ECG Wave Research Articles

Why did QT dispersion die?

Considerable controversy exists about the meaning of QT dispersion (QTD). The working hypothesis of the present paper was that the necessary although not sufficient condition for the validity of QTD concept is the association of QTD with nondipolar voltage (NDPV) in T waves of the 12-lead ECG. ECGs of 4,890 subjects, 966 with coronary heart disease (CHD) and 3,844 considered CHD-free were processed using computer programs for measurement of the ratio of the first two eigenvalues (E2/E1), nondipolar voltage (NDPV), terminal T wave direction and ECG estimate of left ventricular mass (LVM). The mean NDPV in T wave was 11 muV (SD 3.9), with 6 muV (SD 1.3) in terminal 40 ms. NDPV alone explained only 6% and NDPV, E2/E1 and LVM combined 13% of QTD variance. There was a modest increase in the fraction of subjects with QTD >60 ms among subjects with NDPV in terminal T > 7 muV compared to those with NDPV >/=7 muV (15% vs. 10%). A more profound increase was associated with terminal T wave direction deviating from normal (37% vs. 12% among those with normal direction), reflecting dipolar rather than nondipolar components. The association between QTD and NDPV is weak, and QTD is unlikely to represent any meaningful myocardial repolarization event in the interval domain. It seems more logical to use direct measurement of NDPV as a potential marker of localized dispersion and heterogeneity of ventricular repolarization for evaluation of the risk of adverse cardiac events.

A comparative study of three techniques for QRS cancellation in the ECG (poster session)

In this paper, the performance-three QRS cancellation techniques compared to obtain a residual ECG information containing only atrial activity (AA), thereby facilitating detection of the P wave in the ECG and/or analysis of atrial arrhythmias. The methods are based on adaptive filters (AdF), neural networks (NN), and the space-time of an averaged beat for subsequent removal from the ECG signal, the comparison is made with reference to the results obtained with the adaptive filtering method by Thakor. The results show that the methods based on NN and AdF are more robust to morphological changes of the signal and in the presence of noise than non-adaptive methods, also have the advantage that they do not require a pre-detection stage of QRST, however, for the average beat alignment method, best results are obtained when there are no QRS detection failures.

Hospital and emergency ambulance link: using IT to enhance emergency pre-hospital care

Emergency ambulances traditionally inform receiving hospitals of impending arrival of patients only in instances of load and go situations, which on average constitute less than 5% of ambulance runs. Information transmitted is usually sparse. For all other runs, information is made available only on arrival at the emergency department (ED). There have also been numerous limitations associated with voice transmissions. A comprehensive electronic ambulance case record was created as a pilot project in Singapore between three emergency ambulances and the busiest ED there. All information captured by the ambulance crew, including vital signs information and ECGs was entered or downloaded onto a ruggardised PC in the ambulance and this complete ambulance record was transmitted to the ED. Transmission was wireless via the public mobile data network. A 3-month analysis of this pilot run revealed the following. (1) It was possible to capture a complete ambulance case record electronically at a mean time of 94 s vs 7 min 7 s for the traditional written record. (2) Air transmission time for data was ≈4 s unless ECG wave forms were also transmitted resulting in transmission times frequently exceeding 60 s. (3) At least 68% of data was transmissible in 75% of Hospital & Emergency Ambulance Link (HEAL) ambulances as opposed to only 25% in less than 5% of non-HEAL ambulances. (4) Paramedics’ time in the ED decreased from 15 to 8 min as a result of HEAL. (5) The waiting time for critical care patients to be seen at the ED decreased from 35 to 17 min if brought by HEAL ambulances. (6) The HEAL system was able to effectively prompt paramedics in carrying out critical aspects of treatment in close to 100% of instances. (7) The pilot HEAL system was able to demonstrate a limited amount of automated audit of specific aspects of ambulance runs. Having demonstrated the feasibility of the HEAL system, it is a matter of time before enhanced features such as electronic data collection at patient site, voice activated data entry, transmission of data from site, automated ambulance audits and an enhanced level of professional care in the ambulances become common-place reality.

