Chapter 7: Atrial Abnormalities and Their Relationship to Ventricular Abnormalities

J. Willis Hurst, MD

 [Ventricular Electrocardiography © 1991, 1998 J. Willis Hurst, MD]
 
 

Right Atrial Abnormality

Abnormalities of the atria may be reflected in abnormalities of the P waves, and abnormalities of the P waves may be clues to abnormalities of the ventricles and QRS complexes. The depolarization and repolarization of the atria are discussed in Chapter 4. The abnormal P wave vectors characteristic of right (P1) and left (P2) atrial abnormalities are discussed below. P wave abnormalities may be caused by intrinsic disease of the atria (a localized conduction defect), atrial enlargement, or atrial hypertrophy. So far, it has not been possible to separate one cause from another. Accordingly, we will refer to such abnormalities as atrial abnormalities without specifying their precise nature.
 
 

Right Atrial Abnormality

The electrocardiographic characteristics of a right atrial abnormality are listed in Table 7.1, and examples of such an abnormality are shown in Figs 7.1 and 7.2.
Click to zoom Figure 7.1

 This electrocardiogram was recorded from a 36-year-old female with Ebstein's anomaly of the tricuspid valve. The PR interval is 0.22 second; the QRS duration is 0.13 second; and the QT interval is 0.36 second.

P waves: The amplitude of the P wave measured in lead II is 2.25mm. In lead V2, it is 4mm and its duration is 0.08 second. The direction of Pm is at +45°, and slightly anterior. P1 is at +50°, directed slightly anteriorly. P2 is at +30°, almost parallel with the frontal plane. When the amplitude of P2 is multiplied by its duration in V1, the product is-0.08mm/sec. The shape, duration, and amplitude of the P waves, plus the direction of the P1 vector, indicate a right atrial abnormality. The measurement of -0.08mm/sec for the second half of the P wave in V1 does not indicate a left atrial abnormality in this patient. The depolarization of the huge, abnormal right atrium produces the abnormality of the P wave (P2) in lead V1; the electrical forces are initially directed anteriorly and then posteriorly on their way to the left atrium. First degree atrioventricular block and a right atrial abnormality are present.

 QRS complex: The mean QRS vector is directed +110° to the right and slightly anteriorly. The mean initial 0.04 second QRS vector is directed +80° inferiorly, and slightly posteriorly (note Q waves in leads aVL, V1, and V2). This is likely to be abnormal: the initial QRS forces are posterior to the subsequent forces, producing the Q waves followed by R and S waves in lead V2. The mean terminal 0.04-second QRS vector is directed +120° inferiorly, and flush with the frontal plane. (Note that the last 0.04 second of the QRS complex in lead aVR is almost isoelectric, whereas the initial portion of the complex is negative; the terminal QRS forces are directed more to the right than are the initial ones). The QRS duration and the direction of the mean QRS and mean terminal 0.04 second QRS vectors indicate a variety of right bundle branch block (RBBB). 

T waves: The mean T vector is directed -60° to the left and slightly posteriorly. The ventricular gradient is not definitely abnormal. The T wave abnormalities are of the secondary type.

A. The frontal plane projections for the mean P, P1, P2, mean QRS, the initial 0.04-second QRS, the terminal 0.04-second QRS, and T vectors.

B. The spatial orientation of the mean P vector. Note the course of the transitional pathway on the chest.

C. The spatial orientation of the mean P1 vector. Note the course of the transitional pathway on the chest.

D. The spatial orientation of the mean P2 vector. Note the transitional pathway.

 Summary: This electrocardiogram shows first-degree atrioventricular block, a right atrial abnormality, RBBB, an abnormal mean initial 0.04-second QRS vector, and a secondary T wave abnormality. The P wave abnormality of the magnitude shown here, plus RBBB, has a predictive value of almost 100 percent in indicating Ebstein's anomaly of the tricuspid valve. The abnormal mean initial 0.04-second QRS vector produces abnormal Q waves. In another setting, myocardial infarction should be considered, but with the abnormal P waves and RBBB, the QRS abnormality here is more likely the "pseudo-infarction" of Ebstein's anomaly.

