DISCUSSION
DISCUSSION:
Left ventricular systolic dysfunction in HIV infection can be asymptomatic or symptomatic101.Subclinical abnormalities of left ventricular dysfunction detected by echocardiography have been reported in treatment-nạve HIV-positive patients. Studies done in Portugal9, Congo8, and Zimbabwe35 as well as in Nigeria38 have reported cases of left ventricular systolic and diastolic dysfunction in treatment-nạve HIV-positive patients who had no prior history or symptom suggestive of underlining cardiac disease.
Symptomatic Left Ventricular Systolic Dysfunction
The presentation of left ventricular systolic dysfunction in HIV infected patients is generally in form of left sided heart failure. Moreover, a clinical diagnosis of left ventricular systolic dysfunction may be difficult in HIV-infected patients due to masking of symptoms by concomitant bronchopulmonary disease and/or wasting disease especially in more advanced stages of HIV infection. However, adhering to Framingham's criteria of diagnosis of heart failure102 makes the diagnosis easier in patients with HIV infection. Symptoms and signs of left ventricular dysfunction includes productive cough, orthopnoea, paroxysmal nocturnal dyspnoea, weak or thready pulse, tachycardia, narrow pulse-pressure, displaced apex, presence of third heart sound and rales on chest auscultation.
Asymptomatic Left Ventricular Systolic Dysfunction
These patients by definition have no symptom as well as no clear physical sign of left ventricular systolic dysfunction. However, the depressed ejection fraction on echocardiography, usually gives
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out the diagnosis. It is widely accepted that an individual may progress through an asymptomatic phase of left ventricular dysfunction to symptomatic state. Asymptomatic left ventricular
dysfunction is now a well recognized clinical entity and is currently included in the ACC/AHA staging System103.
Clinical features of left ventricular diastolic dysfunction
There are minimal differences between the clinical features of left ventricular systolic and diastolic dysfunction. However, echocardiography104 assessment of left ventricular ejection fraction and Doppler studies reliably distinguishes the two.
Echocardiography Features of Left Ventricular Systolic Dysfunction
Echocardiography is a very useful non-invasive, radiation-free imaging technique that provides immediate assessment of structure and function of the heart. It has also been recommended for use in clinical trials104. Echocardiography has become an important investigating tool in the diagnosis of cardiac lesions in HIV/AIDS. Evaluation of left ventricular systolic function using echocardiography includes estimation of the following parameters:
Left ventricular chamber dimension.
Left ventricular fractional shortening.
Left ventricular ejection fraction.
Left ventricular chamber dimension
Cardiac function can be determined from chamber quantification with M-mode and two-dimensional echocardiography.
Left Ventricular Ejection Fraction
The most commonly used index to assess left ventricular systolic function is the left ventricular
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ejection fraction, which is commonly calculated by echocardiogram machine, using derived volumes by Teichholz105 formulabased on M-mode left ventricular dimensions.
LV volume =7/ (LVID + 2.4) × (LVlD)3.
The above equation compensates for ventricles of abnormal size as against cubed formula, but its accuracy is limited in patients with regional wall motion abnormality.
The left ventricular ejection fraction (LVEF) can also be calculated using the cubed formula as shown below.
LVEF (%) =(LVDd)3 - (LVDs)3 × 100 (LVDd)3
Left Ventricular Fractional Shortening
Left ventricular fractional shortening is used as an index of left ventricular systolic function.
Left ventricular fractional shortening (LVFS) is calculated from left ventricular internal dimension in systole and diastole using the formula below106.
LVFS (%) = LVDd - LVDs x 100 LVDd
Left ventricular systolic dysfunction was defined in a study by Longo-Mbenza et al8 as EF <
50% and FS < 28%.
Evaluation of Left Ventricular Structure
Left ventricular mass, left ventricular mass index and relative wall thickness are estimated using the formula.
Left Ventricular Mass107.
Left ventricular mass = 0.8 [1.04 (IVSd + LVIDd + PWTd )3 - LVIDd3)] + 0.6g.
Where LVIDd: Left ventricular internal diameter in diastole; IVSd: Inter ventricular septum diameter in diastole; LVPW: End diastolic left ventricular posterior wall thickness.
26 Left Ventricular Mass Index
Left ventricular mass index (LVMI) = LVM / BSA
• BSA (Body surface area) is derived from the Mosteller equation108, using the formula below BSA (m2) = [Height (cm) x weight (kg) / (3600)1/2.
Left ventricular hypertrophy was considered, with LV mass index greater than 125 g/m 2 for men and 110 g/m 2 for women in a study by Unwanurochi99.
Relative Wall Thickness
Relative wall thickness is calculated using the formula below109.
Relative wall thickness (RWT) = 2 x end-diastolic posterior wall thickness Left ventricular end-diastolic diameter
Increase relative wall thickness was considered, with RWT > 0.43 in a study by Koren et al109. Echocardiography Features of Diastolic Dysfunction in HIV Infection
Left ventricular diastolic dysfunction occurs as a result of impaired left ventricle filling, which depends on left ventricular relaxation and compliance. In HIV infection, left ventricular diastolic dysfunction may precede left ventricular systolic dysfunction110. Diastolic dysfunction can be evaluated by Doppler echocardiography. Criteria to diagnose left ventricular diastolic dysfunction remain imprecise; however, an algorithm has been developed. This algorithm comprises of combinations of multiple echocardiography parameters, which have been proposed as sufficiently sensitive and specific, including mitral inflow velocity pattern, isovolumic relaxation time, deceleration time, reversal of E-A, pulmonary vein flow pattern, tissue Doppler measurement and the M- mode echocardiography measurement of the left atria size.
There are four basic echocardiography patterns of left ventricular diastolic dysfunction, which are graded one to four 111. The mildest form is called abnormal relaxation pattern or grade I
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diastolic dysfunction. Grade I diastolic dysfunction is seen on mitral inflow Doppler echocardiogram as a reversal of normal E/A ratio. This pattern may develop normally with age in some patients, and many grade I patients usually do not have any clinical sign or symptoms of heart failure.
Grade II diastolic dysfunction is called pseudo normal filling dynamic. This is considered as moderate diastolic dysfunction that is associated with elevated left atria filling pressure.
Individual with this form of diastolic dysfunction, more commonly have symptoms of heart failure and may have left atria enlargement due to elevated pressure in left heart. Grade III &
IV diastolic dysfunctions are called restrictive filling dynamic and are both severe forms of diastolic dysfunction and individual with this types of diastolic dysfunction, tends to have advance heart failure.
Left ventricular diastolic dysfunction is usually diagnosed in the presence of any of the following criteria111:
1. Impaired relaxation with an E/A ratio < 1, impaired ventricular relaxation time (IVRT)
> 100ms and deceleration time (DT) > 220ms.
2. Pseudo normalization resembling the normal configuration with respect to mitral inflow, but with normal or low deceleration time (DT).
3. Restrictive pattern with E/A ratio > 2, IVRT < 70ms and DT < 160ms.