What is a Cardiologist?

A cardiologist deals with diseases of the heart and blood vessels in adults. Blood vessels are the pipes that carry blood in the body.  A cardiologist trains as an internist and then develops a subspecialty as a cardiologist. 

Arteries are blood vessel that carry blood propelled from the heart, most carry oxygenated blood. Veins are blood vessel in which the blood slowly makes its way back to the heart, they contain valves that prevent back-flow and usually carry unoxygenated blood. Capillaries are microscopic vessels that form meshes of networks that connect smallish arteries (arterioles) and veins (venules).

Children with cardiovascular problems are treated by a pediatrician who develops a subspecialty in pediatric cardiology.

A cardiologist does not perform open-heart surgery. That is the work of a cardiac surgeon.

Heart anatomy:

From, http://freestock.ca/vintage_heraldry_g88-antique_anatomy_illustration__human_heart_blood_circulation_circa_1911_p3559.html

“Auricle” and “atrium” are interchangeable terms


Ancient History and the Middle Ages


Galen (129 – 217 CE) was an enormously influential Greek who lived in what is now Turkey. His architect father had a dream that he should become a physician, and Galen eventually treated several Roman emperors.

Medieval European scholars developed a reverence for the Greek and Roman works they discovered and translated. Unlike the ancient scholars, they abhorred experimentation and observation. It was enough to read what the ancients thought about an issue. So when Galen made a mistake it went virtually uncorrected for 1300 years.

Because he dissected animals, he knew that the heart has four chambers. There are two small atria (atria, plural; atrium, singular/ also known as auricles) on top and two large ventricles on the bottom divided by a septum. It is organized into right and left sides.

Galen’s mistake was that he thought there were two separate blood systems. He thought venous blood was generated by the liver from the contents of food and was dark, thick, and nourished the body. (The portal vein actually does connect the intestines and the liver.) Venous blood made its way through the right ventricle of the heart on its way to the lungs.

 In Galen’s system the heart’s main job was to heat up the blood of the arteries. It did this in the left ventricle with a fire fed by air supplied by the pulmonary veins (filled with air, not blood).  When you dissect an animal the some vessels are empty- one could conclude they are for pumping air, not blood. Venous blood leaked from the right ventricle across the wall dividing the two ventricles into the left ventricle and then was pumped out to the body. This arterial blood was thinner, lighter, and warmer.

Ibn al-Nafis (1213-1288) of Damascus was the first to figure out what was really going on. However, his ideas were not well known. An Englishman William Harvey (1578-1657) , independently rediscovered and expanded on the actual circulation pattern of the blood.

Circulation of the Blood

What Harvey and al-Nafis discovered was that the right ventricle pumps deoxygenated blood to the lungs through pulmonary arteries. There the blood picks up oxygen and returns by the pulmonary veins to the left atrium (auricle) and the left ventricle pumps the oxygenated blood out to the body. The deoxygenated blood returns to the heart at the right atrium. So, the pulmonary veins contain no air, but do carry oxygenated blood.

Barbers and Physicians

If you go to a barbershop today they will cut your hair and may go as far as applying a styptic to a cut. In medieval Europe they also performed medical procedures such as amputating limbs and applying leeches to draw blood. Physicians were university-trained and preferred not to get their hands dirty. However, they might recommend concoctions to relieve symptoms. Cardiologists are descended from the medieval physician; cardiac surgeons are descended, in part, from the medieval barber.


The Twentieth Century

 Willem Einthoven (1860-1927) was born of Dutch parents in Indonesia, moving back to the Netherlands when he was 10.  He developed an early version of the electrocardiogram in 1901. He was awarded the Nobel Prize in 1924 for this work. This device is based on the observation that heart muscle not acts as a pump, but has electrical properties as well. It generates and responds to electrical current.  Specialized cells, called pacemakers, initiate spikes in voltage. In fact, a heart removed from the body will keep on beating for some time.  However, the central nervous can prod the heart to speed up or slow down.

A healthy heart displays a pattern of voltage changes that can be measured with the electrocardiogram.

