Reducing Radiation Exposure during CRT Implant Procedures: Early Experience with a Sensor-Based Navigation System BERNARD THIBAULT, M.D., JASON G. ANDRADE, M.D., MARC DUBUC, M.D., MARIO TALAJIC, M.D., PETER G. GUERRA, M.D., KATIA DYRDA, M.D., ´ LAURENT MACLE, M.D., LENA RIVARD, M.D., DENIS ROY, M.D., ´ BLANDINE MONDESERT, M.D., and PAUL KHAIRY, M.D., PH.D. From the Electrophysiology Service, Montreal Heart Institute and the Department of Medicine, Universit´e de Montr´eal, Montreal, Canada
Background: Cardiac resynchronization therapy (CRT) implant procedures are often complex and prolonged, resulting in significant ionizing radiation (IR) exposure to the patient and operator. We report our early experience working with a novel sensor-based electromagnetic tracking system (MediGuideTM , MDG, St. Jude Medical Inc., St. Paul, MN, USA), in terms of procedural IR exposure reduction. Methods and Results: Information regarding patient demographics, procedural details, procedural duration, and IR exposure were prospectively collected on 130 consecutive CRT procedures performed between January 2013 and January 2014. Sixty procedures were performed with MDG guidance, and 70 were performed without MDG guidance. Despite a nonsignificant trend toward shorter procedure duration with the use of MDG (120 minutes vs 138 minutes with non-MDG, P = 0.088), a 66% reduction in total IR exposure (median 769 μGray·m2 vs 2,608 μGray·m2 , P < 0.001) was found. This reduction was primarily driven by a >90% reduction in IR dose required to cannulate the coronary sinus (median 80 μGray·m2 vs 922 μGray·m2 , P < 0.001), and to a lesser extent from a reduction in IR dose required for LV lead placement (median 330 μGray·m2 vs 737 μGray·m2 , P = 0.059). In addition, a significant learning curve effect was observed with a significantly shorter procedural duration for the last 15 cases compared to the first 15 cases (median 98 minutes vs 175 minutes, P < 0.001). Conclusion: The nonfluoroscopic MDG positioning system is associated with a dramatic reduction in exposure to IR during CRT implant procedures, with a 90% decrease in the IR dose required to cannulate the coronary sinus. A steep learning curve was quantified. (PACE 2015; 38:63–70) radiation, cardiac resynchronization therapy, fluoroscopy
Financial Support: None. Conflict of Interest: The Montreal Heart Institute participates in many research protocols in the fields of ablation procedures and pacing/resynchronization therapy that are supported by all manufacturers (Biotronik, Boston Scientific, Johnson and Johnson, Medtronic, Sorin, and St. Jude Medical). All the coauthors are involved directly or indirectly with these studies. The present report was conducted independently at the Montreal Heart Institute (MHI) and was not sponsored by St. Jude Medical. Data were not shared with St. Jude Medical prior to publication. Drs. Guerra, Macle, and Thibault are specifically involved in developing MediGuide and serve on its advisory board. The MHI is a training site for this new technology. Address for reprints: Bernard Thibault, M.D., Electrophysiology Service, Montreal Heart Institute and the Department of Medicine, Universit´e de Montr´eal, 5000 Belanger Street, Montreal, Quebec H1T 1C8, Canada. Fax: 514-593-2551; e-mail: [email protected] Received April 14, 2014; accepted September 2, 2014. doi: 10.1111/pace.12522
Introduction Cardiac resynchronization therapy (CRT), when added to standard medical therapy, results in sustained improvements in functional class, quality of life, left ventricular (LV) ejection fraction, exercise capacity, and mortality in appropriately selected patients.1 Nevertheless, CRT implant procedures are often complex and prolonged, resulting in significant ionizing radiation (IR) exposure to the patient and operator despite standard precautionary measures (i.e., low dose-rate and pulse-rate fluoroscopy, collimation, keeping the detector as close as possible to the patient and the x-ray tube as far as possible, and avoidance of steeply angulated projections).2,3 Minimizing IR exposure during CRT implantation is limited by: (1) close proximity of the operator to the IR source, (2) ergonomic constraints for equipment position and access to the operating field, (3) cumbersome external and personal shielding that is often not adaptable to CRT implant procedures, and (4) frequent
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need for left-oblique projections to guide coronary sinus (CS) cannulation and/or LV lead placement. Taken together, these restrictions result in increased IR emission, particularly for prolonged procedures. A recently developed sensor-based electroTM magnetic navigation system (MediGuide ,MDG, St. Jude Medical Inc., St. Paul, MN, USA), which applies three-dimensional (3-D) visualization to previously recorded fluoroscopic images in realtime, carries the potential to reduce IR exposure during electrophysiological (EP) procedures.4,5 We sought to quantify and compare IR exposure during CRT implantation guided by MDG to contemporary procedures performed without MDG guidance.
