Adaptive filtering in exercise high resolution ECG as applied to the hypertrophic cardiomyopathy

The application of adaptive filtering to ECG signals has been investigated for many years. This study shows that the exercise high resolution ECG (HRECG) can also be processed successfully in a similar way. Two groups were included consisting of 20 healthy individuals and 24 patients with hypertrophic cardiomyopathy (HCM). The HRECG parameters for both groups were similar (QRSdur: 107 +/- 7 vs 114 +/- 18 ms NS, LAS: 25 +/- 8 vs 22 +/- 6 ms NS). In the first step, the HRECG signal was acquired at rest to obtain the averaged reference pattern. The next step was associated with peak exercise in which one could calculate short duration averaging (approximately 30 beats) or apply adaptive filtering in which the exercise component (EC) was extracted. Exercise was performed in the supine position on a bicycle ergometer. The load of 50 W was incremented by 50-W steps in 3-minute intervals and the test was ended by fatigue. Signals were recorded in X, Y, and Z bipolar leads with a 20-Hz high pass filter. The short time average QRS duration mostly was abbreviated in normal individuals in contrast to HCM patients in which ventricular activity prolonged with sensitivity, specificity, and negative and positive predictive values: 79%, 65%, 73%, and 72%, respectively. The adaptive recurrent filtration (ARF) after cutoff of the EC at the level of 70 ms (this level is the EC mean value of both groups) showed the following statistics: 63%, 90%, 88%, and 90%. The Student's t-test as applied to the duration of EC allowed a statistically significant difference between normals and HCM patients (66 +/- 4 vs 71 +/- 6 ms, P < 0.0052) and between HCM patients with and without ventricular tachyarrhythmia and DS (74 +/- 6 vs 69 +/- 6 ms, P < 0.046).

[Selective catheter ablation of the slow pathway in a patient with recurrent atrioventricular nodal reentrant tachycardia]

The case of a 35 year-old patient with recurrent, sustained atrioventricular nodal reentry tachycardia (AVNRT)--type slow/fast--refractory to group IA, IC, II, IV antiarrhythmic agents is presented. The maximum rate of the tachycardia was 280/min. During the antiarrhythmic treatment with group IA, IC and IV agents the tachycardia rate was 230/min. The effective refractory period (ERP) of the slow pathway was 200 ms in antegrade direction. ERP of the fast pathway was 260 ms in antegrade and 210 ms in retrograde direction. Ablation of the slow pathway was performed with radiofrequency energy (device HAT 200 S manufactured by Osypka GMBH, catheter Cereblate No 6). The total ablation time was 96 s, maximal temperature of the effective ablation time was 51 centrigrades. Total energy delivered was 2316 J. The ablation caused neither atrioventricular conduction block nor any damage to the heart structure other than the slow conduction pathway. After the ablation there are no evidence of conduction through the slow pathway. Conduction in anterograde and retrograde direction occurs through the fast pathway. No AVNRT were observed. After ablation the patient has no antiarrhythmic treatment.

[Electrical ablation with high frequency (radiofrequency) in patients with recurrent atrioventricular nodal reentrant tachycardia--introductory information]

In 10 patients (pts) with atrioventricular nodal reentrant tachycardia type slow/fast (AVNRT) refractory to the antiarrhythmic treatment, radiofrequency current catheter ablation was performed. Adult pts (mean age 31 years) suffered from paroxysms of AVNRT for 2 to 18 years (mean 8 years). Episodes of arrhythmia recurred from 2-3 times a week to 1 for several months during antiarrhythmic therapy. The mean rate of the tachycardia was 243/min. 3 pts had syncope and 5 fainted during the tachycardia. In 2 females mitral valve prolapse was diagnosed. Programmed stimulation of the right atrium on the basic rate 130/min revealed ERP of the slow pathway mean 238 ms and ERP of the fast one mean 346 ms. The tachycardia has been induced with right atrium stimulation--most often programmed or burst stimulation--200 and 220/min, sometimes with incremental pacing. Successful radiofrequency energy ablation was performed in all 10 pts. Average number of the impulses for one pt was 7.7 (from 1 to 18 impulses). The total average time of the ablation was 216 s. The temperature of effective ablation was average 65 centigrade. The effect of the ablation was evaluated during repeated electrophysiological study before and after intravenous injection of atropine. Ablation was considered successful when no tachycardia was induced. P-R interval did not change and no episodes of AVNRT was observed in the 1-3 months follow-up. No complications were observed during the ablation and after the procedure, especially no thromboembolism was noticed. The echocardiographic evaluation revealed no damage to the heart structure. The pts receive no antiarrhythmic treatment and they are systematically controlled.

