Assessment of P-wave dispersion on 12-lead electrocardiography in students who exercise regularly

Background: P-wave dispersion, an electrocardiographic marker, is an independent predictor of atrial fibrillation. P-wave dispersion is associated with inhomogeneous and discontinuous propagation of sinus impulses. The aim of this study was to investigate P-wave dispersion in students who apply for registration to School of Physical Education and Sports.
Methods: Totally 984 students (810 boys [mean age: 19.8 ± 2.0 years] and 174 girls [mean age: 19.0 ± 1.8 years]) who applied for registration to School of Physical Education and Sports with a training history of some years were included in the study. P-wave duration was calculated in all 12 leads of the surface electrocardiography, which were simultaneously recorded. The difference between P maximum and P minimum durations was defined as P-wave dispersion.
Results: Age, body mass index (BMI), systolic blood pressure, diastolic blood pressure, P-wave maximal duration, and P-wave dispersion were increased in boys as compared with girls. Of age (P = 0.53), systolic blood pressure (P = 0.42), diastolic blood pressure (P = 0.50), pulse pressure (P = 0.73), gender, heart rate, and BMI tested with univariate linear regression analysis in all subjects; only gender (P < 0.001), BMI (P = 0.01), and heart rate (P = 0.02) were associated with P-wave dispersion (F = 5.16, P < 0.001, R²= 0.03).
Conclusions: P-wave dispersion was increased in boys as compared with girls who exercise regularly. P-wave dispersion is affected by gender, BMI, and heart rate in healthy students.     

P wave dispersion on 12-lead electrocardiography in patients with paroxysmal atrial fibrillation

The prolongation of intraatrial and interatrial conduction time and the inhomogeneous propagation of sinus impulses have been shown in patients with atrial fibrillation. Recently P wave dispersion (PWD), which is believed to reflect inhomogeneous atrial conduction, has been proposed as being useful for the prediction of paroxysmal atrial fibrillation (PAF). Ninety consecutive patients (46 men, 44 women; aged 55 +/- 13 years) with a history of idiopathic PAF and 70 healthy subjects (42 men, 28 women; mean age 53 +/- 14 years) were studied. The P wave duration was calculated in all 12 leads of the surface ECG. The difference between the maximum and minimum P wave duration was calculated and this difference was defined as P wave dispersion (PWD = Pmax-Pmin). All patients and controls were also evaluated by echocardiography to measure the left atrial diameter and left ventricular ejection fraction (LVEF). There was no difference between patients and controls in gender (P = 0.26), age (P = 0.12), LVEF (66 +/- 4% vs 67 +/- 5%, P = 0.8) and left atrial diameter (36 +/- 4 mm vs 34 +/- 6 mm, P = 0.13). P maximum duration was found to be significantly higher in patients with a history of PAF (116 +/- 17 ms) than controls (101 +/- 11 ms, P < 0.001). P wave dispersion was also significantly higher in patients than in controls (44 +/- 15 ms vs 27 +/- 10 ms, P < 0.001). There was a weak correlation between age and P wave dispersion (r = 0.27, P < 0.001). A P maximum value of 106 ms separated patients with PAF from control subjects with a sensitivity of 83%, a specificity of 72%, and a positive predictive accuracy of 79%. A P wave dispersion value of 36 ms separated patients from control subjects with a sensitivity of 77%, a specificity of 82%, and a positive predictive accuracy of 85%. In conclusion, P maximum duration and P wave dispersion calculated on a standard surface ECG are simple ECG markers that could be used to identify the patients with idiopathic paroxysmal atrial fibrillation.     

