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Ann Thorac Surg 2001;72:S1083-S1089
© 2001 The Society of Thoracic Surgeons

Supplement: Cardiothoracic techniques and technologies

Three-dimensional electromechanical mapping: imaging in the operating room of the future

Gil Bolotin, MD, PhDa, Tamir Wolf, PhDb, Frederik H. van der Veen, PhDc, Robert Shachner, BSa, Yuval Sazbon, BSb, Daniel Reisfeld, PhDb, Rona Shofti, DVMb, Roberto Lorusso, MD, PhDc, Shlomo Ben-Haim, MD, DSb, Gideon Uretzky, MDa

a Department of Cardiothoracic Surgery, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel
b Department of Biomedical Engineering, Rappaport Institute of Research in the Medical Sciences, Technion-Israel Institute of Technology, Haifa, Israel
c Department of Cardiothoracic Surgery, Academic Hospital Maastricht, Maastricht, The Netherlands

Address reprint requests to Dr Bolotin, The Department of Cardiothoracic Surgery, Tel Aviv Sourasky Medical Center, 6 Weizman St, Tel Aviv, 64239, Israel
e-mail: bolotin{at}netvision.net.il

Presented at the Seventh Annual Cardiothoracic Techniques and Technologies Meeting 2001, New Orleans, LA, Jan 24–27, 2001.


   Abstract
Top
 Footnotes
 Abstract
Introduction
 Material and methods
 Results
 Comment
 Acknowledgments
 References
 
Background. Three-dimensional electromechanical mapping has previously been shown to be a clinically important tool for cardiac imaging and intervention. We hypothesized that this technology may be beneficial as an intraoperative modality for assessing cardiac hemodynamics and viability during cardiac surgery. We report here the use of this technology as an imaging modality for intraoperative cardiac surgery.

Methods. The tip of a locatable catheter connected to an endocardial mapping and navigating system is accurately localized while simultaneously recording local electrical and mechanical functions. Thus the three-dimensional geometry of the beating cardiac chamber is reconstructed in real time. The system was tested on 6 goats that underwent acute dynamic cardiomyoplasty and on 5 dogs that underwent left anterior descending (LAD) coronary artery ligation.

Results. The electromechanical mapping system provided an accurate three-dimensional reconstruction of the beating left ventricle during cardiomyoplasty. After the wrapping procedure, significant end-diastolic area reduction was noted in the base and mid parts of the heart (948 ± 194 mm2 vs 1245 ± 33 mm2, p = 0.021; and 779 ± 200 mm2 vs 1011 ± 80 mm2, p = 0.016). The area of the cross-section of the apex did not change during the operation. Acute infarcted tissue was characterized 3 days after LAD ligation by concomitant deterioration in both electrical and mechanical function.

Conclusions. By providing both a clear view of the anatomical changes that occur during cardiac surgery, and an accurate assessment of tissue viability, electroanatomic mapping may serve as an important adjunct tool for imaging and analysis of the heart during cardiac surgery


   Introduction
Top
 Footnotes
 Abstract
 Introduction
Material and methods
 Results
 Comment
 Acknowledgments
 References
 
Knowledge of patient hemodynamic status and the state of myocardial viability is of importance during cardiac surgery. Therefore, in addition to routine hemodynamic monitoring in the operating theater, several intraoperative imaging modalities have been suggested as tools for real-time intraoperative decision-making. Transesophageal echocardiography (TEE) is considered a routine perioperative test in mitral valve operations, and in some institutes it is used in all open heart surgeries [1–3]. Measuring continuous cardiac output and oxygen saturation in mixed venous blood during cardiac operations have also been suggested for intraoperative monitoring of severely ill patients [4], whereas use of the conductance catheter technique for intraoperative monitoring during selected cardiac operations has been suggested by others [5, 6]. For the evaluation of coronary status and graft patency, several methods are currently used in the operating theater including Doppler flow analysis, thermal coronary angiography, and conventional, intraoperative, coronary angiography [7–9]. However, despite producing important data, none of these methods directly assesses the degree of myocardial tissue viability.

