Prevalence of potential noninvasive arrhythmia risk predictors in healthy, middle-aged persons

Abstract

Background: To date, prevalence and clinical significance of noninvasive arrhythmia risk predictors in apparently healthy, middle-aged persons are largely unknown.

Methods: A total of 110 apparently healthy persons 20-75 years old were enrolled in this prospective observational monocenter study and followed up for 32 +/- 15 months. Baseline investigations included symptom-limited bicycle ergometry, echocardiography, time-domain analysis, and spectral turbulence analysis of the signal-averaged electrocardiogram (ECG), ventricular arrhythmias, and heart rate variability on 24-hour Holter ECG, baroreflex sensitivity, and t-wave alternans in all persons.

Results: The prevalence of an abnormal signal-averaged ECG was 1% for spectral turbulence analysis and varied between 1% and 37% for time-domain analysis depending upon the definition used for an abnormal time-domain analysis. A reduced heart rate variability defined as a standard deviation of normal-to-normal intervals < or =105 ms, <100 ms and <70 ms was found in 12%, 9%, and 1% of persons. A baroreflex sensitivity <6 ms/mmHg and <3 ms/mmHg was present in 15% and 2% of persons. Microvolt t-wave alternans was found to be positive in 5%, negative in 88%, and indeterminate in 7% of persons, respectively. During the 32 +/- 15 months follow-up, no arrhythmic events and no cardiovascular mortality were observed in this population.

Conclusions: Abnormal findings of noninvasive arrhythmia risk stratification can be found in 1-37% of healthy, middle-aged persons when previously reported cut-off values are used.

Figure 1

Normal (A) and abnormal time‐domain analysis (B) of the signal‐averaged electrocardiogram in an apparently healthy person without arrhythmic events during follow‐up.

Figure 2

Distribution of the standard deviation of normal‐to‐normal R‐R intervals (SDNN) (A), and baroreflex sensitivity (B) in 110 healthy, middle‐aged persons.

Figure 3

Positive t‐wave alternans analysis in an apparently healthy person without arrhythmic events during follow‐up. Alternans analysis during symptom‐limited bicycle ergometry for leads VM, X, Y, Z, and V₄ is shown on the left side. The t‐wave spectrum during exercise testing with a distinct peak at a 0.5 cycle/beat frequency is shown on the right side. The dark shaded areas with black bars for each lead also indicate positive microvolt t‐wave alternans during exercise in this person. HR, heart rate trend; % bad, percentage of beats more than 10% premature; noise, mean noise in lead VM; RPM, bicycle ergometer pedaling rate; resp, respiratory frequency; HR delta, the difference between the highest and lowest instantaneous heart rates for a 128‐consecutive beat interval; R‐R alternans, the amplitude of R‐R interval alternans.