Catheterization and Cardiovascular Diagnosis 22:290-294 (1991)

Influence of Radiographic Contrast Media Viscosity to Flow Through Coronary Angiographic Catheters

Robert Roth, RN, Mustafa Akin, MD, Ubeydullah Deligonul, MD, and Morton J. Kern, MD

To assess the influence of viscosity on flow resistance, 4 clinically available contrast media were injected through 12 angiographic catheters of varying dimensions at 20" and 37" C. Seven cc of contrast was injected at a pressure of 200 PSI at 3cc/sec by Medrad Mark IV power injector. The pressure of injection through the manifold was recorded with an electronic pressure transducer.

The lowest injection pressure at 37°C occurred with Hexabrixa. Differences in contrast media viscosity were apparent with catheters <6 French diameter. There were minimal differences in injection pressures with regard to the coronary curve tip configurations for any of the contrast agents. At 20"C, Isovue@ had lower injection pressures than the other contrast agents. Injection through 5 French catheters demonstrated a >1.5 atmosphere difference, especially between Omnipaque@ and Hexabrixm. The difference in contrast media injection pressure was >2 atmospheres between 8 French guiding and 8 French diagnostic catheters and between 5 French and 6 French diagnostic catheters and <2 atmospheres between 8 French and 6 French diagnostic catheters. Injection pressure differences >1 atmosphere were not observed for catheters of the same French size at body or room temperature contrast injection.

These data indicate that important temperature related viscosity differences between agents are present and confirm that the largest differences in contrast media are most apparent for the smallest diameter catheters. Given equivalent image opacification and hemodynamic and adverse effects, selection of a low viscosity contrast media theoreti- cally provides an advantage during procedures using small diameter catheters or inter- ventional procedures requiring contrast media visualization through reduced channels.

Key words: contrast media, hemodynamics, injection pressure

INTRODUCTION

Recent advances in angiographic contrast media for- mulations have produced improved agents with reduced viscosity. Parallel technical improvements in catheter materials and designs have provided small diameter cor- onary angiographic catheters which often require high flow rates for satisfactory images. The trend toward use of smaller diameter (i.e., 5 and 6 French vs. 7 and 8 French) catheters for routine diagnostic angiography [ 11, as well as for guiding catheters in interventional proce- dures [2] raises the clinical question of viscosity as a factor in selection of radiographic contrast media for use in the catheterization laboratory.

The purpose of this study was to compare 4 clinically available radiographic contrast media, assessing the in- fluence of viscosity on flow resistance in 12 coronary angiographic catheters of varying internal dimensions. The hypothesis tested was that the lower the viscosity, the lower pressure required to inject a fixed volume of contrast media through the same coronary catheter. In addition, a lower injection pressure for the same contrast media would indicate a larger lumen (i.e., reduced flow

resistance) for catheters with the same reported internal diameters. This information would validate manufactur- er's claims with regard to clinical differences of contrast media injection pressures with handheld syringes in ad- dition to reported differences in catheter performance regarding flow rates.

MATERIALS AND METHODS

The 4 contrast media tested were ioxaglate meglumine (Hexabrix@), iopamidol (Isovue@), iohexol (Omni- paqueo) and diatrizoate meglumine (Renografin-76@) (Table I). Twelve catheters were tested, grouped into 8 French diagnostic and guiding catheters, 5 and 6 French

From the Cardiology Division, St. Louis University Hospital, St. Louis, MO.

Received August 6 , 1990; revision accepted November 4, 1990.

Address reprint requests to Morton J . Kern, M.D., Director, Cardiac Catheterization Laboratory, St. Louis University Hospital, 3635 Vista Avenue at Grand, St. Louis, MO 631 10.

0 1991 Wiley-Liss, Inc.

