A new method for automated detection of the R-on-T phenomenon

The detection of premature ectopic beats coinciding with the T-wave of the antecedent beat is important for patient monitoring. In the method described here, the difficulties of direct measurement of QT time are avoided by evaluating the changes of QT time according to heart rate by use of a diode function generator. An analog circuit is used for comparing the computed QT time with the coupling interval of successive beats. In case of a R-on-T-phenomenon an alarm is given. The frequency of alarms is registered on a trend recorder. The method is based on empirical equations which all contain a constant factor. Our investigations showed that the variability of this factor during longer periods of monitoring was small enough to allow sufficient exactness of the evaluation procedure.     

Automatic identification of late potentials

The purpose of the present study was to develop an algorithm for the automated identification of ventricular late potentials (LP) that can be recorded non-invasively by means of the signal averaging technique. This new algorithm was designed to determine the possible presence and the onset and duration of a given LP by analyzing the end of the QRS complex. As there is no objective standard for identifying these late potentials, the new algorithm was developed by continuous comparison and adaptation to visual analysis in 65 patients (algorithm definition phase). In the subsequent trial phase, visual and automated analysis were compared in a second cohort of 50 patients (40 patients with and 10 patients without late potentials). In the latter 50 patients, the results obtained with the new algorithm corresponded to the analysis made by at least two of three independent observers in 92% of cases. In only four patients--one without and three with late potentials--there was no agreement between the observers and the new program. In conclusion, the new algorithm can be used reliably for the evaluation of late potentials. The results are more objective. They are reproducible, which is of great advantage when data from different groups are to be compared or when less experienced investigators are using non-invasive methods for registration of late potentials.     

The conduction system in rheumatoid arthritis with complete atrioventricular block.

Rheumatoid arthritis, of the peripheral type, or the ankylosing spondylitis type, with complete atrioventricular (A-V) block^1–11 or other conduction disturbances^12–18 has been sporadically reported. Very few conduction system studies have been done in these cases.^{3, 7–9, 17, 18} The present report deals with a comprehensive serial section study of the conduction system in a case of the peripheral type of rheumatoid arthritis with complete A-V block.     

Paroxysmal tachycardia with atrioventricular dissociation in a patient with a variant of pre-excitation syndrome

We report a patient with a variant of the pre-excitation syndrome who has paroxysmal tachycardia with a pattern of left bundle branch block and ventriculo-atrial dissociation. The tachycardia is precipitated by exercise, reproduced by atrial pacing and terminated with lidocaine. Between attacks the electrocardiogram revealed prominent R waves in right precordial leads and the vectorcardiogram displayed anterior displacement of the mean QRS vector, but neither was diagnostic of pre-excitation. The resting P-R interval (140 msec) and A-H interval (60 msec) were within normal limits, but the H-V interval (30 msec) was at or slightly below normal limits. Increasing heart rate from 80 to 150/min with atrial pacing increased A-H from 70 to 160 msec, but did not change the H-V interval. With pacing at 160/min, A-H lengthened progressively from 160 to 190 msec, but A-V remained constant at the critical limit of 190 msec. Accordingly, the H-V interval decreased until the His spike disappeared into the QRS or did not occur because of A-V block. At this point, the QRS complex changed to that seen during spontaneous tachycardia. Pacing was stopped, but tachycardia continued at 160/min and ventriculoatrial dissociation appeared. Lidocaine promptly restored sinus rhythm. We speculate that the patient has anomalous conduction between the lower segment of the A-V node and the ventricular septum (Mahaim fibers) and a reciprocating tachycardia which results from antegrade conduction down the anomalous pathway and retrograde conduction up the His-Purkinje system and lower A-V node. Ventriculo-atrial Wenckebach during the tachycardia excludes participation of atria and upper part of the A-V node in the re-entrant tachycardia. This variant of pre-excitation syndrome could easily be mistaken for “true ventricular tachycardia” and serious heart disease.     

His bundle electrogram in trifascicular disease: report of a case studied with His bundle electrograms.

