Value of different non-invasive methods for the recognition of arrhythmogenic complications in high-risk patients with sustained ventricular tachycardia during programmed ventricular stimulation

It is well known that patients with coronary heart disease and ventricular tachycardia show a high incidence of arrhythmogenic complications and sudden cardiac death. The best predictor of spontaneous ventricular tachycardia and sudden death in these patients is programmed ventricular stimulation, but this invasive method is limited to specialized institutions. The purpose of our study was to assess the predictive value of Holter monitoring, late potentials and heart rate variability as markers for these high-risk patients. We investigated 20 patients (18 m, 2 f, age range 31-79 years) with coronary artery disease documented angiographically (6 patients with single vessel disease (vd), nine patients with 2 vd, five patients with 3 vd) and previous myocardial infarction. Each patient underwent 24-h ambulatory monitoring with analysis of rhythm of heart rate variability (24-h spectral and non-spectral analysis) and a signal-averaged ECG with late potential measurement. In all patients, sustained ventricular tachycardia was inducible during programmed ventricular stimulation. Late potentials were recorded in 12 out of the 20 patients (60%). Ventricular arrhythmias of Lown classes IVa, IVb or V were recorded in 12 patients. Analysis of heart rate variability compared to 20 age- and sex-matched healthy controls revealed a loss of parasympathic activity and increased sympathic activity in 16 of the 20 patients (80%).

CONCLUSION

in this study, heart rate variability was the most sensitive method with which to recognize patients at a high risk of arrhythmogenic complications. Evaluation of the above parameters in large controlled clinical trials may help predict arrhythmogenic complications and sudden cardiac death.

The arrhythmogenic substrate of the long QT syndrome: genetic basis, pathology, and pathophysiologic mechanisms

The Long QT syndrome (LQTS) is a relatively rare disorder. It has a major clinical impact as affected individuals are prone to syncope and sudden arrhythmogenic cardiac death. The LQTS comprises three groups of patients. The Jervell-Lange-Nielsen syndrome is characterized by an autosomal recessive pattern of inheritance and congenital neural deafness. The Romano-Ward syndrome shows an autosomal dominant pattern of inheritance and normal hearing. Patients with the sporadic form of LQTS have no evidence of familial transmission and have normal hearing. Imbalance of sympathetic cardiac innervation with predominance of the left stellate ganglion and an intrinsic myocardial defect leading to early afterdepolarization are the two pathogenetic mechanisms of LQTS discussed today. More recently a genetic basis for the Romano-Ward LQTS has been reported. The genetic linkage to the Harvey ras-1 gene provides the basis for a new hypothesis that an impairment of guanine nucleotide binding proteins is responsible for symptoms observed in LQTS. This paper discusses the genetic basis, pathology and pathophysiology of LQTS and tries to unify the different theories.

Magnetocardiography: three-dimensional localization of the origin of ventricular late fields in the signal averaged magnetocardiogram in patients with ventricular late potentials

The purpose of this study was to detect ventricular late fields recorded by a biomagnetic multichannel system in patients with ventricular late potential and to determine the site of these ventricular late fields non-invasively in three dimensions. Biomagnetic signals of sinus beats during a 5-min acquisition period simultaneously recorded by a 37-channel system Krenikon were averaged in all channels. Ventricular late fields were determined in each channel according to the algorithm of Simson for ECG data. For the localization process, baseline correction from the averaged non-filtered signals was performed at the end of the QRS complex under visual control. The single current dipole model within the homogeneous half-space was applied. Eight patients post myocardial infarction with ventricular late potentials (four with recurrent sustained ventricular tachycardia) and four healthy individuals were examined. In the normal subjects, no ventricular late fields were detected. However, ventricular late fields were found in all patients, and were localized in six patients within the border zone of myocardial infarction. In the four patients with ventricular tachycardia, a spatial coincidence of the site of origin of ventricular late fields and the site of origin of ventricular tachycardia determined by catheter mapping was found in two. It is concluded that magnetocardiography is able to detect ventricular late fields and can be used to determine their site of origin.

