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PubMed1994

Maximal spatial ST-vector patterns in patients with acute anteroseptal myocardial infarction.

Seventy patients with acute myocardial infarction were studied by serial vectorcardiography. Eleven out of 70 patients had acute myocardial infarction, which consistently met the vectorcardiographic QRS-loop criteria of anteroseptal myocardial infarction within the 21 days follow-up period. From the first vectorcardiographic tracings three types of the maximal spatial ST-vector were seen. Their directions belonged to one of the following octants: (1) right-anterior-superior, (2) left-anterior-superior, or (3) left-anterior-inferior. The directions were the same as the types of initial activity of the normal depolarization process of the interventricular septum revealed by the intracardiac mapping in dogs. The subsequent vectorcardiograms showed no change in direction of the maximal spatial ST-vector in all patients except one. This study suggested that there are three types of the maximal spatial ST-vector concealed in patients with first acute anteroseptal myocardial infarction. Each type of the maximal spatial ST-vectors is capable of causing S-T segment elevation from leads V1 to V3 in the acute electrocardiogram. Why the subgroup of the right-anterior-superior maximal spatial ST-vector in patients with acute anteroseptal myocardial infarction had poor outcomes during the acute stage needs further investigation.

Aged↗

PubMedDate not supplied

Electrocardiomultigraphimeter using a home computer.

The drop in hardware costs has fostered the widespread use of home-computer systems. Because of this situation, the home computer can be profitably employed in some highly specialized fields. We believe electrocardiographic instrumentation to be one such field. We have built an electrocardiomultigraphimeter (ECXGM), which can be considered as a development of the traditional electrocardiograph that performs some additional functions. Our prototype features vectorcardiography, polar coordinate tracing, automatic measurements between fiducial points selected by the user with a joystick and screen cursor and trace filing by patient on labelled floppy disks. The standard hardware consists of a Commodore 64 console, a monitor, two floppy disk drives and an Epson HI-80 plotter, all of which are readily available. The special hardware consists of an A/D converter, which receives the electrocardiographic signal downstream of the amplifying stage, which is a standard feature of any electrocardiograph. Prototype development mostly involved the software. Difficulties were posed by the limited resources available on home computers, an important point in view of the problem to be tackled. The solutions adopted are based on the use of assembler language and overloading techniques and minimizing the interconnections among the software modules defined in a compactly built program. The result is an instrument with significantly advanced clinico-scientific capabilities as compared to current electrocardiographic instruments. This fact, and the class of the hardware used and special software built, confer originality to this work. The new instrument ought to be especially suitable for the offices of cardiologists who have an interest in such capabilities, and for schools of electrocardiography.

Computer Graphics↗

PubMed1981

Dynamic electrocardiography. III. The "imaginary cardiac vector" hypothesis: theoretical basis.

The "imaginary cardiac vector" hypothesis states that the "cardiac vector" is not a "real" vector entity. The hypothesis arises from the fact that voltage is not a vector but a scalar quantity. Nevertheless, in classical electrocardiographic analysis and teaching, the ECG voltage is treated as a vector. These voltages are used as "vector" components--first, to calculate a "resultant manifest potential difference", represented by the "cardiac vector" arrow in electrocardiography, and second, to draw the "cardiac vector" loop in vectorcardiography. The resultant "cardiac vector" is usually considered to be a "real" vector quantity describing the electrical activity of the heart. It is also widely believed that this "vector" was first described by Einthoven in 1913. To evaluate the hypothesis, we have utilised the actual values and methods presented by Einthoven, and demonstrated that the theoretical basis of the "cardiac vector" is false. It appears that Einthoven followed scalar and not vector procedures and that he did not describe a vector.

Electrocardiography↗

PubMed2004

T vector and loop characteristics in coronary artery disease and during acute ischemia.

