Effects of acute volume changes on P wave characteristics: correlation with echocardiographic findings in healthy men

Establishment and validation of a multivariate predictive model for the efficacy of oral rehydration salts in children with postural tachycardia syndrome

BACKGROUND

The therapeutic effectiveness of the empirical and unselected use of oral rehydration salts (ORS) on postural tachycardia syndrome (POTS) is not satisfactory in children. Therefore, looking for suitable predictors of the therapeutic effects of ORS before treatment is extremely necessary to implement individualised treatment for paediatric patients with POTS.

METHODS

A retrospective case-control analysis of 130 patients (aged 5-18 years) who suffered from POTS with a 3-month treatment of ORS was conducted. A nomogram model was developed in the training set (n = 87) to predict the therapeutic response to ORS. Univariate analysis and logistic regression were applied to select the most useful predictors. ROC curves were applied to evaluate the discriminative performance of the nomogram model. The nomogram was then evaluated by calibration curves and the Hosmer-Lemeshow (H-L) test. The results were further validated using 1000 bootstrap resamples. External validation was performed in an independent validation set (n = 43).

FINDINGS

Among the ten variables with significant differences between the responders and non-responders in univariate analysis, five variables were found to be independently associated factors for ORS therapeutic efficacy among POTS children in the further logistic regression, including mean corpuscular haemoglobin concentration (MCHC), mean corpuscular volume (MCV), mean arterial pressure (MAP) at the first minute of the upright position, urine specific gravity (SG), and P-wave voltage peaking ratio (PWP). The nomogram model was established in the training set (AUC 0.926 [95% CI: 0.865-0.988], yielding a sensitivity of 87.8% and a specificity of 86.8%). The calibration curves showed good agreement between the prediction of the nomogram and actual observation in both the training and validation sets. The nomogram also effectively predicted the external validation set (sensitivity 82.1%, specificity 73.3%, and accuracy 79.1%).

INTERPRETATION

We established a feasible and high-precision nomogram model to predict the efficacy of ORS, which would help implement individualised treatment for children with POTS.

FUNDING

This study was supported by National High-Level Hospital Clinical Research Funding (Multi-centre Clinical Research Project of Peking University First Hospital) (2022CR59).

P-wave voltage and peaking on electrocardiogram in patients undergoing head-up tilt testing for history of syncope

BACKGROUND

Only scanty data are available in the literature on P-wave (PW) morphology at ECG in patients with history of vasovagal syncope undergoing diagnostic functional testing. In this study, we evaluated resting and head-up tilt testing (HUTT) related changes in PW voltage (PWV) and duration (PVD) and their relationship with triggered syncope.

METHODS

55 patients, mean aged 41 ± 19 y (35 F), without patent heart disease or neuropathy, underwent potentiated HUTT according to the Italian protocol. Heart rate (HR), blood pressure (BP), PR-interval, PWV and PWD were measured at rest, 15 min from passive position (15-min) and after nitroglycerine (peak-HR). PW peaking (PWP) was calculated as percent increase in PWV than baseline values. Patients were divided into 2 groups based on tilt-positive (group-A) or negative (group-B) response.

RESULTS

20 patients (36%) entered the group-A, whereas 35 (64%) the group-B. Higher PWV was observed at baseline in group-A (0.147 ± 0.034 mV vs 0.114 ± 0.036 mV in group-B, p=0.001), with no differences in the remaining ECG measurements. BP was lower in group-A than in B, both at 15-min and peak-HR. HUTT-related PWP in lead II (the most significant among all inferior leads) was 31 ± 30% in group-A vs 95 ± 54% in group-B (p<0.0001) at 15-min, and 52 ± 44% vs 112±72% at peak-HR, respectively (p=0.002). 75% of patients with PWP ≤ 50% experienced HUTT-triggered syncope, vs 5% of those with PWP ≥ 100% (p<0.0001).