Methods A prospective two-group single-center cohort study was conducted by enrolling 130 consecutive patients with standard clinical indications for CRT (New York Heart Association [NYHA] functional class 2–4, LV ejection fraction ࣘ35%, and prolonged QRS duration ࣙ120 ms) between January 2013 and January 2014. Patients undergoing generator change or lead revision procedures were excluded. The EP laboratory to which patients were assigned (i.e., with or without MDG guidance) was arbitrarily determined by secretarial staff. Standard practice at our institution is to implant the LV pacing lead using left subclavian access via a transvenous approach, with the CS engaged using a combination of a nondeflectable guiding catheter (starting with a CPS Direct II, St. Jude Medical) and a steerable EP catheter (Livewire, St. Jude Medical). If clinically indicated, a right ventricular pacing or defibrillator lead, with or without a right atrial bipolar pacing lead, was also implanted. Procedures were performed by eight experienced implanters with the assistance of 11 trainees. Most (79/130) procedures were supervised by a single operator (i.e., 26/60 nonMDG and 53/70 MDG-enabled). Procedures were performed in one of two similarly equipped electrophysiology laboratories, with the exception of MDG. Both laboratories had a single Carm under-couch tube intensifier fluoroscopy system (Axiom Artis Zee and Axiom Artis DFC, Siemens Healthcare, Herlangen, Germany) with the tube voltage and current dose optimized for IR reduction. Standard ALARA principles (“as low as reasonably achievable”) were followed, including limiting the fluoroscopy frame rate to 6 images/s, using the anterior-posterior projection view whenever possible, and minimizing cine
64
acquisitioning, the distance between the patient and detector, and the field of view. The MDG system consists of three components: a transmitter generating a 3-D electromagnetic field, an electromagnetic field reference sensor attached to the patient chest, and a miniaturized coil sensor assembled within the EP catheter, guiding sheath and guidewire. The transmitter produces a set of magnetic fields in a range of frequencies between 10 kHz and 15 kHz, with a magnitude of less than 200 μT, and is mounted on the fluoroscopy detector, aligning the 3-D electromagnetic field with the fluoroscopy field. The reference sensor provides information about the spatial relationship between the chest wall and the fluoroscopy detector and allows accurate compensation for respiratory and patient movement. The sensor tip is tracked nonfluoroscopically within the 3-D electromagnetic field and projected onto the prerecorded fluoroscopy cine loops gated to real time electrocardiogram cycle length. In no case was the MDG-enabled subselector used to intubate the targeted vein. Details about the technology, its interface, potential applications, and the technique for CRT implantation have been previously described.5 Information regarding patient demographics, procedural details, total procedural duration (from start of skin preparation to removal of sterile covers), and total IR exposure time (including fluoroscopic-guidance during venous punctures, and placement, repositioning, or removal of all leads), dose area product (DAP; μGray·m2 ), and DAP indexed to body mass index (μGray·m2 /kg/m2 ) were recorded for all patients. A more detailed breakdown of IR exposure throughout the implant procedure was prospectively collected as of July 2013, including IR exposure during the LV lead placement, that is, beginning of CS cannulation attempts to final removal of the guiding sheath, as well as the individual components of (1) CS cannulation, that is, introduction of the guiding sheath to CS cannulation in a manner that allows for CS angiography and/or LV lead placement and (2) LV lead positioning, which includes CS angiography, all attempts to enter CS side branches, guidewire changes, use of stylets or inner guiding sheaths, and recannulation in the event of lead dislodgement (i.e., [total LV lead dose] − [CS cannulation dose]). The study was approved by the local institutional review board. Written informed consent was obtained in all patients. Statistical Analysis Continuous variables are summarized as mean ± standard deviation or median and