OBJECTIVE: Three-dimensional characterization of the ventricular repolarization by the T vector and T vector loop morphology in coronary artery disease (CAD), and their response to short-term (no flow) ischemia induced by coronary occlusion during a percutaneous intervention (PCI). BACKGROUND: The risk for sudden cardiac death is increased in conditions of acute or permanently heterogeneous ventricular repolarization, for which ischemia is a risk factor. METHODS: Fifty-six CAD patients without visible collateral circulation were studied during an elective single-vessel PCI, and 10 healthy controls twice at rest. T vector parameters (Televation, Tazimuth, and QRS-T angle), and T loop parameters (Tarea, Tavplan, and Teigenv) were measured by vectorcardiography. ST vector magnitude (ST-VM) and its change (STC-VM) were used for reference. RESULTS: At rest, T vector loop morphology (Tarea, Teigenv) was significantly different in CAD patients and controls, while T vector angles did not separate the groups. Ischemia induced significant changes in T loop parameters in the entire CAD group, whereas in the LAD subgroup significant changes were seen also in T vector angle. The T loop morphology was significantly different at baseline and a more pronounced response to ischemia (Tarea) was seen in patients with, than in those without, a history of hypertension. CONCLUSION: T loop morphology, rather than the T vector angle, separated CAD patients from healthy controls. Coronary occlusion had significant impact on ventricular repolarization, as assessed by T vector and morphology analysis, and most prominently in the LAD group. Hypertensive patients appeared especially vulnerable to ischemia.

Acute Disease↗

PubMed2005

Temporal characteristics of cardiac memory in humans: vectorcardiographic quantification in a model of cardiac pacing.

OBJECTIVES: The purpose of this study was to assess the temporal characteristics of cardiac memory in a human pacing model. BACKGROUND: Cardiac memory is induced by periods of altered ventricular activation and in the canine pacing model develops in 2 to 3 weeks. METHODS: Cardiac memory development (phase 1) and resolution (phase 2) was followed qualitatively (ECG) and quantitatively (vectorcardiography [VCG]) in 20 patients with symptomatic sinus bradycardia receiving DDD-R pacing at physiologic rates. During phase 1, maximum ventricular pacing in the right ventricular apical endocardium was achieved by short AV delay. ECG and VCG were recorded during normal ventricular activation prior to implantation (sinus rhythm), 1 day after and then weekly for 5 to 8 weeks during AAI pacing (n = 14, "long-term"), and daily during 1 week (n = 6, "short-term"). In phase 2, the remaining cardiac memory was related to the amount of ventricular pacing. A long AV delay was chosen to reduce ventricular pacing, and 14 patients were seen once after 4 to 5 weeks. RESULTS: ECG and VCG showed marked changes in all patients within 1 week's pacing and remained stable during phase 1. Of the 14 long-term patients, 13 showed significant change in T vector azimuth (mean -150 degrees ) and 11 in T vector elevation (mean 63 degrees ). At the end of phase 2, a linear relation existed between remaining cardiac memory (%) and amount (%) of delivered ventricular pacing. CONCLUSIONS: Cardiac memory developed and reached steady state within 1 week of right ventricular endocardial pacing at physiologic rates in man, was preserved in proportion to delivered ventricular pacing, and completely resolved within 1 month in its absence.

Adult↗

PubMed1977

Echocardiographic evaluation of septal motion in patients with artificial pacemakers: vectorcardiographic correlations.

Twenty-one patients with transvenous endocardial right ventricular pacemakers and one patient with epicardial right ventricular pacemaker inducing artificial left bundle branch block (LBBB) were studied with echocardiographic and vectorcardiographic techniques. Sixteen patients were found to have an initial very active posterior motion of the interventricular septum occurring within 70 msec. (range, 40 to 100 msec.) of the pacemaker artefact followed by posterior movement during the ejection period (Pattern A). Eighteen of 20 patients with clinical LBBB serving as a control group showed a dynamic posterior motion occurring within 40 msec. of the onset of QRS and preceding anterior (paradoxical) motion of the septum during ejection. In four patients, following the initial brief posterior septal movement, there was flat or anterior movement of the septum during the ejection period (Patern B). Two patients had myocardial infarction and one had atrial septal defect and epicardial right ventricular pacemaker. Only in two patients the initial brief posterior septal motion was not recorded before moving posteriorly during the ejection period (Pattern C). The different patterns of septal motion found in patients with artificial LBBB and in those with natural LBBB could be explained by differences in activation of the heart, as shown by vectorcardiography. Echocardiographic septal evaluation of patients with artificial pacemakers could have diagnostic implications in suggesting possible underlying complicating cardiac abnormalities.

