Basic Auscultation Skills
Identification of a triple rather than a double set of heart sounds per cardiac cycle is a fundamental skill that can be acquired and honed by simply listening for it in every patient.
Initial auscultation skills focus on identifying heart sounds and being able to recognize systole and diastole. This is easily done in patients with slow heart rates; it is more difficult in patients with rapid heart rates. Similarly, in patients with a slow heart rate, it is easier to recognize additional heart sounds during the cardiac cycle. As one's experience increases, confidence increases with rapid heart rates - somewhat like recognizing a familiar piece of music at a faster tempo.
Significance of a Triple Rhythm
Identifying a triple rhythm does not provide a diagnosis. It is a stepping stone to further auscultation and may prompt diagnostic testing with echocardiography.
A triple rhythm is easy to understand irrespective of the level of training in cardiac auscultation. A beginning student can compare impressions with an experienced teacher. The two can simply discuss whether both are hearing a triple rhythm or not.
Reduplication is said to be present when two sounds are close together and are of similar quality. Reduplication of a heart sound together with the other normal sound in the cardiac cycle gives rise to a triple rhythm.
Splitting, or reduplication, of the first heart sound is heard in normal patients at the lower left sternal border. One is hearing the mitral and tricuspid components of S1. The split S1 and a single S2 result in a triple rhythm.
Splitting of the second heart sound is heard in normal patients at the upper left sternal border. One is hearing the aortic and pulmonic components of S2. In this case, the single S1 and a split S2 also result in a triple rhythm.
Timing the Triple Rhythm
The following discussion will focus on evaluating sounds that are split (reduplicated) in the proximity of the first heart sound.
The first heart sound should be identified in all patients. Reduplication in the proximity of S1 should be recognized, and one should develop an orderly approach to evaluating this finding.
Splitting of the first heart sound is likely to be heard in many normal patients at the lower left sternal border. The most accepted explanation is that one is hearing the mitral and tricuspid components of S1. The reason the splitting is confined to this area is that the tricuspid component of the first heart sound is only audible in that confined area at the lower left sternal border. In all other areas of the chest, the first heart sound is single because only the mitral component is audible.
A split, or reduplication of S1 however, could also indicate cardiac abnormalities. A right bundle branch block on the electrocardiogram may manifest as reduplication of S1.
One diagnostic approach during auscultation is to focus on two possibilities at a time and develop an ordered approach to distinguish between the two (as will be discussed next).
Distinguishing the Systolic Ejection Click
The presence of an early systolic ejection click is important to recognize because it may signal the presence of the most common congenital, non-cyanotic heart defect in the adult, namely, a bicuspid aortic valve.
There are also other explanations for an early systolic ejection click including hypertension, a dilated aorta, or pulmonic valve stenosis. Many times there will be no evident explanation and the the initial auscultatory finding of a triple rhythm prompts further diagnostic tests such as echocardiography.
The auscultatory approach, therefore, is to look for the features of an ejection click.
An ejection click is loud, and easily heard once it has been considered. One initially confounding auscultatory feature is the fact that an aortic ejection click may radiate to the "mitral area" at the apex, and indeed, may actually be louder at the apex than at the base.
It is therefore, important for the stethoscopist to remember that a triple rhythm at the apex may be due to the normal mitral component of the first heart sound, closely followed by the ejection click and ending the triple rhythm of this auscultatory cardiac cycle is a normal S2.
"First Heart Sound" at the Base
Thinking about the presence of an ejection click may help avoid another auscultatory pitfall, namely, assuming that a sound heard at the right upper sternal border is due to the mitral component of S1. The mitral component of the first heart sound (M1) radiates widely and is often audible at the base. This does not happen in all patients, and therefore should not be assumed to always be the case. Just because one hears a "first heart sound" at the right upper sternal border does not mean that this is M1. It may well be an early systolic ejection click, and the mitral component of the first heart sound (M1) may simply not be reaching that area.
The auscultation technique to evaluate this possibility uses the principle that the mitral component of the first heart sound should not be louder at the base than at the apex. The technique consists of simply moving the stethoscope from the right upper sternal border to the left ventricular apex and continuing back and forth until one has decided whether the intensity of the "first heart sound" is louder at the apex or at the base. If the intensity of this heart sound is clearly louder at the base, and furthermore, if there is clear splitting of the first heart sound at the apex, then the triple rhythm may be due to: M1 - closely followed by a systolic ejection click - followed by a normal S2. The "splitting of the first heart sound at the apex" is, in this case, a loud mitral component of the first heart sound closely followed by an even louder ejection click. Indeed, the ejection click may be louder at the apex than at the base, and it is frequently louder than M1. But, as already stated, M1 - the mitral component of the first heart sound should not be louder at the base than it is at the apex. In other words, if the sound in question is louder at the base, it is not coming from the mitral valve.
The presence of a bicuspid aortic valve is not always conclusively confirmed by echocardiography. Many patients are not easily scanned and the resolution is not always adequate to identify all three aortic leaflets, or to determine that there are two instead of three.
Listening for an aortic ejection click can help the clinician decide whether to proceed with more invasive testing. If there is a triple rhythm and careful auscultation suggests that is is due to an ejection click (as explained above), non-confirmatory transthoracic echocardiographic findings will not be accepted as conclusive.
In such cases, the echocardiography laboratory can be asked to perform a transesophageal echocardiographic study to further delineate aortic valve anatomy in order to confirm or refute more conclusively the auscultatory suspicion of a bicuspid aortic valve.
The contents and links on this page were last verified on March 1, 2004.
This information is intended for use by doctors and other healthcare professionals.
Daniel Shindler M.D., F.A.C.C.
Associate Professor of Medicine
UMDNJ - Robert Wood Johnson Medical School
Director, Echocardiography Laboratory
Robert Wood Johnson University Hospital
Editor: E-chocardiography Journal.
Moderator: International Echocardiography Discussion Group.