QT Interval Dynamics and Cardiovascular Outcomes: A Cohort Study in an Integrated Health Care Delivery System

Background Long QT has been associated with ventricular dysrhythmias, cardiovascular disease (CVD) mortality, and sudden cardiac death. However, no studies to date have investigated the dynamics of within‐person QT change over time in relation to risk of incident CVD and all‐cause mortality in a real‐world setting. Methods and Results A cohort study among members of an integrated health care delivery system in Northern California including 61 455 people (mean age, 62 years; 60% women, 42% non‐White) with 3 or more ECGs (baseline in 2005–2009; mean±SD follow‐up time, 7.6±2.6 years). In fully adjusted models, tertile 3 versus tertile 1 of average QT corrected (using the Fridericia correction) was associated with cardiac arrest (hazard ratio [HR], 1.66), heart failure (HR, 1.62), ventricular dysrhythmias (HR, 1.56), all CVD (HR, 1.31), ischemic heart disease (HR, 1.28), total stroke (HR, 1.18), and all‐cause mortality (HR, 1.24). Tertile 3 versus tertile 2 of the QT corrected linear slope was associated with cardiac arrest (HR, 1.22), ventricular dysrhythmias (HR, 1.12), and all‐cause mortality (HR, 1.09). Tertile 3 versus tertile 1 of the QT corrected root mean squared error was associated with ventricular dysrhythmias (HR, 1.34), heart failure (HR, 1.28), all‐cause mortality (HR, 1.20), all CVD (HR, 1.14), total stroke (HR, 1.08), and ischemic heart disease (HR, 1.07). Conclusions Our results demonstrate improved predictive ability for CVD outcomes using longitudinal information from serial ECGs. Long‐term average QT corrected was more strongly associated with CVD outcomes than the linear slope or the root mean squared error. This new evidence is clinically relevant because ECGs are frequently used, noninvasive, and inexpensive.

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Specialized Heart Failure Centers-A Success or an Indicator of the Failure of Our Health Care Delivery System

Clinical Cardiology ◽

10.1002/clc.4960231204 ◽

2000 ◽

Vol 23 (12) ◽

pp. 881-882 ◽

Cited By ~ 3

Author(s):

Bertram Pitt ◽

John M. Nicklas

Keyword(s):

Heart Failure ◽

Health Care ◽

Delivery System ◽

Health Care Delivery ◽

Care Delivery ◽

Health Care Delivery System

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Abstract P107: Association of Longitudinal Change and Fluctuation in QT Interval with Cardiovascular Outcomes: A Cohort Study in a Managed Care Setting

Circulation ◽

10.1161/circ.125.suppl_10.ap107 ◽

2012 ◽

Vol 125 (suppl_10) ◽

Author(s):

Carlos Iribarren ◽

Alfred D Round ◽

Liisa L Lyon ◽

Joseph F Terdiman ◽

Jonathan G Zaroff ◽

...

Keyword(s):

Heart Failure ◽

Cardiac Arrest ◽

Managed Care ◽

Qt Interval ◽

Care Setting ◽

Coronary Syndrome ◽

All Cause Mortality ◽

Race Ethnicity ◽

Linear Slope ◽

Over Time

Purpose. Both long and short QT intervals are associated with life-threatening cardiac arrhythmias and adverse cardiovascular (CV) events, but prior studies have typically relied on a single baseline measure of the QT interval. We examined the prospective association of within-person change and fluctuation in QT length over time with subsequent CV outcomes and all-cause mortality in a managed care setting. Methods. We assembled a cohort of 187,901 Northern California Kaiser Permanente Medical Care Program (KPMCP) members who underwent three or more standard 12-lead ECGs as part of regular care between 1995 and 2008. Cohort-specific log-linear models stratified by gender, age and race/ethnicity were used to correct raw QT measurements for heart rate (QTc). Non-fatal and fatal CV outcomes and all-cause mortality were identified between the last ECG and right censoring event (CV event, death, termination of health plan membership or 12/31/2009; the median [SD] follow-up time was 4.1 [3.7] years). Cox regression models adjusting for age, gender, race/ethnicity, hypertension, diabetes, hyperlipidemia, smoking status and average QTc were used to simultaneously generate hazard ratios and 95% CI for tertiles 1 and 3 (versus tertile 2) of the linear slope of QTc (change in ms per year) and for tertiles 2 and 3 (versus tertile 1) of the root mean square error of QTc (RMSE, variability about the linear slope in ms). Results. The mean QTc slope and RMSE were +2.2 ms/year and 15.3 ms in men and +1.4 ms/year and 14.3 ms in women, respectively. In fully-adjusted models, the sex-specific tertile 3 of the QTc slope was associated with increased hazard of acute coronary syndrome (Number of events; Hazard Ratio; 95% Confidence Interval) (17,920; 1.34; 1.30-1.39), ischemic stroke (11,716; 1.30; 1.25-1.36), heart failure (42,909; 1.47; 1.44-1.51), cardiac arrest (4,700; 1.67; 1.55-1.79) and all-cause mortality (72,392; 1.43;1.40-1.45). In turn, the sex-specific tertile 3 of the RMSE was associated with increased hazard of heart failure (1.34;1.31-1.37), cardiac arrest (1.19;1,11-1.28) and all-cause mortality (1.06;1.04-1.08). Conclusions. In an insured population that underwent multiple ECGs, both linear increase and fluctuation of QTc over time were significantly and independently associated with adverse CV outcomes. Whether these associations are causal or represent confounding effects of medications warrant further research.

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