The frontal QRS-T angle (QTA) is widely available on routine 12-lead electrocardiograms (ECGs), but its practical significance is little recognised. An abnormally wide QTA is known to be a prognostic predictor of cardiovascular events. It has even been considered as a stronger prognostic predictor than the commonly used ECG parameters including ST-T abnormality and QT prolongation. The aim of this study was to investigate the influence of ageing on the QTA in a low-risk population where there were no obvious ECG abnormalities. Having analysed 437 consecutive patients, we found a positive correlation between age and QTA, but no age difference in heart rate, QRS duration, QT interval and P-wave axis. As hypertension was more prevalent in older patients, we compared patients with hypertension to those without and found no significant difference in QTA. Therefore, ageing alone is a significant contributory factor to the widening of QRS-T angle. Further study to confirm QTA as a prognostic predictor for all-cause mortality, independent of age itself and in the absence of ECG abnormalities, in an older population would be significant.
Introduction
The significance of the frontal QRS-T angle (QTA), the difference between the QRS-axis and T-axis, has not been widely recognised in clinical practice, though it is widely available on 12-lead ECGs recorded by a modern electrocardiograph.1,2 An abnormally wide QTA represents an abnormality of ventricular depolarisation or repolarisation, and is known to be an independent predictor of cardiovascular mortality secondary to ischaemic events, sudden death, death from arrhythmia, increased incidence of congestive heart failure, as well as all-cause mortality.2-5 It has even been considered as a stronger predictor of poor prognosis than other commonly used ECG parameters, including ST depression, T-wave inversion and QT prolongation.5 However, whether QTA widens with ageing in people with an apparently normal ECG remains uncertain. We, therefore, aimed to investigate the influence of ageing on the QTA in the frontal plane of 12-lead ECG in a low-risk population.
Method
We recruited 437 consecutive patients retrospectively from our GP Open Access ECG services from March to May 2015. Patient age ranged from 18 to 88 years and all patients had a normal resting ECG determined digitally by the electrocardiograph used (Philips PageWriter TC70). Patients taking beta blockers or with a history of coronary artery disease were excluded from the study. We investigated the relationship between QTA and age by linear regression analysis. We compared risk factors for cardiovascular disease and ECG measurements using Chi-square analysis or student t-test between those aged below 65 years and those aged 65 years and above.
Results
There was a positive correlation between age and QTA in both actual (0.36, p<0.001) and absolute (0.12, p<0.01) values. The only significant difference in patient characteristics was, among risk factors for cardiovascular disease, a higher incidence of hypertension in those aged 65 years and above than those who were under 65 years (p<0.05). On ECG, heart rate, QRS duration, QT-interval and P-wave axis did not show any age difference, but the PR interval was longer, QRS axis closer to zero, T-wave axis farther away from zero and the QTA greater in patients aged 65 and above than in those who were younger than 65 years (table 1).
Table 1. Patient information and electrocardiogram (ECG) measurements
| Measurements | Group I Age <65 years n=375 |
Group II Age ≥65 years n=62 |
p value |
|---|---|---|---|
| Sex (M/F), n | 177/198 | 27/38 | NS |
| Hypertension, n | 93 | 29 | <0.01 |
| Diabetes, n | 15 | 6 | NS |
| Smoking, n | 10 | 4 | NS |
| Heart rate (bpm) | 72.7 ± 12.7 | 72.9 ± 11.8 | NS |
| PR interval (ms) | 151.9 ± 20.8 | 161.3 ± 22.8 | <0.01 |
| QRS duration (ms) | 90.5 ± 16.8 | 89.4 ± 7.5 | NS |
| QT interval (ms) | 385.1 ± 45.7 | 393 ± 23.4 | NS |
| P-axis | 49.6 ± 22.8 | 42.3 ± 23.9 | NS |
| QRS-axis | 40.2 ± 30.0 | 25.7 ± 31.8 | <0.001 |
| T-axis | 36.0 ± 22.9 | 48.4 ± 24.5 | <0.001 |
| QRS-T angle | |||
| Actual value | 4.1 ± 32.4 | 22.7 ± 36.8 | <0.001 |
| Absolute value | 25.0 ± 21.0 | 34.0 ± 26.4 | <0.001 |
| Presented as mean ± standard deviation, unless otherwise specified. Key: NS = not significant |
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As hypertension was more prevalent in the older group, we compared patients with hypertension to those without and found no significant difference in QTA (absolute 29.5 ± 26.0 vs. 26 ± 20.6, p>0.05) between the two groups, hence hypertension did not affect the QTA in this study population.
The increase in QTA with ageing in this population was the combination of anticlockwise shift of the QRS axis and clockwise shift of the T-wave axis. The observation, by design, did not include any patients with an abnormally wide QTA, nor was it indented to evaluate the ageing effects in the same subjects, which would be a worthwhile longitudinal study. The main limitation of this study was of its small scale in both sample size and observation parameter.
Conclusion
We conclude that ageing is a significant contributory factor to the widening of QRS-T angle in a population who have no apparent ECG abnormalities. Longitudinal observations would be needed to identify whether QTA can serve as a prognostic predictor, independent of age, for all-cause mortality in an older population with a normal baseline ECG.
Key messages
- QRS-T angle is a prognostic factor for cardiovascular events and all-cause mortality. It is widely available but is not commonly used
- The greater the age the wider the QRS-T angle
- QRS-T angle may serve as a prognostic predictor for all-cause mortality, even in the absence of conventional electrocardiogram (ECG) abnormalities in the older population
Conflicts of interest
None declared.
Funding
None.
Study approval and consent
The data analysis was carried out on our departmental database retrospectively as part of a service evaluation initially. Information related to patients’ identity was not included. We did not seek consent of patients or ethics committee approval of the project as we believe this complies with the NHS Health Research Authority guidance.
References
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2. Oehler A, Feldman T, Henrikson C, Tereshchenko L. QRS-T angle: a review. Ann Noninvasive Electrocardiol 2014;19:534–42. https://doi.org/10.1111/anec.12206
3. Aro AL, Huikuri HV, Tikkanen JT et al. QRS-T angle as a predictor of sudden cardiac death in a middle-aged general population. EP Europace 2012;14:872–6. https://doi.org/10.1093/europace/eur393
4. Yamazaki T, Froelicher VF, Myers J, Chun S, Wang P. Spatial QRS-T angle predicts cardiac death in a clinical population. Heart Rhythm 2005;2:73–8. https://doi.org/10.1016/j.hrthm.2004.10.040
5. Kardys I, Kors JA, van der Meer IM, Hofman A, van der Kuip DAM, Witteman JCM. Spatial QRS-T angle predicts cardiac death in a general population. Eur Heart J 2003;24:1357–64. https://doi.org/10.1016/S0195-668X(03)00203-3
