Clinical Usefulness of the Pocket Echocardiographic Device: Potential Advantage and Reliability Compared to the Conventional Echocardiographic Equipment

Introduction

Echocardiographic examination becomes a crucial diagnostic process in patients with cardiovascular disease. Technological evolution has led to the development of pocket size echocardiography (PE) with basic functions. It had great advantages compared to the full-size comprehensive and conventional echocardiography (CE) [1, 2, 3, 4]. PE can be wildly used in bedside examination during ward rounds, in emergency room for cardiology consultation and in remote village for its portable property because of pocket size nature. Since PE is often used by cardiologists but not sonographer to get the first information, it is necessary to assess the clinical value and to assess its contribution in current consultant mode. We hypothesized that PE is a useful and has a potential advantage in clinical practice compared to CE.

Methods

The study protocol was reviewed and approved by the Ethics Committee of Renji Hospital, Shanghai. We studied 200 patients who underwent PE and CE (male 107, female 93, age 56.6±16.6 years) during July 1, 2012 to August 31, 2012 in our hospital, included outpatients 105 (52.5%), emergency patients 33 (16.5%), hospitalized patients 57 (28.5%) and outside hospital consultation 5 (2.5%). A GE V-Scan (weight 390 g, General Electric, Milwaukee, WI, USA). Figure 1 with fixed sector angle of 75º and a 1.7- 3.8MHz transducer was used for PE. Color flow Imaging is available with a 30 º maneuverable sector. Spectral Doppler and M-mode imaging is not available. CE was performed with GE vivid E9 and PHILIPS ie33 within 2 hours after PE. Each patient was submitted to physical examination before PE and CE assessment. The patient demographics and underlining disease are listed in the Table 1. Beside 33 patients underwent bedside PE, 26 patients in catheter laboratory and intensive care unit also underwent bedside PE. PE studies were performed by a level 2 cardiologist followed by the guideline issued by American Society of Echocardiography [5]. Images and movies were acquired and stored in a folder of the device. CE was performed by a well trained level 3 sonographer. Each examiner was blinded to the results of the other examination. The final echocardiographic report was based on the results of CE. A single echocardiogrpher reviewed the examinations of all subjects separately to analyze the results.

Click to enlarge

Table 1: Patient demographics and underlining disease. Cardiovascular diseases were classified as major and minor abnormalities. Major abnormalities were considered to be clinically significant abnormalities that would trigger further diagnostic evaluation, to change or initiate treatment management, or to have prognostic significance [6]. Minor abnormalities were considered to be abnormalities that were of no clinical significance and therefore would not affect decision making for patient management. The present and severity of the valve regurgitation diagnosed by color flow imaging was evaluated by PE according to the guideline issued by American Society of Echocardiography [7]. Unsuspected major abnormalities were considered to be the first detected major abnormalities by echocardiography that did not reported in the history or were not suspected or previously described from the symptoms or physical examination. Since the PE had no spectral Doppler modality, left ventricular diastolic function and pulmonary systolic pressure could not be set to be compared. Sample size was calculated by SPSS 17.0 using non- inferiority tests for two correlated proportions. Continuous variables were presented as mean ± standard deviation. Categorical data was assessed with a Chi- square or Fisher-exact test if cell sizes were < 5. Agreement between PE and CE in echocardiographic results was assessed by the Kappa statistics. Based on Landis & Koch ’s classification [8], kappa values 0.21-0.40 looks as "Fair"; 0.41-0.60 looks as "Moderate"; 0.61-0.80 looks as "Substantial" and 0.81-1.00 looks as "Almost perfect". A receiver operating characteristic (ROC) curve was used for evaluation of cutoff value, sensitivity and specificity of PE to predict cardiac chamber dimensions measured by CE. A two-tailed p value <0.05 was considered significant.

Discussion

Previous reports showed that PE had greater advantages compared to CE and hand-carried echocardiographic device [9, 10, 11, 12, 13]. It may due to pocket size nature, good enough image quality and true frame of color flow imaging of PE. PE is suitable to study in the emergency and operation room, outside hospital consultation and ward rounds in anytime, especially in patient with critical ills. In this study, we evaluate the image quality, capability to answer clinical questions, the value of PE in evaluation of cardiac chamber enlargement, valvular heart disease and congenital heart disease, global and segmental cardiac function. PE could answer over 77.5% clinical configured questions and provide un configured cardiac findings at the first stop which could not answer by physical examination and may result in changes on clinical decision making and management. The value of PE to evaluate the major abnormalities was similar to the CE, included for evaluating the size of cardiac chamber, valvular heart disease, hypertrophic cardio myopathy and congenital heart disease. PE may become a new tool to modify the one-stop consultation model. We hope that the new one-stop consultation model in the future would be included interrogation, physical examination and PE. We successfully diagnosed 8 patients with critical ills by PE in emergency room. This first hand information at emergency room had great impacts in evaluation of patient prognosis, clinical decision making and acute management. PE could be used in follow-up for patients with decreased blood pressure after ablation of atrial fibrillation, Tran’s catheter ASD or VSD closure and coronary intervention to find possible complications after procedure. With its advantage of portable size and acceptable image quality, PE could meet the need for outside hospital consultation and provided practical suggestions. However, PE is not designed to replace CE. The 75° sector angle is narrower compared to current CE, and our PE user is clinical physician but not sonographer, who insufficiency of operator experience render physician overlook the tiny clue of structure abnormalities. The missing detected pericardial effusion and dilation of ascending aorta were mainly due to operator experience. In other reports, the physician experience felled far short [10]. As ASE guideline recommended that it is necessary for physician to undergo level II training in echo laboratory [5]. Limitation: We enrolled a large percentage of patients with left ventricular diastolic dysfunction or pulmonary hypertension because of consecutive patient nature. Therefore, clinical questions answered by PE were significantly less than CE. Finally, the suspected findings and unanswered clinical questions by PE still need CE and Transoesophageal echocardiography examination. Moreover, the detection of diastolic function, flow velocity, pulmonary systolic pressure is not available with PE range.

Conclusions

PE allows immediately detecting the intra cardiac structure and flow, had almost perfect performance in finding major and minor abnormalities associated with great concordance with CE. The pocket size echocardiographic device would like a stethoscope for cardiologist during consultation and determine release from the outpatient clinic which helps them to diagnose and manage critically ill patients at the bedside. Being ultra-portable and convenient, PE may become part of the clinical examination, performing like an excellent consultation tool. With pocket size nature and good agreement with CE, PE showed additive clinical value over the clinical physical examination. It may alter the current consultation mode in clinical practice in the future.

Disclosures

This article was supported by GE Healthcare, the Natural Science Foundation of China [Grant number 30800453 and 81270206], Shanghai Rising-Star Program [Grant number 10QA1404500], Natural Science Foundation of Shanghai [Grant number 12ZR1417600] and Shanghai Med-X program [Grant number YG2010MS29]. The author gratefully acknowledges the support of K. C. Wong Education Foundation.