Arie C. Maan

Normal limits of the spatial QRS-T angle and ventricular gradient in 12-lead electrocardiograms of young adults: dependence on sex and heart rate

BACKGROUND AND PURPOSE Normal limits of the spatial QRS-T angle and spatial ventricular gradient (SVG) are only available from Frank vectorcardiograms (VCGs) of male subjects. We determined normal limits for these variables derived from standard 12-lead electrocardiograms (ECGs) of 660 male and female students aged 18 to 29 years. METHODS A computer algorithm was used that constructed approximated VCG leads by inverse Dower matrix transformation of the 12-lead ECG and subsequently calculated the spatial QRS-T angle, SVG magnitude, and orientation. RESULTS In female subjects, the QRS-T angle was more acute (females, 66 degrees +/- 23 degrees; normal, 20 degrees-116 degrees; males, 80 degrees +/- 24 degrees; normal, 30 degrees-130 degrees; P < .001), and the SVG magnitude was smaller (females, 81 +/- 23 mV x ms; normal, 39-143 mV x ms; males, 110 +/- 29 mV x ms; normal, 59-187 mV x ms; P < .001) than in male subjects. The male SVG magnitude in our study was larger than that computed in Frank VCGs (79 +/- 28 mV.ms; P < .001). CONCLUSIONS The spatial QRS-T angle and SVG depend strongly on sex. Furthermore, normal limits of SVG derived from Frank VCGs differ markedly from those derived from VCGs synthesized from the standard ECG. As nowadays, VCGs are usually synthesized from the 12-lead ECG; normal limits derived from the standard ECG should preferably be used.

The importance of high-frequency paced breathing in spectral baroreflex sensitivity assessment

Objective Computation of the low-frequency (LF) blood pressure variability (BPV) to heart rate variability (HRV) transfer-index is a common method to assess baroreflex sensitivity (BRS), tacitly assuming that all LF-HRV is caused by baroreflex feedback of LF-BPV. However, respiration may also cause HRV by mechanisms not involving the baroreflex. Application of narrow-band (controlled) high-frequency breathing would keep such non-baroreflex-mediated HRV best out of the LF band. Spontaneous breathing, because of its broad-band character, might cause extra, non-baroreflex-mediated, HRV in the LF band, while paced LF breathing would even concentrate most non-baroreflex-mediated HRV in the LF band. Our study addresses the likely resulting BRS overestimation. Design We recorded HRV and BPV in 20 healthy young subjects in the sitting position. We varied the sympathovagal balance by gradual leg-lowering from horizontal till 60°. At each angle the subjects performed controlled 0.10 Hz, spontaneous, and controlled 0.25 Hz respiration. Results Resting BRS values were 15.5(7.2), 13.1(3.7), and 11.6(6.2) ms/mmHg, respectively. Both the 15/min and the free breathing values differed significantly, P < 0.01 and P = 0.04, from the 6/min breathing value. With lowered legs, the BRS values were 8.2(3.4), 8.3(2.9), and 8.3(3.4) ms/mmHg, respectively. Conclusion Controlled 6/min breathing caused significant BRS overestimation under resting conditions. For the group, spontaneous respiration yielded acceptable BRS values, but individual BRS values deviated sometimes considerably. Conversely, with gravitational load, the respiratory pattern had only minor impact on BRS. Our results demonstrate that the risk of an overestimated BRS value is realistic as long as respiration is not controlled and of high-frequency.

LEADS: an interactive research oriented ECG/VCG analysis system

We recently developed a MATLAB program, LEADS (Leiden ECG analysis and decomposition software), for research oriented ECG/VCG analysis. Any eight-channel recording in comma-separated values format (CSV) can be input. After detection of QRST complexes in the spatial velocity signal and baseline correction, LEADS generates a default selection of beats for subsequent averaging. The analyst may then adjust this selection, after which the selected beats are averaged to generate a representative and low-noise averaged beat (ECG and VCG). In this beat, LEADS computes default onset-QRS, end-QRS and end-T instants, which may be subsequently reviewed/edited. Finally, several conventional and advanced ECG and VCG parameters are automatically computed, and the results are output in the form of a CSV file. By virtue of the combination of adjustable configuration settings and interactive procedures, LEADS has provided us with the ability to reliably analyze ECGs ranging from normal to highly pathological

Changes in frequency of premature complexes and heart rate variability related to shift work.

