Prediction of the Recurrence of Atrial Fibrillation After Successful Cardioversion with P Wave Signal‐Averaged ECG

Background: The recurrence of atrial fibrillation (AF) was often observed after cardioversion. Methods: In our study, a P wave triggered P wave signal‐averaged ECG (P‐SAECG) was performed on 118 consecutive patients 1 day after successful electrical cardioversion in order to evaluate the utility of this method to predict AF after cardioversion. We measured the filtered P wave duration (FPD) and the root mean square voltage of the last 20 ms of the P wave (RMS 20). Results: During a 1‐year follow‐up, a recurrence was observed in 57 patients (48%). Patients with recurrence of AF had a larger left atrial size (41.9 ± 4.0 vs 39.3 ± 3.1 mm, P < 0.0003), a longer FPD (139.6 ± 16.0 vs 118.2 ± 14.1 ms, P < 0.0001), and a lower RMS 20 (2.57 ± 0.77 vs 3.90 ± 0.99 μV, P < 0.0001). A cutoff point (COP) of FPD ≥126 ms and RMS 20 ≤3.1 μV could predict AF with a specificity of 77%, a sensitivity of 72%, a positive value of 75%, a negative predictive value of 75%, and an accuracy of 75%. A stepwise logistic regression analysis of variables identified COP (odds ratio 9.97; 95% CI, 4.10–24.24, P < 0.0001) as an independent predictor for recurrence. Conclusions: We conclude that the probability of recurrence of AF after cardioversion could be predicted by P‐SAECG. This method seems to be appropriate to demonstrate a delayed atrial conduction that might be a possible risk factor of reinitiation of AF.     

P wave signal-averaged ECG in normal population and in patients with converted atrial fibrillation

Background: Signal‐averaged electrocardiography of the P wave (P wave SAECG) is a noninvasive method for evaluating the risk of atrial fibrillation (AF). We aimed to study P wave SAECG parameters in a large number of apparently healthy subjects and to compare them with patients with converted AF. Methods: We examined 591 individuals; P wave SAECG were recorded in 330 normal subjects, 31 patients with converted persistent AF and 57 patients with converted paroxysmal AF immediately after conversion, at 12 and 24 hours after conversion, then after 3 and 6 months. P wave SAECG were recorded using a commercially available machine aiming to obtain a noise level <1 μV. Results: In the normal population the duration of the filtered P wave (PWD) was higher in men. P wave duration, RMS₄₀ and RMS₃₀ were significantly correlated with age. By comparing the normal population with patients with persistent AF converted to sinus rhythm we demonstrated significant differences in PWD and P wave integral. Patients with recurrent persistent AF had significantly higher PWD. The study of patients with paroxysmal AF, compared to the control group, showed significant increase of the same parameters: PWD and integral of the P wave. Patients with recurrent paroxysmal AF had higher PWD and lower RMS₄₀, RMS₃₀, RMS₂₀. Conclusions: Filtered P wave duration was higher in men; PWD was weakly but significantly correlated with age. Patients with paroxysmal or persistent AF converted to sinus rhythm had significantly higher P wave duration and P wave integral. Ann Noninvasive Electrocardiol 2011;16(4):351–356     

Predictors of atrial flutter with 1:1 conduction in patients treated with class I antiarrhythmic drugs for atrial tachyarrhythmias

OBJECTIVES: The purpose of the study was to look for the predictor factors of atrial proarrhythmic effects of class I antiarrhythmic drugs. BACKGROUND: Class I antiarrhythmic drugs may induce or exacerbate cardiac arrhythmias. The predictors of ventricular proarrhythmia are known. The predictors of atrial flutter with 1:1 conduction are unknown. METHODS: Clinical history, EGG, signal-averaged EGG (SAECG) and electrophysiologic study were analysed in 24 cases of 1:1 atrial flutter with class I AA drugs and in 100 control patients without history of 1:1 atrial flutter with class I AA drugs. RESULTS: The ages of patients varied from 46 to 78 years. Underlying heart disease was present in nine patients. The surface EGG revealed the presence of a short PR interval (PR<0.13 ms), visible in leads V5, V6 in eight (35%) patients with normal P wave duration; in other patients with prolonged P wave duration, PR seemed normaL On SAECG recording, there was a pseudofusion between P wave and QRS complex. The electrophysiologic study revealed some signs indicating a rapid AV nodal conduction (short AH interval or rate of 2nd degree AV block at atrial pacing >200 beats/mm) in 19 of the 23 studied patients. All patients, except one, had at least one sign indicating a rapid AV nodal conduction (short PR and/or P wave-QRS complex continuity on SAECG). In the control group, seven patients (7%) had a short PR interval (P<0.01) and 11 (11%) had a pseudofusion between P wave and QRS complex on SAECG (P<0.001). The P wave-QRS complex pseudofusion on SAECG had a sensitivity of 100% and a specificity of 89% for the prediction of an atrial proarrhythmic effect with class I antiarrhythmic drug. CONCLUSION: We recommend avoiding class I AA drugs in patients with a short PR interval on surface EGG and to record SAECG in those with apparently normal PR interval to detect a continuity between P wave and QRS complex, which could indicate a rapid AV nodal conduction, predisposing to 1:1 atrial flutter with the drug.     