Prominent Q Waves in a Preoperative ECG

Prominent Q Waves in a Preoperative ECG

SPET miocárdico de perfusión y ventriculografía isotópica en la miocardiopatía hipertrófica obstructiva y no obstructiva

To evaluate the role of myocardial perfusion SPET and radionuclide ventriculography in patients with hypertrophic cardiomyopathy (HC). Exercise myocardial perfusion SPET with 99mTc-tetrofosmin and radionuclide ventriculography were performed in a consecutive series of 101 patients (54 15 years, 50 women, 55 with dynamic obstruction) diagnosed of HC by echo. Follow-up from the diagnosis was 9,9 6,7 years (1 to 28 years). Thirty six percent of patients had perfusion defects (non reversible in 15 and reversible in 21). In non obstructive HC higher number of patients with non reversible defects (p = 0.01 was obseved and in patients with no reversible defects higher incidence of pathologic Q waves in ECG (p = 0.01), Higher ventricular volumes (p < 0.05), lower ejection fraction (p = 0,0001) and longer time to peak emptying velocity (p < 0.05). There were 4 cardiac deaths, 15 syncopes, 18 pacemakers and 6 myectomy. Ejection fraction was higher in patients with syncope (p = 0,034) and there was no isotopic variable predictive of mortality, pacemaker or myectomy. Neither SPET nor radionuclide ventriculography have a prognostic role in patients with HC, but patients with syncope have higher values of ejection fraction. Patients with non reversible defects have higher rate of pathologic Q waves in ECG, higher ventricular volumes and lower ejection fraction. This is indicative of evolution to dilated form of HC.

Radiofrequency Catheter Ablation of Atrial Tachycardia

Radiofrequency catheter ablation (RFCA) has been established as an effective and safe treatment modality for atrioventricular nodal reentrant tachycardia and WPW syndrome. Surgical ablation or direct current catheter ablation had been performed to cure focal atrial tachycardia (AT), however, these treatments had limitations such as the need of open thoracotomy or the risk of barotrauma. RFCA could be an effective treatment modality for cure of AT. We performed RFCA for AT in 22 patients (male 13, mean age 38.1±15.4 years) among 831 patients who underwent electrophysiologic study between Jul. 1996 and May. 1999. Clinical pattern of tachycardia was paroxysmal (17 patients) or incessant (mean duration of symptoms, 41.1±42.3 months). Associated cardiac diseases were tachycardia-mediated cardiomyopathy (3 patients), aortic stenosis (1 patient) and ventricular septal defect with pulmonic stenosis (1 patient). AT was induced by programmed electrical stimulation in 17 patients;AT in the other 5 patients was incessant. The RFCA was successful in 17 patients (77.3%). The mean interval between atrial electrogram of mapping catheter and P wave of surface ECG was –53.5±24.9msec in 17 successful sites. Fractionated atrial activities were invariably found in the successful sites. Successful sites of RFCA for right AT were around coronary sinus ostium (5), crista terminalis (4), lower portion of sinus node (1), inferior portion of tricuspid annulus (1), and His area (1), respectively. In left AT, lateral portion near atrioventricular groove (2), inferoposterior portion (2) and near left atrial appendage (1) were successful site. During follow-up (mean 23 months), one patient had recurrence (recurrence rate 5.9%). RFCA for AT is an effective and curative treatment in selected cases. (Korean Circulation J 2000;30(2):153-165)

An electrocardiographic criterion for diagnosis of patent foramen ovale associated with ischemic stroke.