Adult↗

PubMed1977

Electrocardiographic and vectorcardiographic abnormalities in Fabry's disease.

Fabry's disease has been reported to be associated with ECG abnormalities. Thirty-two patients with this disease followed in the University of Minnesota had ECG's and 15 had VCG's. An abonrmal rhythm was observed in two patients on initial examination and four more developed abnormal rhythm on follow-up examinations. A short PR interval (120 msec. or less) was seen in five patients. Thirteen others had a PR interval that was less than 140 msec. Conduction abnormalities involving the A-V node or His bundle or its branches were present in 22 per cent of the patients, most frequently the intraventricular conduction defects progressing to the right bundle branch block. Atrial or ventricular enlargement was seen in 60 per cent of the patients, left ventricular hypertrophy being the most common. ST-T changes with or without chamber enlargement were seen in 10 patients. One patient had an anterior myocardial infarction pattern on his ECG. Hemizygosity was found to be associated with significantly more abnormalities than heterozygosity. The severity of conduction defects also increased with the duration of the disease process. Vectorcardiography in this study did not provide significant additional information other than that observed on the ECG alone. Since the pathology usually reveals myocardial fibers, conduction system, and blood vessels infiltrated with glycosphingolipid, it is believed that lipid infiltration is responsible for conduction defects, chanber enlargement, and other abnormalities. Although Fabry's disease is rate, it may be amenable to therapy; therefore, recognition of cardiac involvement is important.

Adolescent↗

PubMed1976

Correlation of electrocardiogram and vectorcardiogram with coronary occlusion and myocardial contraction abnormality.

Electrocardiograms and Frank vectorcardiograms were recorded in 156 consecutive patients with total occlusion of at least one coronary artery (on arteriography) and associated left ventricular contraction abnormality (on ventriculography). The angiograms and cardiograms were independently reviewed. In the presence of single vessel occlusion, appropriate vectorcardiographic diagnosis of myocardial infarction was determined in 118 of 156 cases (76 percent) compared with a lower electrocardiographic detection rate in 77 of 156 cases (49 percent). Findings diagnostic of two coexisting infarctions were observed in 71 percent of vectorcardiograms and 37 percent of electrocardiograms in 51 patients with double vessel occlusion and two areas of left ventricular dyskinesia. The vectorcardiographic detection rate was similarly superior to the electrocardiographic rate in the presence of subtotal coronary occlusion and myocardial asynergy in single (73 percent versus 53 percent) and double (53 percent versus 28 percent) vessel disease. The incidence rate of false positive diagnoses was 3 percent for electrocardiography and 4 percent for vectorcardiography. It is concluded that the vectorcardiogram is superior to the electrocardiogram in the diagnosis of obstructive coronary artery disease and left ventricular contraction abnormality.

Adult↗

PubMed1984

Estimation of inferobasal myocardial infarct size by late activation abnormalities of the QRS complex.

This report describes the relation of myocardial infarct (MI) size in the left ventricular inferobasal wall, measured at necropsy, to late activation abnormalities of the QRS complex, measured by computerized spatial vectorcardiography. Fifteen patients with single inferobasal MIs and 10 patients with no evidence of heart disease were studied. The percentage of MI in the inferobasal wall was significantly related to the vectorcardiographic abnormalities noted late (i.e., 31 +/- 13 ms before the end of the QRS waveform) (r = 0.96, p less than 0.00001). The integral of the vector magnitudes during late abnormal activation significantly predicted the amount of MI in the basal inferior wall (r = 0.88) and in the basal inferior wall plus the outer, subepicardial half of the transmural middle inferior, lateral and inferoseptal walls (r = 0.91). The additional information obtained from late activation of the QRS complex contributed more significance to the estimation of the left ventricular inferobasal MI size than the abnormalities commonly noted during early activation (i.e., during the Q wave).

Aged↗

PubMed1984

Reduction of infarct size by the early use of intravenous timolol in acute myocardial infarction. International Collaborative Study Group.

