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David Krum

Publications and source records attributed to David Krum.

14 recordsLinked to original sources
PubMed2005

Catheter location, tracking, cardiac chamber geometry creation, and ablation using cutaneous patches.

OBJECTIVE: The ability to construct a three-dimensional (3-D) surface model of the endocardium and track the location of catheters within a cardiac chamber, using only cutaneous patches, would be a useful advancement in treating arrhythmias. We tested the feasibility of such a system, Ensite NavX (Endocardial Solutions, Inc., St. Paul, MN, USA), in patients undergoing catheter ablation for SVTs. METHODS: Sixteen patients with 20 arrhythmias undergoing ablation were selected. Skin electrode patches were placed on the chest to create a 3-D coordinate system. A low-amplitude, 5.7 kHz signal emitted from the patches was received by conventional catheters positioned in the heart. Catheter location was determined by measuring the field strength received by the catheters. Location points were successively acquired while catheters were moved throughout the chamber. This information was collected and processed by a workstation to create a detailed 3-D model of the endocardial surface. Anatomic landmarks were labeled on the model as the mapping catheter was navigated. 3-D cardiac chamber geometry reconstruction, landmark labeling, and real time catheter tracking were performed successfully in all patients. Up to six catheters, with a total of up to 26 intracardiac electrodes, were tracked simultaneously. RESULTS: Constructed geometries, including major vessels and valves, correlated closely with traditional anatomic models as well as intracardiac recordings and fluoroscopic images. CONCLUSIONS: Real-time catheter tracking and 3-D cardiac chamber model construction is feasible using cutaneous patches and conventional catheters. This approach may be useful in the treatment of patients with cardiac arrhythmias where ablation therapy is primarily anatomically based.

Adult↗
PubMed2005

Feasibility and validation of registration of three-dimensional left atrial models derived from computed tomography with a noncontact cardiac mapping system.

OBJECTIVES: The purpose of this study was to determine the feasibility and assess the validity of registering three-dimensional (3D) models from computed tomographic (CT) images using a cardiac mapping system. BACKGROUND: Registration of 3D anatomic models with an interventional system could help identify and navigate mapping and ablation catheters over a complex structure such as the left atrium (LA). METHODS: ECG-gated, contrast-enhanced cardiac CT imaging was performed in 14 patients with atrial fibrillation. Segmentation was used to create 3D models of the LA. The 3D models were registered with the mapping system using a series of fiducial points. Registration was accomplished retrospectively in the first 10 patients, and catheter navigation was visualized from recorded data. In the final four patients, registration was accomplished in real time during electrophysiologic study. The mapping catheter position, as it was navigated inside the LA, was applied to the registered model in real time. For the validation study, temporary pacing leads were implanted in the LA of 10 dogs. Following this, CT scanning, segmentation, LA model importation, and registration was described previously. After registration, a mapping catheter was positioned at the site of each buried lead according to the registered model with no fluoroscopic guidance. A radiofrequency lesion was created at this location, and the dog was sacrificed, the heart removed and stained, and the distance between the buried lead and the lesion measured. RESULTS: During the feasibility study, the location of the catheter in the registered model correlated with fluoroscopy, angiography, and intracardiac electrograms. LA endocardial potentials during sinus rhythm and any premature atrial contractions also were successfully delineated over the registered models. In the validation study, the mean target registration error was 2.0 +/- 3.6 mm. CONCLUSIONS: Registration of CT-derived 3D models of the LA using a cardiac mapping system is feasible and accurate.

Animals↗
PubMed2002

Validation of a left atrial lesion pattern for intraoperative ablation of atrial fibrillation.

BACKGROUND: Evidence that atrial fibrillation may begin in early stages from triggers or reentry circuits primarily in the left atrium suggests that the entire Maze 3 lesion pattern may be unnecessary. In the present study we describe a new left atrial lesion pattern for intraoperative linear ablation of chronic atrial fibrillation. METHODS: Endocardial radiofrequency ablation was performed on 12 dogs with chronic atrial fibrillation. Lesions to isolate pulmonary veins in pairs, the left atrial appendage, and connecting lesions between these structures were administered in a randomized approach. RESULTS: Twelve dogs were in chronic atrial fibrillation for 31 +/- 21 days before ablation. Atrial fibrillation was successfully ablated and rendered noninducible in all 12 dogs. All treatment failures observed with less than the full lesion pattern became a success when the remaining lesions were given. CONCLUSIONS: Atrial fibrillation ablation using this left atrial lesion pattern is highly successful in this model. This approach may have significant utility as a concomitant procedure for patients with atrial fibrillation undergoing mitral valve procedures.

Animals↗
PubMed2002

Radiofrequency ablation of atrial fibrillation during mitral valve surgery.