Helen B. Taussig (1898-1986) was a cardiologist who was central to the founding of the field of pediatric cardiology. She was born in Massachusetts, descended from several generations of physicians and academics. However, she struggled with dyslexia and was refused entry to Harvard Medical School as a woman. After she graduated from Johns Hopkins University School of Medicine she became interested in “blue baby syndrome.” Whenever a patient is oxygen deprived their blood takes on a blue tint which can be visible in skin tone.

A developing fetus does not use its lungs but receives oxygen from its mother.  In the fetus, much blood is diverted from the lungs by the ductus arteriosus which normally closes at birth when the lungs become operational. Taussig noticed that the ductus arteriosus stayed open longer in children that had better survival when suffering from the Tetralogy of Fallot. That is, an abnormal ductus arteriosus can help the baby survive this condition.

A “tetralogy” is a group of four. The two most important features of the Tetralogy of Fallot are ones in which there is a hole in the septum between the right and left ventricle and the entrance to the aorta is pulled over this hole.  This means unoxygenated blood of the right ventricle is mixed with the oxygenated blood of the left ventricle sent through the aorta to the body, and that not enough blood is reaching the lungs.

She reasoned correctly that, in the tetralogy, the blood traveled backwards through ductus arteriosus.  This allowed additional blood to make its way from the aorta to the lungs.  This suggested that the “pipes” of the circulatory system could be manipulated like plumbing to produce a desired effect.

She presented her ideas to the chief of surgery at Johns Hopkins University Hospital, Alfred Blalock (1899-1964), and his trusted technician, Vivien Thomas (1910-1985). These two gentlemen are a remarkable story in their own right. Despite the fact that they worked in the Jim Crow era in the south, Blalock had become more and more reliant on the technical abilities of Thomas, an African-American with a high school education. They had performed “plumbing” on dogs in research before and were able to develop a procedure in which arterial blood was diverted to the lungs in babies suffering from the Tetralogy of Fallot. Thomas was in the operating room coaching Blalock through the first attempts at the procedure. The operation was a great success and led to the development of many surgical procedures to repair congenital heart defects.

The story of Werner Forssmann (1904-1979) is extremely dramatic (see Forester). He was working in a small town hospital in his native Germany before World War II, when he became obsessed with the idea of having direct access to the patient’s heart. He came up with the idea of pushing a sterile urinary catheter up a cut vein to the heart. This technique eventually would be called “cardiac catheterization.” As he couldn’t get permission to do the experiment he seduced the nurse in charge of the supplies. When he got the supplies he needed he started the experiment, numbing his left arm, cutting open a vein, shoving the sterile urinary catheter up into it towards his heart, walked down the hall with the catheter in his arm to the X-ray room, wrestled with his physician-friend who was trying to stop him, and took an X-ray of the thin tube sticking into his right atrium.

He did this experiment many times, sometimes with approval, but was eventually fired.  Other physicians used his tool deliver x-ray opaque dyes to the heart so clearer pictures could be taken in relief.  Many years later Forssmann shared in the Nobel Prize for this work.


The Career of a Cardiologist

In the United States, after four years of post-graduate education in medical school, a prospective cardiologist will complete at least three years of a residency in Internal Medicine. So, they are “internists” first. Afterwards they become “Cardiology Fellows” for 3-6 years and then apply to be board certified. They work 57.5 hours per week, on average, with average base salary of $512,000.00 according to Forbes.com.

A cardiogeriatric internest specializes in the treatment of older patients.


Professional Organizations for Cardiologists

The American College of Cardiology is an organization open to physicians, nurses, technicians, and administrators. The influential American Heart Association is a voluntary organization founded by cardiologists dedicated to promoting cardiovascular health.

Disorders Treated by Cardiologist: Stenosis

The hollow inside of any tube in biology is a lumen. Stenosis is the narrowing of a lumen, including a blood vessel.  Stenosis of a blood vessel might be the result of atherosclerosis which is the result of a deposit called plaque composed of fat, cholesterol, and calcium. After Werner Forssmann developed cardiac catheterization, André Cournand and Dickinson Richards working at Bellevue Hospital in New York modified it by using it to inject x-ray-opaque dyes into the heart to help produce diagnostic images. This evolved into vascular radiology, in which cardiologists produced images of the cardiovascular system.

Eventually one of these vascular radiologists, Charles Dotter (1920-1985), used the catheter to treat a vessel. He inserted a stent into a clogged artery in a patient’s leg.  This is referred to as interventional radiology- a term that is nonsensical if decoded.  That is, radiology visualizes structures with radiation and it is not directly related to intervention.  