Recently, a nonfluoroscopic three-dimensional (3D) electromechanical mapping system has been introduced for evaluation of left ventricular (LV) function [10–12]. This mapping technique is capable of reconstructing any beating heart chamber, providing a superimposed color-coded map of electrical characteristics (eg, local activation time sequencing, electrogram amplitude values), based on information gathered from sensors at the catheter tip. The electromechanical mapping system has been shown to be highly accurate and reproducible both in vitro and in vivo [11, 12]. It is currently being used for clinical purposes in several cardiologic imaging and intervention procedures, including viability studies (ventricles), and ablation strategies (atria and ventricles) [12–15].

In the study presented here, we hypothesized that implementation of this new technique as an imaging modality during cardiac surgery would supply hemodynamic and electromechanical data essential to the surgeon and the anesthesiologist for the purpose of decision-making in the course of selected cardiac surgery cases. To this end, acute cardiomyoplasty provided the conditions for electromechanical assessment of regional and global LV function, and LAD ligation provided the opportunity to analyze a mapping of the endocardial properties of ischemic myocardial tissue.


   Material and methods
Top
 Footnotes
 Abstract
 Introduction
 Material and methods
Results
 Comment
 Acknowledgments
 References
 
Animal study
The experiments were performed in accordance with the "Guide for the Care and Use of Laboratory Animals" [16].

Regional and global left ventricular function
For the assessment of the electromechanical mapping system’s ability to identify and present regional and global LV function changes in the operating room, 6 goats underwent the wrapping phase of acute cardiomyoplasty. General anesthesia was induced by intravenous sodium thiopental (Penthotal, thiopentone sodium, Abbot S.p.a.) 15 mg/kg, and maintained after endotracheal intubation with 02:NO (1:2) and 1.5% Fluothane. Throughout the experiments, lung ventilation was maintained using a positive pressure respirator (Harvard Apparatus Inc, South Natick, MA). Body temperature was kept constant using a heating mattress. Before surgery, a single dose of 5,000 U of heparin was administered intravenously.

A left-sided midaxillary incision was performed above the latissimus dorsi (LD) muscle and all collateral blood vessels to the distal part of the muscle were coagulated. All attachments of the muscle except the axillary pedicle were disconnected to keep the thoracodorsal artery, vein, and nerve intact. A 5-cm segment of the anterior portion of the second rib including the periosteum was then resected to allow transposition of the LD muscle flap into the thorax. The muscle was inserted into the chest cavity and its tendon cut and sutured to the periosteum of the third rib before closing the thoracic window. The thorax was then opened at the fourth left intercostal space and the pericardium was cut open.

The left LD muscle flap was wrapped in a counterclockwise fashion around both ventricles. The muscle was first positioned around the right ventricle and fixed with interrupted sutures near the atrioventricular groove at the base of the heart. Subsequently, the remaining part of the muscle was wrapped around the LV. The distal portion was sutured to the proximal part of the muscle.

Myocardial ischemia
In the second part of this study, for the assessment of ischemic heart disease, we performed LAD ligation on 5 mongrel dogs weighing 15 to 35 kg. The preoperative values of local shortening and local electrocardiogram obtained in each animal before the ligation procedure served as its own control. Anesthesia, induced using ketamine 10 mg/kg IV and diazepam 1 mg/kg IV, was maintained after intubation using isoflurane 1% and fentanyl 0.25 mg/kg/min IV. Ventilation was kept constant with a veterinary anesthesia ventilator (model 2000, Hallowell EMC, Pittsfield, MA). Left thoracotomy was performed, after which the LAD was ligated distally to the first diagonal branch.

Nonfluoroscopic electromechanical mapping system
The nonfluoroscopic electromechanical mapping system is based on the principle that a metal coil placed in a magnetic field can generate a current. The size of the current is proportional to the strength of the magnetic field, the location of the coil, and the orientation of the coil in the field [10]. The system (NOGA, Biosense-Webster, Tirat Macarmel, Israel) has been described previously in great detail [10–12]. Briefly, ultralow magnetic fields are generated by three external magnetic field emitters, which are located beneath the operating table. Thus, accurate determination of the location and orientation of a passive magnetic location sensor incorporated in the proximal end of the tip of a 7F deflectable-tip electrophysiological catheter (NAVI-STAR, Cordis-Webster, Diamond Bar, CA) is enabled. This information is then used to track the tip of the specially designed mapping catheter within the LV cavity, without the use of fluoroscopy.

