ECG Method Research Articles

Quantitated fetal heart rhythm at 20, 32 and 38 weeks of gestation and dependence on rest-activity patterns

Quantitative parameters of fetal heart rate (FHR) were automatically analysed at 20, 32 and 38 weeks of pregnancy. FHR was obtained both by the fetal ECG method and by wide range Doppler ultrasound with autocorrelation. At 32 and 38 weeks, FHR was studied in relation to fetal rest-activity according to the fetal behavioural state concept (coincidence 1F and 2F). Basal fetal heart rate was significantly higher at 20 weeks of gestation than at 32 and 38 weeks. The number of accelerations increased significantly from 20 weeks to 32 and 38 weeks for C2F periods. Parameters of FHR variability, i.e. ID, ABB, LTI indices and bandwidth, were higher during periods C2F compared to periods C1F. Lowest values of all four parameters were found at 20 weeks gestation. The ID index, which is a measure of short-term variability increased significantly between 32 to 38 (C2F). The absolute values of ID, ABB and LTI were lower for ultrasound recordings than for the fetal ECG.

Effect of β-blockade on the interpretation of the exercise ECG: ST level versus [formula omitted] index

The diagnostic value of exercise-induced ST segment depression is considered to be decreased in patients receiving β-blockers. One approach to improving predictive accuracy has been to use the ratio of maximal change in exercise-induced ST segment depression to the corresponding maximal change in heart rate ( Δ ST HR index). The present study compared these two ECG methods. The records of exercise tests performed on 3047 male veterans were screened to exclude patients with prior revascularization procedures or myocardial infarction, those receiving digoxin, and those with certain resting ECG abnormalities; the use of β-blocker drugs at the time of testing was also noted. All exercise tests were sign/symptom limited. Significant angiographic coronary disease was defined as ≥75% reduction in luminal diameter of at least one coronary artery. Disease severity was evaluated in an expanded study group that included patients with prior myocardial infarction. Mean maximal heart rate was 21 beats · min −1 lower for those receiving β-blockers ( p < 0.05), but there was no difference in mean metabolic equivalent (MET) level achieved. The diagnostic accuracy of an abnormal test result for determination of the presence or absence of coronary artery disease was not significantly different in the subgroup taking β-blockers versus the subgroup not taking β-blockers (N = 200), and use of the Δ ST HR index did not improve test performance. For discrimination of severe disease, test accuracy was also unaffected by β-blockers and was not improved by the Δ ST HR index (N = 454). Exercise testing is a useful predictor of the presence and/or severity of coronary artery disease in patients taking β-blockers. Withholding these medications before testing does not appear to alter interpretation of the exercise ECG.

Reentrant Junctional Tachycardias

Most of the tachycardia arising in the atrioventricular (AV) junction are reentrant in nature. The two most common variety are AV nodal reentry and AV reentry utilizing an accessory pathway of the Kent bundle type. Typically these tachycardias have narrow QRS complex and are regular but an associated right or left bundle branch block could result in a wide QRS complex. Other mechanisms for wide QRS in AV junctional tachycardia include: (a) antidromic reentry; (b) preexcited tachycardia using two accessory pathways; (c) AV nodal reentry with incidental accessory pathway participation; and (d) atriofascicular (nodoventricular)e Mahaim participation. A variety of surface ECG and intracardiac electrophysiological methods are used to delineate the precise mechanisms which is essential for successful nonpharmacological therapy in these patients.

Two dimensional polar display of cardiac blood pool SPECT.

A new method of ECG gated cardiac blood pool SPECT to illustrate the left ventricular (LV) wall motion in a single static image, two dimensional polar display (2DPD), was described. Circumferential profiles of the difference between end diastolic and end systolic short axis images of the LV were displayed in a similar way to the bull's eye plot of 201Tl myocardial SPECT. The diagnoses by 2DPDs agreed with those by cinematic displays of ECG gated blood pool SPECT in 74 out of 84 segments (85.5%) of abnormal motion, and 155 our of 168 segments (80.3%) of normal motion. It is concluded that 2DPD can evaluate regional wall motion by a single static image in a significant number of patients, and is also useful in comparing with the bull's eye image of 201Tl myocardial SPECT.

