Assessment of the Spatial QRS-T Angle by Vectorcardiography: Current Data and Perspectives

Spatial QRS-T angle can indicate presence of myocardial fibrosis in pediatric and young adult patients with hypertrophic cardiomyopathy

BACKGROUND

Myocardial fibrosis, expressed as late gadolinium enhancement (LGE) on cardiac magnetic resonance imaging (CMR), is an important risk factor for malignant cardiac events in hypertrophic cardiomyopathy (HCM). However, CMR is not easily available, expensive, also needing intravenous access and contrast.

OBJECTIVE

To determine if derived vectorcardiographic spatial QRS-T angles, an aspect of advanced ECG (A-ECG), can indicate LGE to appropriately prioritize young HCM-patients for CMR.

METHODS

Young patients (age 7-31 years) with clinical HCM (N = 19) or genotype-positive but phenotype-negative (G+ P-) results (N = 6) and nine healthy volunteers were evaluated for LGE by CMR at a single centre between 2011 and 2018. A-ECG was performed within 4 months before and 6 months after CMR and evaluated for spatial mean and peaks QRS-T angles. ECG Risk-score and frontal, two-dimensional QRS-T angle were also calculated from the 12‑lead ECG.

RESULTS

All QRS-T angles were significantly higher in the HCM group with LGE as compared to the HCM group without LGE, and the G+ P- and Healthy groups. Only HCM-patients showed LGE (11/19). The optimal cut-offs for indicating LGE were > 50° for the spatial peaks (AUC = 0.98 [95 %CI 0.95-1.00], sensitivity 100 %, specificity 93 %; p < 0.001), >80° for the spatial mean (AUC = 0.91; p < 0.001), and > 60° for the frontal QRS-T angles (AUC = 0.85; p < 0.001), and > 2 points for an established ECG risk-score (AUC = 0.90, p < 0.001).

CONCLUSION

A spatial peaks QRS-T angle >50° has excellent sensitivity and specificity as a marker of myocardial fibrosis in a young patients with HCM, and can be useful for management and follow-up of such patients.

Review of Processing Pathological Vectorcardiographic Records for the Detection of Heart Disease

Vectorcardiography (VCG) is another useful method that provides us with useful spatial information about the electrical activity of the heart. The use of vectorcardiography in clinical practice is not common nowadays, mainly due to the well-established 12-lead ECG system. However, VCG leads can be derived from standard 12-lead ECG systems using mathematical transformations. These derived or directly measured VCG records have proven to be a useful tool for diagnosing various heart diseases such as myocardial infarction, ventricular hypertrophy, myocardial scars, long QT syndrome, etc., where standard ECG does not achieve reliable accuracy within automated detection. With the development of computer technology in recent years, vectorcardiography is beginning to come to the forefront again. In this review we highlight the analysis of VCG records within the extraction of functional parameters for the detection of heart disease. We focus on methods of processing VCG functionalities and their use in given pathologies. Improving or combining current or developing new advanced signal processing methods can contribute to better and earlier detection of heart disease. We also focus on the most commonly used methods to derive a VCG from 12-lead ECG.

Widened QRS-T Angle May Be a Measure of Poor Ventricular Stretch During Exercise Among On-duty Firefighters

BACKGROUND

The spatial QRS-T angle is a measure of repolarization heterogeneity and may be a predictor of poor ventricular health. It is unknown whether a relationship exists between QRS-T angle and blood pressure (BP) during exercise.

OBJECTIVE

The purpose of this study was to evaluate the potential relationship between QRS-T angle and BP during exercise, which may be indicative of ventricular stretch.

METHODS

Ambulatory 12-lead 24-hour Holter electrocardiographic monitoring for QRS-T angle measurement was followed by exercise testing with BP (mm Hg) recordings taken preexercise, maximum achieved BP during exercise, and 2 minutes postexercise. Blood pressure recovery was calculated by subtracting the maximal and 2-minute postexercise BPs. Means (± standard deviation) and percentages are presented. Pearson correlations (r) among all QRS-T angles and all BP measures were performed. One-way analysis of variance was conducted on classification of QRS-T angle and all BP measures.

RESULTS

One hundred eleven firefighters (95.5% male; mean age, 44 years) were included in this analysis. Twenty-seven percent of the firefighters had either a borderline (100°-139°) or widened (≥140°) QRS-T angle. Although the analysis of variance was not statistically significant, a near-statistically significant negative correlation existed between QRS-T angle and maximum diastolic BP (r = -0.190, P = .05), and a statistically significant relationship existed between QRS-T angle and postexercise diastolic BP (r = -0.261, P = .008).