His bundle electrograms were performed on a 75 year old female with trifascicular block and digitalis induced junctional block. The usefulness of this technique in understanding the patients' electrocardiographic abnormalities and the relationship to phase-3 and phse-4 block is discussed.     

Mobitz II atrioventricular block due to infra-Hisian block and bundle branch extrasystoles.

An asymptomatic elderly male presented with complete right bundle branch block, left anterior fascicular block and Mobitz Type II second degree atrioventricular block. In addition, he was noted to have ventricular premature systoles. Electrophysiologic studies demonstrated two apparently different mechanisms for the second degree A-V block--infra-Hisian block and A-V block due to bundle branch extrasystoles arising in the affected right bundle branch. Concealed conduction of the bundle branch extrasystoles as the proximate cause of infra-Hisian block could not be excluded. However, both forms of A-V block were evidently dependent upon significant distal conduction system disease; this consideration was felt to warrant permanent pacemaker implantation.     

Disappearance of right bundle branch block with left anterior hemiblock when associated with a type B pre-excitation syndrome

A patient with mitral valve disease showing RBBB plus LAH with an intermittent association of type B pre-excitation is presented.The bifascicular block is masked by the existence of pre-excitation. The RBBB image is entirely canceled and the LAH is altered because its inital forces are replaced by a delta wave. The electrical axis in the frontal plane is also modified.The mechanism of production of this ventricular complex is explained on the basis of the premature excitation of the right ventricle and the sum of forces produced by the activation through the posteroinferior division of the left bundle.     

Right bundle branch block in complete transposition

Two of 26 infants with complete transposition presented with complete right bundle branch block in the first year of life, and 10 showed incomplete right bundle branch block. In no instance was the right ventricular conduction anomaly related to surgery or cardiac catheterization and it was not present at birth. The two cases with complete right bundle branch block had prolonged and severe hypoxemia and markedly dilated right ventricles. One had depressed right ventricular function and died after a Mustard procedure from low output syndrome. Whereas incomplete right bundle branch block may reflect right ventricular hypertrophy, it is suggested that complete right bundle branch block in complete transposition may signify right ventricular dysfunction and possibly irreversible changes of the right ventricular myocardium. It may be a sequel of long-term hypoxemia and pressure overload. Once observed, it is perhaps an indication for an alternative surgical approach other than an intra-atrial repair procedure.     

Effects of coronary arteriography on atrioventricular conduction. Studies with His bundle electrography.

The effect of coronary arteriography on atrioventricular (A-V) conduction was studied in 26 patients with the use of His bundle electrography. Slowing of atrioventricular conduction (prolonged A-H interval) was observed in all 26 pateints following either left or right coronary arteriography without a detectable change in the H-V interval. In four patients with left coronary preponderance in arterial distribution pattern, prolonged A-H inverval was produced only by injecting the contrast material into the left coronary artery. Conversely, in the remaining 22 patiens either with right preponderance or balanced distribution, prolongation of the A-H time was a result of opacification of the right coronary artery. The A-H interval at peak prolongation (133.9 +/- 18.7 [S.D.] msec.) was significantly higher than the control measurement (98.3 +/- 15.7 msec.) (P less than 0.0001). Prolongation of the A-H interval started around 4 seconds after the initiation of injection, reached its peak at an average of 7.7 seconds, and subsided within 20 seconds. When intracoronary injection of 6 ml. of normal saline was made in these 26 patients, no change was observed in the His bundle electrograms. On the other hand, hypertonic (20 per cent) glucose solution, when injected into coronary arteries, had an effect remearably similar to that of contrast material on A-V conduction. These findings suggest that prolonged A-H interval observed during coronary arteriography may be a result of osmotic effect of the contrast material, rather than hypoxia resulting from dilution of coronary blood flow.     