Pharmacological therapy in coronary heart disease: prevention of life-threatening ventricular tachyarrhythmias and sudden cardiac death

Life-threatening ventricular tachyarrhythmias are the main reason for sudden cardiac death in coronary heart disease. In the majority of survivors of cardiac arrest, malignant tachyarrhythmias generate from a structurally fixed arrhythmogenic substrate following myocardial infarction without evidence of acute ischaemia. Thrombolysis in acute myocardial infarction improves the electrical stability as elucidated by electrophysiological studies and the signal averaged surface ECG. In post-infarction patients, beta-blockers provide significantly beneficial effects on arrhythmic outcome, particularly in the presence of impaired left ventricular function, whereas calcium antagonists and vasodilators are of no affect or may worsen the prognosis. In survivors of myocardial infarction, the prophylactic use of class I antiarrhythmic agents, which are able to suppress frequent single or complex premature ventricular contractions, cause worsening of the prognosis due to their proarrhythmic properties. However, arrhythmia suppression by antiarrhythmic agents selects patients who are at very low risk for arrhythmic death. Pilot trials using class III antiarrhythmic agents suggest beneficial effect on the reduction of sudden death mortality. As regards secondary prevention of malignant tachyarrhythmias in survivors of ventricular tachycardia or fibrillation, there is controversy about the importance of Holter monitoring or invasive electrophysiological testing in the evaluation of drug efficacy. In patients with severely impaired left ventricular function, pharmacological treatment is of limited efficacy. Even in cases of significant suppression of spontaneous or inducible tachyarrhythmias documented by Holter recording or programmed ventricular stimulation, the arrhythmic outcome is considerably poorer, but it could be influenced by implantable defibrillators. Amiodarone, as a potential alternative to class I antiarrhythmic agents, particularly in patients refractory to conventional antiarrhythmic drugs, shows only limited effects on long-term outcome, which is in part caused by the toxicity of this agent. There is substantial need for new drugs without proarrhythmic properties and particularly for those that correct abnormalities of the automatic nervous system.

Lack of effect of nitrates on exercise tolerance in patients with mild to moderate heart failure caused by coronary disease already treated with captopril

OBJECTIVE

To test the hypothesis that the addition of nitrates improves exercise tolerance in patients with heart failure caused by coronary artery disease already treated with an angiotensin converting enzyme inhibitor and diuretics.

DESIGN

Randomised, double blind, placebo controlled, 16 week treatment periods.

SETTING

Outpatient clinic at a university hospital.

PATIENTS

54 patients with previous myocardial infarction, symptoms of mild to moderate heart failure, left ventricular ejection fraction below 40%, no exercise-induced angina or electrocardiographic signs of ischaemia. Four patients in the nitrate group (n = 24) and one patient of the placebo group (n = 25) were withdrawn from the study.

INTERVENTION

After the patients had been on constant doses of captopril and diuretics for at least 2 weeks, they were randomised to receive a target dose of 40 mg isosorbide dinitrate twice daily or placebo in addition to the continuation of captopril and diuretics.

MEASUREMENTS

Bicycle exercise tests with measurement of gas exchange were carried out before randomisation and after 1, 6, 12, and 16 weeks of the double blind treatment. The change in peak oxygen uptake from control to week 16 was prospectively defined as the main outcome measure.

RESULTS

The increase in peak oxygen uptake from before randomisation tended to be greater in the placebo group (before randomisation 17.4 (3.4) ml/min/kg) than in the nitrate group (before randomisation 17.1 (3.5) ml/min/kg) after 12 weeks (mean increase 1.1 (2.7) v 0.0 (2.7) ml/min/kg, p < 0.12) and 16 weeks (1.7 (3.0) v 0.3 (2.6) ml/min/kg, p < 0.14) of treatment.

CONCLUSION

The addition of nitrates to a baseline treatment consisting of captopril and diuretics did not improve exercise tolerance.

