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Electrocardiographic (EKG) cardiac abnormalities are common in patients with systemic lupus erythematosus (SLE), even those with a short disease duration, Canadian researchers have found. Severe abnormalities in this patient population are rare, however.

In their study, which appears in , nearly one-third of patients from a registry of participants with SLE were found to have EKG abnormalities. Some 779 adult patients participating in the Systemic Lupus International Collaborating Clinics (SLICC) Inception Registry formed the study population.

"Although patients were young (mean age 35.2 years) and had a short disease duration (mean 10.5 months), patients in the Systemic Lupus International Collaborating Clinics inception cohort already demonstrated evidence of cardiac abnormalities by EKG, including repolarization abnormalities that confer an increased risk for ventricular arrhythmias and sudden death," the authors wrote.

, from the University of Montreal Health Center in Quebec, and colleagues evaluated the prevalence of EKG abnormalities and clinical and laboratory variables among 779 adult SLE patients from eight countries participating in SLICC. Patients in the registry undergo a yearly research visit, during which disease activity, clinical features of SLE, risk factors, and laboratory data are collected. Most (80.4%) were women and 50.7% were white. The mean age at assessment was 35.2 years and the median lupus disease duration was 10.5 months. Nearly half (47.3%) had positive anti-Ro/SSA antibodies, of which 30.2% were anti-Ro/SSA 52 kd positive, 44.2% were anti-Ro/SSA 60 kd positive and 27.0% were both anti-Ro/SSA 52 and 60 kd positive. Thirty-one percent of the cohort was taking antihypertensive medication.

Nonspecific ST-T segment changes were found in 30.9% and a prolonged QTc interval (≥440 msec) in 15.3%. "In patients with rheumatic diseases, a 50-msec increase in the QTc interval has been associated with a doubling of the relative hazard for all-cause mortality, and some authors have suggested a connection between disease activity and arrhythmogenesis," the authors wrote. Severe repolarization abnormalities were rare; <1% of patients had a QTc interval ≥550 msec, they noted.

An increased QTd was found in 38.1%. In the general medical population, increased QTd is associated with arrhythmias and cardiac death and is an independent predictor of cardiovascular mortality.

Prominent QRS voltages, suggestive of left ventricular hypertrophy, occurred in 5.4%. Premature atrial and ventricular complexes occurred in 1.15% and 1.40%, respectively. Atrial fibrillation and other supraventricular arrhythmias were found in 0.13%.

Among the patients with ventricular conduction disturbances, incomplete bundle branch block, found in 2.68%, was the most frequent abnormality.

In multivariate models, antihypertensive drug therapy and increasing age were associated with QTc prolongation.

Wide confidence intervals "precluded definitive conclusions for other clinical and laboratory variables in our study, although numerical increases in the QTc interval were observed with anti-Ro/SSA antibody positivity," according to the investigators.

An increased QTc interval was observed in 12.4% of anti-Ro/SSA-negative patients compared with 17.0% who were anti-Ro/SSA 52 kd and/or 60 kd-positive. Anti-Ro/SSA positivity was not significantly correlated with QTc ≥440 msec. These results are "in accordance with previous studies involving a majority of SLE patients who did not demonstrate differences in QTc duration or QTd between anti-Ro/SSA-positive and anti- Ro/SSA-negative patients," they wrote.

The use of resting EKGs instead of 24-hour Holter monitoring is a potential limitation to the study, as is the lack of computer-generated QTc at some of the study centers.

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