Yes, this is part 2. If you read this before reading part 1 you will totally spoil it for yourself. Please read it in the proper order. I really don’t want to be responsible for traumatizing you.
The exam is written as follows:
Cor – RRR s M/G/R
The heart is going at a normal speed without irregular beats. There are no abnormal noises with the heart beat.
Since all of you (ahem) have read the previous post, I will dive right back into the aspects of a heart exam.
“Murmur” is probably one of the best words in the English language. It is fun to say and it sounds very much like a murmur – except a heart murmur. Heart murmurs don’t sound like people murmuring at all, unless it is a bunch of people with laryngitis. “Whoosh” more accurately describes what it sounds like and is fun to say, but it is not nearly as dignified as “Murmur.”
A murmur is caused by turbulent blood flow. Normal blood flow makes very little sound, much like a calm river does not make sound. When a river goes over rapids (turbulence), it gets noisier. The faster the blood flow, the louder the “whoosh.”
The main thing that causes turbulence is the narrowing of the path for the blood. Here’s the story of how this came to be known in the medical community:
There were two guys named Hagen and Poiseuille* who were really smart mathematicians. One day, as they were hanging out doing the “cool” things mathematicians do, they happened on the following formula:
They showed it to a bunch of doctors, whose reaction was: “Huh?”
The mathematical community delights in having three equal signs and multiple Greek numbers, but this is just not acceptable to the medical community (which strongly adheres to a “one equal sign per equation” policy). So the scientists simplified it, making the Hagen-Poiseuille Equation:
Unfortunately, the doctors still responded: “Huh?”
But then the scientists explained that the “DP” represents the change in pressure in a tube, like a blood vessel or airway in a patient. They also said that the doctors could ignore the stuff on the top on the fraction (which they were doing anyway). The important part is the bottom of the fraction:
which represents the number pi times the radius to the fourth power.
To which the doctors responded: “Huh?”
This really annoyed the scientists, but they explained how it relates to blood vessels and airways. The pressure in these tubes increases by the 4th power as the radius of that tube gets smaller. This makes the blood or air in those tubes move much faster, and hence more turbulent.
To which the doctors responded: “Ohhh….Now we get it!”
Hagen and Poiseuille headed immediately to the nearest bar and ordered stiff drinks.
*These scientists are no relation to Haagen and Dazs, who single-handedly doubled the income of cardiologists
So what is the significance of this story? When blood is forced through a smaller space, it speeds up and makes noise. If it is in a blood vessel, it is called a bruit (pronounced “broo-ee”, and to be covered in another post); if it is in the heart, it is called a murmur.
When, Where, What
When listening for murmurs, the examiner must address three things:
The two main heart sounds (S1 and S2, remember?) mark the boundaries of the two phases of a heart beat. Between S1 and S2, the heart is squeezing blood out of the main chambers in the phase called systole. Between S2 and the next S1, the main chambers are relaxing and filling with blood in the phase called diasystole. So murmurs are classified as being either systolic or diastolic. Systolic murmurs happen because of turbulent flow coming out of the heart, while diastolic murmurs happen as blood enters the main chamber of the heart.
Think of the heart as a Whoopie Cushion. A diastolic murmur happens when you blow up the cushion. The noise is there, but not very loud. A systolic murmur happens when someone sits on that cushion, making a much louder sound. Systolic murmurs, however, don’t cause as much madcap hilarity as a Whoopie Cushion (except among cardiologists).
The location of murmurs tells much about their cause. In adults, the vast majority of murmurs happen because of abnormal flow across a heart valve.
There are four valves in the heart, three of which cause significant murmurs. The poor tricuspid valve gets the shaft here, as the pressure is just too low on both sides to cause much noise. Does it bring attention to itself? No, the tricuspid just does its job in silence. Before moving on to the noisy boys, let us tip our hats and hairpieces to the tricuspid valve.
Aortic Stenosis – When the left side of the heart squeezes, blood flows through the aortic valve and goes to the body. If there is narrowing of this valve, it makes this systolic murmur heard near the right collarbone.
Pulmonic Stenosis – In the same way, the right heart pushing blood through a narrow pulmonic valve causes this systolic murmur near the left collarbone.
Mitral Regurgitation – No, the Mitral (bicuspid) valve isn’t nauseated, it is having fluid going in the wrong direction. When the Mitral valve is leaky, the squeezing of the left heart causes blood to flow the wrong direction across that valve. It makes a systolic murmur heard around the left nipple.
Aortic Regurgitation – This is caused by a leaky Aortic valve. This allows backward flow over that valve when the left heart relaxes. This causes a diastolic murmur over the left mid-breastbone.
Mitral Stenosis - Blood entering the main chamber of the heart through a narrow Mitral valve makes a low diastolic rumble.
There are other murmurs caused by holes in the heart that happen in pediatric patients, but I am not going into that on this post.
The last clue as to what is causing a murmur is to what it sounds like.
- Is it high-pitched, or low pitched?
- Is it steady, or does it get loud then soft?
- Does it last the whole systole or diastole, or does it just last for part of it?
- How loud is it?
All of these give good ideas of the type and seriousness of the murmur.
The goal of the heart is to take blood from the body and pump it to the lungs, then pump blood from the lungs and send it back to the body. Each of these murmurs decreases the efficacy of these tasks. If valves get narrow or leaky enough, they need to be replaced.
What’s the Rub?
The last sound listened for is a rub. Rubs are caused by irritation of the pericardium (the sack that surrounds the heart). When the heart beats, it normally moves smoothly in the pericardium. If that sack is irritated, the inside is rough and causes a crunching sound when the heart beats.
Truthfully, heart rubs are among the sounds used to embarrass medical students. They are very hard to hear. I hear maybe one every couple of years. The biggest problem is that the movement of the stethoscope on the skin of the patient also sounds like crunching.
The Heart of the Exam
The heart exam is both literally and figuratively a central part of the exam. So far we have gotten halfway through the physical exam. Stick with me on this trip (taking lots of Dramamine). You have to wonder how I am going to handle some of the more “seedy” parts of the exam.
Heck, I wonder how I am going to handle them.This material, written by me, is free to re-post and share under the Creative Commons agreement. In other words, use it all you want; just give me credit.