Plasma brain natriuretic peptide and atrial natriuretic peptide concentrations correlate with left ventricular end-diastolic pressure

The present study was designed to investigate whether brain natriuretic peptide (BNP) and atrial natriuretic peptide (ANP) plasma concentrations correlate with left ventricular end-diastolic pressure (LVEDP), pulmonary capillary wedge pressure (PCWP), diastolic pulmonary arterial pressure (DPAP), right atrial pressure (RAP), or ejection fraction (EF). Plasma BNP and ANP levels were determined by commercial radioimmunoassays (Peninsula) after Sep Pak C18 extraction in blood samples withdrawn from the pulmonary artery and the left ventricle or from the left ventricle and the femoral vein in 85 patients undergoing diagnostic cardiac catheterization. Linear and nonlinear regression analysis and the paired sample t-test were applied to the data. Pulmonary arterial plasma BNP and ANP levels showed a close nonlinear correlation with LVEDP (BNP: r = 0.94, p < 0.001; ANP: r = 0.81, p < 0.001), a significant linear correlation with PCWP, DPAP, and RAP, and a significant negative correlation with EF. ANP concentrations decreased significantly from the pulmonary artery to the left ventricle and from the left ventricle to the femoral vein (p < 0.001). BNP levels also decreased significantly between the left ventricle and the femoral vein (p < 0.001), but there was no significant difference between pulmonary arterial and left ventricular BNP concentrations. BNP and ANP concentrations correlated significantly between pulmonary arterial and left ventricular blood samples (BNP: r = 0.99, ANP: r = 0.93, p < 0.001) and between left ventricular and peripheral blood samples (BNP: r = 0.99, ANP: r = 0.94, p < 0.001). The present data suggest that peripheral plasma BNP and ANP levels are useful non-invasive indices of cardiac performance.

Local calcification as a determinant of the outcome of excimer laser coronary angioplasty: an in vitro study

BACKGROUND

Calcification influences the outcome of various angioplasty techniques in the treatment of coronary artery disease. During angioscopic in vitro studies, we observed that dissections and perforations not caused by vessel bending frequently occurred at the boundary areas of plaque and adjacent vessel wall. This study investigated whether this is related to the distribution of calcific deposits.

METHODS

Postmortem excimer laser coronary angioplasty (308-nm XeCl) was performed in 51 stenotic coronary arteries. Twenty-three segments were further examined; these consisted of 11 perforations, six dissections, three segments with no ablative effect after the application of 20,000 laser impulses, and three successfully passed stenoses without complications. X-ray diffraction analysis and scanning electron microscopy were performed to detect calcium deposits and their spatial relationship to perforations and dissections.

RESULTS

X-ray diffractions analysis detected calcifications in 21 of 23 specimens. Postmortem angiography revealed calcifications only on 11 of 23 segments. Three of 11 perforations were located at the plaque border, as were three of six dissections. In all six complications at the plaque border, x-ray diffraction analysis revealed that the plaque border was identical with a border of calcium deposits. Eight of 11 perforations and three of six dissections could be explained by axis divergence between the laser catheter and the vessel orientation.

CONCLUSIONS

Contributing factors for perforations and dissections during excimer laser coronary angioplasty are axis divergence and the distribution of plaque calcification. More sensitive methods are needed to detect local vessel wall calcium in vivo.

Non-invasive three-dimensional localisation of arrhythmogenic foci in Wolff-Parkinson-White syndrome and in ventricular tachycardia by radionuclide ventriculography: phase analysis of double-angulated integrated single photon emission computed tomography (SPECT)

A new tomographic technique combined with phase analysis was used to detect premature and ectopic ventricular contraction patterns in 15 patients with Wolff-Parkinson-White syndrome and during ventricular tachycardia in seven patients. Data generated by gated single-photon emission computed tomography (SPECT) were analysed by backprojection of the Fourier coefficients, double-angulation, and integration to thick slices containing the ventricles, thus allowing visualisation of the contraction patterns in three perpendicular views. The results were compared with those of catheter mapping. In nine patients with Wolff-Parkinson-White syndrome the site of initial contraction detected was identical with the site of the accessory pathway found by catheter mapping. The sites of origin of the ventricular tachycardias determined by catheter mapping were within 3 cm of the sites detected by the new technique. This new technique seems to be a promising non-invasive method for localising ectopic ventricular activity that will considerably shorten the time required for subsequent invasive procedures.