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SENSOR-BASED NAVIGATION AND CRT IMPLANTATION
Table I. Patient Demographics
Age (years) Male, N (%) Height (m) Weight (kg) BMI (kg/m2 ) NYHA functional class, N (%) Class 1 or 2 Class 3 Class 4 LV ejection fraction (%) Ischemic cardiomyopathy, N (%) Comorbidities, N (%) Hypertension Diabetes Permanent atrial fibrillation Previous stroke Previous cardiac surgery QRS duration, ms QRS morphology, N (%) Typical left bundle branch block Intraventricular conduction delay Right bundle branch block Paced Laboratory Hemoglobin (g/L) Platelets (×109 /L) International normalized ratio eGFR (mL/min)
Non-MDG (N = 70)
MDG (N = 60)
P Value
64.8 ± 12.8 53 (75.7) 1.71 ± 0.08 82.4 ± 19.1 28.1 ± 5.3
65.0 ± 11.1 45 (75.0) 1.69 ± 0.10 88.6 ± 18.2 30.9 ± 5.6
0.929 0.925 0.440 0.065 0.006 0.172
42 (60.0) 23 (32.9) 5 (7.1) 25.7 ± 7.8 32 (45.7)
35 (58.3) 23 (38.3) 0 (0.0) 25.4 ± 6.5 29 (48.3)
36 (51.4) 20 (28.6) 16 (22.9) 5 (7.1) 22 (31.4) 165.4 ± 23.9
32 (53.3) 26 (43.3) 11 (18.3) 7 (11.7) 16 (26.7) 165.8 ± 23.2
41 (58.6) 12 (17.1) 4 (5.7) 13 (18.6)
44 (73.3) 3 (5.0) 2 (3.3) 11 (18.3)
130 ± 16 188 ± 53 1.5 ± 0.6 68.6 ± 23.1
131 ± 17 193 ± 64 1.3 ± 0.5 69.4 ± 25.2
0.986 0.414 0.828 0.079 0.626 0.374 0.345 0.917 0.123
0.679 0.607 0.167 0.848
BMI = body mass index; eGFR = estimated glomerular filtration rate; LV = left ventricular; MDG = MediGuide; NYHA = New York Heart Association.
interquartile (Q1–Q3) range depending on whether or not they were normally distributed. Categorical variables are presented by frequencies and percentages. For continuous variables, Mann-Whitney U tests for independent samples were used nonnormally distributed variables and Student’s t-tests for normally distributed variables. Pearson χ 2 -tests or Fisher’s exact tests were used for categorical variables. All tests were two-sided and conducted at the 0.05 significance level. Statistical analyses were performed using the SPSS Statistics version 21 (IBM Corp., Armonk, NY, USA). Results A total of 130 patients (age 64.9 ± 12.0 years, 74.4% male) were examined. Sixty procedures were performed with MDG guidance, and 70
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were performed without MDG guidance (22 in the MDG lab and 48 in a similarly equipped EP lab). No patient crossed over from one treatment arm to the other. Baseline characteristics according to whether procedures were performed with or without MDG guidance are summarized in Table I. With the exception of body mass index (BMI), which was greater in the MDG group (30.9 ± 5.6 vs 28.1 ± 5.3, P = 0.006), baseline characteristics were comparable between the two groups. Likewise, indications for CRT, the type of procedure, implant site, number of leads, and LV lead position were similar between groups (Table II). Radiation Exposure As shown in Table III, MDG was associated with a significant decrease in IR exposure duration
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Table II. Non-IR-Related Procedural Characteristics Non-MDG (N = 70)
MDG (N = 60)
57 (81.4) 9 (12.9) 4 (5.7)
50 (83.3) 10 (16.7) 0 (0.0)
46 (65.7) 24 (34.3)
44 (73.3) 16 (26.7)
65 (92.9) 5 (7.1)
52 (86.7) 8 (13.3)
0 (0.0) 5 (7.1) 23 (32.9) 42 (60.0)
1 (1.7%)a 9 (15.0) 14 (23.3) 36 (60.0)
2 (2.9) 19 (27.1) 28 (40.0) 17 (24.3) 4 (5.7) 138.0 (108.7, 160.5)
0 (0.0) 19 (31.7) 21 (35.0) 1 (28.3) 3 (5.0) 120.0 (94.2, 160.8)
