Improved cardiovascular diagnostic accuracy by pocket size imaging device in non-cardiologic outpatients: the NaUSiCa (Naples Ultrasound Stethoscope in Cardiology) study

Abstract

Miniaturization has evolved in the creation of a pocket-size imaging device which can be utilized as an ultrasound stethoscope. This study assessed the additional diagnostic power of pocket size device by both experts operators and trainees in comparison with physical examination and its appropriateness of use in comparison with standard echo machine in a non-cardiologic population. Three hundred four consecutive non cardiologic outpatients underwent a sequential assessment including physical examination, pocket size imaging device and standard Doppler-echo exam. Pocket size device was used by both expert operators and trainees (who received specific training before the beginning of the study). All the operators were requested to give only visual, qualitative insights on specific issues. All standard Doppler-echo exams were performed by expert operators. One hundred two pocket size device exams were performed by experts and two hundred two by trainees. The time duration of the pocket size device exam was 304 ± 117 sec. Diagnosis of cardiac abnormalities was made in 38.2% of cases by physical examination and in 69.7% of cases by physical examination + pocket size device (additional diagnostic power = 31.5%, p < 0.0001). The overall K between pocket size device and standard Doppler-echo was 0.67 in the pooled population (0.84 by experts and 0.58 by trainees). K was suboptimal for trainees in the eyeball evaluation of ejection fraction, left atrial dilation and right ventricular dilation. Overall sensitivity was 91% and specificity 76%. Sensitivity and specificity were lower in trainees than in experts. In conclusion, pocket size device showed a relevant additional diagnostic value in comparison with physical examination. Sensitivity and specificity were good in experts and suboptimal in trainees. Specificity was particularly influenced by the level of experience. Training programs are needed for pocket size device users.

Figure 1

Prevalence of cardiac abnormalities not detectable by PE and diagnosed by PSID in the overall population.

Figure 2

Sample of abnormal findings detected by PSID in the study population. In the first line (from left to right): enlarged left ventricle with depressed EF, dilated right ventricle and dilated IVC which also presents reduced respiratory reactivity. In the second line: mitral regurgitation (double jet), pericardial effusion and pleural effusion.

Figure 3

Sensitivity and specificity (with 95% confidence intervals) of PSID in the overall population (left panel) and comparison of experts and trainees (right panel). Standard Doppler echo is the reference gold standard.

Figure 4

Proposal of a training program model for PSID users. A short period of 3 days basic teaching (ultrasound physics and biological effects, normal and pathologic cardiovascular anatomy, normal and pathologic blood flow dynamics) should be followed, after a free interval, by an in-hospital period (60 days, 3 days per week) for highly motivated operators (direct scan of standard echo views by PSID and visual assessment of at least 150 exams by PSID), in order to achieve the target level of competence.