Portable Ultrasound as the Stethoscope of the Future: Is It the Snapchat of Formal Echocardiography?

John Mandrola


November 18, 2013

Dr Eric Topol speaks often of the disruption that is coming in the practice of medicine. He calls it creative destruction, and he argues that mobile devices and the technology that run them will be the vehicle for transformation. It's hard for me—an IPhone ECG user and early adopter of social media—to doubt such a bold claim. Dare I say, though, outside of Southern California, the medical world is populated with disruption doubters?

An essay is supposed to persuade. So, let me tell you about some compelling evidence from the American Heart Association (AHA) 2013 Scientific Sessions that suggests Dr Topol is indeed on to something tangible and real.

In terms of usefulness, perhaps the most proximal of innovative devices is the handheld portable ultrasound machine. What once weighed hundreds of pounds can now be carried around like a stethoscope. What's more, sound waves do not hurt or emit radiation. Ultrasound is no CT scanner, nuclear study, or heart catheterization.

Yet major questions remain as to how a sound-wave–emitting stethoscope will improve patient care: Is it feasible? Does the evidence support its use? And the most acute question: how exactly will an ultrasound exam be incorporated into our relative value unit (RVU)–driven, bloated healthcare system?

Before I tell you about the AHA study, a first-person short story:

Years ago, I got into a pattern of doing a "quick" echocardiogram exam after an AF ablation. (There's a lot of that could have happened during those two hours.) When I first began this departure from my normal routine, an astute nurse, whose job it is to document all (and I mean all) the things we do, asked: "Dr Mandrola, are you doing an echocardiogram? I need to write that down."

"No, no, I am definitely not doing an echocardiogram . I am just taking a quick look at some basic things." It is true. When I do a "quick-look" echo after an AF ablation, I don't need to know derivatives and integrals of regurgitant jets, I just need to know the answers to a few simple yes/no questions.

Now let's get to the abstract; I'll come back to the story.

Dr Bruce Kimura and colleagues (Scripps Mercy Hospital, San Diego CA) studied whether a quick-look ultrasound exam can improve echo referrals and what the implications are for appropriate and competent ultrasound stethoscopes .

This group has published previously on the use of portable ultrasound devices, but yet few data exist on how to cost-effectively and competently apply such technology. The idea is that this point-of-care exam could be highly cost-effective if it diminished unnecessary cardiac testing.

Researchers used 233 consecutive outpatients' echo studies and assessed the utility of four embedded quick-look signs—called the CLUE protocol. The clinically relevant yes/no signs were: LV dysfunction, left atrial enlargement (LAE), pulmonary edema (+/- comets), and elevated central venous pressure (inferior vena cava [IVC] dilation +/-). The research team then performed an analysis of the additional cardiac testing vs percent missed abnormalities, each calculated for any combination of echo findings. This yielded an R-curve that was compared with other common validated diagnostic tests, like D-dimer and exercise treadmill testing (ETT).

Echo abnormalities were found in 39% of the 233 patients enrolled. The best-fit combination for the quick-look exam was LAE and IVC+, which yielded a sensitivity of 65% and specificity of 76%. Applying the quick-look strategy in this population would reduce echo referrals by 60%, but at a 13% risk of missing a true abnormality. The R-prediction-model curve looked similar to that of D-dimer test and ETT.

These results led the authors to conclude that the "cost, competency, and risk boundaries of ultrasound stethoscope use can be modeled as comparable to accepted clinical practice."

Four Take-Home Lessons:

I had a chance to talk with both lead author Dr Paul Han, and senior investigator Dr Kimura. Four themes emerged—at least in my mind:

One is that the portable ultrasound must not be thought of as a procedure, but rather as an extension of the physical exam. We don't make an mpeg recording of an S3 gallop; we hear one and write down our observation. We don't take a picture of the tympanic membrane; we look at it and note whether it is normal or not. It's the same with the ultrasound exam. We take a quick look—without a recording or procedure report. We interpret the image as we would an exam finding. Is this the Snapchat of formal echocardiography?

Second, the portable ultrasound exam changes the paradigm of how medical learners incorporate physical findings into medical decisions. My generation was taught the physiology of inspiratory crackles; it meant there was pulmonary edema, usually due to pulmonary venous congestion. The current generation will be able to see the congestion through their ultrasound stethoscope. That's different. Better. The physical exam will still be important—for patient-doctor rapport if nothing else—but there's little argument that the art of the exam is being lost. (Just like the art of ECG interpretation.)

Third, it's okay that the portable ultrasound isn't as sensitive or specific as formal echocardiography. It's not supposed to be. Data such as those presented today tell us that (at least in the intermediate term) the stethoscope of the future will be as good as an exercise test or D-dimer. That's pretty darn good for an exam that can be done painlessly without radiation in mere minutes. A word comes to mind: Efficiency is defined as achieving maximum productivity with minimum wasted effort or expense or by preventing the wasteful use of a particular resource. It seems to me this innovation fulfills that definition perfectly.

The final thing that struck me about this disruptive technology is that its success of turns on the precept of less is more. Here the KISS principle reigns supreme. Attempts to teach learners too many tricks undermine the chances for success.

Let's go back to my postablation quick-look study. I am interested in simple binary questions: Is there a pericardial effusion, and if yes, is it big or small? Is the LV function normal, or is it impaired enough for me to give diuretics postprocedure? These are simple questions that an extension of the physical exam can accomplish more efficiently than a four-page formal echo report.

As a clinician, everything about this innovation excites me. Yes, the technology is nifty, the cost-effectiveness useful, but the best part is this: if we try to make portable ultrasound do too much, it fails.

That success demands simplicity is beautiful.



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