Indication for cardiac resynchronization therapy, N (%) Primary prevention Ventricular tachycardia/fibrillation Atrioventricular block Procedure type, N (%) First implant System revision or upgrade Procedure site, N (%) Left infraclavicular Right infraclavicular Number of leads implanted, N (%) 0 1 2 3 LV lead position, N (%) Anterior Antero-lateral Lateral Postero-lateral Failure Procedure duration (minutes) (25th, 75th percentile)
P Value 0.238
0.348
0.241
0.256
0.665
0.088
a Patient was admitted after LV lead dislodgement but a new LV lead could not be implanted due to coronary sinus occlusion. IR = ionizing radiation; other abbreviations as in Table I.
Table III. Radiation-Related Characteristics
Total IR Exposure time (minutes) Exposure dose (µGray·m2 ) Exposure dose/BMI (µGray·m2 /kg/m2 ) IR exposure time during CS cannulation (minutes)a IR exposure during CS cannulation (µGray·m2 )a IR exposure time during LV lead placement (minutes)b IR exposure during LV lead placement (µGray·m2 )b
Non-MDG (N = 70)
MDG (N = 60)
P Value
19.1 (10.2, 25.3) 2608 (1,333, 5,345) 92.2 (48.4, 181.5) 5.7 (3.2, 15.9) 922 (335, 4,321) 5.6 (3.4, 7.4) 737 (333, 2,124)
6.5 (4.3, 10.7) 769 (491, 2,182) 28.2 (15.8, 67.5) 0.4 (0.3, 0.5) 80 (50, 149) 2.6 (1.2, 5.6) 330 (154, 881)
Background: Cardiac resynchronization therapy (CRT) implant procedures are often complex and prolonged, resulting in significant ionizing radiation (IR) exposure to the patient and operator. We report our early experience working with a novel sensor-based electromagnetic tracking system (MediGuideTM , MDG, St. Jude Medical Inc., St. Paul, MN, USA), in terms of procedural IR exposure reduction. Methods and Results: Information regarding patient demographics, procedural details, procedural duration, and IR exposure were prospectively collected on 130 consecutive CRT procedures performed between January 2013 and January 2014. Sixty procedures were performed with MDG guidance, and 70 were performed without MDG guidance. Despite a nonsignificant trend toward shorter procedure duration with the use of MDG (120 minutes vs 138 minutes with non-MDG, P = 0.088), a 66% reduction in total IR exposure (median 769 μGray·m2 vs 2,608 μGray·m2 , P < 0.001) was found. This reduction was primarily driven by a >90% reduction in IR dose required to cannulate the coronary sinus (median 80 μGray·m2 vs 922 μGray·m2 , P < 0.001), and to a lesser extent from a reduction in IR dose required for LV lead placement (median 330 μGray·m2 vs 737 μGray·m2 , P = 0.059). In addition, a significant learning curve effect was observed with a significantly shorter procedural duration for the last 15 cases compared to the first 15 cases (median 98 minutes vs 175 minutes, P < 0.001). Conclusion: The nonfluoroscopic MDG positioning system is associated with a dramatic reduction in exposure to IR during CRT implant procedures, with a 90% decrease in the IR dose required to cannulate the coronary sinus. A steep learning curve was quantified. (PACE 2015; 38:63–70) radiation, cardiac resynchronization therapy, fluoroscopy
Financial Support: None. Conflict of Interest: The Montreal Heart Institute participates in many research protocols in the fields of ablation procedures and pacing/resynchronization therapy that are supported by all manufacturers (Biotronik, Boston Scientific, Johnson and Johnson, Medtronic, Sorin, and St. Jude Medical). All the coauthors are involved directly or indirectly with these studies. The present report was conducted independently at the Montreal Heart Institute (MHI) and was not sponsored by St. Jude Medical. Data were not shared with St. Jude Medical prior to publication. Drs. Guerra, Macle, and Thibault are specifically involved in developing MediGuide and serve on its advisory board. The MHI is a training site for this new technology. Address for reprints: Bernard Thibault, M.D., Electrophysiology Service, Montreal Heart Institute and the Department of Medicine, Universit´e de Montr´eal, 5000 Belanger Street, Montreal, Quebec H1T 1C8, Canada. Fax: 514-593-2551; e-mail: [email protected] Received April 14, 2014; accepted September 2, 2014. doi: 10.1111/pace.12522