An M-shaped bifid notch on the ascending branch, or on the zenith, of the R wave in inferior ECG leads (II, III, aVF), so called "crochetage," is an indicator of ostium secundum atrial septal defects. The pathophysiology underlying this finding remains unknown. A crochetage pattern has not been previously reported in patients with patent foramen ovale (PFO); however, the location of this defect and the secundum atrial septum are similar. The purpose of this study was to determine the prevalence of crochetage in cryptogenic stroke patients with or without PFO. A conservative selection scheme was used to identify patients likely to have had PFO-associated strokes (ie, cryptogenic) and to exclude any structural, functional, or vascular heart disease responsible for ECG changes. All patients had a standard 12-lead ECG. The prevalence of crochetage in each group was determined. Sixty consecutive patients were studied (28 with echo-documented PFO and 32 echo-negative control subjects). The crochetage pattern was present in at least 1 inferior limb lead in 10 of 28 PFO patients (36%) and 3 of 32 control subjects (9%) (P<0.05). The sensitivity and specificity of the crochetage pattern for diagnosis of PFO in cryptogenic stroke cases were 36% and 91%, respectively; positive predictive value was 77%. The finding of an ECG crochetage pattern may help to identify stroke patients with PFO, may help to streamline their diagnostic workup, and may warrant future studies to determine its value in stratifying stroke risk in patients with PFO.

MECHANISM AFFECTING RELATIONSHIP BETWEEN PULSE WAVE TRANSIT TIME AND BLOOD PRESSURE IN ISOFLURANE ANESTHETIZED DOGS

S222 Although the transit time between aortic valve opening and peripheral arterial pulse arrival, pulse wave transit time (PWTT), correlates well with blood pressure change (BP), it is shown that the transit time between R wave of ECG and peripheral pulse arrival (modified PWTT: m-PWTT) has a poor correlation. The present study was done to elucidate the mechanism producing such poor correlation in isoflurane anesthetized dogs. METHODS: With the approval of institutional Animal Investigation Committee, 10 mongrel dogs were anesthetized and mechanically ventilated. A catheter tip pressure transducer was placed distal to the aortic valve to measure pre-ejection period (PEP) as well as at the bifurcation of femoral artery for m-PWTT. A PA catheter was used for cardiac output measurement. PEP and m-PWTT were measured while hypotension was induced by isoflurane inhalation or hypovolemia, and hypertension induced by dobutamine or phenylephrine infusion, in random manner. A linear correlation between m-PWTT and BP was obtained by using least squares method. RESULTS: During hypotension and hypertension, m-PWTT and PEP were well correlated with BP (Table 1). During hypertension by phenylephrine infusion, the slope of m-PWTT against BP was positive, with the reflex prolongation of PEP. (Table 1).Table 1: Correlation Coefficient and Slope of m-PWTT against Blood PressureCONCLUSION: The good correlation between m-PWTT and BP indicates that m-PWTT is a good predictive parameter for blood pressure change when the cardiac performance alters due to anesthetics, or inotropic agents. On the contrary, it has a negative predictive value for blood pressure estimation, when vasoactive agents are given, probably due to the reflex response of PEP.

Clinical, electrophysiological characteristics, and radiofrequency catheter ablation of atrial tachycardia near the apex of Koch's triangle.

Atrial tachycardia, with its focus near the apex of Koch's triangle, may carry a potential risk of atrioventricular block during radiofrequency catheter ablation. The efficacy and safety of this procedure have never been addressed. The characteristics and catheter ablation results are reported for six patients with atrial tachycardia near the apex of Koch's triangle. All six patients were female aged 49.6 +/- 9.3 years (range 39-63). Organic heart disease was present in 3 (50%) of the 6 patients. The P wave in surface ECG had a mean axis of -28 degrees (range -90 degrees - +30 degrees) in the frontal plane. The catheter ablation was guided by activation sequence mapping. The energy was titrated from low power level. Atrial overdrive pacing was used to monitor the atrioventricular conduction should accelerated junctional rhythm occur. At the final successful ablation site, the local atrial activation was 41.8 +/- 9.1 ms before the P wave and His-bundle potential was present in 5 of the 6 patients. All patients had their atrial tachycardia eliminated without recurrence or heart block during a follow-up period of 17.7 +/- 8.5 months (range 6-30). In conclusion, atrial tachycardia near the apex of Koch's triangle has distinct clinical and electrophysiological features. Radiofrequency catheter ablation can be performed effectively. However, extreme care must be taken to prevent inadvertent atrioventricular block. Titrated energy application and continuous monitoring of atrioventricular conduction are mandatory.

