Esophageal Electrocardiography Research Articles

Multichannel Esophageal Heart Rate Monitoring of Preterm Infants.

Autonomic dysregulation in preterm infants requires continuous monitoring of vital signs such as heart rate over days to months. Unfortunately, common surface electrodes are prone to electrocardiography (ECG) signal artifacts and cause serious skin irritations during long-term use. In contrast, esophageal ECG is known to be very sensitive due to the proximity of electrodes and heart and insensitive to external influences. This study addresses if multichannel esophageal ECG qualifies for heart rate monitoring in preterm infants. We recorded esophageal leads with a multi-electrode gastric feeding tube in a clinical study with 13 neonates and compared the heartbeat detection performance with standard surface leads. A computationally simple and versatile ECG wave detection algorithm was used. Multichannel esophageal ECG manifested heartbeat sensitivity and positive predictive value greater than 98.5% and significant less false negative (FN) ECG waves as compared to surface ECG due to site-typical electrode motion artifacts. False positive bradycardia as indicated with more than 13 consecutive FN ECG waves was equally expectable in esophageal and surface channels. No adverse events were reported for the multi-electrode gastric feeding tube. Heart rate monitoring of preterm infants with multiple esophageal electrodes is considered as feasible and reliable. Less signal artifacts will improve the detection of bradycardia, which is crucial for immediate interventions, and reduce alarm fatigue. Due to the possibility to integrate the multichannel ECG into a gastric feeding tube and meanwhile omit harmful skin electrodes, the presented system has great potential to facilitate future intensive care of preterm infants.

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.

Estimation of the Cardiac Field in the Esophagus Using a Multipolar Esophageal Catheter.

The rapid progress of invasive therapeutic options for cardiac arrhythmias increases the need for accurate diagnostics. The surface electrocardiogram (ECG) is still the standard of noninvasive diagnostics but lacks atrial signal resolution. By contrast, esophageal electrocardiography (EECG) yields atrial signals of high amplitude and with a high signal-to-noise ratio. Esophageal electrocardiography has become fast and safe, but the mechanical constraints of esophageal measuring catheters and the "random" motion of the catheter inside the subject's esophagus limit the spatial resolution of EECG signals. In this paper, we propose a method to estimate the electrical field projected onto the esophagus with an increased spatial resolution, using commonly available esophageal catheters. In a first step, we estimate the time-varying catheter position, and in a second step, we estimate the projected electrical field with enhanced spatial resolution. The proposed algorithm comprises several consecutive optimization steps, where each intermediate step produces not just a single point estimate, but a cost function over multiple solutions, which reduces the information loss at each processing step. We conclude with examples from a clinical trial, where the fields of cardiac arrhythmias are presented as two-dimensional contour plots.

The Syndrome of Inter-atrial Conduction Block.

The formulation of the syndrome of interatrial conduction block is an important step for improved identification of patients at high risk of developing atrial fibrillation (those with advanced, that is, third degree interatrial block, which includes retrograde instead of normal activation of the left atrium). The rationale and potential benefits of prophylactic antiarrhythmic treatment of patients with advanced interatrial block currently seems not sufficiently convincing and requires further study including prospective trials. In addition to the identified future directions for research in this syndrome, it seems important also to explore novel electrocardiogram (ECG) methods (e.g. new electrode positions and ECG leads) for improved characterisation of the atrial electrical events. Oesophageal electrocardiography and vectorcardiography are old, venerable and unjustifiably forgotten ECG techniques: their additional use of for better diagnosis of interatrial conduction block is highly commendable.

An optimized lead system for long-term esophageal electrocardiography

Long-term electrocardiography (ECG) featuring adequate atrial and ventricular signal quality is highly desirable. Routinely used surface leads are limited in atrial signal sensitivity and recording capability impeding complete ECG delineation, i.e. in the presence of supraventricular arrhythmias. Long-term esophageal ECG might overcome these limitations but requires a dedicated lead system and recorder design. To this end, we analysed multiple-lead esophageal ECGs with respect to signal quality by describing the ECG waves as a function of the insertion level, interelectrode distance, electrode shape and amplifier's input range. The results derived from clinical data show that two bipolar esophageal leads, an atrial lead with short (15 mm) interelectrode distance and a ventricular lead with long (80 mm) interelectrode distance provide non-inferior ventricular signal strength and superior atrial signal strength compared to standard surface lead II. High atrial signal slope in particular is observed with the atrial esophageal lead. The proposed esophageal lead system in combination with an increased recorder input range of ±20 mV minimizes signal loss due to excessive electrode motion typically observed in esophageal ECGs. The design proposal might help to standardize long-term esophageal ECG registrations and facilitate novel ECG classification systems based on the independent detection of ventricular and atrial electrical activity.