Introduction Cardiac resynchronization therapy (CRT), when added to standard medical therapy, results in sustained improvements in functional class, quality of life, left ventricular (LV) ejection fraction, exercise capacity, and mortality in appropriately selected patients.1 Nevertheless, CRT implant procedures are often complex and prolonged, resulting in significant ionizing radiation (IR) exposure to the patient and operator despite standard precautionary measures (i.e., low dose-rate and pulse-rate fluoroscopy, collimation, keeping the detector as close as possible to the patient and the x-ray tube as far as possible, and avoidance of steeply angulated projections).2,3 Minimizing IR exposure during CRT implantation is limited by: (1) close proximity of the operator to the IR source, (2) ergonomic constraints for equipment position and access to the operating field, (3) cumbersome external and personal shielding that is often not adaptable to CRT implant procedures, and (4) frequent
©2014 Wiley Periodicals, Inc. PACE, Vol. 38
January 2015
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THIBAULT, ET AL.
need for left-oblique projections to guide coronary sinus (CS) cannulation and/or LV lead placement. Taken together, these restrictions result in increased IR emission, particularly for prolonged procedures. A recently developed sensor-based electroTM magnetic navigation system (MediGuide ,MDG, St. Jude Medical Inc., St. Paul, MN, USA), which applies three-dimensional (3-D) visualization to previously recorded fluoroscopic images in realtime, carries the potential to reduce IR exposure during electrophysiological (EP) procedures.4,5 We sought to quantify and compare IR exposure during CRT implantation guided by MDG to contemporary procedures performed without MDG guidance.
Methods A prospective two-group single-center cohort study was conducted by enrolling 130 consecutive patients with standard clinical indications for CRT (New York Heart Association [NYHA] functional class 2–4, LV ejection fraction ࣘ35%, and prolonged QRS duration ࣙ120 ms) between January 2013 and January 2014. Patients undergoing generator change or lead revision procedures were excluded. The EP laboratory to which patients were assigned (i.e., with or without MDG guidance) was arbitrarily determined by secretarial staff. Standard practice at our institution is to implant the LV pacing lead using left subclavian access via a transvenous approach, with the CS engaged using a combination of a nondeflectable guiding catheter (starting with a CPS Direct II, St. Jude Medical) and a steerable EP catheter (Livewire, St. Jude Medical). If clinically indicated, a right ventricular pacing or defibrillator lead, with or without a right atrial bipolar pacing lead, was also implanted. Procedures were performed by eight experienced implanters with the assistance of 11 trainees. Most (79/130) procedures were supervised by a single operator (i.e., 26/60 nonMDG and 53/70 MDG-enabled). Procedures were performed in one of two similarly equipped electrophysiology laboratories, with the exception of MDG. Both laboratories had a single Carm under-couch tube intensifier fluoroscopy system (Axiom Artis Zee and Axiom Artis DFC, Siemens Healthcare, Herlangen, Germany) with the tube voltage and current dose optimized for IR reduction. Standard ALARA principles (“as low as reasonably achievable”) were followed, including limiting the fluoroscopy frame rate to 6 images/s, using the anterior-posterior projection view whenever possible, and minimizing cine
64