OBJECTIVES To investigate whether an increased risk of cardiovascular disease might be caused by increased arrhythmogeneity and by unfavourable changes in autonomic cardiac control the changes in the occurrence of premature complexes (PVCs) and in heart rate variability (HRV) were studied in subjects who started to work in shifts. METHODS 1 Year changes in frequency of PVCs and HRV were measured in 49 shift workers and 22 control subjects working in daytime. All respondents were starting in a new job in integrated circuit or waste incinerator plants. RESULTS The incidence of PVC increased significantly in shift workers over the 1 year follow up, compared with daytime workers. The frequency of ventricular extrasystoles increased in 48.9% of the shift workers, and in 27.3% of the daytime workers. The Spearman correlation coefficient between the number of nights worked and the change in PVCs was 0.33 (p=0.004). A small non-significant unfavourable change in HRV was found in both the shift and daytime workers. CONCLUSIONS A change in arrhythmogeneity, but not in cardiac autonomic control, might explain the increased risk of cardiovascular disease in shift workers.

Cardiac autonomic neuropathy in patients with diabetes and no symptoms of coronary artery disease: comparison of 123I-metaiodobenzylguanidine myocardial scintigraphy and heart rate variability

PurposeThe purpose of this study was to evaluate the prevalence of cardiac autonomic neuropathy (CAN) in a cohort of patients with type 2 diabetes, truly asymptomatic for coronary artery disease (CAD), using heart rate variability (HRV) and 123I-metaiodobenzylguanidine (123I-mIBG) myocardial scintigraphy.MethodsThe study group comprised 88 patients with type 2 diabetes prospectively recruited from an outpatient diabetes clinic. In all patients myocardial perfusion scintigraphy, CAN by HRV and 123I-mIBG myocardial scintigraphy were performed. Two or more abnormal tests were defined as CAN-positive (ECG-based CAN) and one or fewer as CAN-negative. CAN assessed by 123I-mIBG scintigraphy was defined as abnormal if the heart-to-mediastinum ratio was <1.8, the washout rate was >25%, or the total defect score was >13.ResultsThe prevalence of CAN in patients asymptomatic for CAD with type 2 diabetes and normal myocardial perfusion assessed by HRV and 123I-mIBG scintigraphy was respectively, 27% and 58%. Furthermore, in almost half of patients with normal HRV, 123I-mIBG scintigraphy showed CAN.ConclusionThe current study revealed a high prevalence of CAN in patients with type 2 diabetes. Secondly, disagreement between HRV and 123I-mIBG scintigraphy for the assessment of CAN was observed.

Correlation of heart rate variability with cardiac functional and metabolic variables in cyclists with training induced left ventricular hypertrophy

OBJECTIVE To examine the correlation between heart rate variability and left ventricular mass in cyclists with an athlete’s heart. METHODS Left ventricular mass and diastolic function were determined at rest and myocardial high energy phosphates were quantified at rest and during atropine–dobutamine stress in 12 male cyclists and 10 control subjects, using magnetic resonance techniques. Ambulatory 24 hour ECG recordings were obtained, and time and frequency domain heart rate variability indices were computed. RESULTS In the cyclists, the mean of all RR intervals between normal beats (meanNN), the SD of the RR intervals, and their coefficient of variation were significantly greater than in control subjects (p < 0.01, p < 0.01, and p < 0.05, respectively). For cyclists and control subjects, only meanNN correlated with left ventricular mass (r = 0.48, p = 0.038). The heart rate variability indices that correlated with functional or metabolic variables were: meanNN v E/A peak (the ratio of peak early and peak atrial filling rate) (r = 0.48, p = 0.039); the root mean square of successive differences in RR intervals among successive normal beats v E/A area (ratio of peak early and peak atrial filling volume) (r = 0.48, p = 0.040); percentage of successive RR intervals differing by more than 50 ms v the phosphocreatine to ATP ratio at rest (r = 0.54, p = 0.017); and the SD of the average RR intervals during all five minute periodsv the phosphocreatine to ATP ratio during stress (r = 0.60, p = 0.007). CONCLUSIONS Highly trained cyclists have increased heart rate variability indices, reflecting increased cardiac vagal control compared with control subjects. Left ventricular mass has no major influence on heart rate variability, but heart rate variability is significantly correlated with high energy phosphate metabolism and diastolic function.

Incremental prognostic value of an abnormal baseline spatial QRS-T angle in chronic dialysis patients.

