Age and sex differences in the P-wave signal-averaged electrocardiogram in a Japanese study population

Ventricular late potentials and myocardial fibrosis in hypertrophic cardiomyopathy

AIMS

Ventricular late potentials (VLPs) represent delayed conduction due in part to myocardial fibrosis. We sought to examine the relationship of signal-averaged electrocardiography findings with myocardial fibrosis as assessed by cardiac magnetic resonance (CMR) in patients with hypertrophic cardiomyopathy (HCM).

METHODS

This study consisted of 41 HCM patients with sinus rhythm who had undergone risk assessment including CMR and signal-averaged electrocardiography such as VLPs, filtered QRS duration, low amplitude signal duration of the terminal filtered QRS below 40 μV (LAS), and root mean square voltage of the late 40 ms of the filtered QRS (RMS). The concordance rate between VLPs and myocardial fibrosis as assessed by CMR was examined.

RESULTS

Late gadolinium enhancement (LGE) on CMR was detected in 13 patients, and VLPs were detected in 14. Filtered QRS duration, LAS, RMS, and VLPs were not associated with LGE. The results of LGE and VLPs were concordant in 26 patients, whereas 15 exhibited discordance. Patients with discordance had a higher maximum wall thickness (24.1 ± 4.0 mm versus 21.0 ± 5.9 mm, p < 0.05), higher LGE volume (2.3 ± 1.2 g/cm versus 0.0 ± 0.8 g/cm, p < 0.01), lower LGE volume/the total number of sites with LGE (1.5 ± 0.7 versus 3.1 ± 2.8, p < 0.01), and predominant LGE location of the interventricular septum and anterior wall (60% versus 8%, p < 0.01) than patients with concordance.

CONCLUSION

VLPs were not a reliable marker for the detection of myocardial fibrosis as assessed by LGE on CMR in our cohort of patients with HCM.

CONDENSED ABSTRACT

Ventricular late potentials on signal-averaged electrocardiography represent delayed conduction due in part to myocardial fibrosis but were not an alternative to cardiac magnetic resonance for detecting myocardial fibrosis in patients with hypertrophic cardiomyopathy.

Evolution of P-wave morphology in healthy individuals: a 3-year follow-up study

BACKGROUND

Orthogonal P-wave morphology in healthy men and women has been described using unfiltered signal-averaged technique and holds information on interatrial conduction. The stability of P-wave morphology in healthy subjects over time is not fully known.

METHODS

Sixty-seven healthy volunteers were investigated (29 males, aged 63 +/- 14 years, 48 females, 60 +/- 13 years). Orthogonal lead data (X, Y, and Z) were derived from standard 12-lead ECGs (recording length 6 minutes, sampling rate 1kHz, resolution 0.625 muV) recorded at baseline (BL), and 3 years later at follow-up (FU). P waves were then signal-averaged and analyzed regarding P-wave morphology, locations of maxima, minima, zero-crossings, and P-wave duration (PWD).

RESULTS

No differences of P-wave variables were observed at FU compared to BL, including PWD (127 +/- 12 vs 125 +/- 14 ms at BL and FU, respectively, n.s.). In 59 of the 67 subjects (88%), the P-wave morphology was unaltered at FU. However, in the remaining eight cases a distinctively different morphology was observed. The most common change (P=0.030) was from negative polarity to biphasic (-/+) in Lead Z (n=5). In one case the opposite change was observed and in two cases transition into advanced interatrial block morphology was evident at FU.

CONCLUSIONS

In the majority of healthy subjects, P-wave morphology is stable at 3-year FU. Subtle morphological changes, observed principally in Lead Z, suggest variation of interatrial conduction. These changes could not be detected by measuring conventional PWD that remained unchanged in the total population.

Improvement of atrial signal-averaged electrocardiographic abnormalities after radiofrequency catheter ablation in persistent atrial flutter

It has been reported that abnormalities of atrial conduction are present in patients with atrial flutter (AFL). We analyzed the P wave signal-averaged ECG (PSE) in patients after cardioversion of chronic AFL by radiofrequency catheter ablation (RFCA) to determine whether abnormalities of atrial conduction exist in patients with AFL and whether they recover. We studied 11 patients undergoing ablation of persistent AFL (AFL group), 11 patients with paroxysmal AFL (PAFL group), and 14 patients without any evidence of arrhythmias (control group). The PSEs were recorded 1 day, 7 days, and 1 month after RFCA. The filtered P wave duration (FPD) was calculated from the PSE recording. The FPD correlated with interatrial conduction time (r = 0.644) and left atrial dimension (r = 0.675) in combined assessment of the AFL and PAFL groups. The FPD was longer in the AFL group 1 day (165 +/- 14 ms, P < 0.001) and 1 month (150 +/- 18 ms, P < 0.05) after RFCA than in the control group (134 +/- 10 ms). Our findings suggest that atrial conduction abnormalities detected by PSE are present in patients with persistent AFL and improve 1 month after cardioversion.