Ka-thump ka-thump ka-thump.

Listening to the heart.  I do it every day on countless patients.  While this isn't the most important thing I do (usually), there is still something special about hearing a person's heart beating.  It is the measure of life.

In a patient record, this mystical experience is reduced to:

Cor - RRR s M/G/R

Which means:

Heart exam - Regular rate and rhythm without murmurs, gallops, or rubs

Which is translated:

The heartbeat is of normal speed and consistent rhythm, without any extra sounds indicating abnormalities of the heart.

Of course, this part of the exam requires a tool: The Stethoscope

Listening Device

doctor_with_stethoscope For medical students, one of the milestones made is when they get their first stethoscope.  Doctors share other devices for medical exam, but they generally own their own stethoscope.  I have a picture of Scooby Doo on mine.

I doubt the guy on the left has Scooby Doo on his.

It takes a bit of time to get used to stethoscopes.  They hurt your ears when you first start using them.  I usually use soft ear pieces that make the scope more comfortable to wear.  Some clinicians use hard ear pieces.  I suspect that they are punishing themselves for something; either that or their ears have developed calluses.

There are two sides of the other end of the stethoscope (the end you put on people's chests): the bell and the diaphragm.  The diaphragm is used the most, and is used for higher-pitched sounds.  The diaphragm is also the part that is chilled - to enhance the patient experience.   The bell is used for listening for lower-pitched sounds.

Most stethoscopes are just a series of tubes - very low tech.  Some newer scopes have electronics in them to enhance the sound quality.  My partner had one of these for a while.  It worked too good.  It made normal heart and blood vessels sound abnormal.  He sent it back.

Lub Dub

The heart beats with two cycles: Systole (sis-toe-lee) and Diastole (die-ass-toe-lee).  Sorry if I embarrassed anyone with that last one.  In systole, the heart's main chambers are squeezing, causing the mitral and tricuspid valves to shut, making the first heart sound, or S1.  Diastole is when the heart relaxes and the main chamber refills with blood, causing the aortic and pulmonic valves to snap shut, making the second heart sound, or S2.

350px-Diagram_of_the_human_heart_(cropped).svg

The heart is usually not colored in such a pretty way.

When listening to the heart, the clinician is listening for the two heart sounds.  Consistent-sounding and regularly spaced sounds are a sign of a healthy heart.  Normal adults have heart rates of 60-100, although athletes (whose hearts pump more blood with each beat) can operate with much lower heart rates.

Problems with the heart valves will sometimes result in turbulent flow over the valve, causing the heart sound to be a "whoosh" rather than a "thump."  I will go into heart murmurs in more detail in the second post about the heart.

Mythological Hoof Beats

torchlt1 There are two more heart sounds that physicians are taught about in medical school: S3 and S4.  A person with an S3 gallop, we were taught, will have heart sounds making the rhythm of the word "Kentucky" - three fairly evenly spaced sounds.  The S4, on the other hand, will have sounds making the rhythm of the word "Tennessee" - where the three syllables come quick, and then are followed by a pause.

From this one might conclude that the 3rd and 4th heart sounds happen when the heart uses chewing tobacco, but that would be incorrect.  The real cause of the S3 gallop is described as follows:

S3 is thought to be caused by the oscillation of blood back and forth between the walls of the ventricles initiated by inrushing blood from the atria. The reason the third heart sound does not occur until the middle third of diastole is probably because during the early part of diastole, the ventricles are not filled sufficiently to create enough tension for reverberation. It may also be a result of tensing of the chordae tendineae during rapid filling and expansion of the ventricle.

So it is basically the vibration of the heart wall like a rubber band.  I prefer the following description:

340x The S3 is caused by the intense desire of cardiologists to feel superior to other doctors.  They have invented this sound for the sole purpose of making other doctors embarrassed that they can't hear it, while the cardiologist says "it's obvious."  This is often heard on cardiology rounds, where the cardiologist listens to the heart of a patient carefully and proclaims, "listen to this patient for a very clear S3 gallop."  The medical students and residents each spend five minutes listening to the heart trying to hear the mythical sound, nodding their heads to avoid embarrassment.

Those who fake it the best are those who are chosen for cardiology fellowships.

I have never heard an S3, but I have faked it several times.  It is said to be a sign of heart failure (the gallop, not the faking).

The cause of the S4 is described:

S4 is caused by the atria contracting forcefully in an effort to overcome an abnormally stiff or hypertrophic ventricle. This causes abnormal turbulence in the flow of blood that can be detected by a stethoscope.

Which is to say that the S4 is like the atrium (or smaller heart chamber) grunting as it tries to push blood into a stiff ventricle (or larger chamber).  I think I have heard an S4 gallop, but I am not certain.  It could have just been that stampede of caribou in the room next to me.

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Got Rhythm?

discofire Do you feel awkward on the dance floor?  Do you feel like you move when you shouldn't?  Do you look like a person with a rare neurological condition when you are trying to two-step?  If so, you know how the heart sometimes feels.

The heart normally has a good sense of rhythm.  It beats with the regularity of the pounding sound coming from the 2 trillion watt speakers in the back of a teenager's car.  It does so without complaint, day and night, rain or shine.  The heart really likes to "shake it's groove thing."

The regular rhythm is produced by an electrical impulse traveling down electrically conductive cells (or purkinje fibers) that cause the heart to contract.  This electric pulse normally starts from the pacemaker of the heart, or SA Node.

But sometimes, the groove thing just won't shake, and the heart goes into an irregular rhythm.  There are many ways for this to happen, including:

Extra beats thrown in the middle of the regular ones.  This are called premature contractions, and are usually no big deal.  They can happen at regular intervals or just randomly.  It is quite easy to experience premature contractions; just drink three cans of Red Bull and let the fun begin.

Fast regular beats.  Whether this is good or terrible depends on where the beats start from. 

  • If they start from the SA node, then it is called Sinus Tachycardia, and is a generally benign condition.  This condition can also be caused by drinking Red Bull, as well as by watching Victoria's Secret commercials
  • If the fast beats come from other parts of the atrium (or small chamber), it is an atrial tachycardia, which is possibly a more serious, but not life-threatening problem.
  • If the fast beats come from the ventricle (or large chamber), it is called ventricular tachycardia.  This means you are in deep yogurt.  It is really bad.
  • If the beats come from the car next to you at the intersection, then it is only dangerous if you open your window and give them the finger.  Don't do that.

band-middle-84 Irregular beats.  These beats come randomly - kind of like the percussion section of a middle-school band (and possibly just as dangerous).  The common cause of this condition is called atrial fibrillation.  A Fib happens when the pacemaker goes haywire, and signals the heart to beat at a very high rate.  Fortunately, the heart can ignore the rapid random beats of the SA Node, so that the whole heart doesn't go at a dangerously fast rate. 

I am going to stop here, as I am running out of bizarre analogies.  When I think of more, I will finish with the rest of the heart exam.

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