Hydroxychloroquine Use Is Not Associated With QTc Length in a Large Cohort of SLE and RA Patients

Background Hydroxychloroquine (HCQ) is a cornerstone therapy for systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). However, reports of its use and subsequent fatal arrhythmias in patients with Coronavirus disease 19 (COVID-19) have raised concern regarding its cardiovascular (CV) safety. Therefore, we examined the relationship between HCQ use and corrected QT (QTc) length in SLE and RA patients without clinical CV disease (CVD). Methods One SLE (n=352) and two RA cohorts (n=178) with electrocardiograms (ECGs) collected as part of study data were analyzed. RA cohort participants were recruited from tertiary referral centers with additional referrals from community rheumatologists, while SLE subjects originated from the Columbia University Lupus Cohort. All patients met American College of Rheumatology (ACR) classification criteria for SLE or RA, and lacked known CVD. The exposure of interest was HCQ use and main outcome measure was QTc length [continuous or categorical (≥440 ms and ≥500 ms)]. Results Of the combined SLE and RA cohorts (n=530), 70% were HCQ users and 44% had a QTc≥ 440 ms. The adjusted mean QTc length was comparable between HCQ users vs non-users (438 ms vs 437 ms). In multivariable logistic models, HCQ use was not a significant predictor of a QTc≥440 ms for the entire cohort (OR 0.77; 95% Cl 0.48–1.23; p=0.27). Importantly, a QTc≥500 ms was inversely associated with HCQ use and not associated with arrhythmias or deaths. A significant interaction was found between HCQ use and use of anti-psychotics. Ultimately, the use of HCQ combined with any QTc prolonging medication as a group was associated with a QTc length (434 ms; 95%CI 430,439) which was comparable to that of use of HCQ alone (433 ms; 95% Cl 429,437). Conclusion In a combined cohort of SLE and RA patients without clinical CVD, adjusted QTc length was comparable between HCQ and non-HCQ users, supporting its CV safety in patients with rheumatic diseases.

HCQ use and not associated with arrhythmias or deaths. A signi cant interaction was found between HCQ use and use of anti-psychotics. Ultimately, the use of HCQ combined with any QTc prolonging medication as a group was associated with a QTc length (434 ms; 95%CI 430, 439) which was comparable to that of use of HCQ alone (433 ms; 95% CI 429, 437).

Conclusion
In a combined cohort of SLE and RA patients without clinical CVD, adjusted QTc length was comparable between HCQ and non-HCQ users, supporting its CV safety in patients with rheumatic diseases. Background Hydroxychloroquine (HCQ) has long been a cornerstone therapy for systemic lupus erythematosus (SLE) and is commonly used as monotherapy or combined with other disease modifying anti-rheumatic drugs (DMARDs) for rheumatoid arthritis (RA). HCQ neutralizes acidic cytoplasmic components within the lysosome, leading to downstream alterations in antigen processing and inhibition of toll-like receptors (1,2). The observed cutaneous, retinal, and musculoskeletal toxicities are thought to arise from long term storage of its metabolite, 4-aminoquinolone, in these tissues (2). Loading [MathJax]/jax/output/CommonHTML/fonts/TeX/fontdata.js Acute cardiovascular (CV) toxicities from short term exposure of HCQ (and subsequent blocking of potassium channels within myocytes) manifest as QT interval prolongation and acute arrhythmic events (i.e. torsades de pointes) (3). With long term exposure, HCQ metabolites may also accumulate in the myocardium and result in a cardiomyopathy with concentric hypertrophy and conduction abnormalities (1, 3)(4). In fact, 33 of 42 histologically con rmed cases of HCQ induced cardiomyopathy originated from RA and SLE patients, who on average had been on treatment for 13 years (1). Moreover, 14 of those 42 cases progressed to third-degree atrioventricular block. However, there are no current guideline-based recommendations for CV screening in the setting of prolonged HCQ use.
Recent reports(5, 6) of possible associations between concurrent HCQ and azithromycin use and QTc prolongation in those receiving treatment for coronavirus disease 2019 (COVID19) associated pneumonia have raised further concerns for HCQ-associated cardiotoxicity. However, the wide spectrum of cardiotoxic effects of COVID19 itself (arrhythmias, myocarditis, microvascular injury, stress cardiomyopathy)(7) confound these observations. In observational (mostly retrospective studies) in rheumatic disease patients(8) , (9)(10)(11)(12) there were no differences in QTc prolongation in HCQ users vs nonusers, nor was there an association between QTc length and HCQ use. However, these studies did not consistently account for the use of other prolonging QTc medications. We therefore investigated associations between HCQ use and QTc length in an SLE and RA cohort without known CV disease (CVD), accounting for the use of various QTc prolonging medications.

