Electrocardiographic Time to Intrinsicoid Deflection and Heart Failure: The Multi-Ethnic Study of Atherosclerosis

Abstract

Background: Time to intrinsicoid deflection (ID), the time from onset of the QRS complex to the peak of the R wave on the electrocardiogram, represents delayed ventricular activation and suggests that impaired myocardial function is present. It is unknown whether delayed time to ID is predictive of future heart failure (HF) events.

Hypothesis: Delayed time to ID is predictive of future HF events.

Methods: A total of 6394 participants (mean age, 62 ± 10 years; 54% women; 38% whites, 28% blacks, 22% Hispanics, 12% Chinese Americans) without clinically apparent cardiovascular disease or major ventricular conduction delay (QRS ≥120 ms) from the Multi-Ethnic Study of Atherosclerosis were included. Time to ID was automatically measured from baseline electrocardiograms (2000-2002) as the maximum value in leads V5 and V6 . Cox regression was used to compute hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between time to ID and HF.

Results: Over a median follow-up of 11.2 years, a total of 217 (3.4%) participants developed HF (incidence rate per 1000 person-years: 3.33, 95% CI: 2.91-3.80). In a multivariable Cox regression analysis adjusted for demographics, cardiovascular risk factors, and potential confounders, each 10-ms increase in maximum time to ID was associated with an increased risk for HF (HR: 1.42, 95% CI: 1.15-1.74). The results remained similar when stratified by age, sex, and race/ethnicity.

Conclusions: Delayed time to ID is able to identify individuals at risk for developing HF before major ventricular conduction delays (eg, bundle branch block) are evident.

Keywords: Electrocardiography ambulatory ECG; Epidemiology; Heart failure/cardiac transplantation/cardiomyopathy/myocarditis.

Figure 1

Multivariable risk of HF by time to ID. Each HR was computed with the median time to ID value of 36 ms as the reference and was adjusted for age, sex, race/ethnicity, education, income, heart rate, SBP, smoking, DM, BMI, cholesterol, HDL‐C, aspirin, statins, antihypertensive medications, and LVH. Dotted lines represent the 95% CI. Abbreviations: BMI, body mass index; CI, confidence interval; DM, diabetes mellitus; HDL‐C, high‐density lipoprotein cholesterol; HF, heart failure; HR, hazard ratio; ID, intrinsicoid deflection; LVH, left ventricular hypertrophy; ms, millisecond; SBP, systolic blood pressure.