Why complicate an important task? An orderly display of the limb leads in the 12-lead electrocardiogram and its implications for recognition of acute coronary syndrome.

BACKGROUND: In the standard ECG display, limb leads are presented in a non-anatomical sequence: I, II, III, aVR, aVL, aVF. The Cabrera system is a display format which instead presents the limb leads in a cranial/left-to-caudal/right sequence, i.e. in an anatomically sequential order. Lead aVR is replaced in the Cabrera display by its inverted version, -aVR, which is presented in its logical place between lead I and lead II. MAIN TEXT: In this debate article possible implications of using the Cabrera display, instead of the standard, non-contiguous lead display, are presented, focusing on its use in patients with possible acute coronary syndrome. The importance of appreciating reciprocal limb-lead ECG changes and the diagnostic and prognostic value of including aVR or lead -aVR in ECG interpretation in acute coronary syndrome is covered. Illustrative cases and ECGs are presented with both the standard and contiguous limb lead display for each ECG. A contiguous lead display is useful when diagnosing acute coronary syndrome in at least 3 ways: 1) when contiguous leads are present adjacent to each other, identification of ST elevation in two contiguous leads is simple; 2) a contiguous lead display facilitates understanding of lead relationships as well as reciprocal changes; 3) it makes the common neglect of lead aVR unlikely. CONLUSIONS: It is logical to display the limb leads in their sequential anatomical order and it may have advantages both in diagnostics and ECG learning.

Comparison of two commonly used reference materials for exercise bicycle tests with a Swedish clinical database of patients with normal outcome.

BACKGROUND: Reference values for working capacity, blood pressure, heart rate, perceived exertion, etc. during bicycle exercise tests have been sought after for many years. This is because earlier commonly used reference values for physical work capacity have been either too low or too high when compared to the clinical experience of several Swedish departments of clinical physiology. The aim of the study was to compare two commonly used reference materials with normal outcomes from a clinical database. METHODS: Data from a clinical database of standardized exercise tests in Kalmar, Sweden, between 2004 and 2012, and having been judged as normal, were divided into 5-year categories of 5-10 to 75-80 years of age covering people from 7 to 80 years of age. RESULTS: Maximal working capacity (Wmax ), maximal heart rate, maximal systolic blood pressure and maximal perceived exertion are presented for each of the 15 age categories. Regression equations are also presented for each sex with age and height as independent predictors. Quantitative comparisons of Wmax are calculated for the three materials and possible explanations discussed. CONCLUSIONS: Values of Wmax lie between the two reference materials most commonly used in Sweden. In addition, the present material covers subjects aged 7-19 years.

Signal-averaged electrocardiography in normal newborn infants.

Signal-averaged electrocardiograms (SAECGs) were recorded with bipolar orthogonal and standard 12-lead settings in 29 term healthy newborn infants. SAECGs performed with the two lead configurations were similar in quality and quantity. For the duration of the QRS complex (QRSD), the upper limit of normality for newborn infants can be set to 100 ms. It is similar in individual bipolar orthogonal and individual standard 12-lead recordings as well as in filtered QRSD in the vectorcardiograms (the vector magnitude, VM, and the sum of extremity leads). In individual leads of bipolar orthogonal and standard 12-lead recordings, root-mean-square voltage of the terminal 40 ms of the QRS complex (RMS40) is widely scattered and unsuitable as discriminant variable. For VM and the sum of the extremity leads, the same reference values for RMS40 and duration of low-amplitude signal can be used as applied in adults. Individual lead recordings provide complementary information in addition to vectorcardiograms. There are practical advantages using standard 12-lead compared to conventional bipolar orthogonal configurations. The widespread use of standard 12-lead ECG in routine medical practice makes its utility advantageous also in performing signal-averaged electrocardiography.

Detection of body position changes using the surface electrocardiogram.

