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Hand-held echocardiography is useful for diagnosis of left systolic dysfunction in an elderly population

Line Lisbeth Olesen1, Andreas Andersen1 & Søren Thaulow2

1. jul. 2015
14 min.

Faktaboks

Fakta

Heart failure is common in the elderly, but there are indications of under-diagnosis and under-treatment [1-3]. Consequently, there is a need for reliable methods to screen for left ventricular systolic dysfunction (LVSD) in the growing geriatric population.

The clinical diagnosis of LVSD is unreliable and cardiac dysfunction needs to be verified [4-7]. Magnetic resonance has the best diagnostic reproducibility, but it is cumbersome as opposed to classic 2D echocardiography, which is the gold standard for LVSD diagnosis in
daily clinical practice [8]. In recent years, portable echocardiographs have emerged on the market. They are inexpensive and easily accessible; but only few investigations have compared them with standard echocardiographs [9-13].

The aim of the present study was to test the quality and usability of a hand-held echocardiograph compared with a standard echocardiograph for screening for LVSD in a geriatric population.

METHODS

This study forms part of an investigation focusing on early detection of heart failure in the elderly population. It was performed in compliance with the Declaration of Helsinki and approved by the local ethics committee and the Danish Data Protection Agency. For recruitment of patients, the study was announced locally in the Danish Association of Senior Citizens (Ældresagen), in a newspaper article, in our department of cardiology and in a heart failure clinic. The study population was representatives of a mixed and mobile geriatric population. It included a total of 260 subjects aged 75 years old or older. The subjects were recruited from the outpatient clinic and the general geriatric population with risk factors for or with known heart disease, as well as from the healthy background population. Table 1 shows the baseline characteristics of the study participants.

The 260 participants were invited to the outpatient clinic. Within one hour, each participant underwent a standard echocardiography lasting approximately 15 minutes, and a hand-held echocardiography, which
lasted on average of 10 minutes. The participants stayed in the same room during the procedure and were lying on an echocardiographic stretcher in a left-sided position.

The echocardiographers performed either standard or hand-held echocardiography blinded to any subject data and to each other´s results. LVSD was diagnosed from the echocardiographic images and ejection fraction (EF) < 40-50%. Unfortunately, 25 handheld echocardiograms were deleted and lost to follow-up due to a misunderstanding regarding the secure storage of the data. This left 235 cases for analysis in the present study.

The digitally stored recordings were reviewed by an independent and blinded echocardiographer who reviewed the 235 handheld echocardiograms once and the 260 standard echocardiograms twice (separated by an approx. three-month period to avoid bias).

As an expert on valvular diseases, the reviewing echocardiographer was asked to pay special attention to valvular changes, to select only those which were to undergo follow-up, and to disregard any insignificant changes.

All echocardiographers completed a structured data sheet. The evaluation was focused on LVSD, EF and valvular disease because other changes were infrequent and because of the limitations of the hand-held echocardiograph. Financial analysis was not performed.

All the echocardiographers were very experienced in standard echocardiography (expert level III), but had limited training in advance in hand-held echocardiography. Two echocardiographers performed 58% of all the standard echocardiographies and 96% of all the handheld echocardiographies.

Standard echocardiography was performed with a General Electric Vingmed Vivid 7 or E9, MJS probe 1.5-4.0 MHz and following the guidelines from the Danish Society of Cardiology.

Handheld echocardiography was performed with General Electric Vscan and probe 1.7-3.8 MHz to evaluate A) LVSD: yes, no, or cannot judge, B) EF: < 40%, 40-50%, > 50%, cannot judge, C) standard echocardiography recommended: No, Yes (No: nothing abnormal. Yes: LVSD, valvular disease, other changes in cardiac function or morphology, poor quality, technical problems, inconclusive echocardiogram or discrepancy between what was found and what was expected).

