European Journal of Echocardiography Advance Access originally published online on August 15, 2007
European Journal of Echocardiography 2008 9(3):381-383; doi:10.1016/j.euje.2007.06.013
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Hand carried echocardiography screening for LV systolic dysfunction in a pulmonary function laboratory*
University of Chicago, 5841 S. Maryland Avenue, MC 5084, Chicago, IL 60637, USA
Received 9 April 2007; accepted after revision 10 June 2007; online publish-ahead-of-print 15 August 2007.
* Corresponding author. Tel: +1 773 702 5836; fax: +1 773 702 1043. E-mail address: kspencer{at}uchicago.edu (K.T. Spencer).
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Abstract |
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Aims: Dyspnea is a common indication for pulmonary evaluation but also a common symptom in heart failure. Identification of dyspneic patients with significant LV systolic dysfunction is critical because of high morbidity of untreated heart failure. We sought to determine whether screening patients referred for pulmonary function testing (PFT) using a hand carried ultrasound (HCU) device could identify LV systolic dysfunction.
Methods: Forty-nine subjects were recruited from a pulmonary function lab to undergo a brief echocardiographic examination by an internist using a HCU device. All subjects also received an examination with a full-featured echocardiogram machine as a gold standard.
Results: All subjects with normal PFT had normal LV systolic function. Among subjects with abnormal PFT, 6 (15%) had LV systolic dysfunction and the remainder had normal LV systolic function. No subjects with LV systolic dysfunction by full-featured echocardiograms were missed by the HCU (sensitivity 100%, specificity 95%, negative predictive value 100%, positive predictive value 75%).
Conclusions: LV systolic dysfunction is prevalent among patients with pulmonary disease and can be accurately screened for by a physician using a hand carried ultrasound device with subsequent confirmation with complete echocardiography.
Keywords: Hand carried ultrasound; Left ventricular function; Ejection fraction; Pulmonary function testing
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Introduction |
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The evaluation of patients with dyspnea is a common clinical scenario and a frequent indication for pulmonary function testing (PFT). Patients with dyspnea and normal PFT are commonly referred for echocardiography to assess for cardiac causes of breathlessness. When dyspneic patients have abnormal PFT, this may be considered a satisfactory explanation for the patient's breathlessness, and cardiac evaluation may be forgone. However, it is clear that patients with significant pulmonary disease often have concomitant left ventricular systolic dysfunction (LVSD).1–5 Identification of dyspneic patients that have significant LVSD is critical because of the high morbidity and mortality of this disorder when untreated.
Identification of LVSD prior to PFT is limited by the considerable overlap between pulmonary and cardiac signs/symptoms, as well as the limited sensitivity of physical findings for cardiac disease in patients with significant lung disease. Although brain natriuretic peptide has proven useful in the differentiation of CHF and acute pulmonary exacerbations, it is not specific for LVSD.6–8 Echocardiography is the most commonly used modality to assess LVSD and is highly accurate, but problems of portability, cost, and training limit the use of traditional echocardiography as a screening modality.
Hand carried ultrasound (HCU) devices have the potential to overcome these difficulties. HCU devices weigh less than 8 pounds and provide relatively high quality 2-dimensional echocardiographic images. A variety of operators, from medical students to cardiologists, have used these devices to detect important cardiovascular disease in a wide variety of clinical settings.9–21 We sought to test whether a general internist with limited echocardiographic training could screen stable ambulatory outpatients referred for PFT for LV systolic dysfunction using a HCU device.
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Methods |
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The University of Chicago institutional review board approved the protocol and all patients gave informed consent. Forty-nine subjects (mean age 64, range 25–82 years, 71% female) undergoing pulmonary function testing for the evaluation of dyspnea were recruited to undergo a brief echocardiographic examination, using a HCU device (Optigo, Philips Medical). The subjects were selected consecutively without regard for the quality of their echocardiographic images. The HCU studies were performed by a general internist with 20 h of instruction in interpreting echocardiograms and experience in performing 30 exams using a HCU device. The physician was instructed to focus on identification of LVSD. LV dysfunction was visually graded in a binary fashion as an ejection fraction above or below 40%.
Following standard echocardiographic protocol, the subjects were examined in a left lateral decubitus position and underwent imaging from the parasternal, apical and subcostal windows. The examinations were limited to 5–10 min duration. All subjects also received a limited examination with a full-featured echocardiographic machine (Sonos 5500, Philips Medical) performed by a sonographer and LV systolic function visually interpreted in a binary fashion as an ejection fraction above or below 40% by an experienced echocardiographer. The presence of cardiac risk factors (hypercholesterolemia, family history, smoking, hypertension, diabetes) was recorded. Patients' pulmonary function tests were classified as abnormal or normal/nearly normal by an experienced pulmonologist and the internist performing the echo was blinded to these results.
