Prevalence and predictors of acquired long QT syndrome in the ER department

Introduction

Long QT syndrome (LQTS) is a rare heterogeneous syndrome that may be congenital or acquired, the latter being more common. Its real-world prevalence remains to be determined. We aimed to determine the prevalence of this syndrome in patients admitted to the emergency room (ER) and characterize the subset of patients with severely prolonged QT.

Methods

A retrospective analysis of ECG of all consecutively admitted patients in the ER of a tertiary hospital between the 28th of January and the 17th of March 2020 was made. All patients with Bazzett corrected QT interval greater than 470ms in men and 480ms in women were included. Repeated ECGs or with bad electrocardiographic quality, congenital LQTS, atrial fibrillation and pacemaker rhythm were excluded. Clinical data with a special focus on QT prolonging drugs and clinical factors were recorded. Statistical comparison was made between the groups with and without QT interval greater than 500ms.

Results

A total of 6280 ECGs of 5056 patients were analysed. After evaluation, 390 ECGs from 387 different patients were considered. Prevalence of LQTS at admission was 7.95%. Patients were more commonly men (53.1%) with an average age of 73.6±14.7 years old and mean QTc interval of 502.14±32.2ms. Only 20% of the patients were symptomatic, with the most common form of presentation being syncope (50%). No ventricular arrhythmias were recorded.

Regarding patients with a QT interval greater than 500ms, these were more frequently female (59.9% vs 37.2%, p<0.001), were more frequently on QT prolonging drugs (77.8% vs 67.3%; p=0.002). Presence of clinical risk factors was not a risk factor per se (p=0.811) but a greater number of risk factors was linked to more severely prolonged QT (p=0.040). The main contributing factor was intake of antibiotics (odds ratio (OR) 3.497; CI 95% 1.074–11.321; p=0.038) followed by female gender (OR 2.518; CI 95% 1.668–3.800; p<0.001) and use of antipsychotics (OR 1.960; CI 95% 1.159–3.316; p=0.012).

Conclusions

Acquired LQTS is particularly prevalent in the ER setting. The complex interaction of clinical factors and drug iatrogenesis and the unpredictability of its manifestations render its management and recognition difficult but essential. Female patients on antibiotics and antipsychotics are at particularly high risk. Efforts must be made in order to avoid, detect and treat acquired LQTS as early as possible.

Funding Acknowledgement

Type of funding sources: None.

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Response to treatment with interferon-alfa in patients with chronic hepatitis C and high titers of -M2, -M4 and -M8 antimitochondrial antibodies

The prevalence of antimitochondrial antibodies (AMA) in chronic hepatitis C is 2%; titers of AMA are usually low (< 1:40). The prevalence decreases to 0.5% when the results are verified by determination of the M2 subtype (anti-M2, ELISA). In patients in whom both hepatitis C virus (HCV) and AMA are present, the therapeutic decision to give interferon-alfa is complicated, because AMA may be 'real', and if it reflects primary biliary cirrhosis, cholestasis can be triggered or exacerbated. This does not occur when AMA positivity results from induction by hepatotropic C virus; however, this is rarely the case when AMA titers are high (> 1:160).

OBJECTIVE

to undertake a preliminary analysis of the submitochondrial profile of AMA in three patients with chronic hepatitis C and positive AMA titers (> 1:160).

METHODS

we determined antibodies to submitochondrial particles (subtypes) -M2, -M4 and -M8 by ELISA, complement binding (CB) and western immunoblotting with Immunoblot-M2 or WIB-M2 (immunoreactive bands).

RESULTS

two patients were positive for mitochondrial subtypes by ELISA (IgG/IgM subclass) and CB (ELISA M2 470/365 in patient 1 and 600/1370 in patient 2; M4 490/1200 in patient 2. CB M2 1:128, M4 1:64, M8 1:64 in patient 1, M2 1:128 in patient 2). Immunoreactive epitopes (bands) were detected with WIB-M2 for 70, 56, 51, 45 and 36-kDa molecules. Interferon-alfa treatment was unsuccessful, with biochemical exacerbation of cholestasis. In contrast, the patient with no submitochondrial particles according to ELISA, CB and WIB-M2 results responded favorable to this drug.

CONCLUSION

these preliminary results suggest that analyses to detect antibodies to submitochondrial particles (-M2, -M4 and -M8 subtypes) and -M2-immunoreactive epitopes in patients with chronic hepatitis C and AMA titers > 1:160 facilitates the diagnosis of primary biliary cirrhosis, and establishes a contraindication for treatment with interferon-alfa despite the presence of HCV infection.

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Esophageal transection and paraesophagogastric devascularization performed as an emergency measure for uncontrolled variceal bleeding

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