Color Doppler echocardiographic determination of mitral regurgitant flow from the proximal velocity profile of the flow convergence region

Flow rate across an orifice can be determined from color Doppler echocardiographic maps of the flow convergence region proximal to the orifice. Different methods have been developed in vitro. The proximal velocity profile method was prospectively evaluated in patients with mitral regurgitation. Color Doppler echocardiography was performed in 74 patients before cardiac catheterization. The increasing velocities within the flow convergence region were determined in an apical plane on the straight line from the transducer to the leak; thus the proximal velocity profile was established and plotted on a nomogram. Instantaneous regurgitant flow rate was derived from the position of the resulting curve in relation to the nomogram's reference curves, which were derived from in vitro measurements. Regurgitant stroke volume was calculated as regurgitant flow rate.regurgitant velocity-time integral/regurgitant peak velocity, using additional continuous-wave Doppler. The 55 patients with angiographic regurgitation had a close association between regurgitant flow rate (0 to 600 ml/s) and angiographic grade (Spearman's rank correlation coefficient = 0.91; p < 0.0001). Regurgitant flow rate did not overlap between grades < or = 2+, 3+ and 4+. In 16 patients, regurgitant stroke volume by echocardiography correlated well with that by the angiography/Fick method (r = 0.88; SEE = 17.1 ml), with a regression line close to identity (y = 0.89x + 12.7 ml). The proximal velocity profile method enables determination of mitral regurgitant flow and estimation of regurgitant volume.

[The diagnostic value of standard ECG methods, the cold-pressure test and Valsalva maneuver in idiopathic QT syndrome]

The idiopathic Long QT Syndrome is an infrequently occurring disorder. Affected patients usually show ECG alterations and are prone to syncope and sudden arrhythmic cardiac death. Adequate therapy with beta-blocking drugs may significantly improve the prognosis of affected patients. The early and precise diagnosis of the disorder therefore has major prognostic impact. This paper reports the diagnostic significance of standard ECG, exercise stress testing, ambulatory ECG monitoring, cold pressor test and Valsalva maneuver in 14 patients with Long QT Syndrome. The results were compared with those obtained in 14 healthy age matched volunteers. QTc duration was significantly longer in patients with Long QT Syndrome during standard 12-lead ECG at rest (489 +/- 55 ms versus < vs. > 412 +/- 25 ms, p < 0.005), exercise stress test (490 +/- 39 ms vs. 409 +/- 18 ms, p < 0.001), cold pressor test (512 +/- 45 ms vs. 407 +/- 19 ms, p < 0.001), Valsalva maneuver (497 +/- 49 vs. 407 +/- 18 ms, p < 0.001), minimal heart rate during 24-h of ambulatory ECG monitoring (482 +/- 69 ms vs. 402 +/- 22 ms, p < 0.01) and maximal heart rate during Holter monitoring (460 +/- 47 ms vs. 411 +/- 27 ms, p < 0.005). Four of 14 patients with Long QT Syndrome had pathological findings during ambulatory ECG monitoring (two patients showed short episodes of asymptomatic torsade de pointes tachycardia, one patient had an intermittent SA-Block, and one patient showed T-wave alternans). All healthy volunteers had normal ambulatory ECG recordings (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Spatial differences of the duration of ventricular late fields in the signal-averaged magnetocardiogram in patients with ventricular late potentials

Magnetocardiography (MCG) allows one to noninvasively localize cardiac electrical activity in three dimensions. It was the purpose of this study to obtain information about the spatial variations of signal-averaged ventricular late magnetic fields recorded by a biomagnetic multichannel system. Biomagnetic signals of 170-600 heart cycles obtained by the 37-channel system KRENIKON (Siemens Medical Engineering Group) were simultaneously averaged in all channels. The absolute values of the filtered signals (digital, bidirectional, four-pole butterworth, bandpass filter [3-dB range, 40-250 Hz]) were calculated in each channel. The noise level was determined within the TP segment. The onset of the terminal low amplitude signals (TLAS) was defined when the signals became lower than 1/23 of Rmax of the QRS complex for the channel with the largest filtered QRS complex after filtering. The TLAS ended when the signal was lower than twice the standard deviation (2 sigma) above the mean noise level. Ventricular late fields were defined as present when the TLAS had a duration of more than 39 msec. In this study, five patients with ventricular late potentials (four with sustained ventricular tachycardia) and three healthy individuals were examined. Ventricular late fields were detected in the patient group in 2-15 MCG channels with a mean length of 49.6 msec (43-60 msec). The spatial distribution of the ventricular late fields was consistently found to exhibit maximum duration in a certain area. In the normal subjects no ventricular late fields were detected. Thus, MCG is able to detect ventricular late fields and their spatial variations. In addition to the information obtained by signal averaging from the surface ECG, averaging of biomagnetic signals with a multichannel device can reveal spatial inhomogeneity of delayed myocardial excitation.