Atrial fibrillation after coronary artery bypass surgery: P wave signal averaged ECG, clinical and angiographic variables in risk assessment.

BACKGROUND: Atrial fibrillation (AF) is a commonly encountered arrhythmia and occurs in up to 40% of patients after coronary artery bypass surgery (CABG). The preoperative signal averaged ECG (SAECG) P wave may be useful indicator of AF after CABG. We prospectively analyzed the predictive value of SAECG P wave compared to clinical variables. METHODS: Fifty-three patients with coronary artery disease undergoing first elective CABG were enrolled. All patients had P wave specific SAECG, standard 12 lead ECG, ejection fraction and left atrial posteroanterior diameter from the echocardiogram within the 24 h before surgery. From the SAECG P wave, filtered P wave duration was measured. Lead II P wave duration, left atrial enlargement and left ventricular hypertrophy were determined from standard ECG. Patients were continuously monitored during their postoperative period and serial ECGs were taken. RESULTS: During an observation period of up to 16 days, 19 (35.8%) patients developed AF 2.8+/-1.3 days after CABG. Patients with AF more often had left atrial enlargement (LAE) on ECG (P = 0.041) and right coronary artery (RCA) lesion (P = 0.0034). The filtered P wave duration on the SAECG was significantly longer in the AF patients than those without AF (129.7+/-13.2 ms versus 113.9+/-9.0 ms, P = 0.001). Logistic regression analysis identified independent predictors, estimated adjusted relative risk (95% confidence interval) of AF: with LAE, the relative risk was 2.72 (1.13-5.82), RCA lesion, the relative risk was 3.06 (1.45-6.45) and SAECG P wave duration >122.3 ms, the relative risk was 4.58 (2.11-9.97). The occurrence of AF was predicted by electrocardiographically determined left atrial enlargement with a sensitivity of 36%, specificity of 88%, positive predictive accuracy of 63%, negative predictive accuracy of 71%. If presence of right coronary artery lesion was evaluated these values were 63%, 79%, 63%, 79% subsequently. P wave duration >122.3 ms had a sensitivity of 68%, specificity of 88%, positive predictive accuracy of 76%, negative predictive accuracy of 83%. If both P wave >122.3 ms and presence of right coronary artery lesion were combined, these values were 47%, 94%, 81%, 76% subsequently. CONCLUSION: The predictors of AF after CABG were left atrial enlargement on standard 12 lead ECG, RCA lesion and SAECG P wave duration. Among these predictors, SAECG P wave duration was the best predictor of AF after CABG.     

Usefulness of the P Wave Signal-Averaged Electrocardiogram in Predicting Patients at Risk of Atrial Flutter and Fibrillation Induced by Transesophageal Pacing

