Signal-averaged P wave duration and the dimensions of the atria

Predictive value of electrocardiographic markers in children with dilated cardiomyopathy

Dilated cardiomyopathy (DCM) refers to a heterogeneous group of cardiomyopathies characterized by ventricular dilatation and myocardial systolic dysfunction, which can lead to serious consequences such as malign arrhythmia, sudden death, heart failure, and thromboembolism. With its economical, non-invasive, simple and reproducible advantages, electrocardiogram (ECG) has become an important indicator for assessing the prognosis of cardiovascular diseases. In recent years, more and more studies of electrocardiography on DCM have been carried out, but there is still a lack of a comprehensive summary of its prognostic value. This article reviews the prognostic value of electrocardiographic markers in children with DCM.

Beat-to-beat P-wave morphology as a predictor of paroxysmal atrial fibrillation

BACKGROUND AND OBJECTIVES

Atrial Fibrillation (AF) is the most common cardiac arrhythmia. The initiation and the perpetuation of AF is linked with phenomena of atrial remodeling, referring to the modification of the electrical and structural characteristics of the atrium. P-wave morphology analysis can reveal information regarding the propagation of the electrical activity on the atrial substrate. The purpose of this study is to investigate patterns on the P-wave morphology that may occur in patients with Paroxysmal AF (PAF) and which can be the basis for distinguishing between PAF and healthy subjects.

METHODS

Vectorcardiographic signals in the three orthogonal axes (X, Y and Z), of 3-5 min duration, were analyzed during SR. In total 29 PAF patients and 34 healthy volunteers were included in the analysis. These data were divided into two distinct datasets, one for the training and one for the testing of the proposed approach. The method is based on the identification of the dominant and the secondary P-wave morphology by combining adaptive k-means clustering of morphologies and a beat-to-beat cross correlation technique. The P-waves of the dominant morphology were further analyzed using wavelet transform whereas time domain characteristics were also extracted. Following a feature selection step, a SVM classifier was trained, for the discrimination of the PAF patients from the healthy subjects, while its accuracy was tested using the independent testing dataset.

RESULTS

In the cohort study, in both groups, the majority of the P-waves matched a main and a secondary morphology, while other morphologies were also present. The percentage of P-waves which simultaneously matched the main morphology in all three leads was lower in PAF patients (90.4 ± 7.8%) than in healthy subjects (95.5 ± 3.4%, p= 0.019). Three optimal scale bands were found and wavelet parameters were extracted which presented statistically significant differences between the two groups. Classification between the two groups was based on a feature selection process which highlighted 7 features, while an SVM classifier resulted a balanced accuracy equal to 93.75%. The results show the virtue of beat-to-beat analysis for PAF prediction.

CONCLUSION

The difference in the percentage of the main P-wave-morphology and in the P-wave time-frequency characteristics suggests a higher electrical instability of the atrial substrate in patients with PAF and different conduction patterns in the atria.

Signal-averaged P wave duration and the long-term risk of permanent atrial fibrillation

OBJECTIVE

To assess the long-term risk of developing permanent AF in relation to the signal-averaged P wave duration (SAPWD) and clinical and echocardiographic characteristics.

DESIGN

In an observational study design we studied 131 patients with earlier ECG-documented AF and successfully restored sinus rhythm attending a long-term, follow-up visit at hospital or at home. Established permanent AF was examined in relation to primary clinical, echocardiographic, and electrophysiological parameters.

RESULTS

Only prolonged SAPWD (p=0.006) was associated with an increased risk of development of permanent AF. The risk of permanent AF after 3 years follow-up was 0.72 with an SAPWD equal to 180 ms versus 0.39 with a normal SAPWD (130 ms). We found no prognostic effect of age, gender, dilated left atrium, long duration of AF history, or long duration of the most recent episode of AF. Co-existing hypertension reduced the risk of permanent AF; this could be explained by concomitant treatment with angiotensin-converting-enzyme-inhibitors.