Mapping protocol
In the cardiomyoplasty group, electromechanical mapping of the LV was performed before and immediately after the wrapping procedure in the operating room while the animal’s chest was still open. In the ischemic protocol, mapping was performed before ligation of the LAD and 3 days after ligation.

In all experiments, the mapping catheter was introduced either through a femoral or carotid sheath and advanced in a retrograde fashion into the LV. The reference catheter was placed in the right ventricle (cardiomyoplasty) or attached to the animal’s back (ischemia). Mapping was achieved by moving the locatable catheter tip to multiple endocardial sites. The NOGA processing unit used a triangular algorithm to reconstruct the LV anatomy, enabling real-time assessment of LV geometry.

In addition to the electrical data obtained, global and regional mechanical function of the myocardium were assessed using an algorithm that calculated the fractional shortening of endocard regions at end systole. The method of measuring local endocardial shortening (LS) has been described previously [17]. A site has a positive LS ratio if the distance measured decreases during systole (ie, physiologic contraction), whereas a site has a negative ratio when the distance between it and the surrounding points increases during systole (abnormal endocardial wall motion).

For data analysis, a fixed, cylindrical polar reference coordinate system was defined. The center of mass of the reconstructed LV was calculated from the collection of sampled endocardial points. The line connecting the LV apex with the center of mass was defined as its long axis. For hemodynamic analysis in the cardiomyoplasty protocol, three inner cross-sections were plotted on the LV endocardium, at the apex, middle, and base of the heart. The three cross-sections were plotted at 25%, 50%, and 75% of the LV long axis (Fig 1). The area of these three cross-sections was recorded continuously during a normal cardiac cycle.



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  		Fig 1. The three cross-sections, plotted at 25%, 50%, and 75% of the left ventricle’s long axis. The area of these cross-sections was recorded continuously throughout a normal cardiac cycle.

 
For analysis of electromechanical data obtained throughout the ischemic protocol, the long axis was divided into three parts (apex, midventricle, and base, at 10%, 40%, and 50% of the length of the long axis), and the longitudinal location of each endocardial site was determined based on its projection on the axis. Both the midventricle and base were further divided into six different circumferential regions: anterior, anteroseptal, inferior, inferoseptal, posterior, and lateral. In total, the endocardial surface was divided into 13 different regions, from which the average unipolar electrogram amplitudes and LS values were derived.

Statistical analysis
In the cardiomyoplasty protocol, paired Student’s t test was used to compare the prewrapping (base line) and postwrapping maps and evaluate the geometrical and hemodynamic effects of wrapping without skeletal muscle stimulation. In the ischemic protocol, the unpaired Student’s t test was used to compare bipolar and LS values in baseline and postligation maps. All results are expressed as mean ± standard deviation. Differences were considered to be significant when p was less than or equal to 0.05.


   Results
Top
 Footnotes
 Abstract
 Introduction
 Material and methods
 Results
Comment
 Acknowledgments
 References
 
Global left ventricular function
The mean number of points acquired in each map was 72 ± 6; total mapping time was 29 ± 5 minutes.

The 3D reconstructions of the beating LV obtained intraoperatively before and after the wrapping procedure during the operation were accurate and revealed major changes in the LV as a result of the wrapping. There were no differences between the superimposed color-coding of the endocardial activation propagation mapped before and after the procedure.

Left ventricular end-diastolic volume reduction was documented by comparing the preoperation base line map with the maps obtained after the wrapping procedure (80.6 ± 11 mL vs 60.9 ± 12 mL, p < 0.05); this was accompanied by a less striking reduction in LV end-systolic volume (44.8 ± 14 mL vs 35.8 ± 7 mL, p = 0.09), and nonsignificant changes in ejection fraction (45.6% ± 12 vs 40% ± 5%, p = 0.3).

Changes resulting from the wrapping procedure were demonstrated in three different areas using cross-sections of the apex, midsection, and base of the heart. We found a significant reduction in the midsection end-diastolic area (1011 ± 80 mm2 before vs 779 ± 200 mm2 after the wrapping, p = 0.016), and at both the base end-diastolic and end-systolic cross-section areas (1245 ± 33 mm2 before vs 948 ± 194 mm2 after the wrapping, p = 0.021; and 754 ± 178 mm2 before vs 538 ± 176 mm2 after the wrapping, p = 0.0014). After the wrapping, there were no significant changes in the cross-section of the apex in either systole or diastole, nor in the midsection of the heart at end-systole. The results demonstrating the cross-area changes in the cardiac cycle before and after the wrapping are presented in Table 1.