QT dispersion measured by automatic computerized 12-lead electrocardiography contributes significantly to detection of left ventricular hypertrophy in Japanese patients

This study assessed the diagnostic value of QT dispersion for left ventricular hypertrophy (LVH) as determined by echocardiography. The QT and QRS interval parameters were determined automatically using computerized 12-lead electrocardiography in 153 Japanese out-patients. Corrected QT dispersion (QTcD) and maximal QRS duration (MaxQRS) were significantly correlated with left ventricular mass index. The sum of QTcD and MaxQRS showed the highest correlation with left ventricular mass index among QT and QRS interval parameters and their combinations. The cut-off points for LVH discrimination in this study were different to those reported in Western, mainly Caucasian, populations, suggesting the need for ethnicity-specific LVH detection criteria. A scoring system derived from multiple logistic regression analysis, employing a combination of QTcD, QRS time-voltage product and ST-T change, showed a specificity of 86.3%. It was concluded that QTcD, in addition to QRS time-voltage product and ST-T change, improved the detection of LVH.     

Real-time 12-lead high-frequency QRS electrocardiography for enhanced detection of myocardial ischemia and coronary artery disease

Several studies have shown that diminution of the high-frequency (HF; 150-250 Hz) components present within the central portion of the QRS complex of an electrocardiogram (ECG) is a more sensitive indicator for the presence of myocardial ischemia than are changes in the ST segments of the conventional low-frequency ECG. However, until now, no device has been capable of displaying, in real time on a beat-to-beat basis, changes in these HF QRS ECG components in a continuously monitored patient. Although several software programs have been designed to acquire the HF components over the entire QRS interval, such programs have involved laborious off-line calculations and postprocessing, limiting their clinical utility. We describe a personal computer-based ECG software program developed recently at the National Aeronautics and Space Administration (NASA) that acquires, analyzes, and displays HF QRS components in each of the 12 conventional ECG leads in real time. The system also updates these signals and their related derived parameters in real time on a beat-to-beat basis for any chosen monitoring period and simultaneously displays the diagnostic information from the conventional (low-frequency) 12-lead ECG. The real-time NASA HF QRS ECG software is being evaluated currently in multiple clinical settings in North America. We describe its potential usefulness in the diagnosis of myocardial ischemia and coronary artery disease.     

Influence of cardiac autonomic neuropathy on heart rate dependence of ventricular repolarization in diabetic patients

OBJECTIVE: Prolongation of the QT interval and increased QT dispersion are associated with a poor cardiac prognosis. The goal of this study was to assess the long-term influence of the autonomic nervous system on the heart rate dependence of ventricular repolarization in patients with diabetic autonomic neuropathy (DAN). RESEARCH DESIGN AND METHODS: We studied 27 subjects (mean age 51.8 years) divided into three age- and sex-matched groups: nine control subjects, nine diabetic subjects with DAN (mostly at a mild stage; DAN+), and nine diabetic subjects without DAN (DAN-). DAN was assessed on heart rate variations during standard maneuvers (Valsalva, deep-breathing, and lying-to-standing maneuvers). No subject had coronary artery disease or left ventricular dysfunction or hypertrophy, and no subject was taking any drugs known to prolong the QT interval. All subjects underwent electrocardiogram and 24-h Holter recordings for heart rate variations (time and frequency domain) and QT analysis (selective beat averaging QT/RR relation, nocturnal QT lengthening). RESULTS: Rate-corrected QT intervals (Bazett formula) did not differ significantly between the three groups. The diurnal and nocturnal levels of low frequency/high frequency, an index of sympathovagal balance, were significantly reduced in DAN+ subjects. Using the selective beat-averaging technique, a day-night modulation of the QT/RR relation was evidenced in control and DAN- subjects. This long-term modulation was significantly different in DAN+ subjects, with a reversed day-night pattern and an increased nocturnal QT rate dependence. CONCLUSIONS: In diabetic patients with mild parasympathetic denervation, QT heart rate dependence was found to be impaired, as determined by noninvasive assessment using Holter data. Analysis of ventricular repolarization could represent a sensitive index of the progression of neuropathy. The potential prognostic impact of a reversed day-night pattern with steep nocturnal QT/RR relation still remains to be defined.     