Relationship between normalization of negative T waves on exercise ECG and residual myocardial viability in patients with previous myocardial infarction and no post-infarction angina.

The usefulness of normalization of negative T waves in exercise ECG was investigated as an index of myocardial viability in patients with previous myocardial infarction with no symptoms or ischemic ST-segment change during exercise test. A total of 39 patients, 20 with T-wave normalization (POS group) and 19 without T-wave normalization (NEG group) on exercise ECG. were studied. Myocardial viability was evaluated by thallium-201 single-photon emission computed tomography (SPECT) during exercise or at rest. We also assessed left ventricular ejection fraction (LVEF) by contrast ventriculography before (n=39) and after percutaneous transluminal coronary angioplasty (PTCA) (n=17). SPECT detected myocardial viability in 16 (80%) of the 20 patients in the POS group and in 4 (21%) of the 19 patients in the NEG group (p<0.01). LVEF increased after successful PTCA in the POS group (from 53+/-13% to 63+/-8%, p<0.025), but fell in the NEG group (from 57+/-10% to 51+/-8%). It is concluded that normalization of negative T waves on exercise ECG is a useful, simple index of myocardial viability in patients with previous myocardial infarction with no symptoms or ischemic ST-segment change during exercise testing.

Hemodynamic characterisation by ECG and arterial pulse wave velocity

Hemodynamic characterisation by ECG and arterial pulse wave velocity

Hemodynamic characterisation by ECG and arterial pulse wave velocity

Hemodynamic characterisation by ECG and arterial pulse wave velocity

Quantitative analysis of errors due to power-line interference and base-line drift in detection of onsets and offsets in ECG using wavelets.

Timing characterisation of the ECG using wavelet transforms is a new technique in which multiscale analysis reduces the influence of noise. This technique issued to investigate the effect of noise and to estimate the errors involved in the detection of onsets and offsets of ECG waves. With appropriate choice of scales of analysis, the study shows that the errors involved in the measurement of QRS width in the presence of base-line wander are negligible. The 50 Hz power-line interference introduces a maximum error of 6.25% if it is greater than 50% of the signal amplitude. The P and T complexes are not affected by power-line interference, but the base-line wander introduces a maximum error of 9.6%. In situations with the simultaneous presence of both types of noise, the use of an optimised scale restricts the errors to within clinically acceptable limits.

DSP implementation of wavelet transform for real time ECG wave forms detection and heart rate analysis

An algorithm based on wavelet transform (WTs) suitable for real time implementation has been developed in order to detect ECG characteristics. In particular, QRS complexes, P and T waves may be distinguished from noise, baseline drift or artefacts. This algorithm is implemented in a DSP (SPROC-1400) with a 50 MHz frequency clock. The performance of this algorithm is discussed, its accuracy is evaluated and a comparison is made with a similar algorithm implemented in C language. For the standard MIT/BIH arrhythmia database, this algorithm correctly detects 99.7% of the QRS complexes.

Glibenclamide attenuates peaked T wave in early phase of myocardial ischemia.

ECG peaked T wave appears during the early phase of myocardial ischemia, but the underlying mechanisms remain unknown. The purpose of this study was to elucidate the role of ATP-sensitive K+ channel (KATP) in this ECG change. In 12 anesthetized, open-chest dogs, the sinus node was crushed and the right atrium was paced at a cycle length of 400 ms. The left anterior descending coronary artery was abruptly occluded for 60 s before (control) and 15 min after an intravenous infusion of vehicle (n = 6) or glibenclamide (1 mg/kg, n = 6), a blocker of KATP. Forty-eight epicardial electrograms were simultaneously recorded from the anterior surface of the left ventricle. The potentials at 40, 80 and 120 ms from the J point were measured, and these points corresponded to the early, middle and late phases of the T wave, respectively. During the control occlusion, T wave increased time-dependently and the maximal T-wave change was noted at the end of 60 s of coronary occlusion. The extents of T-wave elevation at the early, mid and late T phases were 5.5 +/- 0.5, 7.3 +/- 0.8 and 11.7 +/- 1.8 mV, respectively, and these T-wave elevations were significantly reduced by 33 +/- 21%, 59 +/- 12% and 63 +/- 13%, respectively, after the pretreatment with glibenclamide but not with its vehicle. The % reductions of mid and late T by glibenclamide were significantly larger than that of early T wave (P < 0.05). An abrupt coronary occlusion accompanied peaked T wave as an early ECG wave change. As the extent of this T-wave elevation was attenuated by glibenclamide, the ischemia-induced alteration of ventricular repolarization can partly (60%) be explained by the modification of KATP activation.

