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Biomedical subjects

S A Ben-Haim

Publications and source records attributed to S A Ben-Haim.

At least 19 recordsLinked to original sources
PubMed1998

Preliminary animal and clinical experiences using an electromechanical endocardial mapping procedure to distinguish infarcted from healthy myocardium.

BACKGROUND: A catheter-based left ventricular (LV) endocardial mapping procedure using electromagnetic field energy for positioning of the catheter tip was designed to acquire simultaneous measurements of endocardial voltage potentials and myocardial contractility. We investigated such a mapping system to distinguish between infarcted and normal myocardium in an animal infarction model and in patients with coronary artery disease. METHODS AND RESULTS: Measurements of LV endocardial unipolar (UP) and bipolar (BP) voltages and local endocardial shortening were derived from dogs at baseline (n=12), at 24 hours (n=6), and at 3 weeks (n=6) after occlusion of the left anterior descending coronary artery. Also, 12 patients with prior myocardial infarction (MI) and 12 control patients underwent the LV endocardial mapping study for assessment of electromechanical function in infarcted versus healthy myocardial regions. In the canine model, a significant decrease in voltage potentials was noted in the MI zone at 24 hours (UP, 42. 8+/-9.6 to 29.1+/-12.2 mV, P=0.007; BP, 11.6+/-2.3 to 4.9+/-1.2 mV, P<0.0001) and at 3 weeks (UP, 41.0+/-8.9 to 13.9+/-3.9 mV, P<0.0001; BP, 11.2+/-2.8 to 2.4+/-0.4 mV, P<0.0001). No change in voltage was noted in zones remote from MI. In patients with prior MI, the average voltage was 7.2+/-2.7 mV (UP)/1.4+/-0.7 mV (BP) in MI regions, 17.8+/-4.6 mV (UP)/4.5+/-1.1 mV (BP) in healthy zones remote from MI, and 19.7+/-4.4 mV (UP)/5.8+/-1.0 mV (BP) in control patients without prior MI (P<0.001 for MI values versus remote zones or control patients). In the canine model and patients, local endocardial shortening was significantly impaired in MI zones compared with controls. CONCLUSIONS: These preliminary data suggest that infarcted myocardium could be accurately diagnosed and distinguished from healthy myocardium by a reduction in both electrical voltage and mechanical activity. Such a diagnostic electromechanical mapping study might be clinically useful for accurate assessment of myocardial function and viability.

Animals↗
PubMed1998

New method for nonfluoroscopic endocardial mapping in humans: accuracy assessment and first clinical results.

BACKGROUND: Accurate mapping of the site of origin and activation sequence of a cardiac arrhythmia is essential for a successful catheter ablation procedure. To achieve this, precise and reproducible catheter manipulation is mandatory. The aim of this study was (1) to assess the accuracy of a new nonfluoroscopic mapping system in humans and (2) to report the first result of endocardial activation mapping with this system during sinus rhythm and several types of supraventricular and ventricular tachycardias. METHODS AND RESULTS: Fifteen patients were studied. Accuracy measurements were performed in 5 of them (patients 5, 6, 7, 8, and 14). The distances between two subsequent catheter positions in the inferior caval vein as determined by the nonfluoroscopic mapping system were compared with measurements made with calipers by four independent investigators using identification marks on the catheter shaft. The difference between these two methods was 0.95+/-0.8 mm. In 15 patients, activation of the right atrium and/or the right or left ventricle was recorded during sinus rhythm. Three-dimensional activation maps were constructed in patients with atrial and ventricular tachycardias and Wolff-Parkinson-White syndrome. CONCLUSIONS: With this new nonfluoroscopic mapping technique, accurate positioning of the catheter tip is possible. A three-dimensional activation map can be reconstructed during sinus rhythm and during supraventricular and ventricular tachycardias of different compartments of the heart.

Adolescent↗
PubMed1998

System response of the sinoatrial node during vagal stimulation.