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  		Table 1. Cross-Section Areas at the Apex, Midpart, and the Base of the Heart, at Baseline, and Immediately After the Wrapping Procedure

 
Local electromechanical assessment of ischemic tissue
The mean number of points acquired in each map was 102 ± 9; total mapping time was 38 ± 7 minutes. Baseline maps demonstrated normal LV function as assessed from the reconstruction (ejection fraction 61.2% ± 7.5%). Three days after LAD ligation, the global function of the LV was found to be reduced (ejection fraction 45.8% ± 8.1%, p = 0.03). The ischemic regions (specifically apex, midanterior, and midanteroseptal) had already undergone irreversible damage. This was attested to by the pathologic coupling of diminished bipolar electrogram amplitude values and local shortening. In the midanterior region, the bipolar electrogram amplitude was 0.6 ± 0.1 mV as compared with 3.9 ± 1.4 mV at base line (Fig 2A), and local shortening of the same region was -6.4% ± 4.5% compared with 11.7% ± 1.3% at baseline (Fig 2B). Results of the electromechanical analysis performed while mapping are summarized in Table 2. Importantly, the coupling of electrical and mechanical data from maps generated and observed in real time enabled delineation of the infarcted tissue, distinguishing it from the surrounding healthy, noninfarcted regions.




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  		Fig 2. Typical electromechanical maps of infarcted myocardium at 3 days after induction of ischemia. Red indicates regions of abnormal electromechanical activity, whereas blue/purple designates a region in which function remains unhindered. (A) Bipolar electrogram amplitude, with red indicating amplitude <0.7 mV and purple designates amplitude >7 mV. (B) Local shortening, with red indicating abnormally contracting regions with values <4% and purple indicating normal contractile function >12%). Reconstructed maps are shown in a left anterior oblique projection, and the white head indicates the left ventricular base.

 

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  		Table 2. Bipolar Electrogram Amplitude (BEA) and Local Shortening (LS) Values at Baseline and 3 Days After Ligation

 

   Comment
Top
 Footnotes
 Abstract
 Introduction
 Material and methods
 Results
 Comment
Acknowledgments
 References
 
Imaging and monitoring of the heart in the operating room
This study demonstrates the ability of 3D electromechanical mapping to generate real-time information in the operating room. Such data includes global LV function, endocardial activation propagation, and detection of regional myocardial damage (ie, assessment of tissue viability by coupling areas of diminished local electrocardiogram amplitude with those demonstrating diminished local shortening). Although TEE is an important tool for evaluating valve function as well as general left ventricular function, its ability to detect the degree of regional ischemia and distinguish between hibernating, stunned, and infarcted areas is limited [1, 2]. This is due to the fact that this imaging modality depends solely on contractile function. A mapping system that combines regional mechanical and electrical characteristics of the endocardium tissue makes it possible to distinguish among such viability states [13, 17]. Furthermore, TEE is unable to supply information regarding the endocardial activation propagation, the importance of which will be discussed later [3].

The conductance catheter technique, while generating important real-time assessment of hemodynamic function, does not directly assess changes in LV structure and anatomy, nor does it provide information regarding local ischemic damage [5, 6].

We believe that the optimal imaging modality in the operating room should be based on a single technique capable of supplying all of the information necessary for decision making during cardiac surgery. Specifically, such a modality should include aspects that will enable global hemodynamic function assessment as well as information regarding tissue viability, while providing high spatial and temporal resolutions.

Regional and global left ventricular function and endocardial activation propagation
Our results demonstrate the ability of electromechanical mapping to reconstruct highly accurate 3D images of the beating LV. Subsequent rotation of the beating image in 3D space easily allows a precise, detailed view of any region of the endocardium. This may be advantageous, especially during more complicated procedures such as aneurysmectomy, left ventriculectomy, cardiomyoplasty, and complex congenital anomaly corrections.