CONCLUSIONS

A negative correlation existed between QRS-T angle and maximal diastolic BP and postexercise diastolic BP. Lower maximum diastolic BP during and after exercise may be a sign of poor ventricular stretch. A widened spatial QRS-T angle may represent poor ventricular stretch.

Spatial QRS-T Angle and Cognitive Decline in Older Subjects

BACKGROUND

An abnormally wide spatial QRS-T angle on an ECG is a marker of heterogeneity in electrical activity of cardiac ventricles and is linked with cardiovascular events. Growing evidence suggests that cardiac dysfunction might signal future cognitive decline.

OBJECTIVE

In this study, we investigated whether spatial QRS-T angle associates with future cognitive decline in older subjects at high cardiovascular risk.

METHODS

We included 4,172 men and women (mean age 75.2±3.3 years) free of cardiac arrhythmias from the PROSPER cohort. Spatial QRS-T angle was calculated from baseline 12-lead ECGs using a matrix transformation method. Cognitive function was assessed using 4 neuropsychological tests including Stroop test, letter-digit coding test, immediate and delayed picture word learning tests. Cognitive function was assessed at baseline and repeatedly during a mean follow-up time of 3.2 years. Using linear mixed models, we calculated the annual changes of cognitive scores in sex-specific thirds of spatial QRS-T angle.

RESULTS

Participants with wider spatial QRS-T angle had a steeper decline in letter-digit coding test (β= -0.0106, p = 0.004), immediate picture-word learning test (β= -0.0049, p = 0.001), and delayed picture-word learning test (β= -0.0055, p = 0.013). All associations were independent of arrhythmias, cardiovascular risk factors, comorbidities, medication use, cardiovascular events, and other ECG abnormalities including QRS duration, QTc interval, T wave abnormalities, and left ventricular hypertrophy.

CONCLUSION

Abnormal cardiac electrical activity characterized by wide spatial QRS-T angle associates with accelerated cognitive decline independent of conventional cardiovascular factors. These findings suggest a link between a non-traditional ECG measure of pre-clinical cardiac pathology and future cognitive decline.

Frontal planar QRS/T angle can be a prognostic factor in the early postoperative period of patients undergoing coronary bypass surgery

BACKGROUND

Wide QRS/T angle reflects the ventricular repolarization heterogeneity and has been found in association with cardiac morbidity and mortality in various study populations. However, literature data about the availability of QRS/T angle in patients undergoing cardiac surgery has not yet been available.

METHODS

A total of 157 patients who underwent isolated coronary artery bypass surgery were included in this study. A preoperative 12-lead ECG was obtained one day before surgical procedure. The absolute difference between the frontal QRS wave axes and T-wave axes was defined as frontal planar QRS/T angle. Afterwards, patients were divided into two groups according to their frontal planar QRS/T angle (the cut-off value as 90°).

RESULTS

Group 1 consisted of 109 patients with frontal planar QRS/T angle of <90, and the remaining 48 patients with frontal planar QRS/T angle 90 were placed into group 2. Mean EuroSCORE was much higher in group 2. There were significant differences for positive inotropic agent usage (27.5% for group 1 versus 58.3% for group 2, P < .001) and the prevalence of postoperative atrial fibrillation (11.9% for group 1 versus 31.2% for group 2, P = .004) between the two groups. In multivariate logistic regression analysis, used to determine the independent predictors of positive inotropic usage in the early postoperative period, only frontal planar QRS/T angle (OR: 0.989, 95% CI: 0.981-0.997, P = .008) and EuroSCORE (OR: 0.792, 95% CI: 0.646-0.971, P = .025) were found to be statistically significant.

CONCLUSION

We found that frontal planar QRS/T angle might be an important preoperative parameter in predicting the need for inotropic drugs in the early postoperative period following coronary artery bypass surgery.

Usefulness of the QRS-T angle to improve long-term risk stratification of patients with acute myocardial infarction and depressed left ventricular ejection fraction

In light of the low cost, the widespread availability of the electrocardiogram, and the increasing economic burden of the health-related problems, we aimed to analyze the prognostic value of automatic frontal QRS-T angle to predict mortality in patients with left ventricular (LV) systolic dysfunction after acute myocardial infarction (AMI). About 467 consecutive patients discharged with diagnosis of AMI and with LV ejection fraction ≤40% were followed during 3.9 years (2.1 to 5.9). From them, 217 patients (47.5%) died. The frontal QRS-T angle was higher in patients who died (116.6±52.8 vs 77.9±55.1, respectively, p<0.001). The QRS-T angle value of 90° was the most accurate to predict all-cause cardiac death. After multivariate analysis, frontal QRS-T angle remained as an excellent predictor of all-cause and cardiac deaths, increasing the mortality 6% per each 10°. For the global mortality, the hazard ratio for a QRS-T angle>90° was 2.180 (1.558 to 3.050), and for the combined end point of cardiac death and appropriate implantable cardioverter defribrillator therapy, it was 2.385 (1.570 to 3.623). This independent predictive value was maintained even after adjusting by bundle brunch block, ST-elevation AMI, and its localization. In conclusion, a wide automatic frontal QRS-T angle (>90°) is a good discriminator of long-term mortality in patients with LV systolic dysfunction after an AMI. The ability to easily measure it from a standard 12-lead electrocardiogram together with its prognostic value makes the frontal QRS-T angle an attractive tool to help clinicians to improve risk stratification of those patients.

