Esophageal ECG Research Articles

Fluid Loss during Exercise-Heat Stress Reduces Cardiac Vagal Autonomic Modulation

Sweat-induced fluid loss during prolonged exercise-heat stress can compromise cardiovascular and thermoregulatory function, although its effects on cardiac autonomic modulation remain unclear. We therefore examined heart rate variability (HRV) and recovery (HRRec), as surrogates of cardiac autonomic modulation, during and after prolonged exercise in the heat with and without fluid replacement. Eleven young and healthy men performed 90 min of semi-recumbent cycling in dry heat (40°C; 20% relative humidity) at a fixed rate of metabolic heat production (600 W; ~46% V˙O2peak) followed by 40-min resting recovery without fluid replacement (No-FR; ~3.4% reduction in body mass). On a separate day, participants completed the same protocol with fluid replacement (FR; 500-700 mL timed boluses) to offset sweat losses. Esophageal temperature and ECG were recorded throughout, with measurements analyzed over 10-min averaged epochs during baseline, each 30-min interval during exercise and 20-min interval during recovery. Esophageal temperature and heart rate were elevated in No-FR relative to FR throughout exercise (all P ≤ 0.02). The HRV indices reflecting vagal influence of heart rate including the cardiac vagal index (CVI = log10[16 × SD1 × SD2]) and root-mean-square of successive differences were attenuated throughout exercise relative to baseline in both conditions (all P < 0.05), with the magnitude of the reduction greater in the No-FR condition (all P < 0.05). Further, sample entropy was reduced throughout all time points measured during exercise in the No-FR relative to FR condition (all P ≤ 0.03). Our unique observations indicate that while prolonged exercise heat stress attenuates the vagal influence and complexity of cardiac rhythms, that reduction is further exacerbated by fluid loss, highlighting the importance of fluid replacement in such conditions.

Toward a novel semi-invasive activation mapping tool for the diagnosis of supraventricular arrhythmias from the esophagus.

Supraventricular arrhythmia diagnosis using the surface electrocardiogram (sECG) is often cumbersome due to limited atrial signal quality. In some instances, use of esophageal electrocardiography (eECG) may facilitate the diagnosis. Here, we present a novel approach to reconstruct cardiac activation maps from eECG recordings. eECGs and sECGs were recorded from 19 individuals using standard acquisition tools. From the recordings, algorithms were developed to estimate the esophageal ECG catheter's position and to reconstruct high-resolution mappings of the cardiac electric activity projected in the esophagus over time. Esophageal two-dimensional activation maps were created for five healthy individuals and 14 patients suffering from different arrhythmias. The maps are displayed as time-dependent contour plots, which not only show voltage over time as conventional ECGs, but also the location, direction, and projected propagation speed of the cardiac depolarization wavefront in the esophagus. Representative examples of sinus rhythm, atrial flutter, and ventricular pre-excitation are shown. The methodology presented in this report provides a high-resolution view of the cardiac electric field in the esophagus. It is the first step toward a three-dimensional mapping system, which shall be able to reconstruct a three-dimensional view of the cardiac activation from recordings within the esophagus.

Markers for silent atrial fibrillation in esophageal long-term electrocardiography

PurposeParoxysmal atrial fibrillation (PAF) often remains undiagnosed. Long-term surface ECG is used for screening, but has limitations. Esophageal ECG (eECG) allows recording high quality atrial signals, which were used to identify markers for PAF. MethodsIn 50 patients (25 patients with PAF; 25 controls) an eECG and surface ECG was recorded simultaneously. Partially A-V blocked atrial runs (PBARs) were quantified, atrial signal duration in eECG was measured. ResultseECG revealed 1.8‰ of atrial premature beats in patients with known PAF to be PBARs with a median duration of 853ms (interquartile range (IQR) 813-1836ms) and a median atrial cycle length of 366ms (IQR 282-432ms). Even during a short recording duration of 2.1h (IQR 1.2–17.2h), PBARs occurred in 20% of PAF patients but not in controls (p=0.05). Left atrial signal duration was predictive for PAF (72% sensitivity, 80% specificity). ConclusionseECG reveals partially blocked atrial runs and prolonged left atrial signal duration – two novel surrogate markers for PAF.