This study demonstrates anatomical changes in different regions of the LV during and as a result of the cardiomyoplasty procedure that cannot be demonstrated by any other imaging modality in the OR. The interpretation of the specific changes that occurred in each cross-section as a result of the wrapping may be important for deciding how to adjust the tightness of the wrapped skeletal muscle. Furthermore, such assessment may prove beneficial for immediate evaluation and sizing of other procedures such as aneurysmectomy repair or a left ventriculectomy at a stage when correction of the surgical configuration is still possible. For these procedures and others, the ability to monitor the procedure in the operating room with this system and to compare the findings to the patient’s long-term results may supply the surgeon with information for improving future procedures of the same kind.

In addition, the ability to assess local endocardial activation patterns may be important after operations in which LV endocardial tissue is cut, such as left ventriculectomy and acute ventricular septal defect repair.

Another possible application of this technique is during atrial fibrillation operations, with or without mitral valve operation. For this purpose, the mapping catheter is inserted into the left atrium, as previously reported by Gepstein and coworkers [18].

Detection of myocardial ischemia
Previously, electromechanical assessment has been shown to be reliable in detecting and localizing chronically infarcted tissue, using a combination of LS and several other indices including unipolar and bipolar electrogram amplitude [17, 19] and endocardial impedance values [20]. The reduction in "active" electrical components such as electrogram characteristics is attributed to the loss of excitable tissue that occurs in myocardial infarction. Endocardial impedance, a passive electrical property, is reduced after tissue necrosis as a result of the increase in available pathways (ie, extracellular space) through which an electrical current may flow [20].

The results of this study indicate that such an analysis of function is valuable in detecting infarcted tissue as early as 3 days after induction of ischemic injury. An important issue is whether such an assessment can provide information regarding acutely occurring alterations of tissue viability. If so, electromechanical mapping may be of value in the immediate postoperative period in patients undergoing coronary artery bypass grafting surgery.

The endocardium is the most vulnerable layer of the heart. This has been attributed to several factors: (1) The subendocardium receives less flow than any other layer during ischemia, due to poor collateral blood supply [21]. (2) The subendocardium is under greater tension than is the subepicardium (according to "Laplace’s law"), giving rise to a higher myocardial O2 consumption (> 20%) even under physiologic conditions [22]. (3) A greater degree of systolic thickening occurs in the subendocardium, resulting in higher energy requirements [23]. (4) The subendocardial arteries are more susceptible to compression; hence, systolic flow is reduced and the layer depends on diastolic flow [24]. (5) The subendocardium is characterized by consistently lower high-energy phosphate concentrations compared with those of the subepicardium [25]. (6) Subepicardial cells possess a transient outward K+ current (Ito) that shortens the duration of action potential [26]. Such a current is absent in subendocardial cells. (7) Cell depolarization occurring as a consequence of elevated extracellular K+ concentration (specifically as seen during ischemia) depresses excitability to a greater extent in the subendocardium as compared with the subepicardium [27]. The latest works of Wolf and colleagues [28] and Fuchs and associates [29] demonstrate the ability of these imaging techniques to assess myocardial viability based on the combination of local shortening and endocardial electrogram.

Given this rationale for addressing the acute ischemic changes in the endocardium, assessment of the changes that occur immediately after graft placement, along with patency verification, may yield important data as to tissue viability. As the latter is observed in real time, such appraisal may enable the surgeon to perform immediate modifications of the revascularization procedure. This may also be an important tool during off-pump surgery, when the need for immediate assessment of graft quality is particularly important and the option of placing the patient on the heart–lung machine for immediate correction is readily available [9].

Limitations of the electromechanical mapping technique in the operating room
The major limitation of this technology is the time required to generate a complete reconstruction of the chamber in question. As observed in the current study, localization of ischemic damage requires a more detailed map than does assessment of global LV function. Areas that were far from the infarcted zone were tested with fewer samples and, when in proximity to noncontractile regions that were mapped in detail, resulted in false-positive LS reductions (e.g., Base-AS).

The electromechanical mapping technique requires insertion of the mapping catheter into the left ventricle. This is as invasive a procedure as intraoperative angiography, conductance catheter, and Swan-Gantz catheter insertion, but is more intrusive than TEE. Although the mapping technology is not based on fluoroscopic visualization (and thus the problem of radiation in the operation room is avoided), it is time-consuming and may be found to be too long relative to the intensive changes that usually occur during and immediately after cardiac surgery.