CONCLUSIONS

This study shows a potential relationship between HUTT-triggered syncope and low or absent PWP, suggesting a role for atrial chamber functional involvement in the mechanisms underlying the vasovagal syncope.

Effect of ethnicity and hypertension on atrial conduction: evaluation with high-resolution P-wave signal averaging

BACKGROUND

Measurements by P-wave signal-averaged electrocardiogram (P-SAECG) of P-wave duration and P-wave voltage integral are higher in patients with atrial fibrillation (AF) than in those with sinus rhythm. Hypertension is perhaps the most common cardiovascular antecedent cause of AF, and particularly a disproportionate cause of morbidity and mortality among blacks. The purpose of this study was to examine the effect of hypertension and ethnicity on P-SAECG parameters in patients without AF.

HYPOTHESIS

It was hypothesized that P-SAECG parameters can identify hypertensives, and are disproportionately higher in hypertensive blacks.

METHODS

In all, 234 normotensives and 84 hypertensives underwent P-SAECG analysis. In an ancillary study group of 34 hypertensive black men, the relationship between severity of hypertension and measured parameters of P-SAECG was evaluated.

RESULTS

Mean filtered P-wave duration and total P-wave voltage integral for normotensives of both ethnic groups were similar. Hypertensive blacks had greater increase in P-wave duration (138 +/- 16 vs. 132 +/- 12ms;p < 0.01, N42:42) and total P-wave voltage integral (922 +/- 285 vs. 764 +/- 198 microV-ms; p < 0.001) than white hypertensives. Filtered P-wave duration and total P-wave voltage integral increased with severity of hypertension.

CONCLUSIONS

Patients at very early stages of hypertension have demonstrable evidence of prolonged atrial conduction by P-SAECG and, thus, cardiac electrical remodeling. P-wave duration and total P-wave voltage integral increase with severity of hypertension. Hypertensive blacks manifest a greater increase in P-SAECG parameters than whites. This may portend an increased cardiovascular risk for black patients with hypertension.

Circadian behavior of P-wave duration, P-wave area, and PR interval in healthy subjects

BACKGROUND

The prolongation of P-wave duration has long been shown to indicate the presence of high risk for atrial fibrillation. The circadian variation of P-wave characteristics and their dynamic adaptation to heart rate changes was not tested before.

METHODS

To evaluate the diurnal pattern of P-wave duration, P area, and PR interval and of their linearly fitted relation with RR interval, 50 healthy volunteers (25 men, mean age 34 +/- 10 years) underwent 24-hour ambulatory electrocardiographic (ECG) recording with digital 12-lead Holter recorders. The median P-wave duration, P area, and PR interval were calculated from the average 12-lead ECG constructed from each 10-second ECG recording. Single harmonic regression analysis was performed to reveal the presence of circadian variation in the aforementioned ECG parameters.

RESULTS

The P area (P < 0.0001, R(2) = 0.78), the PR interval (P < 0.0001, R(2) = 0.92), the P area / RR slope (P < 0.0001, R(2) = 0.55), and the PR/RR slope (P < 0.0001, R(2) = 0.42) showed a highly significant circadian variation while the periodic nature of P-wave duration (P = 0.016, R(2) = 0.32) and of the P duration / RR slope (P = 0.011, R(2) = 0.18) was only indicated by harmonic regression analysis.

CONCLUSIONS

P-wave duration, P area, and PR interval show a significant circadian variation in healthy subjects. The relations between P area/RR,PR/ RR, and P duration/RR also demonstrate a significant diurnal pattern.

Correlation of atrial electrocardiographic amplitude with radiofrequency energy required to ablate cavotricuspid isthmus-dependent atrial flutter

OBJECTIVES

The purpose of this study was to evaluate a possible correlation between atrial ECG amplitude in common atrial flutter (AFL) and radiofrequency (RF) energy required to achieve cavotricuspid isthmus block.

