From the Guidelines
In atrial fibrillation (AF), the characteristic heart sounds include an irregularly irregular rhythm with variable intensity of the first heart sound (S1), a normal second heart sound (S2), and an absence of the fourth heart sound (S4). The first heart sound varies in intensity because the ventricular filling time changes with each beat due to the irregular atrial contractions 1. Some key points to consider when evaluating heart sounds in AF include:
- The irregularity of the rhythm is the most distinctive auscultatory finding in AF, often described as "irregularly irregular" because there is no discernible pattern to the heart beats, unlike other arrhythmias which may have predictable patterns of irregularity.
- Patients with AF may have a rapid heart rate (tachycardia), though this depends on the ventricular response rate.
- If AF is associated with underlying valvular disease, such as mitral stenosis, additional sounds like murmurs may be present.
- Physical examination may suggest AF on the basis of irregular pulse, irregular jugular venous pulsations, variation in the intensity of the first heart sound, or absence of a fourth sound heard previously during sinus rhythm 1. The diagnosis of AF requires confirmation by ECG recording, sometimes in the form of bedside telemetry or ambulatory Holter recordings 1. It's worth noting that the findings on examination are similar in patients with atrial flutter, except that the rhythm may be regular and rapid venous oscillations may occasionally be visible in the jugular pulse 1.
From the Research
Heart Sounds in Atrial Fibrillation (AF)
In patients with atrial fibrillation (AF), the heart sounds that can be heard are typically irregular and may vary from one patient to another. The following are some key points to consider:
- The first heart sound (S1) may be variable in intensity and timing due to the irregular atrial contractions 2.
- The second heart sound (S2) is usually normal, but may be followed by an irregular interval before the next S1 3.
- An irregularly irregular rhythm is often heard, with no discernible P waves on the electrocardiogram (ECG) 4.
- The intensity and character of the heart sounds may vary depending on the ventricular response rate and the presence of any underlying heart disease 5.
- The use of machine learning algorithms and visualization tools, such as the regularogram (RGG), can help identify and quantify irregular heart rate irregularities, which can aid in the detection of AF episodes 6.
Clinical Implications
The clinical implications of these heart sounds in AF patients are significant, as they can impact diagnosis, treatment, and outcomes. For example:
- Accurate diagnosis of AF is crucial to prevent stroke and other complications 3.
- The presence of irregular heart sounds can guide treatment decisions, such as the use of anticoagulation therapy or cardioversion 4.
- The characterization of AF burden and its impact on heart sounds can inform patient management and prognosis 5.
- The development of new technologies and tools, such as machine learning algorithms and visualization tools, can improve the detection and management of AF 6.