AIMS In order to improve the abysmal outcome of dialysis patients, it is critical to identify patients with a high mortality risk. The spatial QRS-T angle, which can be easily calculated from the 12 lead electrocardiogram (ECG), might be useful in the prognostication in dialysis patients. The objective of this study was to establish the prognostic value of the spatial QRS-T angle. METHODS AND RESULTS All patients who initiated dialysis therapy between 2002 and 2009 in the hospitals of Leiden (LUMC) and Amsterdam (AMC) at least 3 months on dialysis were included. The spatial QRS-T angle was calculated, from a routinely acquired ECG, and its relationship with mortality was assessed. An abnormal spatial QRS-T angle was defined as ≥ 130° in men and ≥ 116° in women. In total, 277 consecutive patients (172 male, mean age 56.3 ± 17.0) were included. An abnormal spatial QRS-T angle was associated with a higher risk of death from all causes [hazard ratio (HR) 2.33; 95% confidence interval (CI) 1.46-3.70] and especially a higher risk of sudden cardiac death (HR 2.99; 95% CI 1.04-8.60). Furthermore, an abnormal spatial QRS-T angle was of incremental prognostic value, when added to a risk model consisting of known risk factors. CONCLUSION In chronic dialysis patients the spatial QRS-T angle is a significant and independent predictor of all-cause and especially sudden cardiac death. It implies that this parameter can be used to identify high risk patients.

Reconstruction of standard 12-lead electrocardiograms from 12-lead electrocardiograms recorded with the Mason-Likar electrode configuration.

Electrocardiograms (ECGs) made with Mason-Likar electrode configuration (ML-ECGs) show well-known differences from standard 12-lead ECGs (Std-ECGs). We recorded, simultaneously, Std-ECGs and ML-ECGs in 180 subjects. Using these ECGs, 8 x 8 individual and general conversion matrices were created by linear regression, and standard ECGs were reconstructed from ML-ECGs using these matrices. The performance of the matrices was assessed by the root mean square differences between the original Std-ECGs and the reconstructed standard ECGs, by the differences in major ECG parameters, and by comparison of computer-generated diagnostic statements. As a result, we conclude that, based on the root mean square differences, reconstructions with 8 x 8 individual matrices perform significantly better than reconstructions with the group matrix and perform equally well with respect to the calculation of major electrocardiographic parameters, which gives an improved reliability of the QRS frontal axis and the maximal QRS and T amplitudes. Both types of matrices were able to reverse the underdiagnosis of inferior myocardial infarctions and the erroneous statements about the QRS frontal axis that arose in the ECGs that were made by using the Mason-Likar electrode positions.

Electrocardiographic detection of right ventricular pressure overload in patients with suspected pulmonary hypertension

BACKGROUND AND PURPOSE Early, preferably noninvasive, detection of pulmonary hypertension improves prognosis. Our study evaluated the diagnostic accuracy of the electrocardiographically derived Butler-Leggett (BL) score and ventricular gradient (VG) to estimate mean pulmonary artery pressure (PAP). METHODS In 63 patients with suspected pulmonary hypertension, BL score and VG were calculated. The VG was projected on a direction optimized for detection of right ventricular pressure overload (VG-RVPO). BL score and VG-RVPO were entered in multiple linear regression analysis and the diagnostic performance to detect PH (invasively measured mean PAP ≥ 25 mmHg) was assessed with receiver operating characteristic analysis. RESULTS Both BL score and VG-RVPO correlated significantly with mean PAP (r=0.45 and r=0.61, respectively; P<0.001). Combining BL score and VG-RVPO increased the correlation to 0.67 (P<0.001). The diagnostic performance of this combination for the detection of PH was good with an area under the curve of 0.79 (P<0.001). CONCLUSION Combination of the BL score and VG-RVPO allows for accurate detection of increased PAP.

24-Hour Heart Rate Variability in Shift Workers: Impact of Shift Schedule

24‐Hour Heart Rate Variability in Shift Workers: Impact of Shift Schedule: L.G.P.M. van Amelsvoort, et al. Department of Epidemiology, Maastricht University—Disturbance of the circadian pattern of cardiac autonomic control by working at night when the physiological system anticipates rest could explain part of the elevated cardiovascular risk in shift workers. Analysis of Heart Rate Variability (HRV) is a non‐invasive tool to estimate disturbances of the cardiac autonomic control. To assess the influence of working at night on cardiac autonomic control, HRV levels were determined in shift workers. 24‐h ECG recordings were made during a day on morning shift and a day on night shift. Within person differences between a morning and a night shift were calculated. Possible modification of the reported effects by the shift schedule was determined. Significantly elevated mean %LF during sleep was found on a day worked on night shift compared with a day on day shift (%LF + 3.04, P<0.01). Type of shift schedule was found to be a significant modifier of this effect. The difference in %LF between the night and day shift for the different shift schedules apart were: + 0.88% for the workers in the fast forward rotating shift, + 3.06% for the fast backward rotating shift, + 6.15% (P<0.001) for the medium speed backward rotating shift and + 1.18% for the shift workers without a regular shift schedule. The results suggest an increased sympathetic dominance during a night shift sleep, indicating an inferior sleep quality. Optimisation of this schedule might diminish this impact and could contribute to a reduction of the cardiovascular disease risk among shift workers.