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Percutaneous subclavian catheterization of the right heart and pulmonary arteries
Experimental andlaboratory
Percutaneous of the right
reports
subclcwian catheterization heart and pulmonary arteries
Robert E. Guide, M.D.* L. Russell Malinak, M.D.** Faber F. McMullen, M.D.*** David J. Turell, M.D.**** Hugh H. Hanson, M.D.***** Hozlsfon. Tex.
A
rapid, simplified technique for right heart catheterization has been employed with success in this laboratory. It has proved to be especially valuable for use in difficult patients and in patients in whom it is desirable to avoid “cutdowns.” This has been accomplished by the use of a standard 36-inch Bardic 17-gauge radiopaque Intracath passed via percutaneous right or left subclavian venipuncture. Through the use of this technique, excellent pressure tracings and samples of blood were obtained in all areas of the right heart and pulmonary arteries, including the wedge position. Wilsoni-3 has, popularized the use of percutaneous subclavian venipuncture for monitoring central venous pressure and as a means of securing a vein for infusions. The many advantages of this technique and the pertinent physiology are well documented.1-4 For these reasons it has
replaced the “cutdown” in the management of seriously ill patients on ouri services. During the past 2 years, 412 standard 12-inch catheters have been placed in the superior vena cava via the subclavian approach. As demonstrated by pulse contour, the catheter frequently passed into the right ventricle prior to withdrawal to the superior vena cava, where it remained for purposes of monitoring and infusion. This technique is advantageous in the presence of: (1) extreme obesity, (2) shock, and (3) obliteration of veins by previous USe.
During the past year, investigational work has been done5s6 which required repeated heart catheterization in the same individual. It was often difficult to isolate veins for venotomy after the second or third catheterization. Difficulties encountered in passing cardiac catheters through the
These studies were completed at Hermann Hospital, Houston, Texas. Received for publication Nov. 12, 1964. *Chief Resident, Internal Medicine. Currently. Special Fellow in Cardiovascular Disease, Cleveland Clinic. Division of Medicine, Cleveland Clinic, 2020 East 93rd St., Cleveland, Ohio. 44106. **Chief Resident, Obstetrics and Gynecology. Currently with the United States Army in Heidelberg, Germany. **Head, Cardiopulmonary Laboratories. **Instructor, Department of Cardiology. *“**Chief. Department of Cardiology. tR.E.G. and L.R.M.
481
Address:
antecubital using this eterization. Materials
veins may be obviated by technique for cardiac cathand
methods
The equipment used for the procedure is simple and inexpensive: a sterile 36-inch radiopaque Intracath with detached needle, a lo-C.C. syringe with saline, a syringe and needle filled with a local anesthetic, a forceps, and a rotating adaptor for attachment to the pressure transducer via the stopcock manifold. The pertinent anatomy is demonstrated in Fig. 1. Note the relationship of the subclavian vein to the clavicle, subclavian arterv, and brachial plexus. Fig. 2 further depicts the position of the subclavian vein, its proximity to the artery and pleura, and the path taken by the venipuncture needle. The external
landmarks for the procedure (Fig. 3) are a point halfway between the anterior axillary fold and the acromion process and a point in the center of the triangle formed by the two heads of the sternocleidomastoid muscle as it joins the clavicle. The venipuncture needle is advanced along the line which joins these points. is placed in Trendelenburg’s The patient position to elevate the central venous pressure and thereby reduce the likelihood of air embolus. The skin is prepared jvith
Fig. 2. Right sagittal view of thorax at point of entry of the needle into the subclavian vein. Note the simplicity of “walking down” the posterior surface of the clavicle into the subclavian vein. (A more perpendicular approach predisposes to entry into the artery and/or pleura.)
Fig. 1. Illustration of regional anatomy. Note the direct proximity of the subclavian vein to the posterior surface of the superimposed clavicle and consider the presence of only supportive structures (pectoralis major muscle, subclavian muscle, and/or costoclavicular ligament) between the skin and the vein. (From Sobotta-Figge Atlas of Human Anatomy, Vol. III, Part 1, Fig. 46, New York, 1964, Hafner Publishing Company, by permission.)
Fig. 3. Photograph depicting the safe angle of advancement of the needle from the mid point between the anterior axillary fold and the acromion process (W~OUU) to the center of the triangle formed by the two heads of the sternocleidomastoid muscle.
