(153) Reviving Rhythms: The Modern Role of Quinidine in the Cardiac and Cardiothoracic ICU

Introduction: The use of quinidine, a Vaughn-William class Ia antiarrhythmic, has decreased over time. However, there is still a need for effective antiarrhythmic drugs (AADs) to suppress ventricular arrhythmias (VAs), in patient's intolerant or unresponsive to other AADs. Its minimal negative inotropic effects make it favorable in critically ill patients with ventricular dysfunction.

Methods: This retrospective cohort study included adult patients that received quinidine for ≥ 24 hours, for any sustained VA in the cardiac or cardiothoracic intensive care unit (CICU/CTICU) from 1/1/2018 to 6/31/2024.  Data collected included the type of VA, AAD prior to quinidine, echocardiographic data, and quinidine characteristics. The primary outcome was the cumulative incidence of escalation in any VA treatment, up to 3 days post quinidine initiation. This was defined as an increase in shocks in those with an ICD, or any escalation in AAD, addition of mechanical circulatory support (MCS) or other VA treatments such as stellate ganglion block or ablation. Adverse events and therapeutic drug monitoring (TDM) were collected up to quinidine discontinuation or until hospital discharge or death.

Results: Our cohort included 38 patients, 83% of whom received quinidine for refractory VA due to ischemic cardiomyopathy in 61% of the cohort. The median quinidine dose was 800 mg/day (IQR 600, 900) for a median duration of 7.5 days (IQR 6, 12). Prior to quinidine initiation, the most common AADs included amiodarone (84%) followed by lidocaine (53%), mexiletine (21%), procainamide (11%), and beta blockers (8%). The cumulative escalation of any VA treatment occurred in 9 (24%) patients. Of the 20 patients with preexisting ICDs, quinidine reduced the mean VA instance by 4.6 events. Nausea and vomiting were seen in 16% of patients and one patient discontinued quinidine due to QT prolongation. The incidence of TDM was 16% for the total cohort, with no quinidine level > 5mcg/mL. Total mortality was 16% for the cohort.

Conclusions: Quinidine remains relevant in modern CICU/CTICUs for patients failing conventional AADs or in those who are not hemodynamically stable for cardiac ablation, in whom the immediate goal is to achieve arrhythmia suppression as a bridge to destination MCS or transplant.