A method for detecting body position changes that uses the surface vectorcardiogram (VCG) is presented. Such changes are often manifested as sudden shifts in the electrical axis of the heart and can erroneously be interpreted as acute ischaemic events. Axis shifts were detected by analysing the rotation angles obtained from the alignment of successive VCG loops to a reference loop. Following the rejection of angles originating from noise events, the detection of body position changes was performed on the angle series using a Bayesian approach. On a database of ECG recordings from normal subjects performing a predefined sequence of body position changes, a detection rate of 92% and a false alarm rate of 7% was achieved.

Quantification of myocardial hypoperfusion with 99m Tc-sestamibi in patients undergoing prolonged coronary artery balloon occlusion.

Percutaneous transluminal coronary angioplasty provides an excellent opportunity to investigate the location and quantity of hypoperfusion during sudden complete occlusion of one of the major coronary arteries. Thirty-five patients referred for elective percutaneous transluminal coronary angioplasty were injected intravenously with 99mTc-sestamibi during balloon inflation. To visualize and quantify the hypoperfused region, a map of perfusion was constructed from that occlusion study and from the control study performed on the following day. Patients were divided into groups according to proximal or distal occlusion within each of the three coronary arteries. The region of myocardium supplied by each coronary artery varied in location and extended outside the typical borders for all arteries, but most prominently for the left circumflex coronary artery. The quantities of hypoperfusion varied within each artery group, but the average hypoperfusion was greater for the left anterior descending coronary artery than for either the right coronary artery or the left circumflex coronary artery. It is concluded that the quantities of hypoperfusion were highly variable within each artery group. Occlusion of the left anterior descending coronary artery was associated with the largest ischaemic region. The area of hypoperfusion extended outside the typical borders, most prominently for the left circumflex coronary artery.

Tolerability of concurrent use of nicotine gum and smoking in healthy volunteers.

Although nicotine replacement therapy (NRT) is mainly licensed as an aid for smoking cessation, many smokers alternate NRT with cigarettes. This study evaluated the cardiovascular tolerability of nicotine gum plus smoking. This open, three-way, randomized, multiple-dose, crossover study involved 19 healthy adult volunteer smokers. Three treatments (placebo gum+cigarette vs. nicotine 4-mg gum+unlit cigarette vs. nicotine 4-mg gum+cigarette) were each administered hourly seven times during one study day. Plasma nicotine, ECG variables (ST60 and ST(slope)), heart rate, and blood pressure were measured at rest and during/after 5 min exercise tests. Mean plasma nicotine levels were higher with gum plus smoking than with either gum or smoking alone. After the final administration, mean levels with gum plus smoking were 39.5 (range 27.6-54.4) ng/ml vs. 19.6 (11.8-30.1) ng/ml with gum and 22.6 (6.6-36.6) ng/ml with smoking alone. No signs of myocardial ischaemia were observed during concomitant use of gum plus smoking, despite high plasma nicotine levels. Decreases of ST60 and ST(slope) were observed in all treatment groups during exercise but were asymptomatic. Concomitant gum plus smoking did not increase the incidence of extrasystoles or arrhythmia. No serious adverse events occurred during the study. In conclusion, there were no signs of myocardial ischaemia during multiple submaximal exercise tests in healthy volunteers while smoking and using nicotine 4-mg gum.

The absence of high-frequency QRS changes in the presence of standard electrocardiographic QRS changes of old myocardial infarction.

