Article Figures & Data
Figures
- Fig 1.
MARC catheter system. A, Hand-wound copper coil solenoid on an alumina substrate tube. B, Catheter diagram with thermocouple. A. Catheter length. B. Catheter tip. C. Coil feedwire. D. Power lead E. Power phone jack lead AA. Catheter tip. C, Magnetic microcatheter III with thermocouple. A light blue Rapid Transit microcatheter (Cordis, Miami Lakes, Florida) with a 2.3F distal tip has been used as a substrate. A 30-turn copper solenoid coil mounted on an alumina tube is attached to the distal tip of the microcatheter with brown shrink-wrap. A copper-constantan thermocouple terminates adjacent to the coils within the shrink-wrap. Current-carrying copper wires to the solenoid coil run down the catheter lumen and are attached to a phone jack adaptor that, itself, can be plugged into a power source for activation experiments. The dark blue thermocouple plug at the catheter hub can be attached to a data logger for temperature measurements. D, Distal tip of magnetic microcatheter III. A 30-turn copper solenoid coil mounted on an alumina tube is attached to the distal tip of the microcatheter. Brown shrink-wrap attaches the alumina tube–copper coil assembly to the distal tip of the microcatheter. The final outer diameter is approximately 2 mm.
- Fig 2.
Schematic diagram depicting coil-tipped microcatheter heating activation points in vivo (swine right and left common carotid arteries, respectively). The first activation point is 1 cm distal to the origin of the internal carotid artery (ascending pharyngeal artery). Each subsequent activation point is separated by a 1-cm manual pull-back of the catheter, confirmed by imaging. This ensures adequate spacing between points in case of potential thermal damage to the arterial wall at any given point.
- Fig 3.
In vitro heating data for alumina tube construct tested at 300 mA in air, in a 25°C water bath, and in a 37°C water bath.
- Fig 4.
In vivo x-ray, DSA, axial MRA, coronal MRA MIP, and coronal SSFP. Unsubtracted x-ray image (A) demonstrates MARC catheter tip coils (white arrowhead), microcatheter shaft with lead wires (black arrow), and guiding catheter (black arrowhead) in the right CCA. Only the guiding catheter tip marker is readily evident on the equivalent DSA image (B). Susceptibility from the catheter shaft lead wires (black arrow) and catheter tip (white arrowhead) is seen on axial MRA (C and D), coronal MRA MIP (E), and coronal SSFP (F). With a 300-mA current applied (G), the catheter tip coils are more apparent (white arrowhead). Guide catheter tip artifacts resulting from a metallic marker band are very prominent on the SSFP sequence (F and G).
- Fig 5.
Porcine carotid artery wall histologic appearance after use of endovascular catheter tip coils at a 300-mA tip current for 1 minute at normal flow (A-D) or a 600-mA tip current for 2 minutes at zero flow (E and F). There is no evidence of vessel wall damage on hematoxylin-eosin (A and B) or Masson trichrome (C and D) at 300 mA. At 600 mA, however, luminal thrombus (E, black arrowhead), extensive medial vacuolization (F, black arrow), and medial hemorrhage (G, white arrow) all indicate thermal damage to the arterial wall.
- Fig 6.
Plot of applied current vs degree of histologic damage for catheter activation experiments in vivo (n=94) in porcine carotid arteries. A, Normal arterial flow. B, Arterial stasis.
Tables
Experimental Catheter No. Substrate Microcatheter Catheter Length (cm) Solenoid Coil (no. of turns) Resistance (ohms) Thermocouple I 2.3F RapidTransit 170 30 2 None II 2.7F Tracker-18 150 75 5.5 None III 2.3F RapidTransit 170 30 2.5 Copper/constantan type T IV 2.3F RapidTransit 170 30 2.5 Copper/constantan type T - Table 2:
Definite vs no or questionable histologic damage to carotid arteries under various conditions of catheter testing in vivo
Condition Tested Definite Damage (%) No/Questionable Damage (%) Odds Ratio 95% CI P Value* Arterial stasis (n = 24) 4 96 3.0 0.36–137 .44 Normal flow (n = 70) 11 89 Current ≤300 mA (n = 58) 0 100 0 0–0.21 .0001 Current > 300 mA (n = 36) 25 75 Activations ≤1 min (n = 52) 6 94 0.37 0.056–1.9 .29 Activations > 1 min (n = 42) 14 86 Work ≤100 J (n = 68) 3 97 0.082 0.008–0.5 .0015 Work >100 J (n = 26) 27 73 Saline drip ≤2 mL/min (n = 39) 15 85 3.2 0.61–21 .16 Saline drip > 2 mL/min (n = 55) 5 95 ≤5°C catheter tip coil temperature rise (n = 36) 0 100 0 0–0.36 .0022 > 5°C temperature rise (n = 29) 24 76 MR and x-ray guidance (n = 45) 11 88 1.9 0.35–13 .47 X-ray guidance only (n = 49) 6 94 CI indicates confidence interval; J, Joules; mA, milliamperes.
Note:—Definite damage denotes a histologic score of 2; questionable damage, histologic score of 1; and no damage, histologic score of 0.
↵* P value = 2-tailed Fisher exact test.
- Table 3:
Definite or questionable vs no histologic damage to carotid arteries under various conditions of catheter testing in vivo
Condition Tested Definite/Questionable Damage (%) No Damage (%) Odds Ratio 95% CI P Value* Arterial stasis (n = 24) 21 79 0.87 0.25–3.5 .77 Normal flow (n = 57) 23 77 Current ≤300 mA (n = 51) 14 86 0.31 0.092–1.020 .034 Current > 300 mA (n = 36) 31 69 Activations ≤1 minute (n = 52) 8 92 0.17 0.037–0.61 .003 Activations > 1 min (n = 42) 33 67 Work ≤100 J (n = 68) 13 87 0.29 0.018–1 .037 Work > 100 J (n = 26) 35 65 Saline drip ≤2 mL/min (n = 39) 21 79 1.2 0.35–3.7 .80 Saline drip >2 mL/min (n = 55) 18 82 ≤5°C catheter tip coil temperature rise (n = 36) 8 92 0.17 0.028–0.80 .013 > 5°C temperature rise (n = 29) 34 68 MR and x-ray guidance (n = 45) 16 84 0.64 0.19–2.0 .44 X-ray guidance only (n = 49) 22 78 ↵* P value = 2-tailed Fisher exact test.
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