State-of-the-Art Review
Functional Regurgitation of Atrioventricular Valves and Atrial Fibrillation: An Elusive Pathophysiological Link Deserving Further Attention

https://doi.org/10.1016/j.echo.2019.08.016Get rights and content

Highlights

  • Atrial fibrillation is associated with functional tricuspid and/or mitral regurgitation.

  • Dilatation of the annulus is the key mechanism of functional regurgitation.

  • 3DE is key for assessing mechanisms of atriogenic functional regurgitation.

  • Understanding this entity may have important implications for its treatment.

In patients with structurally normal atrioventricular valvular apparatus, functional regurgitation of the mitral or tricuspid valves has been attributed mainly to ventricular dilation and/or dysfunction, through a combination of annulus dilation and tethering of the valve leaflets. The occurrence of functional regurgitation of atrioventricular valves in patients with long-standing persistent atrial fibrillation and atrial dilation but normal ventricular size and function has received much less attention, and its peculiar mechanisms still remain to be understood. This distinct form of functional regurgitation (i.e., “atrial functional regurgitation”) may require different treatment and interventional repair approaches than the classical functional regurgitation due to ventricular dilatation and dysfunction (“ventricular functional regurgitation”), and current guideline recommendations do not yet address this distinction. Clarifying the differences in the pathophysiology of atrial functional regurgitation and its management implications is of paramount importance. This review describes briefly the comparative anatomy of mitral and tricuspid apparatus and the pathophysiology and typical echocardiographic features of atrial functional regurgitation compared with ventricular functional regurgitation, as well as the added value of three-dimensional echocardiography as an essential imaging tool to clarify the mechanisms involved in its development.

Section snippets

Comparative Anatomy of the Mitral and Tricuspid Valvular Apparatus

The AV valvular apparatus comprises several components: leaflets, their annular attachment at the AV junction, chordae tendineae, papillary muscles, ventricular, and atrial walls8 (Figure 1, Figure 2, Figure 3). The structural integrity and the complex mechanistic interplay of all these components are pivotal to preserve AV valve competence. Compared with the MV apparatus, a significant anatomic variability of the TV leaflets, chordae, and papillary muscles9, 10, 11 has been described. The

Pathophysiology of Ventricular Functional and Atrial Functional Mitral Regurgitation

VF-MR has been described as the result of an imbalance between increased tethering forces (secondary to global and/or regional LV dilation and papillary muscle displacement) and decreased closing forces (impaired LV contractility and/or dyssynchrony).2, 3 Normally, a low LV pressure is required to close the thin MV leaflets and VF-MR is generally not produced by LV dysfunction alone (without LV dilation). In patients with ischemic or dilated cardiomyopathy, as a consequence of LV geometric

Pathophysiology of Ventricular Functional and Atrial Functional Tricuspid Regurgitation

The pathophysiology of VF-tricuspid regurgitation (TR) shares many similarities with VF-MR and involves the same three mechanisms described above, which contribute to its development and severity by different extents depending on the etiology: (1) distortion of the spatial relationships between leaflets, chordae, and papillary muscles leading to leaflet tethering and malcoaptation; (2) dilatation of the TA; (3) changes of TA geometry and dynamics. As with the LV, various cardiac conditions

Role of Two-Dimensional and Doppler Echocardiography for Assessing Functional Regurgitation

The main echocardiographic features that may help differentiate atrial from ventricular functional regurgitation are presented in Figure 8. As opposed to ventricular functional regurgitation, in patients with atrial functional-MR and atrial functional-TR the ventricles have generally normal geometry and ejection fraction, although longitudinal strain analysis might detect subtle myocardial dysfunction41 (Figures 9 and 10). In advanced stages, reactive ventricular dilation due to increased

Role of 3DE

An important aspect for the differential diagnosis between atrial and ventricular functional regurgitation is the accurate quantification of ventricular size. It is well known that 2DE measurements might underestimate the size of LV,56, 59, 60 with potential risk of misclassification of VF-MR as atrial functional-MR. In atrial functional-TR, as the RV assumes a triangular shape with dilation confined to the inflow basal region, it may erroneously appear enlarged if quantified by RV basal

Clinical Implications of Atrial Functional Regurgitation

Significant atrial functional-MR is present in 4%-8% of AF patients,40, 78 and its prevalence may increase to 28% in patients with lone AF > 10 years.79 Significant atrial functional-TR is also frequent, representing 25% of patients with lone AF > 10 years.79 Combined atrial functional-MR and atrial functional-TR have been associated with worse prognosis,79 but no studies addressing its burden in the general population and specific treatment strategies have been conducted so far. Considering

Conclusion

The pathophysiology of atrial functional regurgitation due to AF involves the interplay between atrial dilatation, loss of atrial contraction, and annulus remodeling. Three-dimensional echocardiography imaging is particularly helpful in understanding the complex anatomy and function of AV valves in the beating heart and has provided unique mechanistic insights that help to discriminate the pathophysiology of atrial from ventricular functional regurgitation. In light of recent evidence regarding

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    Drs. Muraru and Guta contributed equally to this article.

    Dr. Guta has received a research grant from the Romanian Society of Cardiology.

    Conflicts of Interest: None.

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