BACKGROUND: This study compares the high-frequency QRS components (HF-QRS) in patients with and without standard electrocardiogram (ECG) changes indicative of old myocardial infarction (MI). Previous studies have indicated that patients with an old MI differ in their HF-QRS compared with healthy subjects. The HF-QRS has been reported to be decreased during acute coronary occlusion and increased after reperfusion. However, there is controversy about the appearance of HF-QRS after the acute phase of MI. METHODS: A total of 154 patients were included, 57 with and 97 without QRS changes of old MI on the standard ECG. The patients with old MI were divided into subgroups on the basis of the MI location indicated by the standard ECG. Signal-averaged ECGs from the 12 standard leads were recorded. The root-mean-square values of the HF-QRS were determined within two frequency bands: 150 to 250 Hz and 80 to 300 Hz. RESULTS: There was a large interindividual variation in HF-QRS in patients without MI as well as in those with different MI locations. There were no significant differences between the groups in the summed HF-QRS of all 12 leads or in the pattern of lead distribution of the HF-QRS. Not even the patients with the greatest QRS changes of old MI could be differentiated from those without any changes of old MI on the standard ECG. The results were the same in both analyzed frequency bands. CONCLUSIONS: This study shows, contrary to previous studies, that analysis of HF-QRS cannot differentiate between patients with and without old MI.

Standards for the function of an academic 12-lead electrocardiographic core laboratory.

An academic 12-lead electrocardiogram (ECG) core laboratory aims to provide the highest possible quality ECG recording, measurement, and storage to aid clinicians in research into important cardiovascular outcomes and to maximize the credibility of scientific results based solely, or in part, on ECG data. This position paper presents a guide for the structure and function of an academic ECG core laboratory. The key functional aspects are: 1) Data collection, 2) Staff composition, 3) Diagnostic measurement and definition standards, 4) Data management, 5) Academic considerations, 6) Economic consideration, and 7) Accreditation. An ECG Core Laboratory has the responsibility for rapid and accurate analysis and responsible management of the electrocardiographic data in multicenter clinical trials. Academic Laboratories, in addition, provide leadership in research protocol generation and production of research manuscripts for submission to the appropriate peer-review journals.

Changes in high-frequency QRS components are more sensitive than ST-segment deviation for detecting acute coronary artery occlusion.

OBJECTIVES: This study describes changes in high-frequency QRS components (HF-QRS) during percutaneous transluminal coronary angioplasty (PTCA) and compares the ability of these changes in HF-QRS and ST-segment deviation in the standard 12-lead electrocardiogram (ECG) to detect acute coronary artery occlusion. BACKGROUND: Previous studies have shown decreased HF-QRS in the frequency range of 150-250 Hz during acute myocardial ischemia. It would be important to know whether the high-frequency analysis could add information to that available from the ST segments in the standard ECG. METHODS: The study population consisted of 52 patients undergoing prolonged balloon occlusion during PTCA. Signal-averaged electrocardiograms (SAECG) were recorded prior to and during the balloon inflation. The HF-QRS were determined within a bandwidth of 150-250 Hz in the preinflation and inflation SAECGs. The ST-segment deviation during inflation was determined in the standard frequency range. RESULTS: The sensitivity for detecting acute coronary artery occlusion was 88% using the high-frequency method. In 71% of the patients there was ST elevation during inflation. If both ST elevation and depression were considered, the sensitivity was 79%. The sensitivity was significantly higher using the high-frequency method, p<0.002, compared with the assessment of ST elevation. CONCLUSIONS: Acute coronary artery occlusion is detected with higher sensitivity using high-frequency QRS analysis compared with conventional assessment of ST segments. This result suggests that analysis of HF-QRS could provide an adjunctive tool with high sensitivity for detecting acute myocardial ischemia.

Spatial, individual, and temporal variation of the high-frequency QRS amplitudes in the 12 standard electrocardiographic leads.