acquisitioning, the distance between the patient and detector, and the field of view. The MDG system consists of three components: a transmitter generating a 3-D electromagnetic field, an electromagnetic field reference sensor attached to the patient chest, and a miniaturized coil sensor assembled within the EP catheter, guiding sheath and guidewire. The transmitter produces a set of magnetic fields in a range of frequencies between 10 kHz and 15 kHz, with a magnitude of less than 200 μT, and is mounted on the fluoroscopy detector, aligning the 3-D electromagnetic field with the fluoroscopy field. The reference sensor provides information about the spatial relationship between the chest wall and the fluoroscopy detector and allows accurate compensation for respiratory and patient movement. The sensor tip is tracked nonfluoroscopically within the 3-D electromagnetic field and projected onto the prerecorded fluoroscopy cine loops gated to real time electrocardiogram cycle length. In no case was the MDG-enabled subselector used to intubate the targeted vein. Details about the technology, its interface, potential applications, and the technique for CRT implantation have been previously described.5 Information regarding patient demographics, procedural details, total procedural duration (from start of skin preparation to removal of sterile covers), and total IR exposure time (including fluoroscopic-guidance during venous punctures, and placement, repositioning, or removal of all leads), dose area product (DAP; μGray·m2 ), and DAP indexed to body mass index (μGray·m2 /kg/m2 ) were recorded for all patients. A more detailed breakdown of IR exposure throughout the implant procedure was prospectively collected as of July 2013, including IR exposure during the LV lead placement, that is, beginning of CS cannulation attempts to final removal of the guiding sheath, as well as the individual components of (1) CS cannulation, that is, introduction of the guiding sheath to CS cannulation in a manner that allows for CS angiography and/or LV lead placement and (2) LV lead positioning, which includes CS angiography, all attempts to enter CS side branches, guidewire changes, use of stylets or inner guiding sheaths, and recannulation in the event of lead dislodgement (i.e., [total LV lead dose] − [CS cannulation dose]). The study was approved by the local institutional review board. Written informed consent was obtained in all patients. Statistical Analysis Continuous variables are summarized as mean ± standard deviation or median and
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SENSOR-BASED NAVIGATION AND CRT IMPLANTATION
Table I. Patient Demographics
Age (years) Male, N (%) Height (m) Weight (kg) BMI (kg/m2 ) NYHA functional class, N (%) Class 1 or 2 Class 3 Class 4 LV ejection fraction (%) Ischemic cardiomyopathy, N (%) Comorbidities, N (%) Hypertension Diabetes Permanent atrial fibrillation Previous stroke Previous cardiac surgery QRS duration, ms QRS morphology, N (%) Typical left bundle branch block Intraventricular conduction delay Right bundle branch block Paced Laboratory Hemoglobin (g/L) Platelets (×109 /L) International normalized ratio eGFR (mL/min)
Non-MDG (N = 70)
MDG (N = 60)
P Value
64.8 ± 12.8 53 (75.7) 1.71 ± 0.08 82.4 ± 19.1 28.1 ± 5.3
65.0 ± 11.1 45 (75.0) 1.69 ± 0.10 88.6 ± 18.2 30.9 ± 5.6
0.929 0.925 0.440 0.065 0.006 0.172
42 (60.0) 23 (32.9) 5 (7.1) 25.7 ± 7.8 32 (45.7)
35 (58.3) 23 (38.3) 0 (0.0) 25.4 ± 6.5 29 (48.3)
36 (51.4) 20 (28.6) 16 (22.9) 5 (7.1) 22 (31.4) 165.4 ± 23.9
32 (53.3) 26 (43.3) 11 (18.3) 7 (11.7) 16 (26.7) 165.8 ± 23.2
41 (58.6) 12 (17.1) 4 (5.7) 13 (18.6)
44 (73.3) 3 (5.0) 2 (3.3) 11 (18.3)
130 ± 16 188 ± 53 1.5 ± 0.6 68.6 ± 23.1
131 ± 17 193 ± 64 1.3 ± 0.5 69.4 ± 25.2
0.986 0.414 0.828 0.079 0.626 0.374 0.345 0.917 0.123
0.679 0.607 0.167 0.848
BMI = body mass index; eGFR = estimated glomerular filtration rate; LV = left ventricular; MDG = MediGuide; NYHA = New York Heart Association.
