A T.E., U D.I., O J.O.
diastolic function., heart failure, left ventricular ejection fraction, systolic function, tei index
A T.E., U D.I., O J.O.. Usefulness Of Tei Index In Patients With Heart Failure. The Internet Journal of Internal Medicine. 2009 Volume 9 Number 1.
Tei index (TI) also referred to as myocardial performance index is defined as the sum of isovolumic ventricular contraction time (IVCT) and isovolumic ventricular relaxation time (IVRT) divided by ejection time (ET)1,2. It is a Doppler derived unit-less index and is a measure of combined systolic and diastolic myocardial performance¹ of the left ventricle (LV) or right ventricle (RV)1,3. Heart failure (HF) is a final common pathway for diseases of diverse aetiologies4. In Africa, at least 3-7% of all hospital admissions are caused by HF5.The overall prevalence of HF is thought to be increasing in the developed world6. Little is known with respect to the prevalence or risk of developing HF in the developing world because of a paucity of population–based studies7. The two important cardiac functions are systolic and diastolic functions of which the leading non-invasive technique for evaluation is echocardiography8 and its findings are known to influence management decisions and outcomes9. There are many limitations to the use of classical echocardiographic indices for the estimation of systolic and diastolic left ventricular (LV) function10. The ejection fraction (EF), an index of systolic function, and LV volumes are subject to large errors when the ellipsoid shape of the heart becomes spherical10. Age, rhythm and conduction disturbances and changes in loading all affect the Doppler signal of transmitral flow which is the most commonly used method10. The characteristics of the Tei index such as its feasibility, ease of use, less dependence on operator, geometry, heart rate, preload, afterload and excellent separation of clinical groups, as well as strong relation of outcome in patients in HF2, 11, 12 enhance its (Tei index) appeal for study in this part of the world with limited resources. This study aimed at determining the Tei index in patients with HF and matched normal controls. It also assessed if there was any significant difference in Tei index with severity of HF and if there was any relationship between Tei index and ejection fraction.
Diagnosis of HF was made using Framingham criteria13,17 for definitive HF. New York Heart Association (NYHA) classes were determined on admission. Anthropometric measurements included height, weight, waist circumference, body mass index. Peripheral arterial pulses were assessed and blood pressures were measured on admission18,19.
Chest radiograph (postero-anterior view) was done at the radiology department to assess the cardiac silhouettes, aorta and the lung fields.
A conventional resting 12–lead electrocardiography was performed with Cardiofax ECG – 9620 model machines. Lead II was recorded for a long rhythm strip. The recommendation of the American Heart Association (AHA)20 concerning standardization of leads and specification for instrument was followed.
Two-dimensional (2–D), motion mode (M–mode) and Doppler studies were performed with transthoracic echocardiography using Siemens Sonoline G60S ultrasound imaging system with P4–2 transducer. Measurements were in accordance with the recommendations of the American Society of Echocardiography21 with leading edge to leading edge recordings taken.
Calculations were made using the internal analysis software of the echocardiographic device. The 2–D views were used for real time morphological characteristics and also as a reference for the selection of the M–mode beam. The echo views utilized for the study included parasternal long axis view, short axis view, apical 4-chamber, and apical 5-chamber. Pulsed
The TI was calculated from the ratio of time intervals expressed by the formula a-b/b or IVCT + IVRT/ET¹º as shown in fig 110 below. Measurements were taken from three consecutive beats and averaged. The parameters for the formula were determined by first locating the sample volume at the tips of the mitral valve leaflets in the apical 4-chamber view which enabled the measurement of ‘a’ (the time interval between the end and the start of transmitral flow). The sample volume was then located in the LV out flow tract, just below the aortic valve (apical 5-chamber view) for the measurement of ‘b’ (LV ejection time). The interval ‘a’ included isovolumic contraction time (IVCT)), the ejection time, (ET) and the isovolumic relaxation time.
Data obtained were analyzed with a statistical computer software package (SPSS version 17.0). Continuous variables were expressed as means ± standard deviation, and categorical variables as percentages. The chi-square test was used to determine the statistical significance of associations between categorical variables while student t-test was used to determine the difference between two means. A p-value of less than or equal to 0.05 was considered significant.
The study population comprised 44(48.9%) male patients with HF and 40(44.4%) male control subjects. There were 46 (51.1%) females with HF and 50 (55.6%) female controls. There was no statistically significant difference between patients and controls (p = 0.531). The mean ages of the HF patients and control subjects were 56 ± 18.57 years and 57 ± 18.66 years respectively (p = 0.762). The ages ranged from 22 to 88 years for patients versus 23 to 88 years for control subjects. There was no statistically significant difference between patients and controls (p = 0.072).Seven disease conditions were identified as causes of HF in the patients studied. The commonest cause of HF was systemic hypertension accounting for over 60% of cases followed by dilated cardiomyopathy, rheumatic heart disease, renal failure, congenital heart disease, endomyocardial fibrosis, and ischaemic heart disease in decreasing order (table 1). As shown in table 2, majority of patients (51%) in heart failure recruited for this study presented in NYHA Class IV. The TI in HF patients was higher than that in control subjects and had a wider range (table 3) and there was statistically significant difference between mean Tei indices in patients with HF compared with control subjects. The mean value of EF in patients with HF (49 ± 14%) was lower than in control subjects (57 ± 9%). A comparison of the TI in patients in HF with EF >45% and those with EF ≤45% and controls, showed statistically significant difference between each HF subgroup and mean TI of the controls (see table 4). Also, the mean value of Tei index in patients with heart failure, sub-grouped into two, showed that patients with EF >45% had a lower TI mean value than those with EF
Number of patients in HF with EF >45% and EF ≤45% were 50 and 40 respectively.