Differential diagnosis of slow/slow atrioventricular nodal reentrant tachycardia from atrioventricular reentrant tachycardia using concealed posteroseptal accessory pathway by 12-lead electrocardiography

Slow pathways are used as both antegrade and retrograde conduction pathway in slow/slow atrioventricular nodal reentrant tachycardia (SS-AVNRT), and patients with SS-AVNRT have tachycardia ECGs mimicking atrioventricular reentrant tachycardia using concealed posteroseptal accessory pathway (PS-AVRT). Therefore, SS-AVNRT can be misdiagnosed as PS-AVRT, and the differential diagnosis is clinically important. Standard 12-lead ECGs during tachycardia were analyzed in patients with SS-AVNRT (n = 10) and PS-AVRT (n = 10). All these patients were diagnosed by electrophysiological study and underwent successful catheter ablation. Differences of the RP' intervals (dRP') between V1 and the inferior leads were evaluated. SS-AVNRT had significantly longer RP' intervals measured in V1 (167 +/- 25.2 vs 137 +/- 26.8 ms, SS-AVNRT vs PS-AVRT, respectively, P = 0.02), longer dRP' between V1 and II (dRP'[V1-II], 37 +/- 14 vs 17 +/- 6.7 ms, P = 0.0007), longer dRP'[V1-III] (39 +/- 14 vs 17 +/- 9.9 ms, P = 0.0011), and longer dRP'[V1-aVF] (39 +/- 13 vs 20 +/- 9.5 ms, P = 0.0008). The following criteria were suggested for differential diagnosis of SS-AVNRT from PS-AVRT: dRP'[V1-II] >25 ms (sensitivity and specificity: 80% and 100%, respectively), dRP'[V1-III] >23 ms (90% and 90%), dRP'[V1-aVF] >30 ms (90% and 90%). Differences of the RP' intervals between V1 and the inferior leads in the tachycardia ECGs were useful for differential diagnosis of SS-AVNRT from PS-AVRT.     

Spatial distribution of repolarization times in patients with coronary artery disease

The potential clinical value of QT dispersion (QTd), a measure of the interlead range of QT interval duration in the surface 12-lead ECG, remains ambiguous. The aim of the study was the temporal and spatial analysis of the QT interval in healthy subjects and in patients with coronary artery disease (CAD) using magnetocardiography (MCG) and surface ECG. Standard 12-lead ECG and 37-channel MCG were performed in 20 healthy subjects, 23 patients with CAD without prior myocardial infarction (MI), 31 MI patients and 11 MI patients with ventricular tachycardia (VT). QTd was increased in CAD without MI compared to normals (ECG 46.1 +/- 6.0 vs 42.8 +/- 5.0, P < 0.05; MCG 66.8 +/- 20.3 vs 49.7 +/- 10.8, P < 0.01) and in VT compared to MI (ECG 66.8 +/- 16.5 vs 51.9 +/- 16.6, P < 0.05; MCG 93.6 +/- 29.6 vs 66.8 +/- 20.8, P < 0.005). In MCG, spatial distribution of QT intervals in patient groups differed from those in healthy subjects in three ways: (1) greater dispersion, (2) greater local variability, and (3) a change in overall pattern. This was quantified on the basis of smoothness indexes (SI). Normalized SI was higher in CAD without MI compared to normals (3.8 +/- 1.1 vs 2.7 +/- 0.6, P < 0.001) and in VT compared to MI (6.4 +/- 1.6 vs 4.2 +/- 1.4, P < 0.0005). For the normal-CAD comparison a sensitivity of 74% and a specificity of 80% was obtained, for MI-VT, 100% and 77%, respectively. The results suggest that examining the spatial interlead variability in multichannel MCG may aid in the initial identification of CAD patients with unimpaired left ventricular function and the identification of post-MI patients with augmented risk for VT.     