Ultrasound-guided positioning of temporary pacing catheters and pulmonary artery catheters after echogenic marking

Pacing of the heart is one of the most effective emergency measures in the management of critical bradycardic arrhythmias. Positioning of the pacing catheter is safest under fluoroscopic control; however, this facility is not always readily available in emergency situations. A procedure was therefore developed by which pacing catheters could be easily positioned under echocardiographic control after echogenic marking. It involves the filling of commercially available balloon-tipped pacing catheters with an echogenic substance consisting of galactose microparticles suspended before use in a 0.9% saline solution (Echovist). The balloon on the pacing catheter is then easy to locate intravascularly by ultrasound and can be visually guided into the right ventricle. To date, this method has been used effectively and without complication to position both pacing catheters and pulmonary artery catheters.

Direct current application: easy induction of ventricular fibrillation for the determination of the defibrillation threshold in patients with implantable cardioverter defibrillators

For the determination of the defibrillation threshold, the induction of ventricular fibrillation is mandatory. However, in severely damaged hearts it is sometimes difficult to induce ventricular fibrillation by rapid stimulation or alternating current. Only rapid nonclinical ventricular tachycardias may result, and their cardioversion threshold may be different from the defibrillation threshold. Therefore, it was the purpose of this study to test the potential of direct current (DC) application to rapidly induce ventricular fibrillation in patients with an implanted cardioverter defibrillator. The defibrillation threshold had to be determined in 13 patients (9 with coronary heart disease, 4 with dilative cardiomyopathy, ejection fraction 35%) during and 2 weeks after the implantation of a cardioverter defibrillator. DC was applied 37 times by a commercially available 9-V DC battery via a bipolar catheter for about 3 seconds. Ventricular fibrillation was induced 23 times (62%) and rapid nonclinical ventricular tachycardias were induced six times (16%). In one patient clinical ventricular tachycardia was observed. In seven instances (19%) sinus rhythm remained. In 12 of the 13 patients, ventricular fibrillation could be induced by DC. Thus, the induction of ventricular fibrillation by DC application may serve as an additional tool to induce ventricular fibrillation, determining the defibrillation threshold in implantable cardioverter defibrillator patients.

Massive main pulmonary artery embolism diagnosed with two-dimensional Doppler echocardiography

This report describes the usefulness of echocardiography in the differential diagnosis of acute cardiovascular events. In a 66-year-old patient with known aortic stenosis and mitral valve prosthesis, who suddenly deteriorated with severe dyspnea, a thrombus within the pulmonary artery could be detected with 2-D echo. Pulsed-wave Doppler disclosed the resulting flow-velocity disturbances.

Short-term reproducibility of gas exchange measurements during bicycle exercise in patients with mild to moderate congestive heart failure

A series of 45 patients with congestive heart failure due to coronary disease had semisupine bicycle exercise tests (ramp protocol, 10 W/min) on two occasions separated by 3 to 7 days in order to determine the short-term reproducibility of gas exchange measurements during symptom-limited exercise. The percentage difference (PD) between each pair of measurements (m1, m2; PD = 100%.(m2-m1): m1) were calculated. The mean PD values (+/- 1 sigma) and the single determination standard deviations (SDSD) for exercise tolerance (ET, W), peak heart rate (pHR, 1/min), peak oxygen uptake (pVO2, ml/min/kg), peak carbon dioxide output (pVCO2, ml/min/kg), and peak minute ventilation (pVE, l/min) were as follows: [table: see text] No patient reached a plateau of oxygen uptake during the last portion of the ramp exercise test. Thus, pVO2 is not an objective endpoint. The single determination standard deviations show that exercise tolerance and peak oxygen uptake do not differ as to their reproducibility. The absolute values of PD were not a function of exercise tolerance for any of the parameters studied. The PD values for ET and pVO2 were normally distributed. The data suggest that a change in ET and pVO2 must exceed 27% and 28% between two sequential studies in an individual patient in order to be significant at the 5% level, respectively. For the one-tailed test situation, the changes in ET or pVO2 must be greater than 23% in order to be significant.