BACKGROUND: Analysis of high-frequency QRS amplitudes (HF-QRS) may provide an additional diagnostic tool in patients with heart disease, but the basic properties of these waveforms have not been sufficiently investigated. This study describes the spatial, individual, and temporal variation at rest of HF-QRS recorded with the 12 standard electrocardiographic leads in patients with ischemic heart disease. METHODS AND RESULTS: Two consecutive electrocardiographic recordings from 67 patients were signal averaged and analyzed within a bandwidth of 150 to 250 Hz. The HF-QRS values were expressed as root mean square values. There was a spatial variation in HF-QRS among the 12 leads, with higher amplitudes in V(2) through V(4), II, aVF, and III. The individual variation among the patients was large for all leads. The sum of the HF-QRS for all 12 leads in each patient ranged from 20 to 75 microV (mean 36 +/- 11 microV). The mean of the temporal variation in HF-QRS for all 12 leads between the 2 recordings was only 0.10 +/- 0. 09 microV. CONCLUSIONS: Because of the large individual variation, analysis of HF-QRS is probably most applicable in monitoring situations when it is possible to track changes in a patient over time. The temporal variation in HF-QRS at rest is small, both in patients with and those without prior myocardial infarction.

Moving toward a new definition of acute myocardial infarction for the 21st century: status of the ESC/ACC consensus conference. European Society of Cardiology and American College of Cardiology.

The European Society of Cardiology and American College of Cardiology established their initial Joint Consensus Conference in July 1999 to develop a new definition of Acute Myocardial Infarction. This action was deemed necessary because of the development of new sensitive biochemical markers of myocardial necroses: Troponins T and I. There were 5 working groups, including one in Electrocardiography. The Conference adopted a definition that required only a history of "ischemic symptoms" and "a typical rise and fall" of at least one of the biochemical markers. The ECG Working Group strongly advised that a term distinctive from "myocardial infarction" such as "myocardial necrosette" be adopted as the diagnosis for an acute coronary event during which the peak biochemical marker level is below that which occurs when serial evolutionary ECG changes are observed. A pilot substudy from the GUSTO IIa Clinical Trial has identified the low end of the "ECG Change Range" to be: >2x the upper limit of normal for CK-MB, > 11 x for Troponin T, and >6 x for Troponin I.

The correlation between presenting ST-segment depression and the final size of acute myocardial infarcts in patients with acute coronary syndromes.

The use of reperfusion therapy in patients with ST elevation acute coronary syndromes had been established. However, reperfusion therapy is usually considered contra-indicated in those with ST depression, despite the knowledge that regional posterior infarction is typically indicated by ST depression maximal in leads V1 to V3 and nonregional subendocardial infarction is typically indicated by marked ST depression maximal in other leads. This study of patients with non-ST-elevation acute coronary syndromes investigates the quantitative relationship between presenting ST depression and final QRS changes in both of these subgroups. The final QRS score was significantly higher (2.44 points) than that of a control group with not ST depression, (1.55 points) in the group with maximal ST depression in V1 to V3 (P = 0.04). However, in the entire population, there was a highly significant correlation (P = .003) between the sum of the presenting ST depression and the final QRS score. Trials of reperfusion therapy will be required to determine if such evolution to electrocardiogram documented acute myocardial infarction can be prevented in patient with marked ST depression acute coronary syndromes.

Clinical implication of down-scatter in attenuation-corrected myocardial SPECT.

BACKGROUND: Interpretation of myocardial perfusion single photon emission computed tomography (SPECT) studies is hampered by attenuation artifacts. Attenuation correction methods with simultaneous emission and transmission are now commercially available. However, it has been observed in clinical practice that attenuation correction without down-scatter correction in a 1-day rest/stress myocardial perfusion protocol may lead to serious interpretation errors. Therefore the aim of this study was to study errors resulting from down-scatter under realistic conditions, thus providing a background for the assessment of further corrections. METHODS AND RESULTS: Forty-six patients underwent myocardial perfusion scintigraphy in a 1-day technetium 99m-tetrofosmin rest-stress SPECT protocol, with a moving 153Gd line-source device for attenuation correction without down-scatter correction. Short-axis slices were quantified as inferior/anterior, septal/lateral, and apical/remainder count ratios. The changes at rest (350 MBq) and exercise (900 MBq) induced by attenuation correction were studied. Attenuation correction gave differences in apparent perfusion between rest and exercise not seen before correction. The gender differences in inferior-anterior ratio were greatly reduced after correction at rest but remained at exercise. A torso phantom study indicated that these results were due to under-correction at exercise because of down-scatter. CONCLUSIONS: Down-scatter results in an underestimation of attenuation in simultaneous emission and transmission, if not accurately accounted for. Particularly, a high-dose study compared with a low-dose study, as in the 1-day protocol, might cause serious interpretation errors.

