Vectorcardiographic criteria for the diagnosis of left ventricular hypertrophy

Vectorcardiographic-hemodynamic correlations in adult aortic stenosis

Thirty-nine vectorcardiographic (VCG) data from 45 patients with pure adult aortic stenosis have been tested as to their ability to reflect quantitatively the peak systolic left ventricular pressure (LVPSP), the left ventricular end diastolic pressure (LVEDP), and the X-ray estimated heart volume. VCG was recorded with the axial lead system and simple and multiple linear regression analyses were applied. Eight VCG data correlated significantly (p less than 0.001) with LVPSP, the best indicator being the maximum posterior dislocation in the Z lead (r = 0.65). Through multiple regression analysis a formula was derived which gave a correlation coefficient between observed and calculated pressures of 0.82. The best indicator of LVEDP was the maximum positive P amplitude in the X lead (r = 0.41). The relationship was, however, too poor to have practical significance. A good correlation was found between ST segment dislocation and heart volume (r = 0.65), in good accordance with previous observations as to the effect of right ventricular dilatation on the ECG. The study illustrates how ventricular volume and pressure exert different effects on the ECG, and how all the important hemodynamic aspects in aortic stenosis to some degree are reflected. Only the pressure correlations have, however, practical importance.

Significance of vectorcardiogram in the cardiological diagnosis of the 21st century

Until the mid-1980s, it was believed that the vectorcardiogram presented a greater specificity, sensitivity and accuracy in comparison to the conventional electrocardiogram, in the diagnosis of the different heart diseases. Recent studies revealed that the vectorcardiogram still is superior to the electrocardiogram in very specific situations, such as in the evaluation of electrically inactive areas, in intraventricular conduction disorders combined and/or in association to inactive areas, in the identification and location of ventricular preexcitation, in the differential diagnosis of patterns varying from normal of electrical axis deviation, in the evaluation of particular aspects of Brugada syndrome, and in the estimation of the severity of some enlargements, among others. With the advent of computerized vectorcardiography, a technology that improves the processing and recording method; a future still promising is expected for this methodology. In the fields of education and research, vectorcardiography provided a better and more rational insight into the electrical phenomena that occurs spatially, and represented an important impact on the progress of electrocardiography. Although a few medical centers still use the method as a routine, we hope that the use of this resource will not get lost over time, since vectorcardiography still represents a source to enrich science by enabling a better morphological interpretation of the electrical phenomena of the heart.

Value of normal electrocardiographic findings in predicting resting left ventricular function in patients with chest pain and suspected coronary artery disease

PURPOSE

Characterization of left ventricular function is important in managing patients with coronary artery disease. Although many methods are available to assess left ventricular function, most are either expensive, invasive, or both. In this study, we examined the ability of normal or near-normal resting electrocardiographic findings to predict resting left ventricular ejection fraction, measured by resting radionuclide angiography, in 874 patients with chest pain and suspected coronary artery disease.

PATIENTS AND METHODS

A retrospective review was undertaken of 4,410 Mayo Clinic patients who underwent rest and exercise radionuclide ventriculography for the evaluation of chest pain and known or suspected coronary artery disease; of these, 874 patients met the inclusion criteria for the current study. A 15-lead electrocardiogram, which was interpreted by the cardiologist or cardiology trainee working in the laboratory, was obtained at the same evaluation as the radionuclide study.

RESULTS

In 590 patients with no previous history of a myocardial infarction and entirely normal resting electrocardiographic results without nonspecific ST-T wave abnormalities, the mean left ventricular ejection fraction was 0.63 +/- 0.004, and 559 patients (95%) had a normal resting ejection fraction (defined as 0.50 or more). Both nonspecific ST-T wave abnormalities (p less than 0.001) and, to a lesser degree, a history of myocardial infarction (p = 0.06) were independent predictors of an abnormal resting ejection fraction. In 185 patients with nonspecific ST-T wave abnormalities and no history of myocardial infarction, the mean left ventricular ejection fraction was 0.61 +/- 0.009, and 85% had a normal resting ejection fraction. In 36 patients with nonspecific ST-T wave abnormalities and a history of myocardial infarction, the mean left ventricular ejection fraction was 0.53 +/- 0.021, and 72% had a normal resting ejection fraction.