Influence of Viscosity on Flow Resistance 291

diagnostic catheters and 8 French guiding catheters with an angioplasty balloon catheter extended through the end of the catheter (Table 11). A fixed contrast volume ( 7 cc) of each media was injected through the test catheter at 3cc/second using a Medrad Mark IV power injector at a pressure setting of 200 PSI. Contrast media was injected through the back port of a conventional four port coro- nary manifold (Namic) system by means of the Namic high flow connecting tubing to the Medrad injector at room temperature (20°C). These measurements were re- peated on a separate day with fresh contrast media pre- warmed in a contrast media heating bath to an average of 37°C (body temperature).

An indeflator pressure transducer (Intelliflator, Merit Medical Systems, Salt Lake City, UT), calibrated with a mercury manometer, was placed in-line between the cor- onary catheter and the coronary manifold using a four- way, high flow stopcock. The stopcock was open to both the catheter and transducer. The analog pressure trans- ducer signal was interfaced directly to a photographic oscilliscope recorder (VR- 12 Electronics for Medicine). Custom software, provided by Merit Medical Systems, also recorded the continuous output of pressure measured by the transducer in atmospheres (atm) and stored this information in digital format. Both the analog signal and digital printout demonstrated identical values for maxi- mal pressure during the power injection. The calibration of the pressure signals was set such that lcm deflection was equal to 2 atm. The pressure curves of the power injection of contrast media through a 6 French catheter using this system are illustrated on Figure 1.

Data Analysis Four injections were performed for each catheter with

each contrast agent. Because of potential artifacts with empty or partially filled catheters, the first injection of each series was excluded. The peak injection pressure of the last 3 of 4 injections was averaged. The peak pressure value was confirmed from both the digital and analog data records. The reproducibility of values was ? 0.2 atm for this system. Values in which a question of va- lidity (e.g., Isovue@ for 6 French catheter series) arose were repeated on another day at both 20°C and 37°C temperature. Catheter dimensions were obtained from the manufacturing package inserts.

RESULTS Body temperature viscosity

The lowest viscosity agent at body temperature (37" C) was HexabrixO for all 12 catheters tested (Fig. 2). Equiv- alent low pressures (0.8 atm) were recorded for 8 French guiding catheters without coronary angioplasty balloon catheters. The 8 French JL4, JR4 and AL2 had >0.5 atm

ATM

1 sec

10

5

0

6F Hexabrix Power Injector 7cc @ 3cclsec

Fig. 1. Pressure tracings for the contrast media pressure transducer system during power injection. The pressure curves of the power injection are highly consistent and reproducible for the upstroke, duration and peak pressure obtained. For this example, Hexabrixa was injected through a 6 French Judkins left 4cm coronary catheter.

Body Temperature 12, I I I I

8 Hexabrix + Omnipaque

ATM

+ lsovue - Renografin

Fig. 2. Body temperature (37" C) contrast media injection through the 12 catheters. Abbreviations as follow: SHI = Shiley; 8F=8 French; JR4=Judkins right 4 cm curve; G=guiding cath- eter; JL4=Judkins left 4cm curve; AL2=Amplatz left 2 cm curve; AR2=Amplatz right 2cm curve; ACX 2.5=ACX angio- plasty catheter 2.5mm balloon; ATM = atmospheres. Note the scale 0-12 ATM (1 ATM = 760mmHg = 14.6 PSI).

difference between HexabrixO and the 3 other agents. Higher pressures (>3.5 atm) were needed for the other 3 contrast agents. The 8 French JR4 guiding catheter filled with an ACS (Advanced Cardiovascular Systems, Palo Alto, CA) angioplasty balloon catheter had peak injec-

292 Roth et al.

TABLE 1. ComDarative Osmolalitv and Viscositv

Contrast media Iodine Osmolality Viscosity Viscosity substance concentration (mOsmikg H,O) at 20" C (CPS) at 37" c (CPS)

Ioxaglate Meglumine 39.3% and 32% (320mgimL) 600 15.7 7.5

lopamidol (IsovueO) 37% (370mgimL) 796 20.9 9.4

Ioxaglate Sodium 19.6% Injection (Hexabrix)"

lohexol (Omnipaque@) 35% (350mgimL) 844 20.4 10.4 Diatrizoate Meglumine Diatrizoate Sodium 37% (370mgimL) 1940 13.Xb 8.4 Injection 76% (Renografin")

"Licensed by Guerbet, S.A. Registered U.S. Patent and Trademark Office. h25"C.

tion pressures similar to the 6 French catheters. The JL4 coronary curve tip configuration was associated with > 1 atm increase in required injection pressure at room tem- perature only for IsovueO.