Electrodes for Long-Term Esophageal Electrocardiography

The emerging application of long-term and high-quality ECG recording requires alternative electrodes to improve the signal quality and recording capability of surface skin electrodes. The esophageal ECG has the potential to overcome these limitations but necessitates novel recorder and lead designs. The electrode material is of particular interest, since the material has to ensure conflicting requirements like excellent biopotential recording properties and inertness. To this end, novel electrode materials like PEDOT and silver-PDMS as well as established electrode materials such as stainless steel, platinum, gold, iridium oxide, titanium nitride, and glassy carbon were investigated by long-term electrochemical impedance spectroscopy and model-based signal analysis using the derived in vitro interfacial properties in conjunction with a dedicated ECG amplifier. The results of this novel approach show that titanium nitride and iridium oxide featuring microstructured surfaces did not degrade when exposed to artificial acidic saliva. These materials provide low electrode potential drifts and insignificant signal distortion superior to surface skin electrodes making them compatible with accepted standards for ambulatory ECG. They are superior to the noble and polarizable metals such as platinum, silver, and gold that induced more signal distortions and are superior to esophageal stainless steel electrodes that corrode in artificial saliva. The study provides rigorous criteria for the selection of electrode materials for prolonged ECG recording by combining long-term in vitro electrode material properties with ECG signal quality assessment.

The optimal lead insertion depth for esophageal ECG recordings with respect to atrial signal quality

BackgroundDiagnosing supraventricular arrhythmias by conventional long-term ECG can be cumbersome because of poor p-waves. Esophageal long-term electrocardiography (eECG) has an excellent sensitivity for atrial signals and may overcome this limitation. However, the optimal lead insertion depth (OLID) is not known. MethodsWe registered eECGs at different lead insertion depths in 27 patients and analyzed 199,716 atrial complexes with respect to signal amplitude and slope. Correlation and regression analyses were used to find a criterion for OLID. ResultsAtrial signal amplitudes and slopes significantly depend on lead insertion depth. OLID correlates with body height (rSpearman=0.71) and can be estimated by OLID [cm]=0.25*body height[cm]−7cm. At this insertion depth, we recorded the largest esophageal atrial signal amplitudes (1.27±0.86mV), which were much larger compared to conventional surface lead II (0.19±0.10mV, p<0.0001). ConclusionThe OLID depends on body height and can be calculated by a simple regression formula.

Atrial waveform analysis using esophageal long-term electrocardiography reveals atrial ectopic activity