Conclusions
The beating LV image generated using electromechanical mapping provides a precise reflection of the actual beating heart in the operating room, enabling more immediate and intuitive understanding by the operating team. The system is capable of generating a wide range of information regarding cardiac function in the operating room, some of which cannot be gathered by any other modality (eg, coupling of electromechanical functions). Because of the invasive nature of this technology, additional confirmation of its clinical advantages to selected groups of patients (eg, patients undergoing aneurysmectomy, left ventriculectomy, off-pump coronary artery surgery) should be sought. There are two major clinical limitations to this technique that need to be addressed: the time required for the mapping protocol, and its reliability in assessing acute ischemia and in distinguishing between ischemic, infarcted, and hibernating areas. Once these are achieved, this technology may prove useful for assessing global and regional cardiac function in the operating room of the future.


   Acknowledgments
Top
 Footnotes
 Abstract
 Introduction
 Material and methods
 Results
 Comment
 Acknowledgments
References
 
This study was supported by Biosense-Webster.


   Footnotes
Top
 Footnotes
Abstract
 Introduction
 Material and methods
 Results
 Comment
 Acknowledgments
 References
 
Drs Reisfeld and Ben-Haim and Mr Sazbon disclose that they have a financial relationship with Biosense-Webster.


   References
Top
 Footnotes
 Abstract
 Introduction
 Material and methods
 Results
 Comment
 Acknowledgments
 References
 