Andreas Gruentzig (1939-1985) modified this technique further by using the catheter to bring a balloon to bear against the stenosis in a vessel. The inflated balloon stretches and opens up the clogged vessel. This technique is called balloon angioplasty and can be applied to the coronary arteries of the heart, the carotid arteries of the neck, the peripheral vessels throughout the body, veins, and the renal artery that nourishes the kidney.

Disorders Treated by Cardiologist: Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy is an inherited genetic condition that results in a thickening of the heart. (“myo” means muscle; “pathos” means disease) It could be the result of the mutation in one of a dozen genes. The heart muscle must beat in a coordinated way once every second. When the heart muscle cells don’t develop correctly because of these mutations, they overcompensate and the heart muscle tissue becomes thicker and the heart larger. It usually is not stronger but, in fact weaker, and less effective at pumping blood. For reasons that are not well-understood, there are a wide range of outcomes once this condition is diagnosed.

Diagnosis is made by echocardiogram which emits high pitched sound waves and then records them as they bounce off internal structures. It is similar to the sonogram of a developing baby.

Treatment includes the use of beta-blockers.

Disorders Treated by Cardiologist: Broken Heart Syndrome

Broken Heart Syndrome is a form of cardiomyopathy that results in a weakening of the left ventricle. It is brought on by severe emotional stress. Stressors might include domestic violence, a bad diagnosis of an unrelated condition, the death of a love one, or getting fired. Death is rare and patients usually recover on their own without treatment.


Disorders Treated by Cardiologist: Restrictive Cardiomyopathy

Is a condition in which the heat muscle lacks elasticity. It cannot fill with blood efficiently between contractions. It may be the result of the inappropriate deposit of amyloid proteins. Treatment may include anticoagulants (blood thinners) and diuretics.


Disorders Treated by Cardiologist: Arrhythmia

Arrhythmia is any alteration in the normal rhythm of the beating of the heart. Heart muscle can generate and respond to electrical currents. Normally, the most rapid firing heart cells are the cells of the sinoatrial node (SA). However, if they adopt an unusual firing pattern or the normal pathways of current conduction are interrupted, or if other heart cells begin to fire more rapidly than the SA node- then an arrhythmia may develop. This can be diagnosed by an EKG.

Atrial fibrillation is when the atria (auricles) don’t effectively pump blood to the ventricles. It dramatically increases the risk of stroke due to the dislodging of a clot.

Bradycardia is a slow heart rate. It can lead to fainting, weakness, and dizziness.

Tachycardia is an excessively fast heart rate. When this happens, the heart doesn’t fill completely before pumping again. In extreme cases this can lead to cardiac arrest.

Ventricular fibrillation is the most serious arrhythmia; it is a disorganized pumping by the ventricles that can result in the complete inability to pump blood and cardiac arrest.

All arrhythmias are a break down in the normal pattern of electrical changes in the heart. They can be reset, and in the case of cardiac arrest, must be reset.

In 1955 Paul Zoll (1911- 1999) resuscitated a patient by applying alternating current to his chest. In 1959, Bernard Lown (1921) was confronted with a patient with bradycardia and applied alternating current to his chest, bringing short term relief. He eventually realized that direct current was tolerated better and this led to his development of the defibrillator that we use today.

A “cardiac electrophysiologist” is a physician that specializes in the diagnosis and treatment of arrhythmias due to abnormal electrical activity of the heart. They receive an additional year or two of training beyond that of a normal cardiologist. They might treat arrhythmias by using a catheter to destroy cells with rogue electrical activity. This is called “ablation.”

Alternatively, the cardiac electrophysiologist might implant pacemakers, which generate current to prompt the heart to beat at a normal rate. An implanted defibrillator applies a more intense shock.

Disorders Treated by Cardiologist: Myocardial Infarction

The myocardial infarction, or heart attack, is a sudden block of the blood flow to the coronary arteries that service the heart muscle. The heart may cease to work effectively, or at all. It may be preceded by reduced flow that is perceived as chronic chest pain, also known as angina.

