Alfred Blalock

Alfred Blalock (April 5, 1899 – September 15, 1964) was a 20th century American innovator in the field of medical science most noted for his research on the medical condition of shock and the development of the Blalock-Taussig Shunt, surgical relief of the cyanosis from Tetralogy of Fallot--known commonly as the blue baby syndrome--with his assistant Vivien Thomas and pediatric cardiologist Helen Taussig.

Birth and early career

Born in Culloden, Georgia, Blalock entered Georgia Military Academy, a preparatory school for the University of Georgia, at the age of 14. Having graduated from the University of Georgia in 1918 at the age of 19, Blalock subsequently entered Johns Hopkins Medical School, where he roomed with, became tennis doubles partner to, and began a lifetime friendship with Tinsley Harrison. Blalock earned his medical degree at Johns Hopkins in 1922. Hoping to gain appointment to a surgical residency at Johns Hopkins due to his admiration of William S. Halsted, Blalock remained in Baltimore over the next three years, completing an internship in urology, one year of an assistant residency on the general surgical service (his contract was not renewed), and an externship in ENT. He moved to Boston, Massachusetts in the summer of 1925 to begin a surgical residency at the Peter Bent Brigham Hospital, but left for Vanderbilt "without ever unpacking ^* trunk."

Vanderbilt University

In July of 1925, Blalock joined his good friend Harrison at Vanderbilt University in Nashville to serve as first chief resident in surgery under Barney Brooks, who was Vanderbilt University Hospital's first Professor of Surgery and Chief of the Surgical Service. Blalock was active in teaching third and fourth year medical students, and as a result was placed in charge of the surgical research laboratory. While at Vanderbilt University he worked on the nature and treatment of hemorrhagic and traumatic shock. Experimenting on dogs, he found that surgical shock resulted from the loss of blood, and he encouraged the use of blood plasma or whole blood products as treatment following the onset of shock. This research resulted in the saving of many lives during World War II. Unfortunately, Blalock met with frequent bouts of tuberculosis during his Vanderbilt years. His first paper on shock, published in 1927, was actually written by his friend Harrison based on the data that Blalock had completed but could not compile due to his illness. While at Vanderbilt in 1938, Blalock attempted to produce pulmonary hypertension in experiments joining the left subclavian artery to the left pulmonary artery. Although these experiment failed in their purpose, he returned to this idea years later.

Johns Hopkins

When Blalock was offered Chief of Surgery at Johns Hopkins in 1941, he requested that his assistant, Vivien Thomas, come along with him. They formed a very close relationship that would last more than 30 years. Together they developed a shunt technique to bypass aortic coarctation. While they were working on this, Helen Taussig presented him with the problem of the blue baby syndrome.

Blue Baby

In the normal heart, there are four separate chambers; the two top chambers are known as atria and pump blood simultaneously into the two bottom chambers, or ventricles. Blood first enters the heart at the right atrium, which then empties blood into the right ventricle, which pumps the blood into the lungs through the pulmonary artery to get oxygen. From the lungs, the blood enters the left atrium through the pulmonary vein; the left atrium empties into the left ventricle, which pumps the blood into the aorta and from there reaches the rest of the body. Because it is responsible for getting blood to the entire body through the aorta, the left ventricle is usually the biggest and strongest chamber of the heart.

The following is a depiction of normal blood flow through the body. Valves keep the blood from flowing backwards. Capital letters indicate blood that has been oxygenated:

veins → superior or inferior vena cava → right atrium ——tricuspid valve→ right ventricle ——pulmonary valve→ pulmonary artery → LUNGS → PULMONARY VEIN → LEFT ATRIUM ——mitral valve→ LEFT VENTRICLE ——aortic valve→ AORTA → ARTERIES

After the body uses up the oxygen delivered by the blood flowing through the arteries, then arterioles, then capillaries, the unoxygenated blood returns to the heart by the capillaries, then venules, then veins.

The blue baby syndrome, known as Tetralogy of Fallot (TOF), consists of an incomplete wall between the ventricles (known as a ventricular septal defect or VSD), an aorta that sits over this defect so that its blood comes from both ventricles instead of just from the left (overriding aorta), a defective right ventricular outflow tract near the pulmonary valve that prevents full flow of blood to the lungs, and a muscular right ventricle necessary to accomplish the extra work required to overcome that defect (right ventricular hypertrophy).

The following is a depiction of blood flow in Tetralogy of Fallot. Mixed capital letters indicate partially oxygenated blood.

veins → superior or inferior vena cava → right atrium ——tricuspid valve→ rIgHt vEnTrIcLe ——VSD→ LeFt VeNtRiClE or \__ ——pulmonary valve→ pulmonary artery → LUNGS → PULMONARY VEIN → LEFT ATRIUM ——mitral valve→ LeFt VeNtRiClE <—————————————————————————————————————————rIgHt vEnTrIcLe \__ ——aortic valve→ aOrTa → aRtErIeS

Unoxygenated blood from the right ventricle flows into the aorta preferentially because of the obstructed outflow tract into the lungs. This means less blood has the opportunity to be oxygenated in the lungs. Blood mixes abnormally between the left and right ventricles and into the aorta. Oxygen gives blood its reddish color. Cyanosis describes the "blueness" in the baby and results from the pumping of mixed oxygenated and unoxygenated blood throughout the body.

Blalock developed the idea for the operation from his aforementioned failed experiments on dogs. The shunt joins the left subclavian artery (normally oxygenated but partially oxygenated in TOF) to the left pulmonary artery (normally unoxygenated but with very little blood flow in TOF). This increases the amount of blood that goes into the lungs and is returned to the left side of the heart. As a result, more oxygenated blood is pumped to the rest of the body. Vivien Thomas perfected the surgical technique in the laboratory and instructed Blalock during the procedure. The first Blalock-Taussig shunt operation was performed on November 29, 1944 on Eileen Saxon and instantly restored her to a healthy "pink" color. Even though this surgery only prolonged Elieen's life for two months, it was pioneering pediatric heart surgery.

Film

In the 2004 HBO docudrama 0386792 about the Blalock-Thomas collaboration, Blalock was portrayed by Alan Rickman.

External links

http://www.medicalarchives.jhmi.edu/blbio.htm
http://www.medicalarchives.jhmi.edu/sgml/blalock.html
http://www.mc.vanderbilt.edu/biolib/hc/biopages/ablalock.html

References

Merrill WH, "What's Past is Prologue" Ann Thorac Surg 1999;68:2366-75