A 59-year-old male patient without the history of heart disease was referred for coronary angiography due to typical chest pain and signs of myocardial ischemia during exercise stress test. On admission, the patient was in sinus rhythm. After successful PCI, the patient was enrolled in a study to investigate esophageal long-term electrocardiography (eECG) comprising simultaneous rhythm monitoring with surface and esophageal leads during 16 h. The surface ECG (sECG) was recorded using a two-channel Holter ECG recorder with a sampling frequency of 1,024 Hz allowing continuous rhythm monitoring for 7 days (Lifecard CF, Spacelabs Healthcare, USA). The eECG was recorded using an esophageal ECG electrode (Esosoft 6S, FIAB, Italy) connected to a dedicated two-channel eECG recorder—a proprietary development—with a sampling frequency of 512 Hz. We registered two bipolar channels (interelectrode spacings of 60 and 15 mm). The eECG was well tolerated; the patient reported only a slight pharyngeal foreign body feeling without any impact on his common daily activities such as eating, talking and sleeping. The sECG was analyzed using an automatic beat classifier system (Pathfinder, Spacelabs Healthcare, USA). The software correctly detected five atrial premature beats (APB’s) but no other atrial arrhythmias. In the eECG, we unmasked another 40 APB’s, as well as 178 episodes with atrial ectopic rhythm [mean duration ± SD 25 ± 31 beats (Fig. 1)]. This report illustrates the limited sensitivity of surface long-term ECG for atrial rhythm disorders. For the sECG, software-based automatic classification of atrial arrhythmias is accomplished by calculating the ratio of the R–Rinterval to be classified and the preceding R–R-interval(s). This quotient is then compared to a coupling interval threshold, e.g., the Pathfinder software uses by default 66 % of the preceding R–R-interval duration. The number of detected atrial arrhythmias strongly depends on this threshold: atrial ectopic beats are only identifiable if they are premature enough as compared to this threshold. The sECG uses R–R-intervals as surrogate markers of the true atrial activity, while morphologic features of atrial signals are not considered. The lack of a direct classifier for atrial arrhythmias is a major limitation of sECG monitoring in cases without evident change in R–R cycle duration. Moreover, reliable detection of atrial arrhythmias is of increasing importance for risk stratification, because it has been shown that excessive supraventricular ectopic activity [1] as well as atrial premature beats [2–4] are associated with an increased risk of stroke and atrial fibrillation. Esophageal electrocardiography may provide an elegant way out by offering excellent atrial signals that additionally allow waveform analysis for the direct and reliable classification of atrial rhythm. Lead movements due to eating or respiration can confound esophageal electrocardiography. We exclude that the morphologic changes are caused by such artifacts for the ClinicalTrials.gov Identifier: NCT01436344.

High-resolution esophageal long-term ECG allows detailed atrial wave morphology analysis in case of atrial ectopic beats

Detection of arrhythmic atrial beats in surface ECGs can be challenging when they are masked by the R or T wave, or do not affect the RR-interval. Here, we present a solution using a high-resolution esophageal long-term ECG that offers a detailed view on the atrial electrical activity. The recorded ECG shows atrial ectopic beats with long coupling intervals, which can only be successfully classified using additional morphology criteria. Esophageal high-resolution ECGs provide this information, whereas surface long-term ECGs show poor atrial signal quality. This new method is a promising tool for the long-term rhythm monitoring with software-based automatic classification of atrial beats.

Esophageal Long-Term ECG Reveals Paroxysmal Atrial Fibrillation

A 79-year-old man was referred for coronary angiography because of atypical chest pain. The patient's medical history included a myocardial infarction 5 years previously and well-controlled arterial hypertension. Three months before this admission he reported atypical chest pain, sometimes associated with palpitations lasting seconds up to a few minutes. Hence, he underwent ambulant 24-hour ECG, which revealed frequent atrial premature beats but no other arrhythmia. On admission, the patient was in sinus rhythm. Echocardiography showed normal ventricular function without structural heart disease. After successful percutaneous transluminal coronary angioplasty, the patient was included in a study …

The combined use of esophageal electrocardiogram and multiple right parasternal chest leads in the diagnosis of PSVT and determination of accessory pathways involved: A new simple noninvasive approach

Introduction Paroxysmal Supraventricular Tachycardia (PSVT) resulting from any cause can at times lead to diagnostic difficulty mainly when due to AVNRT and AVRT. In this study we used a non-invasive approach using esophageal ECG (ECGe) and ECG derived from the various right parasternal chest leads (RPCL) to correctly diagnose the type of PSVT as well the accessory pathways involved in AVRT. Methods and results We studied a total of 161 patients (89 male) all having a history of palpitation. All the patients underwent routine 12 lead ECG, ECGe, RPCL and electrophysiologic study. With use of ECGe and RPCL, 71 (44.1%) were diagnosed as having AVNRT and 90 (55.9%) having AVRT with various accessory pathways compared to only 49 (30.4%) and 22 (13.7%) respectively with routine 12 lead ECG. With combined ECGe and RPCL, 80 (49.7%) showed accessory pathway in the left free wall, 4 (2.5%) showed in the right free wall, 6 (3.7%) septal accessory pathway, 60 (37.3%) in the anterior wall and 30 (18.6%) in the posterior wall. In comparison, EPS could show accessory pathways in the left free wall in 81 (50.3%), in the right free wall in 5 (3.1%), in the septum in 4 (2.5%), in the anterior wall in 53 (32.9%) and in the posterior wall in 37 (23.0%) out of the 161 patients. Conclusions ECGe + RPCL can be used as a reliable noninvasive diagnostic tool to identify the nature of tachycardia and the pathways involved in the reentrant ring of PSVT especially in those with multiple atrioventricular accessory pathways or a combination of atrioventricular accessory pathways and dual atrioventricular nodal pathway.

