Vectorcardiographic Variables Research Articles

Elective lung resection increases spatial QRS-T angle and QTc interval.

Lung resection changes intra-thoracic anatomy, which may affect electrocardiographic results. While postoperative cardiac arrhythmias have been recognized after lung resection, no study has documented changes in vectorcardiographic variables in patients undergoing this surgery. The purpose of this study was to analyse changes in spatial QRS-T angle (spQRS-T) and corrected QT interval (QTc) after lung resection. Adult patients undergoing elective lung resection under general anaesthesia were studied. The patients were allocated into four groups: those undergoing (1) left lobectomy (LL); (2) left pneumonectomy (LP); (3) right lobectomy (RL); and (4) right pneumonectomy (RP). The spQRS-T angle and QTc interval were measured one day before surgery (baseline) and 24, 48 and 72 h after surgery. Seventy-one adult patients (47 men and 24 women) aged 47-80 (65 ± 7) years were studied. In the study group as a whole, lung resection was associated with significant increases in spQRS-T (p < 0.001) and QTc (p < 0.05 at 24 and 48 h and p < 0.01 at 72 h). The greatest changes were noted in patients undergoing LP. Postoperative atrial fibrillation (AF) was noted in 6.4% of patients studied, in whom the widest spQRS-T angle and the most prolonged QTc intervals were also noted. Lung resection widens the spQRS-T angle and prolongs the QTc interval, especially in patients undergoing LP. While postoperative AF was a relatively rare complication after lung resection in this study, it was associated with the widest spQRS-T angles and most prolonged QTc intervals.

Changes in spatial QRS-T angle and QTc interval in patients with traumatic brain injury with or without intra-abdominal hypertension

IntroductionTraumatic brain injury (TBI) affects cardiac electrical function, and several extra-cerebral factors, including intra-abdominal pressure (IAP), might further modulate this brain-heart interaction. The purpose of this study was to investigate the impact of TBI, and of increased IAP during TBI, on cardiac electrical function as measured by vectorcardiographic (VCG) variables. MethodsSurvival, IAP and changes in VCG variables including spatial QRS-T angle and QTc interval were measured in consecutive adult patients with either isolated TBI (iTBI), or with TBI accompanied by polytrauma to the abdomen and/or limbs (pTBI). For all patients, observations were performed just after the admission to the ICU (baseline) and at 24, 48, 72 and 96h after admission. Results74 patients aged 45±18 were studied. 44 were treated for iTBI and 30 for pTBI. In all patients, spatial QRS-T angle and QTc interval increased after TBI (p<0.001), relatively more so in patients with pTBI. Compared to survivors, non-survivors also ultimately had greater widening of the spatial QRS-T angle (p<0.001), most notably just before foraminal herniation. Wider spatial QRS-T angle and longer QTc interval were also noted in patients with IAP>12mmHg (p<0.001), and with right compared to left hemispheric injury (p<0.001). ST segment level at the J point decreased 24 and 48h after TBI in leads I, II, III, aVR, aVF, V1, V2, V3 and V6, and increased in lead V1, especially in non-survivors. ConclusionsSpatial QRS-T angle and QTc interval increase after TBI. If foraminal herniation complicates TBI, further widening of the spatial QRS-T angle typically precedes it, followed by notable narrowing thereafter. Increased IAP also intensifies TBI-associated increases in spatial QRS-T angle and QTc interval.

Intra-abdominal hypertension increases spatial QRS-T angle and elevates ST-segment J-point in healthy women undergoing laparoscopic surgery

BackgroundIntra-abdominal hypertension (IAH) impairs cardiovascular function, however an effect of IAH on cardiac electrophysiology has been poorly documented. The aim of this study was to evaluate the effect of IAH following pneumoperitoneum on vectorcardiographic variables reflecting cardiac repolarisation and depolarisation. MethodsOtherwise healthy women undergoing elective gynaecological laparoscopy were studied. Intra-abdominal pressure (IAP), spatial QRS-T angle and ST-segment J-point (STJ) were observed during surgery and the early postoperative period. ResultsForty women, ages 22 to 43 were examined. Induction of IAH to 15mmHg significantly widened the spatial QRS-T angle, whereas the Trendelenburg position subsequently reduced this widening. IAH also increased STJ voltage in leads III, aVF, V2 and V3 during surgery, with increased STJ voltage persisting in several leads through the morning of postoperative day 1. ConclusionInduction of IAH impacts the relationship between cardiac depolarisation and repolarisation and increases spatial QRS-T angle and STJ voltage.

