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Impact of Atrial Fibrillation on Right Ventricular Diastolic Function in Heart Failure with Preserved Ejection Fraction: A Case Report

Heart failure with preserved ejection fraction (HFpEF) accounts for almost half of all heart failure cases and its clinical outcomes remain poor due to its heterogeneity. Atrial fibrillation (AF) plays a role in the pathophysiology of HFpEF and rhythm control in AF can improve left ventricular diastolic function; however, the relationship between AF and right ventricular diastolic function has not been fully examined in HFpEF. In this case report, we present a 72-year-old woman who developed HFpEF complicated by AF and less-distensible right ventricle. AF was associated with reversible impairment of RV diastolic function in this case.


Introduction
Heart failure with preserved ejection fraction (HFpEF) accounts for almost half of all heart failure cases and its clinical outcomes remain poor due to its heterogeneity [1,2]. Recently, attention has been paid to right ventricular (RV) dysfunction, which is associated with the severity of HFpEF [3,4]. Atrial fibrillation (AF) also plays a role in the pathophysiology of HFpEF and rhythm control in AF can improve left ventricular (LV) diastolic function [5]; however, the relationship between AF and RV diastolic function, especially RV distensibility, has not been fully examined in HFpEF. Recently, we reported that the prevalence of less-distensible right ventricle increases with age, and that RV dysfunction is associated with the clinical outcomes of HFpEF [4,6].

Case Report
A 72-year-old female presented with dyspnea during exercise and at rest, marked leg edema, weight gain of approximately 5 kg, and tachycardia associated with pleural effusion and lung congestion ( Figure 1A). AF tachycardia was observed on her electrocardiogram ( Figure 1B) and initial echocardiography assessment at emergency department demonstrated preserved left ventricular ejection fraction (LV ejection fraction 56%) ( Figure   1C). She was diagnosed with acute decompensated heart failure due to heart failure with preserved ejection fraction (HFpEF) and atrial fibrillation (AF), and admitted to the high care unit (HCU). She was managed in the HCU with furosemide and nitroglycerin infusion, and non-invasive positive pressure ventilation. Two days after admission, bisoprolol (1.25 mg/day) was started to control the heart rate. She gradually recovered and no longer required medication or respiratory support. On day 4 of admission, detailed echocardiography was performed. The LV septal e' ( Figure 1D) and elevated mitral E/e' ratio were 6.9 cm/s and 13, respectively. Moderate and severe valvular stenosis and regurgitation were not observed on echocardiography. Her RV systolic pressure was 35 mmHg; however, other RV function was unable to be assessed by echocardiography due to complex RV anatomy and jugular venous pulse was instead examined. Her jugular venous pulse waveform was indicative of dominant 'Y' descent deeper than the 'X' descent, a sign of less-distensible right ventricle ( Figure 1E); however, signs of constrictive pericarditis, such as septal bounce and mitral inflow variation with respiration and cardiac amyloidosis, such as granular sparkling echoes, were not observed on echocardiography. The brain natriuretic peptide (BNP) was 462 pg/ml. On day 5 of admission, she underwent coronary CT angiography, but neither significant coronary artery stenosis nor pericardial calcification was observed, and there was no thickness on CT ( Figure 1F).
Time-dependent changes in chest X-ray, mitral inflow of echocardiography, and jugular venous pulse are shown in

Discussion
The impact of AF on LV diastolic function has been examined in patients with HFpEF. AF affects LV diastolic function and catheter ablation can improve LV diastolic function by maintaining the sinus rhythm [5]. Recently, RV, but not LV, dysfunction was reported to be related to the clinical outcomes of patients with HFpEF [4,7]; however, the relationship between RV diastolic function and AF in patients with HFpEF has not been examined in detail.
Although assessment of RV diastolic function is needed to clarify the relationship between less-distensible right ventricle and AF, echocardiographic quantitative assessment of RV function is often difficult due to the complex RV anatomy [8]. Instead of echocardiographic assessment, the jugular venous pulse was used to evaluate the RV diastolic function in this case. The jugular venous pulse is an outdated method for qualitative assessment, but its waveform can inform whether RV diastolic function is impaired and the preload reserve is limited [9][10][11].
In general, pattern of less-distensible right ventricle, dominant 'Y' descent deeper than the 'X' descent, can be seen in constrictive pericarditis and/or amyloidosis, which limits the preload reserve for the right ventricle, and this sign remains unchanged unless specific therapy for these diseases is performed. Why was RV distensiblity impaired in this case? Although subclinical amyloidosis, such as wild-type transthyretin amyloidosis, may be underdiagnosed [12], constrictive pericarditis and overt amyloidosis were not suggested by echocardiographic examination or CT scan. RV diastolic function is usually influenced by age-related change of the myocardium, increased RV afterload, and/or diastolic ventricular interaction [6,13,14]. The patient was 72-years-old, had increase in RV systolic pressure, and high LV filling pressure suggested by increase in mitral E/e' ratio. The role of late diastolic ventricular filling in the stroke volume depends on the severity of ventricular distensibility.
Non-distensible ventricle, such as constrictive pericarditis, has no filling fraction after the rapid filling period and atrial kick becomes meaningless [15]. On the other hand, less-distensible ventricle, such as restrictive cardiomyopathy, has a modest filling fraction, but definite slow filling and atrial contraction periods [10]. Indeed, the A wave in the jugular venous pulse and mitral inflow were observed and the BNP level improved under sinus rhythm in this case. Thus, atrial contraction plays an important role in maintaining the stroke volume and AF is a therapeutic target for this patient with HFpEF.

Conclusion
AF was associated with reversible impairment of RV diastolic function in this case. Rhythm control in AF may play an important role in preventing deterioration in some HFpEF patients.

Conflicts of Interest
There are no conflicts of interest to declare.