Background: Transesophageal pacing (TEP) may be a useful tool in the evaluation of patients with palpitations. The induction of atrial tachyarrythmia by TEP often allows the detection of an underlying re-entrant atrial arrhythmia as a cause of the patients' symptoms. Recently, the P-wave triggered signal-averaged electrocardiogram (SAECG) has been used to detect patients at risk of paroxysmal atrial tachyarrhythmias. The aim of this study was to investigate the usefulness of the P-wave triggered SAECG applied in a group of patients with a history of paroxysmal palpitations to identify those prone to the development of electrically-induced atrial flutter or fibrillation. Methods: The study population consisted of 46 patients (31 men, mean age 43 ± 11 years) investigated for palpitations with concomitant symptoms of dizziness or presyncope. Patients were divided into 2 groups according to the presence or absence of an atrial arrhythmia induced by TEP. Twenty-six consecutive patients (18 men, mean age 44 ± 13 years) demonstrated electrically-inducible, sustained (lasting < 30 s) atrial fibrillation or atrial flutter (arrhythmia group). The control group comprised 20 patients (13 men, mean age 44 ± 9 years) with similar symptoms, but without significant atrial arrhythmia induced by TEP. The following P-wave triggered SAECG indices were calculated: the root mean square voltage for the terminal 10, 20, 30 ms of the filtered P-wave (RMS10,20,30) and time duration of the filtered P-wave (PWD). Results: Patients with atrial fibrillation or flutter induced by TEP demonstrated significantly longer values of the PWD compared to controls (126.5 ± 15.9 ms vs. 108.0 ± 7.0 ms respectively, P > 0.0001). In the former group we also found the decreased voltage of the terminal part of the P-wave: RMS10 (4.1 ± 1.1 ptV vs 5.5 ± 2.1 pV, P = 0.002), RMS20 (5.1 ± 1.4 μ V vs. 7.3 ± 2.6 μ V, P = 0.0007), and RMS30 (6.2 ± 1.8 μ V vs. 8.7 ± 2.5 μ V, P = 0.0003) (all comparisons arrhythmia group vs controls, respectively). Moreover, a value of PWD < 117 ms appeared to have practical value in the detection patients at risk of atrial fibrillation or flutter induced by TEP, with a specificity of 90%, sensitivity of 77%, and positive predictive value of 91%. Conclusion: We conclude that among patients presenting with paroxysmal palpitations the P-wave triggered SAECG had practical value as an noninvasive method to identify those at risk of electrically-inducible atrial fibrillation and flutter. To what extent this could improve the management of these patients merits further evaluation. A.N.E. 1999;4(1):46–52     

Signal‐Averaged P Wave Duration and the Dimensions of the Atria

Background: Delay of atrial electrical conduction measured as prolonged signal‐averaged P wave duration (SAPWD) could be due to atrial enlargement. Here, we aimed to compare different atrial size parameters obtained from echocardiography with the SAPWD measured with a signal‐averaged electrocardiogram (SAECG). Methods: In 74 patients scheduled for elective echocardiography, an SAECG was recorded directly after the echocardiogram. We measured the SAPWD and registered clinical characteristics. The correlation between the SAPWD and the left atrial diameter (LAD), left atrial volume (LAV), right atrial volume (RAV), and total atrial volume (TAV) was analyzed by linear regression analyses. The effect of concomitant risk factors on TAV and the SAPWD was examined. Results: Linear regression analysis showed that the correlation between the SAPWD and the LAD was significant (R²= 0.11, P = 0.03). However, LAV (R²= 0.15, P = 0.009), RAV (R²= 0.27, P = 0.0003), and TAV (R²= 0.37, P < 0.0001) were more strongly correlated to the SAPWD. The TAV and the SAPWD were not significantly associated with coexisting risk factors. Conclusions: The SAPWD is significantly correlated to the atrial size; most strongly to the TAV. The size of the right atrium, with the sinus node area, appears to affect the SAPWD.     

Detection of atrial late potentials with P wave signal averaged electrocardiogram among patients with paroxysmal atrial fibrillation

The analysis of the QRS-complex with signal averaged ECG (SAECG) has been evaluated for patients affected by ventricular tachycardia for a long time. A longer filtered QRS-complex was a marker of a slower ventricular conduction velocity and reentry tachycardia. This method was modified for an analysis of the P wave (P-SAECG). Different filter methods were evaluated for the analysis of atrial late potentials. METHOD: We measured the bidirectional P wave signal averaged ECG of 45 consecutive patients with (group A) and without (group B) paroxysmal atrial fibrillation (PAF) and 15 young volunteers without a cardiac disease (group C). RESULTS: As a result patients with PAF had a significantly lower root mean square voltage of the last 20 ms (RMS 20) (2.59 +/- 0.89) vs 4.08 +/- 1.45 microV, p < 0.0003) and a significantly longer filtered P wave duration (FPD) than patients of the control collective (139.2 +/- 17.5 vs 115.1 +/- 17.7 ms, p < 0.0001) and the young volunteers (3.44 +/- 0.95 microV, p < 0.0001/101.9 +/- 14.2 ms, p < 0.009). Furthermore we found an age-dependent relationship of FPD between group B and C (115.1 +/- 17.7 vs 101.9 +/- 14.2 ms, p < 0.05) but not an age-dependent relationship of the RMS 20 (4.08 +/- 1.45 vs 3.44 +/- 0.95 microV, p = n.s.). A specificity of 80% and a sensitivity of 78% was achieved for identifying patients with atrial fibrillation by using a definition of atrial late potentials as FPD > 120 ms and a RMS 20 < 3.5 microV. CONCLUSIONS: The analysis of the P-SAECG can be used as a non-invasive method for identifying atrial late potentials. Atrial late potentials might be a reason for PAF. The predictive power of atrial late potentials has to be examined by prospective investigations of a larger patient population.     