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.

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.

Oesophageal electrocardiography in healthy horses

In human medicine, oesophageal electrocardiography (ECG) is a well-established technique that magnifies P waves with respect to the QRS complex. To investigate the feasibility of oesophageal ECG recording in horses and its ability to produce larger P waves compared with base-apex and unipolar recordings. Bipolar and unipolar ECG were performed using oesophageal and surface electrodes. Oesophageal ECG was obtained from 6 different recording configurations at different oesophageal depths. Amplitudes of P, Q, R, S and T waves were measured from 3 different cardiac cycles for each recording configuration and depth. Oesophageal ECG was feasible in all horses. For all oesophageal recording configurations, significantly larger P waves were recorded from a depth that equalled 'height of the withers + 10 cm' (HW(+10) ) than from any other depth. P/QRS(magn), the ratio between the P wave and QRS complex magnitudes, was largest for intraoesophageal recordings with an interelectrode distance of 10 cm, at HW(+10), where it was significantly larger than base-apex and unipolar recordings. Base-apex recording resulted in significantly smaller P waves than all other recording configurations and significantly smaller P/QRS(magn) ratios than all other recording configurations except one combined oesophageal-surface recording (E/S(low)). Oesophageal ECG recording is feasible in horses and effective in magnifying P wave amplitude. The procedure is promising for diagnosis of supraventricular tachydysrhythmias and might be used in electrophysiological studies and for cardiac pacing.

Venice Arrhythmias 2011: October 9‐12, 2011—Venice, Italy

Introduction: Diagnosing arrhythmias by conventional Holter-ECG can be cumbersome because of artifacts, skin irritation and poor P-waves. In contrast, esophageal electrocardiography (eECG) is promising due to the anatomic relationship of the esophagus to the atria and its favorable bioelectric properties. Methods used: In an ambulant setting, we recorded eECGs from 10 volunteers with a novel, highly-miniaturized eECG recorder that is worn discretely behind the ear (1.5×1.8×5cm, 22grams). The device continuously records two eECG leads during 3 days with 500Hz sampling frequency and 24-bit resolution. Results: Mean ± SD recording time was 21.7±19.6 hours (max. 60 hours). Test persons were not limited in daily activities (e.g. eating, speaking) and only complained mild discomfort during probe insertion, which subsided later on. During 99.8% of time, the recorder acquired signals appropriate for further analysis. In unfiltered data, QRS complexes and P-waves were identifiable during >98% of time. P waves had higher amplitudes as compared to surface ECG (0.71 ± 0.42mV vs. 0.16 ± 0.03mV, p = 0.004). No complications occurred. Conclusion: Ambulatory eECG recording is safe, well tolerated and promising due to excellent P-wave detection, overcoming some limitations of conventional Holter ECG.

Comparison of the Amplitude of the P-Wave from Intracardiac Electrocardiogram Obtained by Means of a Central Venous Catheter Filled With Saline Solution to That Obtained Via Esophageal Electrocardiogram

Recognition of the P wave is important for the correct characterization of atrial and ventricular arrhythmias. When the P wave is difficult to identify on standard electrocardiography (SECG), either esophageal electrocardiography (EECG) or intracardiac electrocardiography (IC-ECG), central venous catheter may be used. The feasibility of these methods has already been demonstrated, but there is no published study comparing them. This study compared the amplitude of the P wave obtained by IC-ECG with those of the P waves obtained by EECG and SECG. SECG, EECG, and IC-ECG were performed on each patient. IC-ECG and EECG made it possible to register P waves larger than registered by SECG (p <0.00001). The difference between the largest P waves obtained with IC-ECG (5.93 +/- 3.56 mm) and EECG (4.67 +/- 2.16 mm) was not statistically significant (p = 0.1953). In conclusion, IC-ECG is easy to perform and magnifies the P wave at least as effectively as EECG.

A new high-resolution esophageal electrocardiography recording technique: an experimental approach for the detection of myocardial ischemia.