PerclltaneoLls subclavian
catheterization
of right heart
483
I / ‘F
FUSION
BOTTLE
\ \ \ I\ \\ I I
Fig. 4. cubital and the by the (middle superior
Contrast medium injected via the median vein. Note the large valves (Zo~,er left arrows) tortuous course of the distal veins bypassed catheter as it enters the subclavian vein arrow), and the tip of the catheter in the ven3 cava (right arroW).
antiseptic solution,* and the landmarks are noted. Local anesthetic may be injected along the path to be taken by the venipuncture needle, including the periosteum of the clavicle. Through the use of sterile technique, a 2-inch, 14-gauge, thinwalled needle (separated from the standard Intracath set) is attached to a lo-C.C. syringe partially filled with saline. The needle is then inserted inferior to the clavicle, according to the directions previously described. After cutaneous puncture, a small amount of saline is injected to insure continued patency of the needle. The needle is slowly advanced while negative pressure is applied through the syringe. Care is taken to avoid disturbing the external anatomy prior to advancement of the needle so that the motion of the catheter follows a straight line from skin to vein (Fig. 3). In this manner, maneuverability of the catheter is excellent as the tortuous course from the arm to the heart is bypassed (Fig. 4). The needle is “\valked *Betadine burg,
Solulion, \‘a.
Physicians
Products
Co.,
Inc.,
Peters-
i 1 I : : : : I’ I \ \
DRAW BLOOD OR I.V. MEDICATION
Fig. 5. Readily available arrangement for bedside monitoring. Note that a pressure transducer may be attached directly at the top of the 3-way stopcock via a 20-gauge needle for simultaneous recording of pressure and administration of fluid. Depicted is a most adaptable plastic stopcock and tubing. All connections must be taped to avoid obvious possible complications. The Intracath is taped to the subclavicular areas as with Intracaths used in peripheral veins. A hemostatic suture may be placed if the needle puncture causes cutaneous bleeding.
down” the posterior surface of the clavicle while the syringe is kept adjacent to the chest \vall. This aids in avoiding structures subjacent to the subclavian vein. Entry into the subclavian vein is indicated by a sudden free flow of blood. The needle is stabilized with the forceps, the syringe is disengaged, and the sterile 36-inch, 17gauge Intracath is passed through the needle to the desired depth. The needle is withdrawn and the catheter advanced and manipulated in the usual mamler. If the catheter fails to pass smoothly through the needle into the vein, a slight adjustment in the position of the needle may he necessary to assure that it has not inadvertent11 passed from the venous lumen. The cath-
484
Guide, Malinak,
McMullen,
l’urell,
eter should not be withdrawn through the sharp needle, since the tip of the catheter may be easily severed subcutaneously. The procedure has been done both with and without the nylon stylus in place. The Intracath may be attached to a standard infusion set for the administration of fluids or to appropriate adaptors for purposes of monitoring pressure prior to insertion through the needle (Fig. 5). Discussion
This method provides a rapid catheterization technique. Discomfort to the patient is decreased and quality tracings are obtained. Ectopic premature contractions caused by this flexible, lightweight catheter are rare. Because of the size of the vessel, venospasm is not encountered. When more specialized catheters are indicated, they may be inserted using a flexible catheter guide.? Angiograms and postmortem studies have not demonstrated the formation of hematomas or vascular extravasation at the site of venipuncture. Contrast medium was injected via the antecubital vein with a catheter in place (Fig. 4). Note the valves in the basilic vein and the tortuous course of the cephalic vein which are bypassed by this procedure. A repeat injection was made during a strenuous Valsalva maneuver simultaneous with removal of the catheter and further depicted no extravasation even with markedly elevated central venous pressure. Of the 412 patients, 17 have been studied at autopsy. The site of venipuncture was often difficult to demonstrate, and again there were no hematomas. Histologically, phlebitis was not observed. In one patient who had intractable shock and congestive heart failure secondary to myocardial infarction a small 1-by-3-mm. thrombus was noted at the tip of the catheter where it lay in the superior vena cava. No other complications have been noted at autopsy. Among the patients who survived their illnesses, only 4 suffered possible complications from the catheter, despite constant use in several for over 2 months: (1) One patient developed minimal inflammation at the site of skin entry after 2 weeks. This cleared spontaneously with removal of the catheter. (2 and 3) Staphylococcal