Response of the ECG to Short‐Term Diuresis in Patients with Heart Failure

Background: Increase in the amplitude of electrocardiogram (ECG) QRS complexes has been observed in patients treated for heart failure (HF), but the underlying mechanism has not been delineated. Also, correlation of augmentation of the QRS potentials with loss of weight has been noted in patients recovering from anasarca of varying etiology, or after hemodialysis. We assessed the effect of diuresis‐based fluid loss in patients treated for HF on the amplitude of ECG QRS complexes. Methods: This is a cohort study based on ECG and other data from a previously published investigation of patients with HF conducted at a university affiliated hospital, which used new measurements and analysis, performed by a totally blinded investigator based at another institution. Twenty‐one patients (10 men) aged 70.5 ± 12.7 years, 13 with ischemic, and 8 with nonischemic cardiomyopathy, were admitted to the hospital for management of exacerbated HF and were observed for 48 hours. The patients received diuresis, and had routine laboratory testing, documentation of the net fluid lost, and recording of ECGs prior to the initiation of therapy and at 24 and 48 hours. Percent change (%Δ) over the course of observation in the sums of the amplitude of QRS complexes from 12 leads (ΣQRS₁₂), 6‐limb leads (ΣQRS₆), and leads 1 + 2 (ΣQRS₂) in mm of standard ECGs were correlated with net fluid loss corrected for admission weight in mL/kg. Results: Fluid loss amounted to 3204.9 ± 1399.5 mL in the course of 40 ± 23 hours of diuresis. ΣQRS₁₂ was 160.9 ± 42.3 mm before and 170.0 ± 50.7 mm after diuresis (P = 0. 024). Percent change in ΣQRS₁₂, ΣQRS₆, and ΣQRS₂ correlated well with the net fluid loss (r =?0.70, ?0.82, ?0.61, and P = 0.002, 0.0005, 0.001) correspondingly. Conclusion: Changes in sums of the amplitude of QRS complexes of the standard ECG correlates well with net fluid loss in response to short‐term diuresis in patients with HF. Change in the ΣQRS₁₂, ΣQRS₆, and ΣQRS₂ from ECGs before and after diuresis can be used as an easily obtainable and universally available bedside index of the net fluid loss experienced by bedridden patients with HF undergoing therapy.     

A Prospective Study of Atrial Fibrillation After Cardiac Surgery

Background: Atrial fibrillation (AF) is a commonly encountered arrhythmia following cardiac surgery and when sustained, may be associated with significant morbidity. Methods: This large prospective investigation examined a variety of clinical and P wave signal-averaged electrocardiogram (SAECG) parameters to identify independent predictors of AF following cardiac surgery. A total of 272 patients underwent P wave SAECG recording and analysis prior to surgery. Information on their clinical, surgical, and hemodynamic characteristics as well as hospital course was collected. Patients were followed during their postoperative course with telemetry and ECGs. Results: During an observation period of up to 14 days, 79 patients (29%) developed AF 2.5 ± 1.9 days after surgery. Patients who developed AF following cardiac surgery were more likely to be older, undergo valve surgery, to have ejection fraction (EF) < 40%, to have P wave duration on SAECG >140 ms (all P < 0.01), and to take digoxin preoperatively (P < 0.05). A multivariate analysis found that only P wave duration on SAECG >140 ms and EF < 40% were independent predictors of AF following cardiac surgery. The odds ratio of P wave duration on SAECG >140 ms and EF < 40% for the development of AF following cardiac surgery was 3.1 and 2.8, respectively, and 8.7 when combined. Conclusions: Thus, the presence of preexisting abnormal atrial substrate as detected by P wave prolongation on SAECG, and implicated by EF < 40%, clearly predicted a higher risk of AF following cardiac surgery and may provide clinicians with an effective means of identifying those at greatest risk.     