Left-to-right cardiac shunts: comparison of measurements obtained with MR velocity mapping and with radionuclide angiography.

PURPOSE: To investigate the agreement between two noninvasive methods, magnetic resonance (MR) velocity mapping and first-pass radionuclide angiography, to quantify the pulmonary-to-systemic blood flow ratio (QP/QS) in adults, adolescents, and children with left-to-right cardiac shunts. MATERIALS AND METHODS: The accuracy and precision of MR velocity mapping were studied in 12 control subjects (six men, six women) and in a phantom. MR velocity mapping and radionuclide angiography were performed on the same day in 24 patients (16 adults, two adolescents, six children; five male patients, 19 female patients). RESULTS: The mean error in QP/QS at MR velocity mapping in phantom experiments was -1% +/- 1 (mean +/- SD). In control subjects, QP/QS at MR velocity mapping was 1.03 +/- 0.03, and the cardiac index was 3.1 L/min/m2 +/- 0.2 and 3.2 L/min/m2 +/- 0.3 for women and men, respectively. In patients, QP/QS at radionuclide angiography was 14% +/- 13, higher than at MR velocity mapping. Interobserver variability was four times higher for radionuclide angiography compared with MR velocity mapping, 0% + 16 versus 0% +/- 4 (n = 12). The difference between repeated MR flow measurements in the same vessel was -1% +/- 5 (n = 36). CONCLUSION: The data suggest that MR velocity mapping is accurate and precise for measurements of shunt size over the whole range of possible QP/QS values.

Combined historical and electrocardiographic timing of acute anterior and inferior myocardial infarcts for prediction of reperfusion achievable size limitation.

The historical time of acute symptom onset is not always an accurate indication of the timing of onset of an acute myocardial infarction (AMI). Consideration of electrocardiographic (ECG) timing parameters could supplement historical timing alone as a clinical guide for decisions regarding the use of reperfusion therapy. Three hundred ninety-five patients from 4 trials of thrombolytic therapy conducted in the northwestern United States and western Canada are included in the present study. A total of 316 patients received either streptokinase or tissue plasminogen activator, and 79 received no reperfusion therapy. Historical time of symptom onset was acquired by emergency or cardiology department personnel and recorded on patient report forms. An ECG method for estimating the timing of the AMI, the Anderson-Wilkins (AW) acuteness score, was calculated from the initial standard 12-lead recording by investigators blinded to the knowledge of symptom duration or any other study variables. Tomographic thallium-201 imaging 7 weeks after hospital admission was used to measure final AMI size. The ECG timing method achieved a relation with final AMI size similar to that previously reported for historical timing. The AW acuteness score proved most useful for anterior AMI location when there was a > or = 2 hour delay following symptom onset, but was most useful for the inferior AMI location when there was a < 2 hour delay. Despite a longer delay, patients with high AW acuteness scores had 50% lower final anterior AMI size than those with low scores; and despite a shorter delay, those with low ECG acuteness scores had 50% greater final inferior AMI size than those with high scores. The AW acuteness score combined with the historical estimation of symptom duration should provide a more accurate basis for predicting the potential for limitation of final AMI size than either method alone. These results could potentially provide the basis for developing a new method for noninvasive guidance of clinical decisions regarding administration of reperfusion therapy in the initial evaluation of patients with AMI.

No serious late cardiac effects after adjuvant radiotherapy following mastectomy in premenopausal women with early breast cancer.

