Right lateral decubitus position reduces QT dispersion in patients with chronic heart failure

QRS-T morphology measured from exercise electrocardiogram as a predictor of cardiac mortality

AIMS

Total cosine R-to-T (TCRT) measured from the standard 12-lead electrocardiogram (ECG) reflects the spatial relationship between depolarization and repolarization wavefronts and a low TCRT value is a marker of poor prognosis. We tested the hypothesis that measurement of TCRT or QRS/T angle from exercise ECG would provide even more powerful prognostic information.

METHODS AND RESULTS

The prognostic significances of TCRT and QRS/T angle were assessed from exercise ECG recordings in 1297 patients [age 56 ± 13 years (mean ± SD), 67% males] undergoing a clinically indicated bicycle stress-test and the subsequent follow-up. During an average follow-up of 45 ± 12 months, 74 patients died (5.7%); 34 (2.6%) were cardiac deaths, and 24 (1.9%) were sudden cardiac deaths. Total cosine R-to-T and QRS/T angle exhibited a correlation with the RR intervals in the total cohort, but the individual responses were variable, e.g. median correlation of TCRT-RR was 0.89 with an inter-quartile range from 0.55 to 0.98. A reduced correlation of TCRT-RR during the recovery phase of exercise ECG predicted cardiac death [adjusted heart rate (HR) 3.5, 95% confidence interval (CI): 1.8-6.8, P= 0.001] similarly as the baseline TCRT measured from ECG at rest (adjusted HR 3.4, 95% CI: 1.4-8.1, P= 0.01). The poor correlation between the TCRT-RR both during the exercise and recovery was specifically related to a risk of sudden cardiac death (adjusted HR 6.2, 95% CI: 2.1-17.8, P< 0.001).

CONCLUSIONS

Loss of rate-adaptation of the spatial relationship between depolarization and repolarization wavefronts is a strong predictor of cardiac death, especially of sudden cardiac death.

Spatial QRS-T angle in peritoneal dialysis patients: association with carotid artery atherosclerosis, coronary artery calcification and troponin T

BACKGROUND

Abnormal values of the spatial angle between the directions of ventricular depolarization and repolarization (QRS-T) predict potently arrhythmic events and mortality in various patients groups. The study was designed to estimate QRS-T in a group of peritoneal dialysis (PD) patients, and to assess the possible association between QRS-T and coronary artery calcification (CAC), atherosclerosis, and some biochemical measurements.

METHODS

The angular differences between the maximum spatial QRS and T vectors were reconstructed from ECGs in 57 selected PD patients and in 54 controls. In patients CAC score was performed by using multi-row computed tomography. Atherosclerotic disease was assessed by measuring carotid arteries' intima-media thickness (IMT) and plaque score (sum of the maximum thicknesses in mm of all plaques on both sides) by using an ultrasound scanner.

RESULTS

QRS-T was higher in patients compared with controls (34.79% B111.97 and 14.95% B17.87 respectively; P < 0.001). Median CAC score equalled 104.5 Agatson units (Au) (range, 0-2478). IMT was 0.832% B10.208, and atherosclerotic plaques were detected in 82.5% of patients. The plaque score was 7.97% B14.49. QRS-T was higher in patients with CAC score >400 Au compared with patients with CAC score <400 Au (P = 0.011). The results of univariate linear regression analysis showed correlation between QRT-T and dialysis duration (r = 0.305, P = 0,020), LVMI (r = 0.311, P = 0.017), HDL (r = -0.361, P = 0.006), cTnT (r = 0.442, P < 0.001), plaque score (r = 0.403, P = 0.001) and CAC score (r = 0.451, P < 0.001). On multivariate analysis, CAC score, plaque score and troponine T were found to be independent predictors of QRS-T values.

CONCLUSIONS

QRS-T is high in PD patients and is mainly associated with coronary artery calcium burden, atherosclerosis and troponin T elevation. The possible clinical importance of the higher QRS-T in PD patients remains to be confirmed in further studies.