Click to zoom Figure 7.2

 This electrocardiogram was recorded from a 72-year-old man with atherosclerotic coronary heart disease and obstructive lung disease. The PR interval is 0.16 second, the QRS duration is 0.09 second, and the QT interval is 0.28 second.

P waves: The amplitude of the P wave measured in lead II is 3.25mm and its duration is 0.08 second. The mean P vector (Pm) is directed vertically at about +80° and slightly anteriorly. Note the depressed PQ and ST segments, produced by the Ta wave. There is definite evidence of right atrial abnormality.

 QRS complex: The QRS magnitude is normal; the total QRS amplitude is 135mm. The mean initial 0.02 second QRS vector is directed slightly to the left, superiorly, and anteriorly. The mean QRS vector is directed vertically about +70°, and about 60° posteriorly.

 T wave: The mean T vector is directed at +65° to the left and anteriorly; the QRS-T angle is about 75°.

 A. The frontal plane projections of the mean P (Pm), QRS, and T wave vectors.

B. The spatial orientation of the mean P vector (Pm). Note the course of the transitional pathway on the chest.

C. The spatial orientation of the mean QRS vector. Note the course of the transitional pathway on the chest.

D. The spatial orientation of the mean T vector. Note the course of the transitional pathway on the chest.

 Summary: A right atrial abnormality associated with a posteriorly-directed vertical mean QRS vector should lead the clinician to search for acquired diseases, such as cor pulmonale, as a cause for these electrocardiographic abnormalities.

There are no other abnormalities that resemble these; the problem is to distinguish P waves that are characteristic of a right atrial abnormality from normal P waves.

 The ventricular abnormalities responsible for right atrial abnormality are Ebstein's anomaly, tricuspid atresia or stenosis, right ventricular hypertension due to mitral stenosis; left ventricular disease with elevated left ventricular diastolic pressure and pulmonary hypertension; pulmonary emboli; Eisenmenger's syndrome; primary pulmonary hypertension, pulmonary valve stenosis, the tetralogy of Fallot, and chronic obstructive lung disease.
 
 

Left Atrial Abnormality

The electrocardiographic characteristics of a left atrial abnormality are listed in Table 7.2. An example is shown in Figure 7.3.
Click to zoom Figure 7.3

 This electrocardiogram was recorded from a 34-year-old woman with mitral stenosis due to rheumatic heart disease. The PR interval is 0.21 second; the QRS duration is about 0.09 second; and the QT interval is 0.42 second.

P wave: The amplitude of the P wave measures 2.25mm in lead II, and the duration of the wave is 0.11 to 0.12 second. It is notched at about the halfway mark. The mean P vector (Pm) is directed inferiorly (+70°) and posteriorly. The mean vector for right atrial depolarization (P1) is directed inferiorly and slightly posteriorly and that of left atrial depolarization (P2) is directed inferiorly and posteriorly. The product of multiplying the second half of the P wave by its amplitude as measured in lead V1 is 0.065mm/sec. The P wave duration of 0.11 to 0.12 second, plus the abnormality of the second half of the P wave in lead V1 (with the product of duration multiplied by amplitude exceeding -0.03 mm/sec), indicates a left atrial abnormality. The Ta wave is seen in lead II where it displaces the PQ segment downward. First-degree atrioventricular block is present. 

QRS complex: The mean QRS vector is directed inferiorly by about +70°, and moderately posteriorly. Although the mean QRS vector is directed normally, there is the possibility of its being directed abnormally when it is considered along with the abnormal P2. 

T wave: The mean T vector is directed at +35° and posteriorly; this is abnormal. The direction of the mean T vector suggests a delay in repolarization of the right ventricle.

 A. The frontal plane projections for the mean P, QRS, and T vectors.

B. The spatial orientation of the mean P vector (Pm). Note the course of the transitional pathway on the chest.

C. The spatial orientation of the mean P1 vector. Note the course of the transitional pathway on the chest.

D. The spatial orientation of the mean P2 vector. Note the course of the transitional pathway on the chest.

E. The spatial orientation of the mean QRS vector. Note the course of the transitional pathway on the chest.

F. The spatial orientation of the mean T vector, showing the course of the transitional pathway on the chest.

 Summary: The abnormalities are first-degree atrioventricular block, a definite left atrial abnormality, a mean QRS vector directed inferiorly (+70°) and posteriorly, and a mean T vector that is directed away from the right ventricle. The predictive value of this cluster of abnormalities for mitral stenosis approaches 100 percent.