Room temperature viscosity

Unlike findings at 37" C, at room temperature (20" C) (Fig. 3 ) , IsovueO had a lower viscosity for all catheters up to the 6 French JL4. The injection pressures for 5 French catheters demonstrated a difference of > 1.5 atm between Omnipaque@ and HexabrixO at room tempera- ture.

Individual pressure curves for each contrast agent at 37" and 20" C are shown on Figure 4. The difference in contrast media injection pressure was >2 atm between 8 French guiding and diagnostic catheters, <2 atm be- tween 8 French and 6 French diagnostic catheters and >2 atm between 5 French and 6 French diagnostic catheters. At body temperature, the peak pressure was <0.5 atm

TABLE II. Dimensions of Catheters*

Manufacturer, catheter size Outside diameter Inside diameter and style inches mm inches mm

Shiley 8F JR4G 0.104 2.70 0.079 2.02 Shiley 8F JL4G 0.104 2.70 0.079 2.02 Cordis 8F JL4 0.104 2.70 0.056 1.42 Cordis XF JR4 0.104 2.70 0.056 1.42 Cordis 8F AL2 0.104 2.70 0.056 1.42 Cordis 6F JL4 0.079 2.00 0.051 1.30 Cordis 6F AR2 0.079 2.00 0.051 1.30 Shiley 8F JR4G + ACS 2.5" 0.105 2.70 0.023 0.61 Cordis 6F JR4 0.079 2.00 0.051 1.30 Shiley 8F JL4 + ACS 2.5" 0.104 2.70 0.023 0.61 Sherwood 5F JL4 0.066 1.67 0.046 1.16 Cordis 5F JL4 0.068 1.67 0.044 1.12

ATM

lower for the smallest catheters (Sherwood 5 French and the Cordis 5 French JL4 catheters). Injection pressures differences > 1 .O atm were not observed for catheters of the same French size at body temperature or at room temperature with one exception (6 French JR4 vs. 6 French AR2) with Isovue@. These data points were un- changed after retesting at a second trial with fresh con- trast media.

DISCUSSION

These results confirm the published viscosity values [3] (Table I) for Hexabrix@, IsovueO, OmnipaqueO, and Renografin-76@ (7.5, 9.4, 10.4 and 8.4 at 37" C; and 15.7, 20.9, 20.4 and 13.8 CPS at 2WC, respectively) as one might find in the clinical setting. Important temper- ature related viscosity differences between these agents were also demonstrated, supporting the notion that warmed contrast media is better tolerated by both the

"From manufacturer package inserts. JL4 = Judkins left 4cm curve; JR4 = Judkins right 4cm curve; AL2 = Amplatz left 2cm curve; AR2 = Amplatz right 2cm curve. "Assuming a guiding catheter internal diameter of 2.02mm and outer di- ameter of an ACS (Advanced Cardiovascular Systems, Inc.) 2.5mm cor- onary angioplasty catheter of 1.41mm.

Room Temperature 121 I I I I

Hexabrix Ornnipaque

lsovue Renografin

Fig. 3. Room temperature (20" C) contrast media injection through the 12 catheters. Abbreviations as in Figure 2.