Early and late potentials in postinfarction patients

Injury within the myocardium may cause disturbances of the intraventricular conduction and may be manifested by altered spectrum of the QRS complex. The purpose of this report is to indicate the existence of microvolt early waves appearing at the beginning of the QRS complex in some postinfarction patients with low ejection fraction. The method used incorporated the high resolution ECG recording, where the "pyramid" electrode location was applied. Results indicated a relationship between high frequency potentials, QRS duration time, and ejection fraction, as well as dependence between ventricular tachycardia/fibrillation (VT/VF) occurrence and early and/or late ventricular activity. In patients with secondary VT/VF where early and late potentials were found, the ejection fraction (EF) was the lowest (26 +/- 15%). Early waves appeared more often in patients with secondary VT/VF (30%) compared with those with primary VT/VF (8%). In patients without VT/VF and without myocardial infarction (MI) early potentials were not remarked. In those patients late potentials also appeared less often. It could be concluded that existence of early potentials, late activity, and significant prolonged total ventricular activation time is associated with wide dispersion and nonuniform delay of the electrical activity within the myocardium as well as with serious lowering of the ejection fraction. Therefore, existence of early waves seems to be a significant diagnostic factor for the poor hemodynamic condition as well as a serious warning for the recurrent late ventricular tachycardia/fibrillation.

[Electrocardiography of high resolution in the diagnosis of arrhythmogenic dysplasia of the right ventricle]

To assess the diagnostic value of high resolution ECG in ARVD which is a rare and diagnostically difficult disease, cardiac micropotentials were evaluated in 32 pts with ventricular arrhythmias with LBBB pattern and right axis deviation. Typical ECG-, ECHO-, angiographic features of ARVD were found in 9 pts (mean age 36 y, VT 8 pts, MAS-5). Normal right ventricle (NRV) (Echo, Tc99) was seen in 23 pts (mean age 36 y, VT-14 pts, MAS-6). 25 healthy man (mean age 28 y) served as control (C).

RESULTS

[table: see text] Morphology of total QRS complex in pts with ARVD, comparing to NRV pts and C, was exceptionally characteristic: it was composed of high frequency notches seen not only as prolonged LP but also within fundamental QRS complex.

CONCLUSION

In pts with ARVD beside presence of LP, significantly prolonged TVAT and characteristic notches within QRS complex are observed, therefore the high resolution ECG is a promising method in noninvasive diagnosis of ARVD.

[Multi-electrode mapping from thoracic surface in patients with Wolff-Parkinson-White syndrome]

Body surface potentials mapping is a new method of heart electric phenomena visualisation. Attempts of accessory conduction pathways localisation in 9 patients with overt and in 1 with concealed WPW syndrome are presented. In 4 pts the preexcitation with QRS complex > 120 ms was clearly seen, in next 4 individuals that symptom was less evident and in one case the retrograde conduction through the accessory pathway was hardly noticed. The isopotential maps allowed precise localisation of the accessory pathways ventricular insertion in all patients with QRS > 120 ms and in one with QRS < 120 ms. After successful dissection of accessory pathways, isopotential maps became normal. In patients with slight signs of preexcitation, noninvasive (transesophageal) or invasive atrial stimulation could improve the visibility of accessory pathways localisation.

[Early results of surgical treatment of patients with Wolff-Parkinson-White syndrome]

Successful dissection of accessory pathways (AcP's) was performed in 19 of 20 patients. 15 pts had single, 4 double and 1 patient had 3 accessory pathways (AcP's). The patient with 3 AcP's was operated twice. During the first operation two AcP's were eliminated. The third one was revealed during the postoperative electrophysiologic study. Verapamil facilitated its manifestation and localisation. No patient had syncope or atrio-ventricular tachycardia after the operation. In 3 of 10 patients who had atrial fibrillation before the operation, episodes of AF occurred in the early postoperative period. Conduction to the ventricles was through the normal conduction system. Dissection of AcP's prevented extremely fast ventricular response and syncope. After discontinuation of amiodarone more frequent ventricular premature beats occurred in patients with long history of cardiac arrhythmias, on drugs for a long time and in patients who had heart dilatation. Several months after the operation VEB were less frequent, probably because tachycardias did not occur, left ventricle geometry improved, and cardiodepressant drugs were discontinued. Previously these patients had been treated usually with combination of 2-3 such drugs. After the successful dissection of AcP's the patients lost the feeling of illness and do not feel being imperilled. Children can attend schools normally and some adult patients resumed their professional activities.