When a patient presents in the emergency room diagnosed as suffering a heart attack they are provided oxygen, nitrates (to improve cardiac output), anti-coagulants (to prevent blood clots), coronary angioplasty, angiotensin inhibitors (that widen blood vessels), and beta-blockers.

Beta-Blockers act against the activity of adrenalin and noradrenalin (also known as epinephrine and norepinephrine) that are hormones that the body releases during flight or fight responses. These are situations that the individual perceives as dangerous that may require running for one’s life or fighting for one’s life. It increases the heart rate, blood pressure, and blood flow to the voluntary muscles- while decreases the flow of blood to the digestive system.

Like many hormones, adrenalin affects its target cells without entering them. There is a protein on the surface of the cell that serves as the receptor.  In the case of Adrenalin, the receptor often is the β-adrenergic receptor.

Beta-blockers are drugs that prevent access of adrenalin to its receptor and thus preventing its effects.  These drugs are administered during a myocardial infarction to keep the heart from working too hard and damaging itself. They also seem to serve this purpose in hypertrophic cardiomyopathy. Beta-blockers were used against hypertension in the past but they have been replaced by diuretics, angiotensin-converting enzyme (ACE), inhibitors, angiotensin-receptor blockers, and calcium-channel blockers.



The left ventricle sends blood out to the body under pressure. The pressure in the arteries when the ventricle is contracting is called systolic. The pressure when the left ventricle is briefly at rest is the diastolic. Blood pressure is measured with a sphygmomanometer. This device includes an inflatable cuff that can be wrapped around the left arm, and the air pressure in the cuff is measureable. The caregiver listens to blood flow through the artery of the arm with a stethoscope. 

First, the cuff is filled to an extreme pressure that stops blood flow through the arm. With no blood flow, the arm is silent. The pressure is released, and when the blood starts to flow the stethoscope will pick up noise. This means that the systolic pressure is strong enough to overcome the pressure of the cuff, although it proceeds with turbulence.  The pressure at which the blood flows is the systolic pressure. The caregiver continues to release pressure. When the pressure of the cuff no longer causes noisy turbulence, this is recorded as the diastolic pressure.

The normal systolic pressure is 120 mm Hg. The normal diastolic pressure is 80 mm Hg. “mm Hg” is millimeters mercury- or how high the mercury rises in the glass tube of the old-fashioned sphygmomanometer.

High blood pressure can lead to heart attacks, strokes, aneurysm, and kidney damage.

Blood pressure readings are typically given as systolic/diastolic pressure:

120-139/ 80-89 mm Hg may suggest lifestyle changes.

140-159/ 90-99 mm Hg may require medication in addition lifestyle changes.

Over 160/ over 100 mm Hg will certainly require medication.

And over 180/ over 110 mm Hg will require emergency care.

Harvey Cushing (1869-1939) introduced blood pressure measurements to the US.  He picked up this insight from Dr. Scipione Riva-Rocci on an Italian trip in 1896.


Disorders Treated by Cardiologist: Coronary Artery Disease

Coronary Artery Disease is a narrowing of the blood vessels that supply blood to the heart muscle. It can result in angina, heart failure, arrhythmia, and heart attacks. It can be treated by balloon angioplasty or the insertion of a stent.

 Other treatments include coronary bypass surgery, performed by Cardiovascular Surgeon. In this surgery, a healthy blood vessel is transplanted as a shunt to the coronary artery network- bypassing the occluded vessel.

An interesting potential therapy depends on collateral arteries. These are rarely used “extra” coronary arteries that might only be used if the normal coronary arteries fail. If the failure of the coronary arteries is gradual some individuals make use of their collateral arteries.  It is thought that heart could be encouraged to produce new collateral arteries as a response to coronary artery disease.

Disorders Treated by Cardiologist: Heart Failure

Heart Failure is a general condition in which the heart is unable to pump blood efficiently.  It may result from high blood pressure or coronary heart disease.



Humans may have always intuitively known that a healthy heart is central to one’s life. Throughout history, well-meaning physicians have been reluctant to aggressively treat the cardiovascular system. It was held in too much reverence and awe.  Some of the early cardiologists, like Harvey, seem a little arrogant for trespassing into the heart of the human body.

While others, like Forssmann, seem a little reckless. However because of their work a cardiologist of today enters this “temple,” not only with respect, but with confidence born of evidence based medicine.




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