What are the three heart sounds when learning to auscultate (listen to) heart sounds?

From the Guidelines

When learning to identify heart sounds, it is crucial to focus on the three key beats: S1, S2, and S3, as they provide essential information for detecting abnormal heart sounds and murmurs. These sounds are fundamental in cardiac auscultation, a method that remains the most widely used for screening valvular heart disease [ 1 ]. The first heart sound, S1, often described as "lub," occurs at the beginning of systole when the mitral and tricuspid valves close. The second heart sound, S2, or "dub," happens at the end of systole with the closure of the aortic and pulmonic valves. The third heart sound, S3, is a low-pitched sound that occurs early in diastole and is normal in children and young adults but may indicate heart failure in older adults [ 1 ].

Key Points for Auscultation

• Use the diaphragm of the stethoscope for higher-pitched S1 and S2.
• Use the bell for the lower-pitched S3.
• Practice listening at different locations on the chest wall:
  • Mitral area (apex)
  • Tricuspid area (lower left sternal border)
  • Pulmonic area (upper left sternal border)
  • Aortic area (upper right sternal border)

Understanding these three beats is vital for establishing a foundation in detecting abnormal heart sounds and murmurs, which can be critical in diagnosing valvular, congenital, or other structural heart abnormalities [ 1 ]. The presence of a third heart sound at the apical area, for instance, suggests a failing left ventricle, emphasizing the importance of accurate auscultation skills in clinical practice [ 1 ].

Clinical Application

In real-life clinical medicine, the ability to accurately identify these heart sounds can significantly impact patient outcomes by facilitating early detection and management of heart diseases. For example, a patient presenting with symptoms suggestive of heart failure, such as dyspnea or fatigue, and found to have an S3 heart sound upon auscultation, would warrant further investigation, such as echocardiography, to assess left ventricular function [ 1 ]. This approach underscores the importance of integrating basic clinical skills, like cardiac auscultation, with advanced diagnostic tools for optimal patient care.

From the Research

Heart Sounds and Learning

• When learning to identify heart sounds, it's essential to understand the different components of the heartbeat, including the first, second, and sometimes third heart sounds [ 2 ].
• The first heart sound (S1) is caused by the closure of the mitral and tricuspid valves, while the second heart sound (S2) is caused by the closure of the aortic and pulmonary valves [ 3 ].
• In some cases, a third heart sound (S3) may be present, which is caused by the rapid filling of the ventricles [ 4 ].

Stress Echocardiography

• Stress echocardiography is a diagnostic test used to evaluate the heart's function under stress, typically induced by exercise or pharmacological agents [ 2 ].
• The test is used to diagnose and assess coronary heart disease, as well as valvular heart disease [ 3 ].
• Stress echocardiography has become a valuable means of cardiovascular stress testing, playing a crucial role in initial detection, determining prognosis, and therapeutic decision making [ 4 ].

ABCDE Protocol

• The ABCDE protocol is a new approach to stress echocardiography, assessing multiple vulnerabilities of the ischemic patient [ 5 ].
• The protocol includes five steps: regional wall motion, B-lines by lung ultrasound, left ventricular contractile reserve, coronary flow velocity reserve, and assessment of heart rate reserve [ 5 ].
• The ABCDE protocol offers insight into five functional reserves, allowing for better functional characterization, risk stratification, and personalized tailoring of therapy [ 5 ].

Cardiac Screening

• Cardiac screening with electrocardiography, stress echocardiography, or myocardial perfusion imaging can reveal findings associated with increased risk for coronary heart disease events [ 6 ].
• However, cardiac screening has not been shown to improve patient outcomes and is associated with potential harms due to false-positive results [ 6 ].
• Clinicians should focus on strategies for mitigating cardiovascular risk by treating modifiable risk factors and encouraging healthy levels of exercise, rather than relying on cardiac screening in asymptomatic, low-risk adults [ 6 ].