One hundred forty-four patients admitted to the hospital within 4 hours after the onset of symptoms of suspected acute myocardial infarction (AMI) were randomly assigned to either intravenous timolol treatment or to matching placebo. Infarct evolution was assessed by continuous vectorcardiography and CK release. Timolol reduced myocardial ischemia and infarct size as measured by an accelerated reduction in ST-vector magnitude, a significant reduction in maximal cumulative CK release (29.5%) and significantly smaller changes in QRS-vector parameters (20 to 25%). Furthermore, the predicted CK release and maximal QRS-vector change for a given initial ST-vector magnitude was significantly reduced by timolol. The drug regimen also caused a significant reduction in pain and the need for analgesic medication.

Administration, Oral↗

PubMed1999

Relative contributions of a single-admission 12-lead electrocardiogram and early 24-hour continuous electrocardiographic monitoring for early risk stratification in patients with unstable coronary artery disease.

Patients with unstable coronary syndromes are a heterogeneous group with varying degrees of ischemia and prognosis. The present study compares the prognostic value of a standard electrocardiogram (ECG) obtained at admission to the hospital with the information from 24-hour continuous electrocardiographic monitoring obtained immediately after admission. The admission ECGs and 24 hours of vectorcardiographic (VCG) monitoring from 308 patients admitted with unstable coronary artery disease were analyzed centrally regarding standard electrocardiographic ST-T changes, ST-vector magnitude (ST-VM), and ST change vector magnitude episodes. End points were death, acute myocardial infarction, and refractory angina pectoris within a 30-day follow-up period. ST-VM episodes (> or = 50 microV for > or = 1 minute) during VCG monitoring was the only independent predictor of death or acute myocardial infarction by multivariate analysis. ST-VM episodes during vectorcardiography was associated with a relative risk of 12.7 for having a cardiac event, hypertension was associated with a relative risk of 1.7, and ST depression on the admission ECG was associated with a relative risk of 5.7. Patients with ST depression at admission had an event rate (death or acute myocardial infarction) of 17% at 30-day follow-up. Patients without ST depression could further be risk stratified by 24 hours of VCG monitoring into a subgroup with ST-VM episodes at similar (8%) risk and a subgroup without ST-VM episodes at low (1%) risk (p = 0.00005). Continuous VCG monitoring provides important information for evaluating patients with unstable coronary artery disease. It is recommended that patients not initially estimated at high risk based on the admission ECG are referred for 24 hours of VCG monitoring for further risk stratification.

Aged↗

PubMed1975

Relation of left ventricular contractile patterns in coronary artery disease to the electrocardiogram and vectorcardiogram.

Two hundred thirty patients with coronary artery disease (CAD) were studied with left ventriculography, coronary arteriography, electrocardiography (ECG) and vectorcardiography (VCG) to determine how well left ventricular (LV) contractile defects could be predicted from the ECG-VCG patterns and how this was related to the coronary disease location and severity. Of 124 patients with infarction patterns on ECG-VCG about 50% had LV contractile defects localized to the corresponding ECG-VCG abnormalities, i.e., antero-apical asynergy with anterior infarction patterns, inferior asynergy with inferior infarction patterns, or antero-apical plus inferior asynergy with anterior plus inferior patterns. About 20% in each infarction group had unexpected synergy on ventriculography except for patients with dorsal infarction patterns (synergy in 68%) who are discussed as a special problem. Another 25-30% of patients had more extensive contractile abnormality than indicated by the ECG-VCG patterns. In 106 patients with left ventricular hypertrophy, normal QRS-abnormal T and normal QRS-T on ECG-VCG, 65-70% had synergy. However, 30-35% had asynergy in various combinations not suspected from the ECG or VCG. Coronary artery disease severity was less pronounced in patients with synergy than with asynergy and single vessel disease was more common in the former, 47% versus 18-30% in the latter. However, coronary artery disease severity was the same for all ECG-VCG groups except for anterior plus inferior infarction patterns where it was most severe.

Coronary Disease↗

PubMed1975

Quantative analysis of the vectorcardiogram in obesity. The effects of weight reduction.

