Electrocardiographic Interatrial Block, P-Terminal Force, ST Level, and T-wave Inversion in General Population: Prevalence, Characteristics, and Prognostic Value

The resting electrocardiogram (ECG) is the most commonly performed cardiovascular diagnostic procedure in clinical practice. The ECG gives information about the electrical activity and the structure of the heart, as well as its pathological changes. Interatrial block (IAB), P-terminal force (PTF), ST depression, and T-wave inversion are abnormalities seen in ECG.

Cardiovascular diseases in general are the leading cause of mortality worldwide, and are related to major healthcare costs. Atrial fibrillation (AF) is the most common sustained arrhythmia in general population, increasing the risk of stroke, mortality, and dementia. Stroke and coronary heart disease (CHD) are both among the major causes of serious disability worldwide.

IAB and PTF are changes in the P wave reflecting underlying electromechanical and structural changes in the atria of the heart. They have been associated with increased risk of AF and ischemic stroke in general population. ST depression and T-wave inversion are markers of repolarization abnormalities of the ventricles in the heart. They are considered to reflect myocardial ischemia, although many other diseases can result in ST depression and T-wave inversion. In general population, ST depression and T-wave inversion in resting ECG have been associated with increased risk of CHD, as well as cardiovascular and total mortality. The location of ST depression and T-wave inversion in 12-lead ECG differs in different pathological conditions, and some studies have proposed that the prognostic significance of these repolarization abnormalities may depend on the location, also in general population. The aims of this study were to examine the prevalence and characteristics of these four ECG abnormalities, IAB, PTF, ST level, and T-wave inversion in general population and their prognostic significance for the above-mentioned cardiovascular diseases. Regarding repolarization abnormalities, the focus was on the prognostic value of the location of the changes.

This study was based on the prospective Health 2000 and Health 2011 Surveys carried out 2000–2001 and 2011–2012 in Finland. The Health 2000 population was designed to cover a nationally representative population sample of the Finnish population and consisted of 8,028 individuals aged 30+, of whom 79% (6,354 individuals) participated in the health examination, which included ECG recordings. All available participants of the Health 2000 Survey year 2011 were invited to take part in the Health 2011 Survey, and corresponding measurements were made. The follow-up data was collected from the national registries and the follow-up period lasted for over 15 years. The ECG parameters were obtained from computer analysis.

Prevalence of advanced IAB was 1% and of partial IAB around 10%. According to the study results, IAB and PTF are highly labile ECG abnormalities in general population as the reversion rate to normal varied 40.0% – 79.3% in serial ECG measurements taken 11 years apart. Traditional cardiovascular risk factors, including arterial hypertension, higher body mass index, and hypercholesterolemia were associated with incident IAB or progression/persistence of IAB. Partial and advanced IAB were associated with increased risk of AF in general population, and advanced IAB was associated with increased risk of stroke or transient ischemic attack, also independently of incident AF. PTF was not associated with increased risk of AF in our study population.

Lower lateral (leads I, aVL, V5 and V6) ST level as a continuous parameter was associated with increased mortality in both men and women. The adverse prognosis of lower lateral ST level in women seemed to be largely caused by left ventricular hypertrophy in the ECG. Nearly one-fifth (19.6%) of the participants had negative T waves in at least one lead group. Lateral T-wave inversion was associated with increased risk of mortality and CHD, and anterior T-wave inversion was associated with increased risk of CHD. Inferior repolarization abnormality (lower ST level or T-wave inversion) was a benign phenomenon in this study.

In conclusion, in this nationally representative population-based study partial and advanced IAB, lower lateral ST levels, and lateral and anterior T-wave inversions were associated with adverse prognosis. The P-wave abnormalities studied were labile findings in general population, hence the prognostic significance of diminution of P-wave abnormalities should be investigated in further studies. The location of repolarization abnormalities in resting 12-lead ECG had a major effect on prognostic significance, which should be taken into consideration in everyday clinical practice.