The Patient Was…

The patient was a young-middle-aged man whom I encountered when I was part of a small group of medical students on a “clinical rotation” at another medical center. A clinical rotation is a period of time spent in more-or-less hands-on training in a particular area of medical education; textbooks are pretty much left behind, and students are exposed to actual patient care under supervision of preceptors or instructors.

The patient, in this case, was our instructor!

He was a full Professor of Cardiology at the medical school we were visiting. His specialty was cardiac arrythmias, disorders of the heartbeat or rhythm of the heart. There are many different types of heart rhythm disturbances, varying from mild and innocuous to serious and life-threatening. And there are many ways of treating these different disorders.

We were in a small conference room, seated around a rectangular table with the Professor at the head of the table. The topic we were discussing involved actual hands-on procedures  —  touching patients in appropriate places and ways  —  to terminate irregularities of the heartbeat and restore normal heart rhythm.

One technique we’ve discussed in an earlier posting on this blog involves striking a sharp blow with the side of the hand (like a karate chop) to the center of the chest, over the breastbone, in instances of a person’s sudden collapse and loss of a palpable pulse. The procedure takes only a second or two, so valuable time isn’t wasted. It doesn’t matter if the underlying problem is actual loss of all electrical activity of the heart, so-called cardiac standstill, or a rapid and irregular rhythm abnormality called ventricular fibrillation where the heart simply quivers but doesn’t contract to pump blood. If a regular rhythm is restored after one or two chest thumps the problem is temporarily resolved. If it doesn’t work  —  and it usually doesn’t!  —  then one must move on to standard CPR (Cardiopulmonary Resuscitation).

Another hands-on technique, used in instances where an abnormal, rapid heart rhythm originates in one of the two upper chambers of the heart (the right and left atria), is called Carotid Sinus Massage. The physiology behind this maneuver is a bit complicated, but when the procedure is performed correctly in the appropriate patient, it can terminate the abnormal heart rhythm and restore normalcy to the heartbeat.

Carotid Sinus Massage was the topic of our little seminar that day.

The carotid arteries, located on either side of the neck, are the primary blood vessels that carry blood to the brain. The two major carotid arteries, called the common carotid arteries, each divide in the neck into a so-called internal and external carotid artery. At this area of artery division is a slight bulge or enlargement of the blood vessels called the carotid sinus. And this structure contains specialized nerve fibers, called baroreceptors, that are sensitive to  changes in pressure.

The pressure to which these baroreceptors respond can be internal, from the force of pumped blood against the blood vessel wall, or external from mechanical pressure applied from outside the body. Thus, high blood pressure can stimulate the baroreceptors from inside the blood vessels, and pressing on the carotid sinus from outside can stimulate the baroreceptors, as well.

The baroreceptors themselves are part of what is called the autonomic nervous system; this is the part of the nervous system of your body that controls things that are involuntary, not under your control (think automatic), such as heart rate, breathing, dilation of the pupils of the eyes. The second major part of the nervous system is called the somatic nervous system, which controls voluntary muscle movements like those involved in walking and talking.

The baroreceptors, being part of the autonomic nervous system, are not under our general control. (I was involved, at one time, in failed research at Rockefeller University that tried to establish some control over heart rhythms and digestive processes.) The autonomic nervous system has two main components, the “sympathetic nervous system” and the “parasympathetic nervous system.” While both components are complicated in themselves, you can think of the “sympathetic system” as one of activation and stimulation (think adrenaline and “fight or flight” responses), and the “parasympathetic system” as one of rest and repose (imagine slowing things down).

When carotid sinus massage is employed to try to control an arrythmia it takes advantage of the parasympathetic nervous system. The mechanical pressure on the carotid sinus from pressing and rubbing it from the outside of the neck causes parasympathetic nerve fibers in the carotid sinus to send nerve impulses that try to slow the rapid heart rate. When successful, the abnormal rhythm terminates and normal heart rhythm is restored.

So, what can go wrong?

One real possibility is that the carotid sinus is too sensitive. In fact, the condition is called “carotid sinus hypersensitivity,” and the resulting symptoms are known as “hypersensitive carotid sinus syndrome.” In this circumstance, stimulation of the parasympathetic nerve fibers in the carotid sinus slows the heart so much and often causes such a marked drop in blood pressure that the patient passes out.

Well, there we were, a group of medical students sitting around a conference table discussing carotid sinus massage. The Professor described the simple technique, then touched his neck to show us the appropriate spot to do the massage. As soon as he touched his neck, his head dropped and he slumped forward onto the conference table.

We all sat there, not moving or saying anything. A few moments later, the Professor lifted his head as if nothing had happened. I remember thinking, Wow, what a demonstration; I’ll never forget carotid sinus hypersensitivity.

The Professor looked at us, and said, “That’s never happened before, All I did was touch my neck, like this.”

And he did it again. And once more, he slumped forward onto the table. None of us moved or spoke. In a few seconds, the Professor sat back up and now he really looked perturbed.

“Gentlemen,” he said to us, “this is not a demonstration. I’ve been running this seminar for a long time. It’s hard for me to believe that the simplest, lightest touch over my carotid sinus, which I’ve done for years, could do this to me.”

And without thinking he once more touched his neck. Damn, if he didn’t pass out on the table again.  This time, as he awakened, we students were a frightened and synchronized chorus.

“Doctor, don’t do that again!”