CONCLUSION

Thus, an entirely normal result on a resting 12-lead electrocardiogram in patients with suspected coronary disease but no history of a previous myocardial infarction is a reliable (95%) predictor of normal left ventricular function. If nonspecific ST-T wave abnormalities are noted, particularly if there is a history of a previous infarction, the predictive value of the electrocardiographic findings is diminished.

Identification of best electrocardiographic leads for diagnosing left ventricular hypertrophy by statistical analysis of body surface potential maps

In view of the increased risk of cardiovascular mortality associated with left ventricular (LV) hypertrophy, early recognition and quantitation of LV hypertrophy are important clinical goals. The standard 12-lead electrocardiogram is the easiest and most widely used noninvasive method for the diagnosis of LV hypertrophy; unfortunately, the diagnostic accuracy of commonly used electrocardiographic criteria remains unsatisfactory. Body surface potential maps contain diagnostic information not present in conventional lead systems. The present investigation combines the increased information content of surface maps with the power of multivariate statistical techniques in order to identify practical subsets of electrocardiographic leads that would allow improved diagnosis of LV hypertrophy. Discriminant analysis was performed on 120-lead data simultaneously recorded in 250 normal subjects and 214 patients with LV hypertrophy using as features instantaneous voltages on time-normalized P, PR, QRS and ST-T waveforms as well as the duration of these waveforms. Leads and features for optimal separation of 173 normal subjects aged greater than or equal to 30 years from 122 patients with pure LV hypertrophy were selected. A total of 6 features from 5 torso sites accounted for a specificity of 97% and a sensitivity of 94%. The single most potent discriminator was the duration of the P wave; voltages were measured in mid and late P on leads located in the lower left parasternal area, the left precordial region and the upper right back, in mid-QRS on a lead positioned 10 cm below V1 and slightly before the peak of the T wave on a lead in the lower left flank.(ABSTRACT TRUNCATED AT 250 WORDS)

When is the vectorcardiogram superior to the scalar electrocardiogram?

The clinical usefulness of the vectorcardiogram is well documented by the numerous reports published in the last 3 decades. It has been found more reliable than the electrocardiogram for the diagnosis of atrial enlargement and right ventricular hypertrophy. It is more sensitive than the electrocardiogram in the recognition of myocardial infarction, especially if the infarction is inferior or if it occurs in the presence of left bundle branch block or left anterior hemiblock. It is helpful in the diagnosis of ventricular pre-excitation and in the localization of the bypass tract. Some repolarization abnormalities are more clearly demonstrated by the vector display. However, some information, such as that on cardiac chamber size and myocardial damage, can also be obtained by other noninvasive tests that are often performed on the same patients. With the increasing awareness of cost-effectiveness of various laboratory procedures in medicine, the vectorcardiogram should no longer be considered a routine cardiac test and should be requested only for a specific clinical purpose. When properly utilized, vectorcardiography should remain a valuable diagnostic as well as teaching tool.

Noninvasive assessment of T-wave abnormalities on precordial electrocardiograms in middle-aged professional bicyclists

Six middle-aged, active, professional bicyclists with T-wave abnormalities on precordial ECGs were studied noninvasively. Twenty-five aged-matched bicyclists without T-wave abnormalities served as the control subjects. Increased voltage of SV1 + RV5 was demonstrated in all subjects. A 5-year follow-up study revealed that these abnormalities of T-wave inversion became more pronounced with age, except in one case. VCGs showed enlargement of anterior QRS loop and discordant T loop, in all cases. On echocardiography, thickness of both the interventricular septum and the left ventricular posterior wall, and left ventricular mass were significantly increased compared with the control group. 201Tl myocardial scintigraphy at rest and during exercise revealed no regional perfusion defects of the tracer in either case. We conclude that: (1) T-wave abnormalities of precordial ECGs in six middle-aged athletes were progressive in nature; and (2) these electrocardiographic abnormalities seem to be related to left ventricular hypertrophy induced by steady and strenuous training rather than to coronary artery disease.