Study Population
A total of 530 SLE and RA patients on whom HCQ use information was available were included in the study. billing code diagnosis, between January 2015 and December 2019. Inclusion criteria were: 1) ≥ 2 SLE ICD-9 /ICD-10 billing diagnoses con rmed by manual chart review (ful lling at least 4 ACR classi cation criteria (13)) or ≥ 1 SLE diagnosis PLUS ≥ 1 lupus nephritis proven on renal pathology report review; 2) at least 2 clinical visits on record; 3) ECG information available and 4) those residing locally in the boroughs of Manhattan and Bronx (to increase the likelihood of having patients with continuous and multidisciplinary care at CUIMC). Exclusion criteria were: 1) major ST-T changes/ bundle branch block on ECG; 2) prior CVD; and 3) missing documentation of medications. These criteria are summarized in Fig. 1.
RA Cohorts. Two established RA cohorts were studied: 1) ESCAPE-RA (Evaluation of Subclinical Cardiovascular Disease and Predictors of Events in Rheumatoid Arthritis) was a prospective study to Loading [MathJax]/jax/output/CommonHTML/fonts/TeX/fontdata.js investigate subclinical atherosclerosis in an RA cohort without clinical CV disease (14). Participants were recruited from the Johns Hopkins Arthritis Center and referrals from community rheumatologists between 2004-2008. Inclusion criteria were age > 45 for men and > 50 for women and ful llment of the 1987 ACR RA classi cation criteria (15). 2) RHYTHM-RA (RHeumatoid arthritis: studY of The Myocardium) is a cross-sectional study (subsequently extended to 4-6 year follow up) of myocardial phenotypes in RA patients without clinical CVD recruited from CUIMC and local rheumatology clinics between 2011-2020. Inclusion criteria included age ≥ 18 years old and ful llment of 2010 ACR RA classi cation criteria (13). In both RA cohorts, ECGs were obtained during the rst study visit.
Outcome Measure:

QTc length
The 12-lead ECGs (25 mm/s paper speed and 10 mm/mV amplitude) obtained at the rst/baseline study visits (RA) and regular clinical care (SLE) were interpreted by a board-certi ed cardiologist (PP) with specialization in electrophysiology blinded to diagnosis. The QT-interval was calculated and adjusted for the heart rate using Bazett's formula (QTc = QT/√RR)(16), and evaluated both as a continuous variable and as a binary variable using cutoffs of ≥ 440 and ≥ 500 ms. These cut-offs have been associated with an increased risk of clinical cardiac events including myocardial infarction, cardiac arrest, and stroke, as well as sudden cardiac death (17)(18)(19).
Clinical Covariates: SLE Patient characteristics and medications were collected from chart review. SLE disease duration was calculated as the duration in years from the date of physician diagnosis. Medication data were ascertained via clinician notes from the Electronic Medical Record (EMR). All medication data including HCQ use, were ascertained at the time of the ECG.
RA Cohorts (ESCAPE-RA/RHYTHM): Patient characteristics and medications were obtained through study patient questionnaires. RA disease duration was assessed by patient self-report of the date of diagnosis. Medication data was ascertained from medication bottles, and HCQ use was ascertained at the time of the ECG. Information regarding cumulative dosage or length of therapy for HCQ were not available for both SLE and RA cohorts. Hypertension was de ned as a systolic blood pressure (BP) of ≥ 140 mm Hg or diastolic BP of ≥ 90 mm Hg or use of antihypertensives at the time of the evaluation. Diabetes was de ned as a fasting serum glucose of ≥ 126 mg/dL or glycosylated hemoglobin (HbA1c) greater than 6.4% or antidiabetic medication use. QT-modifying medications were de ned as any medication included in the following categories: antidepressants, antipsychotics, antiarrhythmics, muscle relaxants, antimicrobials (antivirals/ macrolides/ uoroquinolones), tacrolimus, anticonvulsants, and antiemetics. Medication data (clearly noted as taking in EMR or study visits) was recorded in 76% of biologics, 92% of steroids, 77% of statin, 79% of aspirin, and 38% of any QTc prolonging medications. If QTc prolonging Loading [MathJax]/jax/output/CommonHTML/fonts/TeX/fontdata.js medication use (categorical variable) was not reported on the medication list, it was assumed that the patient was not on QTc prolonging medications.