The SA node response to modulations in canine vagal tone was investigated by means of the heart rate variability power spectrum. A new algorithm that was developed for accurate power spectrum estimation of short R-R segments is described. The performance of the algorithm was assessed for ECG recordings obtained from a controlled experiment, in which a frequency modulated pulse train was applied to the vagal nerve after vagal transaction and blockade of the sympathetic system. The power spectrum calculated for 20-25 heartbeats showed conspicuous spectral peaks in accordance with the different modulating frequencies between 0.1 and 0.3 Hz. The presence of spurious peaks was negligible even when the analysed signal segment consisted of only 20-25 beats. These results imply that for a certain range of modulating frequencies the sinoatrial node responds linearly to fluctuations in the parasympathetic tone. System identification methods that include fitting a linear model to the heart rate variability signal and analysis of the residuals were used for confirming the hypothesis of linearity. For higher frequencies of the modulating signal, usually above 0.3 Hz, the system was found to deviate from linearity.

Animals↗
PubMed1998

Nonfluoroscopic endocardial catheter mapping of atrial fibrillation.

The treatment of drug-refractory atrial fibrillation (AF) remains one of the unsolved problems in cardiology. Surgical interventions have demonstrated that AF can be prevented by multiple incisions within both atria. Recently, this strategy has been translated into a catheter procedure. So far, the ablation approach is not based on individual electrophysiologic data, but constitutes only an anatomic approach. Further insight into the spatial and temporal distribution of the local electrograms during AF is needed. Electroanatomic maps acquired by sequential mapping over 45 seconds at each site during AF in six patients with paroxysmal AF were analyzed off-line. Electrograms were sampled at a mean of 36 +/- 12 sites in the left atrium of each patient. A total of 217 sites were sampled, of which 27.3% (59) represented type A (regular) AF, 9.7% (21) represented type B (totally irregular), and 63.1% (137) represented type C (mixture of type A and B) electrograms. The distribution was analyzed in 20 different segments of the left atrium, and a significantly higher incidence of type A electrograms was found in area 3 (upper lateral pulmonary vein) than at all other sites (P < 0.005). This observation needs further confirmation before any conclusion with regard to catheter ablation can be drawn, particularly because the analysis was based on bipolar recordings from a 4-mm tip electrode.

Aged↗
PubMed1997

Activation-repolarization coupling in the normal swine endocardium.

BACKGROUND: While abnormalities of activation and repolarization play an important role in arrhythmogenesis, little information is available on the interaction between their spatial dispersions in the heart. This study examined the effects of activation spread on the spatial distribution of the repolarization properties during different depolarization patterns. METHODS AND RESULTS: Left ventricular (LV) endocardial activation and repolarization patterns were mapped in 13 healthy pigs. LV local activation, repolarization, and activation-recovery interval (ARI) times were determined from the intracardiac unipolar electrograms, color-coded, and superimposed on a three-dimensional anatomic map of the ventricle generated with a nonfluoroscopic mapping system. ARI values correlated with the duration of monophasic activation potential recorded from onset of activation to time of 90% repolarization (r=.97, P<.01). Activation time range of the left ventricle was 42+/-5 ms (mean+/-SEM) during sinus rhythm and 54+/-5 ms during right ventricular septal pacing. ARI inversely correlated with the corresponding activation times during both sinus (r2=.76+/-.03) and paced (r2=.77+/-.02) rhythms. The longest ARIs were located at the sites of earliest activation and shortest at the latest activation areas, with gradual shortening between them. CONCLUSIONS: The spatial distribution of repolarization is dependent on the activation pattern. Repolarization dispersion in the healthy swine heart is relatively small as the result of tight coupling of the action potential duration to the activation process, assigning longer ARIs to sites activated earlier. This coupling reduces global and regional dispersion of repolarization and may serve as an important antiarrhythmic mechanism present in normal myocardium.

Animals↗
PubMed1997

Hemodynamic evaluation of the heart with a nonfluoroscopic electromechanical mapping technique.

