Postgrad Med J 2000;76:289–291 289 Unreliability of cardiothoracic ratio as a marker of Postgrad Med J: first published as 10.1136/pmj.76.895.289 on 1 May 2000. Downloaded from left ventricular impairment: comparison with radionuclide ventriculography and echocardiography Andrew L Clark, Andrew J S Coats Abstract described (primarily for use in epidemiological Background—The size of the heart as- studies),1 3–5 which use the cardiothoracic ratio sessed by cardiothoracic ratio on chest from a posteroanterior chest radiograph as an radiography is often used as a screening index of the size of the heart. The chest test for the presence of heart failure and radiograph is widely available and frequently for assessing its severity. performed as a screening test for left ventricular Methods—We compared cardiothoracic failure. Other methods for assessing cardiac ratio (CTR), left ventricular ejection frac- function, such as left ventricular angiography tion (LVEF) from radionuclide ventricu- and echocardiography are less widely available. lography, and left ventricular dimensions Even after the diagnosis of heart failure is from echocardiography in a population of made, quantification of the severity of left ven- 91 patients (aged 60.4 (SD 9.6) years) with tricular impairment is important to give 67 a diagnosis of chronic heart failure. prognostic information. Results—There was a weak relation be- We sought to compare methods of quantify- tween CTR and LVEF (R=0.33) and frac- ing left ventricular function in widespread use tional shortening from echocardiography that are easily available in district general hos- (R=0.22). LVEF and fractional shortening pitals. We thus compared LVEF derived from correlated more closely (R=0.55). No radionuclide ventriculography with echocar- measure of left ventricular function corre- diographic indices derived from M mode lated with exercise capacity as measured echocardiography in patients with clinical by peak oxygen consumption. For the heart failure. In particular, we were concerned group of patients with a normal fractional to see whether the chest radiograph could be shortening (n=17), the left ventricle was recommended as a method for assessment of dilated in all but two (mean end diastolic left ventricular function. dimension 5.9 (0.7) cm). The two with normal dimensions had a low ejection Methods http://pmj.bmj.com/ fraction. For the 12 patients with a CTR in This was a retrospective study. Ninety one the normal range, the left ventricular end patients from the Royal Brompton heart failure diastolic dimension was only slightly database were identified who had had a chest smaller than for the rest (6.2 (0.9) v 6.9 radiograph, radionuclide ventriculography, and (1.2); p=0.045). an echocardiographic study within three Conclusions—Chest radiography is not a months of each other. Only those patients were included for whom M mode echocardiographic reliable indicator of the degree of left ven- on September 30, 2021 by guest. Protected copyright. tricular dysfunction. Echocardiography tracings were available. and radionuclide ventriculography are more appropriate investigations for as- RADIONUCLIDE STUDY Subjects were injected intravenously with 0.03 sessing cardiac function. Academic Unit, mg/kg of stannous fluoride red cell labelling (Postgrad Med J 2000;76:289–291) Department of agent (Amersham International). After allow- Cardiology, Castle Hill ing a period of 15–30 minutes for equilibration Hospital, Castle Road, Keywords: chronic heart failure; chest radiography; Cottingham, radionuclide ventriculography; echocardiography of the red blood cells, the patient was Kingston-upon-Hull positioned supine on a scanning couch, with HU16 5JQ, UK the gamma camera, a Sopha medical DS-X A L Clark An accurate diagnosis is the cornerstone of good rectangular field of view, connected to lead V6 management in chronic heart failure. Clinical of an electrocardiograph to synchronise events. Department of examination alone is notoriously unreliable for A bolus of 740 MBq of 99mtechnetium in Cardiac Medicine, establishing heart failure,12 and demonstrating Imperial College 0.3–0.5 ml was injected intravenously, with the School of Medicine, objective evidence of left ventricular dysfunction gamma camera positioned at 45º left anterior London, UK is crucial to make the diagnosis. Methods com- oblique with 10º of craniocaudal tilt. An equi- A J S Coats monly used are echocardiography (using either librium radionuclide ventriculogram was then the absolute left ventricular dimensions or a acquired; 16 frames were acquired in each R-R Correspondence to: derived index such as fractional shortening or Dr Clark interval, and summed repeatedly, until the end (e-mail: A.L.Clark@ ejection fraction) and radionuclide ventriculo- diastolic image contained 300 000 counts, to medschool.hull.ac.uk) graphy (again used to determine left ventricular ensure an accurate estimation of LVEF. ejection