Statistical Analysis
Variables were summarized and compared using Student's t-tests if normally distributed, Wilcoxon ranksum tests for non-normally distributed variables, or χ 2 or Fisher's exact tests for categorical variables. Linear and logistic regression were used to model the associations of clinical and laboratory covariates with QTc length (continuous), and with QTc ≥ 440 ms and QTc ≥ 500 ms, respectively. Multivariable models were constructed by including any covariate signi cantly (p < 0.25) associated with the primary outcomes (QTc length, QTc ≥ 440 ms, QTc ≥ 500 ms) in univariate regression models. All analyses were performed using Stata version 15 (StataCorp, College Station, TX).
Multiple chained imputations were used to impute medication use for those with missing data for medications associated with QTc length (continuous) and QTc ≥ 440 and ≥ 500.

Results
Patient Population: Patient disease characteristics, medications, and CV risk factors of combined SLE and RA cohorts are summarized in Table 1. Of the 530 study patients included in the study, 371 (70%) reported HCQ use at the time of ECG assessment. In the combined SLE/RA cohort, the mean QTc was 437 ± 29ms. The mean QTc measurements for the SLE and RA cohorts were 432 ± 23ms and 444 ± 33ms, respectively. Forty-four % of the combined group had a QTc ≥ 440 ms and 7% had a QTc ≥ 500 ms. On average, the cohort was middle aged (51 ± 14 years), predominantly female (83%) and non-white race (combined Black, Hispanic, and other race: 62%). The median disease duration was 12 years, and 65% were on glucocorticoids. Hypertension was reported in 46%, while 39% were on other QTc prolonging Loading [MathJax]/jax/output/CommonHTML/fonts/TeX/fontdata.js medications. On strati cation by HCQ use, HCQ users were signi cantly younger and used more glucocorticoids and statins (p < 0.005) than non-HCQ users. No arrhythmic episodes or associated deaths were reported during the study periods for the RA or the SLE cohorts (2011-2020 and 2015-2019, respectively). Loading [MathJax]/jax/output/CommonHTML/fonts/TeX/fontdata.js                      In multivariable models, age, current prednisone use, and current smoking were signi cantly associated with QTc length (Table 2). Current prednisone use and current aspirin use were signi cantly associated with QTc440 ms ( Table 3). The only signi cant predictor of QTc500 ms was current use of tacrolimus (Table 4).

