Effects of amiodarone on the P-wave triggered signal-averaged electrocardiogram in patients with paroxysmal atrial fibrillation and coronary artery disease

The electrical substrate of vagal atrial fibrillation as assessed by the signal-averaged electrocardiogram of the P wave

BACKGROUND

The autonomic nervous system is thought to be involved in the initiation of atrial fibrillation (AF). However, there is a distinct entity of vagal AF characterized by episodes occurring at rest, postprandially, or during sleep. The purpose of this study was to compare intraatrial conduction in patients with vagally mediated AF to those with nonvagal AF, using the signal-averaged electrocardiogram (SAECG) of P wave.

METHODS

SAECG of P wave was performed in 58 patients with AF using the Marquette Medical System, and the mean filtered P-wave duration (SAPW) was measured. Nine patients were categorized as having pure vagal AF (Group I), and 42 patients as having nonvagal AF (Group II); the remaining seven patients were excluded from analysis because of incomplete data.

RESULTS

The patients in Group I were significantly younger and more likely to have paroxysmal lone AF, as compared to those in Group II. There was no significant difference in left atrial size and left ventricular function in the two groups. The mean SAPW was significantly shorter in Group I when compared to Group II (118 +/- 5 ms vs 149 +/- 39 ms, P < 0.001). Whereas all patients in Group I had a normal SAPW, 79% of patients in Group II had an abnormal SAPW (P < 0.001). A normal SAPW was significantly predictive of vagal AF independent of other co-variables.

CONCLUSIONS

(1) Patients with vagal AF are younger, and invariably have paroxysmal lone AF. (2) SAPW is normal and significantly shorter in vagal AF when compared to patients with nonvagal AF. (3) This suggests that those in the vagal AF population have normal intraatrial conduction, which has implications for AF ablation in these patients.

Variable interatrial conduction illustrated in a hypertrophic cardiomyopathy population

BACKGROUND

Patients with hypertrophic cardiomyopathy (HCM) have a high incidence of atrial fibrillation. They also have a longer P-wave duration than healthy controls, indicating conduction alterations. Previous studies have demonstrated orthogonal P-wave morphology alterations in patients with paroxysmal atrial fibrillation. In the present study, the P-wave morphology of patients with HCM was compared with that of matched controls in order to explore the nature of the atrial conduction alterations.

METHODS AND RESULTS

A total of 65 patients (45 men, mean age 49 +/- 15) with HCM were included. The control population (n = 65) was age and gender matched (45 men, mean age 49 +/- 15). Five minutes of 12-lead ECG was recorded. The data were subsequently transformed to orthogonal lead data, and unfiltered signal-averaged P-wave analysis was performed. The P-wave duration was longer in the HCM patients compared to the controls (149 +/- 22 vs 130 +/- 16 ms, P < 0.0001). Examination of the P-wave morphology demonstrated changes in conduction patterns compatible with interatrial conduction block of varying severity in both groups, but a higher degree of interatrial block seen in the HCM population. These changes were most prominent in the Leads Y and Z.

CONCLUSION

The present study suggests that the longer P-wave duration observed in HCM patients may be explained by a higher prevalence of block in one or more of the interatrial conduction routes.

Prediction of atrial fibrillation in patients with cardiac dysfunctions†

AIMS

Atrial fibrillation (AF) is a common arrhythmia in advanced heart failure. The occurrence of AF increases the risk of death and hospitalization for patients with heart failure. The results of different studies indicated that patients with paroxysmal AF have a longer filtered P wave duration (FPD), a lower root mean square voltage of the last 20 ms of the P wave (RMS 20), and a lower chemoreflexsensitivity (CHRS). Our study bases on these observations in order to examine the methods for predicting AF in patients with a left ventricular ejection fraction below 40% without a prior documentation of AF.

