial fibrillation 4 days after being started on gabapentin. Laboratory workup did not show significant abnormalities, including normal complete blood count, comprehensive metabolic panel, toxicology screen, and thyroid-stimulating hormone. Transthoracic and transesophageal echocardiography showed a patent foramen ovale with right-to-left shunt. The patient was initially treated with diltiazem for heart rate control and apixaban. Direct current cardioversion with successful conversion to sinus rhythm was performed 24 hours after admission. The patient was then discharged on apixaban and diltiazem. Apixaban was changed to low-dose aspirin 1 month after discharge.
CONCLUSIONS: With rapidly increasing usage of gabapentin for approved and off-label indications, it is important to identify unintended adverse effects of this drug as they are considered safe alternatives to opioids. New-onset atrial fibrillation could be induced by gabapentin in young individuals.

Coronary artery spasm (CAS) is characterized by reversible diffuse or focal vasoconstriction, a phenomenon that plays an important role in the pathogenesis of ischemic heart disease. Fatal arrhythmias, such as ventricular tachycardia/fibrillation and complete atrioventricular block (AV-B), are very common in patients with CAS. Nondihydropyridine calcium channel blockers (CCBs) such as diltiazem were recommended as first-line medications for treating and preventing CAS episodes. However, its use remains controversial in CAS patients with AV-B as this type of CCB can also cause AV-B itself. Here, we present the use of diltiazem in a patient with complete AV-B caused by CAS. The patient\'s chest pain was rapidly relieved, and complete AV-B was promptly restored to sinus rhythm following the administration of intravenous diltiazem without any adverse effects. In this report, we highlight the useful and effective application of diltiazem for treating and preventing complete AV-B caused by CAS.

A thyroid storm is a rare endocrinological emergency caused by severe hyperthyroidism. Reducing circulating levels of free T3 in blood and beta-adrenergic inhibition are the basis of medical treatment for thyroid storms. Propranolol, due to its additional effect of preventing the peripheral conversion of dormant T4 to active form T3, is the chosen drug for blockade in hyperthyroidism and thyroid storm. We describe a rare clinical case of cardiovascular collapse following propranolol administration in a setting of thyroid storm. The patient presented with symptoms of dyspnea and palpitations and had an ejection fraction of 10%. He was started on a calcium channel blocker (diltiazem). Further investigations revealed that the patient also had a thyroid storm and was immediately shifted to methimazole and propranolol. However, following the administration of a beta-blocker, the patient developed circulatory failure as a result of cardiac arrest, necessitating the use of vasopressors and inotropes. This implores the need for further investigations and treatment regimens for cardiovascular conditions, especially atrial fibrillation arising in thyrotoxicosis, as there are no solid treatment guides in the literature to the best of our knowledge.

BACKGROUND: Atrial fibrillation is one of the most common arrhythmias. The main thrombotic complication of arterial fibrillation is ischemic stroke, but it can also cause acute renal infarction from embolization. The low incidence and nonspecific clinical manifestations of acute renal infarction make it difficult to diagnose, often leading to either delayed diagnosis or misdiagnosis. Due to its rarity, more efficient treatment guidelines are helpful for the management of acute renal infarction related to the thromboembolic complication of arterial fibrillation.
METHODS: We report a case of acute renal infarction due to underlying arterial fibrillation, where a novel interventional therapeutic method was used. A 66-year-old Chinese man with arterial fibrillation, not on anticoagulation due to the patient\'s preference, and coronary artery disease post-percutaneous coronary intervention to left anterior descending artery about 1 year ago, was currently on dual antiplatelet therapy. He suddenly developed intermittent and sharp left-sided abdominal pain and was found to have an acute left renal infarction on computed tomography scan. Angiogram showed acute occlusion of the left renal artery due to thromboembolism. For this patient, a combination method of local thrombus aspiration, angioplasty, and infusion of nitroglycerin and diltiazem were used, restoring blood flow to the left kidney. After recovery, the patient was discharged on aspirin, clopidogrel, and warfarin. At 6 months follow-up, there was no residual kidney dysfunction.
CONCLUSIONS: Acute renal infarction from thromboembolism is a rare but serious complication of arterial fibrillation. More efficient and different options for intervention methods will benefit the treatment of this disease. Here, we report a combination therapeutic method that has not been used in acute renal infarction associated with arterial fibrillation, and which restored renal perfusion and prevented long-term kidney injury.

Carbamazepine remains a first-line antiepileptic medication for the treatment of partial seizures. Despite its widespread use, carbamazepine has significant neurotoxicity and hypersensitivity reactions. We report a case of a patient post-kidney transplant who was on regular carbamazepine for childhood epilepsy and developed nystagmus, diplopia and a broad-base gait after receiving diltiazem. Understanding of the interaction between diltiazem and carbamazepine is necessary to prevent the neurotoxic effects.