Subgroup Analyses SLE only cohort
In the SLE cohort, HCQ use was not a signi cant predictor of QTc length (Table 7) or a QTc440 ms (Table 8). However, of the 11 SLE patients with QTc500 ms, 9/11 were reported to be on HCQ. Given the small sample size, statistically signi cant differences could not be ascertained between the HCQ groups with a QTc 500ms, yet no arrhythmias or associated deaths were reported, as per retrospective chart review over 4 years. In multivariable analyses, elevated CRP level (≥ 10.0 mg/L) was signi cantly associated with QTc length, and diabetes and use of any QTc prolonging medications were signi cantly associated with QTc440 ms (                 In the RA cohorts analyzed separately, HCQ use was not a signi cant predictor of QTc length (Table 10), nor of a QTc 440 (p = 0.79) or 500 ms (p = 0.75) (Tables 11 and 12). Notably, signi cant predictors of prolonged QTc500 ms included age, current smoking, and diabetes (Table 12). Adjusted QTc was comparable in HCQ vs non-HCQ users (449 ms vs 443 ms, respectively) (Fig. 4). Loading [MathJax]/jax/output/CommonHTML/fonts/TeX/fontdata.js        In the combined RA + SLE cohort, a signi cant interaction was found between HCQ use and use of antipsychotics (Table 13a), with QTc length being longer in those on both vs only HCQ (439 ms vs 432 ms; Fig. 5). Overall, QTc length was comparable in those on HCQ + any QTc prolonging medications vs only HCQ (434 ms vs 433 ms; Fig. 6). When strati ed by RA vs SLE cohort, no signi cant interactions were found between HCQ use and use of any QTc medications (Table 13b-13c).  QTc length as an outcome remains of paramount interest, since in the general population and in selected subpopulations (i.e. the elderly, patients with coronary artery disease, and the critically ill), prolonged QTc length (de ned in those studies as > 450 ms in men and > 470 ms in women) independently predicts sudden cardiac death (17,18). In fact, even moderate QTc prolongation between 420-440 ms has been associated with all-cause mortality (19). In a retrospective cohort study of RA patients, idiopathic QTc prolongation (20) was associated with an almost 30% increase in all-cause mortality (HR: 1.28; 95% CI: 0.91-1.81, p = 0.16). Furthermore, in a prospective cohort of RA patients, a 50-ms increase in QTc interval was independently associated with a two-fold risk of mortality (HR = 2.18, 95% CI 1.09, 4.35), but this association was lost when CRP was added to the nal model (HR = 1.73; 95% CI 0.83, 3.62; p = 0.143)(8).
In our study, prednisone use was associated with a lower QTc length in the combined RA + SLE cohort, in addition to being a negative predictor of QTc ≥ 440 ms, further signaling a possible interplay between in ammation and arrhythmogenic potential.
HCQ-associated QTc prolongation and subsequent arrhythmia development received considerable attention during its widespread use in COVID-19 patients. In an uncontrolled study of COVID-19 patients receiving HCQ alone or HCQ and azithromycin for associated pneumonia(6), baseline to treatment change in QTc was higher in the HCQ + azithromycin group vs HCQ alone. It is also worthwhile noting that in the prior study, up to 19% of those receiving HCQ alone had a QTc > 500 ms (and 21% in combination group) and 8% had a clinically signi cant increase > 60 ms, with one episode of torsades de pointes reported. However, independent effects of COVID-19 infection on the cardiac conduction system (7)  to treatment in the HCQ and azithromycin group vs HCQ alone (17 ± 39 ms vs 0.5 ± 40 ms; p = 0.07). More concerning, up to 12% of total patients in this study (receiving HCQ alone, azithromycin alone, or both), had critical QTc prolongation (de ned as maximum QTc ≥ 500 ms (if QRS < 120 ms) or QTc ≥ 550 ms (if QRS ≥ 120 ms) and QTc increase of ≥ 60 ms), however no torsades de pointes was documented. The results of a more recent randomized controlled trial (22) were more reassuring in that, in 1,561 COVID patients randomized to the HCQ arm and loaded with high doses of HCQ (800 mg x 2 doses followed by 400 mg every 12 hours for 9 days or until discharge), there were no signi cant differences in terms of frequency of arrhythmias compared to the usual care group.
As for rheumatologic patients, SLE patients treated with high cumulative doses (700g-1300g) of antimalarials from several months to decades, demonstrated bundle branch block and third degree AV block (with some leading to Torsades de Pointes)(23-26). However, interpretation from these case reports is limited due to absence of controls. It is also important to note that current trends in HCQ dosing have become more conservative due to heightened awareness of retinal toxicity. More recently, Lane et al (27) reported no increased risk of cardiac arrhythmias (calibrated HR 0.90; 95% CI 0.78-1.03; p < 0.01) in HCQ users (400 mg/day for 30 days) vs sulfasalazine users in a retrospective review of 14 multinational databases of RA patients. Liu et al(28) reported a lower risk of CV disease including sudden cardiac arrest/death in HCQ/chloroquine (CQ) users vs non-users (RR 0.72; 95% CI 0.56-0.94; p = 0.013) in a meta-analysis of various rheumatologic patients. Various cardioprotective (thromboprotective and cholesterol reducing) effects of HCQ/CQ(29, 30) may partially explain this nding but the absence of clinical trial data and CV/metabolic parameters limit interpretation. In another prospective study(31) of RA patients, incidence of long QT syndrome or arrhythmia related hospitalizations were comparable between HCQ use vs non-HCQ disease modifying anti-rheumatic drug (DMARD) use.
Speci cally, the lack of association of HCQ use with overall QTc length in our results is consistent with prior publications in RA and SLE patients (8)(9)(10)(11)20). The main strength of our study is its sample size as it represents one of the largest multiethnic studies inclusive of both SLE and RA patients. Importantly, we accounted for the concurrent use of a wide variety of QTc prolonging or arrhythmogenic medications, which was not consistently done in previous literature. Although SLE data were obtained retrospectively via ICD 9/10 codes on EMR review, we restricted analyses to SLE patients who demonstrated consistent care at our institution (≥ 2 visits). For both the SLE and RA cohorts, QTc length was calculated by standardized Bazett's formula and con rmed by a blinded, trained cardiac electrophysiologist (PP). The main limitations of our study include the lack of data on HCQ adherence (i.e. via patient report, and/or metabolite levels), as well as cumulative dosage or length of therapy. In addition, we did not obtain or analyze pre-HCQ ECGs (determined only at the time of HCQ use for both SLE and RA cohorts) and therefore, cannot make conclusions about pre and post exposure change in QTc length. Finally, although we excluded patients with clinical CVD and our ndings may not directly apply to those patients, our patients likely had underlying, subclinical CVD given the prevalence of associated risk factors (hypertension, diabetes). In a combined large multiethnic cohort of RA and SLE patients, QTc length did not signi cantly differ in HCQ users compared with non-HCQ users, nor was it associated with a QTc ≥ 440 ms, even while adjusting for potential confounders. There was a notable statistical interaction between the use of HCQ and use of antipsychotics in the combined RA and SLE cohort. Our data suggests that HCQ does not increase the arrhythmogenic risk for patients with rheumatologic conditions.