Am. Hcnrt I. October, 1965
and Hunson
septicemia occurred in one patient while a catheter was in place. Prior to subclavian venipuncture, a septic course and a postoperative abdominal fistula with abscess formation were present. She responded well to therapy. Pneumococcal septicemia also was observed in one patient who had pneumococcal pneumonia. (4) In a patient with pulmonary metastatic choriocarcinoma the right subclavian artery was entered and the needle immediately withdrawn. The left subclavian vein was then catheterized. Eight hours later, symptoms of a serosanguineous pleural effusion were noted. The effusion was aspirated. Two weeks later a repeat aspiration was undertaken when she again developed an effusion. She responded to methotrexate.* Because of the recurrence it seemsunlikely that the first effusion resulted solely from the arterial puncture. By romparison, considerable morbidity (28 per cent) has been reported in a recent article” describing direct percutaneous catheterization of the pulmonary artery. Our method is far safer and more adaptable than this technique and capable of giving the same information. It is often desirable to obtain mixed venous blood repeatedly~ for laboratory study and to be able to perform catheterization of the pulmonary artery at the bedside in critically ill patients. The advantages inherent in performing any catheterization in the laboratory must be weighed when one is deciding to do a bedside procedure. With the monitoring of the pressure pulse contour as the only guide, the subclavian approach has been used to position the catheter in the pulmonary artery. Infusion at that area, as well as the constant monitoring of pressure and aspiration of blood for laboratory studies, are easily accomplished by way of a three-way stopc0ck.i In many of the patients in whom the 12-inch catheter was used, venous pressure was monitored, intravenous medication was given, and blood was aspirated for laboratory studies without disturbing the patient. The patients appreciated the comfort of only one venipuncture, despite weeks and months of hospitalization. It appears that *Lederle Laboratories, Pearl River, N. Y. tK-SZL--3.way stopcock and extension Laboratories. Glendale, Calif.
tube,
Pharrnaseal
Percutaneous
this approach is far safer and more adaptable than that advocated in the reports previously noted. Summary A simple, rapid, inexpensive method of right heart catheterization using a disposable catheter has been presented. Sacrifice of a vein and scarring is avoided. Radiation of the patient is minimized because of prompt entry into the right ventricle and the ease of manipulation. Strict attention to every detail must be followed to avoid the previously reported complications.1,4 \Ve gratefully acknowledge the assistance of Miss Gloria Heard, Director, Department of Photography, Herman11 Hospital, for her work in the preparation of the movie of this procedure and of the photos in this paper. We further acknowledge the consultation and assistance of the Departments of Art and Photography of the Cleveland Clinic. REFERENCES 1. Wilson, J. N., Grow, J. B., Demong, C. V., Prevedel, A. E., and Owens, J. G.: Central venous pressure in optimal blood volume maintenance, Arch. Surg. 85563, 1962.
subclavian
catheterization
of right heart
48.5
2. Wilson, J. N., and Owens, J. C.: Continuous monitoring of venous pressure in optimal blood volume maintenance, Surg. Forum 12:94, 1961. 3. Wilson, J. N.: The management of acute circulatorv failure, Clin. North America 43:469. 1963: 4. Malinak, L. R., Guide, R. E., and Faris, A. M.: Percutaneous subclavian venipuncture for central venous pressure monitoring: Its aDpli.. cation to obstetric and gynecologk problems, Am. J. Obst. & Gvnec. In Dress. 5. Hanson, H. H.,*Gulde, k. E., Allen, H. C., F. F.: The effect of exoJr., and McMullen, genous thyroid and thyroid analogues on left ventricular work, peripheral resistance, cardiac output. and blood volume in athyreotic patients. Presented at the 9th Annual Meeting, The Society of Nuclear Medicine, Southwestern Chapter, Houston, Texas, March, 1964. 6. McMullen, F. F., Allen, H. C., Jr., Guide, R. E., and Hanson, H. H.: The use of center bore scintillation detection ‘crystal in constant monitoring of isotope tracers in cardiac shunt detector and estimation of cardiac output. Presented at the 9th Annual Meeting, *The Societv of Nuclear Medicine. Southwestern Chapter, Houston, Texas, March, 1964. 7. Seldinger, S. I.: Catheter replacement of the needle in percutaneous arteriography, Acta Radio]. 39:368, 1952. 8. Bryant, L. R. : Direct percutaneous pulmonary artery catheterization, J. Thorncic & Cardiox-as. Surg. 48:54, 1964.