Magnetocardiographic non-invasive localization of accessory pathways in the Wolff-Parkinson-White syndrome by a multichannel system

Electrical activity can be localized by magnetocardiography (MCG) non-invasively. In this study a 37-SQUID (Super Conducting Quantum Interference Device) sensor multi-channel system (KRENIKON) was used to assess the potential of magnetocardiography to localize accessory pathways with a multichannel system. Seven WPW patients were studied by means of magnetocardiography. Prior to the MCG recordings, the site of the accessory pathway had been determined in all patients by invasive catheter mapping. MR images of the heart were used for anatomical correlation. The magnetocardiographic localization of the accessory pathway corresponded with catheter mapping within 2.1 cm on average (total range: 0-5 cm). This is thus, a promising new method for non-invasive localization of accessory pathways in WPW patients.

Excimer laser coronary angioplasty: experience with a prototype multifibre catheter in patients with stable angina pectoris

Percutaneous excimer laser coronary angioplasty (ELCA) was performed in a first group of 20 patients with stable angina pectoris caused by significant coronary stenosis, and long-term follow-up was evaluated. Prototype 4 to 5.5 French multifibre catheters with 18-20 quartz fibres of 100 microns diameter, concentrically arranged around a central lumen for taking up a guide wire, were coupled to a commercial XeCl excimer laser. Energy was delivered at a wavelength of 308 nm with a pulse duration of 60 or 120 ns. Operating at a repetition rate of 20 Hz, mean energy transmission was 13.4 +/- 6.8 mJ per pulse. In all but one patient the lesion could be passed by the catheter. Percent diameter stenosis decreased from 77.1 +/- 10.8% to 53.1 +/- 11.8% after ELCA. Complications were frequently observed, intracoronary thrombus formation in eight instances, dissection in six patients and spasm in five cases, causing total vessel occlusion in five procedures. All complications could be managed efficaciously by thrombolytic and vasodilating drugs and/or balloon angioplasty. Subsequent PTCA was performed in case of complication or insufficient stenosis reduction after ELCA in 18 patients with adequate results (residual stenosis, 28.5 +/- 10.2%). Long-term follow-up angiography, which could be performed in 16 of 19 laser treatments, demonstrated significant restenosis in only three patients. Our preliminary results suggest that, using ELCA, ablation of atherosclerotic lesions is feasible in most cases. However, compared with PTCA, stenosis reduction is significantly less, and the acute complication rate is much higher. Thus, further improvements of the catheter system are necessary in order to realize the advantages of excimer laser ablation, which can be demonstrated by experimental studies.

[Determination of normal values of the aortic blood flow profile using continuous Doppler echocardiography from apical and suprasternal echo position]

The present study was undertaken to measure normal aortic blood velocity profiles by means of continuous wave Doppler echocardiography from apical and suprasternal positions in 40 healthy adults. The profiles in the ascending aorta were measured from both positions, whereas the profiles in the descending aorta were measured only from the suprasternal position. The highest values for the maximal flow velocities were found in the ascending aorta from the suprasternal position (1.28 +/- 0.18 m/s), the lowest values for the maximal flow velocities were found in the descending aorta (1.17 +/- 0.22 m/s). This trend was also found for the mean velocity values. As to the time parameters, a longer acceleration time for the descending aorta was remarkable (106 +/- 24 ms), whereby the mean values for the ejection time for the descending aorta (308 +/- 25 ms, suprasternal: 320 +/- 30 ms). The highest values for the acceleration were found in the ascending aorta (suprasternal: 1526 +/- 531 cm/s2, apical: 1422 +/- 330 cm/s2) and the lowest values in the descending aorta (1208 +/- 378 cm/s2). Regarding the maximal velocity index there was no significant difference for the maximal values between the different transducer positions. The results of the regression analysis showed only a weak correlation of the maximal velocity values in the different transducer positions. This means that for follow-up examinations only those values should be used that were obtained from the same transducer position.