Criteria for ischemic changes in the esophageal electrocardiograph (E-ECG) have not been standardized and validated. The main goal of this study was to evaluate the experimental esophageal recording of myocardial ischemia and to assess the association between ST segment alternans in the E-ECG and ischemia. Experiments were performed on 18 anesthetized sheep with occlusion of a branch of the left anterior descending artery. The bipolar signals were recorded via an esophageal lead containing three chloridized silver electrodes. Electrical signals were amplified in a self-designed, battery-supported preamplifier (gain 1000, frequency range 0.01-2000 Hz, common mode rejection 140 dB, signal noise 5-7 microV p-p), then sent to a digital oscilloscope for display and to a pulse code-modulated recorder. Surface electrocardiography (S-ECG) data were also recorded. Ischemia E-ECG revealed homogenous ST segments without any beat-to-beat alternans. Two minutes after occlusion, 14 of 15 sheep (93%) showed repetitive beat-to-beat fluctuations within the ST segment on the E-ECG. Of the 15 sheep, 7 (47%) showed ischemia in the S-ECG (P < 0.01). For calculation of the dynamic changes in the ST segment in the E-ECG, the difference in the amplitudes of the ST segment of five successive beats to the next beat, performed for 200 consecutive beats, was calculated. The central tendency of the sum of these values before versus during ischemia was 2000 mV/ms versus 5000 mV/ms (Hodges-Lehmann point estimator) (95% confidence intervals 1700/2500 versus 3350/9250 [lower limit/upper limit]). The authors have established a close temporal relationship between the magnitude of ST segment alternans recorded via E-ECG and myocardial ischemia. The study presents the use of an esophageal electrocardiograph for detection of progressive changes of myocardial ischemia and infarction. During acute myocardial ischemia and infarction in sheep, the esophageal electrocardiograph has visually apparent ST alternans of amplitude in the millivolt range, in part due to a special amplifier (0.01-2000 Hz). This is therefore one very promising technique for better evaluation of electrocardiographic changes of ischemia.

A New High-Resolution Esophageal Electrocardiography Recording Technique

Criteria for ischemic changes in the esophageal electrocardiograph (E-ECG) have not been standardized and validated. The main goal of this study was to evaluate the experimental esophageal recording of myocardial ischemia and to assess the association between ST segment alternans in the E-ECG and ischemia. Experiments were performed on 18 anesthetized sheep with occlusion of a branch of the left anterior descending artery. The bipolar signals were recorded via an esophageal lead containing three chloridized silver electrodes. Electrical signals were amplified in a self-designed, battery-supported preamplifier (gain 1000, frequency range 0.01-2000 Hz, common mode rejection 140 dB, signal noise 5-7 micro V p-p), then sent to a digital oscilloscope for display and to a pulse code-modulated recorder. Surface electrocardiography (S-ECG) data were also recorded. Ischemia E-ECG revealed homogenous ST segments without any beat-to-beat alternans. Two minutes after occlusion, 14 of 15 sheep (93%) showed repetitive beat-to-beat fluctuations within the ST segment on the E-ECG. Of the 15 sheep, 7 (47%) showed ischemia in the S-ECG (P < 0.01). For calculation of the dynamic changes in the ST segment in the E-ECG, the difference in the amplitudes of the ST segment of five successive beats to the next beat, performed for 200 consecutive beats, was calculated. The central tendency of the sum of these values before versus during ischemia was 2000 mV/ms versus 5000 mV/ms (Hodges-Lehmann point estimator) (95% confidence intervals 1700/2500 versus 3350/9250 [lower limit/upper limit]). The authors have established a close temporal relationship between the magnitude of ST segment alternans recorded via E-ECG and myocardial ischemia. Implications: The study presents the use of an esophageal electrocardiograph for detection of progressive changes of myocardial ischemia and infarction. During acute myocardial ischemia and infarction in sheep, the esophageal electrocardiograph has visually apparent ST alternans of amplitude in the millivolt range, in part due to a special amplifier (0.01-2000 Hz). This is therefore one very promising technique for better evaluation of electrocardiographic changes 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.

Can power spectral analysis of heart rate variability identify a high risk subgroup of congestive heart failure patients with excessive sympathetic activation? A pilot study before and after heart transplantation.

