Thoracic versus nonthoracic MR imaging for patients with an MR nonconditional cardiac implantable electronic device.

BACKGROUND: Observational studies have explored the safety of magnetic resonance (MR) scanning of patients with cardiac implantable electronic devices (CIEDs) that are not Food and Drug Administration approved for MR scanning ("nonconditional"). However, concern has been raised that MR scanning that includes the thoracic region may pose a higher risk. This study examines the safety of MR scanning of thoracic versus nonthoracic regions of patients with CIEDs. METHODS: Patients underwent MR scanning utilizing an institutional protocol. CIED variables examined included sensing value, pacing capture threshold, lead impedance, and battery voltage. Regression analysis of the CIED variable differences (pre- to immediately post-MR and pre-MR to long-term follow-up) was performed to determine if CIED variable differences were dependent on region scanned (thoracic vs nonthoracic), time from CIED implant to MR scanning, or CIED type (pacemaker vs implantable cardioverter defibrillator). RESULTS: 238 patients (38% female, age 65 ± 15 years) underwent 339 MR scans, including 99 MR scans of the thoracic region. CIED variable differences to immediately post-MR or to long-term follow-up were not significantly different from zero (P > 0.05) and there was no dependence upon region scanned (thoracic vs nonthoracic), time from CIED implant to MR scan, or CIED type. One power-on reset occurred in a patient that underwent a cardiac MR and the CIED was successfully reprogrammed. There were no clinical adverse effects. CONCLUSIONS: CIED variable differences following MR scan were not dependent on the region scanned (thoracic vs nonthoracic) and there were no clinical adverse effects in this prospective cohort.

Associations of Prolonged QTc in Sickle Cell Disease.

Sudden death is a leading cause of mortality in sickle cell disease, implicating ventricular tachyarrhythmias. Prolonged QTc on an electrocardiogram (ECG), commonly seen with myocardial ischemia, is a known risk for polymorphic ventricular tachycardia (VT). We hypothesized that prolonged QTc is associated with mortality in sickle cell disease. ECG were analyzed from a cohort of 224 sickle patients (University of Illinois at Chicago, UIC) along with available laboratory, and echocardiographic findings, and from another cohort of 38 patients (University of Chicago, UC) for which cardiac MRI and free heme values were also measured. In the UIC cohort, QTc was potentially related to mortality with a hazard ratio (HR) of 1.22 per 10ms, (P = 0.015), and a HR = 3.19 (P = 0.045) for a QTc>480ms. In multivariate analyses, QTc remained significantly associated with survival after adjusting for inpatient ECG status (HR 1.26 per 10ms interval, P = 0.010) and genotype status [HR 1.21 per 10ms interval, P = 0.037). QTc trended toward association with mortality after adjusting for both LDH and hydroxyurea use (HR 1.21 per 10ms interval, P = 0.062) but was not significant after adjusting for TRV. In univariate analyses, QTc was related to markers of hemolysis including AST (P = 0.031), hemoglobin (P = 0.014), TR velocity (P = 0.036), higher in inpatients (P<0.001) and those with an SS compared to SC genotype (P<0.001) in the UIC cohort as well as to free heme in the UC cohort (P = 0.002). These findings support a relationship of prolonged QTc with hemolysis and potentially mortality in sickle cell disease.