Esophageal PP intervals for analysis of short-term heart rate variability in patients with atrioventricular block before and after insertion of a temporary ventricular inhibited pacemaker

Heart rate variability (HRV) analysis is a useful method for assessment of the activities of autonomic nervous system. The RR intervals in ECG is measured for this purpose. However, RR intervals are not suitable for HRV analysis in atrioventricular block (AV) block patients with ventricular inhibited (VVI) pacemaker, as the intervals will be fixed by the ventricular pacemaker. Thus we used an esophageal lead to detect PP intervals for analysis of HRV. The aim of this study was to evaluate the short-term HRV by using an esophageal electrode to detect the atrial signal and PP intervals in AV block patients. Fifteen AV block patients before and after temporary VVI pacemaker and 15 subjects with normal AV conduction (control group) were enrolled in this study. The atrial signals from esophageal lead, ECG and intraatrial lead were recorded. The duration was 10 min. We compared correlation coefficient of PP intervals from different leads in AV block patients and the control group. We also compared the PP interval's variability parameters between the control group and AV block patients, before and after insertion of a temporary ventricular inhibited pacemaker. The esophageal PP intervals were excellently correlated with intraatrial AA intervals ( r=0.98±0.01). The HRV using esophageal PP intervals with time domain demonstrated a significant decrease in patients with AV block (standard deviation of all PP intervals (SDNN) (s)=0.022±0.014; percentage difference between adjacent PP intervals that are greater than 50 ms (pNN-50) (%)=0.052±0.038; square root of the mean of squares of differences between duration of neighboring PP intervals (r-MSDD) (s)=0.322±0.082) but this returned to normal after insertion of a temporary ventricular inhibited pacemaker (SDNN (s)=0.035±0.009; pNN-50 (%)=2.540±1.682; r-MSDD (s)=0.542±0.190). However, the ratio of low frequency/high frequency (LF/HF) still increased (LF/HF=4.120±1.802). The result of this short-term HRV analysis suggested that withdrawal of vagal tone or increased sympathetic activity in AV block patients compared with the control group. This appearance was normalized after insertion of a temporary VVI pacemaker. however, abnormal sympathovagal balance still remained.

Wave recognition and use of the intraoperative unipolar esophageal electrocardiogram

Study Objectives: To evaluate the automated determination of onset and offset times and amplitudes of all the PQRST waves from simultaneously recorded surface electrocardiogram (SECG) and unipolar esophageal ECG (EsECG). The occurrence of ST segment deviation is also examined. Design: Prospective, observational study. Setting: University hospital. Patients: 30 patients undergoing coronary artery bypass graft (CABG) surgery. Interventions: SECG and two-lead unipolar EsECG were recorded after induction of anesthesia and before cardiopulmonary bypass (CPB). Measurements and Main Results: The amplitudes of the P and T waves and the ST segment deviation were measured. EsECG had more noise than SECG. Slight movement of the esophageal electrodes occasionally caused substantial changes in the wave amplitudes and ST segment deviation in the unipolar EsECG. The maximum P wave amplitude in EsECG was, on average, 97% greater than the maximum P wave amplitude in SECG. ST segment deviation in EsECG was observed in the absence of ST segment deviation in SECG and vice versa. Conclusions: The recognition and measurement of all the PQRST waves can be improved and automated by simultaneous use of EsECG and SECG. The P wave amplitude is greater in EsECG than in SECG, which may facilitate the identification of supraventricular versus ventricular arrhythmias. ST segment deviation in the unipolar EsECG may not be suitable for the routine detection of ischemia.