Increased heterogenity of ventricular repolarization in obese nonhypertensive children

Objective: Obese children, without arterial hypertension, may be a unique clinical opportunity to evaluate the effect of obesity, per se, on ventricular repolarization, excluding the influence of possible comorbidities. The QTc dispersion (QTc‐d), JTc dispersion (JTc‐d), and transmural dispersion of repolarization (TDR) have been suggested to be electrocardiographic indexes reflecting the physiological variability of regional ventricular repolarization. The aim of our study is to define the effects of obesity on the ventricular repolarization in obese children who have no other clinically appreciable cause of heart disease. Methods: The study involved 70 subjects (48 male, 22 female), with a mean age (± standard deviation) of 13 ± 2 years. A total of 35 individuals were obese (Group A: 24 male, 11 female, mean body mass index [BMI] of 38.2 ± 5.8 kg/m²), and 35 participants were healthy lean children (Group C: 24 male, 11 female, mean BMI of 22.3 ± 0.3 kg/m²). Heart rate; QRS duration; maximum and minimum QT interval; and QTc‐d, JTc‐d, and TDR measurement were performed. Results: Compared with the healthy control group, obese children presented increased values of the QTc‐d, JTc‐d, and TDR (31.1 ± 10.6 vs 46.2 ± 15.3 ms, P < 0.003; 29.8 ± 8.5 vs 40.1 ± 10.3 ms, P < 0.04; 83.2 ± 13.5 vs 100.7 ± 16.3 ms, P < 0.05). A statistically significant correlation was found between the values of QTc‐d, insulin serum concentration (r = 0.46, P = 0.04), and homeostasis model assessment of insulin resistance (r = 0.34, P = 0.03). Conclusions: Our data suggest that obese nonhypertensive children have an increased ventricular repolarization heterogeneity in relation to controls. (PACE 2010; 33:1533–1539)     

Usefulness of synthesized 18-lead electrocardiography in the diagnosis of ST-elevation myocardial infarction: A pilot study

Objective

This was a pilot retrospective case-series study performed to investigate whether synthesized 18-lead electrocardiogram (ECG) could improve the accuracy of infarction site diagnosis in patients presenting with ST-elevation myocardial infarction (STEMI).

Prehospital recognition of AMI using independent nurse/paramedic 12-lead ECG evaluation: Impact on in-hospital times to thrombolysis in a rural community hospital

Because the benefits from thrombolytic therapy in acute myocardial infarction (AMI) are time dependent, multiple strategies have been devised to speed therapy. This study sought to determine whether hospital-based nurse and paramedic advanced life support (ALS) providers could be trained to independently evaluate (sight read) a prehospital 12-lead electrocardiogram (ECG) for the presence of AMI as part of a protocol designed to speed in-hospital administration of thrombolytic agents. Providers were required to determine on the basis of a protocol (1) whether or not AMI was present, and (2) whether or not thrombolytic therapy was indicated. Providers then radioed their impression to the emergency department (ED) and initiated a protocol to prepare identified candidates for thrombolysis. The final decision to initiate thrombolytic therapy was made by the ED physician after patient arrival at the hospital. One hundred fifty-five patients with chest pain were studied. Twenty-one (13.5%) were ultimately proven in-hospital to have AMI. Providers were able to recognize AMI in 17 of 21. Four of 21 did not meet ECG criteria for AMI on the field ECG, but were categorized as having a high index of suspicion for AMI by providers. There were no false-positive diagnoses. Fourteen patients (9%) received thrombolytic therapy. In-hospital times to administration of thrombolytic therapy decreased to an average of 22 ± 13.8 minutes in the studied group compared with a historical control group average of 51 ± 50 minutes. It is concluded that hospital-based paramedics and nurses can successfully be taught to evaluate (ie, sight read) a prehospital ECG for the presence of AMI with accuracy. A prehospital chest pain protocol using a field ECG can speed in-hospital administration of thrombolytic therapy to the extent that field administration of thrombolytic agents may not significantly improve times to administration of therapy when transport times are similar to those of this study.     