  1. Reichert S.L., Visser C.A., Moulijn A.C., et al. Intraoperative transesophageal color-coded Doppler echocardiography for evaluation of residual regurgitation after mitral valve repair. J Thorac Cardiovasc Surg 1990;100:756-761.[Abstract]
  2. Rosenfeld H.M., Gentles T.L., Wernovsky G., et al. Utility of intraoperative transesophageal echocardiography in the assessment of residual cardiac defects. Pediatr Cardiol 1998;19:346-351.[Medline]
  3. D’Ambra M. Is intraoperative echocardiography a useful monitor in the operating room?. Ann Thorac Surg 1993;56(Suppl 5):S83-S85.
  4. Vedrinne C., Bastien O., De Varax R., et al. Predictive factors for usefulness of fiberoptic pulmonary artery catheter for continuous oxygen saturation in mixed venous blood monitoring in cardiac surgery. Anesth Analg 1997;85:2-10.[Abstract]
  5. Schreuder J.J., Steendijk P., van der Veen F.H., et al. Acute and short-term effects of partial left ventriculectomy in dilated cardiomyopathy: assessment by pressure-volume loops. J Am Coll Cardiol 2000;36:2104-2114.[Abstract/Free Full Text]
  6. Kuroda H., Sakaguchi M., Takano T., et al. Intraoperative monitoring of pressure-volume loops of the left ventricle in pericardectomy for constrictive pericarditis. J Thorac Cardiovasc Surg 1996;112:198-199.[Free Full Text]
  7. Lin J.C., Fisher D.L., Szwerc M.F., Magovern J.A. Evaluation of graft patency during minimally invasive coronary artery bypass grafting with Doppler flow analysis. Ann Thorac Surg 2000;70:1350-1354.[Abstract/Free Full Text]
  8. Van Son J.A., Falk V., Walther T., Diegeler A., Mohr F.W. Thermal coronary angiography for intraoperative testing of coronary patency in congenital heart defects. Ann Thorac Surg 1997;64:1499-1500.[Abstract/Free Full Text]
  9. Lazzara R.R., Kidwell F.E., Griffith R. A new technique for intraoperative graft angiography utilizing the radial artery stump. Heart Surg Forum 2000;3:123-126.[Medline]
  10. Ben-Haim S.A., Osadchy D., Schuster I., Gepstein L., Hayam G., Josephson M.E. Nonfluoroscopic, in vivo navigation and mapping technology. Nat Med 1996;2:1393-1395.[Medline]
  11. Gepstein L., Hayam G., Ben-Haim S.A. A novel method for nonfluoroscopic catheter-based electroanatomical mapping of the heart. In vitro and in vivo accuracy results. Circulation 1997;95:1611-1622.[Abstract/Free Full Text]
  12. Gepstein L., Hayam G., Shpun S., Ben-Haim S.A. Hemodynamic evaluation of the heart with a nonfluoroscopic electroanatomical mapping technique. Circulation 1997;96:3672-3680.[Abstract/Free Full Text]
  13. Kornowski R., Hong M.K., Gepstein L., et al. Preliminary animal and clinical experiences using an electroanatomical endocardial mapping procedure to distinguish infarcted from healthy myocardium. Circulation 1998;98:1116-1124.[Abstract/Free Full Text]
  14. Gepstein L., Evans S.J. Electroanatomical mapping of the heart: basic concepts and implications for the treatment of cardiac arrhythmias. PACE 1998;21:1268-1278.
  15. Nademanee K., Kosar E.M. A nonfluoroscopic catheter-based mapping technique to ablate focal ventricular tachycardia. PACE 1998;21:1442-1447.
  16. National Academy of Sciences. Guide for the care and use of laboratory animals. DHHS publication no NIH 85–23, revised 1985.
  17. Gepstein L., Goldin A., Lessick J., et al. Electromechanical characterization of chronic myocardial infarction in the canine coronary occlusion model. Circulation 1998;98:2055-2064.[Abstract/Free Full Text]
  18. Gepstein L., Hayam G., Shpun S., Cohen D., Ben-Haim S.A. Atrial linear ablations in pigs. Chronic effects on atrial electrophysiology and pathology. Circulation 1999;100:419-426.[Abstract/Free Full Text]
  19. Callans D.J., Ren J.F., Michele J., Marchlinski F.E., Dillon S.M. Electroanatomic left ventricular mapping in the porcine model of healed anterior myocardial infarction. Correlation with intracardiac echocardiography and pathological analysis. Circulation 1999;100:1744-1750.[Abstract/Free Full Text]
  20. Wolf T., Gepstein L., Hayam G., et al. Three dimensional, catheter-based, endocardial impedance mapping: a new approach for myocardial infarction assessment. Am J Physiol Heart Circ Physiol 2001;280:H179-H188.[Abstract/Free Full Text]
  21. Jennings R.B., Murry C.E., Steenbergen C., Jr, Reimer K.A. Development of cell injury in sustained acute ischemia. Circulation 1990;82(Suppl II):II2-II12.
  22. Weiss H.R., Neubauer J.A., Lipp J.A., Sinha A.K. Quantitative determination of regional oxygen consumption in the dog heart. Circ Res 1978;42:394-401.[Abstract/Free Full Text]
  23. Bell J.R., Fox A.C. Pathogenesis of subendocardial ischemia. Am J Med Sci 1974;268:3-13.[Medline]
  24. Chilian W.M. Microvascular pressures and resistances in the left ventricular subepicardium and subendocardium. Circ Res 1991;69:561-570.[Abstract/Free Full Text]
  25. Fukunamki M., Yellon D.M., Kodoh Y., Maxwell M.P., Wyse R.K.H., Hearse D. Spatial and temporal characteristics of the transmural distribution of collateral flow and energy metabolism during regional myocardial ischemia in the dog. Can J Cardiol 1987;3:94-103.[Medline]
  26. Antzelevitch C., Sicouri S., Litovsky S.H., et al. Heterogeneity within the ventricular wall: electrophysiology and pharmacology of epicardial, endocardial and muscle cells. Circ Res 1991;69:1427-1449.[Free Full Text]
  27. Krishnan S.C., Shivkumar K., Garan H., Ruskin J.N. Increased vulnerability of the subendocardium to ischaemic injury: an electrophysiological explanation. Lancet 1995;346:1612-1614.[Medline]
  28. Wolf T., Gepstein L., Dror U., et al. Detailed endocardial mapping accurately predicts the transmural extent of myocardial infarction. J Am Coll Cardiol 2001;37:1590-1597.[Abstract/Free Full Text]
  29. Fuchs S., Hendel R.C., Baim D.S., et al. Comparison of endocardial electromechanical mapping with radionuclide perfusion imaging to assess myocardial viability and severity of myocardial ischemia in angina pectoris. Am J Cardiol 2001;1–87:874-880.




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