Cellular Basis for the Electrocardiographic J Wave

The J wave is a deflection that appears in the ECG as a late delta wave following the QRS or as a small secondary R wave (R'). Also referred to as an Osborn wave, the J wave has been observed in the ECG of animals and humans for more than four decades, yet the mechanism underlying its manifestation is poorly understood. The present study investigates the cellular basis for the J wave using an isolated arterially perfused preparation consisting of a wedge of canine right or left ventricle. A 12-lead ECG was initially recorded in vivo. After isolation and arterial perfusion of the right or left ventricular wedge, transmembrane action potentials were simultaneously recorded from epicardial, M region, and endocardial transmural sites with three floating microelectrodes. A transmural ECG was recorded concurrently. A J wave was observed at the R-ST junction of the ECG in 17 of 20 adult dogs, usually in leads II, III, aVR, and aVF and the mid to lateral precordial leads. The J wave in the transmural ECG recorded across the wedge was closely associated with the presence of a prominent action potential notch in epicardium but not endocardium. The shape and amplitude of the J wave were found to depend on (1) the transmural distribution of the action potential notch amplitude, (2) the relative time course of the early phases of the action potential (width of notch) at different sites within the wall, (3) sequence of activation, and (4) conduction time across the wall. A highly significant correlation was demonstrated between the amplitude of the epicardial action potential notch and the amplitude of the J wave recorded during interventions that alter the appearance of the electrocardiographic J wave, including hypothermia, premature stimulation, and block of the transient outward current by 4-aminopyridine. Ventricular activation from endocardium to epicardium, with epicardium activated last, was also an important prerequisite for the appearance of the J wave. This sequence permits the establishment of a voltage gradient of the early phases of the action potential after activation (ie, the QRS) is complete. Our results provide the first direct evidence in support of the hypothesis that heterogeneous distribution of a transient outward current-mediated spike-and-dome morphology of the action potential across the ventricular wall underlies the manifestation of the electrocardiographic J wave. The presence of a prominent action potential notch in epicardium but not endocardium is shown to provide a voltage gradient that manifests as a J (Osborn) wave or elevated J-point in the ECG.

Automatic detection of supraventricular premature contraction and P wave in holter ECG

Automatic detection of supraventricular premature contraction and P wave in holter ECG

Intra-QRS high-frequency ECG changes with ischemia: Is it possible to evaluate these changes using the signal-averaged holter ECG in dogs?