PURPOSE: To assess cardiac mortality, coronary artery disease, myocardial dysfunction, and valvular heart disease in women younger than 65 years of age, at least 10 years after adjuvant radiotherapy following mastectomy in early breast cancer. METHODS AND MATERIALS: Ninety women (45-64 years old) with Stage II breast cancer without relapse, included in the South Sweden Breast Cancer Trial (premenopausal arm), with or without adjuvant postoperative radiotherapy +/- cyclophosphamide were examined with myocardial scintigraphy and echocardiography/Doppler, 10-17 years after radiotherapy. Thirty-four patients had been irradiated for left-sided tumors, 33 for right-sided tumors, and 23 patients had not been treated with radiotherapy. The radiotherapy (conventional roentgen, electron beams, and high-energy photon beams combined, in each patient) included the chest wall and the regional lymph nodes, with a specified target dose of 38-48 Gy, administered in daily fractions of 1.9-2.4 Gy, 5 days/week. RESULTS: No cardiac deaths were found among the original 275 patients randomized to adjuvant therapy. In the 90 patients examined, abnormal findings were recorded for ECG (14 patients), exercise test (5 patients), myocardial scintigraphy (6 patients), thickening of valve cusps (14 patients), and mild valvular regurgitation (20 patients). All patients had normal systolic function. Diastolic dysfunction was observed in 6 patients (abnormal relaxation in 4 patients and restrictive filling abnormality in 2 patients). Although no significant differences were found between the 3 study groups, there was a tendency to more abnormal findings after radiotherapy. CONCLUSION: Women younger than 50 years of age at the time of adjuvant radiotherapy following mastectomy in early breast cancer, had no serious cardiac sequelae 13 years (median) later, despite partly old-fashioned radiation techniques.

Beat-to-beat QRS variability in the 12-lead ECG and the detection of coronary artery disease.

The aim of this article was to study beat-to-beat QRS variability in patients with ischemia and old myocardial infarction using the 12-lead resting electrocardiogram (ECG). The variability analysis was based on beats that have been synchronized in time with an iterative alignment technique. The QRS variability was measured in patients submitted for myocardial scintigraphy. Those with a normal myocardial scintigraphy (called NO, n = 34, mean age 57 years, 23 women) were compared with a group with both myocardial infarction and exercise-induced ischemia (called ISCINF, n = 27, mean age 57 years, 5 women). The mean QRS variability was somewhat smaller in lead I in ISCINF than in NO, and there was no statistically significant difference in QRS variability among the groups in leads II, III, and V1-V6. Using a multivariate approach, the joint variability in leads I, II, II, and V1-V6 was used for calculating receiver operating characteristics based on a leave-one-out procedure. The sensitivity for detecting coronary artery disease was 75% at a specificity of 50%. It is concluded that beat-to-beat QRS variability in the 12-lead ECG does not discriminate between the presence and absence of coronary artery disease sufficiently well for clinical purposes.

Electrocardiographic changes during prolonged coronary artery occlusion in man: comparison of standard and high-frequency recordings.

Detection of acute myocardial ischaemia using electrocardiographic methods is generally based on assessment of the ST segments in the standard 12-lead electrocardiogram (ECG). Several studies have also shown changes in high-frequency QRS components during acute ischaemia. The purpose of the present study was to determine the changes in high-frequency QRS components during prolonged percutaneous transluminal coronary angioplasty (PTCA) and to compare these changes with ST-segment deviations in the standard 12-lead ECG. The study population consisted of 19 patients receiving prolonged PTCA. Standard and high-resolution signal-averaged ECGs were recorded before and during balloon inflation. The high-resolution recordings were performed using bipolar X, Y and Z leads. The QRS complexes in the high-resolution signal-averaged ECGs were analysed within a bandwidth of 150-250 Hz. During inflation, significant reductions in high-frequency QRS components were observed (12-72%). Changes in the high-frequency QRS components were seen in four of the patients without ST-segments deviation in the standard ECG. The correlation between the ST-segment deviation and the reduction in high-frequency QRS components was weak (r = 0.27). Acute coronary artery occlusion produces changes in high-frequency QRS components, even in the absence of ST-segment deviation in the standard ECG. Further studies need to be carried out to evaluate whether analysis of high-frequency QRS components could provide a method for detecting myocardial ischaemia and give additional information to that available in the ST segment in the standard ECG.

