Left Atrial Function and Coronary Slow Flow: Is There Diastolic Dysfunction or Not?

Dear Sir,

I read with a great interest the article published by Dr. Fallah et al. in this journal about the role of two-dimensional (2D) speckle-tracking echocardiography (STE) longitudinal strain in the assessment of atrial function in patients with coronary slow flow (CSF).[1] Authors investigated the presence of diastolic dysfunction in a cohort of patients who did not show left ventricular (LV) systolic alterations, comparing atrial function with a control group of normal individuals. The choice of using 2D STE analysis for the assessment of atrial function is valuable. Being born for the evaluation of LV systolic contraction and having showed a great diagnostic and prognostic relevance in several clinical settings,[234] longitudinal strain was then successfully used for the analysis of other chambers, including right ventricle, aorta, and left atrium (LA).[56] Particularly, LA longitudinal strain showed to be able to provide additional information about LV diastolic function compared with conventional parameters and to be more sensitive than the currently suggested algorithm[7] in the detection of increased LV filling pressure.[5]

In the manuscript just published, Fallah et al.[1] reported that they did not find a significant impairment of strain and strain-rate parameters in their population and that all the three phases of atrial cycle, i.e., reservoir, conduit, and pump function, resulted to be similar to those of controls. Accordingly, the authors stated that their patients had a normal diastolic function or that the increase of LV filling pressure was so subtle that strain analysis was not able to detect it.

These conclusions are of great interest. Indeed, as the same authors reported in the discussion section, different results had been obtained before by other research groups in the same kind of patients,[891011] who found an impaired diastolic function in patients with CSF, assessed with conventional parameters and with 2D STE analysis. Particularly, Wang et al.[8] performed the evaluation of atrial function using the same measurements Fallah et al. used and found a significant impairment of reservoir and conduit phases and an increased role of the atrial contraction in the LV filling, the latter a well-known marker of an early increase of LV filling pressure. These results seem to be in line with the findings reported by Sezgin et al.[10] and Suner and Cetin[11] who found a reduced LV diastolic function and a normal systolic function. Of course, Fallah et al.[1] provided some interesting hypotheses to explain the different results obtained by Wang et al. Indeed, while the statement that diastolic dysfunction was too subtle to be detected by 2D analysis seems to be weak, since that other authors[91011] were able to assess it using conventional parameters that are less sensitive than strain analysis,[5] and the relevance of systolic function influence on the diastolic parameters seems not to be confirmed in the previous studies,[1011] the possibility of an underestimation of the confounding role of comorbidities such as diabetes and hypertension in the other reports cannot be excluded.

In my opinion, the presence or not of diastolic dysfunction in these patients is an issue of significant relevance. First of all, it is well known that diastolic dysfunction is associated with the development of heart failure and is predictive of all-cause mortality.[12] Second, the presence/absence of diastolic dysfunction could contribute to better elucidate CSF pathophysiology that is not completely clear so far. Finally, the presence or not of diastolic dysfunction plays an important role in the therapeutic management of these patients: indeed, they are usually treated with ranolazine or nitrate to reduce symptoms, but rarely, drugs for the improvement of diastolic function are prescribed; if the presence of a subtle LV filling pressure increase would be confirmed, it could be early properly treated, improving patients’ quality of life and preventing the progression to advanced stages.

Accordingly, the interesting results reported by Fallah et al. need a further confirmation by larger studies that should use the most sensitive parameters for the assessment of LV filling pressure such as LA strain and strain rate and in the same time should take into account the confounding influence of comorbidities and systolic function on diastolic parameters.

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