Vectorcardiograms (VCG) recorded in 37 subjects with marked chronic EXOGENOUS OBESITY (AVERAGE WEIGHT: 285 LBS.) WERE COMPARED before and after a significant weight reduction (average weight loss: 86 lbs). They were also compared with the VCGs of 293 age and sex matched controls with normal body weight. The SVEC III corrected orthogonal lead system was used, and out of several hundred vectorcardiographic measurements obtained by computer processing, 59 measurements representing various scalar, planar and spatial voltage and angular measurements were selected for study and comparisons. No significant differences were found between the measurements of obese subjects and those of the controls. Of 59 VCG measurements, 13 showed significant differences after weight reduction (paired t test) although they remained within the range of normal controls. There was a trend toward decrease of P and QRS amplitudes after weight reduction. There were no significant changes in the angular measurements. Although they are statistically significant these changes in voltage are too small to be detected in clinical vectorcardiography. The possible decrease of a preexisting myocardial hypertrophy superimposed onto the changes in the anatomy of the thorax might explain the effects of weight reduction. In general the reproducibility of VCG measurements obtained by the SVEC III system was greater than that reported in day-to-day operation with the Frank system in normal subjects.

Adipose Tissue↗

PubMed1978

Vectorcardiographic identification of myocardial scar: a discriminative study with automatically processed vectorcardiographic information.

A multivariate discriminative procedure for the vectorcardiographic identification of ischemic myocardial scarring was performed utilizing data from 1,162 vectorcardiograms (VCGs) obtained in clinically normal subjects and 90 VCGs obtained from patients proved at autopsy to have ischemic myocardial scars. The VCGs from patients with myocardial scars were divided into two groups, a design group of 50 cases and an evaluation group of 40 cases. The best vectorcardiographic variables to discriminate the clinically normal group from the design group with scars were identified by stepwise linear discrimination. Sixteen vectorcardiographic variables were then used for discriminative analysis. This analysis correctly identified myocardial scars in 45 of the 50 VCGs in the design group (sensitivity 90%); among the 1,162 VCGs from clinically normal subjects, 32 were misidentified as myocardial scar (specificity 97.2). The sensitivity of these defining criteria was then tested in the 40 cases of myocardial scar in the evaluation group and found to be reproducible; 34 of the 40 cases of this group (85.0%) were correctly identified as having a myocardial scar. The multivariate discriminative criteria developed in this study had greater sensitivity and specificity than standard methods usually employed in electrocardiography and vectorcardiography. The criteria defined need to be evaluated in a large series that includes instances of cardiac pathology of nonischemic nature.

Adolescent↗

PubMed1979

Electrocardiographic poor R wave progression. I: correlation with the Frank vectorcardiogram.

Fifty-six patients with "poor R wave progression" (PRWP) on the electrocardiogram (ECG) were studied by Frank vectorcardiography in an attempt to define discriminators for subgroups. Criteria were prospectively applied to a test group with achievement of comparable sensitivity and specificity. Four subgroups were identified in the patients with PRWP: Group I - anterior myocardial infarction (AMI) (20/56, 35%); Group II - left ventricular hypertrophy (LVH) (8/56, 14%); Group III - right ventricular hypertrophy (RVH) (7/56, 13%); AND Group IV - leftward axis (LA) (21/56, 38%). The best discriminator for vectorcardiogram (VCG) AMI was RV3 less than or equal to 1.5mm or R1 less than or equal to 4.0mm (18/20, 90% sensitivity; 26/36, 72% specificity). RVH and LVH were identified by R1 less than or equal to 4.0mm and S1 greater than or equal to 1.0mm and standard LVH voltage criteria respectively. Group IV patients (PRWP without VCG criteria for AMI, LVH or RVH) were identified by exclusion. "Reversed R wave progression" (RRWP) was more specific for AMI than was simple PRWP. The same discriminators, however, were applicable. It is clinically useful to note that 72% (26/36) of patients with either PRWP or RRWP who did not exhibit VCG AMI could be identified by 12 lead ECG with only 2/28 (7%) VCG false negative AMI.