Twenty-three patients underwent endocardial radiofrequency ablation of atrial fibrillation (AF) during mitral valve procedures with a previously described left atrial lesion pattern. A temperature-controlled 7-coil surgical probe delivered 60-second lesions at 80 degrees C. The left atrial appendage was oversewn after ablation. Ages ranged from 28 to 88 years. Nineteen patients had chronic AF that was present for over 1 year in 74%; 12 patients had rheumatic mitral stenosis. Mean left atrial diameter was 5.4 +/- 0.7 cm. There was 1 operative death unrelated to the ablation, and no strokes or ablation-related complications were observed. At mean follow-up of 32.5 weeks, 86% of the 22 survivors were in sinus rhythm. All 18 patients with left atrial diameter <6 cm are in sinus rhythm. All postoperative atrial flutter was transient, and no patients required subsequent transcatheter ablation. This lesion pattern is safe and effective when applied in the method described here. It appears to be a reasonable alternative to the complete Maze 3 lesion pattern in patients with mitral valve disease.

Adult↗
PubMed2002

Pathologic and histologic results of electrical impulses in a rabbit model of atherosclerosis: 24-hour versus 8-hour regimen.

OBJECTIVE: Low frequency electrical impulses (EIs) reduce new atherosclerotic plaque formation in previously diseased arteries and may reverse the extent of previous pathologic damage in these structures. METHODS: A pacemaker was implanted on the left side of rabbit abdominal aortas, and an electrode was placed close to the other side of the aorta in the psoas major muscle. For the induction of atherosclerosis, the rabbits were placed on a high cholesterol diet (HCD) for 11 weeks. No EIs were applied to the control series I. In the experimental series, the rabbits were fed an HCD for 3 weeks, after which EIs were applied simultaneously with an HCD for 8 additional weeks (3V, 30 contractions per minute). Experimental series II had 24-hour/day EIs, and series III had 8-hour/day EIs. RESULTS: The closer to the area where the EIs were applied, the more local severity increased (atherosclerosis level and surface area). In the control series, the severity of atherosclerosis in the lower aorta assessed with an arbitrary grading system was 1.75 +/- 0.5 (versus 1.5 +/- 0.57 with 8-hour/day EIs and 0.5 +/- 0.3 with 24-hour/day EIs). The involved surface area was 32.5% +/- 9.5% (versus 1.0% +/- 0.8% with 8-hour/day EIs and 0.75% +/- 0.95% with 24-hour/day EIs). CONCLUSION: Both 24-hour/day and 8-hour/day EIs applied close to the abdominal aorta decreased the severity of atherosclerosis in rabbits placed on a HCD, but 24-hour/day EIs decreased the severity more extensively.

Animals↗
PubMedDate not supplied

Slowed progression or elimination of atherosclerosis by low-frequency electrical impulses.

BACKGROUND: In our previous investigations we showed that electrical impulses (EI) can prevent the development of atherosclerosis if they began simultaneously with high cholesterol diet (HCD) or in the early stages of atherosclerosis (after three weeks of HCD only). In this investigation we demonstrated the slow progression or elimination of atherosclerosis by low-frequency EI in case of moderate atherosclerosis (after eight weeks of HCD). METHODS: Series I rabbits (control group) were fed HCD for eight weeks. Series II rabbits were fed HCD for eight weeks and were then switched to normal diet for eight weeks (no EI). Series III rabbits were fed HCD for eight weeks and then switched to a normal diet with simultaneous EI (applied near the abdominal aorta) for eight weeks (3 V, 30 single impulses per minute, 24 hours/day). After euthanization, the level of atherosclerosis, percentage of surface area involved in the atherosclerosis process, and an atherosclerosis score were calculated in the aortic arch, thoracic and abdominal aorta. RESULTS: Statistically significant differences were seen in the level of atherosclerosis in the abdominal aorta between series III animals (0.4 +/- 0.2) and the other two groups: 1.5 +/- 0.4 in series I (HCD only), 1.2 +/- 0.3 in series II (HCD then normal diet). Gross examination of the surface also revealed statistically significant differences (p < 0.05) in the percentage of atherosclerosis between the control series I (30.1 +/- 4.1%) and series II (21.3 +/- 3.6%), compared with series III (5.5 +/- 5.4%). In addition, the atherosclerosis score was also significantly different: 45.8 +/- 3.9 in series I, 25.2 +/- 6.9 in series II, and 2.2 +/- 2.0 in series III (p < 0.05). CONCLUSION: Our study showed that, when applied near the abdominal aorta, low-frequency electrical impulses decrease atherosclerotic deposition in the abdominal aorta.

Animals↗
PubMedDate not supplied

Electrical stimulation promotes angiogenesis in a rabbit hind-limb ischemia model.