BACKGROUND: Clinical cardiac volumetric measurement techniques are essential for assessing cardiac performance but produce significant inaccuracies in extrapolation of the volume of a three-dimensional (3D) object from two-dimensional images and lack the ability to associate cardiac electrical and mechanical activities. In this study, we tested the accuracy of cardiac volumetric measurements using a new catheter-based system. METHODS AND RESULTS: The system uses magnetic technology to accurately locate a special catheter at a frequency of 125 Hz and is currently used in the field of electrophysiology, in which activation maps are superimposed on the 3D geometry of the cardiac chamber. The mapping procedure is based on sequentially acquiring the location of the tip and local electrogram while in contact with the endocardium. The 3D geometry of the chamber is reconstructed in real time, and its volume could be calculated at every time step (8 ms). The volumetric measurements of the system were found to be highly accurate for simple phantoms (mean+/-SEM deviation, 2.3+/-1.1%), left ventricular casts (9.6+/-1.3%), and a dynamic test jig. In addition, left ventricular volumes of 12 swine were measured. Intraobserver and interobserver variabilities were found to be minimal (ejection fraction, 6.5+/-1.9% and 7.1+/-2.0%; stroke volume, 4.5+/-1.0% and 11.3+/-2.4%). Comparison with the thermodilution method for measuring stroke volume showed an average deviation of 8.1+/-2.2%. Typical pressure-volume loops were also obtained. CONCLUSIONS: The new mapping image provides, for the first time, simultaneous information regarding cardiac mechanics, hemodynamics, and electrical properties. Furthermore, all this information is achieved without the use of fluoroscopy, contrast medium, or complicated image processing.

Animals↗
PubMed1997

Guidance of radiofrequency endocardial ablation with real-time three-dimensional magnetic navigation system.

BACKGROUND: Ablation therapy for certain arrhythmias requires the formation of complex lesions based on electrical and anatomic mapping. We tested the accuracy and reproducibility of a nonfluoroscopic mapping and navigation (NFM) system to guide delivery of radiofrequency (RF) energy in the right atrium (RA) of swine. METHODS AND RESULTS: The NFM system uses an ultralow magnetic field to measure the real-time three-dimensional (3D) location of the tip of the locatable catheter. While in stable contact with the endocardium, between 30 and 40 consecutive tip locations were sampled and used for the 3D reconstruction of the RA geometry. The location of the catheter tip was presented in real time, superimposed over the RA geometry. We selected a point on the 3D reconstruction and delivered RF energy to that site via the tip of the locatable catheter. The catheter was then completely withdrawn and renavigated twice to the same point, at which RF energy was delivered again. At autopsy, the distance between the centers of the three ablation points (mean+/-SEM) was 2.3+/-0.5 mm (n=27). Similarly, we used the NFM system to guide the generation of linear lesions. The measured length of the linear lesions on the NFM 3D view was close to the actual lesion length measured at autopsy (correlation coefficient, .96; P=.002; n=6). Furthermore, the location, shape, and continuity of the linear lesions corresponded to the autopsy findings. CONCLUSIONS: We conclude that the NFM system can guide the application of RF energy without the use of fluoroscopy in a highly accurate and reproducible manner.

Animals↗
PubMed1997

A novel method for nonfluoroscopic catheter-based electroanatomical mapping of the heart. In vitro and in vivo accuracy results.

