Echocardiographic assessment of Diastolic Function in patients with Atrial Fibrillation

Background and Aims: Echocardiographic assessment of left ventricular diastolic function in patients with atrial fibrillation is a challenge as loss of atrial kick (A wave), beat to beat variability and left atrium enlargement despite normal atrial pressure make usual guideline based estimation difficult and inaccurate. Hence adoption of additional echocardiography parameters are necessary which are tricky and have varied results. Hence the aim of this study was to study various aspects of diastolic function in patients with atrial fibrillation. Methods: It was a hospital based prospective cross-sectional observational study conducted at cardiology unit, National Academy of Medical Sciences, Kathmandu and Shahid Gangalal National Heart Center, Kathmandu from 1st July 2018 to 30th June 2019. Results: Total of 92 patients were studied. About one third (34.8%) had diastolic dysfunction. Ratio of E/e’(14.65 ± 2.21 Vs 7.66 ± 1.18) , E/Vp (1.57 ± 0.14 Vs 1.20 ± 0.11), isovolumetric relaxation time (53.06 ± 13.82ms Vs 89.33 ± 9.88ms) and deceleration time of pulmonary venous diastolic wave (203.09 ± 26.13ms Vs 292.25 ± 36.32ms) were significantly different in patients with diastolic dysfunction compared to patients without diastolic dysfunction with sensitivity of 90.6%, 84.4%, 81.2% and 78.1% respectively. Conclusion: Diastolic dysfunction is a common entity in patients with atrial fibrillation. Echocardiography parameters like E/e’ ratio, isovolumetric relaxation time, E/Vp ratio and deceleration time of diastolic pulmonary wave were highly sensitive in detection of diastolic dysfunction.


Introduction Abstract
Diastole is an input phase of heart 1 comprising of four stages i.e, iso-volumetric relaxation, rapid diastolic filling, diastasis, and atrial systole. 2,3 and diastolic dysfunction is defined as a continuum from isolated diastolic dysfunction to impaired relaxation with normal filling pressures to impaired filling (restrictive filling) with extremely elevated filling pressures 4,5 . In patient with Atrial Fibrillation (AF), assessment of diastolic function is a challenge as loss of organised atrial activity in AF vanishes mitral inflow A-wave. Loss of A-wave makes calculation of diastolic function by mitral inflow E/A ratio impossible. Simulataneously, beat to beat variation producing cycle length variability in atrial fibrillation warrants multiple measurements for accuracy. Therefore, an average of 5-10 beats or 3 consequitive beats calculations should be done. Meanwhile, in many instances patients with AF have left atrial enlargement irrespective of elevated filling pressure thus making measurement of various left atrial indices for diastolic function assessment partially incorrect. Thereupon, derivation of diastolic function in patients with AF should utilize all these secondary and/ or additional echocardiography paramaeters 1 .
However, there are many limitations to echocardiography @ Nepalese Heart Journal. Nepalese Heart Journal retain copyright and works is simultaneously licensed under Creative Commons Attribution License CC -By 4.0 that allows others to share the work with an acknowledge of the work's authorship and initial publication in this journal Hence echocardiography derivation of LV diastolic function in patients with AF is tedious and tricky disabling us to use protocol based approach. In addition, not much similar studies are performed in our context. Thus rationale for this study is to justify effective echocardiography parameters to assess diastolic function. The objective of the study was to study various aspects of daistolic function in patients with atrial fibrillation.
It was a hospital based prospective cross-sectional observational study conducted at cardiology unit, National Academy of Medical Sciences (NAMS), Kathmandu and department of cardiology, Shahid Gangalal National Heart Center (SGNHC), Kathmandu, Nepal from 1 st July 2018 to 30 th June 2019 (1 year). A total of 92 patients were included in the study. Sample calculation was based on following equation: Sample calculation:

Methods
All consecutive patients attending above mentioned places of study based on inclusion criteria and during period of study were enrolled. Detail clinical history, past medical/surgical history, general physical examination, systemic evaluation, Chest X-ray (CXR), Electrocardiography (ECG), necessary laboratory investigations and 2D Trans Thoracic Echocardiography were recorded over working proforma. The working proforma was validated by subject committee, National Academy of Medical Sciences. American Society of Echocardiography (ASE) guidelines based estimation of echocardiography parameters were accomplished 8 . Diastolic echocardiography parameters were also obtained as per ASE guidelines 5 . Diastolic dysfunction was labeled when three of more of the four given echocardiography parameters (cutoff values) were obtained from a single patient.
Formal permission for study was taken from subject committee, National Academy of Medical Science (NAMS). Written informed consent was taken from patient or their attendants.
Data were entered into work sheet (Microsoft Excel) and statistical analysis was done using IBM Statistical Package for Social Science (SPSS) software, version 20. Continuous variables were listed as mean ± standard deviation and categorical variables were presented as number or percentage. After processing of all available information, statistical analysis of their significance was done. Chi square test assessed statistical significance between clinical parameters in those patients with and without diastolic dysfunction. Confidence Interval (CI) of 95% and value of P < 0.05 were considered significant.
Nepalese Heart Journal 2019; Vol 16 (2), [17][18][19][20][21] Echocardiograhic assessment of Diastolic Function in patients with Atrial Fibrillation calculation of diastolic function. No single index yield robust criteria and thus multiple indices are required to increase the sensitivity of diagnosis 6 . Moreover, diastolic function is related to myocardial relaxation and passive LV properties and is modulated by myocardial contractility. Myocardial relaxation on the other hand is determined by load, inactivation and non-uniformity 5 . Hence, all these parameters of assessment are skewed with various situations like mitral valvular/ annular pathology, loading conditions including atrial fibrillation and systolic dysfuction including wall motion abnormality.
Current American Society of Echocardiography (ASE) guidelines focus on the following parameters for assessment of diastolic function in patients with AF 5 . Pacemaker/ICD/ CRT in situ 5.
Past h/o radio frequency ablation for atrial fibrillation 6.
Previous Left atrial/ atrial appendage or mitral valve re pair or cardiac surgery 7.
Wall motion abnormality

Discussion
Patients with diastolic dysfunction were slightly elderly and atherosclerotic risk factors have no clinical significant association in patient with left ventricular diastolic dysfunction ( Table 2).
All the echocardiography diastolic parameters used during the study had high sensitivity with highest being E/e' ratio ( The participants of this study were mostly in late adulthood (mean age of 61.07± 10.89 years) and about one third of the patient had diastolic dysfunction. Additionally, patient having diastolic dysfunction were slightly elder than those without diastolic dysfunction revealing the fact that age of the patients play a vital role in prevalence of diastolic dysfunction. Similar findings were observed in different studies done by various authors 7,9 . A study done by Kosiuk J, et al found the prevalence of left ventricular diastolic dysfunction to be 38% 9 . As age is one of the main determinants for atrial fibrillation and diastolic dysfunction separately, elderly people are prone for both these abnormalities. Age related collagen deposition in the myocardium brings the physiological increase in filling pressure of the left ventricle. This results in increase in tendency for atrial fibrillation as well as dysregulation of diastolic function 7,10 .
Various echocardiography parameters assess diastolic function of the heart that includes transmitral flow velocity, pulmonary venous flow velocity, mitral annular velocity, flow propagation velocity, left atrial size, strain, strain rate, and twist. However, clinically all of these parameters may not be feasible as in case of atrial fibrillation. 1 Hence only a few echocardiography parameters were used.
This study showed that the ratio of E/e' in patients with diastolic dysfunction was significantly higher (14.65 ± 2.21) compared to those without diastolic dysfunction (7.66 ± 1.18) and E/e' ration was highly sensitive in discriminating diastolic dysfunction. Many studies had documented similar findings. Kusunose K et al. in their research stated that single beat E/e' ≥11.0 obtained by dual doppler echocardiography in patients with atrial fibrillation with preserved systolic function could predict diastolic dysfunction with elevated filling pressure sensitivity of 90% 11 . Sohn et al. in their study reported that an increase in E/e' ratio (≥11.0) was present in patient with diastolic dysfunction and this could also predict elevated left ventricular filling pressure apart from diastolic dysfunction with a sensitivity of 75% 12 .
Iso-Volumetric Relaxation Time (IVRT) in patients with diastolic dysfunction was found to be 53.06 ± 13.82ms in this study and this parameter had a moderate sensitivity of 81.2%. Literatures have shown that IVRT measured with use of continuous wave doppler can be used in patients with atrial fibrillation and is inversely proportional to left atrial pressure 13 . In a study done by Nagueh SR and team, IVRT inversely correlated well with LV filling pressure in patients with atrial fibrillation 14 . Study done by Abudiab MM, et al depicted that IVRT had moderate sensitivity of 81% for high predicting diastolic dysfunction with raised filing pressure 15 .
The ratio of E/Vp in this study in patient with diastolic dysfunction was found to be significantly higher (1.57 ± 0.14 Vs 1.20 ± 0.11) compared to those without diastolic dysfunction with a moderate specificity of 84.4%. Various researches have justified that slope Nepalese Heart Journal 2019; Vol 16 (2), [17][18][19][20][21] Echocardiograhic assessment of Diastolic Function in patients with Atrial Fibrillation