Relations between QRS|T angle, cardiac risk factors, and mortality in the third National Health and Nutrition Examination Survey (NHANES III)

On the surface electrocardiogram, an abnormally wide QRS|T angle reflects changes in the regional action potential duration profiles and in the direction of the repolarization sequence, which is thought to increase the risk of ventricular arrhythmia. We investigated the relation between an abnormal QRS|T angle and mortality in a nationally representative sample of subjects without clinically evident heart disease. We studied 7,052 participants ≥40 years old in the third National Health and Nutrition Examination Survey with 12-lead electrocardiograms. Those with self-reported or electrocardiographic evidence of a previous myocardial infarction, QRS duration of ≥120 ms, or history of heart failure were excluded. Borderline and abnormal spatial QRS|T angles were defined according to gender-specific 75th and 95th percentiles of frequency distributions. All-cause (1,093 women and 1,191 men) and cardiovascular (462 women and 455 men) mortality during the 14-year period was assessed through linkage with the National Death Index. On multivariate analyses, an abnormal spatial QRS|T angle was associated with an increased hazard ratio (HR) for cardiovascular mortality in women (HR 1.82, 95% confidence interval 1.05 to 3.14) and men (HR 2.21, 95% confidence interval 1.32 to 3.68). Also, the multivariate adjusted HR for all-cause mortality associated with an abnormal QRS|T angle was 1.30 (95% confidence interval 0.95 to 1.78) for women and 1.87 (95% confidence interval 1.29 to 2.7) for men. A borderline QRS|T angle was not associated with an increased risk of all-cause or cardiovascular mortality. In conclusion, an abnormal QRS|T angle, as measured on a 12-lead electrocardiogram, was associated with an increased risk of cardiovascular and all-cause mortality in this population-based sample without known heart disease.

Significance of asymptomatic bradycardia for subsequent pacemaker implantation and mortality in patients >60 years of age

Sinus bradycardia may be more significant in older patients than in a younger group because it could signal important or advanced conduction system and/or cardiac disease potentially modifiable with pacemaker implantation. We evaluated the clinical need for subsequent pacemaker implantation and mortality rate in outpatients >60 years of age with relatively asymptomatic bradycardia (heart rate <55 beats/min without a subsequent pacemaker implantation within 2 weeks) or not (heart rate 60 to 70 beats/min). The 2 groups were matched against pacemaker implantation and death records but without data on indication or cause. Kaplan-Meier survival curves and univariate and multivariable models examined pacemaker implantation and all-cause mortality. The cohort consisted of 470 patients with and 2,090 without asymptomatic bradycardia. Mean follow-up period was 7.2 ± 2.9 years during which 137 patients (5.4%) underwent pacemaker implantation and 748 (29.2%) died. Incidence of pacemaker placement was higher in the bradycardia cohort (9% vs 5%, p <0.001). The higher incidence of pacemaker implantation did not appear in the first 4 years. Univariate analysis showed no increase in mortality in the bradycardia group (hazard ratio 0.87, 95% confidence interval 0.72 to 1.04, p = 0.130), whereas multivariable analysis showed protection (hazard ratio 0.78, 95% confidence interval 0.65 to 0.94, p = 0.010). In conclusion, older patients with asymptomatic bradycardia have a very low rate of pacemaker implantation, annualized to <1% per year. Their higher rate of pacemaker implantation compared to outpatients without bradycardia shows a latency period of approximately 4 years. It has no adverse impact on all-cause mortality and may even be protective.

The ECG vertigo in diabetes and cardiac autonomic neuropathy

The importance of diabetes in the epidemiology of cardiovascular diseases cannot be overemphasized. About one third of acute myocardial infarction patients have diabetes, and its prevalence is steadily increasing. The decrease in cardiac mortality in people with diabetes is lagging behind that of the general population. Cardiovascular disease is a broad term which includes any condition causing pathological changes in blood vessels, cardiac muscle or valves, and cardiac rhythm. The ECG offers a quick, noninvasive clinical and research screen for the early detection of cardiovascular disease in diabetes. In this paper, the clinical and research value of the ECG is readdressed in diabetes and in the presence of cardiac autonomic neuropathy.