Leftward shift of the terminal P forces in the ECG associated with left atrial enlargement

P wave and the development of atrial fibrillation

BACKGROUND

Terminal P-wave inversion in lead V(1) representing left atrial overload has been considered a precursor of atrial fibrillation (AF).

OBJECTIVE

The purpose of this study was to determine whether this P-wave morphologic characteristic can predict the development of AF.

METHODS

Digital analysis of 12-lead ECGs was performed to enroll patients with P terminal force > or =0.06 s x 2 mm in lead V(1) from among a database of 308,391 ECG recordings. The prognostic value of ECG characteristics for developing AF was determined.

RESULTS

A total of 78 patients (mean age 52 +/- 19 years) with left atrial overload were chosen from among 102,065 patients in the database. During mean follow-up of 43 months, 15 (19%) patients developed AF (AF group) versus 63 (81%) patients who did not (non-AF group). No significant difference was noted between the AF and non-AF groups with regard to the area, duration, and amplitude of the P-wave terminal portion in lead V(1). In contrast, the area, duration, and amplitude of the P-wave initial portion in the same lead were significantly greater in the AF group than in the non-AF group (114.6 +/- 73.0 microV x ms vs 73.1 +/- 59.3 microV x ms, 42.2 +/- 12.4 ms vs 35.7 +/- 10.1 ms, and 94.0 +/- 39.9 microV vs 68.8 +/- 49.4 microV, respectively; P <.05 for each). Multivariate analysis confirmed that the area of the P-wave initial portion was independently associated with the development of AF (hazard ratio 4.02, 95% confidence interval 1.25-17.8; P = .018).

CONCLUSION

P-wave initial portion in lead V(1) was an independent risk stratifier of AF development in patients with marked left atrial overload.

Hypodensity of the cerebral white matter in patients with transient ischemic attack or minor stroke: influence on the rate of subsequent stroke. Dutch TIA Trial Study Group

In a prospective study of 3,017 patients with transient ischemic attack or minor ischemic stroke from the Dutch Transient Ischemic Attack Trial, the presence or absence of diffuse hypodensity of the white matter on a baseline computed tomography (CT) scan of the brain was related to the occurrence of subsequent stroke. On entry, 337 patients were judged to have diffuse hypodensity of the white matter on CT; they were older (71.4 +/- 7.4 years versus 64.4 +/- 9.9 years), more often had hypertension (50% versus 41%), and more often had lacunar infarcts on CT scan (40% versus 26%) than did patients with normal white matter. Strokes, fatal or nonfatal, occurred in 51 (15%) of the patients with diffuse hypodensity of the cerebral white matter, compared to 217 (8%) in the group with normal white matter (crude hazard ratio, 2.0; 95% confidence interval, 1.4-2.7). After adjustment for age and other relevant entry variables, the hazard ratio was 1.6 (95% confidence interval, 1.2-2.2). In patients younger than 70 years the crude hazard ratio was 2.7 (95% confidence interval, 1.7-4.2). The distribution between the main subtypes of stroke was similar for patients with and those without diffuse hypodensity of the cerebral white matter: Intracerebral hemorrhage occurred in 6 and 9%, cortical infarction in 47 and 45%, and lacunar infarction in 34 and 29%, respectively. We conclude that hypodensity of the cerebral white matter in patients with transient ischemic attack or minor stroke is associated with an extra risk of future stroke, from large as well as from small vessels, and particularly in patients under 70 years old; this increase of risk is independent of other risk factors for stroke.

The mortality predictive power of discharge electrocardiogram after first acute myocardial infarction

The prognostic value of discharge ECG was studied in 457 patients after their first acute myocardial infarction. Thirteen different ECG variables were studied on the discharge ECG. When cumulative 4-year survival rates were calculated by standard life-table method for each variable individually, the following variables had statistically significant prognostic power: PTF (P terminal force), PTFA (P terminal frontal axis), AF (atrial fibrillation), ST depression, ST elevation, QRS duration, and the combination block (LBBB/RBBB + LAHB/LPHB). The variables with no statistically significant predictive power were: QTc, LBBB or RBBB, LAHB or LPHB, AV block, T wave angle, T negativity, and sigma R. The relative risks for the most important variables in the discrete life-table model were: PTF 3.4, QRS duration 3.3, ST depression 2.6, PTFA 2.5, and ST elevation 2.2. In further analysis a model with only three ECG variables (PTF, ST depression, and ST elevation) was developed which stratified the study population in categories with 1.9% to 75.5% estimated 4-year survival rates.