Effect of propafenone in the Wolff-Parkinson-White syndrome: electrophysiologic findings and long-term follow-up

The electrophysiologic and long-term efficacy of propafenone, a relatively new antiarrhythmic agent, was assessed in 47 patients with accessory pathways. In 23 patients (group I), the electrophysiologic effects were assessed initially. In 19 patients in this group and in 24 additional patients (group II), long-term therapy with oral propafenone was initiated. The mean age of the patients was 38 years in group I and 41 years in group II. The duration of a history of tachycardia in both groups was 12 years (mean); 14 patients previously had had attacks of syncope. During the electrophysiologic study in group I, propafenone did not change the spontaneous sinus rate. Corrected sinus node recovery time as well as the AH interval, HV time, QRS duration and effective refractory periods of the atria and ventricles was significantly prolonged. The effective refractory period of the accessory pathway increased from 238 to 322 ms (p less than 0.02). The 1:1 conduction capacity of the accessory pathway decreased from 231 to 176 beats/min (mean; p less than 0.01). Complete block in the anterograde direction occurred in 6 patients. The shortest RR interval during atrial fibrillation increased from 232 to 303 ms (p less than 0.05). The retrograde refractory period of the accessory pathway was prolonged from 245 to 295 ms (p less than 0.01). Complete or 2:1 retrograde block during basic drive occurred in 3 patients and 1 patient, respectively. In 6 of 15 patients, propafenone made sustained supraventricular tachycardia (SVT) either no longer inducible or nonsustained. The cycle length of induced SVT increased from 324 to 395 ms (p less than 0.01). During long-term administration (follow-up duration 2 to 3 years), 17 of 43 patients did not report any episode of symptomatic tachycardia. In another 18 patients, tachycardia was rare, slower and self-terminating. In only 3 patients, the frequency and severity of attacks had not changed. One patient with dilated cardiomyopathy died suddenly. Side effects necessitating discontinuation of medication were observed in only 2 patients. The remaining side effects, if present, were tolerated, and dosage dependent. In conclusion, propafenone is an effective and well-tolerated antiarrhythmic agent in the long-term management of patients with the Wolff-Parkinson-White syndrome.     

Complications with retained transvenous pacemaker electrodes.

Out of a series of 1,734 pacemaker patients, the clinical course of 46 patients was reviewed in whom a functionless endocardial electrode was retained. Non-infected electrodes (25 patients) were generally well tolerated without complications, except in one patient who experienced fatal catheter embolism into the pulmonary artery. In cases of infected electrodes (21 patients) a mortality rate of 25% was encountered due to septic complications. Catheter migration was fatal in two out of three patients. It is concluded that entrapped electrode catheters should be removed by thoracotomy if persisting infection is present or if catheter migration has occurred.     

Atrial flutter, supraventricular tachycardia, junctional rhythm and complete right bundle branch block in a patient with the Wolff-Parkinson-White Syndrome (type B)

During an attack of tachycardia in a 55-year-old Chinese woman, continuous electrocardiographic monitoring showed the unique changes of, firstly, atrial flutter with aberrant conduction; secondly, a supraventricular tachycardia and junctional rhythm with QRS complexes showing a complete right bundle branch block pattern; and lastly, sinus rhythm with evidence of the Wolff-Parkinson-White Syndrome (type B) and complete right bundle branch block in the same scalar electrocardiogram.     

Spontaneous gap phenomenon in atrioventricular conduction produced by His bundle extrasystoles.

A gap in atrioventricular conduction is a zone within the cardiac cycle during which premature impulses are blocked in the conduction system, while impulses of greater or lesser prematurity are conducted. This has previously been produced only by atrial or ventricular stimulation techniques. This report demonstrates a spontaneous gap produced by His extrasystoles.     