Percutaneous of the right
reports
subclcwian catheterization heart and pulmonary arteries
Robert E. Guide, M.D.* L. Russell Malinak, M.D.** Faber F. McMullen, M.D.*** David J. Turell, M.D.**** Hugh H. Hanson, M.D.***** Hozlsfon. Tex.
A
rapid, simplified technique for right heart catheterization has been employed with success in this laboratory. It has proved to be especially valuable for use in difficult patients and in patients in whom it is desirable to avoid “cutdowns.” This has been accomplished by the use of a standard 36-inch Bardic 17-gauge radiopaque Intracath passed via percutaneous right or left subclavian venipuncture. Through the use of this technique, excellent pressure tracings and samples of blood were obtained in all areas of the right heart and pulmonary arteries, including the wedge position. Wilsoni-3 has, popularized the use of percutaneous subclavian venipuncture for monitoring central venous pressure and as a means of securing a vein for infusions. The many advantages of this technique and the pertinent physiology are well documented.1-4 For these reasons it has
replaced the “cutdown” in the management of seriously ill patients on ouri services. During the past 2 years, 412 standard 12-inch catheters have been placed in the superior vena cava via the subclavian approach. As demonstrated by pulse contour, the catheter frequently passed into the right ventricle prior to withdrawal to the superior vena cava, where it remained for purposes of monitoring and infusion. This technique is advantageous in the presence of: (1) extreme obesity, (2) shock, and (3) obliteration of veins by previous USe.
During the past year, investigational work has been done5s6 which required repeated heart catheterization in the same individual. It was often difficult to isolate veins for venotomy after the second or third catheterization. Difficulties encountered in passing cardiac catheters through the
These studies were completed at Hermann Hospital, Houston, Texas. Received for publication Nov. 12, 1964. *Chief Resident, Internal Medicine. Currently. Special Fellow in Cardiovascular Disease, Cleveland Clinic. Division of Medicine, Cleveland Clinic, 2020 East 93rd St., Cleveland, Ohio. 44106. **Chief Resident, Obstetrics and Gynecology. Currently with the United States Army in Heidelberg, Germany. **Head, Cardiopulmonary Laboratories. **Instructor, Department of Cardiology. *“**Chief. Department of Cardiology. tR.E.G. and L.R.M.
481
Address:
antecubital using this eterization. Materials
veins may be obviated by technique for cardiac cathand
methods
The equipment used for the procedure is simple and inexpensive: a sterile 36-inch radiopaque Intracath with detached needle, a lo-C.C. syringe with saline, a syringe and needle filled with a local anesthetic, a forceps, and a rotating adaptor for attachment to the pressure transducer via the stopcock manifold. The pertinent anatomy is demonstrated in Fig. 1. Note the relationship of the subclavian vein to the clavicle, subclavian arterv, and brachial plexus. Fig. 2 further depicts the position of the subclavian vein, its proximity to the artery and pleura, and the path taken by the venipuncture needle. The external
landmarks for the procedure (Fig. 3) are a point halfway between the anterior axillary fold and the acromion process and a point in the center of the triangle formed by the two heads of the sternocleidomastoid muscle as it joins the clavicle. The venipuncture needle is advanced along the line which joins these points. is placed in Trendelenburg’s The patient position to elevate the central venous pressure and thereby reduce the likelihood of air embolus. The skin is prepared jvith
Fig. 2. Right sagittal view of thorax at point of entry of the needle into the subclavian vein. Note the simplicity of “walking down” the posterior surface of the clavicle into the subclavian vein. (A more perpendicular approach predisposes to entry into the artery and/or pleura.)
Fig. 1. Illustration of regional anatomy. Note the direct proximity of the subclavian vein to the posterior surface of the superimposed clavicle and consider the presence of only supportive structures (pectoralis major muscle, subclavian muscle, and/or costoclavicular ligament) between the skin and the vein. (From Sobotta-Figge Atlas of Human Anatomy, Vol. III, Part 1, Fig. 46, New York, 1964, Hafner Publishing Company, by permission.)
Fig. 3. Photograph depicting the safe angle of advancement of the needle from the mid point between the anterior axillary fold and the acromion process (W~OUU) to the center of the triangle formed by the two heads of the sternocleidomastoid muscle.