The association between diabetic nephropathy and autonomic nerve function in type 1 diabetic patients.

Diabetic cardiovascular autonomic neuropathy increases the risk of deterioration in renal function and is associated with increased mortality in patients with renal failure. Type 1 diabetic patients with long diabetes duration, matched for age (38 +/- 9 years) and diabetes duration (28 +/- 8 years) were studied regarding the association between cardiovascular autonomic nerve function and different degrees of diabetic nephropathy. Eighteen patients were normo- (< 30 mg/l), six micro- (30-300 mg/l), and 13 macroalbuminuric (> 300 mg/l) based on urinary albumin concentrations in three separate morning samples. They were compared with 33 control subjects with similar age. Autonomic nerve function was evaluated by measuring the response of heart rate to deep breathing and active standing. Beat-to-beat finger artery blood pressure (Finapres) was tested during active standing. During deep breathing both change in heart rate (17 +/- 11, 9 +/- 7 and 4 +/- 3 beats/min) and ratio between expiratory and inspiratory R-R intervals (1.32 +/- 0.24, 1.14 +/- 0.15 and 1.05 +/- 0.04) decreased from normo- over micro- to macroalbuminuria (p < 0.05 vs normoalbuminuric and control subjects [17 +/- 5 beats/min and 1.28 +/- 0.10, respectively]). Similar results were obtained during active standing with respect to change in systolic arterial blood pressure (3 +/- 8, 2 +/- 13 and -6 +/- 11 mmHg; p < 0.05 vs control subjects [8 +/- 11 mmHg]). However, the response of diastolic arterial blood pressure or mean heart rate to standing up did not differ between any of the groups. The ratio of maximum to minimum R-R interval during the dynamic response of heart rate to active standing decreased with the degree of nephropathy (1.27 +/- 0.17, 1.11 +/- 0.11 and 1.05 +/- 0.06) with significantly higher values in patients with normo- compared with patients with macroalbuminuria (p < 0.05). All patients groups had significantly lower values than control subjects (1.46 +/- 0.22, p < 0.05). The overshoot of the blood pressure after an initial fall during active standing decreased with the degree of diabetic nephropathy. In conclusion, type 1 diabetic patients with long duration of diabetes have signs of cardiovascular autonomic neuropathy, the severity of which is related to the degree of nephropathy.

Increased prevalence of large bites in 12-lead vectorcardiograms of diabetic patients.

The vectorcardiographic (VCG) bites in diabetic patients were compared with those in nondiabetic control subjects using automated analysis of the conventional electrocardiogram (ECG). A 12-lead ECG was recorded from each of the 154 patients with non-insulin-dependent diabetes mellitus and 128 control subjects. The orthogonal leads X, Y, and Z were derived from the 12-lead ECG, from which a so-called 12-lead VCG was calculated for each of the 282 participants. A computer-based method for the detection and quantification of bites was applied to the 12-lead VCGs. Bite amplitudes in the horizontal loop had an average of 0.062 +/- 0.089 mV in the diabetic group, and 0.039 +/- 0.045 mV in the control group (P < .01). In the sagittal plane, the mean bite amplitude was also greater in the diabetic group than in the control group: 0.095 +/- 0.084 versus 0.069 +/- 0.058 mV, respectively (P < .01). A bite greater than 0.1 mV in the horizontal or sagittal planes was found in 56 diabetic patients (36%) and 27 control subjects (21%) with (P < .05) considered significant. In conclusion, the results of this study suggest that automated analysis of the 12-lead VCG can be valuable in diagnosing diabetic cardiomyopathy.