Risk markers of sudden cardiac death in standard 12-lead electrocardiograms

Abstract The annual incidence of sudden cardiac death (SCD) is estimated at 1 per 1,000 for adults over the age of 35 years, and 1 per 100,000 for adolescents and young adults. Although the overall incidence of unexpected SCD among previously healthy persons is small, the emotional impact of these events is devastating. The 12-lead electrocardiogram (ECG) has been used as a risk assessment tool from healthy occupational applicants and athletes to patients with cardiovascular disorders. The ECG is also routinely recorded in the majority of patients hospitalized for non-cardiovascular causes. Thus, it is a widely used tool intended for identification of unsuspected heart disease generally, as well as for diagnosing specific disorders predisposing to fatal arrhythmias in subjects who have not experienced such events but who are at increased risk. Recognition of specific ECG features is of importance for prevention of SCD in asymptomatic persons. The purpose of this review is to catalog the disorders associated with SCD that may be reflected in 12-lead ECGs seen in office or hospital practices and to discuss their prevalence and the magnitude of risks. The focus is on ECG findings suggesting increased SCD risk among the asymptomatic subjects without previously diagnosed cardiac disease.     

Right ventricular alterations in scuba divers: findings on electrocardiography and echocardiography

BACKGROUND: Scuba diving imposes uncommon environmental stresses. This study assesses the effects of recreational scuba diving on the electrocardiogram (ECG) and echocardiogram and compares them with those of normal controls. METHODS: We studied 50 recreational scuba divers and 50 age-matched and sex-matched normal control subjects. Each subject had a medical history, physical examination, resting 12-lead ECG, and transthoracic echocardiogram. RESULTS: Electrocardiographic findings occurring significantly more frequently in scuba divers than in controls were sinus bradycardia, sinus arrhythmia, QRS duration (> or = 0.10 sec, right axis duration and R > or =S in V2. The mean right ventricular internal dimension (RVID) was significantly larger in divers than in controls. High-normal RVID (2.0 to 2.3 cm) occurred significantly more regularly in divers than in controls (10 vs 1). CONCLUSION: Recreational scuba diving produced right ventricular alterations characterized by chamber dilation and electrocardiographic signs of right ventricular hypertrophy, sinus bradycardia, and arrhythmia.     

Risk markers of sudden cardiac death in standard 12-lead electrocardiograms

Abstract

The annual incidence of sudden cardiac death (SCD) is estimated at 1 per 1,000 for adults over the age of 35 years, and 1 per 100,000 for adolescents and young adults. Although the overall incidence of unexpected SCD among previously healthy persons is small, the emotional impact of these events is devastating. The 12-lead electrocardiogram (ECG) has been used as a risk assessment tool from healthy occupational applicants and athletes to patients with cardiovascular disorders. The ECG is also routinely recorded in the majority of patients hospitalized for non-cardiovascular causes. Thus, it is a widely used tool intended for identification of unsuspected heart disease generally, as well as for diagnosing specific disorders predisposing to fatal arrhythmias in subjects who have not experienced such events but who are at increased risk. Recognition of specific ECG features is of importance for prevention of SCD in asymptomatic persons. The purpose of this review is to catalog the disorders associated with SCD that may be reflected in 12-lead ECGs seen in office or hospital practices and to discuss their prevalence and the magnitude of risks. The focus is on ECG findings suggesting increased SCD risk among the asymptomatic subjects without previously diagnosed cardiac disease.     