Pulsed Doppler recordings of mitral inflow (left side) and left ventricular outflow (right side) in a normal subject. The value of the Tei index is 0.32
Pulsed Doppler recordings of mitral inflow (left side) and left ventricular outflow (right side) in a heart failure subject. The value of the Tei index is 1.807
In virtually all regions of the world, heart failure is common and on the rise7,22. Heart failure is a major and growing health problem resulting from cardiac damage caused by a variety of disease processes7,23-24.
Two-dimensional and Doppler echocardiography facilitate the evaluation of different periods of the cardiac cycle, allowing the acquisition of a combined systolic and diastolic index of left ventricular performance (Tei Index) in a simple, reproducible and reliable manner1,25,26,27. Study on this index is rather scarce in our environment. Our study revealed the usefulness of Tei index in patients with heart failure in Cardiac Care Unit at Obafemi Awolowo University Teaching Hospitals Complex, Ile – Ife, within the study period. The Tei indices obtained in the patients with heart failure were higher and with wider ranges when compared with age and sex matched normal controls. This higher values of the Tei indices in patients than in healthy individuals were due to prolongation of the isovolumic time intervals and a shortening of ejection time. This is because myocardial contractility and relaxation are energy dependent28,29 and significant myocardial dysfunction results in the prolongation of the isovolumic time intervals, and a shortening of the ejection period. Thus, the result of the formula (a – b)/b tends to increase. Similar findings were reported by Bruch et al26 and Dujardin et al11, though the latter study group consisted only of dilated cardiomyopathy as the aetiology of the heart failure compared to our study where systemic hypertension, dilated cardiomyopathy and rheumatic heart disease were all involved in decreasing order, hypertension being the commonest cause (64.4%), a finding which agrees with previous local studies30, 31. Other causes of heart failure identified in the study include
In our study, the mean value of the index was significantly different between normal subjects and heart failure patients of varying severity as determined by the NYHA functional classification of heart failure, showing the index can reasonably differentiate heart failure patients and normal subjects. This finding is important as it shows Tei index can be used to identify patients in heart failure presenting with mild symptoms. This finding agrees with findings of the aforementioned Bruch et al study26 which had also compared the index in normal controls with patients in heart failure of mild to moderate severity.
Also in our study, the mean TI was higher with increased HF severity, and there was statistically significant difference between the mean Tei indices of patients in NYHA class II versus class IV, class III versus class IV, though not between class III and III. This finding agrees with several others including Tei et al1 who in their study, conducted in heart failure patients in NYHA Class II to IV with ejection fractions 30 to 50%, showed statistically significant difference in the mean Tei indices between the functional groups of the patients. In addition, Ohno et al35 had also shown in their studies that patients with advanced NYHA classifications or patients with restrictive left ventricular filling patterns (which reflect higher pulmonary wedge pressure) and advanced congestive heart failure also exhibited increased myocardial performance index (Tei index) values.
Our study also revealed the trend of presentation of patients with heart failure in our environment, of which over 50% were in NYHA Class IV. In most of these cases, the heart failure is structurally advanced with altered left ventricular geometric pattern, as the ellipsoid shape of the heart tends to become spherical and therefore leads to limitations in the use of most of the traditional parameters for assessing systolic and diastolic functions. This further buttresses the relevance of Tei index.
The comparison of two groups of patients with relatively normal ejection fraction (>45%) and low ejection fraction (≤45%) to the corresponding Tei indices showed that the mean myocardial performance index was higher with decreased ejection fraction. There was an inverse relationship between TI and EF (as the TI increased, the EF decreased). Our finding agrees with that by Mohammed and colleagues25 who had reported in their study that Tei index was significantly higher in patients with left ventricular systolic dysfunction (EF
Myocardial performance index (Tei index) combining systolic and diastolic time intervals as an expression of global myocardial performance index correlates with cardiac function and seems to be a useful complimentary marker in assessing left ventricular function.
Limitations Of The Study
The small sample size did not allow adequate stratification for the observation of significance or lack of it.
The effects of loading conditions and arrhythmias on this index remain to be elucidated.
The study indicates that Tei index is a useful myocardial performance index having a useful role in determining overall cardiac dysfunction and can be used to separate patients with and without heart failure. The index showed a significant difference with heart failure severity (functional class) and an inverse relationship with ejection fraction.