The purpose of this experiment is to study the possibility of intra-QRS high-frequency electrocardiographic (HFECG) changes for the evaluation of and recovery from myocardial ischemia in both the time-domain and spectral-turbulence analyses on the signal-averaged ECG using the Holter ECG monitoring (Holter SAECG) system. A balloon catheter was inserted into the left anterior descending coronary artery (LAD of 8 mongrel dogs and was maintained inflated for 2 hours to occlude the LAD and then was deflated to allow for reperfusion. The cardiac signal from the three orthogonal leads of the surface ECG (X, Y, and Z) was recorded and analyzed with a Del Mar Avionics (model 459, Irvine, CA) recorder and analyzer (model 563). The Holter SAECG was assessed before the LAD occlusion phase (control), during the coronary occlusion phase (ischemia), after the reperfusion phase (recovery). To evaluate intra-QRS ECG changes in the time-domain analysis, root-mean-square (RMS) voltage of the entire QRS in 40–250 Hz (40 RMS), 100–250 Hz (100 RMS), and 150–250 Hz (150 RMS) were studied and the vector magnitude of the QRS was depicted. In the spectral-turbulence analysis and spectrocardiogram to study the discordance of the ECG wave front velocity by fast Fourier transformation analysis, the interslice correlation mean (IC mean) and interslice correlation standard deviation (IC SD), which were calculated as the mean and standard deviation of the Pearson correlation coefficient of each time slice with its neighbor, were investigated. In the time-domain analysis, the LAD occlusion by balloon catheter at ischemia produced a reduction in 40 RMS, 100 RMS, and 150 RMS, while a restoration was seen at recovery in 40 RMS and 100 RMS. In the spectral-turbulence analysis, LAD occlusion at ischemia caused a decrease in IC mean and an increase in IC SD. The wave-form of the vector magnitude and the spectrocardiogram seen at control showed changes with ischemia and was restored at recovery with the coronary reperfusion. It was thought possible to capture the intra-QRS HFECG changes that occur during myocardial ischemia and recovery from it in the time-domain analysis and spectral-turbulence analysis on the Holter SAECG system in spite of the limitation of this methodology. To evaluate myocardial ischemia and recovery, this method should be useful clinically.

Electrocardiographic inverse solution for ectopic origin of excitation in two-dimensional propagation model

Inverse calculations were examined that sought the origin of a cardiac ectopic excitation sequence. Cardiac anatomy and its geometric relationships to sites on the body surface were adapted from human cross-sectional images to form a two-dimensional model, which included ventricular muscle and a primitive conduction system. The surrounding volume conductor was modelled in a simplified way as unbounded, homogeneous and isotropic. In a series of tests, one ectopic origin was designated the 'true' origin. The ECG for this true origin was compared to ECGs for 197 ectopic 'trial' origins, and differences between the wave forms for true versus trial origins were determined. Core issues were the magnitudes of changes in ECG wave forms as a function of the site of origin, whether these changes were sufficient to imply uniqueness, and what spatial resolution might be expected, in the presence of realistic noise levels. For a noise level of 10 microV RMS, the origin of excitation was localised to a single region of the muscle using one wave form from the body surface, with a resolution of 10 mm. The resolution was not improved significantly with a second electrode on the body surface, but was substantially improved with an endocardial electrode.

体外循環離脱 酸素供給からみた離脱の条件

This review explains the physiological bases of oxygen transport and evaluation of the heart muscle contractility when we stop the assist circulation of the cardio-pulmonary bypass. When the cardiac index becomes more than two l/min/m2 and the pressure of the left atrium becomes less than 18mmHg, we usually stop the assist circulation. And we also know Forrester's indication of the heart failure. However, there are controversies about the timing of the weaning from the assist circulation. We refereed the relationship of cardiac output and oxygen consumption which were obtained both at the resting condition and during mild to severe exercise. Then we interpolated the value of the minimum cardiac output to survive from the results. The value indicates 1.0l/min/m2 in the cardiac index. The another limitation may be the maximum pressure of the left atrium to be proof against the lung damage. Forrester noted when the value becomes more than 18mmHg, the congestive lung will occur. But the actual lung can tolerate higher pressures, Judging from our analyois of pulmonary lymphatic drainage, 25mmHg of LAP within 30 minutes will never induce acute pulmonary edema.In this article, I also introduce the QD and DS time during the cardiac surgery as the indices of the cardiac contractility. QD time is the duration time from R wave of ECG to the arterial end diastolic pressure. DS time is the duration time from the end diastolic pressure to the systolic pressure. When the duration of the DS time decrease less than 200 msec, the patients weaned from the cardio-pulmonary assist circulation. The evaluation of these indicator is not certain now, but the electrical circuit can measure these values easily and we can measure them continuously during and after the cardio-pulmonary bypass.