BACKGROUND: Cardiac mapping is essential for understanding the mechanisms of arrhythmias and for directing curative procedures. A major limitation of the current methods is the inability to accurately relate local electrograms to their spatial orientation. The objective of this study was to present and test the accuracy of a new method for nonfluoroscopic, catheter-based, endocardial mapping. METHODS AND RESULTS: The method is based on using a new locatable catheter connected to an endocardial mapping and navigating system. The system uses magnetic technology to accurately determine the location and orientation of the catheter and simultaneously records the local electrogram from its tip. By sampling a plurality of endocardial sites, the system reconstructs the three-dimensional geometry of the chamber, with the electrophysiological information color-coded and superimposed on the anatomy. The accuracy of the system was tested in both in vitro and in vivo studies and was found to be highly reproducible (SD, 0.16 +/- 0.02 [mean +/- SEM] and 0.74 +/- 0.13 mm) and accurate (mean errors, 0.42 +/- 0.05 and 0.73 +/- 0.03 mm). In further studies, electroanatomical mapping of the cardiac chambers was performed in 34 pigs. Both the geometry and activation sequence were repeatable in all pigs. CONCLUSIONS: The new mapping method is highly accurate and reproducible. The ability to combine electrophysiological and spatial information provides a unique tool for both research and clinical electrophysiology. Consequently, the main shortcomings of conventional mapping-namely, prolonged x-ray exposure, low spatial resolution, and the inability to accurately navigate to a predefined site-can all be overcome with this new method.

Animals↗
PubMed1997

3D cardiac imaging of electromechanical coupling.

A novel method for three dimensional (3D) electromechanical mapping of the heart is presented. The new method is based on utilizing special magnetically locatable catheters connected to a mapping and navigation system. The 3D electromechanical map of the chamber is reconstructed by sampling the location of the catheter tip throughout the cardiac cycle at a plurality of endocardial sites together with their local electrograms. The ability to spatially combine electrical and mechanical information may provide a useful tool for both research and clinical cardiology.

Animals↗
PubMed1996

Effect of myocardial swelling on residual strain in the left ventricle of the rat.

Left ventricular (LV) residual strain in the unloaded state was shown previously to affect LV performance. The interrelationship between myocardial swelling and LV residual strain was studied, both experimentally and theoretically. Myocardial swelling was induced by retrograde perfusion of beating, nonworking, isolated rat hearts with perfusate of graded osmolarities (200-420 mosM). The opening angle (an index of residual strain), in radially cut equatorial cross-sectional slices, and their water content were measured in 40 arrested rat LV. Both water content and opening angle decreased significantly with osmolarity from 84.2 +/- 0.45% and 77.2 +/- 9.2 degrees at 200 mosM to 76.5 +/- 1.05% and 36.3 +/- 9.8 degrees at 420 mosM (P < 0.001, respectively). A morphologically based theoretical model was developed and yielded as swelling residual strain relationship, which agrees well with the data. Our results indicate that myocardial swelling is strongly related to LV residual strain, suggesting that swelling, through its effect on residual strain, can affect both LV function and its adaptation to varying loading conditions.

Animals↗
PubMed1995

Altered heart rate variability in panic disorder patients.

Resting electrocardiographic recordings were obtained from 10 patients with panic disorder (PD) and 14 normal controls. Signal analysis of the beat-to-beat heart rate variability was performed by means of power spectrum analysis. The analysis revealed that patients with PD had marked reduction in the high-frequency peaks of the power spectrum densities. An Energy Ratio Index (ERI), which accurately differentiated between patients and controls, was calculated. In PD patients, a significant correlation was demonstrated between the clinical ratings and the energy ratios. Our findings suggest that decreased heart rate variability may be a characteristic of PD. The importance of this finding as a diagnostic marker and the underlying pathophysiological mechanisms need to be further explored.

Adult↗
PubMed1995

Epinephrine dose-response of the isolated working heart in O2-exposed rats.