interquartile (Q1–Q3) range depending on whether or not they were normally distributed. Categorical variables are presented by frequencies and percentages. For continuous variables, Mann-Whitney U tests for independent samples were used nonnormally distributed variables and Student’s t-tests for normally distributed variables. Pearson χ 2 -tests or Fisher’s exact tests were used for categorical variables. All tests were two-sided and conducted at the 0.05 significance level. Statistical analyses were performed using the SPSS Statistics version 21 (IBM Corp., Armonk, NY, USA). Results A total of 130 patients (age 64.9 ± 12.0 years, 74.4% male) were examined. Sixty procedures were performed with MDG guidance, and 70
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were performed without MDG guidance (22 in the MDG lab and 48 in a similarly equipped EP lab). No patient crossed over from one treatment arm to the other. Baseline characteristics according to whether procedures were performed with or without MDG guidance are summarized in Table I. With the exception of body mass index (BMI), which was greater in the MDG group (30.9 ± 5.6 vs 28.1 ± 5.3, P = 0.006), baseline characteristics were comparable between the two groups. Likewise, indications for CRT, the type of procedure, implant site, number of leads, and LV lead position were similar between groups (Table II). Radiation Exposure As shown in Table III, MDG was associated with a significant decrease in IR exposure duration
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Table II. Non-IR-Related Procedural Characteristics Non-MDG (N = 70)
MDG (N = 60)
57 (81.4) 9 (12.9) 4 (5.7)
50 (83.3) 10 (16.7) 0 (0.0)
46 (65.7) 24 (34.3)
44 (73.3) 16 (26.7)
65 (92.9) 5 (7.1)
52 (86.7) 8 (13.3)
0 (0.0) 5 (7.1) 23 (32.9) 42 (60.0)
1 (1.7%)a 9 (15.0) 14 (23.3) 36 (60.0)
2 (2.9) 19 (27.1) 28 (40.0) 17 (24.3) 4 (5.7) 138.0 (108.7, 160.5)
0 (0.0) 19 (31.7) 21 (35.0) 1 (28.3) 3 (5.0) 120.0 (94.2, 160.8)
Indication for cardiac resynchronization therapy, N (%) Primary prevention Ventricular tachycardia/fibrillation Atrioventricular block Procedure type, N (%) First implant System revision or upgrade Procedure site, N (%) Left infraclavicular Right infraclavicular Number of leads implanted, N (%) 0 1 2 3 LV lead position, N (%) Anterior Antero-lateral Lateral Postero-lateral Failure Procedure duration (minutes) (25th, 75th percentile)
P Value 0.238
0.348
0.241
0.256
0.665
0.088
a Patient was admitted after LV lead dislodgement but a new LV lead could not be implanted due to coronary sinus occlusion. IR = ionizing radiation; other abbreviations as in Table I.
Table III. Radiation-Related Characteristics
Total IR Exposure time (minutes) Exposure dose (µGray·m2 ) Exposure dose/BMI (µGray·m2 /kg/m2 ) IR exposure time during CS cannulation (minutes)a IR exposure during CS cannulation (µGray·m2 )a IR exposure time during LV lead placement (minutes)b IR exposure during LV lead placement (µGray·m2 )b
Non-MDG (N = 70)
MDG (N = 60)
P Value
19.1 (10.2, 25.3) 2608 (1,333, 5,345) 92.2 (48.4, 181.5) 5.7 (3.2, 15.9) 922 (335, 4,321) 5.6 (3.4, 7.4) 737 (333, 2,124)
6.5 (4.3, 10.7) 769 (491, 2,182) 28.2 (15.8, 67.5) 0.4 (0.3, 0.5) 80 (50, 149) 2.6 (1.2, 5.6) 330 (154, 881)