fraction, LVEF). Ventricular ejection fraction was calculated by Submitted 16 September 1999 Although heart failure is common, the diag- comparing background subtracted images at Accepted 27 October 1999 nosis can be diYcult. Scoring systems have been end diastole and end systole as: ejection 290 Clark, Coats Table 1 Demographic data (n=91); results are number or Results Postgrad Med J: first published as 10.1136/pmj.76.895.289 on 1 May 2000. Downloaded from mean (SD) Demographic data are shown in table 1. The Age (years) 60.4 (9.6) average dose of frusemide (furosemide) being NYHA taken was 83 (55) mg daily, although seven I16were on no diuretic. Twenty one patients were II 34 III 28 not receiving angiotensin converting enzyme IV 13 inhibitors. Twenty eight were receiving digoxin. Male:female 86:5 The indices of left ventricular function are Height (m) 1.73 (0.1) Weight (kg) 79.9 (14.5) shown in table 2. LVEDD and LVESD Diagnosis correlated closely (R=0.95; p<0.00001). The IHD 51 relations between LVEF from the radionuclide DCM 40 Peak oxygen consumption (ml/min/kg) 18.2 (7.1) study and echocardiographic measurements and cardiothoracic ratio is shown in table 3 and DCM = dilated cardiomyopathy; IHD = ischaemic heart disease; NYHA = New York Heart Association classification of figs 1 and 2. symptoms. From fig 1, it can be seen that most patients have both abnormal LVEF and fractional Table 2 Indices of left ventricular function; results are mean (SD) shortening. For the group of patients with a normal fractional shortening (n=17), the left Echo LVEDD (cm) 6.77 (1.17) ventricle was dilated in all but two (mean end LVESD (cm) 5.61 (1.38) diastolic dimension 5.9 (0.7) cm). The two Fractional shortening 0.18 (0.09) RNVG LVEF (%) 27.0 (15.0) with normal dimensions had a low ejection CXR CTR 0.56 (0.06) fraction. CTR = cardiothoracic ratio; CXR = chest radiograph; LVEDD = left ventricular end diastolic dimension; LVEF = left ventricu- lar ejection fraction; LVESD = left ventricular end systolic Table 3 Relations between the diVerent measures of left dimension; RNVG = radionuclide ventriculography. ventricular function fraction (LVEF) = (end diastolic−end systolic LVEDD LVESD Fractional shortening LVEF counts)/end diastolic counts × 100. LVEF R=−0.48 R=−0.56 R=0.55 — p<0.00001 p<0.00001 p<0.00001 — ECHOCARDIOGRAPHIC STUDY CTR R=0.32 R=0.32 R=−0.22 R=0.33 p=0.002 p=0.002 p=0.03 p=0.001 Left ventricular internal dimensions were acquired from standard M mode echocardio- CTR = cardiothoracic ratio; LVEDD = left ventricular end graphic images in the parasternal long axis view diastolic dimension; LVEF = left ventricular ejection fraction; LVESD = left ventricular end systolic dimension. at the mitral valve tips. Fractional shortening was calculated as left ventricular end diastolic 70 y = 92.8x + 10.2 dimension (LVEDD) minus left ventricular R = 0.55; p < 0.00001 end systolic dimension (LVESD) divided by 60 LVEDD. 50 http://pmj.bmj.com/ CARDIOTHORACIC RATIO (CTR) 40 CTR was determined by one of us (ALC) only where a standard posteroanterior chest film 30 LVEF (%) LVEF from within three months of the radionuclide 20 and echocardiographic studies was available. Only posteroanterior erect radiographs were 10 accepted. No anteroposterior, supine, or seated 0 on September 30, 2021 by guest. Protected copyright. films were accepted. The measurements were 0 0.1 0.2 0.3 0.4 0.5 made blind to the results of the other investiga- Fractional shortening tions. Figure 1 Relation between fractional shortening derived from echocardiography and left ventricular ejection fraction EXERCISE DATA (LVEF) derived from radionuclide scanning. The lower end Exercise data were available from maximal of the normal ranges are shown. incremental exercise tests with metabolic gas 10 exchange data. Patients were encouraged to exercise to exhaustion using the standard 9 Bruce protocol with the addition of a stage 0 8 (three minutes’ exercise at one mile per hour 7 with a 5% gradient). Subjects breathed 6 through a one way valve allowing the collection 5 of expired air. Expired air was mixed with an 4 inert indicator gas in a mixing chamber, and 3 samples taken every 10 seconds to be analysed by mass spectrometer (Amis 2000, Odennse, 2 LVEDD y = 6.1x + 3.3; R = 0.32 1 LVESD y = 7.4x + 1.5; R = 0.32 Denmark). Peak oxygen consumption was Echocardiographic dimension derived. 0 0.40 0.50 0.60 0.70 0.80 0.90 Cardiothoracic ratio STATISTICS Results are shown as mean (SD). The relation Figure 2 Relation between cardiothoracic ratio on a posteroanterior chest film and left ventricular end diastolic between variables was explored using linear dimension (LVEDD) and left ventricular end systolic regression analysis. dimension (LVESD). Cardiothoracic ratio and left ventricular impairment 291 There was no significant relation between graphy in a routine clinical setting agree well Postgrad Med J: first published as 10.1136/pmj.76.895.289 on 1 May 2000.