Role of the vectorcardiogram-derived spatial QRS-T angle in diagnosing left ventricular hypertrophy

IntroductionCurrent criteria for electrocardiographic (ECG) diagnosis of left ventricular hypertrophy (LVH) have a low diagnostic accuracy. Addition of demographic, anthropomorphic, and additional ECG variables may improve accuracy. As hypertrophy affects action potential morphology and intraventricular conduction, QRS prolongation and T-wave morphology may occur and become manifest in the vectorcardiographic variables spatial QRS-T angle (SA) and spatial ventricular gradient. In this study, we attempted to improve the diagnostic accuracy for LVH by using a combination of demographic, anthropomorphic, ECG, and vectorcardiographic variables. MethodsThe study group (n = 196) was divided in 4 subgroups with, on one hand, echocardiographically diagnosed LVH or a normal echocardiogram and, on the other hand, with any of the conventional ECG signs for LVH or with normal ECGs. Each subgroup was randomly split into halves, yielding 2 equally-sized (n = 98) data sets A and B. Age, sex, height, weight, body mass index, body surface area (BSA), frontal QRS axis, QRS duration, QT duration, maximal QRS vector magnitude, SA, and ventricular gradient magnitude and orientation were univariate studied by receiver operating characteristic analysis and were used to build a stepwise linear discriminant model using P < .05 as entry and P > .10 as removal criterion. The discriminant model was built in set A (model A) and tested on set B. Stability checks were done by building a discriminant model on set B and testing on set A and by cross-validation analysis in the complete study group. ResultsThe discriminant model equation was D = 5.130 × BSA − 0.014 × SA − 8.74, wherein D greater than or equal to 0 predicts a normal echocardiogram and D less than 0 predicts LVH. The diagnostic accuracy (79%) was better than the diagnostic accuracy of conventional ECG criteria for LVH (57%). ConclusionThe combination of BSA and SA yields a diagnostic accuracy of LVH that is superior to that of the conventional ECG criteria.

Women react with more myocardial ischemia and angina pectoris during elective percutaneous transluminal coronary angioplasty.

Women have been considered to be at higher risk of complications relating to percutaneous transluminal coronary angioplasty (PTCA) than are men. One reason for this sex-related difference could be the ischemic response of myocardium during the procedure. To investigate whether there are sex-related differences in ischemic response of myocardium during elective PTCA. Consecutive patients (n = 192, of whom 48 were women), were subjected to vectorcardiography during the PTCA procedure. Vectorcardiographic variables, magnitude of ST-segment vector (ST-VM), and magnitude of ST-segment vector change (STC-VM) were studied. Women were older (63 +/- 10 versus 56 +/- 10 years, P< 0.001) than men in our study and more often had diabetes mellitus and hypertension. Women less often had stents implanted (24 versus 50%, P < 0.01) and they were subjected to fewer balloon inflations (P < 0.001), with a total inflation time shorter than that for men (P< 0.001). Maximum STC-VM was 25% greater for women (P < 0.05). Women reported greater maximum pain (P < 0.05) and nitroglycerine was more frequently used for them during PTCA (P < 0.05). Occurrence of episodes of residual ischemic STC-VM (the difference between total number of episodes and number of balloon inflations) was more common for women (3 +/- 5 versus 1 +/- 3, P< 0.01). Duration of residual ischemic STC-VM episodes (the difference between total duration of episodes and duration of balloon inflations) was longer for women than it was for men (242 +/- 275 versus 148 +/- 233 s, P < 0.05). In a stepwise multivariate analysis and for a matched case-control group, episodes of residual STC-VM and duration of residual STC-VM episodes still indicated that there was an independent sex-related difference (P < 0.01 and P < 0.01, respectively). Women more commonly develop vectorcardiographic signs of severe myocardial ischemia, more frequently experience episodes of ischemia and report more severe angina pectoris during elective PTCA than do men.

Myocardial recovery after cardiac surgery: A study of hemodynamic performance and electrophysiology during the first 18 postoperative hours

Hemodynamic and vectorcardiographic variables were monitored in 23 patients with acquired heart disease, before and during the first 18 postoperative hours of cardiac surgery. The hemodynamic pattern directly after surgery was characterized by left ventricular depression and increased heart rate. Thus, stroke volume index had decreased from the preoperative 29 +/- 1 to 24 +/- 1 mL/beat/m2, and heart rate had increased from 61 +/- 2 to 94 +/- 4 beats/min. During the following hours a gradual normalization of stroke volume occurred, leading to a cardiac index that was adequate after 8 to 10 hours, judging from the mixed venous oxygen saturation (68% +/- 1%). Fourteen patients had an uneventful postoperative course, with no signs of acute myocardial infarction, and did not require inotropic support. These patients had small but consistent vectorcardiographic changes; the QRS vector difference increased moderately, and the ST vector magnitude also increased. No correlation was found between hemodynamic and vectorcardiographic variables, nor between timing of hemodynamic recovery and vectorcardiographic changes. Patients with a perioperative myocardial infarction had a vectorcardiographic pattern that was compatible with acute myocardial infarction. These patients had markedly elevated ST vector magnitude and QRS vector difference values, which were discernible during the first postoperative hours. The present data suggest that the timing of metabolic and electrophysiological recovery of the heart differ, and a computerized vectorcardiographic system may be of value in the early detection of perioperative myocardial infarction.

Quantitative electrocardiographic and vectorcardiographic study on newly-diagnosed non-insulin-dependent diabetic and non-diabetic control subjects.