PerclltaneoLls subclavian
catheterization
of right heart
483
I / ‘F
FUSION
BOTTLE
\ \ \ I\ \\ I I
Fig. 4. cubital and the by the (middle superior
Contrast medium injected via the median vein. Note the large valves (Zo~,er left arrows) tortuous course of the distal veins bypassed catheter as it enters the subclavian vein arrow), and the tip of the catheter in the ven3 cava (right arroW).
antiseptic solution,* and the landmarks are noted. Local anesthetic may be injected along the path to be taken by the venipuncture needle, including the periosteum of the clavicle. Through the use of sterile technique, a 2-inch, 14-gauge, thinwalled needle (separated from the standard Intracath set) is attached to a lo-C.C. syringe partially filled with saline. The needle is then inserted inferior to the clavicle, according to the directions previously described. After cutaneous puncture, a small amount of saline is injected to insure continued patency of the needle. The needle is slowly advanced while negative pressure is applied through the syringe. Care is taken to avoid disturbing the external anatomy prior to advancement of the needle so that the motion of the catheter follows a straight line from skin to vein (Fig. 3). In this manner, maneuverability of the catheter is excellent as the tortuous course from the arm to the heart is bypassed (Fig. 4). The needle is “\valked *Betadine burg,
Solulion, \‘a.
Physicians
Products
Co.,
Inc.,
Peters-
i 1 I : : : : I’ I \ \
DRAW BLOOD OR I.V. MEDICATION
Fig. 5. Readily available arrangement for bedside monitoring. Note that a pressure transducer may be attached directly at the top of the 3-way stopcock via a 20-gauge needle for simultaneous recording of pressure and administration of fluid. Depicted is a most adaptable plastic stopcock and tubing. All connections must be taped to avoid obvious possible complications. The Intracath is taped to the subclavicular areas as with Intracaths used in peripheral veins. A hemostatic suture may be placed if the needle puncture causes cutaneous bleeding.
down” the posterior surface of the clavicle while the syringe is kept adjacent to the chest \vall. This aids in avoiding structures subjacent to the subclavian vein. Entry into the subclavian vein is indicated by a sudden free flow of blood. The needle is stabilized with the forceps, the syringe is disengaged, and the sterile 36-inch, 17gauge Intracath is passed through the needle to the desired depth. The needle is withdrawn and the catheter advanced and manipulated in the usual mamler. If the catheter fails to pass smoothly through the needle into the vein, a slight adjustment in the position of the needle may he necessary to assure that it has not inadvertent11 passed from the venous lumen. The cath-
484
Guide, Malinak,
McMullen,
l’urell,
eter should not be withdrawn through the sharp needle, since the tip of the catheter may be easily severed subcutaneously. The procedure has been done both with and without the nylon stylus in place. The Intracath may be attached to a standard infusion set for the administration of fluids or to appropriate adaptors for purposes of monitoring pressure prior to insertion through the needle (Fig. 5). Discussion
This method provides a rapid catheterization technique. Discomfort to the patient is decreased and quality tracings are obtained. Ectopic premature contractions caused by this flexible, lightweight catheter are rare. Because of the size of the vessel, venospasm is not encountered. When more specialized catheters are indicated, they may be inserted using a flexible catheter guide.? Angiograms and postmortem studies have not demonstrated the formation of hematomas or vascular extravasation at the site of venipuncture. Contrast medium was injected via the antecubital vein with a catheter in place (Fig. 4). Note the valves in the basilic vein and the tortuous course of the cephalic vein which are bypassed by this procedure. A repeat injection was made during a strenuous Valsalva maneuver simultaneous with removal of the catheter and further depicted no extravasation even with markedly elevated central venous pressure. Of the 412 patients, 17 have been studied at autopsy. The site of venipuncture was often difficult to demonstrate, and again there were no hematomas. Histologically, phlebitis was not observed. In one patient who had intractable shock and congestive heart failure secondary to myocardial infarction a small 1-by-3-mm. thrombus was noted at the tip of the catheter where it lay in the superior vena cava. No other complications have been noted at autopsy. Among the patients who survived their illnesses, only 4 suffered possible complications from the catheter, despite constant use in several for over 2 months: (1) One patient developed minimal inflammation at the site of skin entry after 2 weeks. This cleared spontaneously with removal of the catheter. (2 and 3) Staphylococcal