Bipolar esophageal electrocardiography by using standard limb leads.

The ear-xiphisternum distance (EXD, the distance from the low edge of the ear to the xiphisternal basis in supine position) was used as a reference value for esophageal catheter insertion. ECGs recorded in the esophagus with bipolar electrocardiography using standard limb lead (ESLL) and conventional unipolar lead (ECUL) were compared. 112 patients with sinus rhythm and 76 patients during paroxysmal supraventricular tachycardia (PSVT) whose P-wave and QRS complex did not overlap were studied. The results suggested that in sinus rhythm the amplitude of the P-wave in ESLL was larger and the T-wave was smaller than in ECUL. During PSVT, the P-wave was much clear and higher in each lead of ESLL than that in ECUL. The ideal range of esophageal ECG recording was situated between the end of EXD and 6.5 cm proximal to it.

The Esophageal-ECG: New applications with a new technique

Introduction: Because of suboptimized techniques, concerning leads and amplification methods, the esophageal ECG was thus only used to detect atrial arrhythmias. The esophageal ECG would be suitable for detecting intraoperative myocardial ischemia. Methods: The esophageal ECG signals are detected with a bipolar esophageal probe. The signals are passed to a new high-resolution preamplifier (frequency range 0.01-2000 Hz), further on to an analog-digital-board and finally are visualized on a PC for definite evaluation. Results: Compared with the surface ECG, the esophageal ECG could detect significantly more ischemic episodes in both, an animal comparison study (93% versus 47%) (n = 18), as well as in coronary artery bypass graft (= CABG) surgery. At the beginning of anesthesia 85 % of the high risk CABG patients showed ischemic episodes with the esophageal ECG (18% detection rate with the surface ECG), which were correlated with an adverse postoperative outcome (p<0.05). In addition to that, 8 of 18 CABG patients had a mean of 483 ± 119 high-amplitude, biphasic atrial components during cardioplegia (on the surface ECG, only one patient showed 26 P-potentials). Such atrial activities, visually not detectable, were correlated with postoperative supraventricular arrhythmias in 88 %. Conclusions: The clinical relevance is that the esophageal ECG represents a convenient technique with high sensitivity, to monitor intraoperative myocardial ischemia and to detect atrial activity during cardioplegia.

Electrocardiographic recording, atrial pacing, and defibrillation in the course of electrophysiologic studies using the esophagus

Background The purpose of this study was to evaluate the use of a new quadripolar esophageal electrode system during electrophysiologic studies, with regard to transesophageal ECG recording, atrial pacing, and countershock of induced sustained ventricular tachyarrhythmias. Methods The esophageal system was electively positioned in 29 patients undergoing electrophysiological studies for investigation of life-threatening ventricular arrhythmias. Results One patient was unable to tolerate the esophageal system after its initial successful placement and the electrode was withdrawn. High-quality esophageal ECG recordings were obtained in the remaining 28 patients. Transesophageal atrial pacing was attempted in four patients and successful capture was achieved in all four patients. During programmed ventricular stimulation, electric countershock was required for termination of five episodes of induced ventricular tachycardia and 10 episodes of induced ventricular fibrillation. Successful transesophageal countershock of the five episodes of ventricular tachycardia and of nine of 10 episodes of ventricular fibrillation were effected, with minimal delay, using a maximal delivered transesophageal energy of 100 J. In one patient with induced ventricular fibrillation, successful transthoracic defibrillation was achieved with a single shock of 200 J delivered energy, transesophageal countershock was not attempted. Conclusions This esophageal system provides high-quality ECG recordings with the facility for atrial pacing. It also permits low-energy transesophageal defibrillation of ventricular tachyarrhythmias and should prove to be a useful adjunct in electrophysiologic studies and resuscitation.