Quantitative electrocardiographic (ECG) and vectorcardiographic (VCG) analysis was carried out in 113 newly diagnosed, middle-aged, non-insulin-dependent diabetics (61 men, 52 women) and 125 non-diabetic control subjects (56 men, 69 women) in order to explore changes attributable to non-coronary heart disease (diabetic cardiomyopathy) in diabetics. Diabetic men had a prolonged PQ interval and women a more negative P-terminal force and a more leftward frontal QRS axis than their non-diabetic counterparts, but no other significant differences we found between diabetic and non-diabetic subjects in various quantitative ECG and VCG variables when the effect of confounding factors (age, obesity, coronary heart disease, hypertension, drugs) was taken into account. The more negative P-terminal force and left axis deviation in diabetic women could be explained by a concomitant left ventricular hypertrophy among them. Non-insulin-dependent (type 2) diabetes, which is commonly preceded by a long duration of asymptomatic hyperglycaemia, is not associated, early in its clinical course, with major ECG and VCG abnormalities suggestive of diabetic cardiomyopathy.

Use of vectorcardiography in determination of the left ventricular muscle mass.

Many studies have investigated different ECG and vectorcardiographic (VCG): criteria for diagnosis of left ventricular hypertrophy (LVH). In some investigations VCG was more sensitive than ECG in this respect. This study was performed to elucidate whether it is possible also to determine the degree of LVH using VCG. Eighty cardiovascularly healthy subjects aged 15-39 were investigated with ECG, VCG (Frank system) and echocardiography. The echocardiographic left ventricular (LV) mass has been shown by others to correlate closely to the anatomical and the angiographically determined LV mass and was used as reference standard. Thirty-eight of the subjects were endurance sportsmen and had a LV mass above standard reference limits. The measured ECG variables were R-amplitude in a VL, I, V5, V6, S-amplitude in V1 and SV1 + RV5/V6 and the VCG variables were QRS spatial area and circumference and left maximal spatial vector. The sensitivity and specificity of single criteria tested were similar for ECG and VCG in the quantitative determination of LVH. The correlations between ECG-amplitudes and the magnitude of the LV mass were weak. The correlations were higher with the VCG-variables, QRS spatial circumference being superior to the others, but not good enough to permit an estimation of the LV mass in individual subjects. In conclusion, normal VCG variables were highly specific for a normal LV mass but in individuals with LVH, VCG was not useful for the estimation of the LV mass.

Comparative accuracy of computerized spatial vectorcardiography and standard electrocardiography for detection of myocardial infarction

New computerized spatial vectorcardiographic variables were analyzed by discriminant analyses for group classification of 94 patients with acute myocardial infarction and 79 normal subjects. Using the integral of the sequential magnitudes of the spatial vectors during the period of initial abnormal depolarization (IAD) of the QRS at a discriminating value of 3 mv X msec., 87% of the subjects were correctly classified with a sensitivity of 85%; specificity of 88%; and an overall predictive accuracy of 87%, p less than .00001. The period of initial abnormal depolarization in which the vectors were integrated was determined by the first derivative of the sequential magnitudes of the spatial vectors of the QRS waveform (dm/dt). The mean value of dm/dt during the period of abnormal depolarization was a poor discriminating variable. The predictive accuracy of this new electrocardiographic criterion for diagnosis of myocardial infarction compared favorably with other computerized methods such as vectorcardiography, polarcardiography, Aitoff spatial trajectory, the 12-lead ECG derived by the Frank XYZ leads as well as the standard 12-lead ECG.

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.

The vectorcardiogram in subjects with sex chromosome aneuploidy

Vectorcardiographic variables have been studied in patients with sex chromosome abnormalities and compared with normal controls. Several of these variables were found to be correlated with the number of sex chromosomes in the karyotype, some being related to the number of X chromosomes, some to the number of Y chromosomes, and others to both. The variables concerned included time intervals and vector magnitudes in both the QRS and ST-T wave complexes. The heart rate itself proved dependent on both the X and the Y chromosome complements. The correlations could not be explained by age, height, or weight differences between the seven different karyotype groups studied. The dependences of variables other than the heart rate remained after correction for between-group heart rate differences. The findings are discussed.

Prediction of hemodynamic data in atrial septal defects of secundum type from simple and combined vectorcardiographic data

A search for simple and combined VCG data which could optimally predict right ventricular systolic pressure (RVSP) or shunt size was made in 50 patients with atrial septal defects of the secundum type. VCG was recorded by means of the axial lead system and a multiple regression computer program was applied. Fifty-four VCG data, age, sex, and systolic blood pressure were tested as independent predictors. Seventeen VCG data were significantly correlated with RVSP and six with flow. The best individual variable was the simple maximal negative deflection in Lead X (r = 0.64, p < 0.001). The correlations with flow were poorer, but of theoretical interest. Distinctive differences in the VCG-RVSP relationships were found in atrial septal defects compared with those in pulmonary stenosis, indicating that the increased flow sensitizes the right ventricle to the effect of pressure. Through multiple regression analysis, an equation based on four vectorcardiographic variables was derived. This equation improved the RVSP-VCG correlations significantly (p < 0.05, r = 0.80). The study confirms that vectorcardiogram is a reasonably reliable method for estimating RVSP in patients with atrial septal defects and that the use of combined VCG data may improve the method considerably.