Autonomic dysfunction seems to be involved in the progression and prognosis of severe congestive heart failure. Parasympathetic activity can still be abnormal 4-8 weeks after haemodynamic improvement by heart transplantation. To identify patients in heart failure with a more pronounced neural derangement and to analyse the changes in sympathetic and parasympathetic activity soon after heart transplantation, spectral indices of heart rate variability were assessed in 30 patients in severe heart failure and in 13 patients after heart transplantation; a group of 15 age-matched subjects served as controls. Heart rate variability was assessed by standard electrocardiography (ECG) in patients in heart failure and by oesophageal ECG in patients after heart transplantation. Compared with controls, the mean RR interval and total power were reduced in heart failure. The 30 patients showed two different patterns of heart rate variability: in 14 no power was detected in the low frequency band (0.03-0.15 Hz) (LF) and total power was mainly concentrated in the high frequency band (0.15-0.45 Hz) (HF), whereas in the remaining 16 patients power in the LF band was increased and power in HF band was reduced compared with the controls. Patients with undetectable LF had a lower mean RR interval and total power (745(25) v 864(36) ms, p < 0.05; 118(16) v 902(202) ms2, p < 0.001), higher concentration of plasma noradrenaline (635(75) v 329(54) pg/ml, p < 0.05), and worse clinical status and prognosis (4 deaths v no deaths at 6 month follow up) than patients with a dominant LF band. In the post-transplant patients both the mean PP interval of the remnant atrium and total power resembled results in the patients with heart failure; in 7 of the 13 post-transplant patients no power was detectable in the LF band: when both HF and LF power were present the results resembled those in the 16 patients in heart failure. These data suggest that in more advanced stages of congestive heart failure, power spectral analysis of heart rate variability allows identification of a subgroup of patients with higher sympathetic activation and poorer clinical status who are at major risk of adverse events. In the short term after cardiac transplantation the spectral profile of the rhythm variability of the remnant atrium was not improved, suggesting that parasympathetic withdrawal and sympathetic hyperactivity persist, despite the restoration of ventricular function.

Early detection of myocardial ischemia in hypertensive patients using exercise esophageal electrocardiography

Effects of submaximal exercise were studied on the unipolar esophageal electrocardiogram recorded at ventricular level in 15 patients with essential hypertension who complained of chest discomfort on effort but had negative exercise stress tests using standard leads and lead CM 5. Six patients developed horizontal or downsloping depression of the ST segment in the esophageal lead. The ischemic response might result from subcritical coronary stenosis in face of the increased myocardial oxygen demand of hypertrophied myocardium.

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.

Second Degree SA Block and Escape‐Capture Bigeminy Diagnosed by Esophageal Electrocardiography

We report a case of escape‐capture bigeminy, a rare form of arrhythmia, occurring after treatment of wide‐QRS tachycardia and diagnosed by esophageal electrocardiography recording of atrial activity which was not evident on the surface electrocardiogram.

Esophageal electrocardiography in acute cardiac care: Efficacy and diagnostic value of a new technique

Esophageal electrocardiography can detect atrial electrical activity during tachyarrhythmias when P waves are not evident by surface electrocardiography. However, patient discomfort, the difficulty of accurately interpreting cardiac signals against a background of electrical noise, and the complexity of use have limited widespread application. In this study, esophageal electrocardiography was used in 48 acutely ill patients with a new “pill electrode” system, consisting of a bipolar electrode pair (3 by 20 mm) attached to 0.5 mm diameter Teflon wires contained in a standard gelatin capsule. The capsule with enclosed electrodes was voluntarily swallowed, and the recording electrodes were positioned posterior to the left atrium. A preamplifier system with a low-frequency filter and a standard three-channel electrocardiographic recorder were used. Esophageal “pill” electrocardiographic recordings were made in 48 of 50 eligible study patients (96 percent) with tachyarrhythmias and absent or equivocal atrial activity on surface electrocardiography. In these patients, a high-quality esophageal electrocardiographic recording was obtained within one to 10 minutes with minimal patient discomfort. In 25 of 48 study patients (52 percent), the original diagnosis, based on the surface electrocardiographic recording, was incorrect after review of the esophageal recording. Results of esophageal recording altered management in 19 of 48 (40 percent) patients. This new and simple technique facilitates diagnosis and management of perplexing tachyarrhythmias in acutely ill patients by physicians with minimal training in the technique.

Intraoperative esophageal electrocardiography for dysrhythmia analysis and therapy in pediatric cardiac surgical patients.

Intraoperative esophageal electrocardiography for dysrhythmia analysis and therapy in pediatric cardiac surgical patients.

The Heart: Arteries and Veins

One of the premiere large textbooks of cardiology, this book was first published in 1966 and last revised in 1982. The immense success and popularity of this book will certainly continue. The new edition has 8% more pages, 12% more authors, and 27% more chapters. There are now seven editors and 183 authors of this encyclopedic work. The most visible additions to the volume are 18 new chapters about specific techniques and procedures in cardiology, covering topics such as thrombolytic therapy, laser angioplasty, total mechanical heart, esophageal electrocardiography, signal averaged electrocardiography, the internal defibrillator, Doppler ultrasound, computed tomography, digital subtraction angiography, magnetic resonance imaging, and others. There is also a new section about clinical pharmacology, with eight new chapters covering commonly used cardiovascular drugs. The new chapters about drugs and procedures add 272 new pages to part VII, which now constitutes 25% of the volume compared with 12% in the