Effect of Obesity on P‐Wave Parameters in a Chinese Population

Objective: To study the association between obesity and P‐wave duration and dispersion (P_d) in order to evaluate the potential risk for atrial fibrillation development in Chinese subjects using the definitions applied for Asian populations. Methods: The study population consisted of 40 obese (body mass index (BMI) ≥ 25 Kg/m², according to the World Health Organization classification for the Asian population) subjects and 20 age‐ and sex‐matched normal weight controls. Maximum P‐wave duration (P_max), minimum P‐wave duration (P_min), and P_d were carefully measured using a 12‐lead electrocardiogram, while the presence of interatrial block (IAB; P ≥ 110 ms) was assessed. Results: There were no significant differences between the two groups regarding age, sex, history of hypertension or diabetes, and hyperlipidemia. Compared to controls, BMI, left atrial diameter (LAD), and interventricular septal thickness were increased, while P_max (111.9 ± 9.3 vs 101.1 ± 6.0 ms, P < 0.01) and P_d (47.9 ± 9.3 vs 31.8 ± 6.9 ms, P < 0.01) were significantly prolonged in the obese group. P_min was similar between the two groups. The prevalence of IAB was significantly greater in the obese subjects. Pearson's correlation analysis showed that there were positive correlations between P_d and BMI (r = 0.6, P < 0.001), as well as between P_d and LAD (r = 0.366, P < 0.05). Conclusion: Our data suggest that obesity is associated with increased P_max and P_d, and increased prevalence of IAB, parameters that have been associated with atrial fibrillation. The correlation of these electrocardiogram parameters with LAD indicates an association between increased BMI and atrial remodeling in Asian subjects. Ann Noninvasive Electrocardiol 2010;15(3):259–263     

Abnormal P‐Wave Morphology Is a Predictor of Atrial Fibrillation Development and Cardiac Death in MADIT II Patients

Background: Several ECG‐based approaches have been shown to add value when risk‐stratifying patients with congestive heart failure, but little attention has been paid to the prognostic value of abnormal atrial depolarization in this context. The aim of this study was to noninvasively analyze the atrial depolarization phase to identify markers associated with increased risk of mortality, deterioration of heart failure, and development of atrial fibrillation (AF) in a high‐risk population with advanced congestive heart failure and a history of acute myocardial infarction. Methods: Patients included in the Multicenter Automatic Defibrillator Implantation Trial II (MADIT II) with sinus rhythm at baseline were studied (n = 802). Unfiltered and band‐pass filtered signal‐averaged P waves were analyzed to determine orthogonal P‐wave morphology (prespecified types 1, 2, and 3/atypical), P‐wave duration, and RMS20. The association between P‐wave parameters and data on the clinical course and cardiac events during a mean follow‐up of 20 months was analyzed. Results: P‐wave duration was 139 ± 23 ms and the RMS20 was 1.9 ± 1.1 μV. None of these parameters was significantly associated with poor cardiac outcome or AF development. After adjustment for clinical covariates, abnormal P‐wave morphology was found to be independently predictive of nonsudden cardiac death (HR 2.66; 95% CI 1.41–5.04, P = 0.0027) and AF development (HR 1.75; 95% CI 1.10–2.79, P = 0.019). Conclusion: Abnormalities in P‐wave morphology recorded from orthogonal leads in surface ECG are independently predictive of increased risk of nonsudden cardiac death and AF development in MADIT II patients. Ann Noninvasive Electrocardiol 2010;15(1):63–72     

Factors Associated with the Development of Atrial Fibrillation in COPD Patients: The Role of P‐Wave Dispersion

Background: Supraventricular tachyarrhythmia is a common problem in chronic obstructive pulmonary disease (COPD) patients. The purpose of this study is to analyze the factors associated with paroxysmal atrial fibrillation (AF) in COPD patients. Methods: Forty COPD patients (38 male, 2 female, mean age 60 ± 9 years) and 33 healthy controls (29 male, 4 female, mean age: 58 ± 10 years) were included in this study. Echocardiography, 24‐hour ambulatory and 12‐lead ECG, pulmonary function tests, arterial blood gases, and serum electrolytes were measured. On ECG, maximum (P_max) and minimum (P_min) duration of P wave and its difference, P‐wave dispersion (PWd), were measured. Results: On echocardiography, diastolic dysfunction was found in 14 of the 40 (35%) COPD patients. Heart rate variability analysis revealed that COPD patients had decreased SDANN, SDNN, SDNNIDX in time‐domain, and decreased LF in frequency domain parameters. Fourteen of the 40 COPD patients (35%) had AF. Patients with AF were older (57 ± 10 vs 64 ± 5 years, P = 0.03) and had lower SDANN, SDNN, and LF/HF ratio as compared to patients without AF in univariate analysis. All P‐wave intervals (P_max P_min and PWd) were increased in COPD patients compared to controls. P‐wave dispersion was significantly increased in COPD patients with AF, as compared to patients without AF (57 ± 11 vs 44 ± 7 ms, P = 0.001). In logistic regression analysis PWd was found to be the only factor associated with the development of AF (P = 0.04). Conclusions: The presence of AF was significantly related to the prolongation of PWd, but not with pulmonary function, arterial blood gasses, and left and right atrial function. A.N.E. 2002;7(3):222–227     