Electrocardiographic and vectorcardiographic study of interatrial conduction disturbances with left atrial retrograde activation

From 81,000 ECGs we collected 83 cases that fulfilled the criteria of Interatrial Conduction Disturbances with Left Atrial Retrograde Activation (IACD-LARA) (P +/- in II, III and VF with P width greater than or equal to 120 msec.). We present the detailed study of 35 cases with surface ECG and VCG and 29 cases with orthogonal ECG leads. The results are then compared against two control groups: with cardiopathy (30 cases) and without cardiopathy (25 cases). The prevalence of IACD-LARA was nearly 1% globally, and 2% among patients with valvular heart disease. The diagnostic criteria for IACD-LARA are: 1) ECG: P +/- in II, III and VF with P greater than or equal to 120 msec. with open angle (usually greater than 90 degrees) between the first and the second part of the P.2) Orthogonal ECG: P +/- in Y lead with a negative mode greater than 40 msec. 3) VCG: More than 50 msec. above the X or Z axis, duration of the P loop greater than or equal to 110 msec., open angle between the two parts of the P loop in both frontal (131.3 degrees +/- 32.3) and right sagital planes (171.2 degrees +/- 15.1), and presence of notches and slurrings in the last part of the P loop.

Sensitivity and specificity of commonly used electrocardiographic criteria for left atrial enlargement determined by M-mode echocardiography

To assess the sensitivity and specificity of 6 commonly used electrocardiographic criteria for left atrial (LA) enlargement, the rest ECGs of 99 patients in normal sinus rhythm were analyzed. Fifty-seven of the patients had LA enlargement and 42 had a normal LA dimension as determined by M-mode echocardiography. The 6 criteria studied and their respective sensitivities and specificities were as follows: (1) duration of the negative phase of the P wave in lead V1 greater than 40 ms: sensitivity, 83%; specificity, 80%; (2) notched P wave in any standard lead with an interpeak duration greater than 40 ms: sensitivity, 15%; specificity, 100%; (3) P terminal force (depth X duration of the terminal portion of the P wave) in lead V1 more negative than -0.04 mm X s: sensitivity, 69%; specificity 93%; (4) depth of the negative phase of the P wave in lead V1 greater than or equal to 1 mm: sensitivity, 60%; specificity, 93%; (5) total P-wave duration greater than 110 ms in any standard lead: sensitivity, 33%; specificity, 88%; (6) total P wave duration/P-R interval duration greater than 1.6: sensitivity, 31%; specificity, 64%. Combining 2 or more of these criteria did not substantially improve sensitivity and specificity.

The prognostic value of the P wave morphology in the discharge ECG in a 5-year follow-up study after myocardial infarction

The discharge ECG's of 641 patients with acute myocardial infarction (AMI) (WHO categories "definite" and "possible" AMI) were studied to assess the prognostic value of P wave morphology as an index of left ventricular dysfunction. Of 69 patients with abnormal P terminal force (PTF), i.e., --0.03 mm.sec. or more negative, 53.6 per cent died within the next 5 years of ischemic heart disease, compared with 20.4 per cent of 558 patients with normal PTF. The odds ratio (age-corrected risk to die, Mantel-Haenszel test) was 4.1 (95 per cent confidence limits 2.4 to 7.0). The mortality curve of patients with normal PTF was linear whereas there was an abrupt rise in mortality rate during the first six months if PTF was abnormal. Of a group of 15 patients with the frontal axis of the terminal P wave --30 degrees or more negative, 8 died (Odds ratio 4.7; 1.3 to 17.1). Ten patients had atrial fibrillation, and five of them died (Odds ratio 2.; 0.5 to 12.9). In 14 cases the duration of the P wave in Lead II was 0.12 sec. but it showed no relationship to mortality (p less than 0.10). The significance of the P wave morphology on the discharge ECG to long-term survival after MI has been demonstrated. These simple ECG variables, related to left ventricular failure, can easily be put to clinical use to differentiate MI patients who are in greater risk of dying during the chronic phase.