Safe placement of atrial shunt catheters using intracardiac ECG. Initial experiences with a new ECG adapter system in 33 patients

In 1960 Robinson inaugurated the method of placing atrial shunt catheters with the help of intracardiac ECG monitoring. Vulnerability to artifacts and problems with electrical safety (which have since been solved) led to its disuse. A newly developed ECG adapter proved free from artifacts and was practicable in 33 patients. 31 shunts were correctly placed without requiring time-consuming radiography. 2 extracardiac false positions were clearly identifiable by means of true negative results, which after correction showed a typical atrial ECG. The ECG method is compared with 9 other positioning methods. It seems to be superior to the conventional chest x-ray and equal to fluoroscopy. However, the method is not on a par with sophisticated measuring techniques such as intracardiac pressure monitoring or intravasal sonography.

Clinical Usefulness of Quantitative ECG Methods for Evaluating Ischemic and Infarcted Myocardium

The complete Selvester QRS scoring system is a validated quantitative method of estimating the size of single myocardial infarcts. It remains to be validated in patients with multiple infarcts and in those with confounding factors such as ventricular hypertrophy or fascicular or bundle branch blocks. Discrepancies in its correlation with other sizing methods might give insight into the amount of infarct reperfusion (versus enzymatic methods) or the amount of residual ischemic myocardium (versus mechanical methods). Several strategies have now been presented for quantitative use of the initial ST segment deviation to indicate important clinical parameters such as the precise location of the coronary occlusion, the amount of myocardium in jeopardy, and the potential for salvage by reperfusion. Comparison of the initial ST deviation with final QRS score and with non-ECG methods of estimating the per cent of LV that is scarred and/or dysfunctional might indicate the effect of therapeutic reperfusion on MI healing. These methods remain to be validated and, as yet, no comprehensive ST segment scoring system has been developed. Use of both QRS and ST methods will be facilitated by the development of new ECG recording systems and by automated application of the various criteria. It is likely that acute coronary care in 1990 will include sophisticated methods for continuous monitoring of QRS and ST and T changes. There will be continuous trending of scores indicating the amount of ischemic and infarcted myocardium. Base-line measurements can be obtained before interventions have begun in order to indicate the potential benefit of altering the natural course for the individual patient.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship between electrocardiographically and enzymatically estimated size in anterior myocardial infarction

In 179 patients with anterior myocardial infarction the electrocardiographically estimated infarct size was related to serum enzyme activity. A precordial map containing 24 precordial positions and the peak activity of heat stable dehydrogenase (LD; EC 1.1.1.27) were used. A positive correlation was found between the area at risk (initial sum of ST-elevation) and the peak LD activity (r = 0.48 - 0.55; p less than 0.001). When the final Q-and R-wave amplitude were related to peak enzyme activity a better correlation was observed (r = 0.56 - 0.68; p less than 0.001). The sum of R-waves (sigma R) and the sum of Q-waves (sigma Q) in the 24 precordial leads were related to sigma R and sigma Q in five precordial standard leads. A good correlation was found between the two ECG methods (r = 0.75 - 0.83; p less than 0.001), indicating that an increased number of precordial leads gives information regarding the extent of infarction similar to that obtained with the routinely used standard leads. It is concluded that in the individual patient, serum enzyme activity and the final Q-and R-wave changes can give different information about infarct size. If, however, these two independent methods are used in a large number of patients in intervention studies they will probably give similar information about relative influence of the intervention on the mean infarct size.

Cardiogoniometry.

Cardiogoniometry is a new method to test heart function. It consists of a simple computerized vectorcardiography with a system of leads derived for the construction of three orthogonal projections. With the aid of these three-dimensional projections the cardiogoniometer, a microprocessor system, measures and computes the maximal vectors of depolarization (QRS) and repolarization (T). It also fixes the orientation of these two spatial vectors by projection on two planes (frontal and oblique sagittal) and determines the solid angle phi between them. Every third heart beat these five parameters and the preceding beat interval are printed out. In this way, a series of measurements is obtained in which only little disturbances of the signals of cardiac de- and repolarization occur. In patients with latent coronary insufficiency an abnormal position of the T vector can be detected long before the standard ECG shows a pathological pattern. Cardiogoniometry can be performed in the consulting room or at the bedside. It is noninvasive, painless, and free of risk. The value and limits of this new method are to be tested in comparison with the ECG and invasive methods in cardiology laboratories.

Method for determining the volume of cardiac muscle necrosis in patients with myocardial infarction

A method is proposed for determining the volume of cardiac muscle necrosis in patients with transmural, subendocardial and subepicardial myocardial infarctions using the ECG method. To facilitate calculations, a table of the volume of myocardial necrosis has been compiled. The technique was tested on 160 patients.