Dispersion of ventricular repolarization and ventricular fibrillation in left ventricular hypertrophy: influence of selective potassium channel blockers

This study tested the hypothesis that combination ion channel blockers of the transient outward current (I(to)) and the rapid component of the delayed rectifying current (I(Kr)) would produce greater prolongation of the ventricular action potential duration (APD) and increased dispersion of the APD in hypertrophied hearts compared with control hearts. Isolated rabbit hearts were studied 48 +/- 5 days postabdominal aortic banding. Left ventricular endocardial and epicardial APDs were significantly greater at baseline in the hypertrophied group than in controls (P <.05). The magnitude of APD prolongation induced by the I(to) blocker 4-aminopyridine (4-AP) and combination 4-AP and the I(Kr) blocker dofetilide was greater in the hypertrophied hearts than in the normal hearts (P <.01). Mean APD dispersion was significantly greater in the hypertrophied group than in the control hearts at baseline (P <.05). 4-AP increased APD dispersion by a similar magnitude in the hypertrophied hearts (10 +/- 10 ms) and the control hearts (8 +/- 8 ms, P = NS), whereas the combination 4-AP and dofetilide increased APD dispersion by a greater magnitude in the hypertrophied hearts (41 +/- 28 ms) than the control hearts (21 +/- 11 ms, P <.05). Ventricular fibrillation occurred spontaneously in four hypertrophied hearts (40%) during combination drug perfusion and in none of the control hearts (P <.05). Thus, combination I(to) and I(Kr) blockers cause greater prolongation APD and increased APD dispersion in left ventricular hypertrophy, and this is associated with the development of ventricular fibrillation.     

Detection of repolarization abnormalities in patients with cardiomyopathy using current vector mapping technique on magnetocardiogram

Objectives: We have previously developed current vector maps of tangential components on the magnetocardiogram (MCG) to obtain cardiac current distribution images. The present study was conducted to detect repolarization abnormalities in patients with cardiomyopathy using the current vector map. Subjects and methods: Thirteen patients with cardiomyopathy (nine males and four females aged 7–16 years, mean, 11.5 ± 3.1 years, ±SD), and 15 age- and sex-matched normal subjects were studied. Normal components (Bz) of MCG were measured at rest with a multi-channel superconducting quantum interface device (SQUID) system, and differentiated in the tangential direction to obtain current vector maps. Homogeneity of current in the heart during repolarization was investigated. The direction of the maximum current vector was also calculated in each case. Results: In all normal subjects, the current vector consistently showed a left downward direction on the frontal chest plane during the repolarization process. On the other hand, 8 out of 13 patients with cardiomyopathy showed different patterns; four of these patients showed multi-dipoles, and the other four showed a shift in the current vector direction. One of the eight cases showed no abnormality on electrocardiogram (ECG). Conclusions: Repolarization process in patients with cardiomyopathy was apparently different from those in normal subjects on the current vector map. It was easy to visualize the repolarization process as a projection to the frontal plane, including regional abnormalities, by the current vector maps, which might be more useful for early detection of repolarization abnormalities than ECG.     

极化液对围术期老年患者室性心律失常和心率变异性的影响

目的观察极化液(GIK)对非心脏手术老年患者围术期室性心律失常和心率变异性的影响。方法选取80例非心脏手术老年患者,并将其随机分为观察组和对照组,每组40例。2组患者均于术前给予常规准备,观察组术中根据血糖情况持续大剂量输注GIK。麻醉前及术后12、24、36、48 h应用标准视觉模拟评分法(VAS)对2组患者进行疼痛评分。术前12 h及术后12、24、36、48 h对2组患者发生各类室性心律失常的情况进行比较。对2组患者术前,术后第1、2天的各项心率变异性指标进行比较。结果手术开始时和结束时,观察组患者的血糖水平均显著低于对照组(P0.05);观察组在术后12~24 h、24~36 h和36~48 h的室性早搏次数增加的患者比例显著少于对照组(P0.05);观察组术后第2天的总功率(TP)、极低频功率(VLF)、正常R-R间期的标准差(SDNN)等指标均显著高于对照组(P0.05)。结论在非心脏手术老年患者术中持续大剂量输注GIK能够缓解患者的应激性高血糖症状,降低室性心律失常的发病概率和心率的变异性。