In previous investigations, it was shown that applying a modest regimen of electrical stimulation (ES), even in severely ischemic tissue, improves the healing process, accelerates neovascularization, and enhances angiogenesis in muscle tissue. Our objective in this current report was to further understand ES as a potential alternative treatment for severe muscle ischemia. Immediately after the left distal external iliac artery and the femoral artery were excised, ES (30 contractions per minute [cpm], 2 V, single impulses per burst) was applied to rabbit adductor muscle near the site of the excised femoralis artery for 24 hours daily over 1 month. Three other series served as controls: ES without arterial excision; arterial excision without ES or lead implantation; and arterial excision with lead implantation but no ES. Histologic study of capillary density was performed by angiography (employing a grid template) and by measuring the lower limb-calf blood pressure ratio. At the end of 30 days in the ES series, 10.5 +/-1.2 contrast-medium opacified arteries (COAs) crossed a specific grid section segment compared with 7.2 +/-1.5 in the control series without ES (p<0.05); 68.2 +/-9.3 COAs crossed a grid section compared with 43.2 +/-6.4 in controls (p<0.05); 27.3 +/-1.2 grids contained COAs compared with 29.3 +/-3.5 in controls (p<0.05); lower limb-calf blood pressure ratio was 0.81 +/-0.06 compared with 0.31 +/-0.07 in controls (p<0.05); and capillary density was 283.7 +/-24.5 mm2 compared with 91.4 +/-20.9 mm2 in controls (p<0.001). These preliminary results show that cautious ES enhances and accelerates muscle revascularization in severely ischemic tissue.

Animals↗
PubMedDate not supplied

Effect of electrical stimulation on arteriogenesis and angiogenesis after bilateral femoral artery excision in the rabbit hind-limb ischemia model.

The effects of electrical stimulation (ES) on arteriogenesis (the opening of preexisting collaterals) and angiogenesis (formation of new capillaries) were studied after acute bilateral hind limb ischemia was induced via bilateral femoral artery excision in a rabbit model. The study evaluated the rabbit hind limbs' normal response to acute ischemia and to application of ES by calculating changes in arterial and capillary densities. Comparisons were made with our prior study, in which the femoral artery was unilaterally excised, as we attempted to expand on the topics of arteriogenesis and angiogenesis. Twelve adult New Zealand white rabbits were randomly assigned to 1 of 2 series. In Series 1, the control group, both femoral arteries were excised and no ES was applied. In Series 2, both femoral arteries were excised and ES was applied to the left limb. One lead was implanted into the left adductor muscle near the site of the excised left femoral artery (Series 2), and a stimulator (Thera, Medtronic, Inc, Minneapolis, MN) was implanted in a separate pocket. ES was applied at a rate of 3 V, 30 contractions per minute, beginning immediately after surgery and continuously for 1 month. Angiography was performed in all 12 rabbits 1 month after surgery to establish the anatomy of the collateral vessels and to demonstrate that the femoral artery stump continued to be an end artery. Contrast-opacified arteries (COAs) that crossed the grid's midline, and the total number of grid lines intersected by COAs, were tallied according to an established method. Capillary density was calculated as the number of capillaries per square millimeter of muscle. In Series 1, after 1 month, the number of COAs crossing the grid's midline was 4.5 +/-1.5 on the left and 4.8 +/-1.2 on the right side. In Series 2, the number of COAs crossing the grid's midline was 7.9 +/-1.8 on the left side (p<0.05 vs Series 1) and 5.9 +/-1.6 on the right side of the same rabbit (p=NS vs Series 1). In Series 1, 36.7 +/-5.4 and 30.5 +/-7.7 total intersections were crossed by COAs on the left and right sides, respectively. In Series 2, total grid intersections crossed by COAs were 48.4 +/-8.5 and 47.5 +/-9.1 in the left and right sides, respectively (p<0.001 vs series 1). Baseline capillary density before femoral artery excision was 180.2 +/-21.3/mm(2). The capillary densities on the left sides were 94.2 +/-19.1 and 264.5 +/-7.6 in Series 1 and 2, respectively (p<0.001). The right sides showed a similar pattern with capillary densities of 88.5 +/-37.2 and 135.8 +/-6.8 (p<0.05) in Series 1 and 2, respectively. When capillary density was compared on the left and right sides of the same rabbit in Series 2, a statistically significant increase was also found; 264.5 +/-7.6 vs 135.8 +/-6.8 (p<0.001) in the left and right sides, respectively. Comparisons of the effect of electrical stimulation and the body's normal physiologic response to acute ischemia revealed a significant increase in the opening of preexisting collaterals (arteriogenesis) and the promotion of capillary density (angiogenesis) with the use of electrical stimulation.

Angiography↗