Body surface distributions of repolarization potentials after acute myocardial infarction. II. Relationship between isopotential mapping and ST-segment potential summation methods.

Isopotential body surface distribution derived from 14 subjects with acute anterior and 14 patients with acute inferior myocardial infarction were studied to examine three possible difficulties with ST-segment summation methods as used for evaluation of infarction severity. First, recorded sums of potentials recorded from 150 electrodes placed on anterior and posterior thoracic surfaces and from five subsets of 42 electrodes located only on the left anterior precordium were compared. Lead subsets detected only one-half of total thoracic positivity in acute anterior infarction and the sums of potentials in these sets were significantly altered by small (approximately 1-1.5-inch) deviations in grid location. Second, differing isopotential distributions could yield nearly identical sums of potentials in left precordial electrode grids. Third, the effects of the wide variations in the normal ST-segment isopotential distribution were evaluated by studying 45 normal subjects and application of difference map and departure map and departure map techniques. The results illustrate the significant variation in potentials considered to be generated by the ischemic lesion caused by differences in control patterns. Thus, the recording of potential sums over limited torso areas, the attention to potential magnitudes rather than to distributions and the assumption that the normal ST segment is isoelectric represent significant problems in applying ECG methods to the quantitative evaluation of myocardial infarction.

Computerized 12-hour simultaneous ECG, pressure- and pH-probe investigation of the oesophagus. Method and reference values in healthy individuals

A computerized 12-h simultaneous ECG, pressure- and pH-probe investigation method of the oesophagus is described, and reference values in healthy individuals presented. The analysing system includes two new elements. An interface box, which detects propagating and retrograde peristalsis, by looking at pressures in the oesophagus. A computer (Hewlett Packard 9845T), which makes the whole analysis automatic, draws a 12-h pH-curve, makes area computations, pH-related swallow registrations and time-pH relationships. The results obtained with this measuring system are in agreement with the results of other similar investigations. It is concluded that area computation is the most accurate method of reflux detection. Furthermore this simultaneous ECG, pressure and pH measuring system is excellent in differentiating between chest pain of cardial and oesophageal origin.

Evaluation of Myocardial Damage in Patients Undergoing Coronary-Artery Bypass Procedures with Halothane-N2O Anesthesia and Adjuvants

During a 6-month period in 1975, 102 patients undergoing scheduled coronary-artery bypass grafting were studied by both conventional ECG and heart-specific enzymatic methods to evaluate the incidence and estimate the extent of myocardial damage associated with an anesthetic management protocol using halothane as a primary agent with adjuvant agents. Anesthetic interventions were made to maintain heart rate and systolic pressure at resting levels or below the heart rate systolic pressure product documented during exercise-induced angina. These interventions included adjustment of halothane concentration in all patients, the use of adjuvant agents in 88.2 percent, vasodilators in 26.5 percent, and the precardiopulmonary bypass use of vasoconstrictor or cardiostimulants in 9.8 percent. There were 2 early postoperative deaths. ECG evidence of infarction was observed in 4 surviving patients. Sustained release of heart-specific CPK-MB isoenzyme occurred in 78 percent of surviving patients. Isoenzyme activity was detected in only 1 patients prior to cardiopulmonary bypass (CPB), in 1 patient during CPB, and in all others after termination of CPB. The extent of myocardial damage as estimated by integrating CPK-MB values over time was directly related to number of vessels grafted and to aortic cross-clamp and CPB times. The ECG and enzymatic data both document a low level of myocardial damage associated with this anesthetic management protocol.

Diagnostic possibilities of the uncorrected orthogonal ECG Trethewie system in ventricular overload.

The possibilities of the uncorrected orthogonal ECG system (Trethewie) in assessment of the ventricular overload have been studied. The uncorrected orthogonal ECG system detects the left ventricular overload better than conventional ECG system. The simultaneous application of both uncorrected orthogonal ECG and conventional ECG increases the diagnostic possibilities of the ECG method.

Corrected orthogonal ECG leads in patients with chronic coronary insufficiency

Corrected orthogonal ECG leads open up the prospect of increasing diagnostic capabilities and at the same time simplifying the ECG method of examination. We have shown the advantages of the modified Frankov system of corrected orthogonal leads in the study of patients with overload and hypertrophy of the ventricles of the heart, mitral stenosis, myocardial infarction. The present work aims to study ECG changes in the same system in patients with coronary insufficiency without any indication of a previous myocardial infarction.

電位心電図法並に其の臨床的意義

電位心電図法並に其の臨床的意義