Measurement and reproducibility of magnetocardiographic filtered atrial signal in patients with paroxysmal lone atrial fibrillation and in healthy subjects

Magnetocardiography (MCG) is a method complementary to electrocardiography (ECG). We examined recording and reproducibility of atrial depolarization signal by MCG. Multichannel MCG over anterior chest and orthogonal 3-lead ECG were recorded in 9 patients who had paroxysmal lone atrial fibrillation and in 10 healthy subjects in duplicate at least 1 week apart. Data were averaged using atrial wave template and high-pass filtered at 25, 40, and 60 Hz. Atrial signal duration with automatic detection of onset and offset and root mean square amplitudes of the last portion of atrial signal were determined. Coefficient of variation of atrial signal duration by MCG at 40 Hz was 3.3% and difference between the measurements was 3.5 milliseconds on average. The corresponding figures obtained by signal-averaged ECG (SAECG) were 6.1% and 6.9 milliseconds. Coefficient of variation for root mean square of the last 40 milliseconds of atrial signal were 16% in MCG and 17% in SAECG. Reproducibility was best at 40-Hz filter and similar in patients and healthy subjects. In conclusion, the reproducibility of atrial signal variables in MCG is adequate and somewhat better than in SAECG and equal in patients with lone atrial fibrillation and healthy subjects. Magnetocardiography seems to be a potentially valuable method to evaluate features of atrial depolarization in patient studies.     

Correlation of Mechanical Dyssynchrony with QRS Duration Measured by Signal‐Averaged Electrocardiography

Background: Preimplantation left ventricular dyssynchrony is considered a prerequisite for a beneficial response to cardiac resynchronization therapy (CRT). However, electrical dyssynchrony estimated by QRS duration (QRSd) on ECG has not been proven to be an optimal surrogate of mechanical dyssynchrony. We evaluated the correlation of mechanical dyssynchrony with QRSd as measured by signal‐averaged electrocardiography (SAECG) in comparison with measurements based on conventional surface ECG and with onscreen measurements based on digital ECG. Methods: We included 49 consecutive patients with decompensated heart failure (40 men, aged 66.8 ± 9.5 years), New York Heart Association (NYHA) class II–IV, and LVEF ≤ 40%. QRSd was calculated by manual measurement of 12‐lead ECG, on‐screen measurement of computer‐based ECG, and calculation of total ventricular activation time on SAECG. Results: Only 60.4% of the studied patients had QRS ≥ 120 ms based on measurements derived by SAECG compared to 69.4% by using on‐screen measurement of computer‐based ECG and 73.5% based on surface ECG (P = 0.041). Interventricular but not intraventricular delay was correlated with QRSd. The correlation of interventricular dyssynchrony with QRSd was stronger when measured by SAECG than by surface ECG (r = 0.45, P = 0.001 vs r = 0.35, P < 0.01). Among patients with ischemic cardiomyopathy, no significant correlation was demonstrated between mechanical dyssynchrony and QRSd. In nonischemic patients, interventricular delay was significantly correlated with QRSd measured by surface ECG (r = 0.45, P < 0.05) and SAECG (r = 0.46, P < 0.05). Conclusions: The use of SAECG results in different patient classification in wide QRS complex category as compared to surface ECG. Furthermore, QRSd measured by SAECG is correlated with interventricular but not intraventricular dyssynchrony in heart failure patients.     