Influence of Viscosity on Flow Resistance 293

Hexa b r ix lsovue

ATM

ATM

+ RoomTemc + BodyTemp

A

ATM

Omnipaque Renografin

+ RoomTemF + BodyTemp

ATM

C

+ RoomTemp + BodyTemp

6

+ RoomTemp + BodyTemp

D

Fig. 4. (A) Hexabrixa, (B) Isovue@, (C) Omnipaque@ and (D) Renografin-76° contrast media at room and body temperature for the 12 catheters tested. Abbreviations as in Figure 2.

patient and the physician performing frequent hand in- jections of contrast through small diameter catheters. These in vitro data also demonstrate that the largest dif- ferences in contrast media are most apparent for catheter sizes smaller than 6 French. The difference in contrast viscosity in the catheterization laboratory translates into clinical importance for consistent reductions in injection pressure required to force contrast media through small catheters. Despite manufacturing claims of the same in- ternal lumen dimensions among catheters of the same French size, small pressure differences can be detected, but are probably of little clinical importance. Significant injection pressure differences (i.e., > 1-2 atm) for cath- eters with different tip configurations were not observed

with warmed contrast media. The catheters with second- ary curves (e.g., JL4, AR2) did show a slightly higher pressure requirement (<O. 5 atm) which was not different with room temperature contrast media. Inserting a com- monly used over-the-wire angioplasty balloon catheter through an 8 French guiding catheter reduces the effec- tive cross-sectional lumen area of the guiding catheter from 3.20 mm2 to 1.64 mm’. The cross-sectional area of the 5 French catheter is 1.06 mm2.

The clinical importance of these data is not readily apparent for most coronary angiographic procedures us- ing large size coronary catheters. However, reducing the difficulty of contrast injection during interventional cath- eterization procedures may be important to improve

294 Roth et al.

visualization in a number of clinical settings such as hyperdynamic flow states (e.g., aortic stenosis, hyper- tension, aortic insufficiency), distal injection during an- gioplasty , visualization of vessels during use of larger diameter interventional equipment, such as atherectomy devices. Procedures using small diameter guiding cath- eters for coronary angiography [2] may also be improved by using the lowest viscosity contrast media.

In addition to viscosity, a number of other factors probably have a greater influence on the quality and safety of coronary angiography . Contrast media related factors include concentration of iodine, ionic composi- tion, osmolality , and adjunctive ingredients [4]. Patient related factors influencing the choice of contrast media and effecting imaging quality include body weight, lung water, positioning of adjacent and superimposed ana- tomic structures, assuming consistent and optimal func- tioning of x-ray generation and imaging recording sys- tems. These additional factors were not evaluated for this in vitro study. Further investigation is in progress to identify the clinical relevance of contrast media viscosity for coronary angiography .

The use of power assisted syringes [5] would obviate clinical differences with respect to hand injection of vis- cous contrast media reported here. Given equivalency of image opacification, hemodynamic, and adverse effects,

selection of a low viscosity media theoretically provides an advantage during procedures using small diameter catheters or interventional procedures requiring contrast visualization through reduced channels.

ACKNOWLEDGMENTS

The authors thank Steve Taylor of Merit Medical Sys- tems and Donna Sander for manuscript preparation.

REFERENCES

1. Kern MJ, Cohen M, Talley JD, Litvack F, Serota H, Aguirre F, Deligonul U, Bashore TM. Early ambulation after 5 French dia- gostic cardiac catheterization: Results of a multicenter trial. J Am Coll Cardiol 15:1475-1583, 1990.

2. Kern MJ, Talley JD, Deligonul U, Serota H, Aguirre F, Gudipati C, Ring M, Joseph A, Yussman ZA, Kulick D, Salinger M. Pre- liminary experience with 5 French diagostic catheters as guiding catheters for coronary angioplasty . Cathet Cardiovasc Didgn (In press, 1990).

3. Fisher H. and Package inserts. Catalog of intravascular contrast media. Radiol 159:561-563, 1986.

4. Rischer HW, Thompson KR. Contrast media in coronary arteriog- raphy: A review. Invest Radiol 13:450, 1978.

5. Krieger RA, Furst AE, Hildner FJ, Midwall J , Kieval J. CO, power-assisted hand-held syringe: Better visualization during dia- gostic and interventional angiography. Cathet Cardiovasc Diagn 19:123-128, 1990.