METHODS AND RESULTS

The ratio between the difference of RR intervals in ECG and venous pO(2) before and after 5-min oxygen inhalation was measured (ms/mmHg) in order to determine the CHRS. A P wave signal-averaged ECG was performed for the measurement of FPD and RMS 20. The measurements were only performed in 94 patients with sinus rhythm. AF occurred during the mean follow-up of 39.9 months in 24 patients (26%). There were no significant differences concerning age, heart diseases, sex, ejection fraction, heart rate, or the use of drugs. The FPD (130.3 +/- 4.2 vs. 118.9 +/- 12.4 ms, P < 0.0001) was significantly longer and the RMS 20 (3.03 +/- 0.95 vs. 3.83 +/- 1.58 microV, P = 0.02) was significantly lower in patients with AF than in sinus rhythm. The CHRS did not differ significantly between both groups (3.57 +/- 1.49 vs. 3.48 +/- 1.62 ms/mmHg, P = 0.81). The chi(2) test showed that the threshold of FPD>or=125 ms and RMS 20 <or=3.3 microV revealed the best predictive value for AF. A stepwise logistic regression analysis of all variables identified the threshold of FPD>or=125 ms and RMS 20 <or=3.3 microV (OR 18.71; 95% CI, 4.85-72.16, P < 0.0001) as independent predictors for AF.

CONCLUSIONS

In summary, our data show that the results of a P wave signal-averaged ECG can predict the risk for new onset of AF in patients with heart failure. The value of signal-averaged FPD is probably the result of reflecting the intra-atrial conduction delay, which is a pathophysiological condition for AF. The CHRS is not a suitable method for predicting AF.

P-wave durations in patients experiencing atrial fibrillation during exercise testing

Augmented sympathoadrenal activity during exercise may contribute to occurrence of various arrhythmias including atrial fibrillation (AF). The prolongation of intraatrial and interatrial conduction times and inhomogeneous propagation of sinus impulses are well-known characteristics of the atrium prone to fibrillate and are evaluated by maximum P-wave duration (P max), P-wave dispersion (PWD). To show the increased P max and PWD values in patients experiencing AF during exercise testing and the role of beta blockade on treatment of exercise-induced AF, 22 of these patients were compared with a control group consisting of 41 patients without AF attacks. P max (p = 0.001) and PWD (p = 0.001) values were significantly higher in patients with AF compared to those without AF. The development of AF during exercise testing was found to be positively correlated with P max (r = 0.87, p < 0.001), PWD (r = 0.83, p = 0.001), and work load (r = 0.34, p = 0.002) and negatively correlated with ejection fraction (r = -0.26, p=0.02). After the treatment with beta-blocking agents for 2 weeks, the decrease in P max and PWD values was accompanied by a much lower prevalence of exercise-induced AF. Consequently, the patients with AF had greater P max and PWD values compared to control subjects, and these simple parameters were well correlated with the occurrence of AF during exercise testing. Furthermore, treatment of these patients with beta blockers would appear to decrease the recurrence of exercise-induced AF and to be associated with a decrease in P-wave durations.

Prediction of Conversion from Paroxysmal to Permanent Atrial Fibrillation

BACKGROUND

Paroxysmal atrial fibrillation (PAF) transits to permanent atrial fibrillation (PEAF). The current study was to determine whether a P wave-triggered P wave signal averaged electrocardiogram (P-SAECG) and chemoreflexsensitivity (CHRS) are useful to predict a conversion to PEAF in patients with PAF.

METHODS

The filtered P wave duration (FPD) and the root mean square voltage of the last 20 ms of the P wave (RMS 20) were measured by P-SAECG. The ratio between the difference of RR intervals in the ECG and venous pO2 before and after 5-minutes oxygen inhalation is measured (ms/mmHg) for the determination of CHRS.

RESULTS

A total of 180 patients with PAF were enrolled and followed for a mean of 22.5 months. PEAF occurred in 38 patients (21%) and these patients had a significantly larger left atrial size (43.2 +/- 4.9 vs. 41.0 +/- 5.4 mm, P = 0.021), a significantly longer FPD (158.8 +/- 18.2 vs. 136.7 +/- 16.6 ms, P < 0.0001), and a significantly lower CHRS (1.96 +/- 0.99 vs. 2.44 +/- 1.19 ms/mmHg, P = 0.024) than patients with PAF. Patients with PEAF tended to have a lower RMS 20 (2.38 +/- 0.65 vs. 2.75 +/- 1.18 microV, P = 0.067) than patients with PAF. The chi(2) test showed that the combination of FPD > or = 145 ms, RMS 20 < or = 3.0 microV, left atrial size > or = 41 mm, and CHRS < or = 2.0 ms/mmHg had the best predictive power for PEAF. Patients who fulfilled these criteria had a 12-fold increased risk for a conversion from PAF to PEAF.