P Wave Amplitude and Duration may Predict Immediate Recurrence of Atrial Fibrillation After Internal Cardioversion

Background: Although internal cardioversion (IC) for atrial fibrillation (AF) is effective at restoring sinus rhythm, immediate recurrence (IR) of AF after IC is a major and largely unpredictable clinical problem. The purpose of the study was to determine the role of P wave duration and amplitude in prediction of IR of AF after IC. Forty‐five consecutive patients undergoing IC for chronic AF were evaluated. Material and Methods: After successful IC, 1‐minute ECG recording was obtained in all patients. P wave duration and amplitude in Lead II and V₁ were measured using computer. Forty patients (88%) had successful IC. Thirteen patients experienced IR of AF within 1 minute of restoring sinus rhythm. Results and Conclusion: As a result, the incidence of IR of AF after IC was higher in the patients with shorter P wave amplitude (for lead II P < 0.01 , for V₁P < 0.01 ) and larger P wave duration (for lead II P < 0.01 , for V₁P < 0.05 ).     

The Normal Sequence of Right and Left Atrial Contraction

Objective: To study the sequence of atrial activation and the interatrial electromechanical delay (IEmD) noninvasively in healthy subjects during sinus rhythm (SR). Methods and Results: In 66 SR healthy subjects P‐wave activation was analyzed by means of vectorcardiography. The timing of atrial contractions was measured as the intervals between the P‐wave and the A‐wave of the Doppler right and left ventricular inflows (P‐A_t and P‐A_m), and IEmD was calculated as the algebraic difference PA_m P‐A_t. In the horizontal plane the vectorcardiographic P‐loop was anteroposterior (“typical”, 41 subjects), anterior (18), or posterior (7). IEmD (mean ±; SE 17 ±; 8 ms) was directly related to R‐R and P‐R intervals. IEmD was significantly shorter in anterior and posterior P loops than in the typical (6.5 ±; 5.3 and 8.1 ±; 10.1, respectively, vs 24.2 ±; 3.1 ms). In the posterior P‐loop group, who exhibited longer P‐A_t, mitral E‐wave velocity and E/A ratio were reduced, and left atrial booster function was increased. Conclusion: IEmD was widely variable in SR, reflecting the origin site of sinus impulse, which independently influenced ventricular filling dynamics. A.N.E. 2001;6(3):222–228     

P‐Wave Signal‐Averaged Electrocardiogram Predicts Atrial Fibrillation After Coronary Artery Bypass Grafting

Background: AF is one of the most common complications after CABG. The aim of the study was to identify the risk factors for postoperative AF. Methods: Between June and December 2000, 129 consecutive patients (72 men, 47 women; mean age 67 ± 6 years) underwent preoperative signal‐averaged electrocardiogram (SAECG) with assessment of filtered P‐wave duration (fPWD) and of the root mean square voltage of the last 10 and 20 ms of atrial depolarization (RMSV10 and RMSV20, respectively) before CABG. Results: Fifty‐six (43%) patients developed one episode of AF lasting > 30 seconds at a mean distance of 2.6 ± 1.8 days after surgery (group A), while 73 patients remained in sinus rhythm (group B). No differences between the two groups were found in terms of age, sex, P‐wave duration on the standard ECG, left atrial dimensions, and operative characteristics. In contrast, group A patients showed a significantly longer fPWD (138 ± 10 vs 111 ± 9 ms; P < 0.001) and smaller RMSV10 and RMSV20 (2.8 ± 1.0 vs 4.3 ± 1.1 μV, P < 0.001; 4.2 ± 2.1 vs 6.2 ± 2.0 μV, P < 0.001). Multivariate analysis indicated only fPWD as an independent predictor of AF (P = 0.009). With a cut‐off value of 135 ms for fPWD, the occurrence of AF could be predicted with a sensitivity of 84%, a specificity of 73%, a negative predictive value of 85%, and a positive predictive value of 70%. Conclusion: Preoperative SAECG is a simple exam that correctly identifies patients at higher risk of AF after CABG. A more widespread use of this technique can be suggested. A.N.E. 2002;7(3):198–203     

Predictive Value of P‐Wave Signal‐Averaged Electrocardiogram for Atrial Fibrillation in Acute Myocardial Infarction

