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# Design of a Cooling Guide Catheter for Rapid Heart Cooling

[+] Author and Article Information
Thomas L. Merrill

Department of Mechanical Engineering, Rowan University, 201 Mullica Hill Road, Glassboro, NJ 08028; FocalCool, LLC, 107 Gilbreth Parkway, Suite103, Mullica Hill, NJ 08062merrill@rowan.edu

Denise R. Merrill

FocalCool, LLC, 107 Gilbreth Parkway, Suite103, Mullica Hill, NJ 08062deemerrill@focalcool.com

Todd J. Nilsen

FocalCool, LLC, 107 Gilbreth Parkway, Suite103, Mullica Hill, NJ 08062tnilsen@focalcool.com

Jennifer E. Akers

FocalCool, LLC, 107 Gilbreth Parkway, Suite103, Mullica Hill, NJ 08062jdocimo@focalcool.com

J. Med. Devices 4(3), 035001 (Aug 31, 2010) (8 pages) doi:10.1115/1.4002063 History: Received March 08, 2010; Revised June 01, 2010; Published August 31, 2010; Online August 31, 2010

## Abstract

Cardiovascular disease is the leading cause of death in the United States. Despite decades of care path improvements approximately 30% of heart attack victims die within 1 year after their first heart attack. Animal testing has shown that mild hypothermia, reducing tissue temperatures by $2–4°C$, has the potential to save heart tissue that is not adequately perfused with blood. This paper describes the design of a cooling guide catheter that can provide rapid, local cooling to heart tissue during emergency angioplasty. Using standard materials and dimensions found in typical angioplasty guide catheters, a closed-loop cooling guide catheter was developed. Thermal fluid modeling guided the interior geometric design. After careful fabrication and leak testing, a mock circulatory system was used to measure catheter cooling capacity. At blood analog flow rates ranging from 20 ml/min to 70 ml/min, the corresponding cooling capacity varied almost linearly from 20 W to 45 W. Animal testing showed 18 W of cooling delivered by the catheter can reduce heart tissue temperatures rapidly, approximately 3° in 5 min in some locations. Future animal testing work is needed to investigate if this cooling effect can save heart tissue.

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## Figures

Figure 1

CoolGuide™ catheter without outer braiding: (1) inlet coolant lumen, (2) outlet coolant lumen, (3) blood and angioplasty use lumen, and (4) coolant turn around slot at distal tip

Figure 2

CoolGuide™ distal tip inserted into the right coronary artery from a femoral artery insertion, typical for PCI procedures. Blood flows through and around the catheter as it sits in the coronary artery: (a) eccentric design and (b) concentric design.

Figure 3

Sketch of two inner core designs made of Teflon PTFE. The central, large lumen is for blood flow and intervention tools. The smaller lumens are for coolant flow entering and leaving. The tip of the catheter has a coolant turn-around slot. The outer braid is made of stainless steel and Pebax.

Figure 4

CoolGuide™ heat transfer processes, three processes (Q1,Q4, and Q5) exchange heat from the aorta blood to either coolant or internal blood flow and two process (Q2 and Q3) exchange heat from the internal blood flow to coolant flow. The net cooling effect results from Q2 and Q3 exceeding Q5.

Figure 5

CoolGuide™ thermal resistance network. Heat flows from left to right in the network. This network represents how heat flows radially at every point along the length of the catheter. Heat transfer between coolant pathways was neglected.

Figure 6

Predicted performance results for the eccentric and concentric catheter designs. Model predicts that the concentric and eccentric devices will meet the required minimum cooling capacity of 20 W at 10 ml/min and 18 ml/min, respectively.

Figure 7

Schematic of the in vitro test setup, showing CoolGuide™ catheter placement in a glass aorta. Flow is pumped in two circuits: one circuit carries systemic flow through the glass aorta and one circuit carries internal flow through the catheter. The dashed lines near the catheter represent coolant connection lines; these lines are connected to the cooling console.

Figure 8

CoolGuide™ eccentric coolant pressure-flow behavior. The average coolant temperature was approximately 10°C. Large differences were attributed to the nonlinear dependence on hydraulic diameter, PTFE wall deformation during the circulation process, and extrusion process limitations.

Figure 9

CoolGuide™ cooling capacity compared to model prediction. Error bars indicate sample standard deviations for three different catheter prototypes. These prototypes demonstrated the ability to achieve cooling capacity requirements (20 W) at flow rates above 20 ml/min.

Figure 10

Device and temperature probe locations. Temperature probes were placed in three locations labeled 1–3. CoolGuide™ is shown inserted into the LAD.

Figure 11

Typical myocardium temperatures. The temperature readings of three probes during LAD cooling using CoolGuide™ without artery occlusion are shown. A temperature drop of 3°C occurred in about 5 min (probe 3). Cooling is localized, i.e., probe 1 location experiences minimal decrease in temperature.

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