There are two problems in identifying left atrial abnormalities electrocardiographically. The first is to distinguish the P wave abnormalities that are characteristic of a left atrial disorder from normal P waves. The second occurs because localized atrial disease, undoubtedly interfering with atrial conduction, may simulate left atrial abnormalities caused by the disorders listed below; there is no way to distinguish them with certainty.

 The cardiac abnormalities often associated with a left atrial abnormality are rheumatic mitral stenosis, congenital mitral atresia, left atrial myxoma, mitral regurgitation from any cause, left ventricular disease with an elevated left ventricular diastolic pressure due to aortic regurgitation of any cause, aortic stenosis, and cardiomyopathy.
 
 

Combined Right and Left Atrial Abnormalities

The electrocardiographic characteristics of combined right and left atrial abnormalities are listed in Table 7.3. Examples of abnormalities involving both the right and left atria are shown in Figures 7.4 and 7.5.
Click to zoom Figure 7.4

 Combined right and left atrial abnormalities. This electrocardiogram was recorded from a 49-year-old man with severe aortic regurgitation. The PR interval is 0.155 second; the QRS duration is 0.08 second; and the QT interval is 0.34 second.

P waves: The amplitude of the P wave in lead II is 2.75mm and its duration is 0.09 second. The mean P vector (Pm) is directed inferiorly (+62°), and abnormally posteriorly. The product of the duration of the second half of the P wave (0.05 second) multiplied by the amplitude (1.5mm) in lead V1 is -.075mm/sec. The increased amplitude of the P waves and their duration of 0.09 second signify a right atrial abnormality, while the definitely abnormal P wave in lead V1 indicates a left atrial abnormality. A small Ta wave is seen during the PQ segment in lead II.

 QRS complex: The duration of the QRS complex is normal (0.08 second). The mean QRS vector is directed inferiorly (+65°) and markedly posteriorly. The 12-lead total QRS amplitude is more than 237mm (note that the QRS amplitude is probably even greater than this because it overruns the edge of the electrocardiographic paper in leads V2, V3, V5, and V6), and this increase is indicative of left ventricular hypertrophy. 

T wave: The mean T vector is directed inferiorly (about +90°) and markedly anteriorly. The QRS-T angle is abnormal (about 150°), and characteristic of early systolic pressure overload of the left ventricle. This occurs with severe or longstanding left ventricular diastolic pressure overload. The T wave is abnormal and represents left ventricular hypertrophy. The T wave vector will gradually become increasingly anteriorly directed, finally assuming a direction opposite that of the mean QRS vector.

 A. The frontal plane projections of the mean P (Pm), QRS, and T vectors.

B. The spatial orientation of the mean P vector (Pm). Note the course of the transitional pathway on the chest.

C. The spatial orientation of the mean QRS vector. Note the transitional pathway on the chest.

D. The spatial orientation of the mean T vector. Note the transitional pathway on the chest. 

Summary: There is evidence of a right atrial abnormality (a P wave duration 0.09 second and amplitude of 2.75mm) as well as a left atrial abnormality (the duration of the second half of the P wave multiplied by its amplitude equals 0.075mm/sec) in lead V1. The total 12-lead QRS amplitude with a normal QRS duration indicates left ventricular hypertrophy. The mean T vector is abnormal, being directed 150° away from the mean QRS vector; this indicates an early stage of systolic pressure overload of the left ventricle. The patient had aortic regurgitation, which produced diastolic pressure overload of the left ventricle. This figure illustrates how a late stage of diastolic pressure overload of the left ventricle blends into an early stage of systolic pressure overload of the left ventricle. The ECG in this patient could be due to aortic stenosis, a late phase of aortic regurgitation, or the late stage of mitral regurgitation. In any of these conditions, heart failure is likely, because the right atrial abnormality is related to an increase in pulmonary artery pressure which can be caused by advanced disease.