BACKGROUND

The amount of RF delivery required for ablation of typical AFL is variable. This variation has been attributed to the cavotricuspid isthmus anatomy. Atrial ECG amplitude can be a marker of atrial anatomic variations and therefore may correlate with RF duration required to achieve cavotricuspid isthmus block.

METHODS

Seventy consecutive patients were prospectively studied. Ablation of the cavotricuspid isthmus was performed by creating a line of block between the inferior tricuspid annulus and the inferior caval vein using 8-mm-tip electrode catheters. If more than 20 minutes of RF time was required to achieve conduction block, the catheter was changed to an irrigated-tip catheter. Atrial ECG amplitude was assessed in leads II, III, aVF, and aVL.

RESULTS

A total of 14 +/- 11 minutes of RF energy was delivered to achieve block in all patients; 12 patients (8%) required more than 20 minutes. Atrial ECG amplitude showed highly significant correlations with cumulative RF energy (F and P waves in lead II: r = 0.703 and r = 0.737, P < .001). P-wave amplitude <0.2 mV and/or flutter wave amplitude <0.35 mV in lead II have a high negative predictive value to predict <20 min RF delivery (96% and 89% respectively).

CONCLUSIONS

A significant correlation exists between atrial ECG amplitude and amount of RF required to ablate typical AFL. Atrial ECG amplitude may be a surrogate marker of characteristics of isthmus anatomy. These findings may influence the choice of catheter used for cavotricuspid isthmus ablation.

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 (R(2)= 0.11, P = 0.03). However, LAV (R(2)= 0.15, P = 0.009), RAV (R(2)= 0.27, P = 0.0003), and TAV (R(2)= 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.

Noninvasive Assessment of Acute Changes in Atrial Electrophysiology After Cardioversion by Signal-Averaged P-Wave Electrocardiography

BACKGROUND

Atrial remodeling secondary to atrial fibrillation (AF) may be important in the arrhythmogenic process. Unfortunately, the study of electrophysiologic remodeling in humans has been limited by the invasive nature of most tests of electrophysiologic characteristics. We sought to determine whether changes in atrial electrophysiology occur acutely (within the first hour) after cardioversion and whether these changes could be detected noninvasively by measuring the signal-averaged P-wave.

METHODS

The filtered P-wave duration (FPD) was measured by signal-averaged electrocardiography (ECG) at 20 and 60 minutes after cardioversion in 46 patients with AF, and the difference between the two values was calculated. The root-mean-square voltage of the terminal 40 ms of the signal-averaged P-wave at 20 and 60 minutes and the difference between them were also determined.

RESULTS

The FPD at 20 minutes was significantly different from that at 60 minutes (153.0 +/- 19.1 vs 159.7 +/- 24.8 ms; P = 0.02). In a univariate linear regression model, none of the clinical variables studied was significantly associated with the change in FPD. The root-mean-square voltage at 20 minutes was not significantly different from that at 60 minutes (5.8 +/- 3.0 vs 5.5 +/- 2.7; P = 0.14).

CONCLUSIONS

We conclude that significant changes in atrial electrophysiology occur within the first hour after cardioversion of AF. These changes can be detected by measuring the FPD.

P wave analysis indices in young healthy men: data from the digital electrocardiographic study in Hellenic Air Force Servicemen (DEHAS)

P wave analysis from the 12-lead ECG is a recent contribution of noninvasive electrocardiology. P wave analysis indices (maximum and minimum P wave duration, P wave dispersion [Pdis = Pmax-Pmin], adjusted P wave dispersion [APdis = Pdis/square root of measured leads], summated P wave duration [Psum], standard deviation of P wave duration [Psd], mean P wave duration [Pmean]) can predict atrial arrhythmias. However, the definitions of all these indices are based on few studies. The aim of this analysis was to define normal values of these indices and the examine possible associations between P wave indices and clinical variables. The study included 1,353 healthy men, 24 +/- 3 years of age, who answered a questionnaire and underwent a detailed physical examination and a digitized 12-lead surface ECG. All P wave indices were analyzed by two independent investigators. Mean values of the ECG indices were: Pmax: 96 +/- 11 ms, Pmin: 57 +/- 9 ms, Pdis: 38 +/- 10 ms, Psum: 924 +/- 96 ms, Psd: 12 +/- 3, APdis: 11 +/- 3 ms, and Pmean: 77 +/- 8 ms. Age was significantly related with Pmax (r = 0.277, P < 0.01), Pmin (r = 0.255, P < 0.001), Psum (r = 0.074, P < 0.01), and Pmean (r = 0.074, P < 0.01). All ECG indices were significantly associated with the R-R interval, and among each other. This study defined normal indices of wave duration and correlations among them. These markers may play an important predictive role in patients with atrial conduction abnormalities.