Biomagnetic noninvasive localization of accessory pathways in Wolff-Parkinson-White syndrome

It was our purpose to assess the clinical relevance of noninvasive magnetocardiographic localization of accessory pathways. Nine patients with Wolff-Parkinson-White (WPW) syndrome were studied. For all of them the site of the accessory pathway was known from invasive catheter mapping. A 37-SQUID (superconducting quantum interference device) sensor multichannel system (KRENIKON) was used, allowing synchronous registration with all channels. The site of the electrophysiological activity at the beginning of the delta wave was determined. Magnetic resonance images of the heart were obtained to correlate the biomagnetically localized activity with the anatomy. Magnetocardiographic localization of the bypass tract corresponded with catheter mapping with a spatial difference of 0-5 cm, 1.8 cm on the average, compared to the results obtained by catheter mapping. Thus, magnetocardiography is a promising new method for noninvasive localization of accessory pathways in WPW patients. This may streamline further invasive procedures.

Chemical ablation by subendocardial injection of ethanol via catheter--preliminary results in the pig heart

This study was set up to discover how a subendocardial application of ethanol administered via a catheter would affect an animal model. A 7 F bipolar catheter with a lumen, through which a 2 mm needle was inserted, was placed in the left ventricle of 11 pigs. Altogether, 33 subendocardial injections into the left ventricular myocardium were performed under fluoroscopic control using a mixture of 0.5-1.5 ml ethanol and 0.5-1 ml iopamidol as contrast medium. The mixtures were injected into the apical, lateral and septal walls of the left ventricle. After 25 days, the hearts were removed and the lesions examined pathologically. The calculated volume of the lesions was about 60 mm3, the area in projection to the endocardium about 35 mm2, the depth relative to the endocardium about 1.5 mm and the maximum diameter about 8 mm. Perforation of the myocardial wall by pericardial injection occurred twice without further complications. Subendocardial application of concentrated ethanol by catheter caused a controlled local necrosis. This technique may become a new approach with which to treat ventricular tachycardia by chemical ablation.

Effects of atenolol, slow-release nifedipine, and their combination on respiratory gas exchange and exercise tolerance in stable effort angina

The effects of atenolol, nifedipine, and their combination on gas exchange and exercise tolerance were studied in 27 patients with effort angina and normal global ventricular function in an open-label and randomized cross-over trial. Symptom-limited semi-supine exercise tests using a ramp protocol (20 W/min) with simultaneous breath-by-breath analysis of gas exchange were carried out after a 4-day wash-out period and after consecutive 2-week treatment periods with atenolol (50 mg b.i.d.), slow-release nifedipine (20 mg b.i.d.), and their combination (b.i.d.). Exercise tolerance was not significantly higher with atenolol than with nifedipine [118(24) vs 113(23) W]. Combination therapy [120(23) W] was more effective than monotherapy with nifedipine (p less than 0.05) but produced no further increase in exercise tolerance over atenolol monotherapy. Maximum oxygen uptake was not significantly different among the treatments. In the range of light to moderate exercise, the slope of the VO2-workload regression line expressed as ml.min-1.W-1 was lower with atenolol than with nifedipine [8.64(1.59) vs 10.28(1.74), p less than 0.005] and intermediate with combination therapy [9.99(1.83)]. The intercept on the VO2 axis was higher with atenolol than with nifedipine [366(111) vs 299(113) ml.min-1, p less than 0.05]. A similar pattern of results was seen when the drug effects on the slope of the VCO2-workload relation were analyzed. VE was higher with nifedipine than with atenolol at all points of the regression analysis [greater than 30 W].(ABSTRACT TRUNCATED AT 250 WORDS)

