Echocardiography and pulmonary artery pressure: correlation in chronic obstructive pulmonary disease.
HS Trivedi, MN Joshi, AR Gamade
Department of Medicine, Grant Medical College, Bombay, Maharashtra.
H S Trivedi
Department of Medicine, Grant Medical College, Bombay, Maharashtra.
The aim of this study was to assess whether 2 dimensional echocardiography can provide reliable parameters to quantitatively estimate pulmonary hypertension (PH) in patients with chronic obstructive pulmonary disease. Twenty subjects, 16 males and 4 females, mean age 54.5 year +/- 4.92 were evaluated. Right ventricular dimensions were measured using subcostal 2- dimensional (2D) approach viz. right ventricular maximum short axis (Rv) and tricuspid annulus (TA). Free right ventricular anterior wall (AW) was measured by M-Mode. A 2D Index was calculated RV x TA + Aw and the same correlated with mean pulmonary artery pressure (r = 0.97). This appears to be a useful non-invasive method foe estimating PH in cases of COPD.
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Trivedi H S, Joshi M N, Gamade A R. Echocardiography and pulmonary artery pressure: correlation in chronic obstructive pulmonary disease. J Postgrad Med 1992;38:24-6
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Trivedi H S, Joshi M N, Gamade A R. Echocardiography and pulmonary artery pressure: correlation in chronic obstructive pulmonary disease. J Postgrad Med [serial online] 1992 [cited 2023 Jan 30 ];38:24-6
Available from: https://www.jpgmonline.com/text.asp?1992/38/1/24/736
Chronic obstructive lung disease is one of the most common pulmonary diseases. In India, the problem has been studied in the North by Malik. A special problem in rural India is related to domestic fuel. The practice of burning 'chulia' (cow dung and fir dung) is associated with a higher risk of respiratory disease. A prevalence of 5% has been found in 'chuila' users as compared to 1.5 to 2.5% amongst 1 user of other fuel modes like kerosene and coal.
It is essential to assess the extent of impairment of pulmonary function and the pulmonary hypertension (PH) caused by the same to establish the long-term prognosis of the disease. There are various non-invasive methods to determine the respiratory function and the extent of reversibility of the same. However, it is difficult by non-invasive methods to accurately determine the PH. Various attempts have been made to assses the same by electrocardiography, roentegenology and M-mode echocardioqraphy, but the correlations are not as close as required,,. The aim of this study is to assess PH, by utilizing right venticular parameters obtained by echocardiography.
Twenty patients with COPD, diagnosed by history, physical examination, electrocardiography and roentegenology were studied. The diagnosis was further supported by pulmonary function tests (PFT) and arterial blood gas (ABG) analysis. The age group studied is 48 to 70 years (mean 59.5 + 4.92). The study was performed when the patients were stable i.e. in the absence of a recent acute exacerbation of symptoms. PFTs were performed by means of a computerised system (Morgan). ABI3 analysis was done by ABI3 (Copenhagen) analyser.
Real time two dimensional echocardiography and M-Mode echocardiography was performed using a 2.25 mmHz transducer. The subject were examined in the supine position with the transducer angled towards the patient's left shoulder, until the study plane, was parallel to the plane of the tricuspid annulus. Subcostal views were obtained for (1) tricuspid annulus (TA), (2) right ventricular cavity dimension (RV) i.e maximum short axis measured from the right septal surface to the free right ventricular wall, at the point of maximal width parallel to the TA. The right ventricular anterior wall (AW) was measured by moving the cursor perpendicular to the free RV wall, by M-Mode. All the dimensions were end diastolic. All patients were subjected to cardiac catherterization of the right side, using flow directed Swan Ganz catheters and multipurposes Cournard 717 catheters. The pulmonary artery mean and wedge pressure were recorded. All patients had normal pulmonary wedge pressures excluding left sided cardiac disease. A 2D Index was calculated 2D Index (2DI) = RV X TA + AW. A graph was plotted MPAP (y axis) versus. 2DI (x axis) and a coefficient of correlation were calculated. A formula for the slope of the graph was derived, there being two variables MPAP and 2DI. If the value of one is know, the other may be calculated, in a given case.
The date of pulmonary function tests and arterial blood analysis (Mean + 1 - 2 SD) are given in [Table:1], [Table:2].
The current non-invasive methods of assessing PH are unreliable in cases of COPD. Roentegenology has been found to be unreliable to demonstrate right ventricular enlargement-. Considerable dilatation of right ventricle can take place without being demonstrable by X-ray,. Standard criteria for RVH by electrocardiography have been found to be fulfilled, in only one third of patients of COPID who have been shown to have RVH at autopsy,,,,. Thallium perfusion imaging has been used to give indirect evidence of PH by measurements of wall thickness. However, measurements of right ventricular thickness in this manner do not correlate with pulmonary hypertension. Echocardiograms have been used to give information on RVH and/or PH in cases of COPD. Previously M-mode echograms were done to measure right venticular dimension but in COPD, have been found to be unsatisfactory. Because of inaccessible intra-thoracic position and irregular geometrical shape, the right atrium and right ventricle are difficult structures from which to obtain reproducible echographic signals by M-Mode examination.
2 D studies provide a 30 to 80 degrees sector arc image and a good correlation is found with 2D measurements and actual chamber size, by studies of rubber casts of necropsy hearts. Right ventricular maximum short axis by 2D echo was found to be greater in patients with RVH than controls, and distinctly superior to MMode measurements in separating normals with patients of right ventricular dilatation,,,.
Qualitative criteria of PH by pulmonary value echo are well known. Various studies have, however, concluded that pulmonary valve echo is not a satisfactory method to quantitatively assess PH in patients of COPD. Ratio of right and left ventricular end diastolic diameter correlate with PH, but not enough to be used alone as objective criterion. 2 Measurement of right ventricular anterior wall thickness is distinctly superior by M-Mode. This approach provides a success rate of 80% as compated to 50% by subcostal approach, and hence, these measurements were recorded by M-Mode.
The above discussion highlights the shortcomings of various non- invasive methods of assessing PH in COPD. We have studied a unique approach, using a combination of data obtained by echocardiograms, which overcomes the difficulties discussed earlier. Our data shows the advantage of measurement of measuring tricuspid annulus and RV short axis by 2D subcostal approach and measurement of AW thickness by M-Mode. We calculated a 2D Index Le RV x TA + Aw and found that this has an excellent correlation with MPAP (Coefficient of correlation = 0.97). From the graph (see [Figure:1]) obtained by plotting M PAP against 2D Index, we derived a formula for the slope Y = MX + C. (Slope M = 411.5,C = -207.49). Hence Y = 41.5 X x -207.49. For a given ‘X’ i.e 2DI, a ‘Y’ i.e MPAP can be calculated and would correlate excellently. A 2D Index thus obtained, can provide a good estimation of pulmonary artery pressure and would greatly assist in management and prognosis. A similar study by G. Zenkar et al correlated various echocardiographic parameters with MPAP and found that this index has the closest correlation.
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