Short-, mid-, and long-term reproducibility of the atrial signal-averaged electrocardiogram in healthy subjects: comparison with the conventional ventricular signal-averaged electrocardiogram

Although atrial signal-averaged electrocardiogram (SAECG) has been proposed for noninvasive identification of patients with atrial tachyarrhythmias, the substantial variability of the measurement limits the clinical value. The aim of the study was to assess the short- to long-term reproducibility of atrial SAECG and to compare it to that of the conventional ventricular SAECG in 51 healthy volunteers (30 men; age 32 +/- 8 years). In each subject, SAECG recordings were obtained using MAC-VU electrocardiograph and HiRES and PHiRES software (Marquette Medical Systems) and repeated after 5 minutes, 1 day, 1 week, and 1 month. Automatically detected onset and offset of the filtered QRS complex and P wave were subsequently corrected by two independent observers, and the averaged values were used for the analysis. Conventional ventricular SAECG parameters: filtered QRS duration (QRStot), low amplitude signal duration, and root mean square voltage (RMS) of the terminal 40 ms of QRS, and 5 atrial parameters: filtered P wave duration (Ptot), RMS of the terminal 40, 30, 20 ms, and of the entire P wave were obtained. Relative errors of different pairs of measures were used to assess the intrasubject reproducibility. QRStot and Ptot were the most reproducible parameters. The relative errors after 5 minutes, 1 day, 1 week, and 1 month were 0.8% to 2.4% for QRStot, and 1.3% to 4.2% for Ptot. For RMS voltages, the relative errors exceeded 15% in short-term and 20% in long-term recordings. Although Ptot was statistically less reproducible than QRStot, the reproducibility of the former was good and comparable to that of the QRStot. The reproducibility of the voltage parameters was significantly poorer than that of the duration parameters. The study showed a satisfactory short- and long-term reproducibility of Ptot in the atrial SAECG in healthy subjects. However, low reproducibility of the voltage parameters should be considered in clinical applications.

Signal-averaged P wave in patients with paroxysmal atrial fibrillation

The theoretical and experimental rational of atrial signal-averaged ECG in patients with AF is delay in the intra-atrial and interatrial conduction. Similar to the ventricular signal-averaged ECG, the atrial signal-averaged ECG is an averaging of a high number of consecutive P waves that match the template created earlier P wave triggering is preferred over QRS triggering because of more accurate aligning. However, the small amplitude of the atrial ECG and its gradual increase from the isoelectric line may create difficulties in defining the start point if P wave triggering is used. Studies using P wave triggering and those using QRS triggering demonstrate a prolonged P wave duration in patients with paroxysmal AF. The negative predictive value of this test is relatively high at 60%-80%. The positive predictive value of atrial signal-averaged ECGs in predicting the risk of AF is considerably lower than the negative predictive value. All the data accumulated prospectively on the predictive value of P wave signal-averaging was determined only in patients undergoing coronary bypass surgery or following MI; its value in other patients with paroxysmal AF is still not determined. The clinical role of frequency-domain analysis (alone or added to time-domain analysis) remains undefined. Because of this limited knowledge on the predictive value of P wave signal-averaging, it is still not clinical medicine, and further research is needed before atrial signal-averaged ECG will be part of clinical testing.