Cardiovascular Journal of Africa: Vol 26 No 3 (May/June 2015)

CARDIOVASCULAR JOURNAL OF AFRICA • Volume 26, No 3, May/June 2015

112

AFRICA

Discussion

The results of this study indicate that the presence of NAFLD

was associated with impaired RV diastolic function (RVDF).

In addition, the evidence showed that the existence of NAFLD

was related to the extent of impairment in RVDF. NAFLD is

more common in patients with impaired RVDF, obesity, insulin

resistance, hypertension, hyperlipidaemia, coronary artery

disease, obstructive sleep apnoea syndrome, oxidative stress,

endothelial dysfunction and the metabolic syndrome.

In this study, although RVDF was impaired, systolic function

was preserved in NAFLD patients. Furthermore, HS grade was

positively correlated with RV MPI. Several studies reported only

diastolic left ventricular dysfunction, while others reported both

diastolic and systolic left ventricular functional impairment in

NAFLD patients with hypertension, insulin resistance, type 2

diabetes and/or the metabolic syndrome.

18-20

Evaluating the possible influence and correlation of metabolic,

cardiovascular and liver biopsy parameters on cardiac left

ventricular dysfunction, we found a positive correlation between

left ventricular parameters and severity of liver damage (NAS

score).

However, to the best of our knowledge, to date, no study

has explored the involvement of right ventricular systolic and

diastolic function and its relationship with HS grade in NAFLD

patients.

We speculated that the excessive lipid accumulation in

hepatocytes that is a characteristic of NAFLD can lead to

lipid deposition in cardiac myocytes, promoting RVDF. In

addition, our study showed that significantly impaired RVDF

was associated with HS grade in NAFLD according to TDI.

However, we could not detect any significant difference in

tricuspid lateral annulus systolic velocity between the NAFLD

patients and controls. Therefore, right ventricular systolic

function was not impaired in patients with NAFLD.

MPI is a DTI-derived quantitative parameter used frequently

in recent years to grade systolic and diastolic function. This

index was first described by Tei

et al

and is widely accepted

because it correlates with more invasive measurements, is easy

to reproduce and is easy to perform. In coronary artery disease,

a prolonged MPI is an important disease precursor observed

before the development of systolic dysfunction.

A markedly

prolonged MPI despite an unchanged tricuspid lateral annulus

systolic velocity in NAFLD patients compared with the control

group is compatible with the hypothesis that prolonged MPI

stems from RVDD. In fact, RVDF deteriorates in NAFLD, and

this deterioration is associated with grade of HS.

There were some limitations to our study. The first was the

small sample size. The second was that the diagnostic method

depended on USG, and the exclusion of other secondary

causes of chronic liver disease was not confirmed by liver

biopsy. Although liver biopsy is currently the gold standard

for distinguishing NAFLD forms, for assessing the severity of

damage and prognosis, NAFLD can be detected as a bright

liver on USG, which is possible to perform routinely. Moreover,

liver USG has proven to be a sensitive, accurate and convenient

diagnostic tool in detecting steatosis. Its sensitivity ranges from

60 to 94% and its specificity from 84 to 95%.

15,23

Conclusion

We found that there was significant impairment in diastolic

function in non-diabetic and normotensive NAFLD patients

compared to the controls. It should be kept in mind that diastolic

function may be impaired while systolic function is preserved in

NAFLD patients. We suggest that patients with NAFLD require

aggressive cardiac risk-factor modification and closer follow up

for the prevention of diastolic and systolic heart failure.

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Table 5. Correlations between grade of hepatosteatosis

and echocardiographic parameters

Parameters

-value

0.020

0.886

Ea/Aa

–0.156

0.260

IVRT*

0.295

0.03

MPI*

0.641

0.001

*By hepatosteatosis, IVRT: isovolumetric relaxation time, MPI: right

ventricular myocardial performance index, HS: hepatosteatosis.