CONCLUSION

Prolonged SAPWD (a marker of atrial remodelling) appears to be a risk factor for long-term development of permanent AF.

Signal-averaged P wave analysis for delineation of interatrial conduction - further validation of the method

BACKGROUND

The study was designed to investigate the effect of different measuring methodologies on the estimation of P wave duration. The recording length required to ensure reproducibility in unfiltered, signal-averaged P wave analysis was also investigated. An algorithm for automated classification was designed and its reproducibility of manual P wave morphology classification investigated.

METHODS

Twelve-lead ECG recordings (1 kHz sampling frequency, 0.625 microV resolution) from 131 healthy subjects were used. Orthogonal leads were derived using the inverse Dower transform. Magnification (100 times), baseline filtering (0.5 Hz high-pass and 50 Hz bandstop filters), signal averaging (10 seconds) and bandpass filtering (40-250 Hz) were used to investigate the effect of methodology on the estimated P wave duration. Unfiltered, signal averaged P wave analysis was performed to determine the required recording length (6 minutes to 10 s) and the reproducibility of the P wave morphology classification procedure. Manual classification was carried out by two experts on two separate occasions each. The performance of the automated classification algorithm was evaluated using the joint decision of the two experts (i.e., the consensus of the two experts).

RESULTS

The estimate of the P wave duration increased in each step as a result of magnification, baseline filtering and averaging (100 +/- 18 vs. 131 +/- 12 ms; P < 0.0001). The estimate of the duration of the bandpass-filtered P wave was dependent on the noise cut-off value: 119 +/- 15 ms (0.2 microV), 138 +/- 13 ms (0.1 microV) and 143 +/- 18 ms (0.05 microV). (P = 0.01 for all comparisons). The mean errors associated with the P wave morphology parameters were comparable in all segments analysed regardless of recording length (95% limits of agreement within 0 +/- 20% (mean +/- SD)). The results of the 6-min analyses were comparable to those obtained at the other recording lengths (6 min to 10 s). The intra-rater classification reproducibility was 96%, while the interrater reproducibility was 94%. The automated classification algorithm agreed with the manual classification in 90% of the cases.

CONCLUSION

The methodology used has profound effects on the estimation of P wave duration, and the method used must therefore be validated before any inferences can be made about P wave duration. This has implications in the interpretation of multiple studies where P wave duration is assessed, and conclusions with respect to normal values are drawn.P wave morphology and duration assessed using unfiltered, signal-averaged P wave analysis have high reproducibility, which is unaffected by the length of the recording. In the present study, the performance of the proposed automated classification algorithm, providing total reproducibility, showed excellent agreement with manually defined P wave morphologies.

Intra- and interatrial asynchrony in patients with heart failure

Heart failure (HF) is associated with atrial conduction delay. Color tissue Doppler imaging was used to evaluate intra- and interatrial asynchrony in patients with HF, patients with structural heart disease without HF, and controls. Twenty-three controls (mean age 65 +/- 13 years), 29 patients with structural heart disease without HF (mean age 68 +/- 9 years), and 29 patients with HF (mean age 67 +/- 9 years) were studied. Patients had no histories of atrial fibrillation. Echocardiographic color tissue Doppler imaging of the atria was performed. Measurements below the atrioventricular plane were selected on the right atrial (RA) free wall, interatrial septum (IAS), and left atrial (LA) free wall. The time difference from the onset of the P wave to the onset of the A wave at the right atrium (P-RA), the IAS (P-IAS), and the left atrium (P-LA) was measured. Asynchrony was defined as the differences between P-IAS and P-RA (RA asynchrony), P-LA and P-IAS (LA asynchrony), and P-LA and P-RA (interatrial asynchrony). In patients with HF, a significant increase in RA asynchrony was observed compared with controls and patients without HF (30 +/- 21 vs 12 +/- 13 and 14 +/- 15 ms, p <0.001). LA asynchrony was not different (19 +/- 26 vs 25 +/- 13 vs 25 +/- 14 ms, p = NS). Interatrial asynchrony was significantly increased in patients with HF (49 +/- 24 vs 37 +/- 9 and 39 +/- 17 ms, p = 0.04). There were moderate but significant correlations of RA asynchrony with log N-terminal-pro-B-type natriuretic peptide (r = 0.3, p = 0.01) and the ejection fraction (r = -0.4, p <0.001). In conclusion, in patients with HF, significant RA and interatrial asynchrony was documented, evaluated by noninvasive color tissue Doppler imaging. Asynchrony was related to N-terminal-pro-B-type natriuretic peptide and to the ejection fraction.