The sensitivity, specificity, negative and positive predictive values for the HCU identification of LVSD were determined using the sonographer-performed echocardiographic examination as the gold standard. The age, sex and the presence of cardiac risk factors between subgroups with normal and abnormal LVSD were compared with Chi-square testing and t-testing. Statistical significance was considered at P < 0.05.
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Results |
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No patients had acoustic windows inadequate for interpretation. Eight subjects were identified as having LV systolic dysfunction by the internist using a HCU device. Of these, 6 were confirmed as having LVSD and 2 had normal LV systolic performance when imaged by the sonographer using the full-featured echocardiographic machine. There were no subjects with LVSD by gold standard echocardiograms that were missed by a HCU. Overall sensitivity for the identification of LVSD was 100%, specificity 95%, negative predictive value 100% and positive predictive value 75%. Age and sex were not different between subjects with an abnormal HCU examination and a normal examination. At least 1 traditional cardiac risk factor was found in 78% of subjects, but the number of risk factors present did not affect the likelihood of finding LVSD (P = 0.74). Most of the subjects had abnormal PFT (39, 80%), with 7 normal (14%) and 3 technically inadequate (6%) studies. All the subjects with normal PFT results had normal LV systolic function. Among subjects with abnormal PFT, 6 were found to have LVSD (15%), and the remaining had normal LV systolic function. Conversely, all subjects with LVSD had abnormal PFT.
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Discussion |
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Pulmonary disease and heart failure from LVSD are chronic disorders frequently seen in clinical practice as causes of dyspnea. The sheer frequency of these disorders as well as shared risk factors would predict their common coexistence. In fact, studies have demonstrated a prevalence of LVSD in unselected patients with chronic pulmonary disease of 10–36%.1–3,5 Identification of pulmonary patients with concomitant cardiac dysfunction would provide an opportunity to alter the natural history of their LVSD with therapies known to improve morbidity and mortality.
Identification of LVSD in pulmonary patients is difficult as there is extensive overlap between pulmonary and cardiac clinical signs and symptoms. BNP has proven useful in identifying CHF in patients with acute pulmonary exacerbations but not specific for LVSD.6–8 In addition, as many patients with compensated CHF do not have elevated BNP, echocardiography is more reliable to detect unsuspected LVSD in stable outpatients.22 Although echocardiography is superb in identifying LVSD, the cost and size of standard platforms make it impractical for routine screening in outpatient clinics. Hand carried ultrasound, which is substantially more portable and much cheaper has proven useful for screening patients for LVSD in a variety of clinical settings.9–11,14–18 These devices have proven useful even when used by less experienced operators, an important element of successful screeing.11,14,16,18,23,24
Clinicians when faced with dyspneic patients that have abnormal PFT may attribute their dyspnea to their pulmonary disease and not seek noninvasive cardiac testing. In this study 15% of patients with abnormal PFT had LVSD. All cases were successfully identified by a general internist with limited echocardiographic training using a hand carried ultrasound device. The subjects with LVSD in this study could not be identified by age, gender or cardiac risk factors. This is consistent with prior data that demonstrated routine clinical evaluation including history, electrocardiogram and chest X-ray failed to discriminate between patients with COPD alone and those who had LVSD in addition to COPD.25
The rate of LVSD is considerably higher than the 1.8–4.0% prevalence detected using echocardiography in the asymptomatic, general population.26 The prevalence of LVSD in this study is also higher than other studies using HCU in outpatients at high risk for cardiovascular disease, such as underserved minority patients and diabetics where the rates of LVSD were 3.3% and 4.7%, respectively.16,18 However, the prevalence of LVSD seen in this study (15%) is similar to the rates reported of 10–21% in studies of unselected chronic pulmonary patients which used a similar definition of LVSD (EF < 40%).1,2,5
The internist in this study identified 2 subjects with LVSD in whom the sonographer-performed echocardiogram revealed normal LV systolic performance. This rate of false positives is consistent with other studies in which relatively inexperienced operators using a HCU device tended to overestimate the prevalence of LVSD.18 All abnormal HCU examinations should be followed by a complete full-featured echocardiogram. The cost of a complete echocardiographic study for the false positive patients needs to be weighed against the value of correctly identifying patients with LV systolic dysfunction in whom morbidity and mortality could be reduced if screening leads to the adoption of proven therapies for heart failure.
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No assessment of diastolic function was performed and it is possible that subjects had diastolic dysfunction as a contributor to their dyspnea. However, the amount of teaching required to perform and interpret diastolic function studies and the increased cost of devices with this capability would significantly lower the potential for use as a screening device at the point of care. Patients with dyspnea out of proportion to their PFTs and without LVSD on screening echocardiography should have a complete echocardiogram to evaluate for other cardiac causes of dyspnea. We used a single device and internist, so we could not assess the inter-device or inter-observer variability in accuracy.
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Notes |
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* No funding sources, grants or financial support received for preparation of this paper.
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References |
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