Association between left ventricular function and severity of chronic obstructive pulmonary disease

 

 

Abstract               Chronic obstructive pulmonary disease (COPD) is a complex disease with various systemic manifestations and one of the co-morbidity linked with COPD is cardiovascular disease. Left ventricular dysfunction is a well-known complication of COPD. There are neurological, humoral and mechanical interactions between both organs, and various mechanisms that lead to structural or functional ventricular alterations can coexist in patients with respiratory disease. Several studies have shown that cardiovascular events are more common in patients with COPD. We used echocardiography to evaluate the changes in left ventricular size and function. The aim of this study to evaluate the Left ventricular changes associated with the severity of COPD using GOLD guidelines and echocardiographic findings. This study was a cross-sectional study and consists of 134 patients with known history of chronic pulmonary obstructive disease (COPD). Echocardiographic assessment of left ventricular systolic function (ejection fraction) revealed that significant difference in COPD patients of different categories and there was significant difference regarding left ventricular diastolic dysfunction (E/A ratio and isovolumic relaxation time, IVRT). Left ventricular functions are affected in COPD patients especially with progression of the disease.

Key Word: left ventricular functions, Echocardiography, COPD.

 

 

INTRODUCTION

The anatomical and functional relationship between the heart and lungs is so close that dysfunction of one of these systems can affect the other¹. There are neurological, humoral and mechanical interactions between both organs, and various mechanisms that lead to structural or functional ventricular alterations can coexist in patients with respiratory disease. Several studies have shown that cardiovascular events are more common in patients with chronic obstructive pulmonary disease (COPD) compared to smokers without the disease^2-5. Classification of the severity of COPD according to the Global Initiative for Obstructive Lung Disease (GOLD) classification is based on the degree of air-flow obstruction (percent of predicted FEV1)⁶. The association between cardiovascular diseases (CVD) and COPD is much more complex, and may involve other factors: biological (hypoxemia, endothelial dysfunction, increased platelet activation, arterial stiffness)^7-10, mechanical and/or functional (deterioration in the forced expiratory volume in the first second, emphysema, hyperinflation)^11-12, neurohumoral (excess sympathetic nerve activity)¹³ and genetic (polymorphisms of the metalloproteinases, telomere shortening)^14-15. Right ventricular dysfunction is a well-known complication of COPD. Research reports mentioning that there may left ventricular systolic and diastolic dysfunction is associated with right ventricular dysfunction or as a separate complication^16-18. Echocardiography is simple, non-invasive and reliable technique to assess the left ventricular dimensions and function^19-21. In this study we used echocardiography to evaluate the changes in left ventricular size and function.

 

Materials and Methods

The proposed research study was a cross-sectional study and consists of One hundred thirty-four patients (88 male, 46 female: mean age 63 ± 7 years) with known history of chronic pulmonary obstructive disease (COPD). The proposed research study was carried out at Mahamaya Rajkiya Allopathic medical college, Uttar Pradesh and Santosh Medical College, Ghaziabad. This study was commenced after obtaining the ethical clearance from Institutional Human Ethics Committee (IHEC). Patients with known case of Chronic Obstructive Pulmonary disease (COPD) confirmed by medical history and pulmonary function tests were selected using systemic random sampling and informed consent was obtained from the patients before subjecting to research methods. Patients with coronary heart disease (CAD), chronic lung disease other than COPD, chronic kidney disease, valvular cardiac disease, and any systemic or cardiac diseases that may cause pulmonary hypertension, malignant tumors, head and neck abnormalities, patients with exacerbations in the last four weeks, patients with a weak echo window and patients who could not perform spirometry were excluded from the study. All patients have undergone respiratory (spirometry) tests for assessment of pulmonary function. The forced vital capacity (FVC) and forced expiratory volume during first one second (FEV1) were measured and FEV1/FVC ratio was calculated from measured values. The patients were divided into four groups in line with the guidelines of Global Initiative for Chronic Obstructive Lung Disease (GOLD) as mild (FEV1 ≥ 80% expected value), intermediate (50% ≤ FEV1<80% expected value), severe (30% ≤ FEV1<30% expected value) and very severe (30% ≤FEV1<50% expected value), provided that the expected post-bronchodilator FEV1/FVC ratio was less than 70%⁶. A two-dimensional trans-thoracic Doppler echocardiography was performed on all patients while in the left lateral lying position using a eSaote SpA Mylab50 X vision echocardiographic machine with the cardiologist making all measurements who was blind to the respiratory functional test findings of the patients. All measurements were performed during at least three consecutive cardiac cycles and normal respiration and at the end of experiment. Left ventricular end-diastolic and end-systolic volumes were measured using the two-dimensional images from both the apical four and two-chamber views. Left ventricular mass was calculated from linear measurements obtained from parasternal views. The left ventricular systolic function was evaluated by measuring the ejection fraction (EF%) according to Teichholz formula. The left ventricular diastolic function was evaluated by measuring the early (E wave) and late (A wave) diastolic mitral inflow velocities, their ratio, the E wave deceleration time (DT) and the isovolumic relaxation time (IVRT).

Statistical Analysis: Results were expressed as mean ± SD. The data were analyzed by one-way analysis of variance (ANOVA) followed by Bonferroni or Tukey’s multiple comparison tests, respectively. Statistical significance was considered at P<0.05.

RESULTS

Table 1: Classification of patients (Gender wise) according to severity of COPD (COPD severity stages were based on GOLD classification)

 

 

 

 

 

Table 2: showing the baseline and clinical characteristics of study population having mild, moderate, severe and very severe stages of COPD. Values expressed as Mean + SD. SBP-Systolic blood pressure; DBP-Diastolic blood pressure; PP-Pulse pressure; MABP-Mean arterial blood pressure

 

Table 3: showing the Lung function parameters of study population having mild, moderate, severe and very severe stages of COPD. Values expressed as Mean + SD. FVC-Forced vital capacity; FEV1-Forced expiratory volume during first second.

As shown Table 3, COPD patients of different stages shown bronchial obstruction and decreased spirometric volumes like forced vital capacity(P<0.0001), forced expiratory volume(P<0.0001) and FEV1/FVC(p<0.0001

 

Table 4: showing the Left ventricular echo-cardiac dimensions of study population having mild, moderate, severe and very severe stages of COPD

LVIDd - Left ventricular internal dimension in diastole; LVIDs - Left ventricular internal dimension in systole; PWT – Posterior wall thickness; IVST – Inter ventricular septal thickness; LVM – Left ventricular mass; LVEF – Left ventricular ejection fraction.

Table 5: showing the statistical comparison (One-way ANOVA followed by post-hoc tests) between four grades of COPD patients in of left ventricular echo-cardiac measurement.

Variable	Mild vs. Moderate	Mild vs. Severe	Mild vs. Very Severe	Moderate vs. Severe	Moderate vs. Very Severe	Severe vs. Very Severe
LVIDd(mm)	NS	<0.05	<.0001	<0.05	<.0001	<0.001
LVIDs (mm)	NS	NS	NS	NS	<0.05	NS
PWT(mm)	NS	NS	<.001	NS	<0.05	<.0001
LVEF(%)	NS	NS	<0.05	NS	<0.05	<0.05
E/A ratio	NS	0.0001	<.0001	<.0001	<.0001	NS
Isovolumic relaxation time(ms)	NS	<0.05	<0.05	<0.05	<0.001	NS