BACKGROUND: Heart energy efficiency, which is affected by catecholamines, has previously been shown to decline in rats with prolonged normobaric O2 exposure. HYPOTHESIS: Oxygen exposure affects dose response of the heart to catecholamines. METHODS: Epinephrine dose-response (10(-10) - 5 x 10(-6) mol.L-1) was measured in the isolated working heart excised from control rats breathing air, and rats exposed to normobaric 100% oxygen for either 24 h or 49 h. The variables measured were input (oxygen consumption (VO2) and output power, cardiac contractility (Emax and maximal dP/dT), coronary resistance, heart frequency (fH) and left ventricular pressure. Variable (Y*) dose response to epinephrine concentration (C) was fitted to the equation: Y* = Ymax/(1 + (C/C50)n), Ymax--maximal Y*, C50--C for half Ymax and n--an empirical power. RESULTS: Oxygen exposure of the intact rat had little influence on baseline cardiac variables, but did affect sensitivity to catecholamines. A general effect of the O2 exposure was a left shift of the dose-response curve for example, C50 was reduced by 72, 41 and 43 x 10-8 mol.L-1 for VO2, fH and Emax, respectively, after the 24 h exposure. CONCLUSIONS: There was a pronounced change in the dose-response in hearts from 24 h O2-exposed rats, a change partially reversed in hearts from 49 h O2-exposed rats. The high dose, which had a stimulatory effect on hearts from control rats, failed to stimulate hearts from hyperoxic rats.

Adrenergic alpha-Agonists↗
PubMed1993

Impulse propagation in the Purkinje system and myocardium of intact dogs.

To characterize Purkinje activation (PA) patterns, we studied 15 alpha-chloralose-anesthetized dogs. During left ventricular basal or apical pacing, PA was mapped with a row of four to eight multipolar electrodes placed in the left ventricular wall to record Purkinje and muscle potentials. PA times increased linearly with distance from the pacing site (r = 0.8, slope 1.8 +/- 0.15 mm/ms, P < 0.05). With a single premature stimulus (S2) delivered from the apical or basal site, delay of PA times was first evident at remote sites (> or = 50 mm) with S1-S2 = 185 +/- 5 (SD) ms, while at peripacing sites (< or = 10 mm), delay was first evident when S1-S2 = 176 +/- 6 ms (Purkinje relative refractory period; P < 0.05). With S2,...S5 such that S1-S2 = S2-S3, and so on, an alternating mode of conduction, both temporally and spatially, occurred. The alternation was due to refractoriness and conduction interactions. With short premature intervals, remote coupling intervals were 30 ms less than the premature intervals. Conduction delay in Purkinje fibers with premature stimuli allowed remote epicardium to be activated by alternate routes. Conduction of constant-rate stimuli in the Purkinje system is relatively uniform. With single premature stimuli, conduction is delayed first remotely from the pacing site, whether apical or basal stimulation was employed. When S1-S2 is less than Purkinje relative refractory period, the usual endocardial-to-epicardial activation sequence is altered. Multiple premature stimuli cause remote coupling intervals to alternate.

Animals↗
PubMed1993

Ro 5-4864 and PK 11195, but not diazepam, depress cardiac function in an isolated working rat heart model.

The present study was designed to investigate the effects of diazepam, a benzodiazepine (BZ) with high affinity to central BZ receptors and moderate affinity to mitochondrial BZ receptors, and of Ro 5-4864 and PK 11195, ligands specific for mitochondrial BZ receptors, on cardiac function in the isolated working rat heart model. Five concentrations of these drugs (10(-9)-10(-5) mol/l) were used, and the chronotropic (heart rate) and inotropic [maximum elastance of the left ventricle at end systole (Emax), maximal first derivative of left ventricular (LV) pressure (dP/dtmax), LV pressure at dP/dtmax (pressure at dP/dtmax), aortic flow, stroke work, and total pressure-volume area] cardiac parameters were measured. Diazepam, Ro 5-4864, and PK 11195 showed no significant chronotropic activity up to 10(-5) mol/l. Diazepam did not alter the inotropic properties of the heart. Ro 5-4864 at 10(-5) mol/l significantly decreased the indices of contractility, namely, Emax, dP/dtmax, and pressure at dP/dtmax. Aortic flow, stroke work, and total pressure-volume area were significantly depressed at the same concentration. The negative inotropism of PK 11195 appeared to be identical, by most indices, to that of Ro 5-4864, both qualitatively (same pattern) and quantitatively (similar maximal variations); however, for some indices a depressant effect was also found at 10(-7) mol/l. These results show that at high concentrations Ro 5-4864 and PK 11195, but not diazepam, have a depressant effect on mechanical function.