Localization of ectopic ventricular depolarization by ISPECT-radionuclide ventriculography and by magnetocardiography. ISPECT and MCG for ectopic mapping

Since catheter or surgical techniques for ablating the arrhythmogenic substrate in patients with SVT due to accessory pathways or those with VT are now available, exact localization of the substrate is mandatory. We report preliminary results of two new non-invasive techniques for localizing either the site of earliest ventricular contraction using ISPECT, or the site of initial ventricular depolarization by magnetocardiography (MCG) in WPW syndrome and in VT patients. Thirteen patients with WPW syndrome and 8 patients with sustained VTs were studied with ISPECT. In 9/13, comparative catheter mapping data were available. Two patients had two Kent bundles. 13/15 Kent bundles could be localized by ISPECT. In 5/9 patients the area of Kent bundle insertion was identical with ISPECT and catheter mapping, in 3 correlation was fair, and in 2 patients with 2 Kent bundles ISPECT failed to localize their insertion. In 3/8 patients with VT catheter mapping could not be performed for hemodynamic reasons. In 2/5 patients the area of VT focus was identical with both methods, in one patient it was adjacent to each other, and in 2/5 patients a larger anatomic distance of the focus was found with both methods. In 3/7 patients with WPW the MCG showed the site of Kent bundle insertion, which was identical to that seen by catheter mapping. In one patient the area was adjacent, and in 3 more distant from the site determined by catheter mapping. In 1/2 patients with 2 Kent bundles, one of these could be detected by MCG. In 1/3 patients with VT, the site of VT focus was identical with both methods, but in the remaining two a distance of 3-4 cm was observed between the area seen with MCG and that with catheter mapping. In 4 further VT patients with stable and uniform ventricular late potentials, ventricular late magnetic activity was found with different QRS lengths within the single MCG channels. From our results we conclude that both ISPECT and MCG seem to become very promising non-invasive techniques for localizing ectopic ventricular depolarization in WPW syndrome and VT patients. However, these methods have to be refined, improved and validated by further systematical studies.

[Implantation of Strecker stents in the iliac and femoropopliteal region]

The aim of implanting vascular endoprosthesis is to avoid acute complications and restenosis after percutaneous transluminal angioplasty. The Strecker stent is a new development, based on the principle of balloon-expandable endoprosthesis. We treated seven patients (five male, two female) aged 48 to 84 years (average 68 years) with Strecker stents in the iliac and femoropopliteal region. The indications for the implantation of stents were restenosis, reocclusion, recoiling, and kink stenosis. Also, acute complications as dissection or intimal flaps after PTA were stented. The implantation of the Strecker stents was in every case without technical complications. The condition of three patients suffering from a stage III, according to Fontaine's classification, improved to stage IIa after treatment. In three out of four patients with a stage IIb, clinical symptoms were changed to stage IIa after stenting. One patient had an acute thrombosis during the intervention, which could not be solved by local thrombolysis. The Doppler sonographic index increased after treatment to an average of 0.31. The follow-up period up to six months showed persistent clinical improvement. Intimal hyperplasia with stent occlusion or thromboembolic occlusions was not observed. The Strecker stent is a technically non-problematic system, which is qualified for the endoprosthetic therapy of the iliac and femoropopliteal region.

[Localization of premature and ectopic ventricular depolarization using a new nuclear medicine tomographic technique]

In planar radionuclide ventriculography (RNV) identification of the site of initial contraction is possibly by the Fourier phase. First clinical experiences will be presented with a new integrated tomographic technique--ISPECT--in noninvasively assessing the site of ectopic or premature ventricular depolarization. In six patients Fourier phases of RNV and ISPECT were performed and compared in five with results from the corresponding electrophysiologic study. It was possible to exactly localize the beginning of mechanical contraction in the two orthogonal planes: during pacemaker stimulation at the apex of the right ventricle, at the lateral border of a large aneurysm during ventricular tachycardia, and at the site of three of five WPW bundles. In the other two bundles the site of first contraction was near the area found during invasive mapping procedure. Thus, this new ISPECT approach together with planar radionuclide imaging may help in noninvasively localizing the site of ectopic and premature depolarization in addition to surface ECG.