P wave abnormalities in the orthogonal electrocardiogram: Correlation with ventricular overload in pulmonic and aortic valvular heart disease

The correlation between several P wave measurements form the orthogonal electrocardiogram (SVEC III lead system) extracted by computer analysis and simple hemodynamic parameters related to ventricular dysfunction was studied in two groups of patients. Group I consisted of 32 patients with pulmonic valvular stenosis and intact interventricular septum. There was a significant correlation between electrocardiographic criteria of right atrial overload and the two hemodynamic parameters studied: peak pulmonic systolic pressure gradient and right ventricular end diastolic pressure (r = 0.502, p smaller than 0.005 and r = 0.661, p smaller than 0.001 respectively). Group II consisted of 49 patients with aortic valve disease. In this group, a significant correlation between the electrocardiographic parameters of left atrial overload and the left ventricular end diastolic pressure could be demonstrated only be a multivariate regression analysis (r = 0.630, p smaller than 0.005). The P wave measurements that are well correlated with the ventricular end diastolic pressure can be considered as valuable criteria for atrial enlargement secondary to a decrease of ventricular compliance, such as seen in ventricular hypertrophy, failure or in ventricular constrictive or restrictive diseases. The pathophysiologic mechanisms of the influence of the ventricular overload (dysfunction) on the atrial function and the resulting P wave changes are discussed.

Disturbances in atrial rhythm and conduction following the surgical creation of an atrial septal defect by the Blalock-Hanlon technique

Disturbances in atrial conduction or rhythm, or both, were found in 16 of 27 patients undergoing the surgical creation of an atrial septal defect by the Blalock-Hanlon technique. These included P-wave aberrations of intra-atrial block and ectopic atrial rhythm, A-V rhythm, A-V dissociation, sinus bradycardia, atrial flutter, escape-capture bigeminy, and atrial premature beats. Some of these were transient and occurred within 2 weeks after surgery. It seems likely that tissue trauma engendered by the clamp and resection of the atrial septum with possible injury to the internodal conducting pathways may be the genesis of these early postoperative disturbances. Of the eight cases with transient disturbances, six occurred in this period. Later changes, such as intra-atrial block, sinus bradycardia, and atrial flutter, may be attributed to changes in atrial size secondary to the postoperative pathophysiology. Digitalis intoxication and congestive heart failure cannot be excluded as contributory factors in either the early or the late disturbances. It was not possible to correlate the incidence and nature of these disturbances with morbidity and mortality. In such severely ill, cyanotic infants, irregularities, however slight, may have altered cardiac function significantly and contributed to their deaths.

Left atrial rhythm. Experimental production in man

Various criteria have been proposed for the diagnosis of left atrial rhythm (LAR) in previous experimental and electrocardiographic studies. Differentiation from A-V junctional rhythms remains ill-defined. In order to assess the left atrial (LA) P wave and to define LAR, the P wave and loop were studied by direct LA pacing in 11 patients undergoing diagnostic transseptal left heart catheterization. Experimental LAR produced changes in P-wave configuration and polarity. These changes were most obvious in lead V 1 and indicated reversal of the sequence and direction of activation with left atrial preceding right atrial depolarization. A typical "dome and dart" P wave occurred in two studies. P-wave configuration in leads I and V 6 was highly variable; frequent orientation of the LA P vector within the transitional zone of the horizontal electrical axis was thought to be responsible. The LA P loop showed reversal of the direction of inscription of the initial forces, indicating a change in the pattern of atrial depolarization. Stimulation of the appendage produced left-to-right spread of atrial depolarization, whereas activation of the main body was directed primarily anteriorly. Impulse formation in the right side of the posterior wall was usually directed from right to left. When the postero-inferior area was activated, the anterior P vector became directed superiorly, and resembled that of coronary sinus rhythm (CSR) in the frontal plane.

This study indicates that the P wave in lead V 1 is most important in the diagnosis of LAR; inversion of the P wave in lead V 6 is not essential. LAR can usually be differentiated from CSR, since in the horizontal plane, activation of the LA main body is more anteriorly directed than the spatial P vector of CSR.