Statistical analysis

The statistical analysis was performed with STATA 12 (StataCorp, College Station, Texas, USA). The pairwise agreement on LVDS between methods, hand-held and standard echocardiography, and between echocardiographers was evaluated by Cohen’s Kappa statistic. K-values < 0.4, 0.4-0.75, and > 0.75 were considered to represent poor, fair-to-good and excellent agreement, respectively. Kappa with and without (cannot judge) are presented in Table 2 and Table 3. The hypothesis of equal proportions of LVSD was tested by McNemar’s test. A p value below 0.05 was considered statistically significant. Positive (PPV) and negative (NPV) predictive values were calculated of: 1) LVSD diagnosed by hand-held echocardiography with standard echocardiography as reference, 2) LVSD diagnosed on reviewed hand-held echocardiograms with standard echocardiograms as reference, and 3) standard echocardiography recommended performing hand-held echocardiography with significant valvular disease as reference.

Trial registration: not relevant.

RESULTS

Concerning image quality, standard echocardiography is superior to hand-held echocardiography, illustrated in this study by the fact that every standard echocardiogram was interpreted, whereas four hand-held echocardiograms could not be judged by the performing echocardiographer and 14 hand-held echocardiograms could not be judged by the reviewing echocardiographer.

Intra-observer variability

The same echocardiographer reviewed the standard echocardiograms twice with excellent agreement (K = 0.84) regarding presence of LVSD (Table 2) and good agreement (K = 0.70) regarding EF (Table 3) demonstrating diagnostic stability and a low intra-observer variability (p = 0.42).

Inter-observer variability

Table 2 shows that fair-to-well agreement between all echocardiographers regarding LVSD (K = 0.67-0.74) with no-significant inter-observer variability (p = 0.07).Nevertheless, when comparing the performing echocardiographers and the reviewing echocardiographer, we observed a considerable inter-observer variability (p = 0.002 / < 0.001). Table 3 suggests that the reviewing echocardiographer had a tendency to decide on a higher EF than the performing echocardiographers and to discard LVSD when EF > 40%, often contrary to the performing echocardiographers.

Table 3 shows that regardless of the type of echocardiography (standard versus hand-held), there was considerable disagreement about the exact EF when EF was in the indecisive gray zone about 40-50%. Thus, in the grey zone, the diagnostic variation and inter-observer variability were substantial.

Inter-method variability

Table 2 shows good agreement on and non-significant inter-method variability of LVSD diagnosed by: 1) all performed standard and hand-held echocardiographies (K = 0.70, p = 0.07), 2) the standard and hand-held echocardiographies performed by the two echocardiographers who did most of the examinations (K = 0.74, p = 0.81) and 3) the reviewed standard and hand-held echocardiograms (K = 0.74, p = 1).

Thus, when standard and hand-held echocardiography were compared, the inter-method variability when diagnosing LVSD was small; provided the image quality was OK.

Handheld echocardiography and negative predictive value of left ventricular systolic dysfunction

Table 2 shows that the NPV of hand-held echocardiography in assessment of LVSD was 0.94 when standard echocardiography was used as a reference. There was disagreement on LVSD in ten cases, where hand-held echocardiography concluded EF > 40% and no LVSD; whereas standard echocardiography concluded EF < 40 % in five cases and > 40 % in five cases and LVSD in all ten cases, in three cases, rapid atrial fibrillations made it difficult to estimate EF, and five cases were in the grey zone where there is a diagnostic dilemma concerning LVSD.

Hand-held echocardiography and negative predictive value of valvular disease

Table 4 shows that hand-held echocardiography had a NPV of 0.95 regarding the presence of significant valvular disease with significant valvular disease as a reference. Whenever hand-held echocardiography was not completely normal, standard echocardiography was recommended. In total, 20 patients out of 55 with valvular dysfunction had also LVSD. Six cases (11%) with significant valvular disease according to standard echocardiography were missed using hand-held echocardiography. One of these patients had a previously unrecognised moderate aortic stenosis and a cardiac murmur; one had a biologic aortic valve and was followed in the out-patient clinic, whereas four were without any significant valvular disorder according to a detailed follow-up using standard echocardiography.