Animals↗
PubMed1992

Beat-to-beat morphologic variability of the electrocardiogram for the evaluation of chest pain in the emergency room.

The value of electrocardiographic, morphologic variability in the early diagnosis of acute myocardial infarction (AMI) and myocardial ischemia was evaluated in 49 nonselected patients presenting to the emergency room with chest pain. High-resolution electrocardiography was used to determine the morphologic variability of consecutive electrocardiographic complexes, and the ratio of the variance of the QRS onset to that of the entire electrocardiogram was calculated. A final diagnosis of AMI was confirmed in 8 patients, acute coronary insufficiency in 8, angina pectoris in 19, and a noncardiac origin for chest pain in 14. Patients with AMI had a significantly higher beat-to-beat electrocardiographic morphologic variability of the QRS onset (1.4 +/- 0.2) than did those with acute coronary insufficiency (1.1 +/- 0.2), angina pectoris (0.9 +/- 0.1) or noncardiac chest pain (0.8 +/- 0.1) (p < 0.05). The sensitivity of the clinical presentation, typical electrocardiographic changes and creatine phosphokinase levels for the diagnosis of an acute ischemic event on admission to the emergency room was 62, 25 and 37.5%, respectively. Relative variance of the QRS onset of > 0.86 had a sensitivity of 75% and a specificity of 61% for diagnosing an acute ischemic event. Logistic regression of these variables showed that the QRS onset relative variability is an independent predictor for an acute ischemic event. It is concluded that an increased beat-to-beat electrocardiographic variability in patients with AMI is present on admission to the emergency room and may assist in establishing the diagnosis in this setting.

Adult↗
PubMed1992

Prediction of immediate ventricular arrhythmias after coronary artery ligation.

OBJECTIVES: Our aim was to test the hypothesis that increased beat to beat morphologic variations in the body surface electrocardiogram (ECG) are associated with fragmented diastolic electrical activity that appears after coronary artery ligation and to correlate the appearance of spontaneous ventricular fibrillation after coronary ligation with the magnitude of the ECG beat to beat variability. BACKGROUND: Unstable and variably delayed electrical activation precedes the development of ventricular fibrillation in dogs with acute ischemia. Detection of these highly variable low amplitude signals from the body surface is currently impossible. We have developed a system designed to measure the degree of beat to beat variability of the ECG. METHODS: With high fidelity electrocardiography, subtle beat to beat ECG morphologic variations were detected in epicardial and body surface electrograms and quantified as the variance of the ECG voltage at specific points of the cardiac cycle. The ratio of the variance at the QRS offset to that of the QRS onset (beat to beat variability index) was then calculated. RESULTS: Ventricular fibrillation developed in 12 of 27 dogs after left anterior descending coronary artery ligation. In 7 of the 12 dogs it occurred immediately (< 15 min) after ligation; in the other 5 it developed late (> 15 min) after ligation. Dogs with subsequently immediate ventricular fibrillation had a significantly higher beat to beat variability index than that of dogs with late or no ventricular fibrillation both before coronary ligation (4.7 +/- 1.4 vs. 1.1 +/- 0.2 and 0.8 +/- 0.1, respectively, p < 0.001) and after ligation (6.4 +/- 2.6, 1.0 +/- 0.6 and 1.2 +/- 0.6, respectively, p < 0.001). In dogs that developed ventricular fibrillation immediately after coronary ligation, the arrhythmia was preceded by fragmented diastolic electrical activity on the epicardial electrogram and a simultaneous increase in the beat to beat morphologic variability of the terminal portion of the body surface ECG QRS complex. CONCLUSIONS: Beat to beat QRS offset morphologic variations appear to be increased before and further increased after coronary artery ligation in dogs that develop ventricular fibrillation immediately after ligation. Increased beat to beat variability index may be associated with the presence of electrophysiologic instability and can predict early ventricular fibrillation.

Analysis of Variance↗