Association of QT interval with mortality by kidney function: results from the National Health and Nutrition Examination Survey (NHANES)

OBJECTIVE: Prolonged QT interval predisposes to ventricular arrhythmias and sudden cardiac death. However, the association between QT interval and mortality by the level of pre-existing kidney function has not been investigated. METHODS: We followed 6565 participants from the National Health and Nutrition Examination Survey III for a median of 13.3 years. Sample divided according to corrected QT (QTc) interval was as follows: normal (QTc <450 ms for men and <460 ms for women) or prolonged. It was further categorised as follows: (1) no chronic kidney disease (CKD), that is, albumin to creatinine ratio (ACR) <30 mg/g and estimated glomerular filtration rate (eGFR) > 60 mL/min/1.73 m(2); (2) CKD by eGFR only (eGFR <60 mL/min/1.73 m(2), ACR <30 mg/g); (3) CKD by ACR only (ACR >30 mg/g, eGFR >60 mL/min/1.73 m(2)) and (4) CKD by both. Cox proportional hazards models were used. RESULTS: CKD group had prolonged QTc than those without CKD (20.5%vs12.9%, p<0.0001). Both prolonged QTc and CKD are independently associated with increased risk of mortality. When combined, risk of mortality is higher in those with CKD by eGFR with prolonged QTc than normal QTc (HR 2.6 (1.7–3.9) and 3.1 (1.7–5.4) vs 1.4 (1.1–1.7) and 1.7 (1.3–2.1) for all-cause and CV mortality). There is no significant difference in risk in those with CKD by ACR when QTc is prolonged. There is significant improvement in risk prediction for all-cause and CV mortality when QTc is added to CKD beyond established CV risk factors (net reclassification index p<0.00001). CONCLUSION: A screening ECG in those with CKD may help in finer risk stratification and may be considered.