P-wave amplitude and pulmonary artery pressure in scleroderma

BACKGROUND AND PURPOSE

Scleroderma is an immune-mediated disease characterized by excess deposition of collagen leading to microvascular occlusion. Morbidity and mortality are often secondary to pulmonary hypertension from injury to pulmonary microvasculature and interstitial lung disease. This study correlated P-wave findings on the 12-lead electrocardiogram (ECG) with mean pulmonary artery pressure (mPAP) measured by right heart catheterization in patients with scleroderma.

METHODS

A retrospective review of 12-lead ECGs in 23 patients referred to a rheumatology clinic with the diagnosis of scleroderma was performed. Right heart catheterization was performed within 1 month of the resting ECG.

RESULTS

Linear regression related P-wave amplitude in lead II with mPAP (r = 0.52, P = .011) This model was 73% sensitive and 67% specific for the presence or absence of elevated mPAP.

CONCLUSIONS

P-wave amplitude analysis on the ECG may be helpful in the assessment of pulmonary hypertension in patients with scleroderma.

Age-related changes in human left and right atrial conduction

INTRODUCTION

Advancing age is an independent risk factor for atrial fibrillation (AF), which is considered to be initiated by ectopic triggers and maintained by an arrhythmogenic substrate. It is not known whether substrate changes produce this age-related increase in propensity toward AF. We addressed the hypothesis that advancing age is associated with changes in biatrial electrophysiology even in patients with no history of atrial arrhythmias.

METHODS AND RESULTS

Patients with left-sided accessory pathways and requiring routine electrophysiological studies were recruited. Electroanatomic mapping was performed in the left and right atria of 23 patients (age ranging from 17 to 75 years) with structurally normal hearts and no history of AF during sinus rhythm and pacing. Unlike previous studies, a trigonometric method was used to quantify wavefront propagation velocities (WPV) precisely in the direction of propagation. Refractoriness was measured at 2 cycle lengths, at three different atrial sites. Both right (r =-0.77, P < 0.0001) and left (r =-0.79, P < 0.001) atrial WPV demonstrated strongly inverse correlation with age. Furthermore, left and right WPVs were highly correlated (r = 0.66, P < 0.01), with velocities being 6.4 +/- 2.2 cm/sec higher in the right atria (P < 0.01). Refractoriness was significantly correlated with increasing age only at the septum (r = 0.53, P < 0.01). Left atrial wavelength was inversely correlated with increasing age (r =-0.56, P = 0.03). P wave duration was associated with age (r = 0.42, P = 0.04) and left atrial size (r = 0.44, P = 0.04) but not atrial WPV.

CONCLUSION

Aging human atria demonstrate progressive decline in WPV and increase in septal refractoriness. These age-related changes in biatrial electrophysiology are likely to be important factors in the age-related increase in AF prevalence.

Is Electrocardiography Still Useful in the Diagnosis of Cardiac Chamber Hypertrophy and Dilatation?

The echocardiogram undoubtedly is part of the cardiologist's armamentarium in the diagnosis and elucidation of cardiac abnormalities, but the ECG still continues to be the most frequently recorded noninvasive test in medicine. For many patients, particularly those who have newly diagnosed hypertension, a 12-lead ECG recording may be the only test that is required as a baseline measure. For those who have possible heart failure, an ECG and B-type natriuretic peptide measurement may be sufficient to obviate the need for an echocardiogram. Electrocardiography and echocardiography will continue to live side-by-side for the foreseeable future.