Adult↗

PubMed1984

Vectorcardiographic features of acute right ventricular infarction.

A total of seven patients with acute inferior or inferior-posterior transmural myocardial infarction who had cardiac scintigraphically confirmed right ventricular (RV) involvement was studied. Series of vectorcardiographic tracings were taken using the Frank lead reference system from the second day after onset of acute symptoms; we found that in patients with acute inferior and RV infarction, the magnitude of the planar ST vector was greater than or equal to 0.15 mV and the projection of the ST vector pointed either to the right-anterior or right-posterior direction in the horizontal (H) plane. The serial spatial ST vector changed its direction either: 1) from right-anterior-inferior octant to right-posterior-inferior octant or vice versa; or 2) from right-posterior-inferior octant to right-anterior-superior octant. The larger the magnitude of the rightward ST vector, especially right-anterior direction in the H plane, the greater the probability of acute RV infarction. In patients with acute inferior-posterior and RV infarction, the magnitude of the ST vector in the H plane was greater than or equal to 0.2 mV. The spatial ST vector pointed to the right-posterior-inferior octant and its direction did not change from the original octant in the serial tracings during the course of the acute stage. Our data suggest that vectorcardiography--a non-invasive, non-nuclear polluting, and economical method--has shown great potential to become, in the near future, the primary non-invasive diagnostic test of choice for acute RV infarction.

Adult↗

PubMed1994

ECG changes during myocardial ischemia. Differences between men and women.

Women have a higher short-term mortality in acute myocardial infarction (MI) compared with men. This may be partly explained by differences in risk factors such as age and diabetes. However, several reports have focused on the occurrence of a sex bias making women less likely to be subjected to angiography and revascularization as well as aggressive pharmacologic treatment of acute MI. The decision to initiate these procedures is often based on ischemic changes of the electrocardiogram. It was therefore investigated whether differences between men and women in magnitude of electrocardiographic changes during myocardial ischemia could explain some of the differences previously reported. A total of 178 patients with chest pain suggestive of MI (135 men and 43 women) included in a study of thrombolytics were monitored for 24 hours with continuous vectorcardiography. Also, 81 patients with stable angina pectoris undergoing elective angioplasty were monitored during the procedure. In patients admitted with suspicion of MI, the initial summated ST deviation was 178 +/- 146 microV for men as compared with 105 +/- 91 microV for women (P = .002). During angioplasty, men had significantly more pronounced maximum ST deviation during inflation of the balloon (235 +/- 165 vs 156 +/- 89 microV; P = .036). In conclusion, men have more pronounced ST changes than women during myocardial ischemia. When fixed magnitudes of ST deviation are required for initiating therapy such as thrombolytics, this will favor treatment of men. A sex-adjusted limit for administrating thrombolytic drugs may be warranted in the light of the above findings.

Angioplasty, Balloon, Coronary↗

PubMed2003

Prognostic value of ST-segment resolution-when and what to measure.

AIMS: Analyses of ST-segment resolution during acute myocardial infarction has, during recent years, challenged coronary angiography as gold-standard for predicting myocardial reflow and future risk. We have previously reported that continuous ST-monitoring can be done accurately in the clinical setting. We now set out to compare the prognostic value of previously suggested cut-offs for ST-segment resolution, and determine the times to measure these. METHODS AND RESULTS: We analysed 752 patients with ST-elevation infarction, from the second Assessment of Safety and Efficacy of a New Thrombolytic (ASSENT 2) and ASSENT-PLUS studies, either with vectorcardiography or continuous 12-lead ST-monitoring. All analyses were made blindly by two independent observers. Times to 20, 30, 50 and 70% ST-segment resolution were examined in relation to 30-day mortality.The optimal cut-off for ST-segment resolution analyses was found to be 50%, measured at 60 min. We could hereby identify a large low-risk group, 40% of the population, with only 1.4% 30-day mortality. Furthermore, 88% of deaths were correctly predicted within 1h of observation and treatment. CONCLUSION: Continuous ST-monitoring of patients with acute myocardial infarction yields important prognostic information after 60 min of observation and should be used for very early-risk stratification in these patients.

Aged↗