Click to zoom Figure 7.5

 Combined right and left atrial abnormalities. This electrocardiogram was recorded from a 25-year-old man with dilated cardiomyopathy. He had severe heart failure and was waiting for cardiac transplantation. The PR interval is 0.24 second; the QRS duration is 0.10 second; and the QT interval is 0.32 second. The ventricular rate is 109 depolarizations per minute.

P waves: The amplitude of the P wave in lead II is 3mm and its duration is 0.10 second. The mean P vector (Pm) is directed inferiorly (+45°) and posteriorly. The duration of the second half of the P wave (Pm) in lead V1 is 0.04 second, and when this is multiplied by the P2 wave amplitude which is 2.5mm, the product is -0.10mm/sec; this indicates the presence of a left atrial abnormality. There is evidence of a right atrial abnormality, in that the P waves in lead II have an amplitude of 3mm and a duration of 0.10 second.

 QRS complex: The duration of the QRS complex is 0.10 second. The mean QRS vector is directed inferiorly (+110°) and posteriorly. The 12-lead total QRS amplitude is more than 228mm (the deflections are recorded below the grid marks on the paper in leads V2, V3, and V4).

 T waves: The mean T vector is directed superiorly (-90°) and markedly anteriorly. The QRS-T angle is almost 180°. The T wave abnormality is characteristic of systolic pressure overload of the left ventricle.

 A. The frontal plane projection of the mean P (Pm), QRS, and T vectors.

B. The spatial orientation of the mean P vector (Pm). Note the course of the transitional pathway on the chest.

C. The spatial orientation of the mean QRS vector. Note the transitional pathway on the chest.

D. The spatial orientation of the mean T vector. Note the transitional pathway on the chest.

 Summary: Analysis of the P waves indicates the presence of both right and left atrial abnormalities. The mean QRS vector is directed inferiorly (+110°) and posteriorly, suggesting either hypertrophy of the right and left ventricles or left ventricular hypertrophy plus left posterior-inferior division block. The T wave abnormality indicates systolic pressure overload of the left ventricle. There are biatrial abnormalities and biventricular hypertrophy. Whereas these abnormalities could be due to a combination of anatomic and physiologic factors, in this case, they are due to dilated cardiomyopathy which produced severe heart failure and pulmonary hypertension.

The problem is to separate the P wave abnormalities that are characterized as right and left atrial abnormalities from normal P waves.

 The cardiac abnormalities often associated with right and left atrial abnormalities are rheumatic mitral stenosis with pulmonary hypertension, mitral regurgitation from any cause plus pulmonary hypertension, Eisenmenger's syndrome due to patent ductus arteriosus or ventricular septal defect, cardiomyopathy, and severe heart disease with aortic valve disease, with or without mitral valve disease, plus pulmonary hypertension.

 A Word of Caution

 Many unusual and peculiar P waves will be encountered. They are peculiar because they do not exhibit the abnormalities listed in Tables 7.1, 7.2, and 7.3. For the present no more can be said. Some peculiar, but not definitely abnormal, P waves may be due to localized defects in the depolarization of the atria that have nothing to do with ventricular disease.


Copyright information: Ventricular Electrocardiography by J. Willis Hurst, MD, was initially published by Gower Medical Publishing in 1991. The rights to the book were then transferred to Mosby Wolfe and in 1996 were returned to the author, Dr. Hurst.

 J. Willis Hurst, MD, received his degree from the Medical College of Georgia and served his residency in internal medicine at the same institution. He completed his cardiology fellowship with Dr. Paul White at Massachusetts General Hospital in Boston. Dr. Hurst was Professor and Chairman of the Department of Medicine of Emory University School of Medicine from 1957 to 1986. He received the Gifted Teacher Award and Master Teacher Award of the American College of Cardiology and the Distinguished Teacher Award from the American College of Physicians, and was designated a Master of the American College of Physicians. He served as President of the American Heart Association in 1972 and was given the AHA's Gold Heart and Herrick Awards. Dr. Hurst was Chairman of the Cardiovascular Board of the American College of Physicians for several years and served on the council of the National Heart, Lung, and Blood Institute. He was President Lyndon Johnson's cardiologist for 18 years. He is well known for the book The Heart and many other contributions to the medical literature. Currently, Dr. Hurst is Consultant to the Division of Cardiology of Emory University, and spends his mornings teaching and his afternoons writing.