Background: Atrial fibrillation (AF) is a common complication of acute myocardial infarction (AMI) with a reported incidence of 7–18%. Recently, P‐wave signal‐averaged electrocardiogram (P‐SAECG) has been used to assess the risk of paroxysmal AF attacks in some diseases. The aim of this study was to determine prospectively whether patients with AMI at risk for paroxysmal AF would be identified by P‐SAECG and other clinical variables. Methods: A total of 100 patients (mean age: 59 ± 12 , 77 male, 23 female) with ST segment elevation AMI were enrolled in this study. Patients with chronic AF were excluded. At entry, all patients underwent standard 12‐lead ECG and in the first 24 hours, P‐SAECG was taken, and echocardiography and coronary angiography were performed on the patients. Patients are followed for a month in terms of paroxysmal AF attacks and mortality. Results: AF was determined in 19 patients (19%). In patients with AF, abnormal P‐SAECG more frequently occurred than in patients without AF (37% vs 15%, P < 0.05) . Patients with AF were older (70 ± 14 vs 56 ± 10, P < 0.001) and had lower left ventricular ejection fraction (42%± 8 vs 49%± 11, P < 0.05) . AF was less common in thrombolysis‐treated patients (47% vs 74%, P <0.05) . Thirty‐day mortality was higher in patients with AF (16% vs 2%, P = 0.05) . Conclusions: An abnormal P‐SAECG may be a predictor of paroxysmal AF in patients with AMI. Advanced age and systolic heart failure were detected as two important clinical risk factors for the development of AF.     

Electrocardiographic criteria for the diagnosis of abnormal hypertensive cardiac phenotypes

This article compared the performance of 18 electrocardiographic (ECG) left ventricular hypertrophic (LVH) criteria and four P‐wave indices for the diagnosis of echocardiographic (ECHO) LVH and left atrial enlargement (LAE), including the deepest S‐wave amplitude added to the S‐wave amplitude of lead V₄ (S_D+SV₄) and P‐wave terminal force in lead V₁ (PTFV₁). A total of 152 middle‐aged hypertensive patients without evident cardiovascular diseases (CVDs) were enrolled. The gold standard for the diagnosis of LVH and LAE was ECHO left ventricular mass index (LVMI) and largest left atrial volume index (LAVI). For the detection of LVH, Sokolow‐Lyon voltage, Cornell voltage, Cornell product, S_D+SV₄, Manning, and R+S in any precordial lead had relatively higher sensitivity, especially S_D+SV₄ criteria. Their combination could further increase sensitivity (43% vs 29% [S_D+SV₄], P = 0.016). PTFV₁ was the only criterion that had significant diagnostic value for ECHO LAE (AUC, 0.68; 95% CI: 0.54‐0.73, P = 0.008). For middle‐aged hypertensive patients without evident cardiovascular diseases, S_D+SV₄ had the highest sensitivity for the diagnosis of LVH and the combination of several ECG LVH criteria might further increase sensitivity. PTFV₁ had significant diagnostic value for ECHO LAE.     

Ventricular Late Potentials Are Associated with the Presence of Viable Myocardium After Anterior Myocardial Infarction

Background: The aim of the study was to evaluate the relationship between myocardial viability (MV) detected by Tl‐201 rest/redistribution protocol (RR‐SPECT) and the presence of ventricular late potentials (VLPs) in acute myocardial infarction (AMI). We analyzed signal‐averaged ECGs (SAECGs) in 28 patients (age 57 ± 10 years) with a first anterior AMI within 48 hours of symptoms (SAECG1) and prior to discharge (SAECG2). VLPs were defined according to the presence of filtered QRS (QRS‐D) > 114 ms and duration of low amplitude signals (LAS) a 30 ms or root mean square voltage (RMS40) < 25 μ;V, using a 25‐Hz filter, or a duration of LAS > 39 ms or RMS40 < 20 μ;V, using a 40‐Hz filter. RR‐SPECT was performed 17 ± 6 days after AMI. Segments were considered viable when counts were > 60% in early images or when a fill‐in > 10% was detectable on delayed images of those segments with a first count between 31% and 59%. Methods: Patients were divided into two groups: with MV (group 1 = 16 patients) if almost one third of segments appeared to be viable; without MV (group 2 = 12 patients). No difference was found between the two groups in SAECG1, whereas, using a 25‐Hz filter, a greater QRS‐D (106.6 ± 13.5 vs 93.5 ± 6 ms) and LAS (31.2 ± 8.7 vs 18.1 ± 6.4 ms) as well as a smaller RMS40 (43 ± 33.5 vs 71.3 ± 30.4 μ;V) characterized the SAECG2 of group 1. Sensitivity and specificity of VLPs in detecting MV were 31% and 100%. When using cut‐off values derived from median distribution of the population (QRS‐D & 99 ms, LAS a 24 ms and RMS40 > 51 μ;V), sensitivity raised to 75% and specificity was 92% with a positive and negative predictive value of 92% and 73%. Conclusions: The presence of MV is associated with a greater incidence of VLPs. SAECG performed at the time of discharge may facilitate the identification of patients with μ;V after anterior AMI.