CONCLUSIONS

Our results show that a P-SAECG, an analysis of CHRS, and left atrial enlargement are clinical predictors of a progression from PAF to PEAF.

Long-term outcome after cardioversion of atrial fibrillation: Prediction of recurrence with P wave signal averaged ECG and chemoreflexsensitivity

AIM

The recurrence of atrial fibrillation after cardioversion was a general problem in medical practice.

METHODS

We wanted to test the hypothesis that the recurrence of atrial fibrillation could be predicted by measurements of P wave triggered P wave signal averaged ECG and chemoreflexsensitivity (CHRS) in 118 consecutive patients one day after successful electrical 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) with P wave triggered P wave signal averaged ECG. The CHRS was calculated of a ratio between the difference of RR intervals in ECG and venous pO2 before and after 5-min oxygen inhalation. The pathologic CHRS was predefined as a CHRS below 3.0 ms/mm Hg.

RESULTS

A recurrence of atrial fibrillation was observed in 57 patients (48%) during a 9.3-month follow-up. The left atrial size (41.9+/-4.0 vs. 39.3+/-3.1 mm, P<0.0003) was larger, the FPD (139.6+/-16.0 vs. 118.2+/-14.1 ms, P<0.0001) was longer, the RMS 20 (2.57+/-0.77 vs. 3.90+/-0.99 muV, P<0.0001) and the CHRS (2.66+/-1.18 vs. 4.01+/-1.66 ms/mm Hg, P<0.0001) were lower in patients with recurrence of atrial fibrillation. A cut-off point was defined with FPD > or =126 ms and RMS 20 < or =3.1 muV and could predict atrial fibrillation 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%. Patients with FPD > or =126 ms and RMS 20 < or =3.1 muV had nearly a 7-fold increase risk for recurrence of atrial fibrillation.

CONCLUSION

The recurrence of atrial fibrillation after cardioversion could be detected by P wave signal averaged ECG and an analysis of CHRS. These methods seem to be appropriate to show a delayed atrial conduction and a neurovegetative imbalance which might be possible trigger mechanisms of reinitiating of atrial fibrillation.

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 microV, P < 0.0001). A cutoff point (COP) of FPD > or =126 ms and RMS 20 < or =3.1 microV 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 dispersion and short-term vs. late atrial fibrillation recurrences after cardioversion

BACKGROUND

P wave dispersion has been previously suggested as a potential tool for predicting the risk of recurrence of atrial fibrillation after electrical cardioversion. We investigated whether different P wave dispersion values are associated with recurrence of atrial fibrillation in the short (< or =1 month after cardioversion) and longer term.

METHODS

In 37 patients with long-lasting persistent atrial fibrillation (mean duration 21 +/- 36 months) with (n = 19) or without (n = 18) amiodarone pretreatment as antiarrhythmic prophylaxis, maximum and minimum P wave duration and P wave dispersion were measured 1 min after internal cardioversion.

RESULTS

P wave dispersion was lower in patients with amiodarone pretreatment (28.3 +/- 9.5 vs. 21.9 +/- 7.3 ms, P = 0.029). The subgroups of patients with recurrence of atrial fibrillation at 1 month or in the long-term did not differ from the rest of the study sample regarding age, sex, atrial fibrillation duration, left atrial dimensions or ejection fraction. P wave dispersion was significantly higher in patients with short-term atrial fibrillation recurrence (< or = 1 month) than in the rest of the population. Furthermore, P wave dispersion values >25 ms were associated with a higher short-term relapse rate. No significant relation was present in the long-term.

CONCLUSIONS

Our results suggest that P wave dispersion analysis immediately after internal cardioversion may help predict short-term recurrences of atrial fibrillation. These findings may be related to different mechanisms and predisposing factors for short-term and late recurrences. The long-term predictive value of serial evaluations of P wave dispersion during follow-up deserves investigation.