Am. Hcnrt I. October, 1965
and Hunson
septicemia occurred in one patient while a catheter was in place. Prior to subclavian venipuncture, a septic course and a postoperative abdominal fistula with abscess formation were present. She responded well to therapy. Pneumococcal septicemia also was observed in one patient who had pneumococcal pneumonia. (4) In a patient with pulmonary metastatic choriocarcinoma the right subclavian artery was entered and the needle immediately withdrawn. The left subclavian vein was then catheterized. Eight hours later, symptoms of a serosanguineous pleural effusion were noted. The effusion was aspirated. Two weeks later a repeat aspiration was undertaken when she again developed an effusion. She responded to methotrexate.* Because of the recurrence it seemsunlikely that the first effusion resulted solely from the arterial puncture. By romparison, considerable morbidity (28 per cent) has been reported in a recent article” describing direct percutaneous catheterization of the pulmonary artery. Our method is far safer and more adaptable than this technique and capable of giving the same information. It is often desirable to obtain mixed venous blood repeatedly~ for laboratory study and to be able to perform catheterization of the pulmonary artery at the bedside in critically ill patients. The advantages inherent in performing any catheterization in the laboratory must be weighed when one is deciding to do a bedside procedure. With the monitoring of the pressure pulse contour as the only guide, the subclavian approach has been used to position the catheter in the pulmonary artery. Infusion at that area, as well as the constant monitoring of pressure and aspiration of blood for laboratory studies, are easily accomplished by way of a three-way stopc0ck.i In many of the patients in whom the 12-inch catheter was used, venous pressure was monitored, intravenous medication was given, and blood was aspirated for laboratory studies without disturbing the patient. The patients appreciated the comfort of only one venipuncture, despite weeks and months of hospitalization. It appears that *Lederle Laboratories, Pearl River, N. Y. tK-SZL--3.way stopcock and extension Laboratories. Glendale, Calif.
tube,
Pharrnaseal
Percutaneous
this approach is far safer and more adaptable than that advocated in the reports previously noted. Summary A simple, rapid, inexpensive method of right heart catheterization using a disposable catheter has been presented. Sacrifice of a vein and scarring is avoided. Radiation of the patient is minimized because of prompt entry into the right ventricle and the ease of manipulation. Strict attention to every detail must be followed to avoid the previously reported complications.1,4 \Ve gratefully acknowledge the assistance of Miss Gloria Heard, Director, Department of Photography, Herman11 Hospital, for her work in the preparation of the movie of this procedure and of the photos in this paper. We further acknowledge the consultation and assistance of the Departments of Art and Photography of the Cleveland Clinic. REFERENCES 1. Wilson, J. N., Grow, J. B., Demong, C. V., Prevedel, A. E., and Owens, J. G.: Central venous pressure in optimal blood volume maintenance, Arch. Surg. 85563, 1962.
subclavian
catheterization
of right heart
48.5
2. Wilson, J. N., and Owens, J. C.: Continuous monitoring of venous pressure in optimal blood volume maintenance, Surg. Forum 12:94, 1961. 3. Wilson, J. N.: The management of acute circulatorv failure, Clin. North America 43:469. 1963: 4. Malinak, L. R., Guide, R. E., and Faris, A. M.: Percutaneous subclavian venipuncture for central venous pressure monitoring: Its aDpli.. cation to obstetric and gynecologk problems, Am. J. Obst. & Gvnec. In Dress. 5. Hanson, H. H.,*Gulde, k. E., Allen, H. C., F. F.: The effect of exoJr., and McMullen, genous thyroid and thyroid analogues on left ventricular work, peripheral resistance, cardiac output. and blood volume in athyreotic patients. Presented at the 9th Annual Meeting, The Society of Nuclear Medicine, Southwestern Chapter, Houston, Texas, March, 1964. 6. McMullen, F. F., Allen, H. C., Jr., Guide, R. E., and Hanson, H. H.: The use of center bore scintillation detection ‘crystal in constant monitoring of isotope tracers in cardiac shunt detector and estimation of cardiac output. Presented at the 9th Annual Meeting, *The Societv of Nuclear Medicine. Southwestern Chapter, Houston, Texas, March, 1964. 7. Seldinger, S. I.: Catheter replacement of the needle in percutaneous arteriography, Acta Radio]. 39:368, 1952. 8. Bryant, L. R. : Direct percutaneous pulmonary artery catheterization, J. Thorncic & Cardiox-as. Surg. 48:54, 1964.