Prediction of right ventricular systolic pressure in pulmonary stenosis from combined vectorcardiographic data

In 38 patients with isolated unoperated pulmonary stenosis a systematic search was made for optimal VCG criteria for the prediction of peak systolic right ventricular pressure. Fifty VCG measurements, seven ECG measurements, and age of each patient were entered into a stepwise multiple regression computer program.The best individual predictors were found to be the QRS loop rotation in the horizontal plane and the closely related QRS dislocation along the 135 to 315 degree horizontal plane axis (r = 0.78). Five VCG criteria were better than the best ECG criterion (R V₁, r = 0.72). Thirty-three of the 58 variables showed significant correlations with the pressure (p < 0.01). Since the confidence intervals are large with this sample size and degree of correlation, conclusions regarding the superiority of one predictor vs. another should be drawn with great care.The multivariate equation selected by the computer involved four VCG variables and age; this improved the correlation coefficient to 0.93. This improvement from data combination is larger than in previous studies, probably because all variables were given equal opportunity to enter the equation.The results were tested on a secondary sample of 19 patients with pulmonary stenosis as their main cardiac lesion. Although this sample was less homogeneous, the formula-derived pressure estimates remained reasonably good (r = 0.88). The study suggests that the diagnostic power of ECG and VCG could be increased through the proper combination of easily obtainable measurements.     

Prediction of hemodynamic data in atrial septal defects of secundum type from simple and combined vectorcardiographic data

A search for simple and combined VCG data which could optimally predict right ventricular systolic pressure (RVSP) or shunt size was made in 50 patients with atrial septal defects of the secundum type. VCG was recorded by means of the axial lead system and a multiple regression computer program was applied. Fifty-four VCG data, age, sex, and systolic blood pressure were tested as independent predictors.Seventeen VCG data were significantly correlated with RVSP and six with flow. The best individual variable was the simple maximal negative deflection in Lead X (r = 0.64, p < 0.001). The correlations with flow were poorer, but of theoretical interest. Distinctive differences in the VCG-RVSP relationships were found in atrial septal defects compared with those in pulmonary stenosis, indicating that the increased flow sensitizes the right ventricle to the effect of pressure.Through multiple regression analysis, an equation based on four vectorcardiographic variables was derived. This equation improved the RVSP-VCG correlations significantly (p < 0.05, r = 0.80). The study confirms that vectorcardiogram is a reasonably reliable method for estimating RVSP in patients with atrial septal defects and that the use of combined VCG data may improve the method considerably.     

The relative risk of spontaneous complete atrioventricular block in elderly patients with impaired intra-ventricular conduction.

We reviewed 144 consecutive patients with symptomatic high grade atrioventricular block. Cases due to congenital heart disease, acute myocardial infarction, cardiac surgery or digitalis toxicity were excluded. Of the remaining, we chose 71 patients in whom atrioventricular conduction was observed either intermittently during complete heart block (CHB) or in electrocardiograms taken within two years prior to documentation of CHB. The mean age was 69 years, with the peak incidence in the seventh decade in 43 men and eight decade in 28 women. Bundle branch block (BBB) was present in 76% of patients as follows: 47% had right BBB (20% with normal QRS axis, 20% with left axis deviation and 7% with right axis deviation), 17% had left BBB (11% with normal QRS axis and 6% with left axis deviation) and 12% had either alternating BBB, right BBB with alternating axis deviation or atypical BBB. "Trifascicular block" patterns accounted for 21% of the total group of CHB. We also studied the prevalence of various patterns of BBB in a group of 2000 random hospital patients of comparable age and sex exclusive of those with acute myocardial infarction and heart surgery. The risk of CHB for the various patterns of BBB was calculated relative to normal intraventricular conduction. All patterns of BBB carried a considerably increased relative risk of CHB, (P smaller than .01). The relative risk was highest for RBBB with left axis deviation and lowest for LBBB with normal or left axis deviation. In the men, 74% had QRS patterns of "bifascicular" or "trifascicular" block during atrioventricular conduction. By contrast, 71% women had atrioventricular beats showing either no BBB or right BBB with normal QRS axis. QRS pattern during CHB was unchanged from that during atrioventricular conduction in 52% if cases (rabge 38%-76% with different QRS patterns) suggesting idiojunctional pacemaker. CHB in these cases was thought to be due probably to coexistent disease in the AV node or His bundle. Although the concept of uni-, bi- and trifascicular block patterns has been useful in identifying patients at greater risk of CHB, the predictability of the electrocardiogram has obvious limitations, particularly in women.