Analysis of the surface electrocardiogram for monitoring and predicting antiarrhythmic drug effects in atrial fibrillation

Specific antiarrhythmic therapy with class I and III drugs for atrial fibrillation (AF) conversion and prevention of its recurrence is frequently utilized in clinical practice. Besides being only moderate effective, the utilization of antiarrhythmic drugs may be associated with serious side effects. In the clinical setting it is difficult to directly evaluate the effects of antiarrhythmic drugs on the individual patient's atrial electrophysiology, thereby predicting their efficacy in restoring and maintaining sinus rhythm. Analysis of the surface electrocardiogram in terms of P-wave signal averaged ECG during sinus rhythm and spectral characterization of fibrillatory waves during AF for evaluation of atrial antiarrhythmic drug effects is a new field of investigation. Both techniques provide reproducible parameters for characterizing atrial electrical abnormalities and seem to contain prognostic information regarding antiarrhythmic drug efficacy. Further research is needed which elucidates the most challenging clinical questions in AF management whom to place on antiarrhythmic drug treatment and what antiarrhythmic drug to prescribe. Analysis of the surface ECG might have the potential to answer these questions.

P wave signal averaged ECG and chemoreflexsensitivity in paroxysmal atrial fibrillation

Detailed analysis of the QRS-complex and autonomic dysfunction can identify patients at risk to suffer from ventricular arrhythmias. To determine whether patients at risk for paroxysmal atrial fibrillation (PAF) could be identified while in sinus rhythm, a P wave triggered signal averaged ECG and an analysis of the autonomic function by chemoreflexsensitivity (CHRS) were examined. The ratio between the difference of RR intervals in the ECG and the venous partial pressure of oxygen before and after 5-min oxygen inhalation was measured for the determination of CHRS. We examined 224 patients (group A) who suffered from PAF, 250 patients (group B) without arrhythmic history and 30 young volunteers (group C). The filtered P wave duration (FPD) was significantly longer in group A than in group B (140.9+/-21.0 vs. 118.2+/-9.4 ms, p<0.0001) or C (105.2+/-14.1 ms, p<0.0001) while the root mean square voltage of the last 20 ms of the P wave (RMS 20) was significantly lower in group A than in group B (2.68+/-1.12 vs. 4.06+/-1.57 microV, p<0.0001) or C (3.97+/-1.36 microV, p<0.0001). Atrial late potentials (ALP) were defined as a FPD>120 ms and a RMS 20< or =3.5 microV. ALP could identify patients of group A with a specificity of 78% and a sensitivity of 83%. Patients with PAF (2.32+/-1.15 ms/mm Hg) showed a significantly lower CHRS than group B (4.14+/-1.58 ms/mm Hg, p<0.0001) or group C (4.98+/-1.51 ms/mm Hg, p<0.0001). The sensitivity for the presence of atrial fibrillation was 71% for a CHRS below 3.0 ms/mm Hg with a specificity of 70%. A combination of both methods showed a specificity of 85% and a sensitivity of 65% when ALP and pathological CHRS were present. The results of our study suggest that risk of atrial fibrillation could be detected by P wave signal averaged ECG and CHRS. An analysis of CHRS seems to be an appropriate method to demonstrate a neurovegetative imbalance, which might be one possible trigger mechanism.

An evaluation of postoperative P-wave variables after cardiothoracic surgery

Postoperative atrial fibrillation is common after cardiac surgery. Prediction of which patients will develop postoperative atrial fibrillation would be clinically useful. Increased P-wave duration, suggesting atrial conduction delay and measured from preoperative electrocardiograms, predicts postoperative atrial fibrillation. However, postoperative P-wave duration has not been evaluated after cardiac surgery. In this study, we evaluated postoperative P-wave variables (maximum P-wave duration and P-wave dispersion) over 5 days in cardiac surgery patients receiving amiodarone, pacing or no atrial fibrillation prophylaxis. P-wave variables gradually shortened as time passed from surgery. Amiodarone did not shorten P-wave measurements throughout therapy, while pacing shortened P-waves in the immediate postoperative period; however, shortening was not sustained. P-waves did not differ between those who did and did not develop atrial fibrillation with amiodarone or pacing. Our findings suggest that atrial conduction delay resulting from cardiothoracic surgery tends to resolve over time and may not play a critical role in the etiology of postoperative atrial fibrillation.

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.