The role of left ventricular conduction in the electrogenesis of left ventricular hypertrophy. An electrophysiologic study in man

Various electrocardiographic and vectorcardiographic (ECG-VCG) patterns of ventricular conduction disturbances are inducible by premature right atrial stimulation (PRAS). These patterns are a consequence of different degrees of refractoriness in the specialized ventricular conduction system. We observed that the intermediate phase of left bundle branch block (LBBB) induced by PRAS in 20 subjects with normal basal QRS (complexes) were similar to those of left ventricular hypertrophy (LVH). In 18 patients with basal ECG-VCG signs of LVH, right bundle branch block (RBBB) induced by PRAS produced a progressive disappearance of these signs and the "normalization" of the tracings. The initial maximum QRS vector decreased, disappeared or remained absent in the patients with LBBB induced by PRAS, and appeared (when absent in the basal VCG) and remained unchanged (when present) in patients with RBBB induced by PRAS. In this paper we discuss the electrogenetic implications of these data. The ECG-VCG sings of LVH are probably dependent on a slowed conduction in the left bundle branch system, while anatomical hypertrophy per se probably plays a less important role.

Anterior QRS loop in hypertrophic cardiomyopathy

Frank vectorcardiograms (VCGs) were reviewed in 45 patients with hypertrophic cardiomyopathy (HCM), 26 with obstruction and 19 without obstruction. Twelve of the 19 patients without obstruction and five of the 26 patients with obstruction were found to have predominantly anterior QRS loops. Fourteen patients had a large left anterior QRS loop with increased anterior and leftward force; the posterior and terminal rightward force were within the normal range, and the T loops were displaced posteriorly and to the right opposite to the QRS loop. Asymmetric septal and apical hypertrophy were noted echocardiographically and/or angiographically. Increased electrical force from the asymmetric hypertrophy of the septal and apical area is proposed to explain this large left anterior loop. Three patients had a QRS loop located anteriorly and to the right with electrocardiograms (ECGs) resembling those of posterolateral myocardial infarction or right ventricular hypertrophy. These finding suggest that (1) hypertrophic cardiomyopathy may be another cause of an anterior QRS loop; (2) the recognition of the large left anterior loop in the VCG in patients with a left ventricular hypertrophy pattern in the ECG is helpful in the diagnosis of HCM, especially the nonobstructive form; and (3) hypertrophic cardiomyopathy should be considered in the differential diagnosis of myocardial infarction or right ventricular hypertrophy.

Hypertrophy or dilatation? A vectorial analysis of echocardiographically determined left ventricular enlargement

Echocardiograms (ECHO) and Frank vectorcardiograms (VCGs) were obtained in three groups of patients: Group I (n = 16), concentric left ventricular hypertrophy (LVH) with increased interventricular septal (IVS) and left ventricular posterior wall (LVPW) thickness in the presence of a normal left ventricular internal dimension (LVID); Group II (n = 17), left ventricular dilatation (LVD) with an enlarged LVID, normal IVS and LVPW thickness, and Group III (n = 22), no catheterization evidence of heart disease with normal IVS, LVPW and LVID. VCGs were analyzed with respect to magnitude of the QRS maximal deflection vector (MDV) and +/- 10 msec QRS vectors, horizontal plane (HP) maximal posterior force, time of HP MDV inscription, distal and proximal HP loop areas and HP loop configuration utlizing criteria of Varriale et al. The results indicate that: 1) HP QRS vector magnitude cannot reliably differentiate concentric LVH from isolated LVD and 2) proximal-distal loop area relationships and pattern of the HP QRS loop, when reviewed together, are superior to other criteria for distinguishing whether ECHO determined LVH or LVD is the primary correlate of an enlarged left ventricle.

Correlation of left ventricular mass determined by echocardiography with vectorcardiographic and electrocardiographic voltage measurements

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Comparison of the vectorcardiogram with the electrocardiogram in the prediction of left ventricular size

The vectorcardiogram has been suggested as an alternative to the electrocardiogram in the diagnosis of left ventricular enlargement. In 107 patients, precordial QRS voltage measurements were compared with vectorcardiographic spatial magnitude measurements in their relationship to angiocardiographically determined left ventricular mass and volume.

Sensitivity, specificity, and linear correlations obtained with instantaneous spatial QRS magnitude measurements were similar to those obtained with selected precordial voltage measurements suggested by Sokolow and Grant. Multiple regression analysis incorporating time-strength integrals of the spatial QRS correlated more closely with left ventricular mass (R = 0.75) and total volume (R = 0.80) than did similar analysis using precordial voltages (R = 0.71). These differences are statistically significant ( P = <0.01) but reduce the remaining variability of the electromotive-left ventricular size relationship by only 7 to 14% and leave 30 to 40% of the total variability unexplained. These findings do not support a large practical advantage for the vector-cardiogram over the electrocardiogram in the prediction of left ventricular size.