[Clinical and electrophysiological indications for surgical treatment in patients with Wolff-Parkinson-White syndrome]

20 patients with WPW syndrome and recurrent tachyarrhythmias were studied clinically and electrophysiologically. The localization and electrophysiological properties of accessory pathways and other heart structures were estimated before the surgical treatment. 13 patients (pts) suffered syncope in the course of atrial flutter or atrial fibrillation with heart rate greater than 300/min, often proceeding into ventricular fibrillation or atrioventricular tachycardia greater than 260/min, which sometimes proceeds into atrial/ventricular fibrillation. 6 pts experienced dizziness or fainted during tachyarrhythmias or rhythm changes. In 15 pts antiarrhythmic drugs in monotherapy or various combinations did not prevent recurrence of tachyarrhythmias. In 4 of 5 other pts only amiodarone was effective but the drug was discontinued due to serious adverse effects. The lack of good effect of antiarrhythmic drug therapy can be based on mutually unfavorable electrophysiologic properties of the accessory pathways and other heart structures. Pts who experienced syncope had a particularly short effective refractory period (ERP) of the accessory pathways in ante- and retro-grade direction and short ERP of the ventricle muscle. Additionally, there were multiple accessory pathways, heart muscle impairement and frequent ventricular premature beats--factors triggering the tachyarrhythmias.

Pyramid electrode location in a cardiac micropotential study

There are several electrode systems dealing with low noise, body surface, and ECG recordings that have been suggested by various investigators. In the last few years, the most developed system for late potential detection has been related to the uncorrected Frank XYZ leads. However, for His bundle detection many different electrode networks have been used. A pyramid-type electrode system has been used previously for His-Purkinje signal measurement and, with some modifications, for late ventricular activity recordings. This pyramid-type system was used to evaluate 300 adult patients with coronary heart disease (CHD) or cardiomyopathy. In the proposed system, electrodes are located near the myocardium with their configuration consisting of three electrode pairs forming a pyramidal shape. Each electrode can also play the role of the top of the pyramid, with all measurement directions converging to a point. By changing the pyramidal top, signals can be detected in various chosen measurement directions. The pyramid system provides spatial averaging facility, allowing the whole measuring system (consisting of low noise multi-input amplifiers) to detect signals in the range of 1 microVp-p on a beat-to-beat basis. In the majority of cases in hospital environments, however, a number of digital averaging cycles is still necessary. Using this system, late potentials (LP) were found in 29% of the patients without myocardial infarction (MI) and in 86% of cases with remote MI and sustained ventricular tachycardia (VT) and/or ventricular fibrillation (VF). Waveforms suspected to be of His-Purkinje System (HPS) origin were detected in 71% of subjects with normal or prolonged P-R segment.

Noninvasive recording of His-Purkinje system [HPS] activity in man on beat-to-beat basis

Since 1969 His bundle electrography has been used for diagnosis and for the study of cardiac electrophysiology. This method has employed the catheterization technique and has allowed the continuous recording of electrical activity of the specialized cardiac conduction system in every beat. Such investigation, because of its invasive nature, cannot be considered a routine test; it requires expensive instrumentation, it has physiological and technical limitations that include discomfort, a slight morbidity risk and a rather limited recorded area within the heart. In 1973 a method was developed for a noninvasive recording of the electrical activity within the P-R segment of the electrocardiogram measured from the body surface. This method which employs the signal averaging technique delivers even less medical information than intracardiac measurement. The shortcomings of this averaging method include inability to detect beat-to-beat changes in the true signal. Such a method is not useful in transient arrhythmia detection and a "short acting" drug influence examination. The technical approach to the beat-to-beat noninvasive recording of the HPS activation signal as measured from the body surface has been proposed. Using a specially positioned electrode system, a low noise multiple parallel input amplifier and a computer for sampling, processing and plotting of the measured signal, we have obtained an output curve corresponding to the continuous beat-to-beat HPS activity.