(A) study on the use of the electrocardiogram for diagnostic evaluation of patients with mitral valvular disease
Electrocardiography has been long an important tool in cardiac diagnosis and, with advances in electrocardiography, the accuracy of the electrocardiographic diagnosis has been greatly increased. Though the most accurate methods for quantitative diagnosis of mitral valvular disease are cardiac catheterization and ventriculography, these procedures are time consuming, expensive, and not without risk. Thus, it would be helpful if routine catheterization of the heart could be avoided in patients who are potential candidates for mitral valvuotomy. This could be done if reliable electrocardiographic criteria could be found for estimating the amount of obstruction and leak at the mitral valve.
As mitral valvular dysfunction progress, changes(hypertrophy and/or dilatation) in the left atrium and both ventricles are inevitable. Many authors attempted to characterize the electrocardiographic findings of such changes according to the
specific lesion of the mitral valve. In addition to atrial fibrillation, characteristic P wave changes and their diagnostic significance have been reported(Macruz et al, 1958; Arevalo et al., 1963; Morris et al., 1964). The diagnostic importance of QRS voltage difference in precordial leads has been stressed in the differential diagnosis of specific lesions of mitral valvular disease(Janton et al., 1954; Bateman and January, 1955; Wierum and Glenn, 1957; Bentivoglio et al, 1958; Imperial et al., 1960).
Semler and Pruitt(1960) reported that a mean QRS electrical axis of +91° or more degrees was the most frequent positive single index of increased total pulmonary resistance in mitral stenosis, and Fowler et al. (1955) stated that precordial lead
V^^1 was very helpful in evaluating the degree of pulmonary hypertension. In Korea there are only a few reports on the electrocardiographic changes in mitral valvular disease and the correlation of electrocardiographic findings and hemodynamics(Oh et al., 1961; Kim 1970; Kim, 1971). It would be evident that the various electrocardiographic findings noted in western races can't be applied to Koreans.
The main objectives of this study are;
1. To determine the electrocardiographic characteristics of pure mitral valvular disease and the differentiation between the specific lesions of pure mitral stenosis, pure mitral insufficiency and combined lesions of mitral stenosis and insufficiency.
2. To know whether the characteristic electrocardiographic changes of mitral stenosis are directly related to the narrowed valve area or to the hemodynamic abnormalities secondary to obstruction.
Subjects and methods
139 cases of isolated mitral valvular disease were reviewed: of these 93 were cases of pure mitral stenosis, 18 were pure mitral insufficiency, and 28 were combined mitral stenosis and insufficiency. Of the total patients, 68 were male and 71 were female. The ages ranged from 10 to 54 years with an average of 35.6 years. Diagnosis was based on cardiac catheterization and supplemented by cineangiocardiography. The conventional 12 lead electrocardiogram was taken at normal sensitivity and at a paper speed of 25mm/sec. The mitral valve area was estimated according to the Gorin's formula and cardiac output was determined by the
direct Fick's principle.
The electrocardiograms were analyzed with respect to:
1. Rhythm (atrial fibrillation and sinus rhythm)
2. Presence or absence of P-mitrale
3. Terminal P force in lead V^^1 (by the method of Morris et al., 1964)
4. Mean QRS electrical axis in frontal plane
5. QRS voltage in precordial leads(V^^1 S^^2 V^^5 R^^(?) & V^^1 S+V^^5-6 R)
6. R/S ratio in lead V^^1
7. Conduction disturbance of right bundle branch block
In patients with pure mitral stenosis the electrocardiographic findings of atrial fibrillation, P-mitrale, terminal P force in lead V^^1 and R/S ratio in lead V^^1 were correlated with the hemodynamic data of mean pulmonary artery pressure, mean pulmonary arterial wedge pressure and mitral valve area. An attempt was made to ascertain whether or not a quantitative correlation could be found. A patient showing electrocardiographic pattern of right bundle branch block was excluded in the evlauation of QRS voltage in lead V^^1 and mean QRS electrical axis in frontal plane.
Results and summary
1. P wave abnormality, which was noted in most(131/139) cases, is apparently a characteristic and most frequent electrocardiographic finding in mitral valvular disease. Of the P wave abnormalities the development of atrial fibrillation and P-mitrale were thought to be related to the duration of the illness rather than to the types of lesion or hemodynamic abnormalities secondary to valvular dysfuntion. However, the terminal P force in lead V^^1 was thought to be related to the mean pulmonary artery pressure and mean pulmonary arterial wedge pressure rather than to the narrowing of the valve.
2. 15 patients showed the electrocardiographic pattern of right bundle branch block. In patients with mitral stenosis this electrocardiographic pattern was noted at almost all levels of mean pulmonary artery pressure, mean pulmonary arterial wedge pressure, mitral gradient and mitral valve area.
3. Mean QRS electrical axis and QRS voltage in precordial leads; There was no case which deviated leftward more than +30° even among cases with a predominant or pure mitral insufficiency. Although the difference of mean value in mean QRS electrical axis and QRS voltage in precordial leads according to the types of the
lesion was significant, this difference was generally not helpful in the differential diagnosis in individual patients because of much overlapping among cases.
4. There was no definite electrocardiographic criteria to differentiate clearly the types of mitral valvular disease. However, the following aspects of electrocardiogram may be useful in differential diagnosis.
a. Difference of QRS voltage in precordial leads; The voltage of V^^1 S and V^^1 S+V^^5-6 R in all patients with pure mitral insufficiency was over 1mm and 11mm respectively. That of V^^1 S+V^^5-6 R in all patients with pure mitral stenosis was below 39mm.
b. R/S ratio in lead V^^1 : There was no case showing "R wave only" in lead V^^1 among patients with pure or predominant mitral insufficiency.
c. Mean QRS electrical axis in frontal plane: The mean electrical axis of all patients with pure mitral stenosis deviated rightward more than +60° in all except one case. None of the patients with pure mitral insufficiency deviated rightward
more than +110°.
5. Relationship between hemodynamics and electrocardiography in patients with mitral stenosis:
Among the hemodynamic abnormalities, mean pulmonary artery pressure showed a close relationship with the following aspects of the electrocardiogram.
a. R/S ratio in lead V^^1 : The mean value of mean pulmonary artery pressure(45.9±3.8mmHg) in groups showing R/S>1 was significantly elevated as compared with that (34.8±1.5mmHg) of groups showing R/S≤1.
b. Mean QRS electrical axis in frontal plane: There was a weak positive correlation (r=+0.53) between mean pulmonary artery pressure and QRS electrical axis in the frontal plane. The QRS axis of all patients with a mean pulmonary artery pressure of 41mmHg or more was +91° or more except for one case.
c. Terminal P force in lead V^^1: The difference of mean value in mean pulmonary artery pressure according to the size of terminal P force in lead V^^1 was significant in all cases.