Clinical correlates of dysrhythmias requiring an esophageal ECG for accurate diagnosis in patients with congenital heart disease

Esophageal electrocardiography (EsECG) is a useful adjunct in the diagnosis of dysrhythmias that are difficult to diagnose with a conventional ECG. This study was designed to evaluate which type of dysrhythmias required the EsECG for proper diagnosis and what factors produced the rhythm problems. Sixty-eight pediatric patients undergoing cardiac surgery were studied. After release of the aortic cross-clamp, the cardiac rhythm was analyzed by a standard limb-lead ECG at five-minute intervals. Twenty-six of 68 patients exhibited rhythms during reperfusion that required the EsECG for definitive diagnosis. This group of patients was younger, had longer durations of cardiopulmonary bypass and aortic occlusion, and required more time and interventions to achieve a normal sinus rhythm. The likelihood of difficult dysrhythmias was not related to the type of surgical procedure performed.

Improved diagnosis of cardiac dysrhythmias during stress tests using bipolar esophageal ECG

Improved diagnosis of cardiac dysrhythmias during stress tests using bipolar esophageal ECG

24-hour ambulatory manometry in diagnosis of esophageal motor disorders causing chest pain.

The clinical diagnosis of motor disorders of the esophagus leading to chest pain usually lacks documentation by manometry despite the use of sophisticated equipment as well as pharmacologic manipulation. We have developed an ambulatory manometry system that allows us to monitor motility in the esophagus on an outpatient basis for 24 hours. This method seems well tolerated, and tracings obtained are of excellent quality, allowing careful inspection and evaluation of details. Simultaneous 24-hour esophageal pH and surface ECG recordings were also obtained. We believe the technique, when perfected, will significantly enhance the understanding and documentation of the cause of chest pain in patients with motor dysfunction of the esophagus.

Esophageal ECG recording--a valuable diagnostic tool in dual chamber pacing.

The interpretation of the ECG of a dual chamber pacemaker necessitates the identification of atrial activity. This is a prerequisite for the evaluation of pacemaker function and for the correct adjustment of programmable pulse generators. The assessment of atrial capture in standard 12-lead ECGs is, however, sometimes rather difficult. Esophageal ECG recording by means of a reusable unipolar electrode, inserted transnasally, and connected to a standard ECG recorder, is a simple, rapid and inexpensive method for the reliable identification of P-waves. Clinical examples are presented to illustrate the value of this technique in determining atrial capture and as a tool for the differential diagnosis of pacemaker-involved tachycardias. The use of esophageal ECG recording in the clinical follow-up of patients with dual chamber pacemakers is recommended.

Computer analysis of intraoperative cardiac rhythms using esophageal and surface leads.

Esophageal ECG lead and computer as arrhythmia monitor were elevated in 6 dogs and 23 patients. In dogs arrhythmias were induced by an epinephrine infusion during halothane anesthesia. The computer identified 1858 irregular beats, a cardiologist 2130. Bigeminy was correctly identified 82% of the time, trigeminy 72%, couplets 29%, and ventricular tachycardia 45%. The false positive rate was .03%. In the operating room the monitor identified an average of 44 abnormal beats per patient. In 5 patients junctional rhythm was correctly identified. This study shows the feasibility of using an esophageal ECG lead for computerized ventricular and supraventricular arrhythmia monitoring in the operating room.

New Echocardiographic Observations in a Patient With Dissimilar Atrial Rhythms

A patient with an impure flutter was found to have dissimilar atrial rhythms that were confirmed by direct ECG recordings. Echocardiographic studies disclosed that the a waves on the mitral echocardiogram occurred synchronously with the a waves on the esophageal ECG that, in turn, showed atrial flutter at a rate of 300 beats per minute. However, the a waves on the tricuspid echocardiogram coincided closely with the P waves on a surface ECG (lead V) that disclosed a chaotic atrial tachyarrhythmia. These results suggest that echocardiographic study, in conjunction with an esophageal ECG, may be a useful, noninvasive technique for the diagnosis of dissimilar atrial rhythms.