DISCUSSION

This study shows that hand-held echocardiography was comparable with standard echocardiography in terms of quality and safety in screening for LVSD in a geriatric population, when performed by expert echocardiographers. We found a small inter-method variability, but different inter-observer variability. This shows that results depend more on the operator than on the equipment, which emphasises the need for user-education and -evaluation. These findings are in accordance with previous studies [9, 11].

Table 2 and Table 3 illustrate that echocardiography is not an accurate and unfailing diagnostic method. Rather, it is open to differences in interpretation. Thus, in order to compare different echocardiographic equipment and to avoid operator-dependent bias, the intra- and/or the inter-observer variability must be low [8, 9, 11]. This source of variation has gone unnoticed in a number of previous studies [6, 7, 14-16].

In our study, the reviewing echocardiographer manifested very small intra-observer variability and good concordance between hand-held and standard echocardiography for the diagnosis of LVSD. Likewise, there was non-significant inter-observer variability between the performing echocardiographers and concordance between hand-held and standard echocardiography for diagnosis of LVSD. This corresponds to a small inter-method variability and shows that the hand-held echocardiograph is a sensible alternative to the standard echocardiograph when screening for LVSD [11].

This is confirmed by the reliability of the hand-held echocardiograph which did not miss many cases with significant disease, which is reflected in the NPV > 0.90 [16]. Thus, standard echocardiography may be abstained from, when it is assessed that hand-held echocardiography is normal [6, 11, 17].

The hand-held echocardiograph, the Vscan, is the size of a smartphone, it weighs 390 g including the probe and fits into a pocket. It is used as a means to obtaining early and prompt diagnosis [17, 18], to extend the physical examination [4, 10, 13, 14, 17] and to assist some invasive procedures [12]. In addition to using it at the point-of-care and for the triage of the acutely admitted patients [13, 15, 17, 19], the present study suggests that it may be used to screen for LVSD in outpatient settings [5-7, 10, 16, 18].

It is important to keep in mind that the hand-held echocardiograph has its limitations [9, 10]. It has fewer options than the standard echocardiograph and the image quality is poorer. The hand-held echocardiograph has 2D and colour Doppler, but no M-mode and no spectral Doppler [4]. It should not be used to evaluate diseases of the valves, nor diastolic function or pulmonary pressure [6, 17, 18]. The patient has to be informed that a hand-held echocardiography does not replace a complete echocardiography [10].

Because of the limitations of the hand-held echocardiograph, standard echocardiography should be performed whenever handheld echocardiography is not completely normal [7, 15, 19]. This is important especially in the elderly where heart diseases are very prevalent; and, thus, the hand-held echocardiograph should be used with particular caution in the geriatric population.

For the expert echocardiographer, it was easy to acquire and interpret images with the hand-held echocardiograph; but because unqualified users of hand-held echocardiography are more likely to make errors [14, 15] and to misdiagnose [9, 13, 17], several professional societies recommend certification for all users of the hand-held ultrasound scanners [6, 9-11, 18, 20].

CONCLUSION

Based on our findings, we conclude that hand-held echocardiography may be used safely by the expert to screen the elderly for LVSD and other changes in cardiac function and morphology in order to select patients for standard echocardiography. Hand-held echocardiography may increase efficiency and could prove to be both time- and cost-effective [18] as the number of relatively slow and high-cost standard echocardiographies could be reduced.

Correspondence: Line Lisbeth Olesen, Groenagergaardsvej 5, 4070 Kirke Hyllinge, Denmark. E-mail: llole@regionsjaelland.dk

Accepted: 22 April 2015.

Conflicts of interest:Disclosure forms provided by the authors are available with the full text of this article at www.danmedj.dk

Acknowledgements: The authors would like to thank Hanne Elming, Cardiologist Consultant, Department of Cardiology, Roskilde Hospital, for revision of echocardiograms and Hans Burchardt and Klaus Klausen, Cardiologist Consultants, Department of Cardiology, Roskilde Hospital, for their performance and assessment of echocardiographies.

Referencer

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